| In recent years, with the rapidly industrial development, human discharge huge mount of nitrogen compounds into water environment. Unfortunately, the nitrogen brings serious problems to the water environment, such as: water eutrophication, harm to mankind and aquatic mammals, and increase in cost of wastewater treatiment. Therefore, the nitrogen removal of wastewater has been an area of immense concern all of the time. Because of the several shortcomings of conventional nitrogen removal process, scholars from home and abroad devoted themself to develop noval nitrogen removal technique and process. While, heterotrophic nitrogen removal technique become a hot research filed among them.In order to get better understanding of physiological characteristics of Alcaligenes faecalis strain NR, kinetic modeling of bacterial growth and substrates removal were studied and the kinetic constants were obtained. On the basic of batch shaking experiments, the Continuous Stirred-Tank Reactor(CSTR) was built with addition of strain NR. The performance of treating synthetic wastewater was investigated in CSTR by setting different ratio of C/N, Hydraulic Retention Time(HRT) and ammonium concentration. Meanwhile, the Mi Seq sequencing technique was utilized to investigate the microbial community structure due to open system was adopted in CSTR. Therefore, the distribution of microorganism could be obtained.The kinetic modeling of bacterial growth and substrates removal were studied and the kinetic constants were obtained. The growth phases of strain NR could be divided into five phases: lag phase, accelerated growth phase, exponential growth phase, moderating growth phase and stationary phase. After comparing a number of kinetic models, Contois-Contois model and Teissier-Contois model were both considered to be the appropriate one to model kinetics characteristics of strain NR with treating both NH4+-N and TOC as its limiting substrate. The kinetic constants were obtained by solving multiple equations with regression. For the double Contois model: = 0.16 h-1, BC = 0.61 g TOC/ g biomass, BN = 0.018 g NH4+-N/ g biomass; while for the Teissier- Contois model: = 0.16 h-1, BC = 0.64 g TOC/ g biomass, KN = 17.95 mg/L. The constants relevant to substrates removal are as follows: (/) = 0.99 g biomass/ g TOC, (/) = 15.98 g biomass/ g NH4+-N. Maintain coefficient for TOC and NH4+-N were 0.0021 g TOC/ g biomass/ h and 0.00004 g NH4+-N/ g biomass/ h respectively.The performance of treating synthetic wastewater was investigated by adding strain NR into CSTR. In the phase of 80 mg/L influent ammonia nitrogen(phase A and B), the performance of efficient substrates removal was shown in CSTR, and about 78% of NH4+-N and 95% TOC were removed respectively. By this time, the assimilation of nitrogen was around 30% of influent nitrogen. In the phase of 150 mg/L and 300 mg/L influent ammonia nitrogen(phase C and D), the CSTR still maintain the efficient ability to remove substrates. The removal rate of NH4+-N and TOC were both up to 90%. However, the assimilation of nitrogen increased to above 60%. In the phase of 500 mg/L influent ammonia nitrogen(phase E), the removal rate of NH4+-N and TOC decreased to 75% and 70% due to the effect of toxic action of high concentration of ammonia nitrogen. While, the assimilation of nitrogen decreased to about 40%.The microbial community structure was investigated during the operation of the CSTR in open system. 4 stable genera were detected in reactor after long period of operation: Marinobacter, Klebsiella, Pseudomonas and Achromobacter. These four genera were widely reported as heterotrophic nitrogen removal bacteria, and that was the reason why the reactor kept high efficiency of removing substrates. Among them, Achromobacter was found to be dominant bacteria and its proportion was maintained between 55% and 66%. However, the proportion of the target genus Alcaligenes faecalis strain NR was considerably low and which means the strain NR could not grow as dominant bacteria in the CSTR. |
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