Neeri confirms high pollution in Ambazari lake due to sewage, industrial waste

Nagpur: CSIR-National Environmental Engineering Research Institute (Neeri) has confirmed Ambazari lake water is highly polluted due to release of sewage and industrial waste. At the same time, Neeri has okayed the water’s utilization for drinking purpose after conventional treatment, and evaluation of water quality at each treatment unit.
On April 13, TOI had reported fishes were dying in Ambazari lake in large numbers. Nagpur bench of Bombay high court had suo motu treated TOI’s report as a public interest litigation (PIL) and issued notices to many, including NMC.
Following the TOI report, Nagpur Municipal Corporation (NMC) asked Neeri to inspect the lake, collect water samples, and evaluate the water quality. Also, Maharashtra Jeevan Pradhikaran (MJP) contacted Neeri for the same as it planned to supply water from the lake for drinking purposes to colony of Ordnance Factory Ambajhari (OFAj), households in Wadi Municipal Council, and Dawlamethi Gram Panchayat.
Neeri sent its evaluation of water quality to NMC and MJP on Wednesday.
“Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) were observed to be above drinking water quality standards, which is mainly due to incoming water streams carrying sewage and waste water into the lake. Presence of indicator bacteria i.e. faecal coliforms indicates that the water is contaminated due to sewage. Gloeotrichia, synechocystis, synechococcus and anabaena genera, which belong to class cyanophycea, indicate toxin releasing species in water body,” Neeri’s report said.
Neeri also observed bacterial contamination, high and rich density phytoplankton concentration in the water. “Water quality is impaired after its confluence with Nag river. The spatial changes in lake water quality are attributed to characteristics of catchment area, mixing of runoff water, mixing with town flows and human, animal activities in the lake,” the report said.
The Nag river carries only untreated sewage water released from households situated in Wadi, Dattewadi and adjoining areas. Also, industrial waste from some industries of MIDC Hingna is also allegedly released in the river.
Neeri added the lake water is highly polluted by organic/inorganic pollutants. “BOD and COD were from 9.2 mg/L to 14.4 mg/l and 29 to 47 mg/L, respectively. Low value of DO were observed in the range of 1.6 to 4.9 mg/L in five of total eight locations where dead fishes were observed floating. DO was found to be normal at remaining three locations and no fish kill was observed. Shannon Wiener Diversity (SWI) index lies in the range of 2.1 indicating the water probably has high organic pollution,” the report stated.
Though mercury was not detected, Neeri traced various other heavy metals — aluminium, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead and zinc — in the water.
Neeri also mentioned physico-chemical parameters were found within acceptable limits, excluding turbidity, which was high.
Neeri said most of the dead fishes were of one specie — tilapia. “These species are in the habit of rising to surface for respiration. In summer months, due to rise in temperature, the lake shrinks due to evaporation losses and reduces in volume. DO reduces, and the toxic bacteria profusely multiply, which enter the blood stream of the fish via respiratory system, ultimately leading to incidence of fish kill. It is also evident from post mortem report of Veterinary College that the suspected cause of fish kill might be due to septicaemia/toxicity. Septicaemia is systematic infection of the blood by pathogenic microorganisms, especially bacteria that originate from a localized source. It is commonly known as blood poisoning,” the report said.
NMC is likely to initiate measures suggested by Neeri to conserve the lake and reduce high level of pollution.