剩余污泥自絮凝特性及关键影响因素作用分析

为解决污泥减量化处理过程中药耗或能耗过高、污泥量增加等问题,提出利用污泥自身胞外聚合物(EPS)产生的自絮凝调理来促进其脱水性能,通过正交实验和单因素实验考察污泥质量浓度、搅拌强度和搅拌时间对污泥自絮凝特性的影响,分析污泥毛细吸水时间(tCST)、污泥容积指数(SVI)、污泥粒径和Zeta电位的变化规律.结果表明,自絮凝可增大污泥粒径,提高污泥疏水性,减少絮体表面Zeta电位的影响,从而改善污泥脱水性能和沉降性能.在最佳参数(污泥质量浓度18 g·L-1、搅拌强度200 r/min、搅拌时间3.5 min)条件下,自絮凝后污泥体积平均粒径增加11.4%,Zeta电位升高19.0%,tCST降低17.1%,SVI降低8.1%,效果显著.所考察的因素对自絮凝作用的影响程度依次为:污泥质量浓度搅拌时间搅拌强度.较高的污泥质量浓度、搅拌强度和搅拌时间均有利于提高自絮凝效果,而当污泥质量浓度、搅拌强度或搅拌时间大于最佳参数时,自絮凝效果则逐渐减弱.研究成果提供了利用污泥自身特性进行调理的新思路,可为优化污泥调理方式、降低调理药耗和减少污泥产量提供技术支持.

Analysis of characteristics and key factors of excess sludge self-flocculation

To solve the existing problems, such as sludge volume increasing, high consumption of chemical reagent and energy during the sludge treatment and disposal, a sludge conditioning method, called self-flocculation, was proposed. This approach enhanced the dewatering efficiency of sludge via the utilization of the self-flocculation function of the extracellular polymeric substance (EPS). By orthogonal and single factor experiments, the impacts of sludge concentration, stirring intensity and stirring time on the sludge self-flocculation were investigated. Meanwhile, the corresponding variation of the capillary suction time (t_CST), sludge volume index (SVI), particle size and Zeta potential were also analyzed. Experimental results indicated that self-flocculation could enlarge the particle size of sludge and decrease the effect of flocs Zeta potential. Therefore, hydrophobicity, dewaterability and settleability of sludge were improved. Under the optimal self-flocculation conditions (sludge concentration, 18 g/L, stirring intensity, 200 r/min, stirring time, 3.5 min), the particle size and Zeta potential of the sludge increased 11.4% and 19%, respectively, while the t_CST and SVI could be respectively reduced by 17.1% and 8.1%. In addition, the significant effects of operational parameters on self-flocculation showed a decreased trend of sludge concentration > stirring intensity > stirring time. A higher sludge concentration, stirring intensity and stirring time was beneficial to the sludge self-flocculation. However, once each of the three parameters was higher than that at the optimal condition, sludge self-flocculation would weaken gradually. This study provided a new approach for sludge conditioning by using the sludge self-characteristics.