Development and application of a resazurin-based biomass activity test for activated sludge plant management

A rapid, robust and cost-effective method of assaying the metabolic activity of the biomass of activated sludge plants would be a valuable process control tool in the wastewater treatment industry. We have developed and optimised a simple colorimetric test protocol, based on the redox dye resazurin, in which levels of reduction of the dye are proportional to cell biomass and respiration rate in both freshly sampled municipal sludges and in a surrogate activated sludge culture, Polytox. The method has been used to assess the impact of trade wastes on the activities of two municipal activated sludge populations of differing characteristics.