Decentralized Wastewater Systems

Decentralized and Communal Wastewater Systems

Decentralized wastewater management systems are permanent sustainable systems that treat wastewater at or near the source where it is generated. They operate independently of centralized/municipal wastewater collection and treatment infrastructure.  Public or private decentralized systems use  a variety of approaches for collection, treatment, and dispersal/reuse of wastewater for individual dwellings, industrial or institutional/commercial facilities, clusters of homes or businesses, and small communities where it is not technically or economically feasible to extend centralized/municipal wastewater services.  They provide a range of treatment options from simple, passive treatment with soil dispersal (commonly known as septic or onsite sewage systems), to more complex and mechanized approaches such as advanced treatment units.  Treated effluent may be discharged either to surface water or subsurface by infiltration. Decentralized systems come in two varieties:

  • Onsite systems are standalone systems serving a single building, generally on the same property, where wastewater treatment and disposal is provided
  • Communal or shared systems, where some portion of the wastewater management system is connected to more than one lot.

Onsite systems in Ontario that are wholly contained on the lot with the buildings served and that discharge to the subsurface fall under the jurisdiction of the Ontario Building Code. Onsite systems that are designed to treat more than 10,000 L/d, or discharge to surface water, fall under the jurisdiction of the Ministry of the Environment, Conservation and Parks (MECP).

Communal systems can take on different configurations and designs but will generally consist of a collection system that connects different lots to one treatment facility. This is similar to a centralized/municipal system, but at a smaller scale and may use alternative collection system technologies such as low pressure sewers, vacuum sewers and septic tank effluent pump (STEP) sewers. Communal systems always fall under the jurisdiction of the MECP, regardless of capacity or method of effluent disposal.

Like any other system, decentralized systems must be properly designed, maintained, and operated to provide optimum benefits. The Ontario Onsite Wastewater Association (OOWA) represents members that design, engineer, manufacture, install and service systems that manage wastewater in a decentralized fashion.  OOWA is proud to represent members from both sides of the industry, onsite and communal.

For assistance with your project, consult an OOWA industry professional. You can locate one in your area by visiting our ‘Find A Professional’ page.