Raising a stink over Mumbai’s polluted rivers

Published on Jun 02, 2022 12:36 AM IST

Mumbai: In 2016, when Sagar Vira and his eight-member family moved to the plush Hiranandani Heritage apartment complex in Kandivli, they were ecstatic about the new amenities — a large, gated community, a bigger garden, a clubhouse with a swimming pool

The Poisar river originates from the Sanjay Gandhi National Park and merges into the Arabian Sea via the Marve creek in Malad (HT PHOTO)
The Poisar river originates from the Sanjay Gandhi National Park and merges into the Arabian Sea via the Marve creek in Malad (HT PHOTO)

Mumbai: In 2016, when Sagar Vira and his eight-member family moved to the plush Hiranandani Heritage apartment complex in Kandivli, they were ecstatic about the new amenities — a large, gated community, a bigger garden, a clubhouse with a swimming pool. Their new home with three bedrooms met all their requirements, but one thing was a bother. A large sewer flowed right next to the complex. “The sewer was definitely an eyesore, but the property had so many positives that we decided to ignore this one negative point,” said Vira (45).

Five years down the line, Vira wishes they hadn’t. “We had not anticipated such a high amount of floating waste. We didn’t expect the mosquitoes to be such a menace. And we didn’t at all think about the foul smell that emanates from the sewer especially in the winter.”

The “sewer” Vira refers to is Poisar river — one of four that run through the dense suburbs of Mumbai as it makes it way to the Arabian sea. In many places, it can easily be mistaken for a sewer, which is a sign of how contaminated it is.

The Poisar river originates from the Sanjay Gandhi National Park and merges into the Arabian Sea via the Marve creek in Malad. The seven-kilometre-long river runs through slums. For decades, it has served as an open drain for solid and liquid waste, as informal settlements are often unconnected with or underserved by sewage pipelines. As a result, the city’s storm water drainage system, which comprises a hierarchical network of drains, nullahs and outfalls that discharge the surface run-off into the four rivers, are filled with plastic and other waste, including sewerage. The water in the Poisar river is black in many places; in the monsoon, it lightens to brown.

“I keep thinking that if this river was clean, clear and non-polluted, it would have been so calming and pleasant to look at every day,” said Vira.

A FOUL SMELL

“The city stinks, and we have stopped noticing it,” said Gopal Jhaveri, co-founder of River March, a public movement to restore and rejuvenate Mumbai’s environment. “But when people visit from out from outside, it’s the first thing that hits them,” he said.

In fact, it didn’t even cross Narendra Thakkar’s mind when he bought an apartment in the 13th floor of a high-rise building in Borivli which stands on the edge of the Dahisar river, which also originates from the SNGP and makes its way to the Arabian sea through the Bhayander creek.

When Thakkar, a 42-year-old director of a multinational firm booked the apartment in 2009, the Shree Krishna Complex was still under construction. The builder boasted of the river view on the brochure. “When we first saw the property, the water body looked nothing like a river. It was more like a large gutter,” Thakkar said. At the time, the builder assured him that the Brihanmumbai Municipal Corporation (BMC) was going to take up a cleanliness drive, and in the next few years, the river would be pristine.

In December 2021, state environment minister Aaditya Thackeray inaugurated the 246 crore Dahisar River Rejuvenation project that had been in the works since the 2005 deluge in Mumbai. The project included the construction of two wastewater treatment facilities and sewer lines that connected the nearby settlements to them, desludging the river bed and creating green spaces along the river, among others. Till now, the work orders for the sewage treatment facilities have been issued. No other work has commenced.

“It seemed like a promising option that time. Today, we live here as there is no other choice,” said Thakkar who moved into the tower in 2011 with his wife Niyati and son Vedesh. “We are constantly spraying air freshener as the foul smell gets unbearable on some days. In addition to the sewage water and plastic waste, a buffalo stable nearby also releases all its waste into the river, intensifying the odour,” he said.

The Thakkars live with the smell all day long no matter which part of the house they’re in. “It’s irritating and unsettling,” he said.

Dr Rakesh Kumar, a former director of the National Environmental Engineering Research Institute (NEERI) explained that the bad odour we smell are actually from the gases that emanate from polluted water bodies. “Hydrogen sulfide gas smells like rotten eggs. What we smell near polluted water bodies is a mixture of all these gases, with hydrogen sulfide being the main contributor,” said Kumar adding that in small concentrations, these gases may not be harmful, but long-term exposure is bound to have an impact on human health.

“Such strong odours can trigger headaches or nausea. It may not be uncommon to see such an impact when people are in close proximity of the polluted water body,” said Kumar.

There are no studies documenting such impact but beach and river clean-up volunteers often complain of these side effects after spending hours at the water bodies during their drives.

In 2016, a report by a private organisation called Environment Policy and Research India (EPRI) revealed that the pollution in the Poisar river was 100 times higher than what was considered safe. According to the Central Pollution Control Board, a biochemical oxygen demand (BOD) —the quantity of oxygen required by the flora and fauna to survive in the water — of more than 3 mg per litre makes the water unfit for human consumption and a BOD above 6 mg per litre makes it unsuitable for aquatic life. The EPRI team collected water samples from 10 locations and found that the BOD was 414.73 mg per litre in some locations. A river’s chemical oxygen demand (COD) refers to the amount of dissolved oxygen in water needed to oxidize chemical organic materials, and it is used to gauge the extent of effluents in a water body. A higher COD indicates more pollutants. Typically, the COD of sewage water is 100 mg per litre. In Poisar river, it was 767.1mg per litre.

…AND AN EYESORE

In 2014, when lawyer-turned-environment activist Afroz Shah moved to his Versova flat, the view outside his window distressed him. Every morning, he saw tonnes of plastic and other solid waste floating around Versova beach. “One couldn’t go for a walk or a swim. It was a disturbing sight,” said Shah, who spearheaded cleanup drives on the Versova beach starting 2015. Today, the beach looks clean and scenic, and the cleanup efforts are sustained to maintain it.

“When I open the window now, I smile. Smiling releases dopamine and promotes better mental health. So, the cleaner coast has definitely improved my well-being,” said Shah who believes that the best sort of living is achieved when done in tandem with nature.

Aquatic environments such as rivers, lakes and coasts, often called blue spaces, are associated with better mental health and well-being. A 2021 World Health Organization paper from Europe defines blue spaces as “outdoor environments — either natural or manmade — that prominently feature water and are accessible to humans either proximally (being in, on or near water) or distally/virtually (being able to see, hear or otherwise sense water).” In his book Blue Mind, California based marine biologist Wallace J. Nichols writes, “Beyond our evolutionary linkage to water, humans have deep emotional ties to being in its presence”. Nichols’s book combines neuroscience with human stories to establish how proximity to water can improve performance, increase calm, diminish anxiety, and increase professional success. It stands to reason then that ill-maintained water bodies, such as those found in the city, could induce irritability and anxiety.

There is limited but growing evidence of the links between blue spaces and better health and well-being. A 2019 study conducted by researchers at the University of Exeter in the United Kingdom showed that people who lived closer to the coast were less likely to have symptoms of a mental health disorder. “The positive health impact is real,” said Shah.

FINDING SOLUTIONS

In 2017, Vira and other members of River March created a floating island with wetland plant species on the Poisar River. The 25-square-foot floating island was made of plants uprooted from a Metro rail construction site in Andheri and put in 500 discarded plastic bottles which were then tied together to create a makeshift ‘mop’. This was placed in the Poisar river for around three weeks as an experiment to see if it could be used to clean the polluted waterbody.

Their idea was to demonstrate the concept of biological treatment to the civic body with the help of floating treatment wetlands (FTW) that are known to improve the aquatic habitat, trap odour and purify the water. “We hope that civic body implements such concepts too,” Vira said.

Mumbai’s civic body has initiated multi-crore projects to revive the rivers and stop solid waste from entering the sea. The BMC is looking at other long-term solutions. Mumbai’s civic body has initiated multi-crore projects to revive the rivers and stop solid waste from entering the sea. It plans to build 19 sewage treatment plants (STP) for the four river rejuvenation projects, which includes two for the Dahisar river with capacities of 0.5 Mega Litres (a million) per Day (MLD) and 1 MLD. The Poisar river will receive 10 STPs with an overall capacity of 33.5 MLD. The Oshiwara river is set to have five with a total capacity of 20.5 MLD, while the Mithi river, which has been under rejuvenation for the longest among all four (since the 2005 floods), is set to get a 6.7 km long tunnel through which sewage will be transported to a proposed STP at Dharavi that can treat up to 418 MLD.

“Work orders to establish multiple sewage treatment plants for Dahisar, Poisar and Oshiwara rivers have already been issued,” said P Velrasu, additional municipal commissioner (projects).

“The aim is to intercept the sewage, divert it to the treatment plant and then release the treated water into the river. These plants will come up in phase over the next three years,” Velrasu said adding that a sewage treatment plant for Mithi river is in its final stages, and the work on sewage interception along the course of Mithi river will also begin.

According to Velrasu, the civic body is trying trash brooms and catchment nets in rivers and marine outfalls to stop the plastic and other solid waste from entering the sea. “We are also working on bioremediation of nullahs. The difference will be visible in the coming years,” he said.

Kandivli resident Vira believes that the civic body should also use bioremediation to tackle the contamination in the rivers. “They can start with smaller patches. As the contamination reduces, perhaps, the smell will reduce too,” he said.

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