A water sewage system is a collection process which transports sewage to waste water treatment plants 3. The waste water from households can be separated into Greywater, and Blackwater. read more
The term "sewage treatment plant" (or "sewage treatment works" in some countries) is nowadays often replaced with the term "wastewater treatment plant". Sewage can be treated close to where the sewage is created, which may be called a "decentralized" system or even an "on-site" system (in septic tanks, biofilters or aerobic treatment systems). read more