| The increasing eutrophication problem is serious, and the nitrogen(N) remove from wastewater has become an inevitable requirement to meet the social development. However, traditional biological N-removal wastewater treatment plants(WWTPs) were capital and energy intensive. Therefore, it has become a hot issue in the field of water pollution control engineering to research and devel op the high efficiency and non-pollution sustainable biological N-removal technology. Anaerobic ammonium oxidation(anammox) is a novel microbial nitrogen process and an energy conservation and non-pollution technology, and has been widely studied all over the world. The research and application on the anammox technology is still limited in high-temperature and rich-ammonia wastewater treatment, while the report about low-ammonia wastewater of anammox is still relatively little.The main objective in this study is N-removal enhancement and corresponding microbial characteristics of anammox granular sludge with low-ammonia concentration. Firstly, we will explore the N-removal function via anammox process in traditional WWTPs. Secondly, further research will be carried out around strain accumulation, strengthen function and process operation. Meanwhile, the Mi Seq high-throughput sequencing technology was used to analyzed the regulation and difference of the microbial community structure in the key granular stages or in different process.The results will provide data support and theoretical guidance for low-ammonia wastewater.The seasonal investigations showed that anammox bacteria are widely distributed in traditional WWTPs(the most are in activated sludge tanks), the abundance of hzs B function gene was 105-107 copies/g VSS, anammox rate is 0.08-1.20 μmol N/(g VSS·h), the potential contribution of ammonia oxidation ratio is 0.11-16.3%, the average annual N-removal contribution is 2.1-6.6%(1-194.3 t N/yr), and the anammox performance in summer was higher than that in winter. The biodiversity of anammox bacteria is very low with only two genus, Brocadia is dominant. In nitrification process, compared with AOA, AOB has the ability to provide more NO2- for anammox bacteria, and Nitrospira as a NOB strain may be a more powerful competitors for key substrate of NO2- with anammox bacteria. In addition, anammox performance is mainly affected by the combination of microbial community structure, temperature, SRT, and COD, but not the key restricted factors. Among them, the hzs B-gene abundance, rate, and N-removal function of anammox bacteria were extremely positive correlation. These results showed that anammox bacteria has strong robustness, and it is widely distributed and work in the process of biological N-removal from wastewater.In order to effectively improve the anammox role to the N-removal function, we cultured anammox granule from excess sludge. The results showed that the anammox granular sludge mainly in 0.5-0.9mm particle size(93.7%) was successfully cultivated by 200 d operation. When the particle size is larger than 0.5 mm, the granular sludge achieved the rapid bacterial increasing, and the best performance of anammox abundance, activity and diversity appeared in particle size of 0.5-0.9mm, in which the abundance is 1011 copies/g VSS, 104-5 times as the inoculation, activity was the high level in natural environment, but bio diversity of granular sludge was significantly lower than that of sludge flocs while both were Brocadia mainly. It illustrates that the effective performance of anammox can be maintained by controlling the degree of granulation to ensure the best mass transfer efficiency. Also, rich-EPS is one of the key factors for anammox granular sludge formation, protein is the main component of all EPS layered, chromium lysine and tryptophan acid, accounted for 58.9% of the total amount of EPS; the vast most EPS belong to TB-EPS, accounting for 77.1% of the total amount of EPS.By inoculating anammox particles sludge, Amx-UASB and Amx-SBR reactors were successfully started up for continuous flow and intermittent type, respectively. As for Amx-UASB reactor, the disintegration and development of inoculated granular sludge led to the particle size of 0-2.5 mm, which can resist 187.2 L/d flow load and 144 L/d amplitude shocks. To Amx-SBR, inoculated granular sludge mostly disintegrated, but changed with the range of 0.2-0.9mm mainly by remodeling. Partial nitrification(PN) had been achieved fast by real-time control strategy in 20 d with the NO2- accumulation of higher than 90%. When partial nitritation(PN-SBR) is unstable, Amx-SBR had to face the competitive effects of denitrifying bacteria, so stable partial nitritation and suitable substance ratio is the core of starting up and stable operation of anammox process. In addition, Amx-SBR was more biodiverse than Amx-UASB, but both anammox functional bacteria were Brocadia, and Nitrosomonas and Nitrospira are main nitrifying bacteria, which symbiosis or competition with anammox bacteria based on constitute space and/or substrate; the biodiversity of PN-SBR, treating real wastewater, is adjacent to the minimum flora diversity level of anammox sludge cultivated with synthesis water, functional bacteria is Nitrosomonas, accounting for all the bacteria group was 17.2%, while Nitrospira accounted for only 0.01%. The complex and stable micro-ecological structure of anammox granular sludge realizes the efficient N-removal of low-ammonia wastewater. |
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