[Micro-ecology mechanism on microaerobic treatment performance at various influent COD concentrations or HRTs]

A lab-scale continuous experiment was designed to investigate the effect of influent COD concentrations (11,000, 15,000, 30,000 mg/L) or hydraulic retention time (HRT 42, 25 h) on the microareobic treatment performance of simulated high-strength organic wastewater. The molecular microbiological technologies, including Fluorescent in-situ hybridization-Flow Cytometry (FISH-FCM), Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE), and Biolog-FF assay method, were used to detect the variation of microbial community in the aerated column during the four pseudo-steady-state periods. The yeast contents remained > 99.9% throughout the overall experimental periods according to FISH-FCM. Increasing influent COD concentration brought on a rising MISS (2.0-7.3 g/L) and a reduced specific COD removal rate [2.3-1.7 kg/(kg x d)], structural (PCR-DGGE)/metabolic (Biolog FF) diversity index values of fungal community in the aerated column had an increase of (2.05-2.19)/(4.42-4.45). Shortening HRT brought on a reduced MISS (7.3-6.0 g/L) and a rising specific COD removal rate [1.7-2.8 kg/(kg x d)], structural (PCR-DGGE)/metabolic (Biolog FF) diversity index values of fungal community had a decrease of (2.19-0.79)/(4.45-4.36). Increasing influent COD concentration or shortening HRT has an absolutely adverse effect on the microaerobic treatment performance and micro-ecology in the aeration column although either of them can increase influent COD loading up to a higher level.