Kerala - Thiruvananthapuram   

Four lakes under bacterial attack

Thiruvananthapuram: Bacterial contamination poses a serious threat to the water quality in four major lakes in the State, a study conducted by the Centre for Water Resources Development and Management (CWRDM), Kozhikode, has found.

Presenting the findings of the study at the Kerala Environment Congress 2009 held here last month, scientist P.S. Harikumar said the Pookot lake in Wayanad, Vembanad lake in Alappuzha, Sasthamkotta lake in Kollam and Vellayani lake in Thiruvananthapuram were polluted with bacteria from various sources.

The Pookot lake, a freshwater reservoir, showed the presence of coliform bacteria in 36 per cent of samples taken for the study, while e-coli were present in 65 per cent of the samples.

Mr. Harikumar’s paper noted that the Vembanad lake and the backwater system were heavily polluted with industrial effluents and urban waste, causing eutrophication (increase in the quantity of chemical nutrients) of the waters. The lake is infested with phytoplankton and polluted with agricultural and municipal effluents, the study observes.

The Sasthamkotta and Vellayani lakes, both important sources of drinking water, are threatened by urbanisation, reclamation and silting, besides bacteriological contamination, it notes.

The study found that the lower reaches of the rivers in Kerala faced considerable water quality problems, mainly due to faecal contamination. Pilgrimage stations near the rivers indicated organic pollution. Salinity intrusion into the lower reaches of the rivers during summer was found to have an impact on drinking water supply.

Mr. Harikumar identified reclamation as a major problem faced by the backwaters. Indiscriminate discharge of municipal waste, agrochemicals, oil from ships and fishing vessels were other threats as was discharge of industrial effluents. The release of polyphenols and hydrogen sulphide during coir retting was another source of contamination.

The study also revealed that more than 90 per cent of the open wells in the State were contaminated with bacteria. Untreated sewage and soil waste were contributing to the pollution of groundwater resources. It observed that sites for municipal and industrial landfills were selected with little regard for the impact of leachate on groundwater quality.

Analysis of groundwater samples collected from near burial grounds indicated that nitrate, calcium, total hardness and coliforms were present in excess concentration. Eight per cent of the samples from municipal landfill sites showed high coliform contamination. More than 60 per cent of the groundwater samples collected from the Kochi industrial area showed excess concentration of heavy metals, nitrate or fluoride.

The paper recommended a continuous water quality monitoring programme and water safety plan for the preservation and improvement of water quality in the State.

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