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Effluent discharge criteria



In Canada, discharge criteria for federal facilities are set by Environment Canada, and all other discharge criteria are set by the provinces and territories. Most permits are determined on a case by case basis, depending on the quality and type of receiving water and the amount of discharge. Environmental impact studies are required for all federally funded and regulated discharges, and may be required by provincial authorities depending on the volume of the discharge or the sensitivity of the receiving environment.

When discharging to the ocean, until recently preliminary treatment only has been required, and is still being practiced in many coastal areas. Many plants discharging to the ocean have primary treatment only, but this is changing. For example, previously discharges greater than 0.45 ML/d to open marine outfalls required only primary treatment in the province of British Columbia, but effective July 15, 1999, a new regulation mandates secondary treatment as a minimum.

When discharging to streams and lakes or embayed marine waters higher effluent standards apply. Typically a minimum effluent quality of 45 mg/L BOD5 and 60 mg/L TSS is required for most non-ocean discharges in Canada. Discharges to lakes and streams with low dilutions require a more stringent effluent quality. Health Regulations for small discharges to ground with poor soil conditions are often less than 10/10 (10 mg/L BOD5 and 10 mg/L TSS) with stringent fecal coliform criteria (i.e. less than 2.2 MPN/100 mL). Similar stringent criteria apply for effluent re-use and irrigation applications.

Storm overflows in municipal areas are generally not regulated, unless they are from an industrial site.

Nutrients and toxicity

Legislation can identify environmentally sensitive zones, which require more stringent effluent quality standards. This is often based on geological characteristics such as river valley or lake systems. The Okanagan Valley in British Columbia is an example of one such zone which has stringent effluent total phosphorus and total nitrogen requirements for all municipal discharges. Effluent toxicity is also a common parameter, usually expressed as a concentration in which no more than fifty percent of the fish die over a ninety-six hours test period (96hLC50). Often the toxicity is directly related to the effluent ammonia concentration, and effluent ammonia levels are becoming more common in permit criteria for this reason. Effluent toxicity can also be due to high BOD concentrations (eg. primary effluent) which causes oxygen depletion during the test sufficient to suffocate the fish, as the test protocol allows for only marginal aeration during the test.


If chlorine is used, permits may specify minimum dosage, retention time and chlorine residual requirements, as well as sampling, measurement, and dechlorination requirements. Some provinces have standards for management of chlorine and sulfur dioxide containers.

In Ontario, if sufficient time downstream of a discharge is provided, disinfection may not be required. Disinfection from lagoons is generally not required unless there are sensitive downstream conditions such as a potable water intake or shellfish beds. Seasonal relaxation of disinfection requirements may be allowed if the receiving water is not used for recreational, agricultural or consumptive purposes. Most large population centres disinfect year round, but some, as in Vancouver, British Columbia, disinfect only in summer when swimming is likely.

The provinces of British Columbia, Saskatchewan, Quebec and Prince Edward Island do not favour the use of chlorine for disinfection. In British Columbia, dechlorination is mandatory, in other provinces dechlorination requirements are determined on a case by case basis. There is a growing trend across North America to disinfect wastewater effluent using ultra-violet radiation, in place of chlorination.


Biosolids are regulated in all provinces in Canada. Agriculture and Agri-Food Canada (AAFC), the Canadian Council of the Ministers of the Environment (CCME) and the Standards Council of Canada (SCC) (through the Bureau du Normalization du Quebec (BNQ)) are involved in development of composting standards for biosolids. In 1995, the hoped for outcomes of collaboration of the above entities were:

  • a national Canadian standard for the composting industry (BNQ)
  • guidelines for compost (CCME)
  • the adoption of new mandatory criteria for compost (AAFC)

Voluntary standardization is coordinated by the SCC, that represents Canada within the International Standards Organization (ISO). BNQ is one of five standards writing organizations that is authorized by SCC. Among other things, BNQ has been given responsibility for soil amendments, organic fertilizers, fertilization, and treatment of municipal sewage.

CCME guidelines are being developed with four criteria for compost quality and safety: maturity, foreign matter, trace elements and pathogenic organisms. Composting is seen as an alternative for management of the organic portion of municipal waste, since Canada is aiming to divert 50 percent of the waste stream from landfills.

The Plant Products Division of AAFC administers the Fertilizers Act and Regulation, and controls compost sold as soil amendment or fertilizer. Soil amendment or fertilizer must be safe, efficacious and properly labelled, must not pose significant risk to humans, plants, animals or environment when used according to directions. Random sampling and analysis of products must meet established the criteria. The AAFC is currently (1995) working to include a direct reference to BNQ standard in the Fertilizers Regulation.

Limits are often set by provincial regulatory authorities for effluent parameters which may be of concern in specific discharges. These are mainly limits upon metal levels or toxic organic contaminants in industrial or other special waste discharges.

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