Sewage Biosolids - Managing Urban Nutrients Responsibly for Crop Production
Table of Contents
Sewage biosolids are created when municipal wastewater treatment facilities separate municipal wastewater (water from sewage systems, road drains, etc.) into liquid (clean water that can be discharged to a nearby stream or river) and the leftover solids. Solids go through an additional treatment process to reduce the presence of potentially harmful micro-organisms and potential causes of odour. The final treated materials are sewage biosolids. Sewage biosolids that do not exceed the regulatory limits for contaminants, pathogens and odour can be applied to farm land as a non-agricultural source material (NASM). See our NASM web page for more information about land applying NASM.
Biosolids contain nutrients and organic matter that are beneficial and important to plant growth, such as:
They may also contain trace amounts of other elements such as arsenic, lead and mercury. The land application of sewage biosolids as a NASM and the elements NASM contains is regulated under the Nutrient Management Act, 2002, (NMA) and the Nutrient Management Regulation.
Municipal wastewater treatment plants receive raw sewage from residential, industrial and commercial sources. Bylaws regarding municipal sewer use do much to control the quality of the raw sewage received at sewage treatment plants. However, treated biosolids may still contain some chemicals that are not beneficial to crops, but pose minimal risk to the environment when applied to land in accordance with the regulation.
The Nutrient Management Regulation ensures that any land applied biosolids are of benefit to crops, do not degrade the natural environment and don't pose any harm to human or animal health.
The regulation sets out criteria for:
The key to using sewage biosolids successfully is management, which is a combination of:
People who practice good management will get the most benefit from the applied biosolids while minimizing risks to the environment and to the health of people and animals.
When applied according to the regulation, sewage biosolids will:
Sewage biosolids have been used on agricultural land in Canada, the United States and Europe for more than 30 years. Applying sewage biosolids to farmland is an important means of recycling nutrients in the environment, and offers economic and environmental advantages to communities.
These crops are well-suited to using nitrogen supplied by biosolids. Nutrients such as nitrogen should be applied within crop recommendations.
Some sewage biosolids contain a lot of nitrogen. Take care to apply the correct amount of nitrogen to cereal crops, and make sure to follow crop recommendations.
Soybeans and hay crops containing more than one-half legumes do not require added nitrogen, but will use added nitrogen rather than fix nitrogen from the atmosphere. Biosolids that supply phosphorus and/or organic matter can be of benefit to these crops. Some materials may cause management concerns. For example, viable tomato seeds, if present in sewage biosolids, can pose a weed problem in a soybean crop.
Some biosolids may be applied in late fall. However, as is the case for other crops, nitrogen management is critical to avoid over or under application that may cause poor fruit quality, delayed hardening of trees or vines, or winter injury.
As with spreading manure, applying biosolids may produce odours. Odours can be reduced by timely incorporation into the soil. When planning biosolids application, it is important to follow the standards set out in the regulation and to use best management practices that help to maximize benefit by conserving nitrogen while minimizing odour. The Odour Guide establishes the category of the biosolids. OMAFRA has some discretion to assign a different odour category to the material. The procedures to do this are set out in the Odour Guide.
The regulation establishes minimum separation distances between areas where biosolids are applied and dwellings, residential areas, and commercial, community and institutional uses (such as office buildings, campgrounds and schools). These setback distances are based on the potential of the material to produce odours: the greater the odour detection threshold, the greater the required separation distance.
The regulation establishes minimum separation distances of biosolids begin spread from features such as wells, surface water, saturated soil conditions and bedrock. These separation distances are based on the risk of the material entering either surface water or ground water. Minimum separation distances are determined based on the specific analysis of the material, the soil type found in the field, the slope of the land and the application method used in the area near the watercourse. Separation distances are determined on a case-by-case basis as part of a NASM Plan.
A NASM Plan deals with the management of NASM, including storage and land application. See the information about NASM for Farmers web page for more information about NASM plans.
Nutrients can be harmful to soil and water resources if improperly applied. For example:
Over application of nutrients is also a waste of money.
As nutrient sources, sewage biosolids must only be applied in accordance with nutrient management planning principles - total available nutrients applied must not exceed what the crop can use.
The three commandments of nutrient management planning:
The success of a biosolids land application program depends on:
Municipalities as generators of biosolids are responsible for:
Biosolids haulers and applicators are responsible for:
Farmers are responsible for:
Farmers also have the right to request flexibility in the land application program, and to stop or refuse biosolids application at any time.
The Nutrient Management homepage links to information on nutrient management planning, regulation, and certification and training, and other web pages dealing with agricultural and non-agricultural source materials.
The Agronomy Guide for Field Crops, Publication 811, has the latest information on producing field crops, tillage options, soil management and other tools for crop production.
The Soil Fertility Handbook, Publication 611, explains the fundamentals of how nutrients behave with soil and crops.
OMAFRA developed a series of Best Management Practices books to help farmers make practical and affordable farming decisions while conserving soil and water resources. Here is a selection to help you with nutrient and soil management:
For more information:
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