Optimization Of Key Bacteria In The Combined Partial Nitrification-anammox SBR Process

As an innovative process with advantages of no external carbon source addition,no CO2 emission, less greenhouse gas (GHG) nitrous oxide emission and less sludge production, anaerobic ammonia oxidization (Anammox) process becomes the most promising process for biological nitrogen removal. However, there are challenges for promoting application of the Anammox process in practice, such as slow growth rate and low activity of the Anammox bacteria, long-term start-up, and hard to stable operation.The following aspects were mainly focus on above problems. Firstly, the activated sludge in the upflow anaerobic sludge blanket (UASB) of Anammox process was selected to microbiologically characterize the bacteria with SEM and modern biological analysis methods. Secondly, the activated sludge in the combined partial nitrification-anammox SBR (CPNA) was used to test and compare effects of dosing Fe2+, GOs and Fe3+ on the effects of nitrogen removal, activity of Anammox bacteria and microbial characterizations by anaerobic batch test. Thirdly, three key bacteria, such as ammonia oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB) and Anammox bacteria in the CPNA process were investigated by SBR reactor test to optimize the key microbial structure in the CPNA process for improving the nitrogen removal performance. The main conclusions are as follows:(1) The results of microbial characterization of the Anammox process based on UASB showed that the microbial morphology in the UASB Anammox process during the start-up gradually changed from rod shape to clustered ellipsoid. During the start-up of the USAB, the alpha diversity index increased firstly and then decreased,indicating that functional bacteria in the reactor gradually increased and their function gradually specific. In the UASB, the main phylum was Planctomycetes, and the abundance increased from 13.07% to 54.70% which became the most dominant phylum,and the Candidatus Kuenenia genera of Anammox bacteria abundance was up to 48.77%when the reactor started up. Functional abundance analysis also showed that the main metabolic abundance showed a rising trend during the start-up.(2) The results of batch test of enhancing Anammox process by dosing Fe2+, GOs and Fe3+ showed that the effects of nitrogen removal and abundance of Anammox bacteria in the GOs group was the best, and the enhancement of Anammox bacteria activity in the Fe2+ group was the best. GOs dosing has significantly effect on the nitrogen removal efficiency. The average total nitrogen removal efficiency was 22.71%higher than the control group, but the average total nitrogen removal efficiency of Fe2+and Fe3+ were only 5.69% and 1.72% higher than the control group, respectively. The abundance of the Planctomycetes was increased by 2.93 times compared with the seed sludge, 44.51% higher than the control group by dosing GOs. But the abundance of the Planctomycetes in the addition of Fe2+ group was only 1.03% higher than the control group, and its abundance of Fe3+ group was lower than the control group. The treatment of Fe2+, GOs and Fe3+ dosing affected the average Anammox bacteria activity, and the enhancement were 82.10% higher, 50.54% higher and slightly lower than the control group, respectively, and dosing Fe2+ has significantly effect on the enhancement of Anammox bacteria activity.(3) Aiming at coexistence optimization of the AOB, NOB and Anammox bacteria in the CPNA reactor, not only achieving enrichment of the AOB and Anammox bacteria,but also approaching NOB elimination, the results of a laboratory-scale CPNA reactor showed that both Fe2+ and NH2OH dosing could improve the activity of AOB, and the addition of NH2OH could effectively inhibit NOB activity. The maximum removal efficiency of total nitrogen in the doisng NH2OH group was 42.54%, and the highest total nitrogen removal efficiency of the addition of Fe2+ was 25.90%, and the total nitrogen removal efficiency of control group was under 10% during this period. The effect of dosing NH2OH on the community structure of CPNA was the best.