A sewer system that carries only sanitary sewage; no storm-water runoff. When a sewer is constructed this way, wastewater treatment plants can be sized to treat sanitary wastes only and all of the water entering the plant receives complete treatment at all times.
Source https://www.lenntech.com/water-glossary.htmариутгах татуургын тусгаар системийн коллектор
коллектор раздельный системы канализации