超声处理对剩余污泥的粒径和溶出物的影响

Effect of ultrasonic treatment on the particle size and dissolved substances of excess sludge

为了有效地发挥微型动物摄食对剩余污泥的减量作用,研究了超声声能密度和超声时间对剩余污泥的粒径和溶出物(蛋白质、多糖、DNA、COD及BOD)溶出的影响.在脉冲比2∶1和超声时间10min的条件下,声能密度为0.2W.mL-1时出现一个污泥粒径变化的转折点,当小于转折点时污泥粒径随声能密度增加明显下降,而当大于转折点时污泥粒径几乎不受声能密度影响.在脉冲比2∶1和声能密度0.8W.mL-1的条件下,超声时间5min是个转折点.上清液中溶出物的浓度随超声波声能密度或超声时间的增加而增加,各溶出物指标之间存在显著的相关关系.溶出物指标中蛋白质指标可以较好地反映出污泥破解状态.为了得到既能使污泥粒径变小到微型动物可摄食的程度又能使污泥中溶出物的溶出量最少的效果,建议声能密度或超声时间取上述转折点为限值.个数平均粒径(Dn)和重量平均粒径(Dw)分别反映了污泥的几何粒径变化和溶出物的溶出状况,因此,在超声破解污泥-微型动物摄食污泥的污泥减量工艺中可通过Dn和Dw的并用来决定剩余污泥超声处理的工艺参数.

Microfauna can effectively consume particulate matter and minimize the sludge mass when the particle size is appropriate. This research investigated effects of ultrasonic density and treatment time on the particle size and concentrations of dissolved substances including protein, polysaccharide, DNA, COD and BOD of excess sludge. Under conditions of 2：1 pulse ratio and 10-minute treatment time, a turning point of the particle size of sludge existed at 0.2 W· mL^ - 1. If below this point, the particle size of excess sludge decreased significantly with the increase of ultrasonic density. And, if beyond this point, the particle size was hardly affected by the ultrasonic density. Under conditions of the same pulse ratio and 0.8 W·mL^-1, a turning point existed at the treatment time of 5 minutes. Concentration of all dissolved substances in the supernatant increased with the ultrasonic density or treatment time. There were significant correlations between the concentrations of dissolved substances, and the protein concentration was used as an index to indicate the state of sludge disintegration. In order to meet the targets of both disintegrating excess sludge to the size appropriate for microfauna and minimizing the extraction of other substances in the sludge, ultrasonic density and treatment time should be controlled below the above turning points. Since number-mean diameter and weight-mean diameter of sludge particles reflect the change of geometrical diameter and the dissolution of sludge, they can be used to determine the appropriate ultrasonic density and treatment time in the ultrasonic treatment process of excess sludge for to excess sludge reduction by predatory activity of microfauna.