Nitrogen Removal Pathways And Microbial Diversity In A Hybrid Constructed Wetland

With the continuous development of rural urbanization, the scale of small towns in China is growing, but its scattered distribution, quantity, Once the ecological environment is damaged, it is difficult to recover. Constructed wetlands(CW) will be a reasonable option for treating small-scale town sewage and will be widely using, because of the lower investment simple equipment, easy control and low operation cost, and stable operation. Anaerobic ammonia oxidation(Anammox) is a biological reaction with NH4 +-N as an electron donor, NO2-- N as an electron acceptor, nitrogen as final product, which features low cost, low power consumption. In this thesis, the object is a novel hybrid CW, vertical-baffled flow wetland + horizontal subsurface flow wetland, which developed by Research team. On the basis of the relevant research has been completed in the Qinghe agricultural park wasterwater treatment plant by other members, To explore the Anammox changes affected by seasonal in order to provide technical support for the design of the application of CW system.The paper has analyzed the seasonal law of conventional index of the plant as a whole and each structure. The temperature of summer was significantly higher than in other seasons, above 26 ℃, the lowest in winter, between 11℃~13℃, spring and autumn has same temperature, between 17 and 22 ℃; Effluent p H of the four seasons are within 7 ~ 8 neutral. The p H ranges between 7~8 in seasons.The paper has analyzed the seasonal law of pollutants biological removal of the plant as a whole and each structure, especially the nitrogen biological changing rule. Results show that the sewage plant has good effect for removal all kinds of pollutants in seasonal. In the spring and winter, influent COD, TP, TN, NH3-N concentration significantly higher than summer and fall; Nitrate have different degree of enrichment after HSFW.HSFW is the most important part to remove pollutants in the novel hybrid CW.The paper analyzed variation law of DO and ORP along the HSFW with repeating aerobic, anoxic and anaerobic conditions, the NH3-N concentration is between 20mg/L to 9mg/L, the NO2-N concentration remains below 0.25 mg/L,during the research,which may contribute to the the anammox to be tightly correlated with rates of denitrification.The paper designed 15 N isotope tracer experiments, using GC-MS to test the amount of 29N2 and 30N2. Finding that the proportion of Anammox and denitrifying reaction in 0.75:1 ~ 0.9:1, the removal rate of C/N around 1.0, between June and September in 2014.High bacterial diversity was observed in the substrates of HSFWs bed. Illumina high-throughput sequencing analysis of the samples yielded a total of 338 bacterial in the studied bed. Based on 3% cutoffs, the richness of total bacterial community(Chao) were estimated about 338 and that were almost similar to the abundance-based coverage estimator(ACE) index values, indicating coverage(99.8%) of most bacteria in the system. Based on the sequencing data obtained from substrates analysis, Thiobacillus was the most dominant genus followed by Nitrospira, Rhodocyclaceae and Xanthomonadales respectively. Thiobacillus, Nitrospira associated with biological denitrification; Rhodocyclaceae has the function of biological p Hosp Horus removal; Anaerolineaceae has proved in the methane-producing biological system, degraded the carbohydrates and other cellular materials(e.g., amino acids).To identify the presence of nitrogen removal bacteria, sequences obtained from high-throughput sequencing were analyzed and sequences with greatest similarity to reference strains were identified in the Gen Bank database. A total of 1892 16 S r RNA gene sequences were belongs to nitrogen removal bacteria and could be classified under different known nitrogen removal pathway; ammonium oxidizing, nitrite oxidizing, heterotopic denitrification, autotrop Hic denitrification and anammox bacteria respectively. PHylogenetic analysis indicated that, Among all autotrop Hic denitrifiers, majority of sequences(944) were closely related to Thiobacillus denitrificans with about 96% sequence similarity. Moreover, two anammox genus were obtained, one was closely(~100%) related to the Candidatus ―Anammoxoglobus propionicus‖ and anther had the similarity of 99% to the Candidatus Brocadia fulgida‖. It turns out that, the correlation between anammox and denitrification has Has happened in HSFW, which is primarily between thiobacillus anammox bacteria.