Effect of Aeolosoma hemprichi on excess activated sludge reduction

In order to stabilize the growth of A. hemprichi and minimize the sludge production through biological predation, A. hemprichi was inoculated in batch and continuous experiments to investigate the growth characteristics and the effect on sludge reduction in this study. Various available volatile suspended solid (AVSS) concentrations were obtained after the ultrasonic irradiation on pre-sterilized sludge. It was found the density of A. hemprichi was proportionate to AVSS concentration. A. hemprichi reached the maximum density when AVSS concentration was more than 3000 mg/L. No obvious difference was found between the initial specific growth ratio (μ) of A. hemprichi at various AVSS concentrations. When N > 0.5NL, μ decreased with the increase of A. hemprichi and Logistic model was adopted to fit the growth of A. hemprichi. Sludge reduction rate was correlated with both the growth rate and the density of A. hemprichi. The results indicated the sludge reduction rate was maximum at the density of 315 ind./mL. Sludge retention time (SRT) could effectively control the growth density of A. hemprichi in continuous tests.