MICROBIAL COMMUNITY ANALYSIS OF ANOXIC-OXIC-SETTLING-ANAEROBIC (A plus OSA) SLUDGE REDUCTION PROCESS USING PLFA AND PCR-DGGE METHODS

The anoxic-oxic-settling-anaerobic (A+OSA) process, modification of the anoxic-xoic (AO) process by inserting a sludge holding tank (SHT) into the sludge return line, could achieve excess sludge reduction. The microbial communities of the A+OSA process were investigated using combined phospholipid fatty acids (PLFAs) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) methods. The PLFA-based microbial biomass of SHT was significantly lower (p<0.05) than that of other samples of the A+OSA process and AO process. Gram-negative (G-) bacteria and aerobe biomarkers dominated in the A+OSA and AO process except SHT in which Gram-positive (G+) bacteria and anaerobe dominated. Results of DGGE analysis suggested that 6 classes alpha-proteobacteria, beta-proteobacteria, Sphingobacteriia, Cytophagia, Ignavibacteria, Flavobacteria, were identified, and beta-proteobacteria were main microorganisms in the two processes. This study suggested that sludge decay in the SHT could be the main reason for the sludge reduction in the A+OSA process. The microgroups including alpha-proteobacteria, beta-proteobacteria and Sphingobacteria were involved in the sludge reduction.