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Biosolids are the treated residues generated during the processing of domestic sewage at a water recycling center. They are primarily composed of dead microorganisms that consumed organic material in wastewater and were then harvested. Biosolids can be solid, semi-solid, or liquid in form. Biosolids are a natural organic fertilizer and soil conditioner which provide a full complement of the essential nutrients and micronutrients necessary for healthy plant growth.

Biosolids can be beneficially used in agriculture (direct land application) or they can be made into compost for application on lawns, gardens, and trees. Land application involves applying biosolids to rangeland, forests, cropland, or public parks. Composting involves mixing biosolids with another organic waste material, wood chips.

Use of biosolids or compost made from biosolids returns a useful resource to the environment and has a number of very beneficial effects:

  • Accelerates plant growth and produces a healthier plant
  • Improves moisture retention in the soil
  • Increases organic matter in the soil
  • Improves erosion control
  • Reduces dependence on inorganic fertilizers
  • Reduces the volume of material disposed of in landfills, reducing costs and prolonging landfill life
  • Nitrogen is released to the soil slowly, preventing any excess nitrogen from seeping into groundwater

Biosolids have been used in many places throughout the country for decades and there have been no toxic effects or infectious disease outbreaks associated with their use.

  • State and federal regulations regarding the safe use of biosolids were designed to be overly conservative so that workers and the public have a high degree of protection.
  • SAWS has a nationally recognized Pretreatment Program that ensures biosolids derived from domestic sewage contain low levels of metals and chemical pollutants.
  • Proper handling and processing of biosolids ensures the product contains low numbers of pathogens and produces few odors. High temperatures in the compost production process effectively kill disease-causing organisms.