CSE experts answer the questions raised during the webinar

The questions (and their answers) have been listed under two broad sections, and according to the alphabetical order of the names of people who asked them. Questions from anonymous attendees have been listed at the end of both the sections.

For any further queries, you can reach out to mahreen@cseindia.org.


The report and its methodology
The technologies


Achara Taweesan

Q 1: How about parasitic tests such as helminth – did you conduct such tests? Because this affects public health -- if there is unsafely-managed FS, it can lead to things like helminth-led liver disease, as is the case in many ASEAN countries, particularly Thailand, Laos, Myanmar etc.

Ans: We analysed a few samples for helminths, and found that the outlet treated water was free from helminth eggs. More experiments will be conducted on pathogens in the current year’s projects.



Aditya Vidyasagar

Q 2: Thanks for the session -- there were learnings that I picked up. Hope such sharing would continue in future.

Ans: It will, and thank you for attending and the encouragement

Q 3: Is it possible for CSE to advise any ULBs that are not in the covered area (as shown in your PPT)?

Ans: Yes, we can help. Please get in touch with us (mrinal.mallik@cseindia.org, vinod_v@cseindia.org).



Animesh Koyande

Q 4: Were the samples airlifted from each and every STP to your lab for testing?

Ans: Samples were airlifted or delivered by air cargo only from locations that were very far away -- like Ladakh, Kerala, Tamil Nadu, Odisha, Telangana and Andhra Pradesh. All efforts were made to dispatch the samples to the Lab in the shortest possible time.



Digbijoy Dey

Q 5: Very realistic findings. These tell us about the importance of tertiary treatment. Looking forward to the recommendations on this.

Ans: There are a few options for reducing microbial load in discharged water, such as chlorination, UV treatment, or ozone exposure. Of course, the mode of treatment will depend on end uses of the effluents.



Farhad Safi

Q 6: Were the characteristics of FS collected by the tankers and disposed of in the studied FSTPs widely different?

Ans: Yes. A separate report will soon be published on the subject.



Ganesh Parida

TQ 7: Thank you CSE for this study. Practical Action has built the FSTP at Dhenkanal. CSE should mention this in the report.

Ans: We have described the initiative taken by Dhenkanal Municipality and the Government of Odisha to build an FSTP (the first of its kind in the state) in ‘Description of treatment system’ in our report.



Jeevan Roy

Q 8: What kind of variations will the test results show if the plant is under-utilised?

Ans: All the FSTPs that we evaluated are under-utilised. Please refer to the report for details.

Q 9: Were samples from FSTPs collected when the plant was operating at its full capacity? What effects do these tests have with respect to plant capacity?

Ans: In an ideal case, it is advisable to collect samples when the plant is running at full capacity. But in the course of our study, it was not always possible. In a number of cases, samples had to be drawn when the plant was under-utilised.



Jeyannathann Karunanithi

Q 10: You have two FSTPs from the same geography in Tamil Nadu -- do they give any insights into performance?

Ans: Yes they do. Both are working with the same technology and operator. Both FSTPs were observed to be performing almost in the same way in removing the nutrients and the pathogens



Jigisha Jaiswal

Q 11: How was the removal efficiency measured -- by comparing outlet results with inlet leachate quality or with inlet faecal sludge quality?

Ans: All these treatment systems are designed to treat only the leachate -- so the removal efficiency of the contaminants was calculated from inlet leachate and outlet treated water.



Krishna Rao

Q 12: What is the approximate sample size of samples collected at each FSTP (you have only mentioned a time duration of two to nine months)?

Ans: The sample size has been described in Section 3.2.2 of the report (to download, visit www.cseindia.org).

Q 13: Do you have any information with respect to seasonality of the year when test results showed any variations?

Ans: It is advisable to continue the assessment round the year (12 months) to observe any seasonal variations. Seasonal effect was not much pronounced in the CSE study except in the month of July (rainy season), when the microbial load in the liquid stream increased.

Q 14: What was the plant utilisation in terms of the design size of the plant when these samples were taken?

Ans: Capacity utilisation of each plant is different; in a number of cases, samples were drawn when the plant was underutilised



Manasi Mulay

Q 15: I am Manasi R. Mulay, PhD researcher at Grantham Centre for Sustainable Futures in the University of Sheffield, UK. Thank you for accepting my registration request and conducting the webinar. I would like to tweet about the webinar from https://twitter.com/jal_suwidha.

Ans: Thanks a lot, Ms Mulay.



Manas Rath

Q 16: Can the various parameters be combined into a single score to indicate performance level?

Ans: Yes. To understand the performance efficacy of a treatment plant by a single score, unanimous decision has to be taken to ascertain weightage value on each tested parameter based on which final score will be determined. Emphasis should be given on risk assessment of harmful parameters for human health. This initiative has not yet been undertaken.



Mohammad Imtiaz Sharif

Q 17: Rather than asking questions, I would like to provide a few comments. I would like to see the bar charts of Chapter 5 in such a way that all the 12 FSTPs are shown in the same chronological order. Besides, a ranking of performance evaluation would be appreciated.

Ans: Thank you for your inputs. We will work on this in subsequent reports



Paresh Chhajed

Q 18: How many samples were collected each month?

Ans: A batch of at least three samples were collected from each FSTP every month (one faecal sludge sample from the unloading point, one liquid sample after solid-liquid separation, and another liquid sample from the outlet).

Q 19:How does the solid-liquid ratio vary across geography?

Ans: The solid-liquid ratio is highly varied. We will be publishing a sludge characteristic report very soon

Q 20: How would the methodology be different for a study of a treatment unit over a longer duration of time?

Ans: This aspect was not assessed as we did not collect samples over long durations. We hope the treatment plant operators will do this.



Praveen Nagaraja

Q 21: I think this is a very useful and reflective study -- very useful for designing subsequent FSTPs. However, an analysis of bio-solids could have helped view FSTP performance from another perspective

Ans: Characterisation of bio-solids generated from FSTPs has already been initiated in current year.


Rajesh Pai

Q 22: Have you collected multiple samples for analysing the same parameters?

Ans: Every month, we collected one set of samples. Collection of multiple sample was not possible because there is a limit on carrying liquid samples in an airline. The samples were tested in duplicates.

Q 23: Do you have any observations on the average drying period of sludge in drying beds for different geographical areas? What are the challenges faced by operators in terms of O&M that affect the treatment efficiency? Any basis for your conclusions on this?

Ans: We have not done any assessments of observations on the average drying period of sludge. But it is an area we will look at in the coming years. We will also discuss how to engage with operators and understand the working of the plants.



Ruchi A Patil

Q 24: I would like to know about the design capacity and design period, and the overall efficiency of the FSTPs in your survey.

Ans: It is explained in our report, which you can download from www.cseindia.org. Overall performance has been evaluated on the basis of six indicative parameters – these have been described in Section 5 of the report.



Suneethi Sundar

Q 25: What is the next step for CSE, based on these study findings and the final report?

Ans: In the present study, the emphasis has been on treatment of the liquid stream. The next step would be the study on characterisation of bio-mass generated from FSTPs.



Tatjana Schellenberg

Q 26: Did you see any seasonal fluctuations? Do you have data on performance of each process stage? What are the discharge volume flows/time units for each FSTP and how/what are different application areas/discharge environments?

Ans: Seasonal variation data for all FSTPs was not available. Data for each stage has been represented in the Table of results provided in the report. As per our observations, discharge water is mainly being used for horticultural purposes on the FSTP site itself.



Vijai Kumar Chaurasia

Q 27: There are remarkable reductions in various parameters, including the inlet parameters – can you explain the wide variations?

Ans: The answer has been explained in the report.



Vikram Ammavasi

Q 28: What are the end uses of treated water from the analysed FSTPs?

Ans: It is recommended to use discharge water in agricultural field or horticulture, but only after reducing microbial load within the specified limit.



Vishwanath Srikantaiah

Q 29: Why are we comparing FSTP treatment standards with regular WWTP standards? Isn’t WWTP water also diluted very much with grey water, whereas FSTP water is essentially black water?

Ans: There is no separate FSTP effluent discharge standard in India. Though the nature of waste is different, ultimately the treated water is either discharged into agricultural fields or mixed with natural water bodies. Hence, there is no harm in comparing results with stringent STP standards.

Q 30: I'm sure that cost comparisons of treatment will also be available in the report. What is the range of cost per kl of treatment in Rs/kl?

Ans: We have not done a cost analysis as this is outside the ambit of this study. The lab has assessed the technology in terms of its performance. We hope others will use this to understand the cost-benefits of these technologies.



Zinnia Chakraborti

Q 31: How were the FSTPs selected? What was the procedure?

Ans: The FSTPs were selected on the basis of their design, diverse technologies and operational principles.



Anonymous attendees

Q 32: What is the next strategy after this nine-month initial study?

Ans: Analysis of bio-solids generated from FSTPs will be taken up in the next study.

Q 33: I understand that you have analysed FSTPs on the basis of the 2017 guidelines. However, if the NGT guidelines have to be met, how many of these FSTPs do you think will be able to meet them with zero to minimal changes in technology and a minimal cost increase?

Ans: The data is clear and you can assess if these plants will meet the more stringent NGT guidelines. Clearly, this issue will be for operators to assess how they will rework/optimise on the existing technologies to see if these plants can perform to meet these standards. Our study should help both regulators and designers in this work.



Abinash Sahoo

Q 1: :FSTP Bhubaneswar has no post-treatment. How then is it achieving an FC of 1,000 MPN?

Ans: A polishing pond also helps to reduce the FC up to an extent.

Q 2: What are the O&M factors to be considered for a chlorination system, and how economic is chlorination system compared to sand and activated carbon filter?

Ans: The purpose of chlorination and the use of sand and activated carbon filter are different. The later can eliminate the fine particulates and organics from wastewater, but chlorination reduces the microbial load in wastewater. Therefore, one treatment cannot be replaced by the other and the two are not economically comparable.

Q 3: Can we use settler instead of ABR after the solid-liquid separation happens?

Ans: The functions of settler and ABR are different. Settler allows the solid part in the FS to settle down (solid-liquid separation), while ABR facilitates the microbial degradation of organic material.



Anirudh Khanna

Q 4: In Tamil Nadu and Odisha, the treatment is more or less the same -- then why does one need tertiary treatment and the other does not? Is it only to match the standards?

Ans: The treatment module adopted in a FSTP depends on end uses of the discharged water. If it is required to discharge water into natural waterbodies, the load of micronutrients (phosphorus, nitrogen etc) and pathogens has to be reduced drastically. Tertiary treatment is necessary in such a case.

Q 5: Is it viable to install a small community-based FSTP – one that has less mechanism but is still functional? If yes, then what kind of design should we use?

Ans: You can use a DWWT system with proper operation and maintenance.

Q 6: As it is also suggested that an anaerobic process is better in removing BOD and COD, what is your suggestion regarding treatment procedures in the DRDO-based bio-digester? Will it require support of other treatment infrastructure apart from tertiary treatment?

Ans: Anaerobic digestor is being used in DRDO’s Wayanad FSTP. It’s a three-stage process where micro-organisms break down the biodegradable material in the absence of oxygen. These tanks are used to reduce organic load from FS. A polishing pond can help reduce the FC up to an extent.



Avudai Nayakam

Q 7: : I am interested to know more about the tiger bio-filter technology established in the 10-kld Wayanad FSTP.

Ans: In this technology, faecal sludge and leachate are treated using tiger worm (earthworm). For more details, please contact the operator – download and see our report (www.cseindia.org), where you will find the contact details of the operator.



Avudai Nayakam

Q 8: Is there any policy to reuse the dried sludge? How can we use the treated sludge?

Ans: There is no policy yet to reuse dried sludge. A few FSTPs are successfully using co-composting with agri-waste (Ketti, Adigaratty at Coonoor and Karunughuzy in Chennai), vermin-composting (Wayanad), and pyrolysis to make bio-char (Warangal).



G Bala Subramanyam

Q 9: In the case of the Unnao FSTP, the BOD value for septage of new samples is as high as 36,000 and for the second sample, it is only 2,700. But the final outlet BOD value is the same for both -- 8 and 9 mg/l. Comments.

Ans: In Unnao, the solid-liquid separation is done by screw pressing -- so the leachate has high COD and BOD than in other treatment systems (sludge drying bed) that use one step filtration. After screw press, the high BOD leachate is passed through integrated settler and ABR, anaerobic filters, planted gravel filter and sand carbon filter followed by UV treatment and finally, polishing pond. So, the final BOD becomes lower than 10; what should be noted here is that the system is very new.



Jigisha Jaiswal

Q 10: What measures can be taken to enhance removal of total solids and TSS?

Ans: Appreciable removal of TSS and TDS may be achieved by treating water stream with flocculant and subsequent processing through sand and activated carbon filter.



Jogeshwar Singh

Q 11: What is best for a big city – setting plants (DWWT) with less capacity but more in number, or plants having greater capacity but in lesser numbers?

Ans: We cannot answer as we have not assessed this.



Mahendra Chauda

Q 12: Chhattishgarh, they have made FSTPs along with soak pits. In the FSTPs, they have planted plants for drying the faecal sludge. How effective is it?

Ans:Treatment through Planted Sludge Drying Bed (PSDB) has been adopted in several DEWAT systems, where significant improvement in performance has been observed. The selection of soak pit or polishing pond is mainly dependant on the end use of the treated water.

Q 13: At the time of designing of the FSTP, what should be the per capita per day faecal generation?

Ans: This data will be available with the operators.



Nony Gupta

Q 14: How can we make co-treatment facilities more efficient, considering the need for using existing infrastructure for faecal treatment in some cities?

Ans: It is too early to comment on co-processing of FS in existing STPs in India. The only STP which was considered under the purview of the study was the Bharwara STP. We shall conduct an extended study on above aspect in the current year.



Pawan Bharti Chauhan

Q 15: What is the best available eco-friendly technology for treatment?

Ans: We have not done an assessment.



Prakash Chandra Nayak

Q 16: Should we discharge the treated wastewater within the BOD range of 100 mg/l for irrigation? Please elaborate the merits and demerits.

Ans: An MoEFCC notification dated October 13, 2017 says that the discharge standard from an STP will also be applicable for land disposal and applications. Hence, discharge of effluents having BOD of 100 mg/l is not permissible for irrigation purposes.



Pranshu Kumar

Q 17: Can you please name the FSTPs that are currently co-composting dried faecal sludge? What are different methods used to dispose of the dried faecal sludge and what are the parameters?

Ans: In most FSTPs, the sludge is dried and storied separately. A few FSTPs are successfully using co-composting with agri-waste (Ketti, Adigaratty at Coonoor and Karunughuzy in Chennai),vermin-composting (Wayanad), and pyrolysis to make bio-char (Warangal). We will work on this further in the coming year



Rajesh Pai

Q 18: The ABR mentioned here in most of the systems contains ABR (Anaerobic Baffled Reactor) integrated with AF (Anaerobic Filter); in a few systems, it is Settler integrated with AF. Perhaps this can be specified wherever applicable for better understanding of treatment efficiency.

Ans: Systems can be designed with separate Settler and ABR integrated with AF, or Settler integrated with AF. The AF consists of three chambers in series in which the wastewater flows through down-take pipes enabling water to reach the bottom of the tank. Here, the suspended and dissolved solids present in the wastewater undergo anaerobic degradation. As wastewater flows through the filter media, particles are trapped and organic matter is degraded by the biomass that is attached to the filter material. It is clearly mentioned in the report as well.



Sampath Rajkumar

Q 19: We are using the leachate water to water windrows. Please comment

Ans: If the faecal coliform count is high, then it is not advisable to use. The MoEF&CC notification dated October 13, 2017 says that the discharge standard (FC <1000) from an STP will be applicable for land disposal and applications. Here, the FC load in discharged water was observed to be high and treated water is being used for co-composting processes. This will increase the faecal coliform count in the final compost.

Q 20: Is it possible to suggest any specific treatment measures that need to be looked at in Ketty and Adigarahatty?

Ans: Inclusion of ABR system is recommended; also, tertiary treatment can help reduce the pathogen load in the discharge water.



Sanjay Singh

Q 21: It appears your recommendation is that to meet the treatment objective, tertiary treatment is compulsory and it should become an integral part of the design. Also, can you give us any idea about the capacity utilisation levels compared to the designed capacity?

Ans: Yes. It is recommended for the removal of pathogens. As for the second part of your question, we have not assessed this aspect as it was not part of the ambit of this study. Please do contact the operators to collect this information.



Shaji Ramakrishnan

Q 22: In hot zone reed beds, where temperatures go up to 41 degrees, do you use sprinklers to maintain the moisture level to keep the plants healthy? Have you used enzymes at the inlet of a reed bed?

Ans: The above process is not usually adopted. Enzymes are not used at the inlet of the reed bed.



Shashank Nautiyal

Q 23: Are there any risks associated with the chlorination techniques?

Ans: : It depends on the reuse of the chlorinated water.



Swapnil Desai

Q 24: Will you propose some suggestions regarding treatment processes which may be implemented as most of the FSTPs are not meeting the standards with respect to removal of SS, TDS, TKN etc?

Ans: One way to reduce TKN is nitrification through aeration, followed by de-nitrification in anoxic tank. Appreciable removal of TSS and TDS may be achieved by treating water stream with flocculant and subsequent processing through sand and activated carbon filter.

Q 25: Have you measured the DBP like THM, especially for chlorination?

Ans: No.

Q 26: Coronavirus has been found in most of the STPs in Netherlands. A university scientist has developed a kit to test the samples. What will be our test methodology which will help us find it? How will RNA extraction from the sample be carried out?

Ans: There are commercial kits available for RNA extraction. Using qPCR (real time PCR), one can detect and quantify the viral RNA in wastewater.



Swastik Pandey

Q 27: What might be the reason behind high faecal coliform in Dhenkanal, even after tertiary treatment by sand, carbon filter and UV?

Ans: The exposure time to UV is also very important for reducing the pathogen load.



Vijai Kumar Chaurasia

Q 28: In wastewater treatment, performance suffers if there is shock loading. In an FSTP, it appears that whatever be the incoming sludge parameters, the result is always good. Comments.

Ans: In almost all the circumstances, the study was conducted when the FSTPs were running well below the process design capacity. In true sense, all the plants were under-utilised. Hence, there was no excess loading in the plant and as a result, the output was good. Few FSTPs were also newly constructed.

Q 29: Can you explain the process of vermin-filtration in the Kerala tiger bio-filtration plant?

Ans: The plant is designed to treat sludge and leachate simultaneously using tiger worm (earthworm). For more details, you may contact the operator in our report (to download, go to www.cseindia.org.)



Vikram Ammavasi

Q 30: Is there any method for treatment of the solid part out of the leachate?

Ans: A few FSTPs are successfully using co-composting with agri-waste (Ketti, Adigaratty at Coonoor and Karunughuzy in Chennai), vermi-composting (Wayanad), and pyrolysis to make bio-char (Warangal).

Q 31: Is the sludge being used anywhere for indirect potable reuse?

Ans: As far as we know, it is not.



Anonymous attendee

Q 32: Since faecal sludge is variable, don't you think the outlet should be sampled after the cycle of faecal sludge in the plant is complete?

Ans: In most treatment plants, the sample collection is done in the same way. Data from multiple months can overcome that anomaly.

Q 33: After analysing performance indicators from FSTPs, what could be some of the new reuse mechanisms that are possible (beyond using treated water for landscaping and irrigation for select crops)?

Ans: Some FSTPs are using the treated water for co-composting purposes

Q 34: Does the design and working of an FSTP differ considering the atmospheric conditions in an area? How?

Ans:No specific conclusion can be made on this aspect – but we hope further studies will help us understand the reasons for variations in effluents/sludge and performance.




Performance Evaluation: How Faecal Sludge Treatment Plants are Performing
Dr. Vinod Vijayan
Audio clip
The Announcement