Selenium Removal From Waste Waters -an Update

In the author's selenium report of 1994 (1), the literature was culled for selenium removal technologies that had a chance of producing effluents with <10 ppb of total selenium. Very few processes could achieve such low concentrations. The EPA dictates such low concentrations. Discharges to fishery waters must be <5 ppb total selenium. The federal max­imum contaminant level ( MCL) for drinking water is 50 ppb. The EPA regulations are for total selenium, not for the species, perhaps because an approved EPA assay method is atomic absorption and it cannot distinguish between species.