The treatment effect and denitrification mechanism of low-temperature and low-carbon source municipal wastewater treated by micro pressure swirl reactor

To solve the practical problem of the difficulty of denitrification of urban sewage caused by low-temperature and low-carbon sources, the micro-pressure swirl reactor (MPSR) was used to carry out a simulation study of low-carbon source sewage treatment when the influent temperatures were 15, 12, and 10 °C. The results showed that the MPSR process had the best sewage treatment effect at 12 °C, and the average removal rates of COD, NH4+-N, TN, and TP were 85.93 %, 99.17 %, 76.4 %, 94.78 %. Through the study of the denitrification process, it was found that the main composition of TN in the effluent was changed from NO3−-N to NO2−-N at 12 °C, and the MPSR system achieved short-cut nitrification. The DO duration results suggested that a larger low DO range and a longer low DO duration promoted the formation of short-cut nitrification at 12 °C. When the temperature further dropped to 10 °C, the short-cut nitrification of the system was inhibited by the increase of DO. The Niabella was a genus of bacteria involved in nitrification in MPSR system, and its large number ensured the low-temperature nitrification effect of MPSR. The existence of denitrifying phosphorus removal bacteria (Dechloromonas and Rhodoferax) ensured the removal effect of nitrogen and phosphorus in the system. Based on metabolic pathway analysis, it was confirmed that the MPSR system achieved short-cut nitrification under low-temperature and low-carbon sources, which the carbon source consumption was saved and the denitrification effect was improved. [Display omitted] •The MPSR system achieved short-cut nitrification under low-temperature and low-carbon sources.•The larger low DO range and a longer low DO duration promoted the formation of short-cut nitrification at 12 °C.•Niabella was the nitrification bacteria in the MPSR and it was more suitable for low-temperature.