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Biosolids Management Program
Mission | Philosophy | What Are Biosolids? | Why Recycle Biosolids? | Biosolids Quality | Recycling Projects | Nutri-Green® Compost | Agricultural Land Application | Research and Demonstration | Ash Recycling | Heat Dried Biosolids Fertilizer
Mission
HRSD’s biosolids management program goal is to recycle biosolids in a beneficial, cost effective, environmentally sound and publicly acceptable manner. HRSD has numerous recycling programs in place to provide stability and diversity for its nine-wastewater treatment facilities located in the Hampton Roads area. Current programs include land application of biosolids to farmland, composting, and ash recycling. HRSD long-range goal is to further develop these programs through research and demonstration programs and evaluate other beneficial methods of recycling biosolids.
Philosophy
Biosolids recycling provides a rich source of organic matter, nutrients and micronutrients or trace elements essential for the maintenance of healthy soils and vigorous plant growth. Recycling biosolids to agricultural land through land application and compost application to home gardens and landscape plantings eliminates the otherwise wasteful disposal of a beneficial natural resource in landfills. Biosolids quality is effectively safeguarded through proper wastewater treatment, extensive industrial pre-treatment and education.
What Are Biosolids?
Biosolids are a nutrient-rich organic material resulting from the natural biological and physical treatment of wastewater. Solids are separated from the liquid portion of municipal wastewater during the treatment process. These separated solids contain primarily organic material, sand, nutrients, microorganisms, and trace amounts of metals. The solids can be further processed by several biological, chemical or physical methods depending on the end usage. The resulting biosolids are either liquid or a moist to dry soil-like material that generally have a mild organic odor that dissipates rapidly after application.
Why Recycle Biosolids?
Biosolids recycling returns a useful resource to the environment. Biosolids are rich in nutrients, containing nitrogen and phosphorus along with other supplementary nutrients such as potassium, sulfur, magnesium, calcium, copper, zinc and iron. Since most of the nutrients are in the organic form, biosolids acts as a slow release fertilizer and soil conditioner. The application of biosolids to land improves soil properties and plant productivity, and reduces the dependence on inorganic fertilizers. Improving soil structure helps reduce wind and water erosion. Biosolid application rates are calculated based on the crop nitrogen requirement and the soil productivity class to help eliminate any potential leaching to groundwater.
- Farmers can take advantage of the many plant nutrients and soil enhancement properties provided by biosolids. By doing so, farmers can save anywhere from $75-$100 per acre, significantly increase their crop yields, reduce erosion and reduce runoff associated with the use of inorganic fertilizers.
- Commercial landscapers and home gardeners use biosolids compost to establish or enhance lawns and gardens.
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Biosolids Quality
Biosolids quality is determined by analyzing its constituents. Biosolids are monitored routinely for nutrients, trace metals, specific indicator microorganisms, solids content, organic compounds and pH. HRSD tracks these constituents on a monthly basis; the results of these analyses are available by request. HRSD biosolids meet all quality and safety standards established by Federal, State and local regulators. HRSD safeguards biosolids quality through small business and household education programs, treatment plant controls, and industrial pretreatment and source control regulations.
- Trace metals - Many of these metals are essential plant micronutrients that are found naturally in soils. The small amounts of trace metals found in biosolids come from water and wastewater piping systems and discharges from businesses, industries and homes. Metals levels in HRSD biosolids are extremely low due to very low industrial inputs and HRSD’s extensive industrial pretreatment program.
- Microbes - Wastewater contains beneficial microorganisms from the human digestive system. Biosolids may also contain pathogenic, i.e. disease-causing, bacteria and other organisms. The wastewater treatment process significantly reduces the numbers of these pathogens by creating an unfavorable environment for their survival. When applied to land, heat, cold, drying and competition with native soil microorganisms further reduce these pathogens eliminating any health risks. Both composted and heat-dried biosolids are virtually pathogen-free.
- Organic Compounds – Biosolids may contain very small traces of organic compounds. These compounds come from industries and homes. Research indicates that organic compounds are held in the soil and are not taken up by plants. Eventually natural soil microbes and environmental conditions degrade them.
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HRSD Biosolids Recycling Projects
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Nutri-Green® Compost
HRSD supplies biosolids to a private company that composts the biosolids with recycled paper products and woodchips to make Nutri-Green® Compost. The materials are mixed together to form a homogenous mix. The mixture is placed in long windrow piles where it is turned frequently. The pile temperatures and oxygen content are monitored to ensure aerobic conditions are maintained and the product is fully stabilized prior to distribution. The compost process takes approximately 60 days to complete. The final product is screened to remove large woodchips that are recycled back to the initial mixing process. The final product is sampled and tested monthly for nutrient and trace metal content to ensure compliance with regulatory criteria. Nutri-Green® Compost is sold to landscapers, nurseries and the general public, and is widely used in commercial and home landscaping and gardening.
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Agricultural Land Application
HRSD has been recycling biosolids to farmland through the practice of land application since 1981. Similar products are produced all over the world and recycled to farmland as well. Europe and Asia have been land applying biosolids for centuries.
HRSD’s Nutri-Green® Biosolids are applied to over 1,500 acres of farmland per year in Virginia Beach and Chesapeake. Biosolids, which are generally used to grow corn, wheat and soybeans; are beneficial to the environment. Biosolids replace chemical fertilizers and help reduce the chance of runoff of nutrients to surface waters.
Biosolids recycling on land helps farmers by saving them money and benefits crops by increasing crop yields. Biosolids have been thoroughly researched by top scientists at institutions all over the world and have been found to be safe to human health and the environment when processed and applied properly.
The U.S. Environmental Protection Agency and the Virginia Department of Environmental Quality have established regulations that mandate monitoring of the quality of biosolids before recycling, set criteria for the acceptable contents of biosolids and developed site specific management practices for controlling application.
Biosolid application rates are calculated based on the crop’s nitrogen requirement and the soil’s productivity class to help eliminate any potential leaching of excess nutrients to groundwater. HRSD monitors the biosolids on a routine basis to ensure a high quality product is continuously produced. All biosolids generated and applied to farmland by HRSD are in compliance with federal, state and local regulations.
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Research and Demonstration
HRSD has established an extensive monitoring program on its Progress Farm to document the long-term effects and benefits of applying biosolids. The Progress Farm has been in operation more than 20 years. During the early 1980's, HRSD gathered comprehensive data on soil, groundwater and surface water quality on the Progress Farm for two years prior to applying biosolids. This data has provided a scientific baseline to study the long-term effects of biosolid land application. All monitoring data continues to confirm that biosolids are a safe and effective source of nutrients and organic matter. Much of the initial research conducted on the farm was done in conjunction with Virginia Tech and the Virginia Cooperative Extension. Continued research and demonstrations in cooperation with area universities confirm the advantages and safety of biosolids.
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Ash Recycling
HRSD generates approximately 10,000 tons of incinerator ash annually. This bio-ash is recycled into various products for use. The material has been used as a flowable fill in a combined coal ash-biosolids ash mixture and in a bio-ash natural mixture. It has been used extensively as a select fill material and as a component of soil cement. Its unique properties provide a higher compressive strength than many conventional materials. Bio-ash has also been used as a component in landfill cover material and potting soil mixes. The ash recycling program saves HRSD and its customers an estimated $180,000 per year by diverting the ash from landfills to recycling projects.
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Heat-Dried Biosolids Fertilizer
HRSD completed a successful pilot project in 2000 that showed biosolids can be heat-dried to produce high quality turf and landscape fertilizers. This is another option HRSD will evaluate as it develops a biosolids management program that is beneficial, cost-effective and environmentally sound.
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