Biosolids Management
Nutrient Management Act
What governs the standards for Biosolids Land Application?
The Nutrient Management Act provided by the Ministry of Environment (MOE) and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). The Ministry of Agriculture, Food and Rural Affairs and the Ministry of the Environment are jointly responsible for implementing the act. The agriculture ministry works closely with farmers to approve nutrient management strategies and to provide training and education. The Ministry of the Environment oversees the compliance and enforcement requirements of the Nutrient Management Act.
Nutrient Management Act
The Nutrient Management Act passed on June 27, 2002. The Act provides a comprehensive nutrient management framework for Ontario's agricultural industry, municipalities and other generators of materials containing nutrients, including clear environmental protection guidelines. It builds on the existing system by giving current best management practices the force of law, and creating comprehensive, enforceable, province-wide standards to regulate the management of all land- applied materials containing nutrients.
Sewage Sludge Processing
Only stabilized biosolids treated by digestion or other means of stabilization are acceptable for use on agricultural land in Ontario. The biosolids produced at Toronto's Ashbridges Bay Treatment Plant (ABTP) are stabilized by anaerobic digestion for about two weeks in an environment heated to 37°C.
Spreading Requirements:
- Nitrogen - Biosolids contain plant available nitrogen such as ammonium and nitrate. Application rates to land are based on nitrogen fertilizer recommendations for the crop. Maximum application rates are determined based on concentrations of soil samples and the arithmetic average concentration of the material being applied.
- Metals - Arsenic, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, nickel, selenium and zinc are present in biosolids in varying concentrations. Because high levels of these metals can be toxic to plants, animals that eat those plants, and humans, only biosolids with low metal concentrations can be used on agricultural land. See maximum permissible metal concentrations in Ontario.
- Spreading - All biosolids spreading sites must be certified by the MOE. To protect the environment, the guidelines define spreading restrictions related to residences, watercourses, wells and soil depth (see the table below for separation distances).
- Timing - Following spreading of biosolids, waiting periods are required before grazing or harvesting to prevent possible transmission of disease. Waiting periods vary between three weeks to 15 months depending on the crops planted.
- Soil Restrictions - Biosolids may be applied to mineral soils but not to organic soils. They may not be applied to soils with high concentrations of metals or phosphorus in the top soil layer, or to soils with pH below 6.0.
*For more details see the Nutrient Management Act, O. Reg 267/03.
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