Operation Characterictics And Microbial Community Distribution Of Anammox In A Membrane Bioreactor

For the traditional biological nitrogen removal technology, it results expensive in those wastewaters with low biodegradable matter and high nitrogen concentrations. Nowadays the trend in development of treating wastewater with lower ratio of carbon to nitrogen is anaerobic ammonium oxidation(Anammox) process. In order to put it into practical use, Anammox inocula must be achieved and the biomass must be hold inside the reactor. Based on the summarizing the results of previous studies on Anammox, the influence of different sludges on the efficiency of Anammox process was studied in this paper. On the basis of those study, the operation characterictics and microbial community distribution of Anammox in a membrane bioreactor was analysed. The best operation of MBR in the Anammox process was also studied in this studied. The main results were as follows:(1) After 2-3 months of incubation, The enrichment of Anammox strains from the conventional sludge such as aerobic sludge, anaerobic granular sludge and anaerobic digestion sludge are observed in the R1, R2, R3; The removal rate of ammonium, nitrite and total nitrogen were 82 %, 92 %, 91 %; The concentration of effluent sludge were 1.34 gSS/d, 0.42 gSS/d, 0.95gSS/d; The volume index of sludge were 23.23 ml/gSS, 11.11 ml /gSS and 19.38 ml/gSS; Judged by the start-up time, R1was the shortest, followed by R2 and R3.(2) The VS/TS was changed from 0.67 to 0.77 during the Anammox process in MBR; At the end of the anammox reactor operation, the size of Anammox granular sludge was mainly concentrated in 0.2-1mm, experiment demonstrated that granular sludge played an important role in the Anammox process; and the nitrogen-loading rate amounted to 0.245 kgTN/(m3.d), and the removal efficiency of total nitrogen, ammonia and nitrite was 80%, 81%, 91 %, respectively. Cell lysis from heterotrophs was proposed to be one key factor influencing the membrane fouling in the first days, and the first days was remarkably higher than that the period of Anammox bacteria dominated the microbial community in the reactor.(3) During the hydraulic shock text, the HRT of MBR was gradually shorted from 14 to 7.9 h, the NH4+-N and NO2--N removal efficiencies were stable at about 75% and 85%, respectively. Anammox activities were good when temperature was 30-35℃and pH was 7-8. The optimal ascend velocity of flow is 1.8-2.3 m/h in this study. Consideration of nitrogen removal, operating costs, the simplicity of operation, the optimal operation mode was that the reactor was operated in cycles of 6 h , fed for 0.55 h, mixed for 5 h, settlement for 0.3 h, draw for 0.15 h.(4) The photographs showed that the seeding sludge were mostly rod bacteria while Anammox sludge was mostly spherical and rod in shape. Based on terminal restriction fragment length polymorphism (T-RFLP) analysis, the composition and relative populations of the microbial community changed obviously in association with the enrich of Anammmox. The enrichment of Anammox strains such as planctomyce, pirellula, gemmata, pseudomonas were found after enrichment in MBR.