The Start-up Of SNAD Process And The Characterizations Of Microbial Community In MBR

SNAD(simultaneous partial nitrification, Anammox and denitrification) process is a new biological technology which can remove ammonia and COD synchronously. It not only has many advantages over new autotrophic nitrogen removal processes, but also improves the nitrogen removal efficiency with the introduction of denitrifying bacteria, and better to improve water quality. Its research and application is more relevant to practical engineering.At present, the research on SNAD process more concentrated in the low C/N wastewater treatment, with high C/N, especially in the treatment of urban sewage with low ammonia are rarely reported under ambient temperature. The large amount of COD could inhibit autotrophic bacteria(AOB, Anammox bacteria), which makes the SNAD technology applied to high C/N wastewater treatment restricted. Therefore, study the effect of different organic carbon concentration on the SNAD technology has great significance, and provide theoretical basis for urban sewage treatment. MBR rely on the principle of membrane permeability, can prevent loss of sludge, suitable for AOB and Anammox bacteria such as doubling time long microbial growth, to speed up the startup time.In view of this, this research uses the MBR reactor, firstly by the fast start-up of CANON(Completely Autotrophic Nitrogen removal Over Nitrite) process to start the SNAD process under low concentration of organic carbon. Then the effects of different organic carbon concentration on the SNAD process was discussed by gradually increasing the organic carbon concentration. At last, the SNAD process transited to treat urban sewage with low ammonia nitrogen. At the same time, from biological perspective, the characteristics of functional microbial community structure in the reactor were studied by the use of PCR-DGGE molecular biology techniques.To start up CANON process, conventional activated sludge was inoculated to an MBR and the reactor was operated intermediately at ambient temperature. Under NH4+-N=200mg/L, the reactor experienced partial nitration stage and Anammox stage, the CANON process was finally started successfully. Besides, the characterization of functional microbes in stable CANON process was analyzed using PCR-DGGE techniques. The results showed that the CANON process was successfully started up by 36 days, the ammonium removal rate and total nitrogen removal rate were finally kept at around 99% and 84% separately and the maximal nitrogen removal rate can reach 0.41kg/(m3·d). DGGE profiles showed Nitrosomonas and Candidatus Kuenenia stuttgartiensis were predominant in reactor and the two kinds of microbial were together to finish the efficient autotrophic nitrogen removal depend on synergy in the MBR.After the successful start-up of CANON process, the test changed into a continuous flow. By gradually reducing ammonia nitrogen concentration to 150 mg/L, 100 mg/L, to study the effect of different concentration of ammonia nitrogen on the CANON process. During the run, cycle experiments were carried out to study the influence of different inorganic carbon concentration on the CANON process, and determine the best IC/N. The results showed that under certain ammonia surface load, nitrogen removal ability associated with dissolved oxygen solubility. When the aeration is 0.2 m L/min and the influent NH4+-N concentration is 150 mg/L, nitrogen removal efficiencies was best and the ammonium removal rate, total nitrogen removal rate and the maximal nitrogen removal rate were finally kept at around 99%, 84% and 0.41 kg/(m3·d) separately. Cycle experiments show that: high concentration of inorganic carbon benefit the operation of the CANON process. NH4+-N=200 mg/L and IC=480 mg/L(IC/N=2.4) was better than lower inorganic carbon concentration to speed up reaction rate of the CANON process.After the CANON process into continuous flow, SNAD process was started with glucose as a source of organic matter. The effect of different organic substrate concentrations on nitrogen removal in SNAD was investigated by gradually increasing COD concentration and by adjusting aeration and HRT to improve the effluent water quality. Besides, the change of microbial community was observed by PCR-DGGE techniques. The results and DGGE profiles showed that: When C/N=0~2, the increase of organic carbon concentration did not restrain AOB and Anammox bacteria and affect the category species of them. On the contrary, nitrogen removal rate was improved through denitrification. Total nitrogen removal rate and nitrogen removal rate were about 67% and 0.34 kg/(m3·d) separately. Under the operation of C/N=3~4 Anammox bacteria had no change, but AOB was inhibited and the category species was reduced, resulting the decrease of nitrogen removal efficiency. Total nitrogen removal rate and nitrogen removal rate were about 72% and 0.24kg/(m3·d) separately right now. With the increase of COD concentration, the effluent COD concentration changed in a range of 9.0~14.0 mg/L and the COD removal rate increased, which in more than 95%. Nitrosomonas and Candidatus Kuenenia stuttgartiensis were always predominant in reactor and the two kinds of microbial were together to finish the autotrophic nitrogen removal.When applied the SNAD process to sewage treatment, influent was 1/2 artificial water and 1/2 sewage at first, after all the water was domestic sewage, and by adjusting aeration and HRT to improve the effluent water quality. Besides, the change of microbial community was observed by PCR-DGGE techniques. The results and DGGE profiles showed that: Due to a large number of aerobic heterotrophic bacteria was introduced in sewage, the activity of AOB was further restrained and its species were further reduced. But anammox bacteria were still not affected. Total nitrogen removal rate and nitrogen removal rate were about 73% and 0.17 kg/(m3·d) separately with nitrogen removal ability declining. The effluent COD concentration changed in a range of 30.0±3 mg/L and the COD removal was about 90%. Nitrosomonas and Candidatus Kuenenia stuttgartiensis were still predominant in reactor and the two kinds of microbial were together to finish the autotrophic nitrogen removal.