| environ. |
sewage treatment system Sewage treatment comes in two stages - primary and secondary treatment. The primary stage involves a process of screening solids from sewage, leaving a sludge and relatively clear water for further treatment or for disposal into rivers, the sea or on to the land. In the secondary stage the sludge is stirred constantly in vast tanks to get more oxygen into the mixture, allowing bacteria to break down the organic matter and leave a harmless residue that falls as a sediment to the bottom of the tank. After processing, the clear water on top of the tank is discharged into rivers and the sediment is used as landfill or discharged at sea (污水处理分为两步——初级和中级处理。初级处理包括从污水中去掉固体，留下做进一步处理或进入河流、海或土地中的泥浆以及相对干净的水。中级处理中，泥浆在很大的罐中搅拌以混入更多的氧气，使细菌分解有机物质并且留下无害的剩余物，这些剩余物沉积在罐的底部。处理之后，罐上部的干净的水被排放到河里，沉积物作为填埋物或排放到海里。); wastewater treatment system |
