The water quality index on the banks of Kolkata shifted from bad in pre-monsoon to very bad during monsoon.Credit: Subhra Priyadarshini
Researchers from the Indian Institute of Science Education and Research Kolkata have found that human activities in semi-urban and urban locations on the banks of the Ganges have contributed to poor water quality downstream by discharging untreated sewage, and solid and liquid waste1.
They detected high concentrations of nitrate, which can fuel an explosive growth of algae, at various locations on the banks of the river in West Bengal.
Algal growth is known to release molecules that adversely affect the growth of native fish and hamper the fishing-dependent economy, the researchers say.
The research team, led by Punyasloke Bhadury, studied seasonal trends along a 50-kilometre stretch of the river. The researchers collected water samples at different locations before, during and after the monsoon season.
They then assessed water quality of the river and generated an index based on dissolved oxygen, pH levels, electrical conductivity and dissolved nitrate. The researchers found that the water quality index on the banks of Kolkata went from poor before the monsoon to very poor during the monsoon, with marginal changes post-monsoon. Water quality deteriorated during the monsoon at most sites, including Dakshineswar, Chandannagar, Halisahar, Tribeni and Kalyani.
Discharge of pollutant-laden water into the river influenced the environmental parameters and concentration of macronutrients, worsening the water quality, the researchers report.
“We have identified specific species of microalgae which could potentially be used to remove harmful pollutants from the river,” Bhadury says.
