www.smartwww.in | OCT 2019 33

LEADERS FROM

DIFFERENT SEGMENTS OF WATER

COMMUNITY IN INDIA

SHARE THEIR THOUGHTS ON

THE ‘AGENDA FOR THE

INDIAN WATER SECTOR’ IN

THIS SPECIAL ANNIVERSARY

EDITION.

W AT E R L E A D E R S

Ce l e b r a t i n gSM

ART WATER & WASTE WORLDCOVER STORY

As part of the effort to provide a healthy environment to her citizens, India is taking giant

steps to clean the waters of India (such as rivers, lakes, etc.) and to provide sanitation. In November 2015, to reduce water pollution, Central Pollution Control Board (CPCB) has issued strict effluent limits for the discharge of treated sewage to waters of India. However, the limits were relaxed by CPCP in October 2017. But the National Green Tribunal (NGT) upheld the 2015 limits in April 2019 and made some changes. The final discharge limits are provided in Table 1.

W AT E R L E A D E R S

COVER STORY

To improve on sanitation, numerous greenfield Sewage Treatment Plants (STPs) are being built to treat untreated sewage while the existing STPs are being upgraded to meet the new discharge limits. To meet the strict effluent discharge limits, state-of-the-art technologies need to be installed in the STPs. In addition, to conserve water, the regulatory authorities are also making an effort to bring in a policy for recycling and reuse of treated sewage. By issuing strict discharge norms (by CPCB) which was later upheld by NGT, both CPCB and NGT have done a tremendous job requiring municipalities to clean sewage to high standards before discharge. This has and will go a long way in cleaning the waters of India and improve the health of the environment. However, to further improve the health of the environment, it is high time CPCB focus on sewage

sludge management and disposal. Sludge contains pathogens and may cause diseases if not properly treated, managed and disposed off. With no regulation in-place, the current practice of sludge management in India is unhealthy and presents a health hazard. Farmers (who receive the sludge from the STPs) and others are exposed to pathogens resulting in various diseases. In addition, crops grown from the land where the sludge with pathogen is applied, present health hazards to the public at large who consume those crops. In this regard, CPCB is recommended to come

up with a sewage sludge rule immediately or adopt United

“SWACHH BHARAT SWASTH BHARAT” (CLEAN INDIA HEALTHY INDIA) TO ENSURE HEALTHY LIFE OF CITIZENS THROUGH CLEANLINESS To further improve the health of the environment, it is high time we focus on sewage sludge management and disposal.DR. INDRA N. MITRA, DIRECTOR - TECHNOLOGY & PROJECT DEVELOPMENT CAMBI INDIA

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www.smartwww.in | OCT 2019 43

Ce l e b r a t i n g

States Environmental Protection Agency (EPA) Biosolids Rule in 40 Code of Federal Regulation (CFR) Part 503 (hereafter referred to as EPA 503 Biosolids Rule). It may be appropriate to rename and extend the “Swachh Bharat” (Clean India) Program to “Swachh Bharat Swasth Bharat” (Clean India Healthy India) to ensure a healthy life of citizens through cleanliness.

MY 5-POINT AGENDA FOR THE WATER SECTOR1) TechnologyWastewater treatment is a highly complex field and as effluent limits become stricter, the focus will be on technology. Technology and process is the fundamental building block of wastewater treatment based on which other disciplines work. It is very important to have genuine wastewater treatment experts for each technology who will not only have strong knowledge of the technology but also be knowledgeable of

recent developments in the specific field. Projects should require technology specialists for various critical processes particularly for biological treatment of wastewater and sludge. Companies should have/ develop a separate technology center/ department offering to its employees a career as a technologist. Technology and process will make or break a project and that is why the enormous emphasis is given to technology in developed countries. Proper selection and application of right technology reduces capital and operating costs of STPs, enhances the chances of winning various STP projects with minimum or no risk, simplifies plant operation, enhances process efficiency and performance, and ensures that the plant meets its effluent limits all time.

2) Sewage Sludge RegulationsCurrently, India does not have

any regulations for the disposal of sewage sludge. Presently, the sludge generated in STPs are: (i) Thickened and dewatered or (ii) Thickened, digested and dewatered, and then (i) Disposed off to landfill or (ii) Given to farmers for agriculture - both of which are not desirable in today’s world. Landfill uses up space and land and requires further treatment including operation and monitoring which add to costs. Sludge generated from STPs contains pathogens that affect the health of the farmers and others who are exposed to it and the public at large who consume the crops because crops grown from the land where the sludge is applied may contain pathogens. It is recommended that CPCB should immediately come up with sludge regulations or adopt EPA 503 Biosolids Rule. This rule is used in the USA, and in many other countries. EPA 503 Biosolids Rule establishes criteria for various modes of disposal of sludge - land application, surface

pH s.u 5.5 - 9.0 5.5 - 9.0 5.5 - 9.0 5.5 - 9.0

BOD mg/L 10 20 30 30

TSS mg/L 20 30 50 50

COD mg/L 50 100 150 150

Total Nitrogen mg/L 10 15 - -

Total Phosphorus mg/L 1.0 1.0 1.0 -

Fecal Coliform MPN/100 mL 230 1,000 10,000 10,000

Parameter Unit Mega & Metro Cities

Deep Marine Outfall

Class 1 Cities Others

Table 1

Sludge Treatment Treatment Status in India

Recommended Application1 Current Status CommentsSludge Produced

Table 2 (Based on EPA 503 Biosol ids Rule)

Thickening + Dewatering

In most STPs

Thickening + Anaerobic Digestion+ Dewatering

Only in a few select large STPs

None

High level of pathogens, lower quality than Class B

Class B - contains some pathogens

Class A with no pathogens

Landfill

Landfill or land apply with a lot of restrictions

Land apply with no restrictions, fertilizer

Landfill or land applied by farmers

Landfill or land applied by farmers

Not applicable

Must not be land applied

Must not be land applied without restrictionsRecommended for present and future sludge treatment and disposal

Thickening + Pathogen Reduction +Anaerobic Digestion+ Dewatering

disposal, and incineration. Land application is the preferred method of disposal in most cases as it is usually the least expensive of all alternatives and has the least environmental impacts. For land application where the sludge is used as a fertilizer, no additional land is required and operational cost is lowest. According to the EPA 503 Biosolids Rule, following are the criteria which the sludge must meet for land application:

a. Concentration Limit of 10 Trace Heavy MetalsFor land application, all biosolids must meet the trace heavy metals concentration limit specified in the rule.

b. Vector Attraction ReductionFor vector (such as flies, mosquitoes and other disease-causing organisms) attraction reduction, the sludge must meet one of the 10 options listed in the rule. One such option is to achieve volatile solids reduction by a minimum of 38% before disposal. Typically anaerobic digesters treating combined primary and secondary sludge achieve 45-50% volatile solids reduction at 15-20 days Solids Retention Time (SRT).

c. Pathogen ReductionThose that meet the metals and vector reduction criteria must meet Class A or Class B biosolids criteria for pathogen reduction specified in the rule for land application. Class A biosolids require reduction of pathogen level to below detectable levels (i.e., Fecal Coliform 1,000 MPN/gm of dry solids) compared to Class B requirement of pathogen reduction to 2,000,000 MPN/gm of dry solids. Class A biosolids allow unrestricted use of biosolids and can be sold/ used as a fertilizer or soil amendment. It can be applied

COVER STORY WATER LEADERS

44 OCT 2019 | SMART WATER & WASTE WORLD

at home lawns, public parks, etc. Conversion of sludge into Class A is converting waste to worth. On the other hand, Class B biosolids need to be landfilled or land applied with a lot of restrictions (and must be away from public contact for at least a few years). Table 2 shows the proposed and current status of various options for treatment of sludge from clarifiers in STPs and their ultimate disposal.

3) Requirement of Class A BiosolidsIndia and the whole world are moving towards a circular economy and there is a push to recover resources from waste. As a result, many STPs in many parts of the world are changing their names to Water Resource Recovery Facility (WRRF). So, now the STPs are looking at technologies to convert sludge to energy, produce Class A biosolids which can be used as a fertilizer and increase the solid content of sludge (> 30% solids) to reduce the volume of sludge to be disposed off. It may serve as a model for smart cities also. It is high time that all STPs, particularly the large and medium-sized plants adopt the requirement of anaerobic digestion along with Class A biosolids and more than 30% solids in the final solid cake in tenders to promote a circular economy. Anaerobic digestion converts sludge to energy and Class A biosolids can be used as a fertilizer. Most common technologies used for the production of Class A biosolids are Pasteurization, Thermophilic popularly known as Temperature Phased Anaerobic Digester (TPAD) and Thermal Hydrolysis (THP). Some of the plants employing Pasteurization and TPAD have shown Reactivation and Regrowth (R&R) of pathogens in sludge which violates Class A biosolid requirement. Therefore, proper risk evaluation must be done before selecting Pasteurization or TPAD. On the other hand, THP is widely used in producing Class A biosolid and is the most popular of all technologies. No R&R has been reported by any

THP installations. It is the most reliable and robust process with a pay-back period of only 5-7 years when upgraded from the conventional system (producing Class B biosolids). More than 80% installations of THP worldwide are supplied by Cambi. Cambi is an advanced anaerobic technology that uses the THP process. It is essentially a pre-treatment technology placed before anaerobic digester. In a normal anaerobic digester, the sludge is first hydrolyzed and solubilized by the biomass before it can be consumed by the biomass. This hydrolyzing and solubilization is the rate-limiting step and can even take days. In the Cambi process, this process is done by physical means (instead of biological) by externally “pressure cooking” the sludge before the digester. It is a two-step pre-treatment process where the sludge is first mixed with steam under high temperature and pressure followed by sudden expansion (steam explosion) resulting in disintegration, hydrolyzation, and solubilization of sludge. The sludge so produced is more biodegradable, with lower viscosity and sterilized. This also changes the rheology and physical characteristics of the sludge. This results in 25-50% higher volatile solids destruction and 25-50% higher biogas production in the digester. It also allows higher digester loading which reduces the digester volume by over 60%. It improves the dewaterability of sludge producing sludge cake of more than 30% solids. This reduces the volume of sludge to be disposed off by over 40%. It also reduces odor and saves space. The sludge produced is Class A biosolids and can be sold/ disposed off as fertilizer. In addition, Cambi reduces carbon footprint significantly.

4) Design and Tender RequirementRight selection and design of STPs are crucial for the right estimation of costs and performance of STPs to meet strict discharge limits. So, as mentioned earlier, the role of the knowledgeable technologist

is the key to the selection of technology and design. Both consultants and EPC companies must employ experts for each process. Consultants preparing the tender for the design, construction and operation must design the entire STP correctly and put in all specifications. To make the design compact and to reduce costs, the following recommendations are made which can be included in the tender:• Raw sewage data including flows and pollutant concentrations must be actual and not taken from any standard textbooks/ literature as sewage characteristics vary from place to place. It is often found that the actual data is vastly different from those provided for design. For example, raw influent design BOD provided may be 250 mg/L when in real data reflects it is less than 150 mg/L. This may lead to unnecessarily overdesigning the system resulting in higher costs and faulty design.• Flows and concentrations must be chosen based on last 5 year data which includes all seasons.• For better design, the spectrum of raw sewage parameter must be increased and include the following: BOD, soluble BOD, COD, soluble COD, TSS, volatile solids, non-degradable volatile solids, settleable solids, TKN, total nitrogen, total phosphorus, soluble phosphorus, pH, min and max temperature, alkalinity, and other additional parameters.• In places of high rainfall, provision may be allowed to bypass the biological process during stormwater events beyond a certain flow so that the biological system does not get upset.• Offline equalization tank before the biological system may be suggested to protect the biological system from upsets.• A pilot may be recommended to demonstrate the process and also to fine-tune the design parameters. This will ensure a robust design with a consequent reduction in costs.• Most of the tenders with anaerobic digesters require Combined Heat and Power (CHP)

for production of electricity from biogas generated from anaerobic digestion of sludge. It is recommended that another option be evaluated where the CO2 in biogas is scrubbed and the pure methane is produced and supplied to run buses, autos, etc (run on CNG).• For sludge treatment and disposal, EPA 503 Biosolids Rule must be followed. Currently, very few STPs have anaerobic digesters and produce sludge which has very high pathogen levels. Anaerobic digesters must be included in STPs (beyond a certain flow) to ensure, at a minimum, Class B biosolids are produced. Proper checks and monitoring requirements (in accordance with EPA 503 Biosolids Rule) must be incorporated in the tender to protect the health of the farmers and public at large.• Given the paucity of landfill sites, monitoring the requirement for Class B biosolids, high sludge transportation and disposal costs, it is recommended that the tenders for medium to large STPs adopt the requirement of anaerobic digestion along with Class A biosolids and more than 30% solids in the final solid cake. This will ensure a circular economy where sludge can be used to produce energy and fertilizer and sold. This concept may serve as a model for smart cities also.• Sludge centers may be constructed where dewatered sludge from several small STPs can be combined at a central location for processing of sludge and production of energy with Class A biosolids.• Other degradable wastes, such as food and vegetable waste may be mixed with sludge in sludge centers for food waste treatment, enhanced energy generation and production of Class A biosolids.• As India is a signatory to climate change, tenders may include carbon footprint as one of the criteria for selection of technologies and estimate the total carbon footprint of the project.

5) Industrial Wastewater and Sludge Treatment

COVER STORY WATER LEADERS

Ce l e b r a t i n g

To minimize water pollution from industrial sources and to conserve water, CPCB and local authorities are requiring Zero Liquid Discharge (ZLD) for many industries. To achieve ZLD, many industries are using Reverse Osmosis (RO) process. Holistically, the use of RO process is not an environment-friendly process as it requires electricity, produces chemical waste and membrane waste and generates reject wastewater which is hard to dispose off. It is a classic case of transforming environmental pollution from one media to another. Innovative solutions are encouraged and found to achieve the desired goal at reduced environmental hazards. It is recommended that the use of RO processes be limited to places requiring high-quality water from treated wastewater.

To improve on sanitation,

numerous greenfield Sewage Treatment Plants (STPs) are being built to treat untreated sewage while the existing STPs are being upgraded to meet the new discharge limits.

All tenders for industrial Effluent Treatment Plants (ETPs) must include pilot studies. It should be made mandatory. As India is a signatory to climate change, tenders may include carbon footprint as one of the criteria for selection of technologies and estimate the total carbon footprint of the project. Sludges from ETPs are treated as hazardous waste and are generally disposed off in a landfill. This takes up space and land, consumption of which goes on increasing. It is recommended that the regulators promote environment-friendly sustainable solutions for this sector. For example, in certain wastewaters containing low metals concentrations, sludge from the biological treatment section of ETP (waste activated sludge) which are organic, can be converted to energy and fertilizer using various technologies such as Cambi and anaerobic digester. This will also increase the final solids content of sludge and reduce the volume of sludge to be disposed off. This will save landfill space.

ABOUT THE AUTHOR

Dr. Indra N. Mitra has 24 years of domestic and international wastewater work experience (12 years in India and 12 years in the USA) in Group Management, Business Development, Proposals, Technology & Process, Design and Engineering with EPC, Consulting and Technology and Equipment Supplier Companies in water & wastewater. He is an International Wastewater and Sludge Treatment Expert and is recognized as a “Who’s Who” in Water & Wastewater by American Academy of Environmental Engineers. He is a registered Professional Engineer (PE) of the State of Virginia, USA.Currently, Dr. Mitra is working as Director for Cambi, India. Previously Dr. Mitra has worked in various capacities as Director/ Vice-President heading Technology/ Business Development / Proposals/ Design and Engineering in leading water and wastewater companies such as World Water Works (USA), NJS Consultants (Japan), Ion Exchange Ltd, SMS Ltd and Praj Industries in India. He started the India operation of World Water Works (USA) and headed the India and Asia operations. In the USA, he worked for CH2M Hill (Jacobs) and Tetra Tech.Dr. Mitra has completed B.Tech in Chemical Engineering from IIT, Kharagpur, India, MS in Environmental Engineering from Vanderbilt University, Tennessee, USA, Ph.D in Environmental Engineering from Lehigh University, Pennsylvania, USA and MBA in Finance from Virginia Tech, Virginia, USA. He has authored several books and papers and is a member/advisor to several leading water and wastewater associations and organizations.