Even as Karnataka readies 165 new sewage treatment plants (STPs), underutilisation of the existing STP infrastructure is a limitation that calls for new treatment and supply strategies, experts say. They said capacity gaps, design flaws, consumer non-compliance and limited applications of treated water have all contributed to underutilisation of installed capacity.
Karnataka has 168 state-run STPs with an existing installed capacity of 2787.213 MLD (million litres per day), of which a capacity of 1931.11 MLD is being utilised. The state also has 45 STPs on 17 polluted river stretches through which 531.33 MLD of sewage out of the installed capacity of 822 MLD is treated. With a capacity utlisation gap of over 30%, the state needs new strategies to optimise its STP potential, including a comprehensive plan for reusing treated water, a senior official in Karnataka State Pollution Control Board (KSPCB) said.
Karnataka has 70 STPs under construction, with a capacity of 421.13 MLD. Apart from these, 95 STPs of 263.67 MLD capacity are proposed.
The official said work on incomplete underground drainage (UGD) networks that limit the flow to the STPs – a detailed, delay-prone activity – needed to be taken up to complement installation of additional capacity.
He said considering the pace at which some of the UGD works progressed, the STPs became ineffective by the time the drainage lines were connected.
The STP designs that fail to factor in future volumes have led to utilisation gaps.
“There are also cases where UGD lines are functional, but there’s no sewage flow as the house service connections (HSCs) are not in place,” the official told DH.
Vikas Brahmavar, founder-CEO of water utility company Boson White Water, said decentralising STP networks was the solution. “A capital-intensive project on UGD lines could be taken up as a long-term option but the pace at Bengaluru is growing leaves us with no waiting time. The viable approach involves decentralising STPs and devising cost-effective models to reuse treated water,” he said.
Vikas said decentralisation could ensure that supply channels remained sustainable.
The official said lake development initiatives also needed to expand scope beyond desilting, removal of encroachments and landscaping – which are essentially civil works – to focus on installation of STPs near lakes.