Questions & Answers The following is a sampling of some commonly-asked questions about biosolids application projects; however, we cannot respond here to all possible questions. Please come to our Open House, Saturday, January 18, at the Pleasant Valley Community Hall, or call Paul Lucas, R.P.F., at 753-3245, local 2232, if you have questions that haven’t been covered here. What are biosolids and how are they produced? Biosolids are the organic solids that settle out when wastewater (sewage) is processed at a Greater Nanaimo wastewater treatment plant. Wastewater entering a treatment plant is first screened to remove large objects, then held in tanks where the suspended organic matter settles out by gravity to form biosolids at the bottom. The biosolids are removed and processed in large tanks called “digesters.” In the digesters, bacteria break down the biosolids, reducing its volume by half. Digestion also significantly reduces odours and disease-producing organisms. After they are dried, biosolids look much like garden soil and have a slight musty smell. 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 contain nitrogen, phosphorus and other nutrients that plants need for growth, as well as trace minerals and micro-organisms. Why does Vancouver Island University want to apply biosolids to sites in its Forest? The Vancouver Island University Forest is dedicated to demonstrating modern practices in forestry and ecology. We have forest sites where a lack of nutrients severely limits tree growth; and we have available to us an abundant supply of municipal biosolids, which can provide those nutrients. This project will provide a model for how we can improve the health of our forests in an ecologically sensible way and, at the same time, help the Regional District of Nanaimo divert biosolids from its landfill site. Why are biosolids such a good fertilizer? Biosolids are superior to commercial chemical fertilizers in many ways.
Recycling biosolids as a fertilizer turns two problems—biosolids disposal and poor forest soils—into an environmental solution. How will biosolids help in making trees healthier? Our 1992 biosolids forest fertilization project has demonstrated remarkable increases in tree growth— from 50% to 400%! But biosolids don’t produce mutant trees. Biosolids help 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. 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. Sewage treatment plant operators regularly work with and around biosolids, with no ill effects. Treatment through the mechanical digestion process kills 99.9% of the micro-organisms 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%. These include such things as copper, lead, mercury and zinc. These minerals enter the sewer system from residences and stormwater runoff. Most of these minerals actually benefit plant growth; however, they can be harmful in excess concentrations. That’s why the composition of biosolids used in land applications is carefully analyzed and controlled. Only biosolids that meet the Ministry of Water, Land and Air Protection’s Organic Matter Recycling Regulation (OMRR) is used in land application projects. Is the application site in Lantzville’s watershed or over Lantzville’s aquifer? Vancouver Island University Forest is located in the Flynfall Creek watershed, which is not part of Lantzville’s watershed. The most recent studies delineating Lantzville’s aquifer show that Vancouver Island University Forest is outside the boundaries of this aquifer. Monitoring data from our 1992 biosolids project shows that biosolids had no detectable impact on ground or surface waters. How will the biosolids be applied? Dried biosolids will be trucked to one of two composting sites located near the end of Weigles Road. After the composting process has been completed the biosolids will be 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 ‘aero-spreader.’ The composted biosolids will then be carefully applied over the forest site in pre-measured amounts. Why are the biosolids being composted? The Directors of the Regional District of Nanaimo instructed their staff to prepare an open tender process for the composting of biosolids to further reduce any harmful micro-organisms that may have survived the wastewater treatment process. Is there any danger of airborne bacteria or viruses being blown onto our property when biosolids are sprayed? Studies have shown that a person would have to be continually exposed for 2,500 hours, 100 metres downwind of a site to be harmed by airborne viruses from a biosolids spray application. Because the chance of this kind of exposure is essentially nil, researchers have determined that the viruses in sprayed biosolids do not pose a public health threat. Furthermore, the biosolids materials are too dense and cohesive to be blown 2 km to the nearest residential property. Will there be effects on well water for the residents on Dumont Road, or on the water in Brannen Lake? The monitoring results from the 1992 project showed that biosolids had:
Extensive research from our 1992 biosolids project has shown that trace minerals 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—2 km away. Nevertheless, we will assure the safety of water supplies in the following ways:
Will access to the Forest be restricted during or after the biosolids application? Public access to the Forest will be limited during the 2 to 3-week field operation, which is tentatively scheduled for September 2003. Afterwards, the public will be free to use the Forest; however, we will be posting signs asking people not to use the four small sites where biosolids have been applied. These sites comprise 20 hectares of the Forest’s total 1,303 hectares. We will also control and monitor all aspects of our project to ensure protection of public health and the environment. This includes posting signs advising people that biosolids have been applied to the sites. We keep these signs up for three years to assure that any potential affects have completely dissipated. What other controls will protect public health and the environment? This project will require a Land Application Plan to be written by a qualified, registered professional. The Land Application Plan must meet all requirements set out in the Organic Matter Recycling Regulation (OMRR) and is subject to audit by the Ministry of Water, Land and Air Protection staff. To protect public health and the environment, we have or will:
What does the Regional District of Nanaimo do with our biosolids now? At the moment, the RDN disposes of its biosolids in a landfill. Annually, Nanaimo produces approximately 500 to 600 dry tonnes of biosolids. This figure could increase dramatically due to new treatment processes and population growth. Nanaimo may not have an immediate problem with biosolids disposal, but it may well become a problem in a few years. We need to plan now for a new approach to biosolids disposal. Our project draws on the lessons learned in our 1992 biosolids project, and is an environmentally responsible alternative to the land filling of this recyclable resource. What is the Greater Vancouver Regional District’s involvement? Unlike the 1992 project, the GVRD is not participating in or providing any materials for this project. All biosolids for this project will come from the Greater Nanaimo wastewater treatment facility. How much biosolids material will be used? The project will require approximately 500 dry tonnes (2,000 bulk tonnes) of biosolids—approximatey 180 truck loads. What will the fertilized sites look like? The sites will appear to be covered by a rich, dark topsoil material to a depth of two centimeters. Because this is a drier application method than was utilized in the 1992 project, little if any material will remain on the trees. 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. Closer to home, farmers in Parksville and Qualicum have been using biosolids from the French Creek Pollution Control Centre to fertilize their agricultural land. Also, Comox composts its biosolids for sale to commercial and home gardeners. 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. Vancouver Island University’s 1992 project demonstrated significant increases in the health and growth rates of trees without detrimental effects on the environment. Is there sufficient soil depth on-site to apply biosolids? The sites where biosolids are to be applied have been carefully surveyed and classified. Soil depths in the proposed treatment areas are at least one metre. Our 1992 project, which also treated sites in the immediate area, showed that soil depths are adequate to support trees and to provide a buffer for any movement of materials into groundwater. Vancouver Island University Forest Fertilization Project comparison of trace mineral content with Ministry of Environment Guidelines Dry
Weight Concentrations – (mg/kg)
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Paul Lucas, R.P.F. [ Discover/VIU ] Produced by the Communications & Public Relations Department Copyright 2002 © Vancouver Island University |
