Microbial Mechanism On Upflow Microaerobic Sludge Blanket Reactor for Municipal Wastewater Treatment

In this study, 16S rDNA-based DGGE and clone library were used to investigate the microbial mechanism on the upflow microaerobic sludge blanket reactor (UMSB) for domestic wastewater with an aerobic reactor (AR) as control, with particular emphasis on nitrification. The oxygen half saturation constant (Ko) of activated sludge was measuured to compare the oxygen affinity of sludge obtained from these two reactors at different experimental phases. Like the AR, the UMSB achieved a 60% energy saving, and a COD and NH3-N removals of 98% and 90% respectivity, at DO=0.7-0.9 mg l-1. The majority of Nox-N in the effluent was NO3-N for the AR but NO2-N for the UMSB. The activated sludge was dominated by nitrite oxidation bacteria (NOB) in the UMSB and Ammonia-Oxidizing Bacteria (AOB) in AR, respectively. The low DO in the UMSB favors the growth of filamentous bacteria, e.g., Sphaerotilus, Planctomycetes, Chloroflexi, however, they did not lead to filamentous bulking in the UMSB. Generally, the activated sludge in the UMSB has low Ko values than that in the AR.