8 KLD Decentralized Wastewater Treatment System (DWWTs) at CSE Head Quarters, New Delhi


Scale of service


Area of installation (Sq-m)

60 Sq-m

Year of Installation


Capital cost

2.25 Lakhs (2005) + 1.0 Lakh additional for vortex


Centre for Science and Environment,Tughlakabad Institutional Area, New Delhi

Operational & Maintenance cost

 Rs. 25K – 30K per annum

Implementing Agency

Centre for Science and Environment (CSE)

Design Capacity


The Decentralized Wastewater Treatment system (DWWTs) at CSE HQ, implemented in 2005, has been designed to treat 8000 litres of wastewater on daily basis. This is based on the assumption that at any given moment at least 150-200 persons would be occupying the premises. CSE has setup this system as a demonstrative project which is being used for the advocacy of decentralized nature based solutions. The treatment modules include a settler, an anaerobic baffled reactor (ABR) with filters, a planted gravel filter (PGF) bed and an additional unit called vortex system. The treated wastewater is stored in an underground sump and is used for horticulture purposes within CSE’s premises.

Wastewater is tapped from the cafeteria and toilets of one of the CSE building.

Grease trap:  The canteen’s grey water is put through a grease trap to separate oil and grease. It has two chambers which provides sufficient time for the oil layer to separate from grey water. The vegetable peels and other solids get trapped in the mesh bag provided over the inlet pipe of the oil and grease trap.

Settler: After the oil separation, grey water enters into the settler for primary treatment. This settler is a two chambered module that offers enough time for the suspended particles present in greywater to settle down under gravity. The black water from toilets at CSE is taken separately into a separate two chambered settler where it undergoes similar process.

Anaerobic Baffled Reactor (ABR): The black water enters the ABR after the settler. The ABR at CSE consists of 10 chambers with the 8th and the 9th chamber having filter materials (pebbles). The wastewater from settler flow into the ABR from chamber to chamber. ABR offers secondary level of treatment wherein the anaerobic microbes degrade the contaminants. Remaining solids settle down and form the sludge blanket. The filter layer restricts the sludge to escape from the ABR. This settled sludge is retained in the ABR and helps in further biological degradation as it has rich microbial content. The retention time of water inside the ABR is 24 hours.

Horizontal Planted Gravel Filter Bed (PGF): Black water and grey water passing through a mixing chamber enters into the horizontal planted filter bed for tertiary treatment. This is mainly to remove the excess nutrients in the treated wastewater. A Horizontal Planted Gravel Filter Bed is a rectangular concrete bed of dimensions 22m x 2m x 1m and filled with different sized filter materials (Gravels and Pebbles) upto 0.6m. The bed has Canna Indica plants grown over the surface that supports removal of nutrients (nitrogen and phosphorus) from the wastewater. The slope of the bed is 1% that ensures gravitational flow. .

Vortex System: The treated wastewater from the PGF is stored in a collection tank and further passes through a vortex system which helps in the removal of foul smell and odour. This treated wastewater is stored in the collection tank and through 1HP submersible pump is used for horticulture requirements of the institute.


Result of Physico-chemical and Microbiological parameters (September 2019)

S No

Sample Location


TS ± Error % (95% C.I.) (mg/L)

TDS ± Error % (95% C.I.) (mg/L)

TSS* ± Error % (95% C.I.) (mg/L)

COD ± Error % (95% C.I.) (mg/L)

BOD (mg/L)

CPCB Standards for effluent discharge (w.e.f. Oct 13th, 2017)


< 2100


< 50


< 30



7.75 ± 0.2%

1335.0 ± 3.1%

1080.0 ± 0.8%

255.0 ± 3.9%

184.0 ± 3.8%



ABR Middle Chamber

7.69 ± 0.2%

1210.0 ± 3.1%

910.0 ± 0.8%

240.0 ± 3.9%

114.0 ± 0.8%



Effluent from Vortex

7.73 ± 0.2%

879.0 ± 3.1%

791.0 ± 0.8%

88.0 ± 3.9%

38.0 ± 4.4%


S No

Sample Location

TKN ± Error % (95% C.I.) (mg/L)

Ammoniacal Nitrogen ± Error % (95% C.I.) (mg/L)

Total Phosphate ± Error % (95% C.I.) (mg/L)

Fecal coliform (MPN/100 ml)


CPCB Standards for effluent discharge (w.e.f. Oct 13th, 2017)


< 50

< 4.5

< 1000




125.8 ± 2.4%

112.88 ± 0.5%

8.2 ± 2.8%

4.3 x 106



ABR Middle Chamber

120.8 ± 2.4%

111.12 ± 0.5%

5.1 ± 2.8%

1.5 x 104



Effluent from Vortex

3.9 ± 5%

3.62 ± 3%

2.2 ± 8.7%

9.3 x 103


Dr. Mahreen Matto
Programme Manager
Water Unit (CSE)                 
Mobile No: +91 9868018045
Email Id: mahreen@cseindia.org