Effect of COD level and HRT on microbial community in a yeast-predominant activated sludge system

This study was conducted to compare the effect of influent chemical oxygen demand (CODin) level and hydraulic retention time (HRT), two primary components of influent COD loading rate (CODLR), on the structure and function of sludge microbial community in a yeast-predominant activated sludge system (1 m H × 0.2 m D) for synthetic industrial wastewater. A combination of polymerase chain reaction-denaturing gradient gel electrophoresis with BIOLOG community-level physiological profiles was used. At higher CODLR and higher CODin and identical HRTs, more microbial species were supported and could metabolise a greater variety of carbon sources in the aerated column. Conversely, a shorter HRT at identical CODin supported fewer microbial species, which resulted in the metabolism of fewer carbon sources.