Hardlook: Mumbai’s woefully inadequate sewage treatment plants need to be upgraded immediatelyhttps://indianexpress.com/article/cities/mumbai/mumbai-sewage-disposal-mithi-river-bmc-ngt-neeri-5599336/

Hardlook: Mumbai’s woefully inadequate sewage treatment plants need to be upgraded immediately

Over the last 10 years, implementation of the Mumbai Sewage Disposal Project-II has virtually come to a standstill. Amid this, the NGT has stayed an MoEF notification on norms for STPs, which is likely to further delay BMC’s plan to modernise these plants.

Mumbai sewage, Mumbai sewage treatment, Mithi river, BMC sevage treatment, NGT, Mumbai Sewage Disposal Project-II , Sewage Mumbai, Mumbai Sewage disposal, Mithi river pollution, Mumbai rivers, Arabian sea mumbai sewage, BOD, TSS, BMC Sewage plants, Indian express, latest news
A nullah in Dharavi which joins the Mithi river. (Express photo:Amit Chakravarty)

In 2018, when Pune-based activist Nitin Shankar Deshpande approached the National Green Tribunal (NGT) against a Ministry of Environment, Forest and Climate Change (MoEF) notification issued on October 13, 2017 for required standards for Biochemical Oxygen Demand (BOD) and Total Solid Suspended (TSS) for Sewage Treatment Plants (STPs), the Brihanmumbai Municipal Corporation hardly saw what was coming.

Deshpande’s case was that in its 2015 draft notification, the MoEF had laid down discharge norms of 10 mg/l of BOD and 20 mg/l of TSS as optimal for the health of water bodies, but relaxed the norms in the 2017 notification to 20 mg/l for BOD and 50 mg/l for TSS. He alleged the dilution of norms had left the water bodies at the mercy of increased pollution. The NGT ordered a stay on the notification on December 21, 2018 and asked experts from the CPCB, NEERI and IIT to prepare a report and submit it before March 31, 2019. The next hearing in the case will be on April 16, 2019.

For the BMC, that meant putting on hold its plan of awarding contracts for construction and upgradation of five STPs (Worli, Bandra, Versova, Ghatkopar and Bhandup) across the city out of a total seven plants. While work on upgradation of the Colaba STP had already begun, another proposed STP at Malad did not get environment clearance as it would require destruction of mangroves.

Mumbai sewage, Mumbai sewage treatment, Mithi river, BMC sevage treatment, NGT, Mumbai Sewage Disposal Project-II , Sewage Mumbai, Mumbai Sewage disposal, Mithi river pollution, Mumbai rivers, Arabian sea mumbai sewage, BOD, TSS, BMC Sewage plants, Indian express, latest news
A nullah in Dharavi which joins the Mithi river. (Express photo:Amit Chakravarty)

The stay could force the BMC to re-invite tenders with changed norms that will delay the upgradation of STPs even if it holds the promise of super-clean treated sewage. But the real problem is not this delay. It is, as BMC officials themselves concede, the entire work of upgradation of Mumbai’s woefully inadequate sewage treatment plants, which are at least 15 years behind time.

Advertising

Under its 1999 Mumbai Sewage Disposal Project-II that was planned for the first three decades of the new millennium, the BMC was supposed to have implemented projects for rehabilitation, repairs, augmentation of sewer lines, laying of new sewer lines for covering the entire city and its suburbs, upgradation of sewage pumping stations and STPs. But over the last 10 years, the implementation of MSDP-II has been at a virtual standstill.

The results are no secret. In the last few years, several studies by government institutions have highlighted the poor condition of the sea off Mumbai and in its creeks. According to a 2017 Maharashtra Pollution Control Board (MPCB) report, the water quality index (WQI) near Girgaum Chowpatty, Nariman Point, Juhu Chowpatty, Dadar, Worli sea face, Mahim Bay and Malabar Hill were found to be ‘bad’ and at Mithi river and Versova beach ‘very bad’, confirming scientifically what people knew just from the stink.

A 2016 NEERI report for MSDP-II project confirmed the deterioration of the water quality off the west coast and Thane creek. Another report prepared by The Energy and Resources Institute (TERI) for the MPCB in 2015-16 had also highlighted that water samples taken at 12 locations along Mumbai’s coast had shown WQI as consistently ‘bad’. However, in 2018, the MPCB claimed a sudden turnaround. The WQI was reported to be ‘good’ to ‘medium’ on the basis of sample collected at 12 locations across the city. The MPCB findings drew criticism from environmentalists and activists, who alleged the findings were ‘manipulated’ to show improvements.

As per Central Pollution Control Board (CPCB) norms, marine life needs BOD of less than 20 milligram per litre (mg/l) to survive. The 11.8-km Mithi river is alone a big source of pollution entering the sea. Mithi carries waste and raw sewage from domestic, commercial and industrial establishments along its banks and dumps it straight in the sea with no treatment whatsoever. The WQI of Mithi has been found to be ‘very poor’ with BOD level of 250 mg/l.

Moreover, Mumbai’s storm water drain (SWD) network, meant only to carry rainwater, is connected with illegal sewerage lines. According to the BMC survey, over 76,400 properties have been illegally connected to SWDs, open nullahs and creeks. This leads to huge quantity of sewage being dumped into the sea or creek without any treatment via SWD pumping stations.

Y B Sontakke, Joint Director (Water Quality), MPCB, said there was more pollution in the creeks than in the sea, where dilution takes place constantly. “The major problem is untreated or primary level treated sewage discharged in creeks. Recent studies show there is no major impact in the sea. Any pollution in any water body is definitely affecting it. But in the sea the pollution is very less compared to creeks. Since some STPs have deep sea marine outfalls they get enough dilution, so there is very little impact in the sea.”

Another MPCB official said, “The BMC has delayed the project. Irrespective of the discharge norms, the civic body could have decentralised the STPs and constructed small ones to deal with sewage treatment. The BMC wanted a complete sewerage system and modernised STPs but that will take a long time. Mumbai is a big city and if it had taken small, small steps in sewage treatment then the situation would have been much better.”

The official said, “We can’t sit and say the project is not happening because of land issue, environment clearances or some other reasons. The BMC could have done ward-wise STPs and the recycled water from that could have been used for non-potable purposes.”

Meanwhile, MSDP-II has seen a three-time increase from its initial proposed cost of Rs 5,500 crore in 2009. The current proposed cost for upgradation of STPs and sewerage network is about Rs 15,000 crore. The BMC has also blamed changing effluent discharge norms by the CPCB, MoEF and environment clearances for the delay in project.

In 2015, the Comptroller and Auditor General (CAG) had slammed the civic body and its consultant, which was paid Rs 141 crore, for delaying the project and preparing faulty and deficient master plans. After CAG’s remarks, the BMC had issued notices to the consultant to recover the money and not to pay any remaining amount. Currently, the issue is with the arbitrator.

Environmentalist Stalin D, NGO Vanshakti, said, “The NGT has reverted to

earlier standards, which according to them were better. Tribunal order has not stopped anyone from going ahead with their work. They have told the corporation to follow old norms as they have standards to which they have to adhere.”

He added, “Also, the BMC’s argument that STPs with stringent norms carry a high financial cost is not right. Why is there reluctance when it comes to following pollution laws. You have Rs 60,000-70,000 crore for Metro, Rs 1 lakh crore for bullet train but you don’t have money to lay proper sewerage lines.”

Why BOD, TSS are important

Biochemical Oxygen Demand (BOD) stands for amount of oxygen needed by microorganisms in water to break down organic matter for their own food. A high BOD points to the presence of high amounts of sewage and other organic matter in the water and consequently a drop in oxygen levels, which makes it completely unsustainable for fish and other aquatic life.

Total Suspended Solid (TSS) is the portion of organic material that does not dissolve but remains suspended in the water. It provides hiding space for disease-causing micro-organisms, silting in water bodies and deterioration of water quality. Another important factor is Faecal Coliform (FC) that causes disease and epidemics such as diarrhoea, dysentery, cholera, gastroenteritis, hepatitis B etc.

As per norms set by the CPCB, a BOD level above 60 mg/l is harmful for aquatic life.

Explaining the effects of sewage on marine organisms, Vinayak Deshmukh, former principal scientist of Central Marine Fisheries Research Institute (CMFRI), said, “Sewage mainly contains human excrement. Raw sewage and primary treatment sewage contain extremely high bacteria and dangerous E-coli. They go untreated into the sea. They can spread various diseases like stomach upset, loose motion. Besides, bacterial infection can cause skin infections. Untreated sewage also contains extremely high levels of organic material. And this organic material provides food for all the bacteria. These bacteria consume the dissolved oxygen in the sea. So obviously the sea around the city has less oxygen.”

He said, “Less oxygen means other marine organisms like fish, crabs, small organisms like cat fish, shelled organisms are deprived of oxygen. They die because of no oxygen and when they die again their bodies are decomposed and bacteria eating these bodies consume lot of oxygen from water. At the end of that whole process what happens is, the sea water around the city is deoxygenated. And because of this deoxygenation, sulphur dioxide and hydrogen sulphate are produced. These gases are extremely pungent and release foul smell.”

Talking about the plight of marine biodiversity, Deshmukh said, “Generally, we never go into such water but marine organisms have no alternatives and finally they also die. In this process, what happens is, all the marine organisms are dead as the whole environment becomes very toxic, that is an end effect if sewage is not treated properly.”

Treatment: Then and now

The development of sewerage system in Mumbai dates back to 1867. The first section of the sewerage system was constructed in Colaba and Worli. The sewerage Master Plan-I was prepared in 1979 for 25 years and was completed in 2003 with help of World Bank.

Under it, seven sewerage zones were established — Colaba, Worli, Bandra, Versova, Malad, Bhandup and Ghatkopar — with primary level Sewage Treatment Plants (STPs). From these STPs sewage is discharged into the nearest natural water source (like creek, harbour or sea) after primary treatment, which means screening and de-gritting.

The existing sewerage infrastructure consist of 2,000 km of sewer lines, 40 satellite pumping stations and the seven STPs. The BMC collects 1,842 million litres sewage per day. But according to the Service Level Benchmark (SLB) set for municipal corporations by the Urban Development department, the total quantity of sewage of a city should be around 80 per cent of total drinking water supply. Currently, Mumbai gets 3,750 million litres of water supply per day.

“More than 2,700 million litres of raw or partially treated sewage is directly discharged into nullahs, sea or creek per day. Also the treated sewage from primary level STPs are far behind from the standard discharge norms. The Island City has proper sewerage connections but the suburbs have grown rapidly and unfortunately there have been very little sewerage networks as well as treatment facilities,” said a BMC official.

Moreover, western suburbs (Bandra to Dahisar), which have seen a huge increase in population in the last few years, do not have proper sewerage network and no treatment facility either. Raw sewage from these suburbs, with a population of 33 lakh, is going into the creeks directly.

‘Situation is alarming…marine biodiversity is almost non-existent’

Dr Rakesh Kumar, Director of National Environmental Engineering Research Institute (NEERI), associated with the Mumbai Sewage Disposal Project-II (MSDP-II) for planning and technical issues, says he is disappointed at the lack of progress in the project.

What have been the consequences of poor sewage management in the city? And to what extent is it affecting marine biodiversity and sea water quality?

The authorities need to hurry as the situation is alarming. There is impact on marine biodiversity and ecology. At places where dilution is not good, particularly in creeks like Malad and Thane, whatever biodiversity existed is all missing now. Discharge of raw and primary treated sewage is resulting in growth of mangroves, which is a negative indicator in such places. Along with mangroves, there should be also an increase in number of birds and fishes, but this is not happening. Mangroves are growing because nutrients of sewage are ideal for them. Sludge of sewage gives nutrients to the roots of mangroves.

For example, mangrove density in the Thane creek has increased and so more number of flamingos are coming there. The rise in number of flamingos is an indication that things are not good. There are bacteria and different types of insects present in the water and flamingos feed on them. Thane creek’s holding capacity has more sludge and silt and not enough water. Fishermen are not being able to catch fish and crabs unlike in the past.

On the western coast, like Versova, Malad creek is getting raw sewage. Sand on the beaches in that part of the city is black. The marine biodiversity is almost non-existent and only in the monsoon you can see some kind of creatures.

What is the future of coastal water?

All these are certain phases, especially in terms of sea water, which can be reversed if discharge quality is improved. The sea has strong dilution capacity and Mumbai is lucky since it has the sea on its side. Though the repair mechanism is different for creeks, the present damage can be reversed with timely intervention. If treatment takes place as per norms, then it can come back to normal over a period of time. It will not happen in one or two years. Only after a higher level of sewage treatment can the water become available for reuse.

It has been over a decade since the BMC planned MSDP-II but there has been hardly any progress. What happened?

Advertising

I have been associated with the BMC for MSDP-II since long and I am really disappointed with the progress. NEERI has been part of the civic body’s ambitious MSDP-II planning since 1999. But the authority has taken into consideration very few of our suggestions and has gone ahead with its own plans. There was no consistency. Also, we had suggested some small corrective measures like putting screens on drains to capture garbage but very little has been done. When MSDP-II was first planned, there was the thinking that discharge in creeks or nullah will be treated at higher level whereas discharges in sea through marine outfall can be subjected to standard level treatment because there is more dilution in sea. World over, it is the same procedure.