Rivers of Mumbai or sewers that stink?

Consequences of poor sewage management in the city and how it is affecting the water bodies

With the situation having turned alarming, the BMC has to hurry up. However, the civic body has estimated the upgradation of the six STPs will not be completed anytime before 2026 to 2027.

Meanwhile, effluent discharge and poor sewage management has an adverse 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 the growth of mangroves, which is a negative indicator in such places. Along with mangroves, there should also be an increase in the number of birds and fish, but this is not happening. Mangroves are growing because the 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 accompanied by an increase in flamingos visiting the area. However, the rise in the number of flamingos is actually an indication that all is not well. There are bacteria and different types of insects present in the water which flamingos feed on them. Thane creek’s holding capacity has more sludge and silt and not enough water. Fishermen are not able to catch fish and crabs, unlike in the past.

Meanwhile, on the western coast, Versova and Malad creek are getting raw sewage. The sand on the beaches in this 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. The pollution not only makes Mumbai’s beaches unsafe for swimming, but contaminates the seas enough to make it unfit for fishing as well,” said a marine biologist from Central Marine Fisheries Research Institute (CMFRI).

Over 700 megalitres of untreated sewage discharged daily into 4 Mumbai rivers

According to a civil appeal petition filed by the BMC in the Supreme Court, a total of 747 megalitres (a single megalitre comprises 10 lakh litres) of untreated sewage is released into four rivers in Mumbai every day. Starting from the Mithi River, which receives the highest quantum of dry weather flow (DWF) at 285 ML per day, followed by the Poisar river (67 MLD), Dahisar river (56 MLD) and the Oshiwara – Walbut river (17 MLD).

“After the completion of the ongoing river rejuvenation projects, a major chunk of DWF, around 426 MLD, will be diverted into the existing municipal sewer lines/STPs,” said P Velarasu, Additional Municipal Commissioner (Projects) of the BMC. The BMC does not seem to have a clear plan of action for the remaining 321 MLD of DWF, environmentalists have alleged.

“Experts, and even IIT Bombay’s report suggests there should ideally be 30-35 STPs for Mumbai, either ward wise or according to the requirement of the rivers. We have even suggested small STPs near the four rivers. However BMC officials have not shown any interest in these suggestions,” said D Stalin, green activist and Director of NGO Vanshakti

A comprehensive report submitted by team River March (an NGO that has been campaigning for the rejuvenation of Mumbai’s four rivers) to the Municipal Commissioner in 2019 stated that discharge of raw sewage, animal waste and garbage are the main causes of pollution in three of the city’s rivers — Dahisar, Poisar and Oshiwara.

“Many slums discharge raw sewage into the river. We have recommended that sewage lines should be laid in slums to stop discharge of raw sewage. We are not saying or suggesting anything new. The Chitale commission talks about STP plants, restoration of rivers, none of which has been implemented since 2006. Diversion of sewage from natural water bodies is the primary way to restore them. Neither has BMC upgraded and commissioned STPs, nor have they managed to restore the river so far but have concretised them in turn. It seems BMC is just not interested in restoring these rivers,” said Gopal Jhaveri, environmentalist and co-founder of River March.

“Unless we have proper functioning STPs, sewer lines in place and the civic body stops discharging waste water in creeks, river rejuvenation will never be a success and public money will keep going down the drain,” said Stalin.

From rivers to sewers – journey of Mumbai’s four rivers

Mithi