Control of activated sludge filamentous bulking: experimental verification of a kinetic selection theory

Abstract Two laboratory activated sludge systems, completely-mixed and selector-type, were continuously fed with a multi-component substrate. With excess biomass from both systems, the maximum substrate removal rates, r x.m , and the half-velocity coefficients, K s , were determined by means of a simple respirometric method. The following substrates were tested: glucose, galactose, acetic acid, valeric acid, citric acid, glutamic acid, alanine, tyrosine, methylalcohol, ethylalcohol and phenol. It has been found that both the r x.m and the K s are basically lower with the mixed cultures cultivated in a completely-mixed reactor (filamentous) than with those cultivated in a selector-type reactor (non-filamentous). The results have experimentally verified a kinetic selection theory in mixed cultures published previously.