Start-up,Operation And Nitrogen Removal Performance Of Continuous Multi-stage Partial Nitrification/Anammox Process

Reducing nitrogen compounds in wastewater is one of the important measures to improve water environment and water quality.Compared with the traditional nitrification/denitrification process,the partial nitrification/anammox process(PN/A process for short)has the advantages of low cost and high efficiency when treating wastewater with high ammonia nitrogen concentration and low carbon to nitrogen ratio.In the PN/A process,on the one hand,it is difficult for the PN process to stably control the nitrosation rate of the effluent,which affects the subsequent Anammox nitrogen removal performance;On the other hand,when anaerobic ammonium oxidizing bacteria(An AOB)and ammonia oxidizing bacteria(AOB)denitrify synergistically in one reactor,due to their different environmental requirements,it is difficult to enrich at the same time,thus affecting the wide application of PN/A process.In this paper,an integrated continuous multi-stage PN/A process reactor was constructed,and the start-up,operation regulation and nitrogen removal performance of the reactor were deeply studied.The main conclusions are as follows:(1)An integrated multi-stage aerobic-biofilm/anoxic-particle reactor(MOBAPR)was constructed.The rapid start-up of the PN process was successfully achieved within 8 days by setting up anaerobic/aerobic compartments in the MOBAPR and using intermittent aeration in the aerobic chamber.After 47 days of stable operation of the PN process,the PN/A process was successfully started,and the nitrogen removal efficiency(NRE)was 83.41%±2.45%.16 S r RNA gene sequencing revealed that the simultaneous enrichment of AOB(27.09%)and An AOB(9.99%)in MOBAPR was achieved.During the operation of the PN/A process,the gas-liquid ratio(aeration rate to water inflow rate)can not only improve the nitrogen removal performance of MOBAPR,but also simplify the PN/A process operation by replacing DO control.(2)To explore the adaptability of MOBAPR’s PN/A process to seasonal fluctuations in wastewater quality and quantity,low temperature and starvation recovery studies were conducted.The results show that the long-term stable operation of the PN/A process is realized by controlling the gas-liquid ratio.During the low temperature(about 17±5℃)operation of the PN/A process,the overall nitrogen removal efficiency of MOBAPR was significantly inhibited,but the effect of low temperature on PN/A process can be alleviated by appropriately increasing p H.Furthermore,the PN/A process denitrification performance of MOBAPR was rapidly reactivated within 7 days after starvation of the microbial flora for 52 days.The results of 16 s high-throughput sequencing showed that after long-term operation of the PN/A process in MOBAPR(Day 341),the relative abundance of An AOB in each reaction compartment reached 41.00%,29.91%,30.83% and 24.75%,respectively,achieving efficient enrichment of functional bacteria.(3)MOBAPR was systematically optimized,that is,an aerobic-biofilm/ anoxic-particle nitrogen removal system(OANRS)consisting of MOBAPR and aeration time/p H control strategies was constructed.OANRS combines the advantages of single-stage and two-stage PN/A process,and successfully realizes the rapid start-up of PN/A process within 41 d.After the PN/A process is successfully started,OANRS can effectively inhibit NOB by utilizing the substrate competition between microorganisms.And under the conditions of high DO(2.1±0.4 mg/L)and low p H(6.86±0.10),the PN/A process can still be operated efficiently and stably.High-throughput sequencing results showed that An AOB was efficiently enriched in each compartment on the 98 th day(20.42±15.88%).The relative abundance of Candidatus Kuenenia(An AOB)in the hypoxic compartment R4 was as high as 43.13%.In addition,it was confirmed by sludge speciation analysis that the aerobic-biofilm/anoxic-particle sludge form in MOBAPR can better retain biomass,thereby promoting the efficient enrichment of functional bacteria.