Quick start-up of partial nitrification in a novel anaerobic/ pulse washout (APW) process for treating municipal wastewater

This study proposed a novel anaerobic/pulse washout (APW) process that can rapidly inhibit nitrite-oxidizing bacteria (NOB) and enrich ammonia-oxidizing bacteria (AOB) to achieve the quick start-up of partial nitrification in an activated sludge system. The results showed that the start-up period of partial nitrification in the APW process (20 days) was shorter than that in the process operated without APW (45 days). Analysis of the microbial communities revealed that the activity and relative proportion of AOB (AOB/(AOB plus NOB)) in the APW process (88.64 mgN·L−1·d−1, 82%) were significantly higher than those in the process without APW (75.82 mgN·L−1·d−1, 62%). Furthermore, the directional change in the composition of extracellular polymeric substances (EPS) and intracellular polymeric substances of microorganisms under APW can affect the metabolic pattern and growth of nitrifiers, thereby, accelerating the start-up of partial nitrification. To further verify efficiency, the APW process was used to treat actual low carbon/nitrogen (C/N) sewage. The results showed that partial nitrification and denitrification were quickly achieved with high nitrogen removal capacity. Thus, this study offers a new process to improve partial nitrification and denitrification and develop a theoretical basis with which to solve low C/N issues in municipal wastewater treatment plants.