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There are Different Classes of Biosolids

The US Environmental Protection Agency (EPA) issued a 40 CFR Rule categorizing biosolids as Class A, Class A EQ, (Exceptional Quality) or Class B. The difference has to do with the level of pathogens and the ability of the material to meet/exceed Vector Attraction Reduction requirements.

What Are Class A Biosolids?

In Class A biosolids, pathogens must be reduced to virtually non-detectable levels and the material must also comply with strict standards regarding metals, odors and vector attraction reduction (VAR) as specified in the US EPA, Part 503 Rule. VAR refers to processing which makes the biosolids less attractive to vectors, which have the potential for transmitting diseases directly to humans or can play a role in the life cycle of a pathogen, as a host.

Examples of vectors are flies, mosquitoes, rodents, birds, etc. Various processes can be utilized to achieve Class A designation such as anaerobic digestion, lime stabilization, composting and thermal hydrolysis. This designation means the material meets U.S. EPA guidelines for land application with no restrictions. Thus, Class A biosolids can be legally used as fertilizer on farms, vegetable gardens, and can be sold to home owners as compost or fertilizer.

The term Class A EQ (Exceptional Quality) is used to describe a biosolids product that not only meet, but exceed, all Class A pathogen reduction metals and VAR requirements.

What Are Class B Biosolids?

Class B biosolids are treated but contain higher levels of detectable pathogens than Class A biosolids. The use of Class B biosolids and may require a permit from the EPA with conditions on land application, crop harvesting and public access. In terms of nutritional value, however, Class B and Class A biosolids are similar as they both contain important nutrients and organic matter.

Due to pathogens, odors and the ability to achieve higher VAR standards with advanced technology, there is a distinct shift away from Class B use and toward Class A and Class A EQ treatment solutions.

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