Succession of nitrogen and phosphorus removal functions of sludge and biofilm in low-temperature sewage treatment

In this study, the succession of nitrogen removal capacity of sludge and biofilm was explored at different temperatures. The results revealed that a decrease in temperature from 15 to 5 degrees C did not significantly alter the removal efficiency of chemical oxygen demand (COD) and total phosphorus (TP), while that of total nitrogen (TN) was drastically reduced. Meanwhile, biofilm biomass did not decrease with decreasing temperature, and microbial adhesion and proliferation were highest on compact polyurethane fillers (B filler). The microbiological analysis determined that the distribution of dominant nitrogen removal functional microorganisms progressively shifted from sludge to biofilm as the temperature decreased. Additionally, predictive analysis of microbial function exposed that biofilms attached to B fillers were the primary contributors to nitrogen removal at 5 degrees C. Taken together, this study provides new insights into the culture of low-temperature-resistant bacteria in reactors at low temperatures.