Sewerage systems are either "separate" or "combined" . 排水系统有“分流制”和“合流制”。
A land drain is usually a pipe buried in farm land but it may also be an open channel . 农田的排水系统通常是埋在农田中的管子,但也可以是明渠。
It became necessary to provide drainage or sewer systems to carry such wastes away from the area . 提供排水系统或污水管道系统,把废物排出市区已成为必要。
On either side a checker of open ditches showed where the municipal constructors had designed a system of drainage . 马路两旁纵横交错的阴沟说明承包市政工程的商人曾计划在那里修建排水系统。
The disinfection of the combined sewer overflows 合流制排水系统溢流污水消毒处理