It is sad, but common knowledge today that the city’s sewage ultimately ends up in the nearest lake or water body. In principle, the sewage from our homes should go to the pumping station via an underground sewerage connection. From the pumping station, this sewage should travel to the Sewage Treatment Plants (STPs), the primary function of which is to treat the sewage water through aerators, clarifiers etc.
A study conducted by Arappor Iyakkam shows that untreated sewage water from different parts of the city are being let out in the three rivers—Adyar, Cooum and Kosasthalaiyar, apart from the lakes and Buckingham Canal.
The Arappor Iyakkam team audited 27 pumping stations spread across the city to understand the sewage treatment process and came up with a conclusion that 10 pumping stations release sewage directly into the water bodies. 9 out of these 10 pumping stations are situated in north Chennai.
The audit findings also revealed the underestimation of the amount of sewage the city generates. Putting data into perspective, the audit stated that close to 2400 MLD of water is used in Chennai every day. 80% of this turns into sewage which would translate to around 1952 MLD of sewage a day.
“Considering the actual sewage generated by the city, a mere 12 STPs cannot be enough, we might need 10 additional STPs,” said Jayaram Venkatesan, Convenor of Arappor Iyakkam.
So in the absence of adequate sewage treatment infrastructure, what is happening to the quantum generated?
Contamination of Chennai lakes with sewage
According to a report of the Centre for Science and Environment in New Delhi, Chennai had more than 600 small water bodies in the 1980s. Yet, the city experienced severe water crisis in 2017. There is ample water in some lakes, but most activists and environmentalists point out that it is unfit for domestic consumption due to severe chemical contamination. As per the revelations of the Central Pollution Control Board (CPCB), 80% of water pollution is caused by domestic sewage.
Lakes have a flood discharge channel through which the excess water goes to the next lake, thus preventing flooding and aids in storing water. The contamination of water bodies with sewage has completely destroyed this natural recharge system which explains the drought, even after the rains in December 2015.
Located off the city, the lake in Sithalapakkam is now a like a reservoir of sewage water from neighbouring localities. Due to the absence of an underground sewerage system and effective STPs, the sewage is diverted to the lake and the Town Panchayat is unable to do anything practically due to lack of funds and awareness. One can even spot a sewer manhole in the lake which catches the sewage from households.
“The canal connecting the lake is choked completely with single-use plastic. Amid all the clutter, the sewage travels through the canal and drains into the lake. The lake in Perumbakkam is also a victim of apathy and is totally surrounded by residential areas and the sewage directly drains into this lake, as well, illegally,” comments Kumaran Mahalingam, a geologist and paddler based in Chennai.
The Pallavaram Periya Eri running along Pallavaram – Thoraipakkam radial road is another lake that is being subjected to illegal sewage disposal and is one of the prime reasons for the slow obliteration of Pallavaram Periya Eri.
Talking about the Periya Eri, David Manohar, an activist adds, “In addition to sewage from the neighbourhood, tons are offloaded at the lake after dark by private tankers coming in from other areas and the Pallavaram municipality is yet to question or investigate the issue. There’s an apartment just behind my home that has around 80 tenants; due to infrastructural deficiency, they rely on private players to let off the sewage. To be honest, the municipality does not even possess proper mechanisms to treat the sewage and catch the perpetrators red-handed. A holistic plan must be in place and implemented for septage management.”
Sprawled across 990 acres, Korattur Lake is one of the biggest lakes in the city, interconnected with the Ambattur and Retteri Lakes. However the connecting channels are choked with sewage and contaminants. There are quite a few industries in the area, and much of the waste generated by the factories ends up in the lakes, though the Tamil Nadu Pollution Control Board (TNPCB) norms dictate industrial sewage must be treated in the premises of the industries with private STPs before letting the water into the lakes. In addition to industrial effluents, many of the households are yet to link their sewage channels with the underground sewerage system, even where it exists.
“The contamination begins right from Ambattur Lake; residential sewage and industrial sewage from Thirumullaivoil are discharged into the lake which is then carried over to Korattur Lake through the outlet. The outlet of the lake then passes through the Ambattur Industrial Estate which collects sewage from Ambattur and the Estate premises. The excess water from Korattur Lake gets drained in Retteri Lake and Otteri Nullah,” said Harris Sultan of Arappor Iyakkam who audited all the three lakes in 2017.
In an attempt to reclaim the lake and prevent further contamination, the entrance point to the lake in north Korattur was closed for some time and was re-opened in December due to excessive inundation in 2015. Post floods, the surplus channel was closed, to be opened again during the rains at the 2016 cyclone.
Post 2015, however, the channels had been planned to be widened, desilted and reconstructed in concrete, a project with a planned completion date of 2018.
“The surplus channel renovation is not even halfway, I suppose. The authorities have failed in reclaiming the lake and are involved in opening and closing the water channels, as and when required,” added Harris.
Despite the above realities, however, S Dayalan, Superintending Engineer (Wastewater Treatment and Reuse) of Chennai Metrowater Supply and Sewerage Board (CMWSSB) said that all STPs except the 80 MLD plant in Kodungaiyur function to the fullest. He further claims that the TNPCB regularly monitors the treated water and concludes that it is within the permissible limit.
Projects to manage wastewater underway
The CMWSSB says that it has initiated set-up of an underground sewerage system (UGSS) in several parts of the city. By 2018, Perungudi is likely to get its own UGSS. In addition to the 12 existing STPs, the CMWSSB is also in the process of installing new plants in Thiruvottriyur and Sholinganallur. The 18 MLD plant in Sholinganallur is close to completion and will be commissioned in six months. The other plant in Sholinganallur with 54 MLD capacity and 31 MLD in Thiruvottriyur will be completed in a year or so.
“The STPs are designed in such a way that it can withstand the load and function even if the city generates more sewage in the future. As per Arappor Iyakkam’s findings, we are working to digitize the entire system so that anyone can check the sewage inflow, outflow etc. on our website. We are also working to fix the damaged parts for which a budget has been prepared and waiting for a Detailed Project Report (DPR) from the concerned consultancy,” said S Dayalan.
However, Jayaram of Arappor Iyakkam says, “Post audit, we have not observed any major changes. The officials have still not accepted the amount of sewage generated by the city. We have been insisting upon provisions to install an online monitoring system so that there is more transparency on the volume and nature of contamination, but there has been no response, even from the TNPCB. We plan to take the issue to National Green Tribunal in some time.”