低溶解氧条件下活性污泥沉降性的研究

采用连续流A/O工艺处理实际生活污水,研究不同溶解氧(DO)浓度条件下的污泥沉降性,同时考察了系统除磷脱氮功能对于污泥沉降性能的影响.结果表明,随着DO从2 mg/L逐渐降低至1、0.5、0.4 mg/L的过程中,系统的硝化效果逐渐恶化,氨氮去除率从100%降低到15%左右,长期低DO条件运行导致系统基本丧失脱氮功能,逐渐转化为单纯去除有机物的系统.期间污泥容积指数(SVI)有小幅波动,维持在145 mL/g以下,污泥沉降性良好.将DO继续降至0.2～0.3 mg/L,在缺氧段和好氧段分别有了一定的放磷和吸磷效果,SVI从130 mL/g降低到99 mL/g.说明系统除磷功能的增强有利于改善污泥沉降性能.对比实验中,将DO从2 mg/L直接降低到0.5 mg/L,氨氮去除率下降到54%,脱氮良好,总氮去除率稳定在50%左右;SVI从110 mL/g上升至160 mL/g左右,显微镜检发现丝状菌增殖.分析认为,脱氮系统比单纯去除有机物的系统容易发生丝状菌污泥膨胀.

Study on the settling ability of activated sludge under low DO condition

Continuous flow A/O process is used for treating domestic sewage. The sludge settling ability under different DO concentrations has been studied. At the same time, the effects of system dephosphorization and denitrification on sludge settling ability have been investigated. getting worse, while the DO reduces gradually from 2 mg/L to 1, The results show that the system nitrification is 0.5, 0.4 mg/L. The removal rate of ammonianitrogen gets lower from 100% to about 15%. Running under low DO condition for a long time has caused the system to lose the nitrification function, and the system has gradually been turned into one that can only remove organisms. The sludge settling ability is getting better while the SVI is always lower than 145 mL/g. When the DO is lowered to 0.2-0.3 mg/L, the phosphate releave and absorption are getting better, in the anoxic and aerobic zones; SVI has been lowered from 130 mL/g to 99 mL/g. It indicates that the reinforced dephosphorization is good for improving the sludge settling ability. In contrast test, the DO is lowered directly from 2 mg/L to 0.5 mg/L, the removal rate of ammonia-nitrogen goes down to 54%, the denitrification is very good, and the total removal rate of nitrogen stays at about 50%. SVI goes up from 110 mL/g to 160 mL/g or so. Filamentous bacteria proliferation is found under microscope. Compared with COD removal system, filamentous sludge bulking is liable to occur in the denitrification system.