Biosolids FAQs
Questions:
Why recycle biosolids on agricultural land?
What nutrients do biosolids contain?
Is land application an established practice?
What about bacteria and viruses?
What about the ground and surface water?
What crops have been fertilized with biosolids?
How much can be spread on a site?
Answers:
A: Biosolids (treated sewage sludge) are a biologically stabilized, nutrient-rich, organic by-product of the wastewater treatment process. The biosolids produced at the City of Kingston's three wastewater treatment facilities have been stabilized to reduce odour and pathogens (bacteria and viruses) and are suitable for beneficial recycling.
Q: Why recycle biosolids on agricultural land?
A: Biosolids contain several nutrients required for crop growth. They also contain organic matter which can improve soil structure, reduce surface water runoff and soil erosion, and increase the soil's water holding capacity. Land application is an environmentally sustainable and cost effective way to enhance soil fertility and crop growth.
At Kingston's treatment plants, we produce close to 2470 dry tonnes of biosolids per year. The biosolids are applied to agricultural land, which is a cost effective means of recycling the nutrients and organic matter contained in biosolids.
Q: What nutrients do biosolids contain?
A: Biosolids have an appreciable concentration of nitrogen and phosphorus. They also contain several other nutrients or trace elements that crops require including magnesium, zinc, copper, boron, sulphur, iron and calcium.
Q: Is land application an established practice?
A: Yes. Biosolids have been applied to agricultural land in Canada and internationally for more than 40 years. Land application is used by more than 80% of Ontario municipalities.
A: Yes, extensive research has shown that responsible land application of biosolids is beneficial and poses minimal health or environmental risks. In order to protect the environment, human and animal health, and to ensure a balance of nutrients, the application of biosolids on agricultural land is regulated. In Ontario, guidelines for the safe use of biosolids on agricultural land are provided by the Ministry of Environment (MOE) and the Ministry of Agriculture and Food (OMAF). The guidelines define biosolids quality standards, receiving site characteristics and numerous application constraints such as crop suitability, soil permeability, soil quality standards, slope, depth to groundwater, biosolids application rate and timing and separation distances from waterways, wells and residences.
Several approvals are required prior to land application:
- Biosolids quality - testing by the generator to ensure the biosolids do not contain harmful constituents and to determine appropriate application rates.
- Soil Conditioning Site Approval - each application site must be certified by the MOE (through issuing a Certificate of Approval) and meet all the guideline conditions prior to land application.
- Contractor Systems Certificate - provided by the MOE indicating that the contractor satisfies defined requirements and operates in a safe manner.
The MOE enforces the guidelines to ensure that practices comply with the requirements of the Certificate of Approval.
A: Ontario's guidelines do not permit the application of biosolids with metal concentrations over specific limits. These are conservatively set to prevent toxicity or health impacts in plants, animals and humans. Biosolids are regularly tested for metals prior to land application to ensure that they do not exceed the established safe levels. The concentrations of regulated metals in Kingston's biosolids are well below Ontario's guideline levels.
Q: What about bacteria and viruses?
A: There have been no scientifically substantiated reports of illnesses caused by land application of stabilized biosolids in Canada. Kingston's biosolids have gone through a treatment process which stabilizes them and destroys disease-causing organisms. A mandatory waiting period between biosolids spreading and harvesting or pasturing acts as a safety precaution.
Q: What about the ground and surface water?
A: Guidelines in Ontario control how and where biosolids can be spread to ensure that ground and surface water is not contaminated. Biosolids are applied at a rate that allows the crops to use most of the nutrients as they become available. This keeps the nutrients from ending up in ground or surface waters. Metals in biosolids are generally in a form that is hard to dissolve in water and tend not to move out of the area to which they were applied.
Q: Do biosolids have an odour?
A: Yes, some people find the odour offensive while others do not. The intensity and duration of the odour is affected by factors such as the humidity, temperature and wind. The odour may be reduced by burying or injecting the biosolids in the soil as soon as they are applied. Kingston demands that contractors operate their facilities so that odours in the community will be minimized.
Q: What crops have been fertilized with biosolids?
A: Biosolids have been used to fertilize many crops locally including feed corn, wheat, soybeans, hay and pasture. Biosolids are not applied to home lawns or gardens, land used for tobacco production, or land with potential for public exposure.
Q: How much can be spread on a site?
A: Based on provincial guidelines, the maximum application rate of Kingston's biosolids is eight dry tonnes per hectare per five year period. The legislated application rate cannot exceed 135 kg of ammonium plus nitrate/nitrogen per hectare over a five year period.
Q: Can I get more information?
A: For more information about this project or to comment on the Biosolids Management Plan project, contact the project consultants or Utilities Kingston using any of the methods listed below:
Consultant Contact:
Mr. Guy Laporte, P. Eng.,
Deputy Project Manager
Totten Sims Hubicki Associates Ltd.
654 Norris Court
Kingston, ON K9P 2R9
Tel: 613-389-3703
Fax: 613-389-6729
Utilities Kingston Contact:
Ms. Erika Sorensen
Utilities Kingston
1211 John Counter Blvd., PO Box 790
Kingston, ON K7L 4X7
Tel: 613-546-1181, ext 2465
Fax: 613-542-1463
