PTO vs Engine-Driven Manure Pumps: How to Size One
For most farms running their own manure with existing tractors in the 200 to 300+ horsepower range, Hoover Ag’s PTO pump covers the job.
Biosolids are the nutrient-rich organic material produced when wastewater treatment plants treat sewage sludge to meet federal and state standards for beneficial use. The key word is treated. Raw sewage sludge is not biosolids. Biosolids are what you get when sludge has been processed to reduce pathogens, control vector attraction, and limit heavy metal concentrations to levels considered safe for land application.
Pennsylvania generates about 2.2 million tons of wastewater solids each year, or roughly a quarter ton per household. That material has to be managed somehow. When it’s treated to biosolids standards, it becomes a fertilizer and soil amendment that can be applied to farmland, forests, reclamation sites, and (for the highest-quality class) home lawns and public spaces.
The regulatory framework is federal (EPA’s 40 CFR Part 503) with state implementation. In Pennsylvania, PA DEP regulates biosolids under 25 Pa. Code Chapter 271, Subchapter J. Individual states can add stricter requirements on top of the federal rule.
Wastewater treatment plants receive raw sewage from homes and businesses. The treatment process separates the liquid effluent (which is treated further and released) from the solids that settle out. Those solids are what eventually become biosolids.
The solids go through additional treatment steps to stabilize the material and reduce pathogens. Common treatment processes include anaerobic digestion, aerobic digestion, composting, heat treatment, alkaline stabilization (adding lime), and drying. The specific process determines the classification of the resulting biosolids.
Once treated, the biosolids are tested for pathogen levels, pollutant concentrations, and vector attraction characteristics. If they meet the standards, they can be land-applied. If they don’t, they have to be further treated, incinerated, or landfilled.
Federal regulations divide biosolids into two main classes based on how thoroughly pathogens have been reduced during treatment. This distinction drives almost everything else about how the material can be used.
Class B biosolids have gone through a “Process to Significantly Reduce Pathogens” (PSRP). Pathogens are reduced substantially but not eliminated. Because pathogens may still be present, land application of Class B biosolids comes with site restrictions: they can’t be applied to sites with high potential for human exposure, access to the site is limited for a period after application, grazing animals are kept off for a specified time, and harvesting is restricted for certain crops.
Class B is the more common classification for biosolids applied to agricultural land in Pennsylvania. Common receiving crops include corn, alfalfa, hay, and small grains. Application requires a PA DEP permit, and the operations are subject to the notification and record-keeping requirements described in the biosolids land application process.
Class A biosolids have gone through a “Process to Further Reduce Pathogens” (PFRP). Pathogens are reduced to essentially non-detectable levels. Because there’s minimal remaining pathogen concern, Class A biosolids can be used in a much wider range of settings: home lawns and gardens, parks, golf courses, and other places where public contact is likely. Site permits generally aren’t required for Class A products, though generators still have to meet quality standards.
Class A biosolids products include composted biosolids, digested and lime-pasteurized biosolids, and heat-dried pellets. You’ve probably seen bagged compost or fertilizer at a garden center that includes biosolids as an ingredient. Those are Class A materials.
Both are EPA-defined categories of treatment processes. PSRP includes things like aerobic digestion, anaerobic digestion, air drying, and lime stabilization at defined times and temperatures. PFRP includes composting at defined temperatures, heat drying, heat treatment, and other higher-intensity processes. The technical distinction is in the specifics of the treatment; the practical distinction is how thoroughly pathogens are reduced.
There’s a third category worth mentioning: Class A “Exceptional Quality” or EQ. This isn’t a separate legal class in the same sense as A and B, but it refers to Class A biosolids that also meet the most stringent standards for chemical pollutants and vector attraction reduction.
Class A EQ biosolids are the least restricted category. They meet or exceed the highest quality standards on pathogens, pollutants, and vector control, which means they can be distributed and used with the fewest restrictions. Bagged biosolids products sold to homeowners are typically Class A EQ.
The Part 503 rule regulates three categories of concerns in biosolids.
Pathogens. Bacteria, viruses, parasites that could cause disease. Treatment processes reduce these to specified levels for each class.
Heavy metals and other pollutants. Concentrations of arsenic, cadmium, copper, lead, mercury, molybdenum, nickel, selenium, and zinc are limited both in the material itself and in cumulative loading to the receiving site. Some of these elements are actually micronutrients that plants and animals need in small amounts, but at high concentrations they become problems.
Vector attraction. Vectors are organisms like flies, rodents, and birds that could carry pathogens from biosolids to other places. Treatment processes reduce the biosolids’ attractiveness to vectors.
The rule doesn’t currently regulate PFAS (per- and polyfluoroalkyl substances) at the federal level, though EPA and state regulators are studying the topic actively. Some states have added PFAS testing or restrictions, and some biosolids programs now include PFAS characterization as part of routine testing.
The regulatory answer is that biosolids meeting Class A or Class B standards under Part 503 are considered safe for their permitted uses. The scientific consensus, based on decades of research by EPA and independent researchers, supports this. Land application of biosolids is used across the United States and in most industrialized countries.
The honest longer answer is that biosolids are safer at Class A than at Class B, which is why site restrictions apply to Class B. The regulations are designed to keep the exposure to the level of remaining pathogens or pollutants within acceptable limits.
The PFAS question is genuinely open, and this is where you’ll see the most current debate. That’s worth watching as regulations evolve.
Class B biosolids can have a noticeable odor, particularly during and immediately after application. This is the source of most public complaints about biosolids land application. Injection application (placing the material below the soil surface with a dragline injector) reduces odor significantly compared to surface application.
Class A biosolids, particularly the composted or heat-dried forms, typically have minimal odor because the treatment processes that produce them also reduce odor-generating compounds.
Application timing is governed by the permit, the site conditions, and Pennsylvania’s application rules for the type of material. Winter application is generally restricted or avoided. Wet or frozen ground shifts what’s possible. The specific windows depend on the site’s permit and the operator’s plan.
Both are organic materials applied to farmland as nutrient sources and soil amendments. Manure comes from livestock. Biosolids come from municipal wastewater treatment. Manure has its own regulatory framework under Pennsylvania’s nutrient management rules. Biosolids fall under the separate biosolids regulatory framework. The application equipment is often the same or similar (dragline systems, injectors, dribble bars, tanker spreaders), but the materials and the rules are different.
Food processing residuals come from food manufacturing facilities and have their own regulatory framework in Pennsylvania. Biosolids come from municipal wastewater treatment. Both are organic materials that can be land-applied, both are regulated, but they’re different categories with different rules.
For farms and applicators dealing with biosolids in Pennsylvania, understanding the class distinctions is the foundation for understanding what’s possible at a given site. Class B is what typically shows up in agricultural land application. Class A shows up more in horticultural, reclamation, and non-agricultural uses.
For the equipment and process side of land application, the companion piece on land application of biosolids covers the operational detail. The Hoover Ag manure equipment lineup includes the injectors, dribble bars, hose reels, and pumps that most biosolids applicators use for liquid application. Call (610) 468-9666 or get in touch if you want to talk through equipment for a biosolids operation.
Sources cited in this guide:
For most farms running their own manure with existing tractors in the 200 to 300+ horsepower range, Hoover Ag’s PTO pump covers the job.
If you haul or broker manure commercially in Pennsylvania, you need a certification, you need to maintain it with continuing education, and you need to keep records that prove you’re doing the work within the rules.
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