pH调节对活性污泥混合液膜过滤性的影响

探讨了用NaOH调节pH值对膜-生物反应器混合液膜过滤性能的影响,并通过分析污泥混合液性质的变化研究其作用机理.试验表明,适当调节pH到碱性,可以使膜过滤性能得到改善.投加碱液使污泥胞外多聚物(EPS)减少,污泥容积指数(SVI)降低,但上清液中总有机碳(TOC)浓度增加.混合液膜过滤性能的改善与污泥SVI的降低密切相关.在碱性条件下,从细胞表面脱落下来的EPS对絮体颗粒的絮凝性有一定促进作用,但效果有限.推测碱液处理使细胞表面的LB-EPS脱落,从而使细胞表面疏水性增加,有利于絮体颗粒之间的絮凝,从而有利于混合液膜过滤性的改善.

EFFECT OF ADJUSTING pH ON MEMBRANE FILTERABILITY OF ACTIVATED SLUDGE MIXED LIQUOR

The effect of adjusting pH by NaOH on membrane filterability of activated sludge mixed liquor was studied in this research. An analysis of the properties of the mixed liquor was conducted to investigate the mechanisms. The results indicated that moderately adjusting pH was effective to improve the membrane filterabilityof mixed liquor. Treated by NaOH,extracellular polymeric substances (EPS) on microbial cells was released,sludge volume index(SVI)was reduced while the supernatant TOC was increased. The improvement of membrane filterability was closely related to the decrease of SVI. EPS released from the surface of microbial cells at alkaline condition could enhance the flocculating ability of activated sludge flocs to some extent, but the effect was limited. It was presumed that treatment with NaOH could extracted LB-EPS from the surface of cells so as to increase the hydrophobic property of cells, which was favorable to flocculation among sludge flocs and hence the membrane filterability of mixed liquor.