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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

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Biosolids: treated sewage sludge
Biosolids: treated sewage sludge

Sewage Sludge/Biosolids Program

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“Sewage Sludge” refers to the solids separated during the treatment of municipal wastewater. The definition includes domestic septage. “Biosolids” refers to treated sewage sludge that meets the EPA pollutant and pathogen requirements for land application and surface disposal. See EPA’s biosolids program at the national level for more general information and documents.

Treatment, Use and Disposal Practices in Region 9

The most common treatment of sewage sludge in Region 9 is by anaerobic digestion to “Class B” pathogen reduction levels. Most methane generated during the digestion process is used for co-generation or heating. About 1/3 of the biosolids receive further treatment to Class A pathogen reduction levels, by means such as composting, solar air-drying, alkali treatment, thermophilic digestion, pasteurization, or heat drying. Many small treatment plants use methods of treatment other than anaerobic digestion, such as air drying, aerobic digestion, or lime treatment. Under certain conditions, these processes meet Class B pathogen reduction.

Over 95% of the sewage sludge in Region 9 meets EPA's most stringent pollutant concentration limits for land application and surface disposal (see Biosolids Quality spreadsheet (.xls 67K) for pollutant levels of the major biosolids producers in Region 9). Municipal treatment plants control what pollutants can be discharged to their system through the pretreatment programs required under 40 CFR 403.

Most biosolids in Region 9 are used for growing agricultural non-food crops, for landscaping, as alternative daily cover or final cover at landfills, or are landfilled. A very small amount is incinerated. There are several new or proposed projects for heat drying and use as fuel.

Regulatory Program

EPA Region 9

Region 9 tracks and enforces compliance with the self-implementing standards in 40 CFR 503, issues permits in some cases, and provides guidance and technical assistance. Wastewater treatment plants with influent flows over 1 mgd must report to EPA Region 9 on their biosolids use/disposal by February 19 of each year for the previous calendar year (facilities in Arizona report to ADEQ and cc EPA). For a recommended report format, see: Biosolids Annual Report Format (.xls 95K).


Arizona Dept. of Environmental Quality has been authorized to administer EPA’s biosolids program in Arizona.


California’s State Water Resources Control Board adopted its General Order for land application of biosolids in July 2004.

Contact your local Regional Water Quality Control Board for information on whether your project will fall under this.

The CalRecycle LEA’s regulate compost operations.

A number of counties in California regulate biosolids through county ordinances and/or conditional use permits. Check with your county environmental health office for information on county regulations


Hawaii plans to seek authorization of EPA’s program in the future. Hawaii State Department of Health places biosolids conditions in NPDES permits and tracks compliance through its wastewater branch.


Nevada's Department of Conservation and Natural Resources, Division of Environmental Protection places conditions in permits issued to wastewater treatment plants, land appliers, and composters.

Enforcement Actions

Administrative Orders
Eastern Municipal Water District (PDF), Perris, CA (6 pp, 140K) 04-20-2011
City of Corcoran (PDF), Corcoran, CA (4 pp, 109K) Cover letter (PDF), (2 pp, 67K) 04-02-2009
City of Pacifica (PDF), Pacifica, CA (6 pp, 49K) Cover letter (PDF), (2 pp, 25K)
News Release
Guam Waterworks Authority (PDF), Tamuning, Guam (6 pp, 119K) Cover letter (PDF), (2 pp, 77K) 04-06-2007
Clean Water Act Section 308 Information Request Letters
Western Envrionmental, LLC (PDF), Mecca, CA (8 pp, 150K) 03-30-2012

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