Water in some parts of the Pallikaranai marshland has turned pink, pointing to the possibility of a rise in pollution in localities neighbouring the Perungudi dumpyard.
The Greater Chennai Corporation (GCC), the Tamil Nadu Pollution Control Board (TNPCB), the Forest Department and Anna University have started monitoring the situation. Residents have complained to the civic body about the issue demanding initiatives to prevent further pollution.
A team of researchers led by S. Kanmani, director of the Centre for Environmental Studies, Anna University, conducted an investigation into the reasons for the unusual colouration of the surface water in the marshland and reported that preliminary analysis indicated the presence of methanotrophs, which include bacteria and other single cell microorganisms.
“Leachate with high biodegradable organics from the dumpsite released into the waterbody may be the reason for the multiplication of the methanotrophs — methane oxidising bacteria. The pink colour of the waterbody is a result of the rapid multiplication of the pigmented bacteria and algae. The reasons may include blooming of algal species belonging to the group of dinoflagellates, growth of halophilic archaea, distribution of methanotrophs or the presence of purple sulphur bacteria,” the report said.
Corporation Chief Engineer (Solid Waste Management) N. Mahesan said civic officials were monitoring the situation, and taking measures to prevent the spread of the colour.
The colour has been observed near Thoraipakkam Radial Road on the northern side of the stretch, gradually reducing in concentration closer to the dump. The southern side, which was handed over to the Forest Department by the civic body 10 years ago, remains unaffected.
Residents, who do not wish to be named, said officials should also monitor the vehicles dumping polluted material at night. They said they were worried about the ground water contamination and demanded the authorities concerned to intervene.
Convener of the Save Pallikaranai Marshland Forum S. Kumararaja said sewage from more than 60 wards was taken to the marshland. “Treated sewage has been let out in the marshland. We are not sure if the sewage has actually been treated before being released. This should stop,” he said.
According to officials, it was observed that the surface water near the location of package I biomining site in Perungudi dump yard has turned pink. Analysis of the surface water samples from six locations around the dump was done in the past few months. Biomining operations at package I started in March 2022.
Analysis of the different parameters indicated that the total dissolved solids of the surface water near package I was very high (8542 mg/l) when compared with other packages, which vary from 1050 mg/l to 1560 mg/l. The chloride, hardness and sulphates near package I is also relatively high.
The sample from the location near Package I was more alkaline (pH — 8.32) when compared with other locations ( pH — 6.85 to 7.8). Gradual increase of the total dissolved solids were observed from January to April, which could be due to high evaporation during the summer season, officials said.
More studies will be conducted to prevent the pollution of the marshland, officials added.