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Frequently Asked Questions


What are biosolids?

Biosolids are nutrient-rich organic matter resulting from the treatment of wastewater. Valuable nutrients include nitrogen, phosphorus, iron, calcium, magnesium and various other macro and micro nutrients that are essential for plant growth.  Once treated and processed, this by-product has minimal odor and eliminated pathogens.  It can then be recycled and applied like a fertilizer, improving and maintaining productive soils and stimulating plant growth.

Read about the history of biosolids.


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Where are biosolids applied?

Farmers and gardeners have been recycling biosolids for ages, using it as a soil conditioner to improve and maintain the structure of soil.  The City of Santa Rosa applies biosolids to agriculture farms for fodder crops such as hay, rye and oat.  Biosolids can also be used for nonagricultural purposes, such as forestry and mine site reclamation.  Recycling of biosolids on land has increased over the past 20 years. Over 50 percent of all biosolids in the U.S. are managed through recycling. Land application of biosolids takes place in all 50 states.

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What are the benefits of land applying biosolids?

Land application of biosolids is beneficial to farmers, municipalities and the community. Biosolids recycling and reuse add nutrients and positive soil characteristics to agricultural land, which increases crop growth and yield. Recycling biosolids saves local and state governments significant amounts of money through lower management costs, while keeping the biosolids out of the landfill and decreasing negative impacts on the environment.

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Are biosolids safe?

Decades of studies have demonstrated that biosolids can be safely used on non-human consumed crops. The National Academy of Sciences has reviewed current practices, public health concerns and regulator standards, and has concluded that "the use of these materials in the production of crops for human consumption when practiced in accordance with existing federal guidelines and regulations, presents negligible risk to the consumer, to crop production and to the environment." In addition, an epidemiological study of the health of farm families using biosolids showed that the use of biosolids was safe.


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Where can I find out more about the regulations?

The biosolids rule is described in the EPA publication, A Plain English Guide to the EPA Part 503 Biosolids Rule. This guide states and interprets the Code of Federal Regulation (CFR) Part 503 rule for the general reader. This guide is also available in hard copy. In addition to the Plain English Guide, EPA has prepare A Guide to the Biosolids Risk Assessments for the EPA Part 503 Rule, which shows the many steps followed to develop the scientifically defensible, safe set of rules (also available from EPA in hard copy.


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Why do we have biosolids?

Thirty years ago, thousands of American cities dumped their raw sewage directly into the nation's rivers, creeks, lakes and bays. Today's wastewater treatment technology separates the water from the solids during treatment, allowing discharged water to be safer and solids to be recycled back into the nutrient cycle.

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Why are biosolids recycled?

Generally, recycling biosolids have numerous benefits.  They are a valuable source of organic matter, which improves soil structure.  It includes rich nutrient fertilizer, nitrogen and phosphorus and is valuable on cropland.  The organic nitrogen is less likely to cause groundwater pollution than chemical nitrogen fertilizers, and it greatly reduces the disposal into disappearing landfills. 

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