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Wednesday 23 August 2017
News updated at 3:07 PM IST

Waste water worries

Rasheed Kappan, Bengaluru, Feb 5, 2017, DHNS 2:44 IST
Wonder why Bengaluru’s lakes remain so hopelessly polluted and dead? Blame the notoriously inefficient systems set up to treat the enormous volumes of waste water generated by the city. If this is not addressed on priority, will big Master Plans and decentralised treatment work?

This question agitates every Bengalurean invited to respond to the grand ideas put forth by the Revised Master Plan (RMP) 2031. When the new Plan talks about more Sewage Treatment Plants (STPs) and mandating apartment owners to treat their waste water themselves, they ask: Why did the old plan fail?

Completion of the underground drainage (UGD) network was high on RMP 2015’s priority list. But today, the UGD network on the city’s outlying areas is complete only in stretches. Implication: Huge gaps in the network, leading to direct flow of untreated sewage into the lakes.

This problem, as Ajit Sequeira from Whitefield Rising points out, is acutely pronounced in Mahadevapura, where the UGD lines end up in Varthur lake. There is no sign of any STP to let only treated water into the lake.

Untreated sewage inflow
An apartment dweller himself, Sequeira is convinced that the direct entry of waste water is the prime reason for Varthur lake’s perennial pollution. The lake attracts attention only when it froths, but the underlying reasons are ignored.

The RMP 2031 talks about big STPs with cursory mention of the inefficiencies of the existing plants. But why not opt for low-cost mini STPs that are energy efficient, wonders Sequeira. “Spending just about Rs 2 crore, such mini plants could be put up at every inlet into a lake. This would be more feasible.”

Both the Master Plan and the Bengaluru Blueprint stress on decentralising waste water treatment. They insist on plants to be installed in apartments, campuses, industries and commercial establishments. But apartment residents have been reluctant, citing problems of high maintenance costs and space.

The way forward, as Bengaluru Blueprint Action Group member V Ravichandar explains, is to incentivise citizens and not penalise them. “The government could encourage those with STPs through, for instance, a rebate on the water bill,” he says.
Incentive model

Retro-fitting older apartments with STPs can be an option if the incentives model is adopted. “They should also be allowed to sell the excess treated water, catering to neighbourhood requirements. This way, the STPs will find better acceptance.”

Acceptability could also improve if the STP maintenance costs are low. Builders, say residents, should construct STPs that are easier and cheaper to maintain. New technologies are available. But most builders will not opt for them as they often require more land, points out a Mahadevapura resident.

But what about the existing STPs maintained by the Bangalore Water Supply and Sewerage Board (BWSSB)? The Master Plan does hint at the inefficiency, but there is no elaboration about why it is so.

Here’s what it says: “As of 2015, there are 17 STPs with an installed capacity of 721 MLD against the requirement of 980 MLD. However, only three-fourth of the installed capacity is being utilised as of today to treat the waste water of the city.”

Sewers inside SWDs

About 35% of the sewers in the city run inside the stormwater drains (SWDs), and this is the fundamental cause, reasons former BWSSB Chief Engineer, M N Thippeswamy. “A third of the sewers, including the lateral, sub-main and main trunk sewers, are inside the SWDs. While the drains are desilted, the sewer lines are damaged,” he explains.

Crown corrosion of the sewer pipes is another factor. “The bio-solids in the waste water combine with moisture for form sulphuric acid which corrodes the pipes. In effect, due to the leakage, the volume of sewage getting into the STPs gets reduced. The new STPs under Cauvery 4th stage are not getting adequate flow,” says Thippeswamy.

STPs in the pipeline

The Master Plan says 11 more STPs with an overall capacity of 339 MLD are under construction. Another eight STPs with overall capacity of 550 are under tendering process. BWSSB has proposed to construct STPs of another 207 MLD capacity at 16 locations.

But, without a mindset of sustainability in planning, what is the guarantee that these additional capacities will address the city’s waste water problem? “The concept of reuse and recycling of waste water is still not integrated in the planning process,” contends Ravichander.

Result: Demand for recycled/tertiary treated water has remained low-key. Apartments with their own STPs use even secondary treated water for gardening and flushing. Due to the zero-discharge rule, they cannot let the treated water into the UGDs, but shift the excess water to construction sites in tankers.

BWSSB, despite advertising supply of tertiary treated water, had found the demand poor from even the construction industry. The Kempegowda International Airport (KIA) remains the only big user of this water today, although the RMP-2031 estimates the treated water availability to be 2,412 Million Litres Daily (MLD) in the next 14 years.

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