Characteristics of nitrogen and phosphorus removal and microbial community structure in hybrid biofilm system

Abstract

Bench scale sequencing hybrid biofilm reactor (HBR), fed on synthetic wastewater, were used to study the characteristics of nitrogen and phosphorus removal with different sludge loads. It was found that under the condition of the sludge load at 0.35 kg (COD Cr)·kg (MLSS)·d , the system had a good performance on nitrogen and phosphorus removal, and the total nitrogen (TN), total phosphorus (TP) and ammonia nitrogen (NH 4 -N) removal efficiency were 96%, 89% and 96%, respectively, all higher than the counterparts in the sequencing batch reactor (SBR) process. The suspended sludge contributed the main nitrification process with the contribution ratio of 1.66 to the biofilm. However, the biofilm influenced the denitrification and phosphorus degradation processes significantly. The contribution ratio from the biofilm to the suspended sludge on denitrification, phosphorus releasing and uptaking were 2.19, 3.50 and 3.76, respectively. The microbial community structures of the treatment reactor were monitored by PCR-amplified 16S rDNA and denaturing gradient gel electrophoresis (DGGE) analysis of the resultant PCR products. The profiles of DGGE showed that the HBR was rich in nitrogen and phosphorus removal functional bacteria and the correlation coefficient between the suspended and biofilm microbial community was only 73%. The results indicated the close relationships among different microbial communities in the HBR. The relationship between the structure of microbial community and its functions may be characterized with the variation analysis.