HYDERABAD: Researchers from IIT-Hyderabad, as part of a study on pollution at Hussainsagar, collected water and sediment samples from five different points of the lake. Two of them were sites where idols were extensively immersed during religious festivities.
One was close to the Kukatpally nala, and the remaining two were sites of regular religious practices. The concentration of heavy metals in the lake’s sediments were detected above the normal values in three of the five sites -- two sites where idols are extensively immersed, and the one close to the Kukatpally nala.
Analysis of concentrations of various heavy metals revealed that the highest risk stands from significant contamination with cadmium, lead, zinc, and copper, apart from arsenic, nickel and chromium.
Heavy metals were detected in quantities much above the ideal values, even at a depth of 40 centimeters beneath the lake bed.
Industrial effluents carried by Kukatpally nala and discharged by industrial units manufacturing batteries, ferrous and non-ferrous metals, rubber, alloy, chemical products, in its upstream areas, are responsible for introducing a majority of heavy metals into the lake. Immersion of idols during religious events contributes to sustaining these metals in the water.
The researchers pointed out that immersion of idols in the lake increases suspended particles in the water. These particles then trap the heavy metals from the industrial effluents and settle down, adding to the heavy metal loads of the lake bed.
Also, the plaster of paris from idols also binds well with the heavy metals, forming a concentrated layer on top of the bed.
In addition to the chromium coming from industrial effluents discharged from the tanning and dying industries, high levels of the heavy metal are also found in the paints used on idols that are immersed during these festivals.
Apart from the bed, the lake water is also highly contaminated. However, heavy metals were found to be above the permissible limits only at the site located near the Kukatpally nala, as per criteria continuous concentration by the US EPA.