城市污水厂污泥化学调理深度脱水机理

Mechanism of chemical conditioning for sludge dewatering in a municipal wastewater treatment plant

城市污水厂剩余污泥脱水是当前实际生产中亟待解决的问题。考察了厦门市集美污水厂剩余污泥经FeCl3和CaO,投加量分别为污泥质量分数的0.5%～0.7%和1.0%～1.5%化学调理前后污泥粒度、形态及胞外聚合物(extracellular polymeric substances,EPS)的变化。结果表明,调理后污泥比阻降低86%,污泥颗粒之间细碎紧密,细菌表面变得粗糙,经板框压滤后含水率低于60%。由三维荧光光谱(three-dimensional emission and excitation matrixs,EEM)光谱分析可知,LB-EPS(loosely bound-EPS)同TB-EPS(Tightly bound-EPS)的荧光峰整体发生红移,出现位于IV区域的色氨酸类蛋白质荧光峰Ex/Em=313/380 nm。FeCl3和CaO的加入一方面破坏了污泥颗粒的细胞结构,使EPS大量溶出,细胞结合水变成表面吸附水;另一方面Fe3+和CaO水解,中和污泥负电荷,通过压缩双电层作用破坏污泥胶体颗粒的稳定,去除表面吸附水,大幅提高了污泥的脱水性能,利于进一步板框压滤脱水。

The excess sludge dewaterbility of municipal wastewater treatment plant （WWTP） is a key issue in practice. The excess sludge of Jimei WWTP was chemical conditioning by FeC13 and lime. The dosage was 0.5% -0.7% and 1.0% -I. 5% of sludge mass fraction for FeC13 and lime, respectively. The size distribu- tion, SEM and extracellular polymeric substances （EPS） changes of excess sludge were investigated before and after conditioning. After chemical conditioning, the specific resistance to filtration of sludge declined by 86%. The sludge particles crushed and bacterial surface became rough. The sludge cake moisture decreased below 60%. According to three-dimensional emission and excitation matrixs （EEM） results, the fluoresce peaks of LB -EPS （loosely bound-EPS） and TB-EPS （tightly bound-EPS） showed red movement and new peak Ex/Em = 313/380 nm was found. The floc structure was destroyed by FeC13 and lime, which made EPS released. The re- leased EPS enhanced the floc＇ s compressibility, forcing the internal water out of floe. Fe3 ~ and lime hydrolysis made the negative sludge charge neutralization, and the stability of sludge colloidal particles was destroyed by the effect of electric double layer compression. The surface attached water was removed, therefore, the dehydration property of excess sludge was enhanced obviously, which was favor for further sludge dewaterability by plate and frame filter press.