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Mumbai set to have network of 7 key sewage treatment plants. Why it took almost 20 yrs

PM Modi will Thursday perform bhoomi poojans for the 7 plants to be set up by BMC at an estimated cost of Rs 26,000 cr. The project is expected to be completed in 4-6 years.

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Mumbai: After a delay of almost 20 years and cancellation of several tenders, Brihanmumbai Municipal Corporation’s (BMC) ambitious Rs 26,000 crore sewage treatment plants (STPs) project finally seems set to see the light of day, with Prime Minister Narendra Modi scheduled to perform bhoomi poojans for seven STPs Thursday.

The bhoomi poojans will be a part of several big-ticket projects the PM is supposed to inaugurate in Mumbai this week.

“The STPs are a long-pending problem faced by Mumbai. The delay in implementation happened for various reasons. However, because of strong governance by the state government and also the intervention of the Honourable Supreme Court, the much-needed projects are seeing the light of day,” said P. Velrasu, additional municipal commissioner, BMC.

The planned STPs will be set up at Worli, Bandra, Dharavi, Versova, Malad, Ghatkopar and Bhandup and each will have the capacity to treat 2,464 million litres of sewage per day. The project is expected to cost upwards of Rs 26,000 crore and is a part of what the BMC has termed ‘Mumbai Sewage Disposal Project — II’.

In 2021, it was Deputy Chief Minister Devendra Fadnavis, who had demanded that tenders for these seven STPs be scrapped owing to being “inflated”. The BJP leader had then been in opposition in the Maharashtra assembly.

Thursday’s bhoomi poojan comes ahead of this year’s expected BMC elections.

Mumbai, being an island city, has abundant water resources, but the water is often polluted by effluents and the BMC expects this project to reduce the level of toxicity in the city’s water bodies. The project is expected to be completed in four-to-six years, an official document shared by the BMC states.

An STP is a treatment facility that removes pollutants from the sewage to make it less hazardous and safe for discharge into water bodies.

At present, sewage is collected at seven zones in the city — Worli, Bandra, Colaba, Versova, Malad, Ghatkopar and Bhandup — and treated only at primary level before being released into water bodies like creeks, rivers and the Arabian sea. Primary treatment of sewage includes removal of those materials that either float or sink to the bottom.

But with the new STPs that will be constructed keeping in mind the stricter norms of Central Pollution Control Board, the sewage will be treated at secondary and tertiary levels, thereby reducing pollution.

The secondary level of treatment removes the soluble organic matter that escapes primary treatment and more of the suspended solids. This is then further treated and filtered and polished as a part of tertiary level treatment.

Speaking to ThePrint, environmentalist Debi Goenka, however, said that while treating water is fine, the water should have been recycled and reused the way it is in Singapore. “This technique of treating sewage water is old and, going forward, the BMC should have instead treated the water to be recycled and reused.”

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STP and its significance

The idea of the STPs was first mooted way back in 2002, but it did not materialise. The project was re-conceptualised in 2009, a BMC official said, but failed to kick off for several reasons.

The tendering process was stuck in litigation since 2017 when the Ministry of Environment and Forests (MoEF) issued a notification stipulating the norms for the construction of STPs but the National Green Tribunal (NGT) put a stay on the notification. BMC challenged this in the Supreme Court. In 2019, SC gave relief to the BMC and allowed the tendering process.

In later years, poor response from bidders and cost escalations added to the challenges. The reason for this was not made clear by the BMC.

According to estimates prepared in August 2020, the contract for the seven STPs were to cost a total of Rs 16,412 crore. The tenders were scrapped after contractors reportedly quoted 30-70 per cent above the BMC’s estimate.

After the Supreme Court’s directives to the civic body to award tenders before 31 May, 2022, the BMC finalised contractors for construction and maintenance of these STPs and the final project cost was pegged at around Rs 26,000 crore.

Meanwhile, the GST on design and construction cost increased from 12 per cent to 18 per cent in July 2022, which also contributed to the escalation in the project’s cost from Rs 21,000 crore in 2021 to Rs 26,000 crore in May — a major hike from the Rs 5,500 crore project cost estimated in 2009.

Before 2022, BMC had planned to upgrade the primary STPs at existing locations, with stricter norms from the Central Pollution Control Board, but BMC decided in 2008 to construct new STPs at these locations, with an addition of Dharavi.

Work on the Colaba STP, a BMC official said, was completed on a pilot basis in 2020. It is now functional.

In Oct 2017, the environment ministry tweaked standards for four parameters that determine water quality — pH value, which captures the level of acidity; biochemical oxygen demand (BOD); total suspended solids (TSS); and fecal coliform (FC).

FC bacteria is found in the intestines of warm-blooded animals and the new standard is less than 1,000 (most probable number per 100 millilitre) for STPs across the country.

According to the 2011 Census, Mumbai has a population of 1.2 crore and the official BMC data says the city generates around 2,400 million litres of sewage every day. The city has a network of 2,000 km odd sewage lines, says the BMC website, and, according to an official, the municipal body is in the process of adding more lines.

“The technological standards of the proposed STPs are world-class with 50 per cent of water being treated at tertiary level. The marine pollution will come down drastically and Mumbai as an international city will get what it deserves. We in BMC have worked for the past two years to make these technically complex projects successfully tendered and awarded,” said Velrasu.

(Edited by Poulomi Banerjee)

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