水污染控制 课件.doc

Chapter 3 Wastewater Treatment 1 Terms Sanitary sewage, municipal sewage, preliminary, primary, secondary/biological treatment, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), treatment/removal efficiency, primary effluent, sewage effluent/emission standards. Screen, grit chamber, primary/secondary clarifiers or settling tanks/basins, detention time, outlet weir. Microbe/microorganism, bacteria, fungi (fungus), activated sludge process, aeration tank/clarifier/basin, supernatant, ruturn/excess sludge, food-to-microorganism (F/M) ratio, mixed liquor suspended solids (MLSS), sludge volume index (SVI), sludge bulking, process flow diagram. 2 Flow chart of a wastewater treatment system A flow chart showing the typical sequence of wastewater treatment processes is given in Figure 1, where screening, grit removal, and primary sedimentation are primary treatment processes. Secondary treatment usually involves biological processes and additional settling. Not all sewage treatment plants require tertiary (advanced) treatment of nitrogen and phosphorus. 废水处理的典型工艺流程图如图1所示。筛滤、砂砾的去除、自然沉淀属一级处理过程。二级处理通常包括生物处理和二次沉淀。 Figure 1 Schematic overview of a wastewater treatment system 不是所有废水处理厂都需要去除氮和磷的三级或者深度处理。 3 Primary treatment In a typical sequence of wastewater treatment processes, screening, grit removal, and primary sedimentation are primary treatment processes. Primary treatment processes include preliminary treatment and primary sedimentation. 3.1 Preliminary treatment systems Preliminary treatment systems typically include screens and grit chambers. The first treatment process for raw wastewater is coarse screening. It retains floating debris such as wood, rags, or other bulky objects, that could clog pipes or damage mechanical equipment in the rest of the plant. 废水的第一个处理过程是初格栅。它能去除悬浮碎片，比如木头，碎屑或者其它大体积的物质，这些物质能堵塞处理厂后续处理设备的管道，或者损坏其机械设备。 3.2 Primary sedimentation Although the grit will settle out at this reduced velocity,