Nesapakkam STP, Chennai

Location: Near Jafferkhanpet

Designed Capacity: 117MLD (Design)
95-100 MLD (Actual, dependent on season)

Scale: Zonal

STP operational since: 1974

Implementing Organisation: Greater Chennai Municipal Corporation

Co- treatment operational since:2006

Area: 45 acres

Capital Cost for co-treatment: INR 20 Million

Project Background
Chennai initiated co-treatment of septage at STPs in the early 2000s. At present, co-treatment is
being undertaken at three locations namely, Nesapakkam, Perungudi and Kodungaiyur. (Table 2)
Nesapakkam services the south western part of the city, Perunguddi services the southern part of
the city and Kodungaiyur services the northern part of the city. This study on co-treatment of
septage at STPs focuses on the Nesapakkam site.
Treatment technology
The original technology installed in the system was Activated Sludge process, however to use co-treatment the following component has been added:

  • Decanting Station: A decanting station has been created at the Nesapakkam STP to allow desludging trucks to discharge septage loads. This is in line with the recommendations of the “Operative Guidelines for Septage Management for Urban and Rural Local Bodies” issued by GoTN. Although located within the STP complex, the decanting facility has a separate entrance which is easily accessible from the main road and is enclosed prohibiting access to the rest of the STP. The trucks are permitted entry between 5 am and 5 pm every day except on Sundays and government holidays. The trucks come mostly between 5-8 am and 11-5 pm as they are not allowed to operate in the city during 8-11 am. The decanting station has sufficient space for up to four desludging trucks to decant simultaneously and has ample parking area for another three to four trucks.
  • The decanting station comprises of a covered receiving tank followed by grit removal chamber and screens. The receiving tank is covered and connected to an odour control air scrubbing unit. Septage from the receiving tank flows into the trunk sewer line passing outside the decanting facility and flows into the terminal SPS feeding into the STP. The decanting station also has a CCD monitoring system which is yet to be operational
  • The decanting facility (as well as the STP) is located in a residential neighbourhood. The entry to the decanting facility is located directly across a large residential complex. Odour control and aesthetics are therefore key concerns for the plant personnel in order to ensure that there are no objections from the residents. The plant is investing in upgrading the decanting facility to address these concerns and has incorporated the following features into the design:

1. Odour control unit connected to the receiving tank
2. High compound walls for the decanting facility
3. Greenbelt development within the STP (plants that absorb bad odour have been planted)
4. Discharge of septage directly into pits connected to the receiving tank to minimize scope for spillage

Business model
The main driver for initiating co-treatment was to put an end to the practice of unauthorised dumping of septage into the city’s waterways by private operators involved in desludging septic tanks which exist in areas that are not yet covered by UGSS. The CMWSSB started accepting discharge of septage at their STPs (three locations, Nesapakkam, Perungudi and Kodungaiyur)
offering to treat the same at a nominal cost (of INR 100 per lorry per trip) in order to incentivise
Registration Fee: The private desludging trucks are charged a one-time registration fee of INR 2000per truck. This amounts to be about INR 0.1 million per annum.
Currently the number of trucks registered with the STP are 52, making approximately 200 trips per day

Tipping Fee: Fee of INR 100 is charged per trip for disposal of septage at the STP. The truck owners
deposit this amount with CMWSSB. The trucks are allowed access to the STP only after showing the
payment receipt. Most operators / truck drivers make advance payments as a lump sum amount.
The tipping fee collections are appr oximately INR 6 million per annum

Type of charge


Rate (in INR)

Annual Collections


One-time payment

INR 2000


User Fee

Per trip, payment made in

INR 100 per trip


Contact person:
G. Sathiamurthi
Chief Engineer (O&M) II

*This study has been adapted from a study conducted by Mr. Sanjay Gupta, Independent consultant,