Safety 
Biosolids are routinely and carefully tested in labs like this to check their quality. Biosolids can be recycled safely for use as a soil enhancer and fertilizer. This beneficial use of biosolids is one of the most extensively studied practices in the U.S. In some parts of the country, biosolids have been recycled as fertilizer for more than 70 years. Decades of research by the University of Washington, Washington State University and other scientists throughout the country form the basis of biosolids regulations and guidelines. King County's biosolids recycling program began in the mid-1970s with research on plant growth response, as well as on potential environmental effects of using biosolids as a soil conditioner and fertilizer. Since that time, the practice of biosolids recycling has grown as benefits to plants and soils were seen in a variety of settings. Monitoring of biosolids shows that quality of the product improved greatly after regulatory programs were implemented in the 1980s to restrict industrial discharges to sewer systems. King County coordinates with federal and state regulators, and partners with other biosolids producers to study and respond to emerging questions about biosolids safety. In response to questions by landowners, regulatory agencies and the public, we continue to fund research programs to help us meet our goals to use biosolids safely and effectively. Regulatory standards
King County biosolids meet the quality standards set by the U.S. Environmental Protection Agency (EPA; 40 CFR 503). The EPA technical standards were the result of many years of field research, detailed human health risk assessment, and careful review by a national panel of scientists with biosolids expertise. These standards were adopted in 1998 by the Washington State Department of Ecology (WAC 173-308).
Biosolids meeting the Class B designation must be used according to certain site management restrictions. In order to be used in areas frequented by the public or on lawns or home gardens, biosolids must be treated further to virtually eliminate pathogens and meet the Class A pathogen reduction criteria. Biosolids may be composted to meet the Class A pathogen designation. This is the process used on compost materials like GroCo, ensuring that they meet the Class A requirements for pathogen content. Find out more on:
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