不同DO下SBBR亚硝酸型同步脱氮及N_2O释放特性

Characteristics of simultaneous nitrification and denitrification via nitrite and N_2O emission in SBBR under different DO concentrations

在(20±2.0)℃条件下,以实际生活污水为处理对象,以碳纤维为填料(填充率35%),利用序批式生物膜(sequencing batch biofilm reactor,SBBR)反应器,通过限氧曝气,成功实现了亚硝酸型同步生物脱氮(simultaneous nitrification and denitrification,SND)过程。荧光原位杂交技术(fluorescence in-situ hybridization,FISH)半定量表明,氨氧化菌(ammonia oxidizing bacteria, AOB)是硝化系统中的优势菌种。微生物将外碳源以聚β–羟基烷酸酯(poly-β-hydroxyalkanoate,PHA)的形式储存在体内,作为后续反硝化过程所需内碳源。DO=0.5 mg/L,SBBR系统NH_4^+-N和TN去除率分别为95%以上和80.4%,SND效率达77.9%。出水NO_x^--N小于10mg/L,且以NO_2^--N为主。DO=2.0、1.2和0.5 mg/L时,系统N_2O释放量分别为1.38、2.39和1.65 mg/L。AOB的好氧反硝化过程和低氧条件下以PHA作为内碳源的NO_x^--N反硝化过程,都会导致N_2O释放。低DO水平是实现亚硝酸型同步脱氮过程和降低N_2O释放的关键因素。低DO促进了AOB的竞争优势,形成了良好的缺氧微环境,降低了COD降解速率,为反硝化过程提供外碳源作为电子供体,从而降低了N_2O释放量。

At normal temperature of(20±2.0)℃,using actual domestic wastewater as influent substrate and carbon fibre as biological carriers(filling rate 35%),the simultaneous nitrification and denitrification via nitrite was achieved in a sequencing batch biofilm reactor under limited DO concentrations.The results of fluorescence in-situ hybridization(FISH)demonstrated that the ammonia oxidizing bacteria(AOB)became the dominant species in the nitrification process under limited DO concentration.During the anoxic and the initial aerobic process,the external COD was taken up and converted to polyhydroxyalkanoate(PHA),which can be used as internal carbon sources for the following denitrification.DO=0.5 mg/L,the NH4^+-N removal,TN removal and simultaneous nitrification and denitrification efficiency was more than 95%,80.4%and 77.9%,respectively.The concentration of NOx^--N in the effluent was less than 10 mg/L and mainly in the form of NO2--N.When the DO concentration was controlled at 2.0,1.2 and 0.5 mg/L,the N2O emission was 1.38,2.39 and 1.65 mg/L,respectively.Both the aerobic denitrification process of AOB and the denitrification of NOx^--N with PHA as carbon source at the presence of lower oxygen can lead to the release of N2O.The long time of lower DO conditions promoted AOB's competitive advantage,formed a micro-environment for denitrifiers,reduced the COD degradation rate,and provided an external carbon source as an electronic donor for denitrification,thereby reducing N2O emissions.