0 Training report

A

REPORT ON

INDUSTRIAL TRAINING

AT

NARMADA CLEAN TECH LTD (NCTL)

ANKLESHWAR

Submitted by:

Sagar Divetiya

Enroll no. 110990135013

Academic year 2014- 2015

Guided by (Industry):

Mr. Dharmesh D. Shah

Senior manager

NCTL, Ankleshwar

Guided by (College):

Mrs. Pratibha Gautam

Assistant professor (DEST)

SRICT, Vataria.

Submitted to:

Mr. Manoj Kumar

Head of Department

Department of Environmental Science & Technology (DEST)

Shroff S. R. Rotary Institute of Chemical Technology

Vataria, Ankleshwar, Gujarat

A c k n o w l e d g e m e n t P a g e | 2

Acknowledgement

Success of any training depends on the dedication and sincere hard work. It also requires some

essential like motivation, guidelines, encouragement, positive attitude, good observation and

time.

We would like to express our gratitude to Mr. K. R. Desai (C.E.O., NCTL) and Mr.

Paresh T. Sarvan (D.G.M.,NCTL) for giving us the opportunity to pursue the engineering

training at Narmada clean technology limited as a partial fulfilment of the requirement for the

degree of Bachelor of Engineering (Environmental Science and Technology).

We would like to thank Mr. Dharmesh D. Shah, (Sr. manager NCTL) without whom

the project would not have literally seen light of the day. He has given us a taste of real flavor

of engineering and industrial environment. Besides our lacking basic knowledge and skills, he

made it possible for us to polish our some of the weaknesses and directed us to minimize the

gap between theory and practical knowledge and skills. He has shared his knowledge and

experiences to enhance our understanding about actual scenarios and practices carried out in

industries to sustain in this competitive and ever-changing world. He has given us tasks in form

of question to put our brain on work that has created a huge impact on our brainstorming

capabilities. He has answered our reasonable question very precisely.

Mr. Pratik Patel (executive, monitoring & process audit, NCTL) being our mentor and

instructor helped and guided us in various ways to carry out our industrial training. He provided

us sufficient information about NCTL.

We would also like to mention that Mr. Shaktisinh Maharaul (QCD Executive, NCTL)

was the one who has helped and guided us in understanding facts, data and quality of

wastewater. He has induced us to perform analysis of effluent samples at NCTL laboratory.

We would like to thank Mrs. Megha Patel as well as all the chemist and analyst at NCTL

Mr. Girish J. Chavda, Mr. Manish h. Gandhi, Mr. Rajesh V. Patel, Mr. Prakash P. Patel, Mr.

Ajay P. Patel and Mr. Gaurang A. Patel for their extraordinary support and for guiding us for

analysis of wastewater samples.

Mr. N. J. Nathani explained us the plant and gave us troubleshooting problems to

understand the operation control of the plant. Mr. Sachin Bhatt explained us the operation of

newly established filter press for sludge dewatering.

We are thankful to each executives, technicians, operators of the facility for their help,

extraordinary support and kindness.

We are also thanking full to our Dr. Snehal Lokhandwala (Training and Placement In

charge, HOD of MSH dept.), Mr. Manoj Kumar (HOD of EST Dept.) and Mrs. Pratibha

Gautam (EST Dept.) from Shroff S.R. Rotary institute of chemical technology by whom we

were inspired to complete the industrial training for one month.

Finally we apologize all other unnamed who helped us in various ways to have a good

training.

A b s t r a c t P a g e | 3

Abstract

Common Effluent Treatment Plants (CETP) has become necessary for managing and treating

industrial wastewater in environmentally sound manner. Narmada clean tech ltd (NCTL) is a

type of CETP called Final Effluent Treatment Plant (FETP) since the industrial wastewater of

Ankleshwar, Panoli and Jaghadia is treated just before discharging into the ocean at the FETP.

It is a great experience to get trained under such big unit. FETP, NCTL is the place to have a

taste of conventional treatment methods.

The prime purpose of this training was to identify and understand the real life practical

scenarios. Purpose was fulfilled up to great extent. Ultimately our knowledge and skills are

improved. Each day some task are given to practically understand the plant. It is an

extraordinary opportunity to experience practical industrial environment, work discipline, team

work, time management, quality controlling and to obtain a clear understanding of the

theoretical knowledge which was gathered at the university.

Industrial training report is prepared to present the knowledge gained throughout the

training. The report precisely represents the major tasks given and their reasonable conclusions.

The report elucidates the real practical experience and deviation from ideal theories. Reader

may find it comprehensive by first view but the report consists of concise conclusions of all

the witnessed conditions.

In one month training, approach taken by guide was very distinctive. So the module

followed was extremely helpful for understanding the technical as well as administrative

aspects of industry. The knowledge gain will be invaluable in near future.

The conventional technologies like Activated sludge process has been understood

thoroughly. But the care had taken to deliver the sufficient knowledge of fields other than

environment. As an environmental technologist FETP is the heaven. Basic design calculations

and troubleshooting has given very firm background for further education and even for career.

I n d e x P a g e | 4

Index

Sections

1. Introduction to CETPs

2. NCTL overview

3. Process description

4. Environmental management at NCTL

5. Safety at NCTL

6. Equipment used

7. Analytical laboratory at NCTL

7.1 Overview

7.2 List of analytical instruments

7.3 Analysis of parameters

8. Tasks performed

8.1 On field task

8.2 Off field literary task

8.3 Lab task

9. Learning outcomes

10. Enhancements at NCTL

11. References

12. Conclusion

Page

6

8

9

13

14

15

18

23

34

36

38

39

I n d e x P a g e | 5

Table Index

Tables

Table-1: Inlet measured parameters at NCTL

Table-2: Places at NCTL where lighting arrestors are installed

Table-3: Comparison between pre-primary, primary, secondary clarifiers

Table-4: Levels of wastewater treatment

Page

10

14

24

25

Figure Index

Figures

Figure-1: NCTL Process Flow Diagram

Figure-2: Pre-Primary Clarifier

Figure-3: Surface Aspirators

Figure-4: Surface Aspirators working

Figure-5: Decanter

Figure-6: Decanter working

Figure-7: Filter press

Figure-8: Sludge dewatered cake

Figure-9: Filter press working

Figure-10: Ammonical Nitrogen analysis

Figure-11: Three phases of microbial growth

Page

9

11

15

15

15

15

16

16

16

20

32

1 | I n t r o d u c t i o n t o C E T P s P a g e | 6

1. Introduction to Common Effluent Treatment Pants (CETPs)

1.1 Concept of CETP

Common Effluent Treatment Plant is the concept of treating effluents by means of a collective

effort mainly for a cluster of small scale industrial units. This concept is similar to the concept

of Municipal Corporation treating sewage of all the individual houses.

CETP was promoted by MoEF (Ministry of Environment and Forest) in 1984 to treat

waste water from small and medium scale industries sector (SMIs). First CETP was constructed

in 1985 in Jeedimelta near Hyderabad. CETP was followed by other states in TN, MP, Gujarat,

and Maharastra. A bulk environmental pollution is caused by SMIs small scale industries

policy has no thought for environmental planning. For the effluent from SSIs the concept of

CETP was introduced. The MOEF has instructed the SPCB (State Pollution Control Board) to

established CETP in different industrial estates in respective states. It said that the central will

provide up to 25% of the total cost of CETP and the remaining should be contributed by state

Govt. and industries.

1.2 Need of CETP

To minimize environmental pollution due to the small and medium scale industries.

Cleaner production technologies

Waste minimization methods and centers.

Collective treatment at a centralized facility, called as the CETP is a viable treatment

solution.

1.3 Advantages of CETP

Facilitates ‘economy of scale’ in waste treatment

Addresses the ‘lack of space’ issue

Homogenization of wastewater

Better hydraulic stability

Professional control

Facilitates small scale units

Eliminates multiple discharges

Recycling and reuse

Organization of treated effluent and sludge disposal

1 | I n t r o d u c t i o n t o C E T P s P a g e | 7

1.4 Problems and constraints

Consistency in operation

lack of access to

o capital investments

o working capitals

o specialized technical skills

inconsistent effluent quality from member industries

improper management of treatment units

Varied nature and scale of the industries, along with the addition of industries in a

haphazard manner, without proper planning

No provision to tackle the fluctuations in the pollution load and quantities, at

individual member industries no separate treatment units to deal with hazardous and

toxic effluents, etc.

1.5 Influencing factors in Planning of CETPs

Categories of effluent generating member industries

Qualitative/quantitative fluctuations of effluent (equalization/ homogenization

/modules)

Pre‐treatment requirements

Segregation of effluent streams at individual member industry

Collection and monitoring mechanism

Treatability choice of technology and bio degradability, interferences

Mode of disposal

Charging system

1.6 General Process of Common Effluent Treatment:

Preliminary treatment - It involves a number of unit processes to eliminate

undesirable characteristics of wastewater. Processes include use of screen, grit

chambers for removal of sand and large particles, communitors for grinding of

coarse solids, pre-aeration for odour control and removal of oil and grease.

Primary treatment- It involves removal of settable solids prior to biological

treatment. The general treatment units include: flash mixer + Flocculator +

sedimentation.

Secondary treatment- It involves purification of wastewater primarily with

dissolved organic matter by microbial action. A number of processes are available

but the ones that are mainly used are anaerobic and /or aerobic treatment methods.

Tertiary treatment - This mainly includes physical and chemical treatment processes

that can be used after the biological treatment to meet the treatment objectives.

2 | N C T L O v e r v i e w P a g e | 8

2. NCTL Overview

Narmada Clean Tech Ltd. (NCTL) formerly known as Bharuch Eco Aqua Infrastructure Ltd.

(BEAIL) is a company, subsidiary of Gujarat Industrial Development Corporation (GIDC) and

jointly promoted by Member Industries of Ankleshwar, Jhagadia and Panoli Industrial Estates.

The objective is to receive the industrial effluent from Ankleshwar, Jhagadia & Panoli

Industrial Estates and to polish it at Final Effluent Treatment Plant (FETP) up to marine

standards and then to convey deep into the sea. VC & MD - GIDC is the Chairman of NCTL.

Ever since the issues of Environment Protection become a priority agenda across the

world, Indian government & Gujarat government has joined the international community in its

commitment towards Environment Protection Program. The priority accorded to control of

Environmental pollution is evident from the number of pollution control acts enacted along

with rules and regulations. Keeping the spirit and intent of these policies, implementation at

ground level is the major challenge.

Prior to commencement of this project, treated effluent from three industrial estates

were disposing off into a natural creek namely Amlakhadi leading to Narmada Estuary.

Objection was raised by local population and NGOs against disposal of effluent and

subsequently High court has intervened and directed to stop the disposal of effluent into

Amlakhadi. Afterwards in high level Committee Meeting chaired by ACS, it was decided to

treat effluent up to marine standard and to release into Gulf of Khambhat beyond Narmada

Estuarine Zone. NCTL was set up to honor the directives given by the High Court.

The Final Effluent Treatment Plant (FETP) is spread over more than 3, 00,000 sq.

meters of land, has treatment capacity of 75,000 m3 per day. More than 38000 trees are planted

to cover bare land. Facility was commissioned in December, 2006 at the cost of 131 crores to

treat 40000 m3 per day of effluent using conventional biological treatment. Facility was

enhanced by 20000 m3 per day at an additional cost of 32 crores taking total project cost to 167

crores. The continual improvement projects includes addition of preprimary clarifies to reduce

carryover of suspended solids, installation of additional decanters for solid removal, installation

of culture tank for sustainable development of microbes, etc. Technical & Economic viability

of other technologies to reduce COD namely Electro coagulation, ozonation, Ultrasonic sound,

RO, etc. are in progress.

NCTL has two departments for Sampling and Analysis:

1. Monitoring Department

2. Analysis Department

The Monitoring Department Collects Samples from Member industries. Coding of

these Samples is done so that the Analysis Department, while Analysis, could not identify the

sample. After Analysis, Samples are decoded. According to the parameters of the industries,

they are charged. They also match the readings of inlet to the plant with the outlet of the

industries (i.e. differences experienced within the path from industries to the plant) for checking

purpose.

3 | P r o c e s s D e s c r i p t i o n P a g e | 9

3. Process Description

NCTL has a Final Effluent Treatment Plant which consists of the neutralization system,

clarification system, aeration system for biological oxidation of organic matter, guard pond &

pumping system after the effluent is being treated to some other Effluent treatment Plant.

3.1 Process Flow Diagram of NCTL

Figure-1: NCTL Process Flow Diagram

3.2 Inlet chamber

Effluent from three industrial estates Ankleshwar, Panoli and Jhagadia comes to NCTL for

their final discharge to sea. Here two parameters are kept under consideration, pH and


temperature of the Effluent. Three different Flow Meters have been installed at NCTL for

continuous Flow measurement into the plant.

Table-1: Inlet measured parameters at NCTL

Parameters Ankleshwar Panoli Jhagadia

Flow (MLD) 41.1 6.5 7.4

pH 6.59 7.32 6.94

Temperature (˚c) 28 33.6 25

(These are the parameters measured on date: 10/06/2014)

Acidic Effluent can cause harm to the plant in form of corrosiveness and other factors.

This, it is tried to keep the pH in almost Neutral condition (pH: 7-8). Provisions for

neutralization are Lime dosing and caustic treatment. Usually Lime dosing is done to the

Effluent, but in cases of lower pH or highly acidic Effluent, Caustic treatment is applied for

immediate pH control.

3.3 Screens

The pipelines coming from the three Estates Ankleshwar, Panoli and Jhagadia are open

pipelines. There are chances of larger particles to flow to the plant with the flow of the effluent.

To prevent these particles from entering the clarifiers, Screens are installed after the Inlet

Chamber.

3.4 Flash mixture

The Effluent after passing through the Screens is free of larger foreign particles which then

reach the Flash Mixture. Here the effluent received is divided and passed to the four Pre-

Primary Clarifiers.

3.5 Flocculator

There is one flocculation Tank for each pre-primary clarifier. The effluent passes from Flash

Mixture to the pre-primary clarifier via flocculator. Here addition of coagulant/ flocculent is

done. At NCTL, Poly Electrolyte is used to serve this purpose.

3.6 Pre-primary clarifier

The inlet of a pre-primary Clarifier is from the top as shown in the figure below. Pre-primary

circular clarifiers are designed to receive raw wastewater after it has been pre-screened to

remove large objects and grit. The sludge settled at the bottom of the pre-primary clarifier is

pumped out at regular intervals and sent to sludge thickener and then to the decanter or filter

press for de-watering purpose.


Figure-2: Pre-Primary Clarifier

3.7 Equalization Tank

There are two Equalization tank at NCTL each of Flow rate 20MLD and Capacity 12512 KL.

It is required to make all the parameters uniform throughout the effluent and to maintain the

Sock load. In the previous Plant, before the Expansion up to 60 MLD from 40 MLD, the

Equalization tank served the purpose of removal of some parts of Suspended Solids by

overflow from one tank to another via rectangular weirs. The leachate generated as a result of

dewatering is sent to the Equalization tank for further treatment.

3.8 Primary Clarifier

From here, the effluent flows in three parallel series namely A-series, B-series and C-series.

Three Primary Clarifier are there at NCTL, before expansion of the plant, form 40 MLD to 60

MLD, these were the first Clarifiers to receive the effluent. The effluent used to come from

inlet via Equalization Tank. After expansion, most of the solids are settled down at the pre-

primary Clarifiers. At primary Clarifier, rests of the solids are made to settle down so as to

proceed towards the secondary treatment. The sludge obtained at the bottom of the Primary

Clarifier is pumped out at regular intervals and sent to sludge thickener and then to the Decanter

for De-watering purpose.

3.9 Culture Tank

NCTL is having Culture tank which is used for the growth of microbes. Culture tank helps

replacing some of the MLVSS in following activated sludge process when needed. In The

Culture tank Spent wash or Jaggery from sugar industries is added as food and oxygen is

dissolved in the tank. The microbes developed at a culture tank where they get acclimatized by

giving them some exposer to the effluent. At culture tank, the ratio BOD : N : P = 20 : 1 : 5 is

maintained and also a fixed ratio of fresh water to that of the effluent and spent wash or jaggery

is maintained for microbe’s growth. Nutrient phosphorous is added in form of phosphoric acid


since microbe need nutrient like phosphorous and nitrogen for new cell synthesis. But nitrogen

is sufficient in wastewater introduced so it is not added externally.

3.10 Aeration Tank

There are in total 11 Aeration Tanks Available at NCTL as can be seen in the Process Flow

Diagram. From the 4 tanks available each in A and B series, the first two are not used for

Aeration purpose, similarly, the first tank out of three of C series is also not used for Aeration

Purpose. Effluent is filled in those tanks because the required BOD is obtained after the aeration

in rest two tanks. Here microbes are introduced to influent which oxidizes the organics and

ultimately reduces the BOD of wastewater.

Initially Blowers were installed to serve the purpose. The high pressure air was blown

from blowers to the diffusers installed at the bottom of the Aeration Tanks.

The Blower system was changed to the Surface aspirators. These are floating aeration

devices which are better than diffusers at aeration and mixing to serve the purpose required at

NCTL.

3.11 Secondary Clarifier

There are Four Secondary Clarifiers at NCTL. One each for A and B series and two for C series

making approximately same capacity of that of A or B series. Separation of MLSS is done in

a secondary clarifier which operates in the same manner as the primary clarifier described

previously. Some of the solids collected in the secondary clarifier (return activated sludge) are

sent back to the aeration tank to treat more wastewater and the excess (waste activated sludge)

is pumped out to thickeners and sent for final disposal. The effluent water that flows out the

top of the clarifier is sent along for guard pond and then final discharge sump.

3.12 Guard pond

Guard pond with 24 hrs detention time is provided to hold effluent in case of discharge delays.

The water from Secondary Clarifiers of each series comes to the Guard Pond. Initially only one

guard pond was there to satisfy with the needs according to the 40 MLD plant, later on with

further expansion of 20 MLD more, another pond was created besides the initial guard pond.

3.13 Final sump and discharge

The final treated effluent is collected in sump from where it is discharged deep into the sea

with the help of 44 km long onshore & 10 km long offshore pipe line through scientifically

designed diffuser. At marine outfall point maximum 235 and minimum 175 times dilution is

available since dispersion rate is too high. Treated effluent is monitored with the help of online

pH meter, TOC analyzer and flow meter before being finally discharged. Composite sample

analysis is made to ensure compliance to marine standard.

4 | E n v i r o n m e n t a l M a n a g e m e n t a t N C T L P a g e | 13

4. Environmental Management at NCTL

1. Since NCTL is an End of the Pipe Treatment, prevention of waste is not waste

generation is not possible on its part.

2. No recycling, No segregation and No reduction of waste occur.

3. NCTL was planned according to inlet parameter of 1000 mg/l COD, but actual inlet

exceeded that. To comply with the situation, flow meters were installed at the outlet of

each member industry and all parameters are analyzed by NCTL, GPCB and Third

Party.

4. Surface aerators were installed to reduce the BOD of waste water which ultimately

reduced the COD from 1000 mg/l to 500mg/l.

5. The efficiency of Diffuser decreases with time. To meet the consequences, Surface

Aerators were installed.

6. Deep sea discharge of effluent via diffuser is done and Institutes like NIO (National

Institute of Oceanography) check and monitor the diffusion and dilution of effluent on

regular intervals. Minimum dilution of 175 times and maximum dilution of 235 times

is noted to occur.

7. Energy Management

a. Gravity

b. VFD

8. Re-use

a. SAC instead of PAC

b. Sugar fact waste used as biomass

9. The sludge generated at the end of clarification process is dewatered and sent to BEIL

(Bharuch Enviro Infrastructure Limited) for final disposal.

10. Continuous monitoring of noise is done.

5 | S a f e t y a t N C T L P a g e | 14

5. Safety at NCTL

1. Safety in lab: Hand gloves, Shoes, Goggles, Lab Coat

2. More Safety Required At Aeration Tank

3. Lighting arrestors at top of buildings

Table-2: Places at NCTL where lighting arrestors are installed

Sr.

No.

Place Range

1 Adm 5-10 m

2 Old blower house 5-10 m

3 FPH area 5-10 m

4 New Blower

House

5-10 m

Sr.

No.

Place Range

5 EPH 5-10 m

6 DG, Storage area 100 m

7 Tert. Decanter

house

100m

8 NCR 100m

4. Electric lines were previously underground for safety purpose now they are over head

5. Fire Alarm (Accident Alarm), Tuesday 11:00 am alarm is tested

6. Assembly points in case of emergency

7. Life jackets for tank’s and aspirator’s Maintenance

8. Life Ring at all tanks

9. Crane for aspirator removal/ installation

10. Boat for Aerator Maintenance

11. MSDS for all chemicals at Lab (Material Safety Data Sheet)

12. Dyke area – surrounding tanks

13. Earth pits – checked each 12 months

14. Motor covers and coupling guards

15. Wind sock for wind direction in case of fire

16. Lime dosing safety PPE: Boots, Apron, Mask

17. Safety Showers

18. Fire Extinguisher and Sand Buckets for fire

19. First Aid Box

20. Monthly safety training for workers

21. Total body checkup per year

22. Every Friday doctor arrives for minor check ups

6 | E q u i p m e n t u s e d P a g e | 15

6. Equipment used

6.1 Pumps

NCTL has installed centrifugal as well as piston pumps for various pumping purposes.

6.2 Aspirators

Aspirators are used as surface aerator in the aeration tank unit. It operates by creating a partial

vacuum under the water, drawing air through the shaft and dispersing the oxygen into the water

in a horizontal direction.

Figure-3: Surface Aspirators Figure-4: Surface Aspirators working

6.3 Decanters

Decanters are devices which is used for the separation of dry solids from the sludge and

each decanter separate 5 to 6 ton dry solids in one day. Poly dosing is done to bind the sludge

for better sludge dewatering.

Figure-5: Decanter Figure-6: Decanter working


6.4 Filter Press

Figure-7: Filter press Figure-8: Sludge dewatered cake

A filter comprises a set of vertical, juxtaposed recessed plates, presses against each

other by hydraulic jacks at one end of the set. The pressure applied to the joint face of each

filtering plate must withstand the chamber internal pressure developed by the sludge pumping

system. This vertical plate layout forms watertight filtration chambers allowing easy

mechanization for the discharge of cakes. Filter clothes finely or tightly meshed are applied to

the two grooved surfaces in these plates.

Orifices feed the sludge to be filtered under pressure in the filtration chamber. They are

usually placed in the center of the plates allowing a proper distribution of flow, right pressure

and better drainage of sludge within the chamber. Solids sludge gradually accumulates in the

filtration chamber until the final compacted cake is formed. The filtrate is collected at the back

of the filtration support and carried away by internal ducts.

The filter press is an intermittent dewatering process. Each press operation includes the

following steps:

1. Closing of the press: as the filter is completely empty, the moving head activated by

the jacks clamps the plates. Closing pressure is self-regulated through filtration.

2. Filling: During this short phase chamber are filled with sludge for filtration. Filling

time depends on the flow of the feed pump. For sludge having good filterability it is

best to fill the filter very quickly so as to avoid the formation of a cake in the first

chamber before the last ones have been filled.

Figure-9: Filter press working

http://www.google.co.in/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=7UJgeTqqQxn1iM&tbnid=1XCoN5PP6vAFeM:&ved=0CAUQjRw&url=http://www.mse-filterpressen.de/en/dewatering-biogas-plant.html&ei=xvq3U4n4KNiVuATBp4LADA&bvm=bv.70138588,d.c2E&psig=AFQjCNG_XUS6YkpxZ03eBLjQErwbc7kwlA&ust=1404652593341572


3. Filtration: Once the chamber have been filled continuous arrival of sludge to be

dewatered provokes a rise in pressure due to the formation of an increasingly thick layer

of filter sludge on the cloths. This filtration phase can be stopped manually, by a timer

or more conveniently by a filtrate flow indicator which issues a stop alarm when the

end of filtration rate has been reached. When the filtration pump has stopped, the filtrate

circuits and central duct, which is still filled with liquid sludge, are purged by

compressed air.

4. Filter opening: The moving head is drawn back to disengage the first filtration

chamber. The cake falls has a result of his own weight. A mechanized system pulls out

the plates one by one. The speed of plate separation can be adjusted to account to the

cake texture.

5. Washing: Washing of clothes should be carried out every 15-30 processing operations.

For mid or large units this take place on press using water sprayers at very high pressure

(80-100 bar). Washing is synchronized with separation of plates.

The production capacity of a filter press is somewhere between 1.5 and 10 kg of solid

per m2 of filtering surface. For every the filter press model the chamber volume and the filtering

surface depend on the number of plates in the filter.

In practical terms pressing times are less than four hours filtration time depends on:

cake thickness

sludge concentration

specific resistance

compressibility coefficient.

One of the advantages of the filer press is that it can accept sludge with average

filterability. It is always advantageous to optimally thicken sludge before filter press

operations. Although sludge presenting a high filterability enables better production capacities,

a filter press still accepts sludge with low conditioning precision. This tolerance means that the

device offers greater overall operational safety.

The filter press is suitable for almost all types of sludge:

Hydrophilic organic sludge: inorganic conditioning is often recommended to enable

satisfactory cake release due to minimal adherence to filter cloth.

Hydrophilic inorganic sludge: the filer press generally requires the addition of lime

only.

Hydrophobic inorganic sludge: it is very dense and ideal for the filter press. It is

dewatered without any preliminary conditioning.

Oily sludge: the filter press can be used to treat sludge containing light oils, the

presence of grease can sometimes impair the smooth running of the filter; clothes have

to be degreased at frequent intervals.

NCTL is also having filter press which is used for the same purpose as the Decanter.

But it is more efficient compare to decanter because of it gives best result and less time require

for the separation. It removes 4 to5 ton dry solids in an operation and time is required 8 hours.

http://www.lenntech.com/sludgethickening.htm

7 | A n a l y t i c a l l a b o r a t o r y a t N C T L P a g e | 18

7. Analytical laboratory at NCTL

7.1 Overview

NCTL has equipped analytical laboratory that analyzes around 80 samples a day of

plant itself and of member industries. A very skilled chemist staff is analyses around 20

parameters and they follow the GPCB standard manuals for analysis of wastewater. Data

management of the laboratory is appreciable. We have done some of the analysis by ourselves

then we came to know some of the practices adopted by chemists for accurate readings.

7.2 List of Analytical instruments

7.2.1 Atomic Absorption Spectrometer

7.2.2 Ultraviolet spectrometer

7.2.3 Total Organic Carbon(TOC) analyzer

7.2.4 Flow meters

7.2.5 pH meters

7.2.6 TDS meters

7.2.7 DO meter

7.2.8 Noise level indicator

7.2.9 Oxidation Reduction Potential meter

7.3 Analysis of parameters

Following are the parameters which are analyzed at the NCTL lab. We have focused on some

of the most important parameters. Detailing all the parameters is beyond the scope of this report

but still we have mentioned some of the key points that we have got during analysis mentioned.

Some of the important focused parameters

7.3.1 Chemical Oxygen Demand (COD)

COD analysis is the most important analysis of wastewater. We have done the analysis of

whole set from top to bottom.

Principle

In this experiment we calculate the oxygen consumed by the chemicals in terms of

oxidation agent used.

Generally we use potassium permagnent as oxidization agent but in COD test we

use potassium dichromate as oxidization agent because it have excellent quality of

oxidizing the organic matter.


In this test organic matter and oxidisable inorganic substances present in water get

oxidised completely by standard potassium dichromate in presence of sulphuric acid to

produce CO2 +H2O given in equation (1).

The excess K2Cr2O7 remaining after the reaction is titrated with ferrous ammonium

sulphate. The dichromate consumed gives the O2 required for oxidation of organic matter

given in equation (2). The contents are refluxed for 2 hours.

CnHaOb Nc + d Cr 2O7 2- + (8d+c)H+

nCO2- + (a+8d-3c/2) H2O + cNH +4 + 2d Cr+3.

Where d= 2n/3+a/6+b/3-c/2.

6Fe+2 +Cr2 O72- +14H + 6Fe+3 +2Cr+3 +7H2O

The low molecular fatty acid are not easily oxidized by dichromate so AgSO4 with

sulphuric acid is used as catalyst for oxidizing of fatty acid because Ag+2 have excellent

catalytic property.

Inorganic interferences

Generally chloride ion in water sample generates interference in COD result. Cl-

ion react with K2Cr2O7 and gives higher inorganic COD in result. To prevent such

interference we use HgSO4 (mercuric sulphate) to precipitate the excess of Cl2 as HgCl2.

Hg+2+ 2Cl- = HgCl2

Note:

The COD of any sample should be higher than its BOD.

The aromatic hydrocarbon and pyridines are not oxidizing under any

circumstance.

If the sample have high COD (above 800mg/L) so dilute it before experiment.it

can be known by instant colour change of sample orange to green if it have

high COD during addition of potassium dichromate solution in given sample.

7.3.2 Ammoniacal Nitrogen

It is the parameter which is important from the point of view of nutrient for biological

reactors. Ammoniacal nitrogen in discharge may cause damage to aquatic life of ocean.

Principle

The distillation method is used to separate the ammonia from interfering substance

and the measurement of ammoniacal nitrogen is done. Distillation avails the nitrogen in the

form of NH3 at pH 4.5 this ammonia condensed is collected in absorbent boric acid and

then collected distillate is titrated against dilute acid.


Figure-10: Ammonical Nitrogen analysis

Note:

Use filtrate as sample for aeration so that aeration biomass does not interfere

If Boric acid and mixed indicator solution remains blue up to 150ml there is not

ammoniacal nitrogen present

If it turns green, ammoniacal nitrogen present then titrate it against 0.02N

Sulfuric acid.

Only when acidic sample comes, buffer is used otherwise not.

Wait up to 150ml after color is green.

Keep nozzle dipped into the solution so ammonia does not get to surrounding if

we are using beaker instead round bottom flask for absorbing solution.

7.3.3 Biochemical Oxygen Demand (BOD)

3day BOD method is employed for the measurement of BOD. Only plant samples are

analyzed for BOD. There are two incubators but only one is used having three trays, every

day one tray of samples is removed and one tray of samples is put into the incubator. BOD

data are used to determine the strength of wastewater through plant in terms of oxygen

required for stabilization of waste and for checking wastewater strength from inlet to

discharge.

The principle involved here is to fill the specific sized an airtight bottle with diluted

sample and incubate it at the specified temperature for three days or five days. DO is

measured initially and after incubation. The BOD is calculated from the difference between

initial and final.

7.3.4 pH, TDS, Turbidity, Colour and Odour

At first, these tests are carried out for any sample since they are primary tests. pH and TDS

both are determined by pH meter and TDS meter respectively. Both the meters are

calibrated daily. pH meter is calibrated with buffers of pH 4 and 9 replaced every day. And

TDS meter is calibrated with standard KCL solutions replaced after 3 days. Turbidity and

colour are analyzed visually by observing in 100ml glass measuring cylinder. Odour is also

analyzed by smelling the sample.


7.3.5 TSS, MLSS, MLVSS

Suspended solids are analyzed by filtration and drying. For samples from member

industries vacuum filtration apparatus is used but for plant samples funnel filtration is used.

Whatman filter 41 is used for TSS analysis and Whatman filter 42 is used for MLSS

analysis. MLSS filtration takes 24 h and TSS filtration takes 8 h to filter. Samples from

activated sludge process is not directly used for other analysis but filtrate is used for further

analysis so the biomass does not interfere COD, BOD, Nitrogen etc. analysis.

Note:

Take initial and final weight of filter paper directly from desiccator otherwise it

will absorb so much moisture.

Whatman filter no.42 is denser than no.41 since it has less pores than no.41.

7.3.6 Oil and grease

Oil and grease analysis is done by to operation in sequence,

1. Solvent extraction

Solvent extraction is carried out in separating funnel using hexane as the

solvent. Oil and grease is extracted from the sample by the 50ml hexane in two

stages. Each by 25ml hexane. Grit is removed from the top and extract is

collected in conical flask.

2. Evaporation

Extract is pass through a filter having 10g anhydrous sodium sulphate to absorb

any water remained in extract and filtrate taken in initially dry weighed beaker.

Now evaporate all the solvent from the extract by heating on hot plate.

Difference between initial (dried) and final weight of beaker gives oil and

grease content of sample.

Some other parameters

7.3.7 Heavy metals

Atomic absorption spectroscope is used to determine the heavy metals present in sample.

7.3.8 Phosphate

Ultraviolet spectroscope is used to measure phosphate content of sample.

7.3.9 Sulphide

7.3.10 Phenolic content

Ultraviolet spectroscope is used to measure phosphate content of sample.

7.3.11 Moisture content for sludge

Moisture content of sludge from decanter was 68 to 72% and from Filter press is 60 to 62%.


7.3.12 Sludge Volume Index (SVI)

Determine the suspended solids concentration of a well-mixed sample of the suspension.

Determine the 30 min settled sludge volume in a liter of graduated cylinder for a liter of

sample.

SVI (mL/g) = (settled volume of sludge,

mL

L)(

103mg

g)

(Suspended solids,mg

L)

7.3.13 SAC Quality & other chemicals used in plant action

Chemicals used in plant processes are also analyzed to determine the quality. One of them

is Spent Aluminum Chloride (SAC) which is the waste product from the other industry so

quality must be determined in order to evaluate the dosing in coagulation.

7.3.14 Toxicity test (fish tank)

Toxicity test is done by using fish tank having fishes sensitive to the toxic substances in

order to identify after dilution of discharge of plant in ocean it will have toxic effect on the

aquatic life or not.

8 | T a s k p e r f o r m e d P a g e | 23

8. Task performed

8.1 On-Field Tasks

8.1.1 Observing the VFD for varying output voltage without power loss

A variable-frequency drive (VFD) (also termed adjustable-frequency drive, variable-speed

drive, AC drive, micro drive or inverter drive) is a type of adjustable-speed drive used in

electro-mechanical drive systems to control AC motor speed and torque by varying motor

input frequency and voltage. We have seen all the VFDs installed at NCTL.

8.1.2 Few measures taken to lower the noise of fluid passing through pipes

Lower the bends and tangential flow when necessary

Fix the pipe with sufficient support and clamps to avoid vibrations

Decrease the pipe diameter where necessary to maintain same pressure through

out

8.1.3 Observe the actual RPM of clarifier rotating arm cycle

We have observe the actual RPM of clarifier rotating arm of primary and preprimary

clarifier and it is found to be primary clarifier arm is slightly faster than preprimary because

preprimary has full diameter are where else primary has half diameter arm.

8.1.4 Observing the foam appearance and its cause

We have observed the foam color of B-series tank was white one which was not normal

and it is found to be it is because of slightly low MLVSS. After three day when we went

back foam color was light tan which is the normal condition. Operator must have taken

corrective actions.

8.1.5 Observed the flow rate of monsoon and comment

When we have observed the flow rate when heavy rain has just appeared, the flow rate of

inlet gone too much higher than its desired value. It has one positive impact that influent

get diluted and all the parameter concentration get reduced but one negative impact is

system has to handle more than its design capacity. Fortunately NCTL plant has the

capacity to accumulate influent.

8.1.6 Comparison between preprimary primary and secondary clarifier


Table-3: Comparison between pre-primary, primary, secondary clarifiers

Sr.

No.

Parameter of

Comparison

Pre-Primary

Clarifier Primary Clarifier Secondary Clarifier

Design calculation comparisons

1. Inlet Flow rate 15 MLD 20 MLD 20 MLD

2. Quantity 4 Nos 3 Nos 3 Nos

3. Surface Area

𝐴 =π

4d2

= π

4(402)

= 1256.63 m2

= π

4(262)

= 530.93 m2

= π

4(552)

= 2375.83 m2

4. Volume

𝐴 =π

4d2h

= π

4(402)(3.8)

= 4775.22 m3

= π

4(262)(4)

= 2123.72 m3

= π

4(552)(4)

= 9503.32 m3

5.

Surface Overflow Rate

SOR=𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑚3

𝑑𝑎𝑦⁄ )

𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 (𝑚2)

=15000

1256.63

= 11.94 𝑚3 𝑑𝑎𝑦⁄

𝑚2

=20000

530.93

= 37.67 𝑚3 𝑑𝑎𝑦⁄

𝑚2

=20000

2375.83

= 8.42 𝑚3 𝑑𝑎𝑦⁄

𝑚2

6.

Detention Time

= 𝑉𝑜𝑙𝑢𝑚𝑒 (𝑚3)×24

𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑚3

𝑑𝑎𝑦⁄ )

=4775.22 × 24

15000

= 7.6 hrs

=2123.72 × 24

20000

=2.5 hrs

=9503.32 × 24

20000

=11.4 hrs

7. Revolutions per hour 2.5 - 3 3 - 3.5 3 – 3.5

Other Comparisons

8. Oil Scrapper Yes, it is present No, it is not

required

No, it is not required

9. Effluent Inlet From the Top From

Bottom(centre)

From Bottom(centre)

10. Drive Central Driven

Motor

Periphery driven

Motor

Periphery driven

Motor

11. Clarifier Position Almost

underground

Partially

underground

Partially

underground

12. Removal of Total Suspended

Solids

Solids Left over

after pre-primary

Clarification

MLSS after Aeration

13. Effluent Comes From Inlet Equalization Tank Aeration Tank

14. Oil and grease

peripheral baffle

Yes present Not present Not present

15. Scrapper arm – Sludge

rake

(for the same RPM

pre-primary scrapper

removes sludge twice)


8.2 Off-field Tasks

8.2.1 Difference between Coagulant and Flocculent

The process of coagulation neutralizes charges on the suspended particles by addition of a

coagulant so that other forces such as repulsion are nullified on the particles. When the

charges are neutralized they can come closer to each other and join together to form bigger

particle called flocs. Process of floc formation is known as flocculation. Due to their own

weight enough for gravitational force to make it settle, they come out of suspension and

starts settling down. A Coagulant is the chemical that is added to neutralize the particles

(i.e. Aluminum chloride). Flocculent is a chemical, typically organic, added to enhance

flocculation process (i.e. poly electrolyte).

8.2.2 Difference between Primary, Secondary and tertiary treatment (Levels of

wastewater treatment) adopted from Metcalf and Eddy, wastewater

engineering,2011, pg. 11

Table-4: Levels of wastewater treatment

Preliminary

Removal of wastewater constituents such as rags, sticks, floatables, grit,

and grease that may cause maintenance or operational problems with the

treatment operations, processes, and ancillary systems

Primary Removal of a portion of the suspended solids and organic matter from

the wastewater

Advanced

primary

Enhanced removal of suspended solids and organic matter from the

wastewater typically accomplished by chemical addition or filtration

Secondary

Removal of biodegradable organic matter (in solution or suspension)

and suspended solids. Disinfection is also typically included in the

definition of conventional secondary treatment

Secondary

with nutrient

removal

Removal of biodegradable organics, suspended solids and nutrients

(nitrogen, phosphorus or both nitrogen and phosphorus)

Tertiary

Removal of residual suspended solids (after secondary treatment),

usually by granular medium Filtration or micro screens. Disinfection is

also typically a part of tertiary treatment. Nutrient removal is often

included in this definition

Advanced

Removal of dissolved and suspended materials remaining after normal

biological treatment when required for various water reuse applications

8.2.3 Feasible vs. viable

Feasible is technically sustainable. Viable is commercially possible.

8.2.4 Few energy saving strategies at design stage

Using natural forces ( like gravity) to carry out operations and processes


Install adjustable speed drives (i.e. Variable frequency drives) on pumps and

blowers for variable operations

Install DO monitoring and control in aeration tanks

Install electric load monitoring devices

8.2.5 Few energy saving strategies adopted by NCTL at design stage

Operations by gravity instead of pumps

NCTL has used gravity to carry out as much as operation possible.

1. Convey effluent from member industries through gravity pipeline

2. Clarifiers are used instead filtration devices that uses gravity to settle

suspended solids.

Aspirators are installed since have lower power consumption than diffuser

system.

Variable frequency drives are installed that does not cause power loss due

to varying speed.

NCTL is experimenting on filter press for sludge dewatering that has lower

power consumption than decanter.

8.2.6 Variable frequency drive

A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric

motor by varying the frequency and voltage supplied to the electric motor which does not

cause power loss just as conventional resistor regulators. At NCTL, VFDs are installed at

four places,

1. Equalization Pump House

2. Secondary Recirculation

3. Recirculation Pump House

4. Final Discharge

8.2.7 Design and process control parameters, their significance and typical values

Clarifiers: Important design considerations

8.2.7.1 Surface overflow rate (SOR) or Surface loading rate

Sedimentation tanks (clarifiers) are normally designed on the basis of a surface

overflow rate expressed as cubic meters per square meter of surface area per day,

m3/ m2·day. The selection of suitable loading rate depends on the type of

suspension to be separated.

SOR = 𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑚3

𝑑𝑎𝑦⁄ )

𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 (𝑚2)


SOR for plain sedimentation is 18-24m3/m2·day and sedimentation

following coagulation and flocculation is 28-36 m3/ m2·day. Higher the SOR,

lower the Detention time, lower the SS removal.

For example, in section of comparison between preprimary primary and

primary clarifiers, we obtained the SOR for three clarifiers, we conclude that

major part of SS get removed in preprimary so its SOR is lower than primary but

secondary clarifier has to handle biomass having poor settling characteristics. So

secondary clarifier has lowest SOR hence detention time also changes

accordingly.

SOR is directly proportionate to detention time required. If SOR is too

small the detention time required is more and dimension of the unit will be too

big and ultimately cost will be more so we should select such SOR at which

efficiency is optimum and detention time is minimum.

8.2.7.2 Weir overflow rate (WOR) or Weir loading rate

Weir loading rates are used commonly in the design of clarifiers although they

are less critical in clarifier design than hydraulic overflow rates.

WOR = 𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑚3

𝑑𝑎𝑦⁄ )

𝑐𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑜𝑓 𝑐𝑙𝑎𝑟𝑖𝑓𝑖𝑒𝑟 (𝑚)

The value of WOR should be between 200 to 300 m3/ m2·day. It

determines the velocity at which the water will flow towards the outlet. Higher

the WOR higher the flow velocity.

V-notchs are provided to control the WOR having small flow fluctuations

and make uniform flow.

8.2.7.3 Detention time

The time for which the water or effluent remains in the tank and fill and

withdrawal is possible in the small amount is called as detention time.

Detention time = 𝑉𝑜𝑙𝑢𝑚𝑒 (𝑚3)×24

𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑚3

𝑑𝑎𝑦⁄ )

Depending upon the type of solid its value may be decided. By analysis or

experience its value can be decided. For plain sedimentation 3 to 8 h. For

sedimentation following coagulation and flocculation 2 to 4 h, typically 3.

8.2.7.4 Velocity and turbulence

Based on type of solids, horizontal velocity of particles and turbulence has huge

impact on settling of particles. Flow must be close to laminar region for optimum

settling and horizontal velocity (also termed as scour velocity) must be in

optimum range.


Activated sludge process: Process control parameters

8.2.7.5 Constant MLSS concentration

The mixture of activated sludge and effluent in the aeration tank is called “Mixed

liquor”. Suspended solid in the mixed liquor are called “Mixed liquor suspended

solid (MLSS)”.

At 550±50˚C the organic fraction of MLSS will be oxidized and driven

off as gas. This fraction of MLSS is referred to as “Mixed liquor volatile

suspended solids (MLVSS)”. MLVSS represents the amount of microbes present

in wastewater.

MLSS = MLVSS + MLFSS is of no use

Depending upon the type of industry, nature of coagulants used and the

sludge age, the MLVSS constitute from 60% to 90% of MLSS. MLVSS/MLSS

ratio must be as high as possible because MLFSS content just increase the load

and does not help in any manner.

MLSS concentration should be in the range of 3000 to 5000ppm. If MLSS

is higher than 5000ppm clarifier will not be able to handle it and overflow

discharge of clarifier will higher COD because of unsettled MLSS

8.2.7.6 Dissolve oxygen (adopted from Metcalf and Eddy, Wastewater

engineering,2011, pg.690)

Theoretically, the amount of oxygen that must be transferred in the aeration tanks

equals the amount of oxygen required by the microorganisms in the activated-

sludge system to oxidize the organic material. In practice, the transfer efficiency

of oxygen for gas to liquid is relatively low so that only a small amount of oxygen

supplied is used by the microorganisms. When oxygen limits the growth of

microorganisms, filamentous organisms may predominate and the settleability

and quality of the activated sludge may be poor. In general, the dissolved oxygen

concentration in the aeration tank should be maintained at about 1.5 to 2 mg/L in

all areas of the aeration tank. Higher DO concentrations (>2.0 mg/L) may improve

nitrification rates in reactors with high BOD loads, Values above 4mg/L do not

improve operations significantly, but increase the aeration costs considerably. The

aeration capacity of the aerators should be sufficiently flexible, to reasonably

match the DO requirement of the variable effluent flows and loadings.

8.2.7.7 F/M

The F/M ratio (the relationship in the mixed liquor of the amount of incoming

food to the amount of microorganisms) describes how well the process will

perform.


F/M = ( BOD ,

mg

L) × ( Q ,

m3

day )

( MLVSS ,mg

L ) × ( V ,m3 )

Where, Q = Flow rate, V = Aeration tank volume, m3

The ideal F/M for a well stabilized Activated Sludge Process ranges from

0.2 to 0.4.

If F/M ratio is higher than 0.4 than it indicates that food available (i.e.

BOD) per microorganism is high. The growth rate of microbes is high. But

ultimately we will not get the desirable results.

If F/M is lower than 0.2 than it indicates that food available per

microorganism is less. The growth rate of microorganism is low. Under such a

circumstances the microorganism will go under endogenous phase. And will not

be able to get the desired results.

8.2.7.8 Sludge volume index (SVI)

Sludge volume index is a test to evaluate sludge settling or thickening

characteristics, and techniques have been developed to apply these fundamental

characteristics to clarifier design. SVI is the volume of 1g of sludge after 30 min

of settling.

SVI (mL/g) = (settled volume of sludge,

mL

L)(

103mg

g)

(Suspended solids,mg

L)

SVI values below 100 mL/g are desired and is considered as good settling

sludge. And above 150 mL/g are typically associated with filamentous growth.

8.2.7.9 Sludge recycle and wasting

The purpose of the recycle of activated sludge is to maintain a sufficient

concentration of activated sludge in the aeration tank so that the required degree

of treatment can be obtained in the time interval desired. The return of activated

sludge from the final clarifier to the inlet of the aeration tank is the essential

feature of the process.

Common control strategies for determining the return sludge flow rate are

based on maintaining either a target MLSS level in the aeration tanks or a given

sludge blanket depth in the final clarifiers.

To maintain a given SRT, the excess activated sludge produced each day

must be wasted.

To determine the Sludge Recycle Rate (SRR) material balance can be

made.

QR

Q= R =

X

XR − X

Where,


QR = Recycle flow rate

Q = Influent flow rate

X = Concentration of MLSS in aeration tank

XR = Concentration of MLSS in recycle stream

R = Ratio of recycle flow rate to influent flow rate, typical

value 0.50

8.2.7.10 Solid retention time (SRT) or Mean cell residence time (MCRT) or

Sludge age

SRT, MCRT and sludge are different terms but represents the same control

measure. They represents the average period of time during which the sludge has

remained in the system.

SRT = Total weight of solid in the activated sludge process each day

Total weight of solid leaving the activated sludge process each day

SRT is the most critical parameter for activated sludge design as SRT

affects the treatment process performance, aeration tank volume, sludge

production, and oxygen requirements.

8.2.8 Troubleshooting activated sludge process

By the experience one can predict the problem by just observing the appearance of the foam

of aeration tank.

Few troubleshooting problems given to solve

8.2.8.1 DO become nil

1. Check DO for proper aeration

If under aerating increase aeration to maintain 2.3ppm

2. Check aeration equipment

Repair, if any problem

3. Check MLSS

If too high, adjust MLSS to proper F/M. Increase sludge wasting or

transfer MLSS to another tank if possible.

8.2.7.2 DO rises above limit

1. Reduce the aeration to maintain DO to 1.0 to 2.0ppm

2. Check MLVSS, if it is decreasing adjust it by reducing the wasting.

Increase the return up to some extent.

3. Check the toxicity of the influent as well as sludge. If influent is

toxic then take preventive steps at primary or preprimary clarifier to

reduce toxicity. Simultaneously replace activated sludge with new


culture or healthy sludge from another tank as much as possible and

waste toxic sludge.

8.2.7.3 MLVSS/MLSS decrement

1. Check SRT, if it is increasing then increase sludge wasting.

2. Check Influent TSS, if it is increased then take preventive action at

primary or preprimary clarifiers.

3. Check MLVSS, if it is decreasing then review the steps 2 and 3 of

DO rise

8.2.7.4 Foam increases, SVI increases

1. Check for available nutrients, if it is less then it might increase

filamentous growth causing foam increase or bulking sludge due to

poor settling characteristics. Adjust nutrient level by monitoring it.

2. Check for low DO at various locations throughout, if it is, then check

for aeration and adjust it.

3. Use defoamer to decrease foam directly.

8.2.7.5 If filamentous bacteria increases then what to do to settle sludge.

1. Apply coagulant or increase poly-electrolyte dosing.

8.2.7.6 Aeration tank pH decreases

1. Check aeration influent if it is lower than 6.5 the take corrective

action at preprimary clarifier by adding caustic or lime.

8.2.7.7 Shock load (COD loading to high)

1. After calculating the F/M and kg MLVSS needed you may find F/M

is high and the kg MLVSS inventory is low. Therefore do not waste

sludge from the process for a few days or maintain the minimum

wasting rate if possible. If not sufficient then seed the process with

healthy activated sludge from a well operating plant.

8.2.9 Concept of Endogenous phase

During biological oxidation, first, the portion of the waste is oxidized to end products to

obtain energy for cell maintenance and the synthesis of new cell tissue. Simultaneously,

some of the waste is converted into new cell tissue using part of the energy released during

oxidation. Finally, when the organic matter is used up, the new cells begin to consume their

own cell tissue to obtain energy for cell maintenance. This third process is called

endogenous respiration. And the phase is called endogenous phase. To control microbial

growth and maintain F/M ratio plant is operated near Endogenous conditions.


Figure-11: Three phases of microbial growth

8.2.10 Effect of pH and temperature aerobic treatment

Depending on the buffering capacity of the system, the pH may drop to a low value of about

5.5 at long hydraulic detention times. The potential drop in pH is due to the increased

presence of nitrate ions in solution and the lowering of the buffering capacity due to air

stripping. Filamentous growths may also develop a low pH values. The pH should be

checked periodically and adjusted if found to be excessively low.

With all the biological systems, lower temperatures retard the process while higher

temperature accelerate it. In addition, Temperature has impact on oxygen transfer rate. At

higher temperature oxygen transfer rate decreases, where at lower temperature oxygen

transfer rate increases.

8.2.11 Advantages and disadvantages of aerobic processes compared to aerobic

processes

Advantages

Less energy required

Less biological sludge production

Fewer nutrients required

Methane production, a potential energy source

Smaller reactor volume required

Elimination of off-gas air pollution

Rapid response to substrate addition after long periods without feeding

Disadvantages

Longer startup time to develop necessary biomass inventory

May require alkalinity addition

May require further treatment with an aerobic treatment process to meet

discharge requirements

Biological nitrogen and phosphorus removal is not possible


Much more sensitive to the adverse effect of lower temperatures on reaction

rates

May be more susceptible lo upsets due to toxic substances

Potential For production of odors and corrosive gases

8.2.12 Generation of filamentous bacteria

In filamentous growth, bacteria form filaments of single-cell organisms that attach end-to-

end, and the filaments normally protrude out of the sludge floc. This structure, in contrast

to the preferred dense floc with good settling properties. Has an increased surface area to

mass ratio, which results in poor settling. Which leads to bulking sludge problem.

Activated sludge reactor operating conditions (low DO, low F/M, and complete mix

operation) clearly have an effect on the development of filamentous population. One kinetic

features of filamentous organisms that relates to these conditions is that they are very

competitive at low subtract concentration whether it be organic substrates, DO, or nutrients.

8.3 Lab tasks

8.3.1 Analytical report analysis

We have observed the analytical report of plant, we have seen the parameters and how they

changes. We conclude that parameter fluctuates but plant has to handle all the fluctuation

since it is end of the pipe treatment.

8.3.2 SVI experiment and conclusion

We have observed SVI experiment of two sample namely aeration tank and sludge recycle.

We conclude that since sludge recycle is more concentrated than aeration tank, sludge

volume of recycle is more than aeration tank. SVI of both is normal hence reasonably good

settling sludge.

8.3.3 Performing analysis of parameters

We have done analysis of the parameters namely MLSS, TSS, MLVSS, COD, Ammoniacal

nitrogen, BOD, sulphide content, TDS, pH, turbidity. And observed the analysis of oil and

grease, heavy metals, etc. The report is presented analysis section 7.

9 | L e a r n i n g o u t c o m e s P a g e | 34

9. Learning outcomes

9.1 About industrial work culture

People at NCTL are very calm and collaborative. Calmness and patience is our biggest weapon

and frustration is our biggest rival when working in any industry. Teamwork empowers the

strength of the industry. Since work culture changes from industry to industry, we have to learn

their way of working and accordingly work. Self-management allows us to reduce our overall

effort and makes it easier to work. Adjustment and compromises has to be made if we want to

successfully achieve your organizational and personal goal. Learning should not stop if we

really want to grow in your field. We must have professional relationship with every one we

are working with.

9.2 Gap between theory and practical application

Theories are the basis of practical applications but we cannot see the connection between them

until we minimize the gap between them as much as possible. Theories are based on some

assumptions and framework but practical application have no such framework. We have to

break our mindsets and avoid thinking virtually.

9.3 Possibilities of tertiary treatment

NCTL does not have any kind of tertiary treatment because it is having such a big mass load

to handle. Commercially viable technology cannot be found easily. Many technologies are

tested like Electro coagulation, ozonation, Ultrasonic sound, RO, etc. but many of them are not

viable. But NCTL along with some of the organizations are trying very hard to find the

technology that is commercially viable in context with NCTL. We learned that many times we

have technology but we must think about its viability and its consequences before employing

it.

9.4 Conventional treatment vs. modern treatment

Nowadays the treatment methods are getting changed. New technologies are being

implemented instead some of the conventional treatment technologies. But we must understand

that most of the modern treatment methods are costlier than conventional treatment in addition

to that we require very skilled labor and technicians to handle modern technologies. Most of

this technologies were invented in western countries and they are implementing because they

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have very skilled labor, technicians and engineers. But in India scenarios are different, we may

it very difficult to find or even train labors and technicians to operate such technology and even

if we do that, new operator has to be trained again after trained operator left. So we conclude

that conventional treatments are better for some extent but to become competitive we must find

alternatives.

9.5 Selection of resource for precise reference

We often find it difficult for us to understand something even if we already took some reference

and selecting one reference to make us understand the thing or topic. So the solution for this

problem is find as much reference as you can and study all the references thoroughly and select

one by which we can have clear understanding of the topic or problem. But in some cases we

have to follow multiple references because nothing is perfect in this world. Above all we must

try to find the most standard references for the topic or problem.

9.6 Uncertainty in industrial practice

When we are student, we have very precise framework to solve problems theoretically. But

when we enter to the industry there are no frameworks or standards to tackle all the problems

and we have too many uncertainties in industrial practice. So we should evaluate the nature of

the problem and then try to find the best way to tackle it. But many times we fail, in those cases

we should not lose our patience and try the alternative ways to solve them.

9.7 Management Facts, PDCA cycle, SWOT analysis

PDCA (plan–do–check–act or plan–do–check–adjust) is an iterative four-step management

method used in business for the control and continuous improvement of processes, products,

design. For example, NCTL has planned for 40mld plant and they have implemented it. But

when they checked its performance they found that they are receiving more influent than they

planned so they acted to evaluate actual requirement and again planned for another 20mld.

Now the plant capacity is just as per the requirement of 60mld.

A SWOT analysis (alternatively SWOT matrix) is a structured planning method used

to evaluate the strengths, weaknesses, opportunities, and threats involved in a project or in a

business venture. A SWOT analysis can be carried out for a product, place, industry or person.

When we find ourselves in the situation where we have to deal with other’s ego or competition

we should do this analysis.

Strengths: characteristics of the business or project that give it an advantage over

others.

Weaknesses: characteristics that place the business or project at a disadvantage relative

to others

Opportunities: elements that the project could exploit to its advantage

Threats: elements in the environment that could cause trouble for the business or

project

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10. Enhancements at NCTL

1. Flow rate overload: Influent flow rate increases during monsoon due to rainwater

influence. Since discharge rate is fixed there is no way to handle this flow rate. It was

necessary to reduce water influent from the source. But after capacity enhanced from

40MLD to 60MLD made it possible to handle such high influent flow rate. Influent gets

accumulated first in equalization then in guard pond as to avoid shock load flow rate.

2. Aspirators instead of diffusers: because of following disadvantages of diffusers,

aspirators are proved to be optimal option for aeration since aspirators does not have any

of this.

a. High noise created while transmission of air through the blower pipes.

b. Diffusers many times get blocked when some particulates settle down.

c. It was a tough job to detect the blocked spot.

d. During blockages, it could not diffuse oxygen to a required rate leading to odorous

problems.

e. Mixing was not proper with this system.

f. Diffuser membrane fouls in short period of time results in improper oxygen transfer

throughout the tank.

3. Equalisation not able to handle high TSS before pre-primary installed: after design

and establishment of the plant it is found that influent TSS concentration is too much higher

than its design limits. So maintenance period has been reduced to one month, the plant has

to be shut down for days to clean all the TSS from such high tanks which was not tolerable.

In order to solve this problem NCTL established pre-primary clarifiers to settle down major

part of TSS in it.

4. Secondary sludge does not go to decanter for dewatering since its moisture capacity is

high instead thickening is done only.

5. Rather than using all the aeration tanks only two are used in series because major part

of BOD is decreased in two aeration tanks.

6. SAC is used instead of PAC because it is viable to use spent aluminium chloride for

coagulation since it is a used liquid in certain industry. Its impurities are not going to affect

because it is used for wastewater.

7. Similar as SAC, spent wash from the sugar industry waste is used as food for bacterial

growth in culture tank.

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8. In winter season because of temperature drop-down growth of hydrophobic bacteria

increases that will ultimately increase the foam since air bubbles form surrounding the

bacteria body. Defoamer is used to reduce excessive foam. It contains silicon as major

compound.

9. While maintenance of the primary clarifier of A-series, the activated sludge of secondary

clarifier A is kept on recycling without worrying about sludge age. Process can be started

over with minimal external addition of microbes. But if whole series is emptied while

maintenance in that case all the sludge has to be replaced.

10. Filter press vs. decanter: At NCTL, for experimental purpose one of the decanters is

replaced by the filter press. A Decanter can dewater 6 to 7 tons of sludge per day in context

to which filter press is capable of dewatering 10 to 12 tons of sludge per day. Also the

moisture content in the de watered sludge obtained from a filter press is comparatively low,

this sludge is eligible for direct land filling, while that obtained from the decanter is not

that dry and needs 15 days drying which is done under the shed. Decanter also uses Poly

electrolyte dosing which consumes comparative capital cost. Filter press efficiency is

supported by low noise produced and low power consumption against decanter.

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11. References

11.1 Web Pages References

1. http://www.meti.go.jp/meti_lib/report/2014fy/E003830.pdf

2. www.gewater.com

3. http://www.igep.in/live/hrdpmp/hrdpmaster/igep/content/e48745/e49028/e51431/e514

50/AnjiReddy.pdf

4. http://www.sipcotcuddalore.com/downloads/BISWCA.pdf

5. http://www.lenntech.com/library/sludge/presses/filter-press.htm

11.2 Book references

1. A hand book of Effluent treatment plants, Mahjabin Shaikh, Enviro Media.

2. Wastewater Engineering Treatment and reuse, Metcalf Eddy, McGraw Hill

http://www.meti.go.jp/meti_lib/report/2014fy/E003830.pdf

http://www.gewater.com/

http://www.igep.in/live/hrdpmp/hrdpmaster/igep/content/e48745/e49028/e51431/e51450/AnjiReddy.pdf

http://www.igep.in/live/hrdpmp/hrdpmaster/igep/content/e48745/e49028/e51431/e51450/AnjiReddy.pdf

http://www.sipcotcuddalore.com/downloads/BISWCA.pdf

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12. Conclusion

Training was tougher than we expected but it become easier gradually. Only thing about this

training which was not to be excluded ever is precise and well organized guidance our guide.

It made each and every task easier to go through it learn something from that for longer time.

Thus we conclude that if we work positively and sincerely learning becomes easier but we must

need a mentor or guide who can guide us with great interest.

The training was focused on design and operational aspects of common effluent

treatment plant. We gone through all the guided tasks given to us so that we can clearly

understand the NCTL, FETP facility itself with exposer of other scenarios.

From the basic evaluation observed by us, we can say that this facility is running at its

best. Some of the enhancements done by NCTL has solved their many big problems. The vision

of NCTL and its authorities has increased the FETP performance by 50 to 70% since last 7

years.

Though technologies employed are conventional but to handle such big load of 60mld

with more than 1000ppm COD is the big quest for the facility. No technology found that can

be viable enough to get employed. NCTL along with some other organizations working really

hard to increase plant performance. Since NCTL is the end of the pipe treatment plant, they

cannot do anything with influent wastewater quality.

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