Cleaning Cooum: Micro algae can help decrease heavy metals in river

Chennai: What 735 crore spent on reviving the dying Cooum since 2015 could not do, a set of micro-organisms seems to have the potential to achieve.City researchers have hit upon microalgal species Chlorella vulgaris, Scenedesmus dimorphus, and Phormidium sp to decrease heavy metal concentrations, resulting from illegal sewage discharge, in the Cooum.This is a coup of sorts, more so because in 2023 a Central Pollution Control Board (CPCB) report still declared the river the most polluted in India.The three microalgal species have metal-binding proteins in their cell walls, and absorb heavy metals in water, reducing the concentrations. "Heavy metals are like food for algae, but harmful for humans. Algae absorb and metabolise metals till they die in 15 days," said Prabhakaran Mylsamy, a botany professor at Pachaiyappa's College and one of the researchers of the study.As one batch of algae dies, new batches are introduced until the heavy metals and pH levels are brought within the safe limits set by World Health Organisation. "After algal treatment, our samples had 7 pH-7.5 pH," said Prabhakaran.Researchers used micro-organisms to clean samples picked up from 27 locations, from upstream reaches in Tiruvallur district to Napier Bridge near the estuary. "We procured these microalgae from freshwater bodies like Porur Lake and temple tanks, including the one in Triplicane Parthasarathy Temple," he said. It could be scaled up to clean large parts of the river with calculations, according to the study titled ‘Heavy Metal Pollution of River Water and Eco-friendly Remediation Using Potent Microalgal Species' published in the Water Science and Engineering journal in March.Procuring algae is not expensive. To treat sewage, a shallow pond (30 cm deep) is created and the wastewater goes there. Then, the algal species are introduced to treat the water, including foul odour and dark colour. For every 1L of sewage, 10mL of algal solution is used.But sewage treatment plants generally have multiple filters, which cost lakhs, and the sludge becomes a secondary pollutant. However, the sludge from the algal treatment can be used as manure, said the researchers.The study recommended that such shallow ponds be created within Cooum for algal treatment, thereby reducing the heavy metals entering the river.
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