AUTOTROPH-HETERTROPH INTERACTIONS IN ACTIVATED SLUDGE: BIOAUGMENTATION FROM SIDE-STREAM TREATMENT

Successful engineering of bioaugmentation for wastewater treatment requires an understanding of microbial ecology. Therefore, the aim of this work was to examine one aspect of reactor ecology: potential interactions between heterotrophic bacteria and ammonia oxidizing bacteria. Microscopic observation, macroscopic observation, and molecular biology techniques were utilized to characterize bacterial community dynamics in laboratory-scale reactors simulating main-stream activated sludge treatment with bioaugmentation of biomass generated from sidestream treatment of anaerobic digester supernatant. Chemical oxygen demand and reduced nitrogen removal efficiency were used to characterize function of heterotrophic and autotrophic bacterial communities, respectively. Overall bacterial community structure is diverse and dynamic despite restricted sources of energy. Some of the diversity can be attributed to autotrophic bacteria as multiple populations of AOB were identified in all reactors. In contrast, AOB populations were very stable throughout the experiment, even despite nitrification instability which was experienced throughout much of the experiment.