Wastewater, often referred to as sewage, is "used" water. Water that has been used for washing, flushing, or manufacturing processes by homes, business and industries. It is approximately 99% water. The rest is made up of anything that is poured or flushed down drains, such as organic waste, detergents and chemicals.

In many municipalities or communities wastewater is collected through a network of underground pipes and delivered to a centrally operated treatment facility. The treated wastewater, or effluent, is then disinfected and discharged to a body of water.

Generally in rural areas, treatment for individual properties is a home sewage disposal system, often call a septic, or on-site system. These consist of a septic tank for settling and treatment, and a sub-surface disposal field.

Check out this video on an innovative approach to municipal management of on-site systems recently introduced in Richmond County, Nova Scotia.

With the conclusion of the Halifax Harbour Solutions Project (2009) about 50% of the population of Nova Scotia will be connected to central treatment facilities. About 45% of the population relies on on-site sewage disposal systems (septic tanks) and about 5% on raw discharge.