微气泡及其产生方式对活性污泥混合液性质的影响

微气泡曝气有助于强化氧传质过程,在废水好氧生物处理中具有潜在的应用优势;同时,微气泡及其产生方式可能对污泥混合液性质产生影响.本研究采用SPG膜微气泡发生系统研究了微气泡及其产生方式对污泥混合液性质的影响.结果表明,微气泡曝气中,微气泡附着于污泥絮体导致污泥上浮聚集,从而造成反应器中污泥浓度(MLSS)下降,以及污泥沉降性能变差.微气泡产生过程中,液体循环泵(离心型)产生的强水力剪切力作用于污泥混合液,造成污泥絮体破碎、污泥粒径减小以及污泥絮体EPS释放,进而使得上清液浊度和有机碳(特别是胶体有机碳)浓度升高,污泥絮体的再絮凝能力丧失.微气泡产生过程中,污泥破碎导致的污泥有机物的释放使得污泥混合液的黏度增加,但混合液表面张力保持不变.

Influence of Microbubble and Its Generation Process on Mixed Liquor Properties of Activated Sludge

Microbubble aeration is supposed to be able to provide potential advantage for aerobic biological wastewater treatment due to enhancement of oxygen mass transfer. On the other hand, microbubble and its generation methods might affect mixed liquor properties of activated sludge. Then SPG membrane microbubble generation system was used to investigate mixed liquor properties of activated sludge in microbubble aeration. The results indicated that sludge floatation happened in microbubble aeration due to attachment of microbubbles to sludge flocs, resulting in a decrease in mixed liquor suspended solid (MLSS) concentration in the bioreactor and poor sludge settleability. The strong shear stress caused by liquid recycling pump (centrifugal type) during microbubble generation led to sludge broken. As a result, sludge floc size decreased significantly and sludge EPS released. The release of sludge EPS was considered to be responsible for increased turbidity and organic carbon (especially colloidal organic carbon) concentration in the supernatant. The re-flocculation ability of sludge flocs also almost lost due to sludge EPS release. In addition, the mixed liquor viscosity increased along with sludge broken and sludge EPS release, but the surface tension of mixed liquor remained constant.