Chennai Mertopolitan Water Supply and Sewage Board (CMWSSB) responsible for development and regulation of water supply and sewage services in Chennai. CMWSSB commissioned a 40 MLD Sewage Treatment Plant (STP) at Nesapakkam under the Chennai City River conservation project (CCRCP).

The joint team of HDO and BHEL were awarded this project, with BHEL responsible for civil and HDO for rest of EPC. Activated Sludge Process (ASP) was adopted. This served the dual purpose of combating the environmentally damaging greenhouse gases generated as biogas from the sewage sludge and using it as fuel for grenration of electric power.

The Project comprised of:

• Inlet screen chamber
• Screen chambers
• Detritus tank
• Parshall flume
• Primary & secondary clarifiers
• Aeration tanks
• Secondary clarifiers
• Sludge thickeners
• Raw sludge pump house, digestors, sludge mixing systems, Gas holding tank, gas burner room, administrative cum lab building, thickened sludge pump house, centrifuge platform, supernatant & centrate pump house, all necessary channels, sumps, sludge dewatering unit, bypass channel, electric substation, MCC rooms & control room & miscellaneous work.

Accomplishments:

• Successfully introduced of new technology for thickening, anaerobic digestion and dewatering of sludge
• Power generation from biogas generated in the Sewage treatment plant significantly reduced the electricity bought form from state electricity board. According to estimates cost saving per month at Rs.3.50/ kWh is approximately 5.25 lakhs
• Secondary effluent treated from STP was used for irrigation; for cultivation of paragrass which was auctioned each year