High levels of faecal contamination reported in Vembanad Lake

The Vembanad lake has been highly contaminated with faecal waste as a recent international study has recorded E.coli contamination of alarming levels in the waterbody.

The Vembanad lake has been highly contaminated with faecal waste as a recent international study has recorded E.coli contamination of alarming levels in the waterbody.

The first four months of the 2018 monsoon saw an E.coli count at 16,631 cells in one millilitre of lake water. The World Health Organisation (WHO) guidelines for coastal and freshwater had noted there was a 10% chance of gastrointestinal illness from exposure to water exceeding E. coli abundance of 5 colonies per millilitre.

The study was jointly carried out by the National Institute of Oceanography (NIO), Kochi Regional Centre, Plymouth Marine Laboratory, UK, Nansen Environmental Research Centre India, and the Central Marine Fisheries Research Institute, Kochi. The water quality of the Vembanad lake was monitored for a year prior to the lockdown and immediately after the lockdown, so that the impacts of the 2018 floods and the pandemic-induced lockdown in 2020 on distribution of faecal contaminants in the lake could be assessed.

E. coli counts in the lake are consistently higher than the WHO threshold, irrespective of the season. However, during the lockdown period, there was 99.8% decrease in the average abundance of E. coli, said A. Abdulaziz of NIO, who was the lead author of the scientific paper ‘The distribution of faecal contamination in an urbanised tropical lake and incidence of acute diarrhoeal disease.’

Shubha Sathyendranath, V. Syam Kumar, Nandini Menon, and Grinson George were among the researchers who carried out the year-long analysis

More than 50% of E.coli isolates from the lake showed varying resistance against 12 antibiotics including Erythromycin, Moxifloxacin, Gatifloxacin, Trimethoprim, and Gentamicin, which spoke about the anthropogenic role on the prevalence of faecal contaminants, according to researchers.

Direct discharge of septage from commercial and residential buildings and tourist boats and unlawful dumping of toilet waste and solid waste might have contaminated the waterbody. Monsoon showers carried the maximum load of septage to the lake system. Analysis revealed that faecal contamination was prevalent throughout the year, which increased during the southwest monsoon, noted the paper.