Citizens have continued to favour idols made of plaster of Paris

The city celebrated Gowri and Ganesh festivals with fervour recently. Thousands of idols were immersed in the city’s various lakes and tanks.

It is now time to clean up. Several immersion tanks in the city are being drained and cleaning work has commenced.

Analysing samples

The cleaning process has revealed that citizens have continued to favour idols made from plaster of Paris. This has obviously had a toll on the water bodies, as the Karnataka State Pollution Control Board (KSPCB) has found after analysing the lake water and sediment samples.

Based on the primary water quality criteria, the lakes in the city have dropped to class D (worst condition) from class C (bad condition), as per the Central Pollution Control Board classification.

This is mainly due to the reduction of dissolved oxygen level and increase in the biochemical oxygen demand.

Heavy metals

The KSPCB has found traces of heavy metals in these samples collected from Lalbagh lake, Yelemallappa tank, Ulsoor lake and Yediyur lake.

Traces of mercury have been found to have increased from 0.003 mg/ litre to 0.007 mg/ l at Lalbagh lake.

Similarly, traces of nickel have increased from 0.16 mg/ l to 0.42 mg/ l at Yediyur lake. Chromium and cadmium traces have also been detected at Yediyur lake.

Traces of both these metals have also increased, KSPCB has found.

Traces of heavy metals — mercury, chromium, cadmium, lead, nickel, copper and iron — have been found even in the lake sediment samples collected from Lalbagh lake, Yelemallappa tank and Ulsoor lake.

However, KSPCB claimed that all measured metals, except iron, were within the limits.

Dissolved oxygen

A KSPCB release stated that the dissolved oxygen level has decreased due to this. Dissolved oxygen level of four mg/ l is essential for the existence of aquatic life. Anything lesser will affect aquatic life in these water bodies.

Drastic reduction has been detected at Ulsoor lake, where the dissolved oxygen level has dropped to 0.6 mg/ l from 12.7 mg/ l. It has dropped to 3.5 mg/ l from 5.8 mg/ l at Lalbagh lake, while it is two mg/ l from 6.6 mg/l at Yediyur lake.

A marginal reduction has been detected at Yelemallappa tank, where the dissolved oxygen levels have dropped to 2.6 mg/ l from 2.7 mg/ l. The release also notes that the biochemical oxygen demand has increased from 4 mg/ l to 8 mg/l.

Advice

The possible solution to prevent the degradation of the water bodies is to ensure that citizens avoid the use of non biodegradable material such as polystyrene (Thermocol) altogether, while composting all biodegradable material, the release added.

More In: Bangalore