双频超声改善剩余污泥的脱水性能研究

摘要

为了探索双频超声预处理对剩余污泥脱水性能的影响,选择单独频率17、33 kHz和双频17+33 kHz,进行单位总固体(TS)不同超声能量水平(0～12 000 kJ·kg-1)下的序批式实验,通过测定污泥比阻和泥饼含水率来表征污泥可过滤性和离心脱水性能的变化.结果表明,在低能量水平下,双频超声对污泥脱水性能的改善效果远优于单频超声,17、33和17+33 kHz 3种频率下污泥比阻较原泥最大降低44.67％、57.30％和80.41％.在双频、超声能量1 000 kJ·kg-1条件下泥饼含水率较原泥最大降低20.62％.随着超声能量的增加,污泥平均粒径不断下降,污泥降解度不断增加,表明污泥胞外聚合物和细胞中的有机质不断从固相向液相转移.双频较单频的能量利用效率高,使得双频在更低的能量条件下达到更好的脱水效果,这为超声预处理技术在实际应用中的推广提供了科学支撑.%The use of ultrasound to pretreat waste activated sludge (WAS) is one of the cleanest means,but its practical application is restrained by its high energy consumption.Double frequency as a new parameter is expected to improve dehydration property of WAS and consequently reduce energy consumption.To explore effect of the use of double frequency ultrasound in pretreatment of WAS on its dehydration property,a sequencing batch experiment on use of ultrasound was designed to have three treatments in terms of frequency,i.e.17,33 kHz and 17+33 kHz,and carried out under the specific energy of 0-12 000 kJ · kg-1 per unit of total solids (TS).Changes in filterability and centrifugal dehydration property of WAS were monitored by measuring specific resistance of filtration (SRF) and moisture content of dehydrated WAS cake.Results show that double-frequency ultrasound was far too superior to single-frequency one in improving dehydration property of the WAS,when the ultrasounds were low in energy.When treated with ultrasound of 17,33 kHz,and 17+33 kHz,separately,SRF of WAS was reduced by 44.67％,57.30％,and 80.41％,respectively.The maximum effect of reducing moisture content in WAS cake by 20.62％ was observed in the treatment of double frequency,17+33 kHz and specific energy of 1 000 kJ · kg-1.With increasing specific energy,mean particle size of WAS declined steadily,but degradation degree of WAS increased steadily,which indicates that extracelluar polymers and organic matter in ceils of WAS were changing steadily from solid phase to liquid phase.The higher energy utilization efficiency of double frequency enables it to achieve better dehydration effect with lower energy supply than single frequency,which may serve as a scientific support to extrapolate the pretreatment technique of double frequency ultrasound in practical application.