Deciphering of organic matter and nutrient removal and bacterial community in three sludge treatment wetlands under different operating conditions

Abstract

Sludge treatment wetlands (STWs) can effectively stabilize sludge, but the microbial community structure in this process is not well characterized. The purpose of this study was to investigate the characteristics of organic matter and nutrient removal and bacterial community in sludge treatment wetlands for treating sewage sludge. Three STWs units included unit STW1 with aeration tubes, unit STW2 with aeration tubes and reed planting and unit STW3 with reed planting. The degradation of organic matter and nutrient, sludge dewatering performance and microbial community dynamics in STWs were examined in feeding and resting periods. Our results showed that during the entire process of the experiment, total solids (TS) in STWs increased to 24-31%, volatile solids (VS) in STWs reduced to 43-47%, while the total kjeldahl nitrogen (TKN) and total phosphorous (TP) concentrations in STWs decreased to 25.1-35.5 mg/g d. w and 5.4-6.2 mg/g d. w. However, the removal efficiencies of organic matter and nutrient in STWs in the feeding period were higher than those in the resting period. Meanwhile, unit STW2 has the best removal performance in organic matter and nutrients during the whole experiment. Microbial community analysis using Illumina MiSeq sequencing technology showed that growth of plants in STWs improved bacterial diversity and richness which corresponded to high removal rates of organic matter and nutrient. Besides, principal coordinate analysis (PCoA) showed that the bacterial community composition in STWs obviously altered between the feeding and the resting periods.

Keywords: Microbial community; Nutrient removal; Organic matter removal; Sewage sludge; Sludge treatment wetlands.