What are biosolids?
Biosolids are a product of sewage treatment that can be used as a natural fertilizer as well as a conditioner to recover contaminated or unusable soil.
As sewage moves through Ottawa’s wastewater treatment facility, solids are extracted from liquids for further treatment. These solids are then dewatered to produce a dry, dark, nutrient-rich material called biosolid cake that closely resembles damp organic soil.
Ottawa biosolids are rich in essential nutrients for plant growth, such as phosphorous. Ottawa-area soils are naturally deficient in phosphorous and the application of biosolids helps return this essential nutrient to the soil.
Who benefits from the use of biosolids?
Farmers:
- The City of Ottawa supplies, delivers and applies biosolids free of charge to eligible farms. This is a significant cost savings for farmers who would otherwise need to purchase commercial fertilizers.
- If you are a farmer interested in participating in the City of Ottawa's Biosolids Beneficial Use Program, please contact 613-580-2424, ext. 23257, or send an email to biosolids-biosolides@ottawa.ca.
Residents:
- The reuse of biosolids keeps close to 50,000 metric tonnes of biosolids out of landfills every year. This extends the life of the City landfill and is more cost-effective than other disposal methods such as incineration.
How are biosolids typically used?
As a fertilizer:
- Ottawa biosolids are an excellent soil amendment providing a significant source of nutrients essential for plant growth such as phosphorus, nitrogen, calcium and other micro-elements. Using biosolids as a soil amendment on farm land is an effective and efficient way to increase the productivity of local soils.
For land reclamation:
- Biosolids can be applied to remediation sites where the material improves soil structure, provides organics and nutrients needed for plant re-growth and helps with water retention.
Do biosolids contain metals?
Yes. However, the levels are closely monitored and are well below provincial regulation limits. Also, under the Nutrient Management Act, the City is required to monitor and report to the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). Some metals such as copper are considered essential trace elements for plant growth.
The City of Ottawa operates a variety of programs to minimize contaminants entering the wastewater stream, including:
Is land application of biosolids a common practice?
Land application of biosolids is a common and acceptable practice for many North American municipalities. Ottawa has had a biosolid land application program since 1992.
What kinds of crops are fertilized with biosolids?
Ottawa’s biosolids are typically used to fertilize crops that are used for fuel or undergo further processing prior to animal consumption, such as:
- field corn
- cereal crops (e.g. wheat)
- legumes (e.g. alfalfa and soybeans)
How often can biosolids be applied to farmland and how much?
The frequency of land applications varies from site to site. Several factors are considered when determining a suitable site for land application. Some of the factors include: proximity to residential areas, slope of the land, soil chemistry, drainage, crops to be grown, and nearby watercourses. Ontario Regulation 267/03 restricts the volume of biosolids that can be applied to a field to protect both surface water and ground water in Ontario.
Do biosolids have an odour?
Yes, and the City employs the following best management practices to minimize odour during land application:
- Biosolids must be incorporated into the soil within 2 hours of their application
- Stockpiling of biosolids in fields is not permitted
- Local residents within 450m of the spreading location are notified a few weeks before the biosolids are applied
- Biosolids are not spread on weekends or statutory holidays
What does the City do to assess my water quality?
As per the City of Ottawa’s best management practices, the City offers free well water testing upon request to households adjacent to biosolid application sites. Tests will be taken up to four weeks before biosolids are applied, and between 10 and 12 weeks after application. All well test results are provided to the well owner.
Interested residents may book free well testing by calling 1-877-360-3830 or 613-260-3830. Residents may also request testing through email at biosolids_biosolides@ottawa.ca.
Ottawa Public Health provides free well testing to all well owners.
Why does the City apply biosolids instead of putting them in a landfill?
Land application is currently the most sustainable and cost-effective reuse option for the City of Ottawa’s biosolids. In addition, land application takes best advantage of a fixed and limited resource – phosphorus – which is essential for plant growth. Land application of biosolids redirects 50,000 metric tonnes towards beneficial reuse of material and puts valuable nutrients back into the soil.
