微气泡曝气中活性污泥混合液性质变化

采用SPG膜微气泡发生系统,考察微气泡曝气过程中,污泥混合液性质的变化及相关关系,包括污泥粒径、污泥EPS质量浓度、上清液浊度和有机碳质量浓度、混合液黏度和表面张力等.结果表明,在微气泡发生系统中液体循环泵的水力剪切作用造成污泥絮体破碎及污泥粒径减小.在该过程中,污泥EPS释放,上清液浊度和有机碳（特别是胶体有机碳）质量浓度升高,同时污泥絮体的再絮凝能力严重丧失.污泥EPS物质的释放导致混合液黏度增加,但混合液表面张力保持不变.相关性分析表明,污泥粒径减小及污泥EPS释放是造成混合液其他性质变化的主要原因.与离心型循环泵相比,蠕动泵水力剪切作用较弱,对混合液性质的影响较小.微气泡曝气中污泥混合液性质的变化会加速膜过滤过程的膜污染.

Variations of mixed liquor properties of activated sludge in microbubble aeration

Variations of mixed liquor properties of activated sludge were investigated and their correlations were analyzed in microbubble aeration using SPG membrane microbubble generation system, including sludge size, sludge EPS mass concentration, turbidity and organic carbon in the supernatant, viscosity and surface tension of mixed liquor. Results showed that the strong shear stress caused by liquid recycling pump in the microbubble generation system led to sludge broken and subsequent sludge floc size decreasing. During the process of sludge broken, sludge EPS released, which was considered to be responsible for increased turbidity and organic carbon (especially colloidal organic carbon) mass concentration in the supernatant. The re-flocculation ability of sludge flocs also reduced significantly due to sludge EPS release. In addition, the viscosity of mixed liquor increased along with sludge EPS release, but the surface tension remained constant. The sludge size decreasing and sludge EPS release were the main reasons for variations of other mixed liquor properties, according to correlation analysis. Compared to centrifugal type pump, peristaltic type pump impacted on mixed liquor properties less due to its weaker hydraulic shear stress. The membrane fouling in the membrane filtration process was accelerated due to variations of mixed liquor properties in microbubble aeration.