Sewage classes [http://scipeople.ru/group/7124/discussions/]
污水类
 
Class IV: general industrial water area.
IV类：一般工业用水区。
 
V: agricultural water area, the general landscape requirements of water.
V类：农业用水区、一般景观要求水域。
 
 
Poor V class: useless dirty water, also known as super V class.
劣V类：无用脏水，也称超V类。