Biosolids Frequently Asked Questions

Frequently Asked Questions
Biosolids application trail


Biosolids Application

Health and the Environment


What are biosolids?

Biosolids are the solids that result from municipal wastewater treatment and meet strict requirements outlined in the Organic Matter Recycling Regulation. Because of their stabilized, nutrient-rich, and humus like properties, biosolids provide a sustainable alternative to chemical fertilizers as a means to improve soil fertility where nutrients are limited.

How much biosolids are produced in the RDN each year?

Roughly 4,300 bulk tonnes of biosolids are produced in the RDN every year.

How are biosolids produced?

During the treatment process, sludge (organic and inorganic materials that settle in a primary clarifier or secondary clarifier) is sent to digesters for solids processing. During this process, micro-organisms use the organic material present in the solids as a food source and convert it to by-products such as methane gas and water. Digestion results in a 90% reduction of pathogens and the production of a wet soil-like material called "biosolids" that contain 95-97% water. Mechanical equipment is used to remove water from the biosolids, producing the final product.

What is in biosolids?

Biosolids are comprised mostly of water, sand, nutrients and organic matter (also called humus). Humus helps soil to retain water and nutrients so they are available for plant growth. Biosolids also contains nitrogen, phosphorus and other nutrients that plants need for growth, as well as trace elements and microorganisms.

Why are biosolids such a good fertilizer?

Biosolids are excellent fertilizers because they:
  • Contain humus, which helps soil to retain water and nutrients.
  • Contain significant amounts of nitrogen, phosphorus and potassium, as well as many trace elements essential for healthy tree growth.
  • Release nutrients over a long period of time, so that trees have a sustained source of nourishment.

What are the goals of the Forest Fertilization Program?

The Forest Fertilization Program goals are:
  • To enhance tree growth rates and biomass
  • To increase natural tree seeding through improved soil quality and increased water holding capacity
  • To improve long-term forest productivity by increasing the nutrient and organic matter concentrations within the thin underdeveloped humus layer overlying the mineral soil in both lowland and upland forests
  • To demonstrate best management practices in the beneficial re-use of biosolids
  • To further the knowledge and research on modern forestry practises on Vancouver Island
  • To divert biosolids from the Regional Landfill
  • To locally manage biosolids in a way that mirrors the nutrient cycling processes occurring in nature
  • To promote and participate in the sustainable environmental management of our Region's resources as well as wastes.

Where are RDN biosolids being applied?

Biosolids are applied to approximately 260 ha of land that is approximately 12 km northwest of Nanaimo and about 1.1 km west of the Biggs/Doumont Road intersection (just off Weigles Road).

How are biosolids stored and applied?

Biosolids are trucked to a storage site located near the end of Weigles Road. Once a sufficient quantity is stored, the biosolids are loaded into a special applicator vehicle. The applicator vehicle has a large box which then feeds a high-speed side throw discharge unit called the 'aerospreader'. The biosolids will then be carefully applied over the forest site in pre-measured amounts.

The biosolids stockpile locations at the woodlot are paved and signs identify them and provide contact information for follow-up.
Photo credit: SYLVIS Environmental

What do the fertilized sites look like?

Fertilized sites appear to be covered by a rich, dark topsoil material to a depth of two centimeters.

How do biosolids improve tree health?

The biosolids Forest Fertilization Project has demonstrated remarkable increases in tree growth from 50% to 400%. Biosolids helps trees in nutrient poor areas to achieve their maximum natural potential as though they were growing in ideal conditions. Trees treated with biosolids also appear healthier; needles and buds are longer, greener and more numerous.

Where else has this type of project been done?

Treated biosolids have been widely used in Canada, the United States and Europe for over 40 years. The most common use is as an agricultural fertilizer. Kelowna has used its biosolids to fertilize orchard trees since 1995. Seattle, Washington has 20 years of experience with applying biosolids to forest land. The Greater Vancouver Regional District completed a three-year research project with the University of British Columbia to demonstrate the potential for recycling treated biosolids as a forest fertilizer.

Are there any public health risks from biosolids?

There is a slight chance that someone could get sick if they actually ate biosolids. Otherwise, the risk from human contact with biosolids is negligible. Treatment through the mechanical digestion process kills most of the microorganisms in biosolids; the rest die off naturally once they are exposed to sunlight, lack of moisture and low pH levels in the soil.

The proportion of trace elements in biosolids requiring careful monitoring is very small (less than 1/10 of 1 percent). These include such things as copper, lead, mercury and zinc. These elements enter the sewer system from residences and storm water runoff. Most of these minerals actually benefit plant growth, but they can be harmful in excess concentrations. That is why the composition of biosolids used in land applications is carefully analyzed and controlled. Only biosolids which meet the Ministry of Environment's Organic Matter Recycling Regulation are used in land application projects.

Will there be effects on my well water?

Studies performed in 2003 and repeated in 2013 confirmed that past and proposed future applications of biosolids within the Application Area will not impact groundwater quality in any of the wells located in the region.

Research performed by Vancouver Island University has shown that trace elements introduced into the soil through biosolids projects generally do not move far below the soil surface, usually within 5 to 10 centimetres. Even during a very severe rainstorm, biosolids that have not yet been absorbed into the soil will move only a few metres. This would not affect the nearest residence to our project site, 1 km away. Nevertheless, to assure the safety of water supplies, application sites are away from steep slopes and 30 to 60 metres from any watercourse.

Will access to the forest be restricted during or after the biosolids application?

Public access to the forest is limited during the field operations, which are scheduled for short periods throughout the year. Afterward, the public may use the forest. However, we post signs advising people that biosolids have been applied to the sites and asking people not to use sites where biosolids has been applied. We keep these signs up for three years to ensure proper notification. These sites will comprise 50 hectares each year out of the forest's total 1,703 hectares.

What other controls will protect public health and the environment?

Biosolids application is done according to a Land Application Plan written by SYLVIS. The Land Application Plan must meet all requirements set out in the Organic Matter Recycling Regulation and is subject to audit by the Ministry of Environment staff.

To protect public health and the environment, we:

  • Regularly test our biosolids to ensure they meet Ministry criteria for land application
  • Restrict public access to the application areas
  • Establish buffer zones from potable water sources, water bodies, roads and highways
  • Post signs on roads and paths advising the public that biosolids are being applied
  • Groundwater monitoring.

Wastewater Services | 6300 Hammond Bay Road | Nanaimo, BC V9T 6N2 | E-mail: rcu@rdn.bc.ca
Telephone: 250-390-6560 (Nanaimo) 250-954-3792 (Oceanside) 1-877-607-4111 (Toll Free)
1-800-862-3429 (Emergency) | 250-390-1542 (Fax)