© Copyright by Shrihari Sridhar 2013 · 3.7.2. Water Stagnation in Pipes and Tanks..... 35 . v...
Transcript of © Copyright by Shrihari Sridhar 2013 · 3.7.2. Water Stagnation in Pipes and Tanks..... 35 . v...
INTERMITTENT WATER SUPPLIES: WHERE AND WHY
THEY ARE CURRENTLY USED AND WHY THEIR FUTURE
USE SHOULD BE CURTAILED
By:
Shrihari Sridhar
A thesis submitted in conformity with the requirement for the Degree of
Master of Applied Science Graduate Department of Civil Engineering
University of Toronto
© Copyright by Shrihari Sridhar 2013
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Abstract
INTERMITTENT WATER SUPPLY: ORIGIN, CONSEQUENCES
AND SOLUTION
By
Shrihari Sridhar
Department of Civil Engineering
University of Toronto
2013
Though water is the most essential element of life in most developing countries clean
drinking water is supplied intermittently to consumers. Municipalities are often under the
impression that intermittent supply is an ideal measure to conserve water. With over a billion
people grappling with deteriorating infrastructure and water scarcity, it is impossible to
neglect the effects of intermittent supply. It is essential to examine the origin of the problem,
quantify the effects or consequences and then provide feasible solutions.
Hence, this thesis provides a comprehensive review of the existing condition of water supply
systems in developing countries but more importantly, examines the causes of the
intermittency and highlights the significant economic incentive that could be achieved by
maintaining a continuous supply system. Finally the thesis concludes with a series of feasible
solutions including short-term and long-term plans that would assist in a complete migration
towards 24-hour supply.
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Acknowledgement
It is a pleasure to thank the many people who made this thesis possible.
I would like to express my deepest gratitude to my supervisor, Dr. Bryan Karney for his
continued support, devotion, patience, consistent guidance and for instilling in me the ability
to motivate myself to achieve results.
My thanks also go to Dr. Jennifer Drake for her helpful comments as a second reader. My
sincere thanks to those who showed interest in my work and gave me some valuable inputs,
especially my colleague Mr. Ahmad Malekpour.
I would like to thank my parents for their financial support and consistent encouragement
without which I would not have been able to continue with my graduate studies.
Finally and most importantly, I thank God for granting me the wisdom, knowledge, sound
mind, good health and for supplying all my needs to produce this work.
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Contents
Abstract
Acknowledgement
List of Figures
List of Tables
1. Introduction
1.1. Importance of this Study........................................ 04
1.2. Objectives....................................................... 05
1.3. Organization.................................................... 06
2. Problems Resulting in an Intermittent Supply
2.1. Water Scarcity Issues............................................ 09
2.2. Economic Restrictions and reducing hydraulic capacity........ 11
2.3. Improper Resource Management................................ 13
2.4. Summary......................................................... 14
3. Consequences of an Intermittent Water Supply System
3.1. Improper Water Distribution and Pressure management........ 15
3.2. Coping Costs.................................................... 17
3.3. Overexploitation of Groundwater............................... 20
3.4. Unhealthy Practices and Water Losses.......................... 21
3.5. Constraints to meet fire flow needs with the present system.... 22
3.6. Increasing Costs and Rising Energy requirements............... 22
3.6.1. Ageing Infrastructure and High Energy Costs............ 22
3.6.2. Pipe Breakage (Line Filling).............................. 27
3.6.3. Air Entrainment .......................................... 29
3.7. Water Contamination............................................ 31
3.7.1. Water stagnation in pipes and private tanks.............. 31
3.7.2. Water Stagnation in Pipes and Tanks....................... 35
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3.7.3. Privatization............................................... 37
3.7.4. Summary.................................................. 38
4. Detailed analysis of the possible solutions
4.1. Immediate steps to move towards a continuous supply......... 40
4.1.1. Water conservation........................................ 40
4.1.2. Water Demand Management.............................. 41
4.2. Pressure Management and Leakage Control..................... 43
4.3. Improved Metering and Billing Procedures..................... 45
4.4. Model Resource Management Strategies and Long Term Plans. 47
4.5. Model Strategies................................................ 51
4.6. Summary........................................................ 52
5. Case Study of Bangalore and Mumbai
5.1. Comparative Energy and Cost Analysis of Continuous and Intermittent Supply
Systems – Mumbai, Case Study.................................. 53
5.1.1. System Parameters and Projected Demand................ 56
5.1.2. Consequences of Pipe ageing on Transmission (Pumping) Energy loss 58
5.1.3. Analysis of the Results..................................... 68
5.2. Sample Study-Bangalore, India................................... 74
5.3. Summary.......................................................... 76
6. Conclusion and Future research opportunities..................... 78
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List of Figures
3.2.1. Estimated Cost Comparison.................................... 18
3.6.1. Water Distribution Energy use Comparison..................... 23
3.6.2. Pipe Wall Corrosion........................................... 25
5.1. Mumbai Water Distribution Plan................................. 54
5.2. Water Conveyance (Pumping) Cost Comparison.................. 68
5.3. Percentage Loss in revenues..................................... 69
5.4. Pipe Repair Cost Comparison.................................... 71
5.5. Estimated Cost Saving........................................... 72
5.6. Pipe Repair Energy Consumption Comparison.................... 73
5.7. Ratio of Energy Use (IS:CS) .................................... 73
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List of Tables
3.7.1. Peak factor Comparison between Intermittent and Continuous Supply Systems. 33
4.1. Monthly Water Consumption Block Rates....................... 46
5.1. Water Supply and Demand Projection........................... 58
5.2. Per-capita Water Consumption distribution...................... 75
1
CHAPTER 1
Introduction
Water for human and urban use is often transported from source to domestic and industrial
users through a network of pipes of various diameters. Drinking water is collected from one
or more natural source water resource such as a lake, river or aquifer and is conveyed to a
treatment facility. Additional facilities such as pumping stations and storage reservoirs are
required to reliably pressurize the water through a pipe network until the water finally
reaches the consumer. A complex system such as this is in place to supply clean drinking
water to the consumers continuously throughout the day. However in some developing
countries, the consumers will have access to drinking water for less than 24 hours or even
from a few hours to few minutes a day. This thesis examines the consequences of resorting
to intermittent water distribution systems in developing countries with a focus on its impacts
on the distribution system and how the society responds and copes with a rationed service.
The work in this thesis is in part summarized in a paper “A Selective Literature of
Intermittent Water Supply: Problems and Solutions”, which is under review in the Journal of
Water, Sanitation and Hygiene for Development.
A water supply is said to be intermittent when the water to an area is regularly/irregularly
provided through piped networks for less than 24 hours a day. Though basic issues related to
water scarcity and intermittent supply are not part of popular consciousness in developed
countries, their effect is truly global as this issue affects over a billion people worldwide.
Intermittent water supply systems are found mainly in newly developing countries.
including most of the countries of South Asia and Latin America (Vairavamoorthy, 2007).
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South Asia is estimated to supply water to at least 350 million people for as little as a few
hours a day, and nearly all water supply systems in Indian cities are intermittent. In Latin
America alone, more than 50 million inhabitants in 10 of its major cities receive rationed
water supply (Vairavamoorthy, 2007). No city in India has a continuous water supply (WSP,
2009) and even in major cities of India, water supply is as low as 1 hour a day or less and 2-3
hours of supply is considered to be good. Currently, some 30 countries are considered to be
water stressed. It is predicted that by 2050, the number of water scarce countries will likely
approach 35 (Vairavamoorthy, 2007). Jordan, for example, has a severe water shortage
problem. The drinking water available per capita is less than 100 lpcd (litre/capita/day)
(Vairavamoorthy, 2007).
Urban population growth is among the most central concerns to meeting future water needs,
particularly in developing countries. One third of the 9 million residents in western Manila,
Philippines are not connected to the municipal water system, and over 1 million suffer from
intermittent supply or very low system pressures (Miya, Manila project, 2007). With overall
consumption constantly increasing from limited sources, water boards felt they have little
option but to supply water intermittently. Water demand is increasing at three times the rate
of the world’s population growth, and officials at the 3rd World Water Forum noted that
poverty alleviation is the single most important factor related to meeting that demand
(Environment News Service, 2003). According to official figures from the Water Forum,
around 1.2 billion people lack safe water supply and 2.4 billion live without secure sanitation
(Environment News Service, 2003). India’s population grows by over 1% per year and with
this acute population increase, water scarcity becomes obvious. In Kathmandu, Nepal 5,000
new connections are provided each year despite an inadequate distribution system (McIntosh,
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2003). According to Western Jakarta water services, 210,000 water connections were added
in the 11 years between 1998 and 2009 (PPP Jakarta water, 2007). The scale of the human,
technical, economic and hydrological problems is immense.
As Vairavamoorthy (2007) shows, the relative increase of water consumption in developing
countries further highlights the need for creative solutions to water scarcity. From 1995 to
2005, water consumption was expected to double in developing countries, with water
demand projected to be essentially flat in developed countries (Vairavamoorthy, 2007). If the
demand drastically increases, a complete system overhaul will be necessary: increased
hydraulic capacity will require more high power equipment to be installed, new water
sources to be found and tapped, and all related infrastructure improved. All such factors
require substantial capital, which in most cases developing countries cannot afford to invest,
and thus intermittent supplies are adopted as a relatively inexpensive water conservation
technique and seemingly safe option. Table 1.1 summarises briefly the advantages and
disadvantages of intermittent flow.
Perceived advantages of Intermittent Water Supply:
A convenient Water saving technique
A good conservation technique for a short term as it doesn’t need any additional
infrastructure.
Disadvantages of Intermittent Water Supply:
Insufficient pressure at the consumers end,
Higher possibility of contamination
Additional costs (coping costs) incurred by the consumers
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Inequitable Distribution of water
Unhealthy practices that lead to unnecessary wastage.
Increase in leakages which in turn worsens the system
Major disadvantage during Fire accidents
Metering problems
More frequent water hammer issues
Increasing exploitation of Ground water will cause environmental problems in the
long run.
1.1. Importance of Current Study
This study makes an important contribution towards relating causes and effects of
intermittent water supply. The effects have however been discussed in the past through
various reports and studies as it manifests itself as hindrances to our everyday life. For
instance, contamination of drinking water, deteriorating water quality and transient pressure
conditions might manifest in the form of a disease outbreak or a watermain break. Though
plethora of evidence was found in the literature reviewed that indirectly pointed towards
intermittent supply as the prime cause of such effects, hardly any attempt was made in other
works to knit all the causes and effects together to present a complete picture of state of
water supply in most parts of the developing world. Simply identifying the origin of a
problem does not provide enough motivation to find an optimum solution unless the
magnitude of its consequences is well documented and quantified. The same has been the
case with intermittent supply. For instance, Totsuka et. al. (2004) analyze the origin of
intermittent supply and express the need to migrate towards a 24-hour supply but finally end
up justifying the need to implement a new set of design guideline to operate distribution
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systems intermittently. However their objectives are partly justified as the existing
intermittent systems are designed to be operated continuously because no guidelines were
available specifically for the design of intermittent systems. This approach of dealing with
intermittent supply is understandable as there are insufficient studies that report the
magnitude of the consequences. For instance, results of a study reported by Charalambous
(2011) were the only information available in the literature reviewed that made a connection
between intermittent supply and the resulting pipe breaks. Similarly, few studies were found
in the literature reviewed that compared the rate of corrosion in an intermittent and 24-hour
supply system. The closest available resource in the literature is the statement, “It is
generally believed that, pipes in an intermittent supply system tend to corrode faster than
pipes in a continuous pressurised system as pipes are alternatively exposed to air and water”,
available in the Sustainable Sanitation and Water Management website (SSWM). As the rate
of corrosion would affect the friction head-loss and ultimately the energy involved in
transmission, a study representing this connection is an important contribution towards
decision making.
Hence this work not only bridges the causes and effects of intermittent supply, but provides
enough evidences to prove that a complete migration towards a 24-hour supply is not only
humanly justified and urgent, but would bring great benefit to infrastructure performance and
longevity.
1.2. Objectives and Organization of this Study
Being one of the foremost issues faced by the developing world intermittent supply needs
utmost attention and careful analysis before any action is taken. India is used as a typical
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developing country to discuss the real-world implications of intermittent supply. Hence the
objectives of the thesis are several:
1) To identify the factors that contribute to the intermittency in supply,
2) To identify the direct and indirect consequences of Intermittent Water Supply (IS),
3) To quantify the effects of intermittent supply,
4) To perform a comparative study of intermittent and continuous water supply (CS)
systems to assess the possible advantages of a complete migration; and
5) To identify feasible methods and strategies for a complete migration under all
conditions of intermittency.
1.3. Organisation
The structure of the thesis is as follows. The origin of intermittent water supply is discussed
in Chapter 2. As the cause intermittency in supply varies, the origin of the problems have
been categorised and each category is analysed and supported with examples from specific
regions in India.
The consequences of resorting to an intermittent supply system are thoroughly presented in
Chapter 3. A comparative energy and cost analysis between a continuous and an intermittent
supply system is performed and results presented typically measure the net advantage of a
complete migration to a 24-hour supply system. As it is one of the first studies of its kind
various available models and reports were reviewed and compared. Results are presented
through two types of indicators: embodied energy and cost.
Chapter 4 presents some feasible solutions in the form of short-term measure and long-term
strategies that would aid a successful migration to a 24-hour supply. Importance is given to
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demand side management and water conservation. As water scarcity situation is not new,
some measures that have either been implemented or proposed in the past are presented with
the idea of identifying a possibility to modify them to suit an Indian (or South-East Asian)
scenario. Further the advantages of using reclaimed wastewater are presented with a focus on
net energy benefit. Chapter 5 concludes the thesis by suggesting future avenues of research
based on the results presented in the thesis that could contribute to reliable and sustainable
24-hour water supply for the growing population in the developing world.
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CHAPTER 2
Origin of Intermittent Supply
The first step in solving a problem is recognising one exists. This chapter hence presents all
crucial factors that lead to, or are said to justify, intermittent supply. Through an extensive
literature review, field surveys and information retrieved from various sources including
personal experiences, discussions and local media, the chapter collects and summarizes a
state-of-the-art understanding of intermittent flow. The common understanding on the reason
behind the intermittency is that the amount of water available is insufficient to meet the
consumer demands. But a little more attention would reveal that intermittency persists even
in places which have abundant fresh water resource. For instance, even though the Indo-
Gangetic plains, home to a billion people in the Indian subcontinent (which covers the
Ganges-Brahmaputra region of Eastern India and Bangladesh) have perennial water source
(in abundance) no city in the region enjoys a continuous water supply. Such realities prove
that apart from absolute water scarcity there are other factors which are either individually or
collectively responsible for the intermittency. The other question is also relevant: to what
extent do intermittent supplies reduce the overall demand for water? Consumers hoarding
large amount of water and discarding them during the next flush simply results in excessive
consumption which contradicts the general belief that intermittent supply reduces overall
water consumption. Hence in the present study the origin has been divided into three main
categories and with the help of real situation in different cities in India, the problems have
been thoroughly examined.
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2.1. Water Scarcity
Lack of access to a continuous source of clean water is a central problem in a developing
country. Though South-East Asian countries and the Indian sub-continent communities are
blessed with water resources, but are experiencing steeply increasing population and heavy
migration from rural to urban areas. These rapidly shifting urban demographics are creating
the potential for acute local, regional or even national water crisis. Conflicts between
households and neighboring communities to secure water are a common sight even in urban
India. There is a frenzied scramble among thirsty crowds to secure water from (water) trucks
(Krishnan, 2013). Regional water dispute between states is strongly affecting the country’s
agricultural and industrial production leave alone the increasing suicide rates among the
agricultural communities! For instance more than 2,200 farmers in India committed suicide
in the past four years, as water loss and drought drove them deeper into debt (Katakey, et.al,
2013).
The city of Chennai stands as a perfect example of a place grappling with water scarcity. As
against the demand of 1009 MLD, the supply only about 766 MLD with only a part of it
supplied through piped networks (Srivathsan, 2013). A portion of the supply takes place
through water tankers. Over 13,000 tankers that operate in the city mine water from the
surrounding farmlands and the tanker industry is said to be worth over $100 Million
(Srinivasan, 2005). Thus, the acute water shortage is met by removing water from the
neighboring rural areas. The scarcity is mainly due to the two seasonal rivers (Cauvery and
Krishna) which are the primary water sources. However as the neighboring provinces depend
on these rivers as well, Chennai is put in an unsure situation.
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A similar situation exists in the Indian capital, New Delhi. The city has a demand of around
4200 MLD but is able to supply only around 3150 MLD (Kaur, 2012). Though a large part of
this demand is not met through piped water supply. Around 2 million people in the Indian
capital of New Delhi alone siphon their water from water trucks, then hauling it back to their
shacks where they live with their families (Fishman, 2011).
Bangalore is one of the largest cities in India with a population of over 8.5 million. With a
per-capita consumption of 150 l/day, the city needs 1425 ML of water every day out of
which the industrial consumption is around 50 MLD (TOI, 2013). The City draws 532,000
ML/year of water from Cauvery river, which gets exhausted (or level in the reservoir drops
below the minimum level) with the supply of 1,425 MLD (TOI, 2013). But even with such
efforts the Water Board (BWSSB) is barely able to supply water 2-3 times a week. This is
mainly because around 450 MLD (or 30%) of the pumped water is lost through leaky pipes
(TOI, 2013). In another six to seven years per-capita availability of water in Bangalore may
be as little as 73 lpcd which is less than what is prescribed by the World Health Organisation
(100 lpcd) (TOI, 2013). There are claims that if the scarcity is not addressed soon, by 2023
half the city will have to be evacuated (Sudhir, 2013). Even the Bureau of Indian Standards
(1993) prescribes the per-capita water requirement in a city like Bangalore should range from
150-200 lpcd.
Hence one of the main reasons of intermittency is absolute water scarcity. Rapid urbanisation
is also partly responsible for the scarcity and a primary concern in developing world cities is
the unprecedented population increase, a direct result of rural migration. Between 1950 and
1990 the number of world cities with a population greater than 1 million increased from 78 to
290 and is expected to rise to 600 by 2025 (Vairavamoorthy, 2007). This is hence a clear
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indication that if the number of cities (and thus the urban population) increases there will
likely be more water scarcity in the future.
2.2. Economic Restrictions and reducing hydraulic capacity
Lack of sufficient financial resources is another of the important factors that contributes to
the intermittency. Finances of the water boards are plummeting and the revenues are
insufficient to meet even the basic expenditures (Mathur and Thakur, 2003). Many
municipalities seem unperturbed about unmetered connections either because it is one of the
crude measures to help the poor or the existing system does not assist in maintaining metered
connections. Also in most Indian cities as the price of water is so low (presently around Rs.
6/KL or $0.1/KL) (Mathur and Thakur, 2003) and penalties for unmetered connections are
not harsh, it is just not feasible to meter the connections. City specific studies of Bangalore,
Chennai and Hyderabad show that the typical price charged for water for residential use is
about Rs. 1.5 ($0.02) per cubic meter which is one tenth of the operating and maintenance
costs (Mathur, 2003). Also, for instance in Gurgaon, until March 2012, over 11000
connections were unmetered. Though municipal authorities issued notification regarding
installation of meters, over 9500 connections remained unmetered till August 2013 (Saini,
2013)
Ray (2009) and Mathur (2001) reported that in India there is a great disparity in metering.
Consumers with metered connections range from as low as 5% in Chennai, 70% in Mumbai,
to 100% in Bangalore. Also a quarter of all connections in Delhi are metered but one-third of
them were no longer working (Ray, 2009). According to Mathur (2001), in Mumbai, 73% of
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the connections are metered of which 81% of the meters were reported to be non-functional
in 2000.
Currently to avoid the pain of metering and compensate for the unmetered connections a flat
rate is maintained for households. For instance in the Indian city of Gurgaon, Rs. 48/month
($0.8 USD) is charged for an unmetered connection (Saini, 2013). If put into perspective, a 4
member household consuming 18,600 L/month (according to 155 LPCD minimum
consumption) would be paying $0.8 every month (Saini, 2013). Currently even metered
connections are poor as the rates are extremely low. In Gurgaon, households with metered
connections pay Re.1.25/KL (around $0.017/KL) (Saini, 2010) which means consuming
186,00 L/month would cost Rs. 23.25 (around $0.38/month)! For instance if the household
income is $12000/annum (or $1000/month) water price would be 0.038% of the household
income!
Increases in power tariffs, higher costs of labour and material and constantly rising loan
interest rates are crippling the water boards, pushing them towards huge revenue deficits. For
instance, in the case of Bangalore Water Supply and Sewage Board (BWSSB), since the last
revised tariff, expenditures on power has gone up by 46%, the cost of establishment has
increased to 144% and the interest paid by the board on loans has increased by more than
400% (Madhusudhan, 2013). According to the Chairman of BWSSB water tariffs in
Bangalore have not been revised since 2001 (Senthalir, 2011). BWSSB’s deficit in 2008-09
stood at $27 million USD and between 2008-09 and 2011-12 the board lost around $40
million USD as a direct result of not increasing the water tariff (Madhusudhan, 2013).
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The economic problems facing Indian water boards are not just with the unrevised tariffs. In
a reading being recorded through bulk flow meters in Bangalore, for a monthly supply of
28,888 ML only 15,465 ML was billed meaning the revenue collected is only for 54% of the
supplied water (NUWA, 2012). A similar situation exists in India’s financial capital,
Mumbai. The City’s municipal corporation has realised that currently 360,000 connections
are metered but 100,000 more connections still need to be metered (Baliga, 2012).Hence
higher proportion of unmetered connections and unrevised tariffs pose significant economic
constraints to achieve a better water supply.
2.3. Improper Resource Management
Water scarcity may be experienced if the boards do not execute responsible stewardship of
the available water resources. In high density (population) regions water boards should
endeavor to sustainably tap every single fresh water source. For instance, in Bangalore 300
MLD of groundwater is drawn through private borewells (Nataraj, 2013). Hence the city
does have 300 MLD fresh water source but it is not been put into (equitable) distribution.
Given that India does not regulate water usage, it should come as no surprise that there is
also little regulation on pollution and even less enforcement of what regulations do exist
(Brooks, 2007). A combination of sewage disposal, industrial effluents and chemicals from
farm runoffs, arsenic and fluoride has rendered India’s rivers unfit for drinking (Brooks,
2007). Only half of New Delhi’s 3.66 million cubic meters of sewage is treated and the rest
is released into River Yamuna (Brooks, 2007). The city cannot process the sewage it
produces as 45% of the population is not connected to the sewage system. Those not
connected to sewage lines end up dumping their waste into canals, which empty into a storm
drain that runs into the Yamuna River (Brooks, 2007). Bangalore is in a similar situation too.
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According to Central Ground Water Board (CGWB) official, the practice of disposing
improper garbage and solid waste into the city’s groundwater source is the main reason for
the pollution (IWR, 2011).
2.4. Summary
Through different cases and examples of Indian cities the chapter highlights various factors
that typically lead to intermittent supply. Absolute scarcity is definitely a key factor that
influences the intermittency. But the fact that even places with abundant source of fresh
water face intermittent supply argues against the myth that such a system is a remedial
measure to overcome water scarcity alone. Hence the chapter stresses on other factors such
as which induce a state of “virtual” scarcity often caused by deteriorating infrastructure and
improper resource management which in turn forces the system to be operated intermittently.
The chapter also attempts to imply that either due to lack of knowledge or negligence,
municipalities seem to look for new sources hundreds of kilometers away but are not
interested to take the initiative required to fix leaky pipes and revenue loss is not caused only
through leaky pipes but also through poor metering and billing policies. The focus of this
thesis is to examine all significant causes and effects of intermittent supply; this Chapter 2
provides a broad platform on which the consequences of intermittent flow can be quantified
and to provide suitable recommendations about such an evaluation.
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CHAPTER 3
Consequences of Intermittent Water Supply
Once the origin of a problem is established it is necessary to examine and quantify the
consequences of the current situation as a key step toward taking appropriate action. In the
case of intermittent supply, the consequences are all the more important as it is affecting over
a billion people around the world. This chapter highlights the direct and indirect effects of
intermittent supply on the individual consumers, the community as a whole, the distribution
infrastructure and the economy. To aid decision making in the future, the consequences have
been quantified in terms of energy use and capital loss. The chapter has linked various
factors contributing to system deterioration and the phenomena behind the role of supply
intermittency have been well explained.
3.1. Improper Water Distribution and Pressure management
Maintaining a minimum residual pressure is equally important as providing enough water to
consumers to fulfill their diurnal demand. But it is even more important to do this for an
intermittent supply. As the consumers are unsure about getting the next flush in the recent
future they have a tendency to collect as much water as possible in a short duration of time or
till the supply lasts. As the consumption or the quantity collected is directly dependent on the
pressure available at the outlet, consumers closer to the pumping station and low-lying areas
have a great advantage. As there are no guidelines made specifically for intermittent supply,
distribution systems are designed for a continuous supply based on the assumption that the
demand would be spread over 24 hours. In reality, water is drawn in a shorter duration. This
implies that the system capacity can become undersized because flows in pipes are much
greater than anticipated resulting in severe pressure losses. Hence, there is generally a low-
16
pressure regime in the network (Anand, 2002). According to Central Public Health
Environmental Engineering Organization’s Indian Government Guidelines (CPHEEO,
1999), a distribution system should supply a minimum residual pressure of 7 m (of water)
(10 psi) for single storied houses, 12 m (17 psi) for two-storied houses and 17 m (24 psi) for
three storied units. Studies conducted by Nelson (2012) show that the residual pressures at
many points in the city mains ranged between 1.5 Psi to 3 Psi (in the Southern Indian city of
Hubli-Dharwad). According to Environmental Health Project a study conducted in Dehra-
Dun revealed that the available residual pressure at the consumers’ end varied greatly
between seasons (Choe, 1996). As it is a normal practice for households to collect and store
water in clean containers as and when possible, they experienced lower pressures during
summer (dry) season. On average it took 3 minutes to fill a bucket (15 liters) of water during
regular seasons and 7 minutes during the dry season (Choe, 1996). This translates to a drop
in discharge rate from 0.083 l/s during regular seasons to 0.035 l/s during dry seasons.
Considering a basic requirement of 150 lpcd, a household with piped connection would need
to spend 2 hours during regular seasons and over 4 hours during dry season to store water.
Also in Dehra-Dun, just 50% of the residents own a private tap, 30% share the water
connection with their tenants (28%) or with their neighbors (2%) and 18% rely on public taps
(Choe, 1996).
Consumers around the country are upset with the rationing as well as unequal distribution,
especially as the cost of water is almost same for all. Recently the residents New Delhi
protested against the erratic and unequal distribution of water by the Delhi Jal Board (DJB)
across the capital city. The agitating residents strongly believe that the brunt of this unequal
distribution of water is borne by the city’s poor who reside in colonies which are supplied
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water not through pipelines but through tankers (Kumar, 2012). In the South-Indian city of
Bangalore where water is supplied for duration of 3-4 hours once every three days, similar
problems persist. Consumers who are lucky to have private bore-wells at home enjoy a 24/7
supply while other residents who have limited access to clean drinking water try to manage
with what have stored till the supply resumes. For high-rise apartments or condominium
units the problems vary. Not only do they have to cope with the unequal distribution from
the rest in the city but inequality also exists between the individual units within the building.
The general practice in such high-rise buildings is to store water in overhead tanks form
where it is distributed to the residents. In such a system customers (nodes) at higher
elevations receive water at a lower pressure compared to those at lower elevation, thus
introducing a sense of “water competition” is introduced among consumers.
3.2. Coping Costs
India, today is a fast growing economy with a steady GDP growth rate of 6.3% (ET, 2012).
With increasing per capita income consumers no longer want to settle for a rationed water
supply. Over the years they have started to adopt various measures to overcome the
intermittency but at a cost which is generally called a “Coping Cost”. A considerable coping
cost is incurred to store back-up water during non-supply hours, which is practically the
whole day in many places. Moreover, most rural consumers rely on public water taps, and
thus end up standing in long queues wasting potentially productive time (Global Water
Intelligence, 2009). In Manila those not connected to a 24-hour piped water supply (mostly
the poor) pay around $20 per month for 6 cubic meters of clean water while others with
continuous supply (mostly the rich) pay around $4 per month for 30 cubic meters of clean
water (McIntosh, 2003). The following estimated cost comparison in Figure 3.2.1 shows
18
similar results in India where households with highly unreliable supply (mostly the poor)
incur costs around $27 per month for a mere consumption of 40 lpcd (source of data; The
Hindu, 2012; expressindia, 2009; The Hindu, 2010; TOI, 2011; Chennai Metro Water; EPA,
2004; EPA, 2008)
Fig: 3.2.1 – Cost estimation for various types of supply. The data has been procured for the
estimation from various sources
The estimated “cost” incurred by a consumer in rural areas of India is high compared to an
average consumer, say, in Canada (fig. 3.2.1); these differences are even greater if income
differences are considered. Though water in rural areas is supplied “for free,” consumers
have to travel to tankers and wait in a relatively long queue. With 2 million people in New
Delhi alone and millions others in rural India where 70 percent of the country’s people live
(Fishman, 2011), intermittent supply alone is affecting the economy considerable. In India 32
million households collect water from places over one kilometer away from their homes and
0
5
10
15
20
25
30
Continuous Supply Ground water + Municipal supply
Alt. Source + Municipal Supply
Municipal Supply Supply in Rural areas (India)
Estimated Cost Comparison
Co
st (
USD
)/ca
pit
a/ m
on
th
Type of cost
19
about 170 million people every day who consume water that has been carried home by foot
(Fishman, 2011). The figure depicts what that particular consumer would have earned if
he/she had worked on hourly wages instead of collecting water, an estimate made by
assuming an hour per day is required to collect 15 litres of water. Another coping cost in
developing countries like India is the tapping of subsurface water by consumers through bore
wells to overcome the problems faced due to intermittent supply. Consumers incur costs to
maintain and manage a groundwater supply system within their homes not to mention the
constant worries about the working of submersible pumps when the yield is lower than
expected or when the water quality is not upto drinking standards.
Consumer willingness to pay is crucial, as urban consumers are willing to pay more for better
and reliable service. At Dehra Dun, the total revenue received by the water works department
in 1994 including non-household revenue was approximately Rs.30 million, with the average
pricing of Rs.2/m3. However, studies have shown that with an increase of pricing to Rs.2-
2.5/m3, which consumers were willing to pay for a continuous water supply, the revenue
generated would have been Rs.46 million (Choe, 1996). Hence the water supply issues both
worsen and are worsened by the financial problems. Raghupati and Foster (2002) found that
on average in India a five member family with a per capita monthly budget of Rs.350 would
pay up to Rs.6 per KL (Kiloliter, or cubic meter) for a block up to 10 KL per month. Given
that estimates of operation and maintenance costs in the range of Rs.15 per KL, subsidies are
thus provided by the water board. It is estimated that the federal government of India spends
US$1.1 billion (0.5% of India’s GDP) to subsidize the water supply, but 70-80% of this does
not reach the poor (Ray, 2009).
20
3.3. Overexploitation of Ground Water
Groundwater supplies 80 percent of water for domestic use in rural areas and almost 50
percent of water for urban and industrial uses (DFID, 2005). Presently as there are few
government regulations in India for domestic groundwater usage which has resulted in
widespread overexploitation of groundwater resources. Industries further contribute to the
overexploitation. For instance a Coca-Cola plant in Kerala (an Indian province) faced a
lawsuit and eventual closure in March 2004, as it was drawing so much subsurface water that
the groundwater table was being depleted (The Hindu, Business Line, 2004).
Overexploitation of groundwater, especially in Bangalore and groundwater contamination
are posing serious health risks. There are around 312,000 borewells in Bangalore from where
300 MLD of water is drawn for domestic use. The withdrawal rate is 3.7 times the rate of
recharge which is the reason why the borewells have gone to depths of 1000 ft (300 m) and
beyond (Nataraj, 2013). Once the households install borewells, they are free to draw as much
water as desired as their consumption is not metered. Only cost they would incur for
consuming groundwater is mainly for power and general maintenance. With the current
domestic rates of Rs. 36/KL and 300 MLD of unmetered groundwater consumption, the
municipality is falling short of an annual revenue of $71 M (assuming $1USD = Rs. 55).
Hence household with access to groundwater consume over 300 LPCD whereas large
sections of the community live on less than 100 LPCD. Reportedly many borewells in the
city are already going dry, meaning the residents have to dig deeper as the groundwater
levels are depleting (Deepthi, 2013). Rapid urban development has added to the woes. With
built-up area in Bangalore amounting to nearly 560 sq. km., just 240 sq. km. of open spaces
are available for groundwater recharge (Deepthi, 2013). This explains why, though the City
21
receives a rainfall of 830 mm just a miniscule 2% seeps into the ground (Deepthi, 2013).
With the current consumption rates it is feared that the groundwater source may be exhausted
by 2018 (Sudhir, 2013) which will leave over a million residents without sufficient potable
water. Unprecedented increase in the number of borewells has lead to other major concerns
in Bangalore. Geologists have warned against the increase in number of bore wells, which is
claimed to be a major cause of earthquakes (NIDM, 2007). Apart from the existing
uncontrolled consumption and disparity in resource allocation concerns are raising over the
quality of groundwater, which is further discussed Chapter 3.7.3.
3.4. Unhealthy Practices and Water Losses
Due to the uncertain timing of water delivery in an intermittent supply, people tend to collect
as much water as they can in the supply duration, but often dump the stored water when they
get their next newer and “fresher” installment. Water hoarding is a common practice in every
Indian home, be it in the form of tanks or a series of smaller containers. Consumers do not
actually keep track of the amount of water collected as their only aim is to collect as much as
possible in the supply hours. The main purpose of an intermittent supply is to reduce
consumption and leakage, but this practice can cause people to consume and waste more
water than they normally would in a 24-hour supply.
Studies have shown that real leakage represents 25-40% of water produced by utilities in
urban areas of India (Ray, 2009). In Zambia, on average 50% of the water produced by the
commercial utilities were unaccounted-for in 2006, providing revenue for only half the water
produced (Hulya, 2008). Leakages can happen due to extreme surge in pressures or too much
variation in temperature, from which cracks are caused (South African Government Online,
Draft-15, 2000), particularly in deteriorated lines.
22
3.5. Constraints to meet fire flow needs with the present system
Major constraints are experienced while meeting fire flow needs during intermittent supply.
According to Bureau of Indian Standards (1990), for every 50,000 population, water for
firefighting needs should be provided at a scale of 1800 L/min up to a population of 300,000
and for every 100,000 hence, an addition 1800 L/min should be provided for a duration of 2
hours. This would mean for instance in the major cities with a population of over 5,000,000,
95,400 L/min of supply must be available for a period of 2 hours or 11 million L per day.
With the supply duration ranging from a several minutes to few hours a day, the supply
would be able to meet fire flow needs only if the fires occur in specific regions during the
supply duration. Further, with a great disparity in residual pressures at the consumers’ end,
the probability of fighting fires is further reduced during intermittent supply. In the year
2005-06 the total fire losses paid by just four insurance companies in India was over USD $2
billion ( ). The accidental death statistics provided by National Crime Research
Bureau, India reveals that about 19000 people per year lost their lives due to fire during the
years 2003 & 2004 ( ).
3.6. Increasing Costs and Rising Energy requirements
3.6.1. Pressure losses and corrosion processes
Water distribution systems need continuous pumping to lift water from the source to an
adequate elevation to provide the required residual pressure at the consumers’ end but pumps
also need to overcome the frictional losses in the system. The lift requirement alone is termed
as static head and the lift with the frictional losses together is termed as the dynamic head
which should be supplied by the pump. The basic idea of static and dynamic head and higher
energy required to pump water through a corroding pipe is illustrated in the simple single
pipe system below (Figure 3.6.1).
23
Fig. 3.6.1: Conveyance energy requirement in pipes with different corrosion levels
In Fig. 3.6.1 (similar to the one depicted in Filion et. al. (2004)) an arbitrary datum of zero is
chosen to coincide with the centerline of the pipe. The pump that is assumed to be located at
the upstream end of the pipe (left hand side) is supposed to lift water to the stated static head
( downstream of the pipe by overcoming the frictional head-loss along the pipe. The total
energy needed is hence equal to the sum of static head and frictional head-loss along the
pipe. This study is aimed at estimating the net energy difference (benefit) on migration from
intermittent to 24-hour system by calculating the energy spent in overcoming the frictional
head-loss is pipe system.
Attack on the pipe material leads to thinning of the pipe walls or formation of precipitate.
Corrosion of metals, in general can be of different forms: a) an overall surface attack slowly
reduces the thickness, b) a localized area may be affected, or c) along the grain boundaries or
other areas which offer less resistance to the corrosive action (Charng, 1982). Apart from
causing a change in the water quality, thinning of pipe walls might increase the probability of
a catastrophic failure and formation of a precipitate will decrease the hydraulic capacity, due
to increase in friction and hence increase the pumping cost. Corrosion of water distribution
pipes happen in continuous as well as intermittent supply systems. The present study
Static head
Q
Static head
, Continuous Supply
, Intermittent Supply
Total Head
required (IS
system)
Total Head
required (CS
system)
Net Energy
Saved due to
migration
24
compares the rate of corrosion and its effects on the total energy embodied in water
transmission.
Corrosion occurs due to the electrochemical processes that take place on the metal surface of
the pipes. and is caused by an anodic area and a cathodic area occurring simultaneously on
specific points on the metal surface. Anodic and cathodic areas are formed by factors such as
non-homogenous metal composition, differential surface conditions, metal stresses or
variation in solution concentration.
It can also be caused by differential aeration cells, which are concentration cells resulting
from the differences in oxygen concentration between two parts of the system. During an
intermittent supply, where the system is not pressurised most of the time (on an average the
system is pressurised for 1.5-4 hours/day), water is left to stagnate in the pipe creating a
condition within the system where water and air are simultaneously in contact with the
metallic surface of the pipe (more like in an open channel flow at the air-water interface).
This results in a difference in potential between the portion of high oxygen concentration and
that of low oxygen concentration. states that the principle cause of corrosion in
water is the oxygen concentration cell and this crucial mechanism has not been given the
attention it deserves in most publications on corrosion, perhaps because it introduces an
apparent anomaly: Oxidation of metal occurs at a site where there is no oxygen. The
following Fig 3.6.2 ( ) depicts the series of electrochemical reactions that occur
during the corrosion process.
25
Fig. 3.6.2: Corrosion occurring at the water-air interface
Corrosion occurs in differential aeration cells at the area of low oxygen concentration.
During an intermittent supply, it occurs at the water-air interface which can be attributed to
differential aeration. Oxygen from the air is available to the meniscus area formed at the
water line. As oxygen is depleted at levels beneath the water line, the meniscus area becomes
cathodic to the immersed iron. illustrates the electrochemical processes involved
in the corrosive action caused when air and water are simultaneously in contact with the
metal surface, which is the pipe wall in the case considered here. Figure 3.6.2 depicts an
oxygen concentration cell where the chemical reactions involved are precisely the same as
those that occur in a galvanic cell. Since voltage produced by the cell is determined by the
chemical reactions, the potential of any oxygen concentration cell will be exactly the same as
in a galvanic cell where the corroding metal is the anode.
The oxygen concentration cell may be initiated by anything that will shield a small area from
the dissolved oxygen in the water, such as a grain of sand or a microbial colony. Such agents
which are responsible to initiate the process are known to be in abundance throughout the
water distribution systems in countries where intermittent supply exists. In hard waters, the
Tubercule: outer shell is rust (ferrous oxide) and inner shell is
black ferric oxide. Interior is void of oxygen.
26
alkaline cathodic reaction products precipitate calcium and magnesium compounds, which
deposit on the iron and shield a part of it from the aerated solution ( ). Since this
shielded area is deprived of oxygen, corrosion occurs here at the water line. Study conducted
by Koliyar and Rokade (2007) in Mumbai (Powai lake) showed the water hardness level to
range between 128-166 ppm and hence could be classified as Hard (with Soft ranging
between 0-60 ppm and very Hard having a concentration > 180 ppm). Once started, the cell
becomes self-perpetuating. The effects of the cathodic and anodic areas on galvanic
corrosion are very important. As the ratio of cathode to anode area increases the current
density at the anode increases making depolarization at the cathode more effective. Thus a
large cathode area and a small anode area would accelerate the corrosion process. According
to Charng and Lansing (1982), in such cases, corrosion of the anode may be 100 to 100 times
more than if the areas were the same.
Corrosive action due to the varying fluid velocities in conduit system is another important
factor that specifically affects pipes in an intermittent supply system, but has not been
touched upon in the past. Charng (1982) briefly describes how fluid velocity in the conduit
system affects the rate of corrosion. An increase in relative velocity between a corrosive
liquid and a metallic surface tends to increase the corrosion rate. This occurs due to the
increase in rate at which different corrosive substances are brought to the surface by the
moving water. Metallic corrosion is resisted by the layers of insoluble corrosion products that
settle on the surface. Higher velocities either prevent the normal formation of the corrosion
products or may remove them after (or as) they are formed. Hence thinner will be the films
through which corroding substances must penetrate and through which soluble corrosion
products must diffuse. In either of the cases the corrosion process would proceed unhindered.
27
Typically in an intermittent supply water would stagnate in the pipe for hours (from a few
hours to a few days) assisting the process of corrosion to take place at the water-air interface.
When the next flush of water is pumped or when supply resumes, high velocity of water in
the pipe and/or the accelerating fluid mass removes the corroding layers making way for
further corrosion to occur. Corrosion rate influenced by fluid velocity occurs frequently in
small-diameter pipes at high velocities (Charng, 1982). Velocity effects on corrosion rate
could be divided into various ranges depending on the velocity magnitude (Charng, 1982):
a) Slight motion (less than 0.3 m/s) may stop localizing attack such as pitting corrosion;
b) At around 0.3 m/s, the flow rate may increase the oxygen supply to a level that will
increase the rate of corrosion to as much as 1 mm/year;
c) At velocity range between 2.4 to 3 m/s the corrosion rate will be around 0.3 to 0.8
mm/year, depending on the surface roughness;
d) At velocities over 4.5 m/s, turbulence could accelerate the corrosion rate upto 5
mm/year.
Currently available literature does not address the effect of repeated line filling where the
accelerating liquid mass removes the corroding layers making way for further corrosion as
mentioned earlier.
3.6.2. Water Distribution System deterioration - Pipe Breaks
Distribution networks often account for up to 80% of total expenditures involved in water
supply systems. As water mains deteriorate both structurally and functionally, their breakage
rates increase, network hydraulic capacity decreases, and the water quality in the distribution
system may decline (Kleiner and Rajani, 2002). Also, 55% percent of the cause for breaks
can be attributed to material deterioration (Kirmeyer et al., 1994). It is essential for water
28
utilities to have short term operational plans to meet the consumer demand and have long
term infrastructure plans as distribution networks involve huge capital expenditures.
An important parameter that defines the reliability of a distribution system is its
susceptibility to breaks and bursts. Flooded streets due to water main bursts causing
inconvenience and heavy loss of resources are a common sight in India. Many factors
contribute to the rate of pipe breaks; material defects induced during water distribution,
ageing, corrosion from soil, water hammer or pressure surge and accidental or damage
caused due to unauthorized consumption. Though reasons are many, according to Shamir and
Howard (1979) the primary cause for the occurrence of breaks can be classified into
following categories:
1. Ageing of pipe and other appurtenances as well, which would include corrosion;
2. Type of environment in which the pipe is laid;
3. Quality of maintaining workmanship; and
4. Water supply conditions such as transient pressure conditions and water hammer.
Breaks occur in continuous as well as intermittent supply systems but extra care should be
taken in reducing the number of breaks when the supply is intermittent as further losses in
resources or additional financial burden would lead to further rationing. Agbenowosi (2000)
states that the cost of rehabilitation is the United States alone is estimated at more than 23
billion dollars. Also as intermittent supply systems are not sufficiently pressurised breaks do
not show up on the surface (Charalambous, 2012).
One of the common conditions that strongly influence pipe breaks is water hammer. Liquid
(water in this case) flowing in a pipe has two types of energy, a) potential energy and b)
29
kinetic energy. At any point in the system the sum of potential and kinetic energy is a
constant. Hence decreasing the flow rate (decreasing the kinetic energy) within the pipe
would result in an increase in the fluid pressure within the pipe as a result of increasing
potential energy. The immediate surge in pressure that generally occurs during rapid valve
closure, pump starts/shutdown, water-column separation and air movement in pipes is termed
as water hammer (or pressure transient). Water hammer is hence a pressure shock wave
induced in a plumbing system due to any rapid local adjustment of flow or pressure. The
instantaneous pressure shock wave of 150 psi or higher, tends to dissipate through the
system. Pipes, pipe joints, valves and other appliances absorb these shock waves, sometimes
causing a loud hammering sound and vigorous high amplitude vibrations. As a result of
continuous chemical attack as described earlier the pipes lose their bearing capacity and
become susceptible to physical damage. Due to the continuous line filling and valve
operations in an intermittent system pipes and other appurtenances are constantly subjected
to high intensity shocks leading to cracks, breaks and bursts more frequently. More details on
the occurrence and consequences of pressure transients are presented in Chapter 3.7.
3.6.3. Air Entrainment
Entrained air in water and wastewater networks has a deleterious effect on the system as a
whole the infrastructure environment and users. Air enters systems when it comes into
contact with flowing water and there is a favourable pressure gradient. Air entrainment may
occur in pumps due to turbulence at the inlet in dropshafts where water is transferred from
higher to lower elevations in open flow or at check towers if flow is partially full. Dissolved
air can also be released if temperatures increase or pressure drops occur; for example,
changes in pipe elevation or partially open valves, variations in pipe diameter can all cause
30
pressure changes. A 100 m length of watermain could contain 4 kg of total combined air.
This is truly a noticeable and significant amount (Lauchlan et al. 2005).
Entrapped air can reduce energy efficiency in pipelines by as much as 30%; it disrupts flow
in addition to increasing head-loss pressures energy consumption (Thomas, 2003) and
consequent greenhouse gas emissions (Maas, 2009). Higher pressures cause greater leakage
in the system, increases the chances of contamination and result in more frequent bursts as
well. The presence of air specifically oxygen in the pipes also increases the potential for
corrosion.
Pipelines are repeatedly filled and emptied in an intermittent supply, which causes the inflow
of air through faulty taps and open faucets. During an intermittent supply faucets are always
kept open as there is uncertainty about supply hours. The inlet of air resists the flow of water,
and hence the initial head needs to be increased to maintain the flow of water, which is again
a waste of energy. During rapid line filling, these air pockets can exert substantial pressure
on pipe walls, joints and valves. For example, Holley’s (1969) experiments and field work
suggest that storage and release of entrapped air can of initiate severe surges in pipelines.
During pump shutdowns, characteristic of intermittent supply, Albertson and Andrews
(1971) found that the maximum peak pressure could be 15 times the operational pressure. As
these high pressure conditions occur repeatedly during intermittent supply, regular but rapid
line filling is likely to lead to high rates of ruptures, bursts, leakages and other operational
problems. Hence it is no surprise intermittent systems usually have such high leakage rates.
31
3.7. Water Contamination
Contamination of drinking water being one of the most central problems in developing
countries, it is necessary to evaluate and understand how intermittent supply systems create a
favorable environment to facilitate the process of contamination.
3.7.1. Water Contamination during Pressure Transients
Contaminated water has become a serious cause for the outbreak of many diseases, and often
occurs due to frequent supply interruptions. This section describes how factors such as the
occurrence of pressure transients (water hammer) and water stagnation induces
contamination of conveyed water and more importantly why the effects are more pronounced
in an IS system.
The basic equation for the pressure transient, traditionally called the Joukowski Equation,
relates the change in pressure to change in fluid velocity (Tijselling and Anderson, 2006)
according to:
(3.7.1)
where is the sudden change in pressure, is the sudden change in velocity, is the
density of water (or fluid), is the speed of sound. Korteweg’s (1878) formula defines c for
liquids in cylindrical pipes with circular cross section as:
(3.7.2)
(3.7.3)
where D is the diameter of the pipe, e is the pipe’s wall thickness, E is the Young’s modulus
for the pipe wall and K is the Bulk modulus water (contained liquid). The magnitude of
32
pressure change is hence influenced by factors like pipe material, characteristics of the liquid
being conveyed and any rapid variation in fluid motion. Of these the primary cause of
concern is any operational change such as valve closure, pump shut down, fire-flows or even
pipe breaks that could potentially lead to rapid change in flow velocity. For instance if a
valve, considered on a pipeline at a distance downstream from a reservoir is closed
instantaneously, the water in the pipeline will decelerate to zero velocity thereby converting
the kinetic energy (possessed by the flowing water) into potential energy (pressure). The
pressure wave hence travels through the pipeline (i.e., upstream and downstream from the
valve) and if not absorbed by a surge tank, it will travel in the reverse direction back to the
valve (LeChevallier et al., 2003). As the valve is closed and there is no relief for the flow, a
negative pressure wave is created at the valve (Simon and Korom, 1997). This wave travels
back and forth until the energy is dissipated by friction (LeChevallier et al., 2003). However
the initial pressure would be positive on the upstream end and negative on the downstream
end (Simon and Korom, 1997). Pressure transients can also be caused by main breaks,
sudden changes in demand, uncontrolled pump starting and stopping, air valve slam and
other conditions (LeChevallier et al., 2003). Though circumstances that introduce transient
condition may commonly occur in any distribution system, certain conditions occur more
frequently in an IS system. LeChevallier et al. (2003) reports that as a rule of thumb, for
every 1 ft/sec (0.305 m/sec) velocity being forced to stop, water pressures increase 50 to 60
psi. The opposite would be true if there is a sudden velocity increase, resulting in an
instantaneous low or negative pressures (LeChevallier et al., 2003). Sudden increases
(changes) in demand with high peaking factor occur frequently when the supply is
intermittent as the consumers in a rush to collect water might not restrain filling or might
33
even use booster pumps. Andey and Kelkar (2007) study the systems in four different cities
in India that were operated continuously and intermittently at different times and report the
demand patterns.
Peak factor
IWS
Ghaziabad Jaipur Nagpur Panaji
6.15 4.38 2 6.4
CWS
3.06 1.66 2.02 1.98
Table 3.7.1
As reported in Table 3.7.1 (Andey and Kelkar, 2007) the peak factor in an IS system is can
be 2 to 3 times the peak factor in a CS system. Peak factor can be defined as ratio of the peak
diurnal demand during a 12 month period to the average day demand over the same period.
But Bose et al. (2012) report a peak factor to range from 3 to 12 due to IS in India. Transitory
contamination can occur when a negative or low pressure in the distribution system allows
untreated water to backflow into a distribution main through leakage points, submerged air
valves, cross connections, faulty seals or joints (Kirmeyer et al., 2001). Kirmeyer et al.
(2001) weighs and ranks the pathogen entry routes into the distribution system. Routes of
entry such a transitory contamination and water main breaks are termed as high risk. With IS
systems experiencing higher rates of water main breaks, this is certainly an additional cause
of concern.
To arrest the shock waves developed during transient regimes, surge tanks, air chambers or
other water hammer arresters are often used, but such strategies are costly. However, if the
arrestors are not completely water tight, the entrance of water hinders the cushioning effect.
To release the trapped water, the whole pipe system has to be drained (by opening the lowest
34
faucets first and then the other faucets) keeping the mains closed. Once the pipe system is
drained, the water present in the water-hammer-arresters is also expelled. The main valve
should now be opened allowing a fresh flush of water to fill the pipe system. This is just a
temporary solution and water hammer can still continue after a while as soon as water starts
entering the arresters. Considerable water is wasted in reducing the effect of water hammer,
and most water hammer mitigation techniques are not well-suited to intermittent flow
systems.
Further, tank agitation and disturbance of impurities are other serious problems induced by
water hammer. During water hammer the shock waves are transmitted up to the storage
tanks. These waves agitate both pipes and tanks and thus disturb the settled impurities,
bringing them back into suspension. This is observed to be causing key water quality issues
in the South-Indian city of Mangalore. As a result, even though treated water might be
delivered, it does not always reach the customers in a potable form.
Contamination due to intrusions could result in unnerving consequences people’s health. A
public relations officer in the Ministry of Defence reported that during a recruitment process
even 50% of the position could not be filled as the candidates failed in their medical tests due
to defects in their bone structure (Vajpai, 2012). Further investigation revealed that these
candidates came from arsenic affected regions in the Indian province of Bengal (Vajpai,
2012). Arsenic can affect any organ including bones causing deformity, degeneration and
brittleness (Vajpai, 2012). Increases in number of leaky pipes and more frequent pressure
transient conditions could induce the more polluted groundwater to enter into the pipes. The
problem is especially aggravated when supply pipes are close to sewage drains. According to
TOI (2012) a recent inspection by the concerned authorities in Bangalore (India) revealed
35
that sanitary and water pipes run next to one another and at some places the water pipes were
submerged in sewage. This is practiced as it is convenient to lay both the pipes (water supply
and sewage pipes) in the same trench (Fishman, 2011).
3.7.2. Water Stagnation in Pipes and Tanks
Contamination due to water stagnation occurs over two distinct stages (or sometimes three)
during intermittent supply. The first stage is in the distribution pipes where water is
invariably left to stagnate for long periods, inducing leaching, scaling, and corrosion, which
results in contamination. Copper is the most common material used in plumbing appliances,
and copper itself is capable of creating a health hazard if contamination is extensive. The
United States Environmental Protection Agency (USEPA) has found that even short periods
of exposure to copper can cause gastrointestinal disturbances, including nausea and
vomiting. According to the EPA, persistent (multi-year) consumption of drinking water
containing over 1.3 milligrams per liter of copper can cause liver or kidney damage (Water
Quality Association, 2005). Copper content in water is also responsible for corrosion and
deterioration of aluminium utensils and galvanised steel fittings. Fabbricino (2005) shows a
direct proportionality between copper concentration in stagnating water and stagnation length
for short periods, though not surprisingly for longer periods (greater than 48hrs) the trend
reaches a plateau.
The second stage of contamination occurs at the storage tank (underground or overhead). A
third stage of contamination is also possible if underground and overhead tanks are used
simultaneously. Lautenschlager et al. (2012) analyse the effect of overnight stagnation of
drinking water household taps. Though the study is confined to the stagnation in household
36
taps the cell concentrations reported to have increased 2 to 3 folds after the stagnation.
Microbial regrowth and its effects have been analysed by various studies and reports. There
are concerns in the drinking water industry regarding the health effects of HPC
(Heterotrophic Plate Count) bacteria that are found in sources of potable water (Rusin et. al.,
1997). HPC in drinking water should not exceed 500 CFU/mL because of the interference of
coliform detection. Higher numbers (HPC) in distribution system are often the result of
bacterial regrowth (Rusin et. Al., 1997). Microbial regrowth could play a vital role in
transferring antibiotic resistance factors to pathogenic bacteria and might also invalidate the
existing water quality monitoring programs (Evison and Sunna, 2001). In a joint research
Project aimed at studying the effects of microbial regrowth in distribution systems, increases
in HPC levels of up to five orders magnitude were reported in a 7-day period when the
supply was intermittent (Evison et. al., 2001).
In India, 85% of the people receive access to drinking water, but barely 20% receive access
to drinking water that meets health standards (Vairavamoorthy, 2007). Intermittent supplies
were responsible for the paratyphoid fever that broke out in New Delhi in 1996
(Vairavamoorthy, 2007). It is estimated that India loses at least 90 million days a year and
around Rs.6 billion in production losses and treatment (Ray, 2009). In Pakistan, because of
pollutants infiltrating into the leaky, damaged, non-pressurised pipes, many water-borne
epidemics swept the regions of Faisalabad, Karachi, Lahore, and Peshawar during the first
half of 2006 (AWDO, 2007). In Karachi (where half the 10 million population live in
informal slum areas) and Lahore (population 5 million), 40% of the water supply is
unfiltered and 60% of effluent is untreated (AWDO, 2007).
37
3.7.3. Privatization and Groundwater Contamination
Groundwater contamination is a serious problem particularly so in regions where consumers
are relying totally on groundwater for their needs. Arsenic contamination in North-Eastern
parts of India and Bangladesh and its consequences to the human health has been reported as
one of the world’s biggest natural groundwater calamities to the humankind (Ghosh and
Singh, 2009). Consumers essentially rely on handpumps and public borewells for water as
the municipal supply is either intermittent or just ceases to exist. These regions where the
supply is rationed are the same regions that have access to perennial fresh water sources.
According to data reported at the Indian Parliament in 2012, groundwater in 158 out of 639
districts has gone saline, in 267 districts groundwater in pockets were found to contain
excess fluoride, in 385 districts nitrate concentration was found to be over the permissible
levels, similarly 53 had excess arsenic levels and 270 with high levels of iron (Sethi, 2012).
It is almost inevitable that absence of reliable continuous water supply will tend to force
consumers to rely more heavily on the contaminated groundwater. It can also be expected
that in most cases they will be oblivious to the repercussions of water supply contamination.
Around 65 million people in India alone suffer from fluorosis which is a sometimes crippling
disease that occurs due to high levels of fluoride in drinking water and five million are suffer
from arsenicosis in the eastern province of West Bengal alone (Gupta, 2013). A UN report
says that over three million people die of water borne diseases in the world and in India alone
over 100,000 die annually (Gupta, 2013). Over 20% (around 300 MLD) of Bangalore’s water
demand is met through private borewells. Laboratory tests reveal that 53% of the borewell
water in Bangalore is not in potable form and contain Escherichia coli (E coli) bacteria
(Nataraj, 2013). The Center of Science and Environment reports another disturbing fact. Due
38
to the lack of sewage treatment and disposal facilities in the City, as many as 600 lakes in
Bangalore urban area have been turned into sewage tanks which contaminates the ground
water and percolates into the borewells (Nataraj, 2013). Another report by the Geological
society of India outlines some hard facts about Bangalore’s groundwater. Samples of
groundwater suggested that fluoride contamination is up to 5.3 mg/L as against a permissible
level of 1.2 mg/L (Madhusudhan, 2013). Nitrate (which affects blood cells) concentrations
range from 16-554 mg/L compared to a permissible level of 50 mg/L and chromium
contamination touched 17 mg/L when the permissible levels were as low as 0.05 mg/L
(Madhusudhan, 2013).
3.8. Summary
This chapter quantifies the consequences of intermittent systems. Through an extensive
literature review the current situation in developing countries with respect to water
distribution has been extensively discussed. Costs incurred by consumers in developed
countries for water consumption and coping costs incurred by different sets of consumers
facing intermittent supply have been compared. The reasons behind the increasing costs and
rising energy requirement to maintain intermittent systems have been examined. Various
forms of water contamination have been presented by highlighting the influence of
intermittent systems on water quality. To cope with intermittency consumers are often forced
to exploit groundwater which is disadvantageous in many ways as discussed in this chapter.
Efforts were made through Chapter 3 to present the deleterious effects of intermittent
systems and thus the need for migration towards a 24 hour supply has been justified. In the
following Chapter possible solutions for converting intermittent supplies into continuous
supply systems will be presented.
39
CHAPTER 4
Recommendations and Analysis of the possible solutions
Having argued that intermittent supply is neither a cost effective nor energy efficient way to
cope with water scarcity, it is important to find an alternative(s) that not only meets
consumer demands but in all possibility is sustainable.
The origin and causes of intermittency have been discussed in Chapter 2. Further on the same
lines, Totsuka et al. (2004) categorise the origin of the problems which would aid in our
attempts to arrive at relevant strategies. The three main categories of water scarcity according
to Totsuka et. al. (2004) are as follows:
a) Scarcity from poor management (Type 1): This could also be termed as perceived
scarcity. Even though the available water sources are sufficient to meet the consumer
demand, the supply must be rationed due to mismanagement of resources, excessive
wastage due to leakage, uncertainty in power supply or even complete negligence
from the respective municipal and Government authorities.
b) Economic scarcity (Type 2): Rapid urbanisation and population explosion in urban
areas could be the main cause of such a scarcity. When such a population increase is
not forecasted, poor planning in the past can lead to limited hydraulic capacity of the
system. In many cases Type 2 and Type 1 occur at the same time or as it is expected
Type 2 could lead to Type 1 in which case too it might seem that they occur
simultaneously. Generally it is hard to clearly categorise a particular situation as
purely Type 1 or Type 2. Bangalore well exemplifies this category, as rapid
industrialization during and after “Dot-com bubble”, saw 1000s of Information
Technology and Bio-technology companies being set up in the city. As planners were
40
not aware of the future demands and were taken by surprise as the City became a hub
for technology-based companies. The same trend could be observed in other cities
too. Though Mumbai is also facing rapid urbanisation, it was expected to become
India’s financial capital since Independence, hence could be categorised as Type 1.
c) Absolute Scarcity: This is the most difficult problem to solve as linking sources
located farther apart might not be realistic but again the issue might be at least partly
economic. However solutions have sometimes been found within water stressed
countries itself. Though consumers also need to cooperate and share responsibilities
in such cases Totsuka et. al. (2004).
4.1. Immediate steps to move towards a continuous Supply
Several immediate steps can be taken to help move a system away from being intermittent;
these are summarized here, with the most promising being to reduce the need of water
through an active and aggressive water conservation program.
4.1.1. Water Conservation
As analysed in Chapter 2, the issues forcing the municipalities to supply water intermittently
need to be dealt in isolation as every case presents a new problem. Water conservation
strategies are proposed through a framework developed for specific cases taking into account
demographic and socio-economic factors. While water demand management techniques
consider all aspects relating to efficient use, water conservation to minimize water loss is
confined water resource efficiency.
The following solutions and strategies are aimed at controlling the demand and reducing
wastage.
41
4.1.2. Water Demand Management
Water demand management (WDM) is the implementation of strategies to more efficiently
use water by curtailing unnecessary consumption particularly if those reductions can be
achieved without reducing the quality of life; the goal of demand management is to foster
social development, social equity and sustained water supply. WDM has not been fully
recognized in developing countries, as it is considered an objective but not a strategy (South
African Government Online, Draft-15, 2000).
Underground and Overhead Private Tanks: Continuous supply is only possible if the utility
has sufficient water to supply the demand throughout the day. If consumers, as they always
practice when the supply is rationed, collect as much water as they can, water utilities can be
under extreme stress to cope with such a peak factor. Hence as a first step consumers should
strictly stop using private tanks or booster pumps. However as it is impossible to prevent
consumers from hoarding excess water through other means their daily consumption must be
indirectly controlled. There are three ways to implement such a practice:
1) Stringent Billing Process: This method employs installing smart electronic water
meters at individual residential units which keeps a record of daily usage as well as
the monthly usage. The smart meters being considered here are capable are
communicating with the servers managing and processing the datasets. Such meters
that are available today (e.g., Sensus, FlexNet) are capable of sending data on an
hourly basis. On a per-capita consumption basis, 155LPCD (CPHEEO, 1999)
household consumption should be billed normal rates. In cases where the daily
consumption exceeds the stipulated 155 LPCD, the amount exceeding the limit
42
should be billed at exorbitant rates. These rates must be fixed based on the price of
commercially available drinking water. This would ensure the consumers will have
enough water for their daily needs but the onus would be on them to make sure they
do not waste or collect more than what is required.
2) Fix a daily quota for water usage: Fixing a daily quote can be an effective strategy if
every household is allowed to collect a set volume of water every day. After the
diurnal limit is reached the Flow Management Device will stop the supply for the
particular residential units for the day. Also, depending on the water affordability,
consumers can choose their daily quota and hence plan their consumption.
This new water management practice is already in place in Cape Town (South
Africa). The device is set to deliver an average of 350 L/day or 10.62 L/month
( ). If households use anything less than their daily quota, the remaining
amount will be carried over to the next day.
As the price of water is very low in India (e.g., 10 cents/1000 L in Bangalore) middle
class and upper middle class households tend to use much more than the required
amount. For instance middle and upper middle class households in Bangalore often
use 250 to 300 LPCD. Again, a middle-class consumer in Mumbai consumes the
same amount of water as his/her counterpart in Shanghai (Varghese, HT) while the
supply in Mumbai is still intermittent. Hence if such strict measures are brought into
place i.e., with a strict consumption 155 LPCD, water demand (for its 12 Million
citizens) in Mumbai alone can be brought down to 2139 MLD (which includes 15%
loss due to leakage).
43
4.2. Pressure Management and Leakage Control:
Though a complete system overhaul is needed in regions with ageing pipes, it is an expensive
and time-consuming process especially in the developing countries where ample data on pipe
locations may not be readily available. Also, a slow process is preferred as initially it is
required for consumer behaviour to adapt to continuous supply. Even if it takes a few years
to replace all the ageing pipes and completely migrate towards a 24/7 supply, water and
energy conservation strategies should be implemented immediately. Only if the
municipalities have enough resources is a system overhaul or a migration feasible. With IS
systems experiencing leakages ranging from 30% to 50% of the supplied water, leakage
reduction is an important and cost effective way to improve the supply conditions as minimal
additional infrastructure is required. Since high pressures increase leakage, pressure
management through leakage reduction is crucial.
Pressure management: Some developing countries face a serious water scarcity problem.
In such cases, an immediate migration to a 24-hour supply would seem to require completely
new water sources. If this is infeasible, the migration should occur in phases where the water
boards can plan and implement demand management and leakage reduction strategies. Hence
the best water boards can do in these cases is to improve supply conditions initially so that
the consumers stop hoarding water. The basic idea here is to reduce the peak demand and
diurnal demand to assist water boards to have enough water to supply demand over a longer
duration. In other words water should be supplied to consumers more frequently at a constant
pressure. For instance if presently the daytime supply period is for 2 hours, it could be
improved by re-distributing the supply period between two separate durations of 1 hour each
44
during different peak hours. In such an improvised supply system, consumers would collect
only the required volume of water as they are confident of promptly receiving the next flush.
Hence this would solve the problem of wastage which otherwise would be prevalent as
consumers tend to discard the stored water when they get the next flush.
South Africa was one of the first countries to implement pressure management on a large
scale, and the results of their efforts were fruitful. Pressure management was undertaken in
Cape Town and results were reported for the township of Khayelitsha. Water was supplied to
around 27,000 small housing units, a population of 45,000. At the beginning of 2000, water
supplied to this town was measured to be 22 million m3/a (McKenzie, 2009). Leakage from
night time water usage was three quarters of what was supplied, due to excessive night-time
pressures where water was supplied at a rate of 1600 m3/hr (McKenzie, 2009). The main
source of this leakage was identified as household plumbing and fittings which were
constantly exposed to high pressure of around 80 m. These leakages result in high
consumption and people would not try to replace expensive taps and fittings.
An excellent way to reduce the leakage level is to divide the network it into permanent
sectors which are supplied by a single pipe on which a flow meter is installed. In this way it
is possible to easily detect a new leak and know from which part of the network it comes
(Rogers, 2008). The application of a mathematical model that simulated key hydraulic
features would solve the problem of numerous interconnections and inaccessibility to various
elements of the network. For a good mathematical model to be developed, relatively perfect
datasets and appropriate estimation techniques are needed to assess the consumption pattern.
Thus for the simulation to be precise, historical consumption of the customers could be
extracted from the billing database by street and type of customer. As performed by DEWI
45
Srl in Lucca (Italy), an extensive monitoring program could be undertaken in similar cities
(i.e., cities with similar characteristics) to derive a demand profile for customer types. By
successfully simulating the network operation it is also possible to find and close the pipes
with little hydraulic importance without causing serious service problems to its consumers
(Rogers, 2008). Analyses of the results show that the application of these strategies yielded a
leakage recovery of 72 L/s or 2.2 Million /s in Lucca(Rogers, 2008).
4.3. Improved Metering and Billing Procedures
Maintaining a system where all the connections are metered is important not only because of
improved revenues but also for generating consumption data for future planning and leakage
detection. Observations and surveys on installed meters will allow for a better estimate of
non-revenue-water and would help determine the investment needed to replace these meters,
while research on them would help to determine reasons for their faulty behaviour. Also
consumers should be discouraged from tampering with a metering system, with stiff
punishments for violation.
Appropriately revised rates and Billing in Stages
General water rates must be revised to recover the operation and maintenance costs of the
water distribution system. Due to a great income disparity between socio-economic
communities in developing countries, fixing a general rate would be unaffordable for low
income consumers while simultaneously failing to de-incentive misuse and wastage by
higher income consumers . Hence it is important to determine the appropriate rates. The
revision should either be based on consumers’ Willingness To Pay or by determining what
percentage of consumers’ household income would an average water bill be in developed
46
countries with 24/7 supply. In Toronto, the cost of municipal water is set at $2.7/kL (TCC,
2013). Though per-capita water consumption in Canada is much higher compared to
developing countries, an average household consuming 18,600 L would pay $51/month.
According to StatCan as an average Canadian family earns $68,000/year (Canada) (Grant,
2013), the water bill would hence be around 0.9% of the household income. Hence the city
or town must be divided into different metering zones based on the average household
income of consumers in each zone. For instance if the average household income in a
particular metering zone in Bangalore is USD$14000/annum (or USD $1167/month) the
monthly water bill should be around USD$10.5/month (for a stipulated consumption of 155
LPCD). That would mean a fivefold increase in water charge from Rs.6/kL (USD$0.1)
(BWSSB) to Rs. 33.88/kL (USD$0.56). It may seem that the consumers might not readily
accept the new rates, but given the coping costs involved with intermittency they would
likely readily agree if the boards were to promise a much more reliable and continuous
supply. Also billing should seldom be on a flat rate which means Rs. 33.88 /kL that is being
charged is not on a flat rate. Table 4.1 presents a sample set of slab-rates.
Monthly Consumption
Slab rates (Rs./kL)
Slab rates (USD $/kL)
6000 8 0.13
6000 16 0.267
6000 24 0.4
6000 87.5 1.46
Table 4.1
The first column shows the monthly household consumption of 24000 L (200LPCD for a
household with 4 members). The first 18000 L (150 LPCD) would be billed on an average
rate of Rs. 16/kL (USD $0.27/kL) and the remaining 6000 L (50 LPCD) would be billed on a
47
quite exorbitant rate of Rs. 87.5/kL. The variation in the slab rates is aimed at providing the
required amount of water (135-150 LPCD) to consumers at a low rate at the same time
discouraging them from hoarding excess water or wasting. Depending on the average
household income the slab-rates must be modified.
4.4. Model Resource Management Strategies and Long Term Plans
Appropriate distribution management measures will also aid in leakage control and meter
management. Some useful measures, either being planned or already implemented, were
found in the literature (Draft-15, 2000, Rogers, 2008):
a. Maintaining water zones and Meter management: Dividing an area into water districts
and subzones makes management and implementation easier and more achievable. The
first priority is to install meters in zones which would be used to find average
consumption, peak consumption, and leakage losses. Initially in each zone, accurate data
needs to be collected regarding the consumption behaviour, location of water treatment
plants and service tanks, pipeline locations and their alignment, demand pattern of the
zone, and most importantly leakage points and faulty meters (these are done particularly
when converting from intermittent to 24-hour supply). Making use of satellite imagery
and GPS, all data should be co-ordinated and synchronised, helping to better prioritize
key zones. Further, managing pressure so as to maintain equitable distribution will be
more effective if the selected zones are smaller. In a typical case in Badlapur dividing
the supply into operational zones was the key strategy in a complete migration from
intermittent to 24-hour supply (e-gov, 2008). Different operational zones were
demarcated from the other zones based on the storage capacities of the service reservoirs
and consumer withdrawal pattern. The service reservoir supplies water to the
48
Operational Zones. Dividing the operational zones into discrete district metering areas
greatly helped in reducing leakage (as it could easily be detected) and controlling high
flow rates through suitable methods. The model prepared has become crucial for
metering strategy. Costly bulk meters previously used to determine net night flow were
all replaced by this model, which saved an estimated Rs.8 million.
b. Retrofit of existing plumbing and fittings: It is estimated that, by replacing existing
plumbing fittings with more efficient fittings, household and commercial water
consumption can be reduced by an average of 15% to 50% of household and commercial
water use. There are various new innovative ideas in this regard. Plumbing retrofitting
may include fitting dual flush, interruptible toilets, low-flow shower heads, tap
controllers, aerators and user-activated urinals (South African Government Online,
Draft-15, 2000).
c. Economy pumping: Energy costs vary at different times of the day and economy
pumping is a valuable strategy in such areas. Pump Scheduling Systems for water
utilities target load movement from peak to off-peak periods chasing the tariff
differential to achieve energy cost savings (Bunn, 2007).
d. Recommendations for Better Water Resources Management:
Water resource management is crucial for water systems and to society well. Various
strategies are summarized here, many of which are mentioned in the online document of the
South African Government Online (Draft-15, 2000).
1. Source Water Protection: Constant tests should be carried out on water sources and
suitable steps should be taken to maintain the quality. Due to improper urban planning in
most of the developing countries, cities have become so impermeable that few places
49
exist for the rain water to seep into the ground. Hence recuperation or rehabilitation of
water resources, especially groundwater sources, should be implemented in urban areas
of developing countries.
2. Imposing strict penalties on booster pumps and illegal connections: Illegal connections
and booster are one of the main reasons for lost revenue and drop in pressure. Also a
moratorium should be placed on private groundwater usage in regions where sufficient
surface water sources exist. The available groundwater sources must be used by the
municipalities for equitable distribution. The law should therefore strongly enforce the
removal of illegal connections and the fines collected from defaulters must directly go
towards improving the water supply. As reported earlier, if the groundwater usage is
metered and supplied through the municipality, even with the existing rates the water
boards will have an additional revenue of USD $71 million per year.
e. Integrated Resource Planning
Integrated water resource planning and management has become a new model for water
policy development. Global Water Partnership defines integrated water resource
management as “a process that promotes the co-ordinated development and management of
water, land and related resources in order to maximize the resultant economic and social
welfare in an equitable manner without compromising the sustainability of vital ecosystems”
(IRC, 2004).
During the implementation of demand management, the primary focus is to decrease water
demand. This affects the supply management to an extent that the supply can be distributed
to more customers, thus increasing the supply capacity without actually altering the quantity
50
of water provided. Hence this “extra” water has become a “product” due to good planning
and management.
It is important to note that water is normally used for the services derived from it, and not for
the water itself (South African Government Online, Draft-15, 2000). Such applications can
include:
1. Garden Watering: Watering a garden is intended to ensure that plants receive enough
water to carry out metabolic activities. Recycled water thus conserves considerable
potable water while the purpose of gardening is served equally well. Plants should
always be watered in the morning or evening and never during bright sunlight, which
leads to excessive losses. Outdoor potted plants are more exposed to sun and wind and
have only a small amount of potting mix to store water; thus, for water conservation,
ground plants are superior to potted plants.
2. Cooking: Boiling food on an open saucepan consumes substantial water with little
practical use, as most of the water vaporises and leaves the food uncooked. The most
water-efficient way of cooking are microwaving, or steaming using a pressure cooker.
Vegetables boil quicker and it will save water and power.
3. Hand Washing: Elmwood Park (2011) estimates that an average person uses around 1
gallon (3.76 litres) of water each time they wash their hands. Assuming people wash
their hands at least 12 times a day, large amounts of water could be saved if hand
sanitizers are used where the cleansing effect is more pronounced and hygienic, though a
life cycle analysis would be required to determine the water use associated with
production and transportation of the hand sanitizers. More work is also needed to
determine the optimal level of hygiene associated with hand washing.
51
4.5. Model Strategies
Broader strategic measures can also be taken to mitigate the negative effects of intermittent
supply. These model strategies are implemented based on some common prevalent problems.
Solutions through a sample study of Bangalore City have been provided in Chapter 5.
Measures and strategies to meet non potable requirements: Untapped Wastewater
Source-India
Out of about 38000 MLD of sewage generated treatment capacity exists for only about
12000 MLD (CPCB, 2009). Discharge of untreated sewage in water courses, both surface
and groundwater, is the main source of water pollution in India. Out of the 15644 MLD of
sewage generated form the 35 metropolitan cities in India treatment capacity exists for only
8040 MLD (51%). However out of the 35 cities New Delhi and Mumbai have a combined
treatment capacity of 4460 MLD, which is 55% of the total capacity.
Water reuse is the strongest conservation technique: after treatment, sewage water can be
used for various purposes like gardening, irrigation etc.. Israel achieved 65% reuse levels by
2003; almost 50% of the total irrigation sector used treated sewage effluents (Saul, 2004).In
Singapore 50% of the nation’s water needs are met by recycling through the “NEWater”
project. Launched in 2003, the project is aimed at recycling wastewater to purified potable
water in an eco-friendly and cost-efficient way.
Wastewater treatment could be the best option for water scarce countries with high
population density. Waste water treatment can serve two purposes,
52
1) Reduces the dependence on freshwater sources for non-potable purposes
2) Preserves the fresh water sources by preventing it from getting polluted
Though financial constraints and energy shortage have been given as the main reasons not to
adopt wastewater treatment, the cost of losing a precious water source due to pollution or the
cost of finding a new source could be much higher.
4.6. Summary
As water conservations is the key factors that decides how successful the migration can be,
this chapter focuses on conservation right from the consumers’ level. The basic idea
presented here is that if less water is consumed by the users and if water losses are controlled
then the municipality would have sufficient amount of water for a 24 hour supply. Some of
the conservation strategies presented have applied and tested by various municipalities great
results were observed. As mentioned in Chapter 2 lack of financial resources are also
majorly responsible for intermittent systems. Hence this chapter attempts to assess the
possibility of implementing various billing strategies and imposing tariff levels that falls well
within consumers’ WTP (willingness to pay) levels. Further discussion is presented through
a case study in Chapter 5.
53
CHAPTER 5
Case Study of Bangalore and Mumbai
Mumbai and Bangalore are two important cities of India that rose to prominence at different
times in the Indian history. Despite their economic growth, both cities have faced many
challenges, with intermittent water supply being but one of them. With a combined
population of over 28 million (Ray, 2013; PIBS, 2011) this problem should not be
overlooked. However, municipalities and water boards are under the assumption that the
intermittency is saving water and thus helping them overcome water scarcity. Also as the
deleterious effects of intermittent supply are not well quantified, and have become to large
extent accepted as a cultural norm. The following case study closely examines and quantifies
the effects of intermittent supplies in Mumbai and Bangalore with the specific goal of
addressing this complacency.
5.1. Comparative Energy and Cost Analysis of Continuous and Intermittent Supply
Systems – Mumbai, Case Study
Mumbai Water Distribution System Description:
Mumbai, formerly known as Bombay, is the capital city of the Indian state of Maharashtra. It
is the most populous city in India, and the fourth most populous city in the world, with a total
metropolitan area population of approximately 20.5 million, out of which slum population
constitutes 6.5 million. Mumbai lies on the west coast of India and has a deep natural
harbour.
The Hydraulic Engineering Department of Municipal Corporation of Greater Mumbai
(MCGM) is responsible for water supply in greater Mumbai area. In 2005 Mumbai with a
54
population of around 12 million (excluding the slum population), had a water supply
requirement of 3900 Million Liters per Day (MLD) (MCD, 2005). Mumbai’s water supply
was established though various schemes since 1860.
Fig. 5.1 (Source: Uitto and Biswas, 2000): Map showing Mumbai’s various water sources
A brief description of the schemes is as follows (MCD, 2005):
55
a) Vihar Scheme: The Vihar scheme was the first water supply scheme commissioned in
the year 1860 to supply 32 MLD to a population of 700,000. Supply from this source
was later increased to 68 MLD by rising of the dam in 1872 which is still operational
today.
b) Tulsi and Powai Scheme: In 1885 it was decided to develop Tansa as the second
source of water supply but a critical water shortage led to the development of Tansa
lake, upstream of Vihar on Mithi river. This scheme was commissioned to supply 18
MLD though at the same time Powai scheme, which was supposedly so supply 4
MLD is no longer in use due to inferior water quality.
c) Tansa Scheme: The four major sources of water supply to Mumbai city today are
Tansa, Vaitarna, Upper Vaitarna and Bhatsa. The Tansa scheme consisted of four
stages, first stage being completed in 1892 and final stage in 1948. The total water
supply from this stage is about 410 MLD.
d) Lower Vaitarna Scheme: At the end of Tansa scheme in 1948 Mumbai’s water supply
was 495 MLD. But after independence from the British rule India and Mumbai saw a
large influx of people which increased the demand for water supply. Hence the
Vaitarna scheme was planned and completed in 1957 adding 510 MLD to the City’s
water supply.
e) Upper Vaitarna Scheme: The State government in 1960 took up the Upper Vaitarna
scheme. This project was fully commissioned in 1972 and water supply was
increased by 540 MLD.
56
f) Bhatsa Scheme: Due to acute shortages that started arising towards the end of 1960s
Bhatsa scheme was commissioned. The project was implemented in three stages and
in each of these three stages 455 MLD water was drawn from the Bhatsa river.
g) I Mumbai Water Supply Project: At the end of Stage I (or Bhasta Stage I) the total
water supply to the City was 1970 MLD.
h) II & III Mumbai Water Supply Project: At the end of Stage II and Stage III the City
had 2900 and 3400 MLD of water respectively.
5.1.1. System Parameters and Projected Demand
Data pertaining to the system parameters was retrieved from MCD (2005) which elucidates
the city water distribution and sewage plan for the period 2005 to 2025. The City’s
distribution network is being laid and upgraded for over 136 years. The total length of the
distribution mains is about 4000 km with the diameter ranging from 80 mm to 1800 mm.
Though it is known that the mains were either of cast iron or ductile iron the exact length of
pipes corresponding to a particular diameter or type was not available in the literature, and is
likely at least partly uncertain in the field. Yet this data was essential to at least roughly
estimate as it is necessary part of determining head-loss over the years, a value dependent on
the initial roughness which is slightly different for the two materials and strongly dependent
on diameter. To move the discussion forward, these crucial hydraulic variables were
provisionally and indirectly estimated. Ductile iron pipes were introduced in Philadelphia
(USA) (PWD, 2013) and also in the UK in the mid 1960s (Gunter, 2010). Around that time
(mid 1960s) total water supplied to Mumbai City’s was around 50% of the present supply
hence it could be assumed that the distribution mains installed after this period were made of
ductile iron. Sterling et al. (2009) reports that 12.4% of the distribution mains have diameter
57
less than 150 mm, 73% of the mains are less than 250 mm (dia.) and 89% are less than 400
mm. Hence for the present study same scenario was aimed by assigning appropriate lengths
for the respective pipe diameter. Discussing with the local municipal officials and with the
knowledge of the commercially available pipes, for Cast Iron pipes of diameter 200 mm, 300
mm and 1500 mm lengths of 1660 km, 300 km and 80 km were assigned respectively.
Similarly for Ductile Iron pipes with diameter 150 mm and 600 mm lengths of 1660 km and
300 km were assigned respectively, totally adding up to 4000 km of distribution mains. But
after discussing with water board authorities at a pipe replacement site (23rd
May 2012,
Bangalore, India), the total length was divided into pipes with diameter equal to 150 mm,
200 mm, 300 mm, 600 mm, 1500 mm. EPA (2007) reports that 50% of the pipes that
constitute the distribution mains are made of cast iron.
Lifecycle energy requirements for manufacturing DI (Ductile Iron) and CI (Cast Iron) pipes
were retrieved from Du et al. (2012) where the results of corresponding LCA was reported.
The corresponding pipe wall thickness for each diameter was calculated by assuming a
maximum internal pressure of 200 m (Filion et al., 2004) and an operating hoops stress at
half the yield strength (i.e., factor of safety equal to 2).
The study was conducted for a planning period of 100 years. Hence the average population
and demand was projected over the period. The projected water supply and demand for
Mumbai from the year 2001 to 2021 is given below:
Year Supply
(MLD)
Demand
(MLD)
2001 3025 3975
2005 3175 4150
2007 3375 4300
2011 3852 4526
58
2016 4307 4800
2021 5172 5068
Table 5.1
With the above data the demand growth rate (for a period between 2001 and 2021) was
found to be 1.18%. However from 2021 to 2031 the projected population growth is around
0.788% (TRANSFORM, 2005). Also due to stabilization of Indian economic growth, rising
cost of living in Mumbai and increasing opportunities in other cities would divert the growth
to other parts of the country thereby further reducing the population growth rate in Mumbai.
Hence an overall growth rate of 0.3% was assumed for the planning period.
While selecting the time-step it was assumed that all the parameters would remain constant
over the period. A coarse time step was chosen as the variation in parameters like roughness
growth rate, demand, breakage rate, to name a few, cannot be estimated with a shorter time
step. With few available models it was believed that a coarser time step would closer
estimates, and that finer estimates could not be justified in any case. Also the achievable
accuracies in energy estimates with a shorter time step could be negated by uncertainties in
other simulation parameters (Filion et al., 2004).
5.1.2. Consequences of Pipe ageing on Transmission (Pumping) Energy loss
The roughness growth model developed by Sharp and Walski (1988) was used in the present
study to simulate and compare the effect of pipe ageing on net energy expenditure between
the two systems. Sharp and Walski (1988) arrived at the roughness growth model by
combining Hazen-Williams and Darcy-Weisbach equations for head loss. The model relates
Hazen-Williams friction co-efficient to time dependent roughness of pipe.
59
(5.1)
(5.2)
where, C is the Hazen-Williams friction co-efficient, initial roughness height during
pipe installation (new pipe), = the roughness growth rate, t = the number of years since
installation, D = internal pipe diameter, e = time dependent roughness height.
a. Initial roughness height and Roughness growth rate assessment:
Two models developed by Colebrooke and White (1937) and Sharp and Walski (1988) were
initially considered to arrive at the roughness growth rates and they are briefly described as
follows:
With the data gathered from New England Water Works Association (1935), Colebrooke and
White (1937) arrived at the following expression:
2 log a = 3.8 – pH, (5.3)
Or
(5.4)
where a is the roughness growth rate (inch/year). The data in NEWWA (1935) was presented
based on William-Hazen formula which is not velocity independent. Hence to convert it to
Chezy’s co-efficient they had to assume that the velocity was 4 feet/s. However this model
has been described in Colebrooke and White (1937) as “a little better than guess”.
Lamont (1981) presented a thorough set of data that relates Langelier Index with different
trends in roughness growth. Sharp and Walski (1988) compiled the data presented by Lamont
(1981) to arrive at the model described below:
60
(for LI<0) (5.5)
where LI is the Langelier Index.
Langelier Saturation Index (LI), a measure of a solution’s ability to dissolve or deposit
calcium carbonate, is often used as an indicator to corrosivity of water. Though the index is
not related directly to corrosion, it is related to the deposition of a calcium carbonate film or
scale. When no protective scale is formed, water is considered to be aggressive and corrosion
can occur. An excess of scale can also damage water systems, necessitating repair or
replacement.
In developing the LI, Langelier derived an equation for the pH at which water is saturated
with calcium carbonate (pHs). This equation is based on the equilibrium expressions for
calcium carbonate solubility and bicarbonate dissociation. To simulate actual conditions
more closely, calculations were modified to include the effects of temperature and ionic
strength. The Langelier Index is defined as the difference between actual pH (measured) and
calculated .
LSI (or LI) = pH – pHs (5.6)
Where, pH = the measured pH of water and pHs = the pH in the calcite or calcium carbonate
and is defined as
= (9.3 + A + B) – (C + D) (5.7)
Where,
A = (5.8)
B = (5.9)
C = (5.10)
D = (5.11)
61
The magnitude and sign of the LI value show water’s tendency to form or dissolve scale and
thus to inhibit or encourage corrosion. Although information obtained from the LI is not
quantitative, it can be used as a general indicator of the corrosivity of water.
Various sources were examined to retrieve the water quality data for the Mumbai City
required for the calculation of Langelier Index. Chandra et.al., (2012) assessed the drinking
water quality in Mumbai (Vihar lake) among other Indian cities. The assessment presents,
pH, Total Dissolved Solid (TDS), average Temperature, water hardness and alkalinity in
Vihar Lake.
Initial roughness height ( ) is another important parameter needed to implement the model
proposed by Sharp and Walski (1988). Sharp and Walski (1988) report the initial roughness
height ( ) to be 0.18 mm for a new metal pipe with sizes ranging from 150 mm to 600 mm
(dia.). These values were further used for Life Cycle Energy Analysis by Filion et. al.,
(2004). Lamont (1981) recommends typical values of initial roughness height to be 0.25 mm
for Cast iron (CI) pipes. Hence an initial roughness height of 0.18 mm was used for DI pipes
(with diameters ranging from 150 mm to 600 mm) and 0.25 mm for CI pipes of all sizes.
Another important factor that dictates the value of friction head-loss in pipe systems is the
volume flow rate (
). Estimating the flow-rate in a continuous supply system is relatively
a straightforward process due to the available hydraulic models and constantly monitored
networks. But in an intermittent system various factors like availability of water, power
shortages, uncertainty in the duration of supply, varying peak factors and constant pipe bursts
significantly influence the flow rate. With a large volume of water being supplied through a
short time span, minor changes in the supply duration would greatly affect the flow-rates.
Hooda and Desai (2012) in their techno-economic feasibility study of a water supply scheme
62
in Upper Vaitarna (Mumbai) estimate the flow velocity to be 1.25 m/s. Andey and Kelkar
(2007) compare the performance of systems in India during intermittent and continuous
supplies. This interesting study compared the average flow-rates during the supplies. From
the reported values the flow-rate ratio (intermittent to continuous) in four cities ranged from
1.27 to 5.26. Hence in the present study it was assumed that the average flow rate in an
intermittent system would be 1.27 times that in a continuous system.
As discussed earlier in this chapter, intermittent flow creates an ideal situation inside the
distribution system to assist and accelerate the process of corrosion. Though there is ample
evidence in terms of rapid deterioration of infrastructure, high leakage and breakage rates
surprisingly, no study has been carried out to estimate the higher levels of corrosion or the
increase in roughness growth rates in an intermittent system.
As it is expected an increase in the roughness height/growth rate would reduce the Hazen-
Williams co-efficient considerably resulting in an increased head-loss, which means the
pumps should need more energy to lift the same volume of water. In simple mathematical
terms the energy difference (between continuous and intermittent systems) is expressed as:
W = (5.12)
where,
W = Net conveyance energy difference between continuous and intermittent systems, =
Density of water (1000 kg/ ), g = Acceleration due to gravity or gravitational constant (9.8
), = total dynamic head delivered by the pump in a continuous supply system, =
total dynamic head delivered by the pump in an intermittent supply system, Q = Total
volume of water delivered by the pumps ( ), = Pump efficiency.
63
b. Pipe Replacement
Researchers, over the years have tried to link the occurrence of pipe breaks and leaks with
ageing. As mentioned earlier many factors are responsible for pipe breaks and the extent to
which they influence actual breaks inevitably varies from case to case. For instance if the
large difference in temperature is in a way responsible for pipe breaks and leaks in colder
countries, negative pressures and frequent water hammer pressures may have a larger impact
in tropical countries. Hence as data on such factors is scarce and not to mention the difficulty
in accounting for various other intrinsic factors, researchers have relied on statistical
approaches to simulate pipe breaks in the systems. The values for the growth rate were
gathered from various studies and compared to arrive at a typical value. A brief description
of the literature reviewed is presented below. Shamir and Howard (1979) describe a
procedure that uses the history of main breaks to forecast how the number of breaks would
change with time if the pipe were not replaced and a separate analysis predicts the failure of
newly installed pipes.
(5.13)
where, is the number of breaks in a pipe i after t years of replacement; is the
breakage growth rate (increase in the number of breaks per year); is the year 0 or the year
of replacement; is the number of breaks in the pipe i in the year of replacement.
The exponential relationship between the pipe breakage rate and their age developed by
Shamir and Howard (1979) was further applied with minor fine-tuning by Walski and
Pellicia (1982) to provide a cost analysis for pipe replacements and breaks. Clark et al (1982)
developed a linear equation to determine the time from pipe installation to the first break and
an exponential equation to determine the breakage rate after the first break.
64
It has to be understood that these models developed over years are valid for continuous
supply systems and do not take into account the intermittency in supply conditions. As the
study here is focused on intermittent systems the approach was modified to accommodate the
intermittency factor. For such an attempt to be successful data must be collected from a
typical scenario of a system that has been transformed from (or to) an intermittent to (or
from) a continuous supply system. Pipe break data from such a system must be collected
before and after the transformation. Charalambous (2011) collected the data from such a
scenario that occurred due to severe water shortage in Lemesos, Cyprus, in 2008/09. In the
study conducted by Charalambous (2011) it was evident that there was a large increase in the
number of reported pipe breaks during the period of intermittent supply. In order to quantify
these a comparison was made by Charalambous (2011) for a large number of District
Metered Areas, 20 in total, between the breaks reported in 2007, before the intermittent
supply was applied, and those reported in 2010, the first year immediately after the measures
were lifted. This comparison showed that the number of breaks on mains increased from an
average of 1 per 7.14 km of mains to 1 per 2.38 km of mains, an increase of 300%. If the
above figures are translated to the number of breaks per unit length the increase would be
from 14 breaks/100 km to 42 breaks/100 km. It should be noted here that in the above case
the system was operated continuously though the rationing occurred just for a period of three
years. Pipes in a system which has always been operated intermittently corrode faster than
pipes in a continuous supply system. Hence in such a (continuous) system where the rate of
deterioration of pipes is far less compared to a system that is operated intermittently by
default, the increase in breakage rate was observed to be 300%. Also in an intermittent
supply system the leaks and breaks often do not surface and hence go undetected as the
65
system is not pressurised. To make the situation worse, most cities in countries like India
where people are grappling with water related problems, have highly unreliable data
collection records. Based on the facts gathered from WSP (2008) only Jamshedpur,
Bhubaneshwar, Bangalore and Hyderabad have maintained an acceptable record of pipe
breaks. However even the available data from a few Indian cities show that the breakage
rates are enough to warrant concerned. Breaks occurred in Bangalore and Hyderabad at the
rate of 5.23 per km and 3.97 per km respectively (WSP,2008), which is quite high when
compared to the situation in industrialized countries like Canada where the number of breaks
range from 0.098 to 0.367 per km depending on the pipe material (NRCC, 1993). Hence it is
evident that though Charalambous (2011) noted just a 300% rise in the number of breaks, in
a system that is operated intermittently by default the number is easily over 10 times that of a
continuous pressurised system. For the case of continuous supply system the values for the
initial break rate were taken from the literature reviewed. In a similar study presented
by Filion et al. (2004) a typical initial break rate of 0.04 break/km/year was applied for all
steel pipes in the NYC water supply system.
With the data retrieved from the reviewed literature and the findings presented by
Charalambous (2011) the initial break rate of 0.07 break/km/year was applied for intermittent
supply.
The breakage growth rate in Shamir and Howard (1979) is reported to have a range
between 0.01 to 0.15 /year but a typical value is stated to be 0.05 breaks per year. Clark et al.
(1982) reported the value of to be 0.086 /year and according to Kleiner and Rajani (1999)
the values range from 0.003 to 0.134 breaks/ year for pit and spun cast-iron. In a similar
study done by Filion et al. (2004) on the water distribution in NYC, a breakage rate of
66
0.07/year was applied. In the present study a slightly different approach was adopted to
arrive at a typical growth rate value for the IS system. A relatively up-to-date data on
breakage rates in the Indian city of Bangalore was presented by WSP(2008). Bangalore was
chosen as the data collected from Bangalore Water Supply and Sewage Board (BWSSB) was
considered to be highly reliable according to WSP (2008) though reliable data on network
performance (specifically on pipe breaks) was supposedly maintained only from 2006.
By applying an initial break rate of 0.07/km/year (for IS) and with the knowledge of average
age of water mains, growth rate value were back-calculated using the model presented by
Shamir and Howard (1979) for which the average age of water mains were required. The age
of water mains were not available in the literature but Bangalore Water Supply and Sewage
Board (BWSSB(website), 2013) in their pipe replacement scheme have reported the supply
lines to be 50-60 years old. Pipes in Hyderabad (India) are 60-70 years old on an average and
oldest pipes are 100 years old (Mohanty et al. 2003). Also, Shivakumar (2013) reports that
pipes in Bangalore were laid from over 50 years ago. Hence average is age of water mains
were taken to be 50 years while calculating the annual breakage growth rate. The typical
value for IS systems was hence found to be 0.09 breaks/year.
The energy required to replace a unit length of pipe was found by simply multiplying the
energy required to fabricate a pipe of a particular diameter and thickness by a typical break
length.
(5.14)
where, = the average length of break (m), = fabrication energy per unit length (MJ/m)
Integrating the formula in equation (3.6.13), over a replacement cycle T gives the total
number of breaks in the pipe as
67
B =
(5.15)
where, B = Number of pipe breaks per replacement cycle, L = Length of pipes, x = dummy
variable.
Combining the above three equations (3.6.13,.14 &.15) and taking into account the
replacement cycle for each pipe-set considered the total energy required to repair pipes in the
system can be estimated ast:
(5.16)
Where, = Total energy required to repair pipes in the system (J), M = number of
replacement cycles throughout the planning period.
Data on typical length of pipe that would be replaced (repaired) during a break was not
readily available in the literature. Hence by assuming that repairing the pipes involves the
same activities as replacing them (Filion et al., 2004), a break length was calculated.
Pipe replacement would involve energy and material needed for soil excavation and
restoration, transportation of materials and operation of machinery. As relevant data on
energy consumption during the above activities is not available in the literature energy
involved during the fabrication process was multiplied by a factor of 2 (based on a similar
study by Filion et al., 2004). Shamir and Howard (1979) used a replacement cost of $164/m
and repair cost of $1000/break but these values do not account for the fact that cost varies
with pipe sizes. Walski and Pelliccia (1982) provide the required data on repair and
replacement costs for different pipe sizes.
68
5.1.3. Analysis of the results
The motive behind conducting this study was to establish concrete evidences that could
prove that maintaining an IS system is not energy and cost efficient. As most IS systems are
prevalent in developing countries which have recently found a need to improve the water
supply, retrieving relevant data was not straightforward. For instance Bangalore is expected
to have an up-to-date record of the network parameters but the BWSSB only started
maintaining a computerised database in 2006 (WSP, 2008). However with the available
datasets, studies and models it was able to establish a connection between service
intermittency, corrosion and water main breaks.
Fig. 5.2
The above Figure 3.6.4 compares the cost incurred in conveying water from the pumping
stations to the consumers in an intermittent and a continuous system. The increase in
corrosion levels in an IS system results in an increase in energy consumption at the pumping
station. The study provided some startling results by quantifying the disastrous effects of
intermittent supply. Pressurising water in an intermittent system seemed to be a costly affair.
0
0.5
1
1.5
2
2.5
3
3.5
10 20 40 50 70 100
Continuous Supply
Intermittent Supply
Pumping Cost Comparison (CS vs IS)
C
ost
($
B U
SD)
Replacement Period (Years)
69
For instance 72% more energy (and hence revenues) would be required to pump water in a
10-year old intermittent system compared to CS system of the same age. As the pipes in the
system get older, the gap between the energy needed to maintain the two systems also
increases. Hence, in a 50-year old system maintaining an intermittent supply would need
84% more energy. Increasing losses due to continued inaction is shown in Fig. 3.6.5. The
results however were very sensitive to the flow-rates applied. Even when the lower limit of
the range of flow-rates ratios (1.27) reported by Andey and Kelkar (2007) were applied,
significant differences in the energy requirements were observed. However, if the flow-rates
are assumed to be same for both the supplies, which is never the case with intermittent
supply, transmission energy requirement for intermittent supply would plummet and would
only be 11 % higher for a 10 year old system. This behavior is enough evidence to disprove
the commonly accepted fact that, intermittency and shorter supply duration are energy saving
strategies.
Fig. 5.3
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120
Percentage Loss
Per
cen
tage
Lo
ss (
Savi
ng)
(%
)
Replacement Period (Years)
70
The study reports another major drawback of IS system discussed earlier. Charalambous
(2007) reported a 300% increase in the number of breaks in a system that was operated
intermittently on a temporary basis. However nowhere else in the literature was a connection
between watermain breaks and intermittency quantified. Hence this study establishes an
important link between intermittency in supply and increasing watermain breaks. Cost
involved in repairing pipe breaks are compared and reported in Fig. 3.6.6. A log-scale was
used only to fit the values in a smaller range due to the exponential nature of the pipe-break
model used. A significant difference in the repair/replacement costs is reported. For instance
costs involved in repairing 20 and 40 year old mains in a IS system were 2.6 and 3.9 times
more, respectively. But if the replacement cycles within the 100 year planning period are
taken into account, costs involved for maintaining IS systems are over 6 times of what is
required for maintenance in a CS system. Though at replacement periods over 70 years the
pipe break values are purely theoretical, costs involved in pipe replacements are very high.
For a system with 40 year old mains it costs almost $2.8 Million (USD) to repair pipes is IS
system as against $0.73 Million (USD) that would be spent otherwise. This also means
hypothetically if a 40 year old system in Mumbai is operated continuously, with the available
funds of $2.8 Million, pipe repair plans could be delayed easily by over 10 years. As more
frequent system overhauls are required to maintain an IS system, it is definitely not a cost
effective option. Fig. 3.6.8 shows the expected saving through a successful migration to 24/7
supply.
71
Fig. 5.4
It is true that during pipe breaks considerable cost is involved repairing/replacing damaged
pipes but they pose a bigger problem by wasting large volumes of water. Also the net energy
expenditure during the replacement process is a serious cause of concern. Due to higher
frequency of breaks, energy requirement for maintenance (replacement/repair) of an IS
system can be several times the requirement for a CS system. With soaring gas and
electricity prices and shortage of supply meeting such requirement would mean incurring
more costs or cutting down on other important tasks. For instance repair of pipes in a 40 year
old system (such as the one consider in Mumbai) would require 3 times more energy if the
supply is intermittent.
0
1
2
3
4
5
6
7
8
9
10
10 20 40 50 70 100
Continuous Supply
Intermittent Supply
Cost of Repair (CS vs IS) C
ost
in $
USD
(Lo
g sc
ale)
Replacement Period (Years)
72
Fig. 5.5
Number of breaks and hence the cost involved drastically increases with the replacement
period, especially for intermittent supply. For instance if in a 20-year old system, the ratio of
the number of breaks (IS:CS) is around 2.5, in a 50-year old system the ratio would be
around 5. With the average age of watermains in many Indian cities being around 50-years it
could be imagined that the municipalities would be shelling out five times more of tax-payers
money to repair pipes, solely due to intermittent supply. In the considered scenario, to repair
pipes in a 50-year old IS system it would cost over a USD $11 million more.
0
2
4
6
8
10
0 20 40 60 80 100 120
Estimated Cost Saving (Pipe breaks)
Co
st (
$ U
SD)
(lo
g sc
ale)
Replacement Period (Years)
73
Fig. 5.6
Fig. 5.7
So far the effects of intermittency have been quantified in terms of direct costs involved or
energy required. But subsequent impacts such as water losses due to deteriorated system and
innumerable cases of inconvenience caused to the public during frequent pipe breaks or
0
2
4
6
8
10
12
14
10 20 40 50 70 100
Continuous Supply
Intermittent Supply
Pipe repair Energy Consumption Comparison (CS vs IS)
En
ergy
Co
nsu
mp
tio
n (
J) lo
g sc
ale)
Replacement Period (Years)
0
2
4
6
8
10
12
0 20 40 60 80 100 120
Ratio of Energy Requirement (IS:CS) (Replacement/Repair)
Rat
io (
IS:C
S)
Replacement Period (Years)
74
replacement processes need much more attention. Mumbai has the highest amount of water
loss in India which some reports claim to be around 40% to 50% (including pilferage)
(Sharma, 2011). According to Delhi Jal Board of 3000 MLD supplied to the City (New
Delhi) only 1700 MLD reaches consumers due to infrastructure constraints and other
problems (Bhatnagar, 2010).
5.2. Sample study on Bangalore City:
Bangalore produces 770 MLD of sewage (CPCB, 2009) out of which only 300 MLD is
treated (Shilpa, 2011). However even out of the 300 MLD treated only 9 MLD is being put
to some use (Shilpa, 2011) while the rest is just released into the city drains. Hence 98.83%
of the sewage is released into the valley and does not contribute to any water source.
Wastewater treatment in Toronto should be a model for Bangalore. The Ashbridges Bay
Wastewater Treatment Plant (ABTP), built in 1910, is Toronto's main wastewater treatment
facility and the largest such plant in Canada. It treats, on average, 9.5 m3.s
-1of wastewater
through a series of processes which includes screening, grit removal, primary treatment,
secondary treatment by a conventional activated sludge process, chemical phosphorus
removal and chlorine disinfection of treated effluent (Dziedzic et al., 2013). The projected
capacity of the plant is almost five times its current flow, though not all pumps can be
operated simultaneously due to power constraints and flooding concerns.
ABTP was chosen for comparison here because of its high COD removal rate of 97%
(Dziedzic et. Al., 2013). As COD determines the amount of organic pollutants in water
(surface or wastewater) it is a useful measure of water quality. The operation phase alone
75
which consumes around 500 TJ/year constitutes 92% of the Life-Cycle Energy consumption
at ABTP (Dziedzic et al., 2013).
At present much of Bangalore’s supply is from River Cauvery which is 90 kms from the city
and 500 m below it (Srinath, 2013). Hence even if fluid friction is not taken into account, to
just get the water from the river to the city 2600TJ of energy is being consumed. It is also
known that from its 312,000 borewells the City draws 300 MLD of water (Nataraj, 2013).
Average depth of the borewells in the city being 200m, over 200 TJ of energy is consumed
(mostly by residents) in pumping the groundwater annually. Hence to meet the demand,
tapping 1400 MLD of surface water and 300 MLD of groundwater, 2800 TJ/year of energy
is required.
If treating 821 MLD (299.59 MCM/year) of waste water in Toronto requires around 500 TJ
of energy per year, to employ the same level of treatment in Bangalore the net energy
required to operate the wastewater treatment plant should be around 470 TJ/year. Which is
any way is around 1/6th
of the present consumption (2763.23 TJ/year).
Table 4.1 (CPHEEO, 1999), shows the breakup of per-capita water consumption as defined
by the Ministry of Urban Development. Around 44% of per-capita needs are for non-potable
purposes. Thus if 50% of current freshwater consumption is offset through wastewater reuse,
800-1000 TJ/year of energy benefits could be achieved.
Per-Capita consumption
Bathing 55
Cooking 5
Drinking 5
Washing Clothes 20
76
Washing Utensils 10
Cleaning of house 10
Flushing 30
Total 135
Table 5.2
Wastewater treatment and reuse seems like the perfect solution to solve the water scarcity
issue but it is possible to achieve further energy benefits. For instance, a 10 MW biogas co-
generation plant was planned in Toronto to flare up the biogas released during the treatment
processes (Hamilton, 2010). Hence through the co-generation plant in ABTP, around 315
TJ/year of energy could be reused within the plant. If biogas co-generation is hence
implemented in Bangalore, 300 TJ/year of energy is put to use for operation of the plant, net
energy for treatment could be further reduced to 155 TJ/year (from 470 TJ/year).
5.3. Summary
So far it has been established that intermittent supply destroys the main purpose it was
employed in the first place. The more municipalities wait without planning a complete
migration towards employing a continuous supply system, the harder it gets to manage as the
system would further deteriorate and more water will flow out through leaks and breaks
without reaching the consumers. The study thus quantifies the effect of a continued inaction.
The systems are ageing and the infrastructure has deteriorated faster than it should. As it has
reached a point where most pipes have to be replaced this would be the best time to
implement strict measures and plan for a complete migration. The net energy and cost benefit
achieved from maintaining a continuous supply could be used as investments to implement
wastewater reuse in phases. For instance by assuming that 100% of the meters in Bangalore
are metered, with the current rates USD $52 million would be recovered but with the revised
77
rates proposed USD $293 million in revenue could be earned. The fivefold increase in the
revenues would hence assist in a successful migration to 24-hour supply and implementation
of wastewater reuse. The only concern with the implementation of wastewater recycling is
that separate water lines need to be installed for the freshwater supply for potable purposes
which would need massive initial investments. However as the present infrastructure has
deteriorated pipe replacements are anyhow necessary. Hence it would be an ideal time to
invest in additional infrastructure and simultaneously implement measures to implement 24-
hour supply successfully. Wastewater reuse can also be implemented in phases.
One of the most challenging and time consuming step in the above estimations was
collecting and estimating the actual data such as water consumption, pipe characteristics,
non-revenue water, number of borewells and pipe breaks. If accurate data is not maintained
then the system cannot be modelled (both physical and computer based) for better
management and maintenance. For instance Bangalore started maintaining data on pipe
breaks from the year 2006. Estimated data based on previously developed mathematical
models could be good for an analysis of the existing condition similar to the one presented
here but more accurate field values would be needed for planning and implementation.
78
CHAPTER 6
Conclusion and Future Avenues of Research
This thesis provides enough evidence to prove the disastrous effects of Intermittent Water
Supply System on the consumers and on the associated distribution infrastructure. For the
following reasons a complete migration to a 24 hour supply is highly recommended. Note
that although these points are framed particularly for India, the problems mentioned are as
broad as intermittent supplies themselves.
1) The IS system can never be a solution to water scarcity, as it is thought to be. In fact,
the truth is higher that the higher the degree of intermittency the higher is the
tendency of the consumers to collect and hoard more water, thus increasing their
consumption. Moreover, intermittency often leads to much higher rates of water loss
from leakage and breaks. It seems perhaps logical to expect that the per capita
consumption will be less in water scarce situation. Ironically, this is often not the
case: when the supply is intermittent per capita consumption is higher.
2) Unequal distribution of water to consumers is unacceptable. It has brought conflict
and tensions between communities in India as the consumers simply cannot accept
that someone else is getting a better water supply when everyone pays the same price.
3) Today the biggest challenge in rural India is intermittency in supply. To cope the
rationing the direct and indirect costs incurred by the consumers is more than what
consumers in the developed world would for a 24 hour supply. This is seriously
affecting the economy of developing countries like India. Young boys and girls who
should be spending time at school or working for hourly wages are sacrificing their
time and also the best part of their lives just to secure water for their families.
79
4) As mentioned earlier, urban India attempts to cope with intermittent systems either
through private borewells or tanks. This unfair edge given to some sets of the
population creates a further rift within communities. It is gives an incentive for
people to take advantage of the system. For instance, landlords are taking advantage
of intermittent supply by charging very high rent if tenants require continuous supply
through private borewells. An unfair increase in property rates is a common reaction
in urban India which is also a result of unequal distribution of nature’s resource.
5) A huge amount of water is being lost through leaky pipes, breaks and bursts. IS
system not only stifles the consumers’ everyday activities, but is rapidly destroying
the existing physical systems. With the current shortage of revenues, coping with
more frequent replacement and repairs is a distant dream which means losses
continue to exist with municipalities doing nothing about it. When it is no longer
feasible to supply water through distribution lines, water trucks and tanks would be
used for water distribution.
6) Water quality deterioration occurs at different levels during intermittent supply and
this extends right from intrusions into distribution mains during negative pressure
regimes to arsenic contamination associated with use of marginal groundwater. Often
consumers are not aware of the repercussions of consuming contaminated water or
they are not aware about the contamination. Serious health related issues arising out
of such negligence are common in most developing countries with intermittent water
supply.
7) As if these problems were not sufficient, intermittent system is a dangerous option
during fire events. Not only are the available pressures unfit for firefighting but often
80
during fire accidents the particular region may not even be receiving water at that
moment! Transporting water through via trucks through the congested roads means
delays response and leads to more destruction and losses during fire accidents.
Hence as intermittent systems do not serve any purpose what-so-ever, the municipalities
should urgently and decisively plan for a complete migration to a 24 hour supply.
Some possible future works that would further optimize water distribution are as follows,
1) Maintaining and keeping better records of water use, infrastructure system
investments and system performance. It is very hard to plan well is data is inadequate,
lacking, uncertain or poorly organized.
2) Droplet size analysis in developing water efficient fire suppression systems
3) Creating a framework to assist the formation of water zones to successfully
implement water charges based on the household income
4) Region-wise groundwater studies to implement appropriate reclamation methods.
5) Developing cost efficient wastewater treatment strategies
6) Developing interactive water usage tracking method for consumers where the
household water usage can be monitored on an hourly basis. For example, an
interactive Smartphone application could help users track their water usage from any
location which would help to stop excess usage and plug leaks instantly.
7) Performing Life-Cycle Energy (& Cost) Analysis of using Biogas generated from
wastewater treatment to desalinate sea water. For instance a model could be
developed to determine the volume of seawater that can be desalinated in coastal
cities (such as water starved Chennai) with only biogas generated form wastewater
treatment from the city.
81
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