Hyderabad: Dissolved oxygen values in the Hussainsagar lake were high before the immersion of Ganesha idols last month, but gradually decreased during immersion. They increased after one week of immersion, according to the Telangana Pollution Control Board which monitors the pollution levels in the lake.
The higher dissolved oxygen levels one week after the immersion was attributed to other polluting inflows into the lake.
Dissolved oxygen (DO) levels and biochemical oxygen levels depict the possibility of aquatic life in the water. The levels of DO were 6.4mg/litre before immersion which fell to 3.3 mg/litre after immersion. The permissible limit is of 3 mg/litre.
The biochemical oxygen (BO) demand was 38 mg/litre before immersion and afterwards it was 20 mg/litre after peaking to 43 mg/litre on September 11, the day before Ganesha nimajjanam. These are way beyond the permissible limits of 3 mg/litre.
A TSPCB official said that high levels of DO and BO before immersion of idols showed that the quality of water in the lake was bad. These high levels do not allow for survival of aquatic life, which is a marker for good water quality. The levels improved after immersion due to the heavy rainfall which brought in more inflows into the lake.
The total coliform levels were found to be on the higher side during the immersion period at NTR and Lumbini Park and Lepakshi Handicrafts. The faecal coliform values increased during and after immersion at all the six locations monitored by the pollution board.
The six locations monitored are NTR Park at Platform No. 1, NTR Park at Platform No.2 , Lumbini Park, Necklace Road, Lepakshi Handi-crafts and Buddha statue.
The worst deterioration of water quality was in 2018, the officer stated. A total of 50,000 idols were immersed in the Hussainsagar in 2019.
