剪切应力对活性污泥絮体特征的影响

Influence of shear stress on characteristics of activated sludge flocs

采用具有自动控制系统可周期性改变搅拌速度的生物反应器处理生活污水,研究了剪切应力周期变化对活性污泥絮体特征及功能菌群分布的影响。结果表明,在相同的运行条件下,运行初期的污泥形态不规则,结构疏松,其内部各功能菌群丰度差异较大,污泥絮体粒径受剪切应力影响较大,最大和最小剪切应力下污泥平均粒径相差30μm;随着反应器运行时间的延长,活性污泥絮体的粒径减小;到达运行稳定期,污泥粒径较小,但结构紧实,最大和最小剪切应力下污泥平均粒径相差仅为6μm,说明剪切应力对污泥粒径的影响减弱,其主要作用在于维持污泥絮体相对稳定的三维结构及相对平衡的功能菌群分布。此外,处理效果研究也表明,稳定的污泥结构有助于污染物去除效率的提高。

The characteristics of activated sludge and distribution of functional flora were studied in differ-ent shear stress and periods in the bioreactor of sewage treatment with automatic control system to change the stir-ring speed periodically. The results showed that, under the same operational conditions, the characteristics of ini-tial activated sludge were irregular form, loose structure and widely different abundance of functional flora. The in-fluence of shear stress on the sludge size was violent, and gap of mean size was 30 μm between maximum and mini-mum shear stress. Along with the bioreactor operation, the mean size of activated sludge decreased. In stable peri-od, the size of sludge floes was smaller, but its structure was tight. The gap of mean size was only 6 μm between maximum and minimum shear stress. Results showed that the shear stress played an important role in maintaining stable 3-D structure and relative mean distribution of functional flora in stable phase. Research of treatment effect also showed that stable characteristic of activated sludge floc helped to removal efficiency of pollutants.