Improving nitrogen and phosphorus removal and sludge reduction in new integrated sewage treatment facility by adjusting biomass concentration

Aiming at the practical problem of rural wastewater and excess sludge treatment difficulties, micro-pressure swirl reactor (MPSR) was employed to carry out the experiment on the treatment of sewage under five different biomass concentration (MLSS concentration) conditions (4.14, 6.05, 7.98, 11.45, 14.46 g/L). The results showed that the nitrogen removal and phosphorus removal and sludge reduction performance of the system showed an increase and then a decrease with increasing MLSS concentration, and 7.98-11.45 g/L was the optimal MLSS concentration range. In addition, parameters related to in situ sludge reduction were further examined, and the extracellular polymeric substance content and sludge dehydrogenase activity were negatively and positively correlated with sludge reduction, respectively. According to the microbial analysis, at suitable MLSS concen-tration, beneficial microorganisms (Tetrasphaera, Aeromonas, Candidatus_Competibacter) were enriched in the MPSR to facilitate the nitrogen and phosphorus removal and sludge reduction of the system. In addition, the potential gene(nirK, norB, nosZ) functions of the microorganisms were positively regulated. The increase in the expression abundance ratio of dissimilatory and anabolic nitrate reduction genes played a positive role in denitrification and sludge reduction of the system.