University of Missouri Extension

WQ424, New May 1994

Biosolids Standards for Pathogens and Vectors

Ken Arnold
Chief of Land Application, Missouri Department of Natural Resources
John H. Dunn
Environmental Engineer, Environmental Protection Agency Region VII
Dennis Sievers
Department of Agricultural Engineering

Biosolids is domestic wastewater sludge that meets standards for use as a fertilizer or soil conditioner. Biosolids standards include limitations for metal and other compounds, pathogen reduction, vector requirements and best management practices.

EPA regulations, under Title 40 Code of Federal Regulations Part 503 (40 CFR 503), establish the minimum national standards for the use and disposal of domestic sludge. These standards include limitations for the land application of biosolids. This publication outlines biosolids standards for pathogens and vectors.

Pathogen limitations for Class A biosolids

Class A biosolids are required for application onto public-use sites and certain food crops. This includes residential areas, road banks, parks, golf courses, schools and other similar areas.

Class A is also required for applying biosolids to turf, vegetable crops, root crops or home gardens.

Alternatives for Class A pathogen treatment

Class A biosolids must meet one of the following bacteria limitations and one of the process treatment alternatives:

Bacterial limitations

Biosolids must comply with one of the following:

Class A Process treatment alternatives

Biosolids must also meet one of the following:

Table 1
Processes to Further Reduce Pathogens (PFRP)


Pathogen limitations for Class B biosolids

Apply Class B biosolids on grain and forage crops, pastures, grassland, fallowland and timberland.

The alternatives for Class B biosolids consist of either a treatment process, such as a Process to Significantly Reduce Pathogens (PSRP) or a bacteria limitation, based on fecal coliform.

Fecal coliform testing is recommended for all treatment processes for at least two years of operation in order to verify PSRP performance. Conduct tests during seasons of the year when biosolids will be applied. Equivalent PSRP processes must be approved by the permitting authority.

Alternatives for Class B pathogen treatment

Table 2
Processes to Significantly Reduce Pathogens (PSRP)


Table 3
Processes approved by EPA as equivalent to PSRP. (Control of Pathogens and Vector Attraction in Sewage Sludge, EPA/625/R-92/013, Dec. 1992.)


Alternatives for vector attraction treatment

All biosolids (Class A and Class B) must meet one of the following alternatives for vector attraction reduction:

WQ424 Biosolids Standards for Pathogens and Vectors | University of Missouri Extension

Order publications online at or call toll-free 800-292-0969.

University of Missouri Extension - print indicia