India, June 9 -- New environmental standards require caustic soda plants using membrane cell technology to pass a fish-survival test for wastewater toxicity.

The rules say at least 90% of fish must survive after 96 hours in 100% wastewater during laboratory-based bioassay testing.

The test is meant to assess whether treated industrial effluent is toxic to living organisms, not just whether it meets individual chemical limits.

The standards also set limits for pH, chloride, suspended solids, dissolved solids, water use and wastewater generation.

Experts say enforcement will be key, as bioassay testing requires specialised laboratories, trained staff and regular independent monitoring.

Wastewater from caustic soda plants using membrane...