FAQs on TNUSSP2021-01-18T13:49:42+00:00

What is the technology/process used in Fecal Sludge Treatment Plants (FSTPs) in Tamil Nadu?2020-12-16T05:45:03+00:00

A non-mechanised system using a combination of sand drying beds and constructed wetlands is being adopted in Tamil Nadu. In some cases where there is a land constraint Tamil Nadu is using mechanised screw press for dewatering instead of sand drying bed.

What were the technologies used? Were all the 61 FSTPs using the same technology?2020-12-16T05:45:06+00:00

Though both mechanical and biological-based technology were used in TN, nonmechanised system using a combination of sand drying beds and constructed wetlands were used in most of the ULBs. Among the non-mechanised gravity based FSTPs, there were two variants of biological-based process used- in ULBs where fresh/ undigested fecal sludge (from Community toilets, hostels and other places where holding tanks collect fecal waste and have to be regularly emptied) was expected, fecal sludge stabilisation unit was included in the treatment process, whereas in other ULBs this is not present

Any consideration of non-sewered sanitation options currently?2020-12-16T05:44:58+00:00

The State of Tamil Nadu can be an example for consideration of non-sewered sanitation options. The State has a mix of both sewered and on-site sanitation systems (OSS). Considering over 45 per cent of the State’s urban population relies on on-site sanitation systems, the Government of Tamil Nadu (GoTN) recognised the importance of Fecal Sludge Management (FSM) (or non- sewered sanitation) as an economical and sustainable complement to networked sanitation systems. The State, therefore, adopted the Operative Guidelines for Septage Management in September 2014, and subsequently, in 2018, a State Investment Plan (SIP) for the creation of Fecal Sludge Treatment Plants (FSTP) and scaling of FSM. Currently, the GoTN is working on the implementation of FSTPs and scale up of non-sewered sanitation solutions across the State. The SIP can be accessed here.

What could be the possible set of criteria that would help decide the mix of technologies in different zones of a city?2020-11-19T09:16:00+00:00

Based on the technology assessment criteria prepared by TNUSSP, the following may
be the key considerations in choosing a technology:

  • Characteristics of fecal sludge in the city
  • Regulatory standards in place
  • Health and safety of workers
  • CAPEX and OPEX
  • Technology requirement such as power, human resources and efficiency
  • Land availability
  • Design and O & M considerations
  • Factors such as population, population density, terrain and ability of ULB to sustainably
    operate, also needs to be considered.

Mechanised screw press (at PNP): is this the Gates Foundation-supported Omniprocessor technology?2020-11-23T09:42:16+00:00

It is not the Omni processor technology, the process followed at PNP is as defined below:

  • Step 1: The septage is received in the septage receiving station (SRS) via screen. The grit settles in the SRS, and the septage flows into the storage tank.
  • Step 2: The septage homogenises in the collection tank. The three-day retention time in the collection tank is designed to address the incoming fresh septage from community toilets and public toilets too.
  • Step 3: Submersible sludge pumps are placed in the collection tank to pump the settled sludge from the collection tank to the sludge holding tank. Two pumps are placed in the first two sections of the holding tank, and one pump in the last two sections. About 65-70% of the sludge is pumped to the sludge holding tank. The rest of the supernatant overflows to the MBBR tank under gravity.
  • Step 4: The sludge from the sludge holding tank is pumped to the dewatering unit.
    The dewatering unit consists of:
    o Polymer mixing system
    o Polymer maturation tank
    o Polymer dosing system
    o Dewatering – volute press (2 nos.)

    The system is designed to handle the varying solids % in the sludge, and hence two volute press are provided. This also acts as a back-up in case of any maintenance requirements.

  • Step 5: The dewatered solids fall into the trailer placed on the ground and is taken away to the composting yard for further composting with the MSW organic fraction. The filtrate from the volute flows to the MBBR.
  • Step 6: The overflow from holding tank, and filtrate from volute is treated in theMBBR, and post the tertiary treatment, stored for use in the plant area in the treated water tank.
  • The overall turn-around time for septage is 4-5 days, from the day of receipt into the FSTP.
Have you thought of using a bio-product to enhance the efficiency of FSTP?2020-11-23T09:44:12+00:00

This has not been explored. TNUSSP is open to consider suggestions on this. Please write to us at tnussp@iihs.ac.in if there are any suggestions.

How does the O&M of FSTP and STP compare?2020-11-19T10:26:49+00:00

FSTPs and STPs use similar treatment processes, except that the volumes treated in FSTPs are low – (by a few orders of magnitude) and waste is likely to have higher solids/ sludge content.

Therefore, operational procedures and maintenance requirements are similar. There are a few changes due to the need for a receiving facility and testing of waste prior to accepting for treatment, etc

What happens to the fecal matter; process?2020-11-19T10:32:26+00:00

This depends on the technology adopted. The process adopted in most FSTPs in TN, in very simplistic terms, is as follows: the fecal matter gets digested and decomposed by microorganisms and is further dried before co-composting with municipal organic waste.

To what extent IT technology is used for monitoring FSM operations and ensuring quality control?2020-11-23T09:46:59+00:00

A mobile-based construction monitoring platform was configured with two checklists, one for stage based reporting of construction progress and the second for conformity of construction with design specifications and construction quality parameters. TSU field engineers periodically visiting sites used their mobile devices in the field to capture data and images that were uploaded to the platform.

A dashboard view was provided to state / regional level government officials to monitor the FSTP construction progress across the State at near real time. TSU was tasked with ensuring adherence to quality and timely escalation of issues to the local administration responsible for supervising construction activities. The systematic recording of information ensured private players were held accountable, both in terms of schedule and quality of construction.

To what extent Information Technology (IT) is used for monitoring FSM operations?2020-11-19T10:36:31+00:00

TNUSSP is currently exploring how IT can be used as part of FSM Operations such as digitising record-keeping at FSTPs/STPs.

How many co-treatment plants are in operation?2020-11-19T10:37:49+00:00

There 50 STPs in the State (other than STPs in the Chennai Corporation limits). TNUSSP has assessed 33 STPs, 20 of which practice co-treatment. It is envisaged to scale this up to all STPs in TN.

What is the performance of the co-treatment plants (STPs)?2020-11-19T10:39:26+00:00

As per TNUSSP assessment, most of the STPs practicing co-treatment meet the CPCB norms for effluent disposal. As per the assessment, most STPs are underutilised (capacity utilisation around 60 per cent). Therefore, optimum utilisation of the facilities is the priority. For a few STPs which had reported certain O&M issues, we are trying to understand and resolve them.

How do the co-treatment plants solutions compare with stand-alone solutions visa-vis performance and costs – capex and opex?2020-11-19T10:41:33+00:00

FSTPs are designed to treat fecal sludge while STPs are designed to treat wastewater collected through UGSS. Comparison of performance between FSTPs and STPs is yet to be explored in TN.

Capex for STPs generally is in the range of 2.5-7.5 Million INR (approximately 35,000-100,000 USD)1 per MLD treatment capacity. Opex generally varies from 3.0 – 3.3 INR per Kilo Litre. Capex for FSTPs varies from 0.9 -1.2 Million INR (approximately 12,000-16,500 USD) per KLD for FSTPs implemented in TN.

Are the 50 co-treatment plants and 61 FSTPs already operational? What is the operational experience in terms of Key Performance Indicators (KPIs)?2020-11-19T10:45:12+00:00

Around 20 STPs have started practicing co-treatment in the State. Of the 61 FSTPs 2 are operational, 4 are on trial run and the rest are under different stages of construction.

The quantity of fecal sludge being received for treatment is increasing regularly as FSM is getting formalised across the treatment plants.

How many cities have been implemented with Underground Sewage Systems in Tamil Nadu and how many are being planned?2020-11-19T10:46:40+00:00

At present, 43 ULBs have implemented UGSS in Tamil Nadu and 27 ULBs have planned for it.

Any publications or documents related to these co-treatment plants?2020-11-23T06:11:06+00:00

Our publications on co-treatment will be uploaded soon. Kindly keep checking the resources section at tnussp.co.in

What is the end use of FSTPs output in functioning plants in TN?2020-11-19T10:53:33+00:00

The end products of treatment can be divided as liquid stream and solid stream. In the liquid stream, the volume of treated water generated is in a few thousands of litres and can be used for gardening within FSTP premises. The treated solids can be used as manure for agriculture through co-composting with municipal solid waste or as fuel pellets.

Were there any resource recovery options operationalised in these examples?2020-11-19T10:55:32+00:00

Some of the FSTPs have already initiated co-composting. There is demand for treated water. Eventually, resource recovery will be scaled-up across all the FSTPs.

Any strategy to address the greywater, as it is different in quantity and quality compared to blackwater?2020-11-23T09:52:01+00:00

The Tamil Nadu government has come up with a wastewater re-use policy which covers greywater as well. Also TNCDBR, 2019 discusses greywater treatment strategy.

What can we do with purified water other than irrigation? Can you give your safe reuse techniques?2020-11-23T10:33:28+00:00

It can be used for groundwater recharge, hedge plantation, construction activities, and in industries for cooling and other secondary uses.

Can we link that with fertiliser company and produce urban manure?2020-11-19T11:06:58+00:00

It depends on the scalability and quantity of manure produced, along with the quality we can achieve. This is an evolving field. Urban manure production is an achievable outcome, though. Co-compost should follow FCO standards for organic compost.

Key measures taken with respect to containment systems and their rectification under TNUSSP?2020-11-20T11:20:05+00:00

As is widely accepted now, there is a wide variation in the containment system, and upgrading/ retrofitting these remain a critical challenge along the chain. Though our work on this front is still ongoing, it can be divided into the following components:

  • Exploring non-invasive technology for identification of issues such as cracks in existing OSS;
  • Assessing suitability of various OSS for different hydrological regions in the State
  • Technical options for improving functions of existing OSS, including low investment options and options for urban poor and
    Working with private sector for 3 above, and for disruptive innovations.

The work around containment is on-going. For specific queries, please write to:tnussp@iihs.ac.in

Retrofitting of septic tanks is being done as part of this? I’m sure it is. Who is funding it and what’s the methodology followed in terms of institutionalising it?2020-11-23T07:23:46+00:00

Existing on-site systems is an ongoing challenge where some action under SBM was taken in terms of conversion of insanitary latrines to sanitary ones. We are pushing for ULBs to ensure new construction conforms to IS standards and TN building rules. Retrofitting of existing septic tanks has been tried by TNUSSP on a pilot basis for understanding the feasibility. This is an evolving field; we are yet to reach any conclusions. For specific queries, please write to tnussp@iihs.ac.in.

In terms of institutionalisation, we ensure that new septic tanks are built according to standards, and thereby ensured that building bye-laws are aligned towards this. Please see suggested changes to Municipal Building Rules here.

Please also see response to question number 22

In many places, soak pits are named as septic tanks. How government or ULBs are going to regulate and monitor it?2020-11-23T07:29:44+00:00

In order to effect improvements across the sanitation chain, an assessment of the existing practices with respect to on-site containment structures was undertaken. While already existing on-site structures need to be surveyed to ensure compliance with sanitary requirements, and enforcement in this regard has been taken up by ULBs in Tamil Nadu, another intervention identified was improvements to the existing procedures for receiving and approving building proposals. A note summarising the review and the ensuing recommendations shared with the Government of Tamil Nadu which are under consideration can be accessed here.

Any thoughts on scheduled desludging? Is it a requirement or can it be designed for “as and when required?”2020-11-23T11:09:47+00:00

While it is important to desludge periodically, given the non-standard nature, dimensions and conditions of containment systems, implementing a scheduled desludging model can be quite complex. More importantly, Tamil Nadu has a robust demand-based desludging market led by private players. Therefore, the primary objective of the Government was to ensure safe disposal through minimal regulation of the desludging market, thereby minimising disruption and protecting existing businesses and livelihoods. The approach also promotes the usage of treatment facilities by reducing the financial burden on private operators.

However, alternate approaches are being explored for other customer segments. For example, scheduled/periodic desludging is being explored for Bulk Waste Generators such as community/public toilets.

Scheduled desludging is not a requirement for the success of FSM, but it is important to ensure that desludging operators are safely disposing collected waste in designated treatment facilities. Therefore, currently, the focus is on regulated desludging. More details on systems and procedures for urban sanitation in Tamil Nadu can be found here

Is there scheduled desludging practices? If yes in how many cities?2020-11-23T07:37:21+00:00

We are piloting scheduled desludging only for Bulk Waste Generators such as community/public toilets. Scheduled desludging is not a requirement for the success of FSM, but it is important to ensure that desludging operators are disposing collected waste in the designated areas. Therefore, currently, the focus is on regulated desludging. Please see these documents for the model for regulated desludging. Please also see response to question number 25.

What is the basis of selecting a cluster for FSTPs?2020-11-20T11:45:49+00:00

In the cluster approach, ULBs have been clustered around existing or proposed treatment facilities within an average travel distance of 10 kms to ensure sharing of treatment facilities within the cluster. The average travel distance has been arrived at after a survey of operators across TN which revealed that this distance works best for the existing business models of operators. This distance is a thumb rule, and may need to be modified based on local conditions e.g. hilly areas, crowded highways etc.

The clustering of ULBs optimises the investments required to provide treatment infrastructure, and ensures that the treatment facilities are most likely located at the bigger ULBs that have the capacity and resources to manage these facilities. More details on clustering can be accessed in our website.

“Light touch” regulation of private FSM service providers – Are more details on this available?2020-11-23T11:11:25+00:00

The GoTN has rolled out a Standard License Agreement (SLA) for desludging operators across ULBs in the State, which aims at optimal regulation of the private sector market without price interventions to address open dumping as well as promote worker safety. The SLA mandates desludging operators to adopt safe desludging and disposal practices. It promotes use of treatment facilities while keeping Tipping and License Fees at nominal rates to minimise disruption to existing market. The SLA also aims to increase awareness and training on Occupational Health Safety as well as improve access to Personal Protective Equipment. A copy of the Govt. Order can be accessed on our website here.

Is there a big advantage in this cluster system compared to traditional centralised system? What are the gains you made by opting this new strategy of FSM?2020-11-20T11:50:07+00:00