The wayward waste water

Blatant discharge of untreated sewage into the stormwater drains continue from lakhs of houses & industries. BWSSB’s STPs are no match.

Sewage. That’s something which Bangalore generates in hundreds of millions of litres every day. That’s one daunting task the city’s 14 Sewage Treatment Plants (STPs) can barely manage to clean up. But when 500 Million Litres per Day (MLD) of this waste water enter our lakes untreated, severely polluting our precious blue bodies, we ought to get deeply worried, angry, forcing us to stand up and ask: Why?

There is no escaping it. A whopping 80 per cent of the 1,155 Million Litres per Day (MLD) of Cauvery water pumped into Bangalore homes and industries gets out as waste! The city’s exponential population growth is bound to push up those volumes even more. Pushed to the wall, the Bangalore Water Supply and Sewerage Board (BWSSB) can only hope the 10 additional STPs – they have been in the pipeline for a long, long time – will address the rising challenge.

But it is not going to be easy. For decades, the Water Board could hardly stop the blatantly illegal outflow of sewage into the Storm Water Drains from lakhs of houses and industries. Let out directly into the open Raja Kaluves that criss-cross the City, the untreated waste water negates the very purpose of these lines: To channel the clean rainwater to the lakes.

The shoulder drains that run along either side of the roads, and wind their way into the Raja Kaluves are mostly clogged. Debris abound, utility pipes run through it, defeating its storm water drainage functionality and triggering flooding on roads. But underground, the sewage lines bear the weight of much more muck, let inside indiscriminately by the households.

Animal parts in sewage pipes

Tonnes of coconut shells, tyres, animal parts, construction debris and a mindboggling range of plastic waste are retrieved from the trunk sewers at the BWSSB’s Intermediate Sewage Pumping Stations (ISPS)s, before the filtered waste water is directed to the STPs. “We have even seen dead bodies,” recalls a senior Water Board official. Hardly aware about what should get into the drains and what should remain for overground garbage clearance, thousands of residents continue their clogging service!

The shocking pictures of man-holes right in the middle of the Raja Kaluves is another grim reminder of poor planning. As urban architects point out, these man-holes, made of bricks, develop cracks and are eventually dissolved in the canal water. The mixture of sewage and storm water is inevitable. “The man-holes shouldn’t have been there at all. Ideally, the sewer lines should be connected to Ovoid pipes on either side of the canals,” points out Naresh Venkataramanan, an architect.

Suggesting a redesign of the city’s sewer network and ideating a lot more on Bangalore’s general development projects, Naresh and other like-minded consultants are now consolidating all their efforts under an umbrella called “Imagine Bangalore.” This group is expected to get more active in proposing new models to BWSSB and other civic agencies. 

With the 10 new STPs likely to be commissioned only in 2015 and beyond, the largely unregulated inflow of untreated sewage into the lakes will continue to raise a stink. Besides, the proposal for an STP in Kachohalli has been shelved because there is no drainage infrastructure at all in the 110 villages added to the Bruhat Bangalore Mahanagara Palike (BBMP). Lake development is still in its infancy, and that would only mean widespread weed growth and eventual encroachment of these water bodies.

Inadequate treatment

Take the hugely polluted Bellandur lake for instance. It has an estimated 17 inlets of waste water, and just one inlet brings in treated water from the adjacent Koramangala & Chellagatta Valley STP in B Nagasandra. This Plant caters to incoming sewage from Koramangala, HSR Layout, BTM Layout and parts of JP Nagar, letting out about 190 MLD of treated water into the lake.

But since the lake is “like an ocean” as one official put it, this volume hardly makes a difference when 250 to 300 MLD of untreated sewage gets in directly through the 17 outlets! This startling picture finds its echo in lakes across the City.

The apartments around most lakes contribute heavily to the sewage inflow. Making a mockery of the rule which states that complexes with more than 50 housing units should have inhouse STPs, the builders directly connect the untreated sewage to the lakes. The nutrients in the untreated sewage help the growth of algae and weeds, reducing water, increasing silt and eventually leading to encroachments.

Encroachments, both authorized and illegal, have killed the centuries-old natural drainage system that once ensured sewerage and storm water flow by gravity beyond the city.

BWSSB now has to take recourse to pumping stations called ISPS to push the sewage onto STPs spread across the three principal valleys of Vrishabhavathi, Koramangala and Chellaghatta, a fourth Hebbal valley and five minor valleys including Kathriguppa, Tavarekere, Arkavathi, Kethamaranahally and Marathahalli. Lakes in these valleys are the main beneficiaries of the treated water outflow from the STPs.

The city’s extensive drainage network use stoneware pipes upto 300 mm diameter sizes, and RCC hume pipes varying in diameter from 300 mm to 2100 mm for sub-mains, mains and outfall sewers. The addition of 2,300 kms of new underground drainage pipes to 250 sqkm of the newly added BBMP areas under the Karnataka Municipal Reform Project (KMRP) will massively boost the sewage volumes. BWSSB officials say about 70 per cent of the work is complete.

Under the Environment Action Plans (EAPs), BWSSB also has the task of repairing and rehabilitating the existing underground lines in core Bangalore. The Board claims the works undertaken with JNNURM finances are close to completion.