Sewage Biosolids - Managing Urban Nutrients Responsibly for Crop Production

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Table of Contents

1. Sewage biosolids result from municipal wastewater treatment
2. Sewage biosolids contain nutrients
3. Crop production can be enhanced by biosolids
4. Applying biosolids to agricultural land benefits urban and rural communities alike
5. Municipal wastewater treatment
6. Typical sewage biosolids characteristics
7. Suitable crops for biosolids land application
8. Metal concentrations in sewage biosolids
9. Separation distances
10. Provincial standards and on-farm management ensure sewage biosolids are applied safely.
11. A farm-specific nutrient management plan balances crop requirements, land base, and available nutrients.
12. Other off-farm generated materials may also benefit crop production or soil quality.
13. Roles and responsibilities
14. For more information ...

Sewage biosolids result from municipal wastewater treatment

The treatment of municipal wastewater produces:

• clean effluent that is discharged to a nearby watercourse
• sewage biosolids, which are high-organic solid, semi-solid, or liquid materials that are retained for further treatment and processing.

Sewage biosolids are then stabilized by methods such as digestion or addition of lime to reduce the pathogen content and odour-producing potential. Once stabilized, biosolids can be applied to land in liquid form, or be dewatered and applied as a solid material.

Sewage biosolids contain nutrients

Biosolids contain nutrients and organic matter that are important to plant growth, such as:

• mineral and organic nitrogen, and phosphorus
• micronutrients such as zinc, magnesium, and copper.

They may also contain trace amounts of other elements such as arsenic,
lead, and mercury. Concentrations of these elements in land-applied sewage biosolids are regulated under the Nutrient Management Act, 2002, and the Environmental Protection Act.

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Crop production can be enhanced by biosolids

When applied according to best management practices, sewage biosolids will:

• improve soil fertility - offsetting the need for commercial fertilizers
• add organic matter - enhancing soil structure, moisture retention and permeability, while reducing the potential for wind and water erosion.
  

Applying biosolids to agricultural land benefits urban and rural communities alike

Sewage biosolids have been utilized 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. As such, the process offers economic and environmental advantages to society at large.

As with spreading manure, applying biosolids may produce odours. And as with manure, odours can be reduced by timely incorporation into the soil. When planning biosolids application, it's of utmost importance to use best management practices, which help to maximize benefit by conserving nitrogen, while minimizing odour.

The sewage biosolids land application program in Ontario is regulated. Land application is regulated under Regulation 347 of the Environmental Protection Act and Regulation 267/03 under the Nutrient Management Act, 2002. Environmental quality, food safety, and human health issues and concerns are addressed in both Regulations and supporting land application publications of the Ontario Ministry of Agriculture, Food and Rural Affairs and the Ontario Ministry of the Environment. In addition, each farm site receiving sewage biosolids must be approved by the Ministry of the Environment.

Municipal wastewater treatment

Text Equivalent of Diagram

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Typical sewage biosolids characteristics

Aerobic liquid sewage biosolids

Total Solids: 1.6% wet weight
Total Nitrogen: 5.1% dry weight
Fertilizer Equivalent Nitrogen: 0.25 kg/m³ (wet weight); 2.5 Lbs/1000 gal (wet weight)
Total Phosphorus: 2.7% dry weight
Phosphate Fertilizer Equivalent (as P₂O₅): 0.4 kg/m³ (wet weight); 4 Lbs/1000 gal (wet weight)

Anaerobic liquid sewage biosolids

Total Solids: 3.0% wet weight
Total Nitrogen: 6.5% dry weight
Fertilizer Equivalent Nitrogen: 1.07kg/m³ (wet weight.); 10.7 Lbs/1000 gal (weight weight)
Total Phosphorus: 3.6% dry weight
Phosphate Fertilizer Equivalent (as P₂O₅): 1.0 kg/m³ (wet weight); 10 Lbs/1000 gal (wet weight)

Anaerobic semi-solid (dewatered) sewage biosolids

Total Solids: 26% wet weight
Total Nitrogen: 4.0% dry weight
Fertilizer Equivalent Nitrogen: 3.98 kg/m³ (wet weight); 8.0 Lbs/ton (wet weight)
Total Phosphorus: 2.7% dry weight
Phosphate Fertilizer Equivalent (as P₂O₅): 6.45 kg/m³ (wet weight); 13 Lbs/ton (wet weight)

Notes:

• Fertilizer equivalent nitrogen is the sum of the inorganic nitrogen plus 30% of the organic nitrogen applied. It is assumed that no nitrogen is lost during application.
• Phosphate Fertilizer equivalent assumes 40% phosphorus availability in the year of application.
  

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Suitable crops for biosolids land application

Field corn, hay, haylage, pasture, and commercial sod

These crops are well-suited to using nitrogen supplied by biosolids. Nutrients such as nitrogen should be applied within crop recommendations.

Cereals

Nitrogen management is critical to avoid over application that may result in the crop lodging (falling down) before harvest.

Perennial legumes and soybeans

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

Tree Fruits and Grapes

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.

Notes:

• The maximum application rate per hectare for sewage biosolids must not exceed the maximum rate specified in the site Certificate of Approval or as determined by the Nutrient Management Plan, whichever is most restrictive.
• Nitrogen application rates for individual crops should not exceed recommended rates. Refer to Ontario Ministry of Agriculture, Food and Rural Affairs Publications 811 - Agronomy Guide for Field Crops, 360 - Fruit Production Recommendations, and 363 - Vegetable Production Recommendations, for recommended nutrient application rates.
• The Ontario Ministry of Agriculture, Food and Rural Affairs nutrient management computer program, NMAN, can be used for the determination of suitable application rates.

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Metal concentrations in sewage biosolids

Source: 2002 Survey of Municipal Sewage Biosolids Quality (Ontario Ministry of Agriculture, Food and Rural Affairs and the Ministry of the Environment)

Separation Distances

90/25* - Residence: 90m if surface applied or 25m if injected or incorporated within 6 hours.
450/50* - Residential Area: 450m if surface applied or 50m if injected or incorporated within 6 hours.

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Watercourses

Regulation 267/03 under the Nutrient Management Act, 2002, requires a minimum 20m separation distance between the top of the nearest bank of a surface watercourse and the area of application of municipal sewage biosolids. Greater separation distances may be required depending on the soil type, 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.

Provincial standards and on-farm management ensure sewage biosolids are applied safely.

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 aren't beneficial to crops, but pose minimal risk to the environment when applied to land in accordance with the Regulations.

The Regulations were developed to ensure that any biosolids being used are of benefit to crops, and are applied to land so as not to degrade the natural environment or pose harm to human or animal health.

The Regulations set out criteria for:

• concentrations of 11 elements of concern
• amount, method and timing of application
• separation distances from sensitive areas
• suitable soil types and topography.

The key to successful sewage biosolids utilization is management, which is a combination of:

• proper application methods
• best management practices
• nutrient management planning.

Wise management will get the most benefit from the applied biosolids, while protecting the environment and the health of people and animals.

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A farm-specific nutrient management plan balances crop requirements, land base, and available nutrients.

Improperly applied, nutrients can be deleterious to soil and water resources. For example:

• excessive nutrient applications can pollute surface and ground water
• nitrate nitrogen is very dynamic, and excessive soil nitrate at the end of the growing season can leach into ground water, posing a risk to human and animal health
• phosphorus binds to soil, and can move with eroded soil to rivers and lakes, degrading water quality and harming fish and wildlife habitat.

Over application of nutrients is also a waste of money.

As nutrient sources, sewage biosolids should only be applied in accordance with nutrient management planning principles - meaning that total available nutrients applied should not exceed what the crop can use.

1. Know what you have.
2. Know what you need.
3. Know how much you are applying.

Other off-farm generated materials may also benefit crop production or soil quality.

Some industrial processes produce organic and inorganic residuals that may benefit crop production, such as food processing by-products and paper mill biosolids.

As with sewage biosolids, application of these residuals to land must be in accordance with the Regulations. In addition, these residuals may be subject to a more rigorous review by the Biosolids Utilization Committee (BUC). For more information about BUC, or land application of materials other than sewage biosolids, contact the nearest office of the Ontario Ministry of the Environment or the Ontario Ministry of Agriculture, Food and Rural Affairs.

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Roles and responsibilities

The success of a biosolids land application program depends on:

• communication
• management
• all parties being aware of their responsibilities.
  

Municipality (as generator of the biosolids)

• must keep records of:
  • biosolids quality
  • location of all application sites
  • volumes applied to each site
• is also responsible for:
  • ensuring land-applied biosolids meet the criteria in the Regulations
  • providing alternative destinations if biosolids don't meet the criteria or can't be applied due
    to weather or field conditions
  • preparing a Nutrient Management Strategy
    

Hauler/Applicator

• is responsible for:
  • uniform land application that does not exceed the maximum application rate
  • timely application that is mutually beneficial for the hauler and the farmer
• must provide the farmer with a report indicating the fertilizer equivalent values of the land-applied biosolids
  • this is essential for the farmer to make sound nutrient management decisions
    

Farmer

• has the right to:
  • request flexibility in the land application program
  • stop or refuse biosolids application at any time
• is responsible for:
  • ensuring that biosolids are land-applied at times that are beneficial for crop production, but not disruptive to normal farming practices
  • ensuring that all waiting periods (as outlined in the Regulations) between biosolids application and harvesting or grazing are observed
  • utilizing best management practices in order to optimize the benefit and minimize the risk of sewage biosolids land application

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For more information…

• For more information or to obtain a ministry publication call the Ontario Ministry of Agriculture, Food and Rural Affairs, Agricultural Information Contact Centre at 1-888-466-2372 from within Ontario.
• Email your requests to products.omafra@ontario.ca or visit the OMAFRA website at www.omafra.gov.on.ca. Orders can be faxed to (519) 826-3633 or mailed to ServiceOntario, 1 Stone Road West, Guelph, Ontario, N1G 4Y2
• Call the OMAFRA nutrient management line at 1-866-242-4460 or email: nman.omafra@ontario.ca
• Contact the nearest ServiceOntario centre or office of the Ministry of the Environment

Additional OMAFRA Resources

• Land Application of Sewage Biosolids for Crop Production Factsheet, Order No. 00-023
• Agronomy Guide for Field Crops, Publication 811
• Soil Fertility Handbook, Publication 611
• Best Management Practices books
  • Nutrient Management BMP 05
  • Soil Management BMP 06
  • Water Management BMP 07
  • Nutrient Management Planning BMP 14

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