Measurement of microorganisms with PHA production capability in activated sludge and its implication in Activated Sludge Model No. 3

Abstract

In Activated Sludge Model No.3 (ASM3), it is hypothesized that all heterotrophic microorganisms (XH) can store substrate. However, in reality, both microorganisms with and without substrate storage capability (XH/STO and XH/S, respectively) could exist. If the ratio of XH/STO in activated sludge is influenced by operational and environmental conditions, kSTO (storage rate constant of heterotrophic microorganisms which is defined in ASM3) may not be a universal parameter and can change from case to case. In this study, polyhydroxyalkanoate (PHA) is assumed as the principal storage product, and the ratio of microorganisms with PHA production capability (XH/PHA) in various activated sludges was estimated by the dual staining of Nile Blue A (NB) and DAPI. It was shown that the ratio of XH/PHA in sludge varied among different municipal and laboratory activated sludges.