Drain water entering Navi Mumbai’s DPS Flamingo Lake raises sewage treatment quality concerns

Navi Mumbai: A laboratory analysis of water drawn from the drain adjoining the DPS Flamingo Lake in Nerul raised environmental concerns in Navi Mumbai, with activists alleging that inadequately treated municipal discharge flowed into the ecologically sensitive wetland during low tide. The activists also said they experienced a "terrible stink" at the lake. The sample, tested by SSAS Laboratory, recorded pH at 9.12 against the acceptable 6.5 to 8.5 range, indicating highly alkaline water that can disturb aquatic life and wetland ecology.The report showed total dissolved solids (TDS) at 7,950 mg/L against the prescribed maximum of 2,100 mg/L, biochemical oxygen demand (BOD) at 36.4 mg/L above the permissible 30 mg/L limit, and chemical oxygen demand (COD) at 114.8 mg/L. The laboratory concluded that the sample did not conform to inland water quality norms.Environmental group NatConnect Foundation, which commissioned the test, said the findings raised questions over the quality of sewage treatment before discharge into the open drain that flowed towards the wetland and onward to Thane Creek. The high pH level indicated strongly alkaline water that can disturb aquatic life, affect microorganisms and worsen stress in fragile wetland ecosystems. It added that elevated TDS pointed to excessive salts and dissolved pollutants, while high BOD suggested organic contamination that can reduce oxygen available for fish and other aquatic species"This is not a routine storm-water channel. It carries water that reaches the flamingo wetland during low tide. If such quality is entering the system, serious questions arise on treatment standards and monitoring," said B N Kumar, director of NatConnect. Navi Mumbai Municipal Corporation officials said they have not received such complaints and, if this is the case, they will examine the matter.The findings came amid continuing concern over the health of the DPS Flamingo Lake, part of the wider wetland chain linked to the Thane Creek Flamingo Sanctuary. Earlier water quality examinations of the DPS lake itself indicated heavy organic loading, algal growth and signs consistent with sewage intrusion. Independent assessments recorded elevated BOD, alkaline stress and high dissolved solids, while field observations noted froth, oily traces and thick algae mats on the water surface. Experts quoted by activists earlier warned that such indicators often suggested inflow of urban wastewater or mixed sewage discharge, making the habitat unsuitable for aquatic organisms that sustain flamingos and other migratory birds.NatConnect said the new drain sample strengthened the need for an independent audit of the civic sewage treatment plant and its filtration standards, especially as the same outflow was believed to move towards the creek ecosystem. "The issue is larger than one lake. If partially treated water is flowing through drains into wetlands and the creek, the ecological cost could be significant," Kumar said. Rekha Sankhala of Save Mangroves & Flamingos Forum called for real-time monitoring of sewage treatment plant output, tidal-flow studies, plugging of illegal sewage entry points and restoration of the DPS wetland before the next migratory bird season.