Biosolids are nutrient-rich organic materials from the treatment of domestic sewage in a wastewater treatment facility. Biosolids are a beneficial resource, containing essential plant nutrients and organic matter and are recycled as a fertilizer and soil amendment. When sewage solids are treated and processed, these residuals can be recycled and applied as biosolids to improve and maintain productive soils and stimulate plant growth. In the U.S., sewage solids must be treated to meet EPA‘s Part 503 sewage sludge regulatory requirements if they are to be recycled as biosolids.

EPA estimates that more than 7 million dry tons of solids are generated annually for use or disposal by the 16,000 wastewater treatment facilities nationwide. Several biosolids management options are available under the Part 503 regulations. Approximately 60% are land applied, composted, or used as landfill cover, 22% are incinerated, and the remaining 17% are disposed of in landfills.

NACWA and WEF believe that EPA‘s risk assessment for the 40 CFR Part 503 Rule, which governs the use and disposal of sewage sludge and biosolids, is adequate to protect human health and the environment when biosolids management practices prescribed in the rule are followed. Wastewater treatment and biosolids management programs across the country strive to carefully follow all applicable regulations and best management practices in the Part 503 and parallel state rules. Professionals managing biosolids concur with EPA‘s long-standing appraisal that biosolids recycling is a relatively low-risk activity. Nonetheless, there will always be new information and questions arising about various aspects of biosolids management. But, the questions being studied today are often about more subtle potential risks than those that have been studied and addressed intensively over the past thirty years (e.g. heavy metals).

Decades of experience and hundreds of studies regarding biosolids recycling make it unlikely that there are any significant negative surprises yet to be discovered about this form of recycling. A comprehensive National Academy of Sciences/National Research Council review of the Part 503 biosolids management program in 1996 found biosolids use on food and other crops presents "negligible risk" when conducted in accordance with federal regulations. Many state regulations are significantly more restrictive than the Part 503 regulations, thus further safeguarding public health and the environment. Wastewater treatment facilities are highly regulated under the Clean Water Act and other regulatory requirements. Pretreatment and pollution prevention programs, in particular, contribute significantly to enhancing biosolids quality. Biosolids recycling is a highly regulated management practice, even though biosolids are only applied on one percent of the nation‘s agricultural acreage. In comparison, other soil amendments and fertilizers that are applied on the majority of agricultural land (manure and commercial fertilizers), are minimally regulated, if at all, and no pathogen testing is done on them. -- from the National Biosolids Partnership

http://biosolids.org/docs/Guide_to_Understanding_Biosolids_Issues_052506.pdf