Simulanous Sulfur-Oxidizing Autotrophic And Heterotrophic Denitrificarion Process For Nitriate Removal And Its Molecular Ecology

Nitrate pollution is becoming increasingly prominent in groundwater. Long-term consumption of high-concentration nitrate groundwater will cause methemoglobinemia, also has a cancer risk. Sulfur-oxidizing autotrophic denitrification process has been widely used, but the process will produce sulfate, usually causing the excessive emission of sulfate. In order to improve the denitrifying performance and control excessive sulfate production, in the present study simultaneous sulfur-oxidizing autotrophic and mixotrophic denitrifying anaerobic fluidized bed membrane bioreactor (SAMD-MBR) was established. The effects of different carbon sources on nutrient removal and final products were investigated in the present study. The rt-PCR and454pyrosequencing analysis were constructed to elucidate microbial community structure, and analyze the response of the microbial community to the macro performance.The membrane and anaerobic fluidized bed bioreactor has good performance for nitrate removal. The NO3--N removal efficiency was up to100%during the whole operation. In the methanol-based and ethanol-based SAMD-MBR reaction systems, the produced sulfate could be controlled under250mg·L-1. When the NO3--N influent concentration is about80mg·L-1, the produced sulfate was less than200mg·L-1in the ethanol-based reaction system. The addition of ammonium had little effect on sulfur-oxidizing autotrophic and mixotrophic denitrification process, indicating that sulfur-oxidizing autotrophic and mixotrophic denitrifying bacteria could utilize nitrate as the sole nitrogen source for growth, when the ratio of S0:CH3COO-was3:1, the sulfate production could be controlled to the great extent.Real-time quantitative PCR and454pyrosequencing technique show in the SAMD-MBR denitrification system microbial community structure exhibited a high-degree stability at class and genus levels. Community characteristics of the reaction system at class level:Betaproteobacteria was the biggest dominant population, and the average content was varied in the range of31.62%-73.01%. In methanol-based mixotrophic denitrifying system Betaproteobacteria was the biggest dominant population and the content was maintained at60to85%in the stable operation stage. Microbial community structure at genus level:in methanol-based SAME) system, Thiobacillus and Sulfurimonas were the biggest dominant species. In ethanol-based SAMD system, microbial community was more abundant but varied larger. Thauera vadinHA17_norank, Sulfurimonas (Thiophilic sp) were the dominant species, accounting for more than60%of the microbial community.