Case Studies

Initial state

North Chennai has historically been the hub for manufacturing activities and in the last decade, is considered an area of stagnant growth with a sizeable and burgeoning population.

However, due to inadequate wastewater management infrastructure, the exploding population which is labour oriented started facing a lot of health and environment issues. This was hampering the productivity of the population and the economic progress of the region.

Challenges

Development of a sustainable wastewater infrastructure for North Chennai which will ensure the safe discharge of treated sewage after removal of the contaminants for replenishing the nearby water bodies.

The solution

Chennai Metro Water Supply and Sewage Board decided to set up a first of its kind sewage treatment plant at Kodungaiyur and VA Tech WABAG was entrusted with the turnkey realization of a new biological sewage treatment plant being the reliable and trusted partner of CMWSSB for developing sustainable water infrastructure.

The contract assigned to VA TECH WABAG was on Design-Build-Operate mode in the year 2003 and was successfully commissioned in the year 2006 with a capacity of treating 110 million liters of sewage per day.

Technologies

The entire plant operates in two different stages. The first stage ensures safe discharge of treated sewage through an aerobic process. Whereas in the stage phase the sludge is treated through an advanced anaerobic process to generate green power from bio-gas and thus makes the plant power neutral, i.e. on self-sustaining basis without depending on grid power.

The plant handles 110 MLD (million liters per day) of sewage and the treatment process is based on activated sludge process with anaerobic sludge digestion and biogas utilisation by means of a power plant based on gas engine (capacity 1,317 KVA). After commissioning in 2006, WABAG also assumed responsibility for operations & maintenance of the plant for over a period of 12 years. It is the largest plant of its kind in India and the most energy efficient one among the 9 STPs in Chennai – achieving 98% self-sufficiency in terms of power consumption.

Comprehensive technical and economic know-how of WABAG has guaranteed efficient project realization and a highly commendable operations phase of the plant for over a decade. The Kodungaiyur STP has the distinction of completing maximum hours of run time with a single gas engine, which has run successfully for over 90,000 operating hours with producing over 50,000 MWh over the last 12 years.

In line with Govt. Policies

• MNRE (Ministry for New and Renewable Energy) programme offering subsidy to utilities and operators for setting up green power generation units inside WWTPs
• CPCB (Central Pollution Control Board) circular to all SPCBs (State Pollution Control Boards) mandating green power production from methane present in biogas produced through anaerobic digestion of sludge
• India’s ratification at COP 21 Paris Climate Convention to satisfy 40% of its energy requirements from non-fossil sources to reduce carbon emission

Key Highlights

• One of the largest Power Neutral Plant of India and achieves 98% self-sufficiency in terms of power consumption.
• Enables reuse of treated wastewater to reduce the burden on freshwater- relevant especially in a city like Chennai which depends on groundwater. Supplies 21 MLD of Treated Sewage to nearby Chennai Petro Chemicals Limited & 5 MLD of treated Sewage to Manali Petro Chemicals for industrial uses.
• 84 MLD treated wastewater routed to nearby Buckingham canal reducing environment pollution.
• Silt generated from Inlet chamber is being used to raise the entire low lying area of the plant.

Conclusion

There are many time tested and successful case studies in India which testify to the viability of power neutral STPs. Kodungaiyur set a precedent in this novel concept. The plant stands as a role model plant for “Comprehensive Sewage Treatment” which focuses on resource recovery with the conviction that “Sewage is a resource with economic value, not a liability.