市政污泥与造纸污泥的脱水性能差异及其调质机理

Dewatering Performance and Conditioning Mechanism of Municipal Sludge and Paper Mill Sludge: A Comparison

为比较不同来源、性质的污泥脱水性能差异和调质机理,以CST为脱水性能评价指标,选用不同类型的PAM对两种污泥分别调质,进一步考察了调质过程中CST、上清液浊度、中位粒径及表面形貌的变化趋势,系统研究不同污泥脱水性能差异的原因。结果表明:与市政污泥相比,造纸污泥沉降性能和脱水性能更好,这主要归因于其较大的污泥絮体粒径和较低的Zeta电势;相对分子质量为1000万-1200万的CPAM对两种污泥均具有较好的调质效果;造纸污泥调质初期污泥上清液浊度迅速下降,当CPAM用量为0.5mg/g DS时,浊度即比原污泥下降75.0%;调质过程中造纸污泥絮体粒径增长速度明显更快;结合SEM分析发现未调质污泥以片状结构排列,以最佳CPAM投加量调质后的污泥呈多孔三维结构,此时絮体强度较高,过调质后污泥絮体结构则发生一定的坍塌。造纸污泥由于有不溶性纤维长链作为骨架材料,调质后三维结构更明显。

In order to compare the dewatering performance and conditioning mechanism of different sludge, the basic properties of municipal sludge and paper mill sludge, including zeta potential, EPS content and SVI were studied. Further research was focused on the flocculation mechanism of above two kinds of sludge conditioning, respectively, with CST as evaluation indexes of dehydration system, also supernatant turbidity ,floc size and surface morphology were investigated. It was indicated that the paper mill sludge exhibited better sedimentation and dehydration performances than municipal sludge did, which is mainly attributed to its larger floc size and less negative charge. CPAM with relative molecular mass of 10-12 million had a good quality effect on both kinds of sludge. When the amount of CPAM was 0.5mg/g DS, the turbidity of paper mill sludge was increased by 75.0% in comparison with that of the original sludge. The floc size of paper mill sludge grew faster than the other during the conditioning process. SEM was applied to gain further insights into surface morphology of sludge conditioning influence. According to the SEM image, the raw sludge without conditioning was arranged in lamellar structure, and the sludge after conditioning were arranged in porous and three-dimensional structure when treated by optimum dosage of CPAM, also the floc strength was better. However, excessive CPAM resulted in collapse of floe structure. Owing to the insoluble cellulose long chain as the skeleton material, the three-dimensional structure of paper mill sludge was more obvious.