Quantitative estimation in cod units of refractory organic compounds produced by activated sludge microorganisms

Abstract

Data on the amounts of refractory organic compounds produced by activated sludge microorganisms under various conditions of cultivation were collected and treated in order to find the main factors influencing their production. The following systems were compared: batch non-proliferating and proliferating, continuous with high and low mean cell residence time and semicontinuous with separate aerobic sludge stabilization. It has been found that there exists a linear relationship between the refractory microbial products and the initial substrate concentration, both expressed in COD units. Both the slope and intercept of the relationship depend on the mean cell residence time or the observed specific growth rate. Depending on the cultivation conditions, the refractory products can amount to 1–10% of the substrate consumed. It has also been found that the amount of refractory compounds, expressed in COD units, released from 1 g of aerobically decomposed biomass varies from 15 to 25 mg g −1.