Impact of nutrient removal on microbial community in bioretention facilities with different underlying types/built times at field scale

Abstract

As the bioretention facilities have been extensively built in the construction of “Sponge City” in China, urban non-point source pollutants could be effectively controlled. The influences on microbial community in three bioretention facilities with different underlying types/built times at field scale were studied. The results showed that nutrient loads in road runoff were 1.1–3 times higher than of roof. Compared with the other two rain gardens, the bioretention tank (BT) was relatively stable and showed >90% nutrient load reduction rates. The nutrients brought by the stormwater runoff changed the original habitat in the soil. Nutrient removal led to the deterioration of the living environment of microorganisms, and then the number of microorganisms and diversity changed. Ten dominant bacteria species were found in the facilities, and Proteobacteria were the most dominant bacteria phyla, with the relative abundances all >30%. Suspended solids were found to be the most important factor and had a high correlation to the most dominant microorganisms. With the increased operation period, the microorganism species tended to be concentrated on Proteobacteria, resulting in decreases of other functional microorganisms. The bioretention facility with the road underlying had the lowest microbial diversity, and the built time was the factor that had the greatest impact on microbial diversity. Based on these results, the future design and construction of bioretention facilities should consider the risk after nutrients entered the bioretention facility and the changes in microbial diversity.