Impacts of Sludge Characteristics on Anaerobic Digestion with Microwave Pretreatment and Archaeal Community Structure Analysis

Abstract

Sludge characteristics is an important factor in sludge pretreatment and anaerobic digestion (AD) efficiency. Therefore, waste sludge of anaerobic-anoxic-aerobic (A2O) and A2O-membrane bioreactor (MBR) wastewater treatment processes from a full-scale wastewater treatment plant were taken, and the variations of sludge characteristics and performance during microwave pretreatment and AD were compared. The succession of archaeal community structure during the sludge treatment was also investigated. A2O waste sludge showed better biodegradability than A2O-MBR waste sludge did, with 16.4% higher organic matter content (66.4% vs. 50.0%), soluble chemical oxygen demand (COD) (1.24 fold), soluble protein (2.02 fold), and polysaccharides (4.84 fold). Although the efficiency of microwave pretreatment for A2O-MBR waste sludge was better than that for A2O waste sludge, the latter sludge produced 26.1% more methane than the former did. The two types of waste sludge showed different archaeal community structures. The abundances of Methanothrix and Methanosarcina in A2O-MBR waste sludge were 3.68% and 19.73% higher than that in A2O waste sludge. The richness and evenness of archaeal communities slightly changed after pretreatment, but significantly changed after AD. The Chao1 index increased by 54.0%-68.8% after AD, whereas the Pielou index decreased by 16.2%-34.6%. Redundancy analysis showed that the organic components of waste sludge contributed to the succession of archaeal community structure.