Causes and control of sludge bulking in high load activated sludge process
AN Ying1, ZHANG Hui-min1, LIU Yun2, CHEN Guang2, TANG Chen1, ZHOU Zhen1
1. College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai 200090, China; 2. Shanghai Chengtou Waste Water Treatment Co., Ltd., Shanghai 201203, China
Abstract：To investigate the causes of sludge bulking during high load operation of activated sludge and the control effect of adding vanillin, this study examined the overall changes in microbial community, filamentous bacteria genus, extracellular polymeric substance secreting bacteria genus, and functional gene clusters involved in exopolysaccharides synthesis when operating under conventional load or high load with or without vanillin addition. The results indicated that after sludge bulking occurred, there was a decrease in the proportion of proteins to polysaccharides in extracellular polymeric substances. This reduction limited the ability of proteins to act as a biological flocculant and resulted in poorer settling performance of the sludge. The causes of sludge bulking during high load operation were attributed to filamentous bacteria dominated by Sphaerotilus and viscous bulking led by Flavobacterium. The addition of vanillin effectively inhibited the proliferation of Sphaerotilus but still allowed for viscous bulking dominated by Thauera and Zoogloea. Metagenomic sequencing analysis revealed that the abundance of alg, eps, and pel functional gene clusters involved in exopolysaccharide synthesis increased by 0.4~0.5 times, 0.8~1.1 times, and 10.3~15.7 times, respectively. These findings suggest that these gene clusters may be potential factors contributing to the substantial increase in exopolysaccharide content observed in bulking sludge.
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