超声对污泥流变性及絮凝脱水性的影响

采用旋转粘度法研究了活性污泥体系的流变特性,考察和比较了超声处理前后污泥粘度及过滤比阻的变化,并就超声处理污泥的絮凝脱水性能进行了相关测试和分析.结果表明,随剪切速率的增大,污泥表观粘度降低,流动性增大,表现出流体变稀;污泥的流变特性反映出其胶状网络结构具有相对稳定性,污泥对水的结合能力强,因此,其过滤比阻高、脱水性能差;在固定频率25 kHz条件下,低声能密度(0.10～0.15W·mL-1)、短时间(2～3 min)超声处理可有效降低污泥表观粘度及过滤比阻;在絮凝剂(PDMDAAC)投量为污泥干固体质量(TS的)0.5%时,超声处理污泥的过滤比阻与滤饼含水率可分别降低至最小值0.18×109s2·g-1和65.7%.实验结果表明,将超声与絮凝剂结合用于污泥调理是可行的.

Influence of ultrasound on the rheological characterization and the flocculating dewaterability of sludge

The rheological characterization of activated sludge originating from a bioreactor was studied by way of rotation tests. The impact of ultrasound on the rheology of sludge was examined. Furthermore, the comparison and analysis of the filtration performances of flocculated sludge with and without an ultrasonic pretreatment were conducted. The relationship between shear rate and shear stress of the samples revealed a pseudoplastic non-Newtonian flow mode. With an increase in the rotary velocity, the shear stress increased, and accordingly the apparent viscosity decreased clearly. This rheological model reflected the network of a sludge possessing stability under low shear rate, which caused some difficulty in sludge dewatering due to interstitial bound water being contained in the network. Under the frequency of 25kHz , the decreasing sludge viscosity and the specific resistance observed at a lower ultrasound intensity (0.10 or 0.15 W·mL-1) and a short duration (2 or 3 minutes) was attributed to changes of the interface and structure of sludge. After being treated for 2 minutes at ultrasound intensity of 0.1W·mL-1, the minimum of the specific resistance and the water content of the filter cake ((i.e. 0.18×109s2·g-1, 65.7% respectively) was obtained by adding polymer of 0.5%TS, less than the minimum of flocculated sludge without being pretreated and accordingly the dose of flocculent was also reduced. In addition, some possible mechanisms concerning the promotion of sludge flocculating dewater performance with ultrasound were analyzed.