CASS工艺应用于小城镇污水处理厂的工艺设计及效果分析

Process Design and Effect Analysis of Domestic Sewage Treatment in Small Towns by Using CASS Process

小城镇污水具有水质不稳定,可生化性好,污水中悬浮物浓度、氮和磷的含量较高等特点.以四川省茂县城镇污水处理工艺设计为例,探讨CASS（Cyclic Activated Sludge System）工艺在小县城污水处理工程的适用性及处理效果.通过计算关键技术参数（污泥负荷：0.15 kg·BOD5·kg^-1·MLSS·d^-1）;排水比：1/4;反应周期：进水2h,曝气4h,沉淀0.8h,出水1.2h）以及时污水处理效果进行分析.结果表明：CODCr进水浓度：244～434 mg·L^-1,出水为21 ～40 mg·L^-1;BOD5进水浓度：150 ～250 mg·L^-1,出水12～20 mg·L^-1;NH4-N进水浓度：25～45mg·L^-1,出水2.0～6.0 mg·L^-1;TP进水浓度：2.0～5.4 mg·L^-1,出水0.2～1.0 mg·L^-1.CASS工艺处理污水的效果良好,出水水质达到《国家城镇污水处理厂污染物排放标准》（GB 18918-2002） 1B要求,CASS工艺适用于茂县城镇污水处理.研究结果可为偏远的经济落后地区的污水处理工艺选择和运行方面提供技术参考.

The sewage in small towns has the features of unstable water quality, good biodegradability and high concentration of SS, nitrogen and phosphorus. The CASS process was applied in the sewage treatment plant in Fengyi Town of Mao County according to the features of sewage and local economic condition. In this paper, the main treatment process of sewage treatment plant was introduced, and the key technical parameters were gained： sludge load 0.15 kg·BOD5·kg^-1·MLSS·d^-1, ratio of draining 1/4. Its reaction period contains influent 2h, aeration 4h, sedimentation 0.8h, and effluent 1.2h. Then, the wastewater treatment effect was analyzed, the results showed that the water quality of influent was ：CODcr ：244 - 434 mg ·L^-1, B OD5 ： 150 - 250 mg ·L^-1, NH4 -N：25 -45 mg·L^-1,TP： 2.0-5.4 mg ·L^-1, the quality of effluent was： CODcr： 21 -40 mg ·L^-1, BOD5 ： 12 - 20 mg ·L^-1, NH4 - N ： 2.0 - 6.0 mg ·L^-1, TP ： 0.2 - 1.0 mg·L^-1, in which the standard of the level B in class I were achieved according to Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant （ GB18918 - 2002） .