Physico-chemical and bacteriological screening of Hussain Sagar lake: An urban wetland

Hussain Sagar is a man-made lake originally designed for drinking water purpose that receives domestic sewage and industrial effluents through drainage canals due to rapid residential and industrial growth. Also, every year thousands of idols are immersed into the lake during festivals. In this context, a comprehensive study was initiated for monitoring the lake water quality. Various physico-chemical parameters such as temperature, pH, EC, TDS, COD and chlorophyll a were analyzed using APHA standard methods Water was also monitored for heterotrophic bacteria, total coliforms, Escherichia coli and antibiotic resistant bacteria. The average values for heterotrophs were found to be 8.6 × 104 and 2.8 × 104 CFU/mL before and after idol immersion, respectively. While the average values for total coliforms and E. coli were 5 × 104 and 5 × 102; 1.2 × 104 and 7.2 × 101 CFU/mL, for the respective sampling periods. The mean values for ampicillin and gentamicin resistant bacteria were 5.9 × 103 and 6.9 × 102; and 2.2 × 103 and 5.4 × 102 CFU/mL, respectively. It was found that TDS, COD and chlorophyll a values were decreased after idol immersion due to extensive cleaning. The statistical results showed no correlation between faecal bacteria and physico-chemical parameters and one way-ANOVA indicated statistically significant differences between the mean values of different sampling locations, with respect to COD and E. coli at 95% confidence. However, enormous load of coliforms and E. coli indicated severe contamination of the lake with domestic sewage and human excreta. Thus, the water is not suitable for human consumption/drinking purpose. Notably, incidence of antibiotic resistant bacteria in lake water is a potential threat to both public health and the environment. Thus, regular monitoring and applying appropriate corrective actions are needed to improve the water quality.