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Good practice Imported

East Kolkata Wetlands — Sewage-Fed Aquaculture as Natural Wastewater Treatment

India · Kolkata · See the India profile · See the Kolkata profile

Evidence: Observational / pre–post Top 58% 40/100 · Ask Evidence Copilot about this practice

A ~12,500-hectare Ramsar wetland east of Kolkata has informally treated the city's sewage since the 1930s through ~254 fish ponds, producing roughly 10,000 tonnes of fish a year, though encroachment and industrial pollution now threaten it.

550–1,000 million litres/day
Wastewater processed daily
10,000–11,000 tonnes/day
Fish produced daily
~33 %
Share of Kolkata's fish consumption supplied
East Kolkata Wetlands — Sewage-Fed Aquaculture as Natural Wastewater Treatment

Details

Maturity
Established
Promoter
East Kolkata Wetlands Management Authority (EKWMA)
Period
1930s–present
Keywords
wastewater treatment, aquaculture, wetlands, urban water management

Context

For nearly a century, sewage from Kolkata has been treated through roughly 254 shallow fish ponds (bheris) covering part of a ~12,500-hectare wetland complex, designated a Ramsar site in 2002.

Results

EKWMA and a peer-reviewed study estimate the system processes 550–1,000 million litres of wastewater daily, producing roughly 10,000–11,000 tonnes of fish and 150 tonnes of vegetables daily — supplying close to a third of Kolkata's fish consumption — but the same peer-reviewed study found locally elevated arsenic, mercury and cadmium in fish and sediment, and reporting documents ongoing loss of fishpond area to encroachment despite statutory protection.

Implementation
Indicative cost
Low (< €50k)
Time to results
Long (> 3 years)
Staffing & skills
East Kolkata Wetlands Management Authority (EKWMA), Local fisher/farmer communities

Conditions for success

  • Statutory protection under the 2006 West Bengal East Kolkata Wetlands Act

Common failure modes

  • Heavy-metal contamination from nearby tanneries/industrial effluent; ongoing fishpond conversion to rice paddy and illegal encroachment

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Data sources

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