Activated sludge respiration inhibition test

Principle

The respiration inhibition test for activated sludge is investigating potential effects of test substances or waste water on mixed bacterial populations, in particular in aerobic wastewater treatment plants.

Abstract

Activated sludge is exposed to a serial dilution of the test substance or waste water for 30 min and/or 3 hours. A control without test substance is studied in parallel. The inhibitory effect of the test substance on the respiration rate in the test vessels is expressed as percentage of the mean respiration rate of the controls. As test result, the 50% effect concentration related to the oxygen consumption (EC₅₀) is determined. A parallel test with N-allylthiourea can be performed to determine the inhibition of heterotrophic respiration and nitrification.

Endpoints

Total respiration, heterotrophic respiration, nitrification