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The unique climate of the Pacific Northwest creates interesting challenges and requires innovative solutions for biosolids management. The wet climate much of the year creates challenges for biosolids managers, but also presents unique local opportunities.

While Class A biosolids facilities are common in many other parts of the country, the abundance of agriculture and forests in the Pacific Northwest makes Class B biosolids land application attractive and cost-effective. Recent public and regulatory pressures are now driving many utilities in the Pacific Northwest to consider Class A biosolids production.

Discussions with state regulatory agencies, biosolids managers, industry associations, and equipment manufacturers revealed that approximately 40 facilities in the tri-state area of Washington, Oregon, and Idaho produce Class A biosolids. Technologies utilized in the northwest to produce Class A/Exceptional Quality (EQ) biosolids include autothermal thermophilic aerobic digestion (ATAD), lime stabilization, composting, thermal drying, and air/solar drying. There is a relatively high concentration of facilities in the Puget Sound region and in the Olympic Peninsula due to the population density and the lack of available nearby application sites for Class B biosolids. The most popular Class A processing option in the region is composting. Most Class A facilities in the Pacific Northwest are located in small to medium-sized wastewater treatment plants.

Markets for Class A biosolids in the northwest include traditional Class B markets - dry land wheat farming, grass seed farming, reclamation sites, and forestry/silviculture – and higher-end markets such as nurseries, landscapers, soil blenders, and private citizens. Each market has different product quality standards and seasonal demands.

Many lessons have been learned from northwest Class A facilities. Managing odors, marketing, aesthetics, costs, and storage facilities are critical factors in the success of Class A facilities. Class A is not a universal solution. In many cases, the odor, debris levels, and other aesthetic characteristics of biosolids are more important to the public and biosolids end-users in the region.

Document Type: Research Article


Publication date: January 1, 2004

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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