Abstract:

By gradually reducing the carbon to nitrogen (C/N) ratio, the phosphorus accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) were acclimated in a sequencing batch with anaerobic-limited oxygen operation mode. The simultaneous nitrification-denitrification and phosphorus removal(SNDPR) process of low C/N ratio domestic wastewater was accomplished. The competition between PAOs and GAOs, as well as the N₂O release at different C/N ratio, was studied. The results showed that the simultaneous nitrification and denitrification (SND) nitrogen removal and phosphorus removal efficiency of SNDPR were 83.5% and over 90% respectively at the C/N ratio of 7.0. The N₂O emission was 0.54 mg/L. The SND and phosphorus removal efficiency decreased to 60.1% and 80.5% respectively at C/N ratio of 3.0—3.5. Meanwhile, the N₂O emission reached 1.09 mg/L and the N₂O yield was 7.68%. The decrease of PHA accumulation, coupled with the increase of denitrification by GAOs, resulted in the higher N₂O emission at the lower C/N ratio of domestic wastewater. The variation of endogenous substance in different stage of SBR showed that PAOs-GAOs coexisted at each C/N ratio. GAOs tended to be enriched in SNDPR with the decreasing of C/N ratio. The extracellular polymer (EPS) increased from 43.4 mg/g VSS to 50.5mg/g VSS and the sludge volume index(SVI) increased from 99 ml/g to 127 ml/g with the decrease of C/N ratio. In loose EPS (LB-EPS), the ratio of protein (PN) to polysaccharide (PS) (PN/PS) decreases as C/N increases, and the hydrophilicity of sludge increases, which is not conducive to sludge dewatering.

Key words: carbon to nitrogen ratio, phosphorous accumulating organisms (PAOs), glycogen accumulating organisms (GAOs), simultaneous nitrification and denitrification phosphorous removal process(SNDPR), N₂O

摘要：

以厌氧-限氧方式运行序批式生物反应器（SBR），采用逐步降低进水碳氮比（C/N）方式驯化聚磷菌（PAOs）和聚糖菌（GAOs），启动了低C/N生活污水同步脱氮除磷过程（SNDPR），并考察了SNDPR内PAOs、GAOs间竞争关系及系统脱氮除磷性能过程N₂O释放特性。结果表明，C/N=7.0，SBR限氧段脱氮和除磷效率分别为83.5%和90%以上，N₂O产量为0.54 mg/L；C/N=3.0~3.5，脱氮和除磷效率分别降至60.1%和80.5%，N₂O产量达1.09 mg/L。SBR内不同反应阶段内源物质变化均表现出PAOs-GAOs共存特性。高C/N有利于微生物合成聚-β-羟基烷酸酯（PHA）并促进N₂O还原。C/N降低，SBR内污泥内源物质转化倾向于富集GAOs的降解特性。氨氧化菌（AOB）好氧反硝化过程及GAOs以PHA作为电子供体的内源反硝化过程促进了N₂O的释放。随C/N降低，SBR内污泥平均胞外聚合物（EPS）由43.4 mg/g VSS增至50.5 mg/g VSS，污泥容积指数（SVI）由99 ml/g增至127 ml/g。疏松型EPS（LB-EPS）内，蛋白质（PN）与多糖（PS）之比（PN/PS）随C/N增加而降低，污泥亲水性增加，不利于污泥脱水。

关键词: 碳氮比, 聚磷菌, 聚糖菌, 同步脱氮除磷, N₂O