Facts - Environment(click here for printable pdf copy)
Long-term scientific studies have consistently demonstrated that biosolids recycling is safe and beneficial when performed in accordance with federal regulations and guidance.
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The management of biosolids to minimize environmental and health risks has been the focus of hundreds of university research studies conducted for many years. The results of this extensive research show that biosolids can be managed so that the risk of adverse effects to the environment or public health from land application of biosolids is extremely low.
To ensure that biosolids are treated and appropriately managed, the United States Congress directed the U.S. Environmental Protection Agency (EPA) to develop comprehensive national standards to reduce the risks and maximize the benefits of land application of biosolids. In February of 1993, EPA issued its biosolids use and disposal regulation, 40 CFR Part 503, commonly referred to as "Part 503".
This regulation addresses the following:
A small amount of metals such as cadmium, lead, copper and zinc can enter wastewater from industrial drains, from homes and from metal pipes. These metal pollutants remain in the solids throughout the treatment process. When biosolids are applied to the land, the metals cling to soil particles and organic matter and do not move down into the groundwater. Metals occur naturally in the soil and many metals are actually plant micronutrients. The amount of metals in biosolids is carefully regulated and monitored.
Government limits:In order to protect human health and the environment, the Environmental Protection Agency (EPA) sets limits on the amount of trace metals allowed in biosolids. These levels are based on more than 20 years of research on how trace metals affect soils, plants and animals.
Pretreatment requirements: Rigorous "pretreatment" programs control the amount of metals entering wastewater treatment plants. Laws regulate industries to make sure that they dispose of their chemicals safely. This means that metals are removed from the waste stream before they ever reach the sewer. This ensures that biosolids contain metals only in small quantities.
Biosolids quality: Biosolids are routinely tested for metal concentrations to make sure that they comply with all regulatory requirements. Biosolids in the Pacific Northwest typically meet the strictest requirements set by the Environmental Protection Agency.
Before treatment, wastewater may contain disease-causing microscopic organisms, such as bacteria and viruses, which are known as pathogens, or germs.
Federal law requires treatment to reduce pathogens: Digesters and other forms of treatment kill at least 90 percent of the pathogens originally found in wastewater solids. Additional treatment by heating or composting is required to eliminate pathogens in biosolids used in home gardens and landscapes.
The cleaning process: Conditions such as exposure to sunlight, lack of moisture or a relatively harsh soil environment destroy the few remaining pathogens that may exist in biosolids soon after they are applied to the land.
Biosolids contain organic and inorganic nitrogen and can be applied to plants as a fertilizer to dramatically accelerate growth. However, the addition of too much nitrogen, whether from biosolids or from a commercial fertilizer, can be detrimental to plant growth or can degrade groundwater or surface water.
Sites receiving biosolids applications are carefully selected and managed to ensure the protection of water resources. Farmers and foresters consider plant needs and soil nutrient levels when applying biosolids to their crops and trees, providing only as much nitrogen as the plants can utilize.
Biosolids contain minute concentrations of certain regulated organic compounds including polycyclic aromatic hydrocarbons, phthalates and plasticizers, polychlorinated biphenyls (PCBs) and solvents. Organic compounds found in biosolids are present in such low concentrations (near the lowest detectable limits), that studies have found risks to be negligible. For this reason, the EPA did not include trace organics in the 503 Rule.
Odor issues are a common concern associated with biosolids applications. The odor varies depending upon the treatment process used and ranges from a strong ammonia scent to an earthy, organic smell similar to that of freshly sterilized potting soil. Odor perception varies from person to person.