Linda F. Benedict, Hendrick, Rodney D.
Sewage sludge was the first non-farm organic material to be applied to farm land in large quantities, and it became the first organic material whose application was covered by federal regulations. States now also have regulations governing the land application of sewage sludge. The current federal rules were enacted after much research and public input from all parties interested in the practice. Rules for use of sewage sludge are considered the pattern for other organic materials being land applied. Enacting rules for manures and other wastes based on the sewage sludge rules will create another layer of costs to producers and processors.
Because of the origins of sewage sludge, the federal agency responsible for regulation is the one whose duty is protection of environmental health, the Environmental Protection Agency (EPA). Regulations for treatment standards, content and use are in Volume 40 of the Code of Federal Regulations, Part 503, commonly called the 503s. These regulations establish standards for pathogen reduction, vector attraction reduction and limits on the content of certain metals. They also require that the material not be applied in a manner to create an overabundance of nitrogen in the soil. There are standards for distances from houses, streams and water wells.
The pathogen reduction regulations are designed to assure that the potential for the spread of disease is controlled. There are two levels of pathogen reduction for different uses. Class A is a pathogen level so low that the material is safe to be used in gardens or other places where the plants might be eaten raw. The other pathogen level (Class B) is higher, and the use of the material is restricted to pastures, crops that would not be eaten raw, forests and other non-public areas. These levels are established with a wide margin of safety, and testing is required to document that the standards have been met.
The vector attraction rules are designed to prevent problems with objectionable odors, flies and other nuisance pests. This is accomplished by reducing the active organic part of the sludge. The treatments for this – long-term digestion, heating, sun drying, composting or lime treating – also are those that reduce the potential pathogens.
The third area of regulatory concern is the potential chemical content. The primary concern is the content of certain metals common to sewage sludge and also in most soil and organic matter. These are the “heavy metals.” Many are essential nutrients for plants or animals, and they are listed among the ingredients on many dietary supplements and vitamins as well as trace element supplements in fertilizers. These are copper, chromium, molybdenum, nickel, selenium and zinc. The other regulated metals are arsenic, cadmium, lead and mercury.
The amount of nutrient that can be applied also is regulated by EPA and in Best Management Practice plans on some agricultural wastes. To prevent contamination of ground and surface waters from nutrients released from organic amendments, the application of these materials is limited to the amount needed by the crop to be grown on the application site. These requirements normally have focused on nitrogen, but phosphorus is becoming of more concern in manures in some areas. Although there is some free or mineral nutrient in sewage sludge or manure, most of the nutrient is in the organic matter and will become available over time as the organic matter breaks down.
Regulations for sludge application cover slope, distances from streams, water wells, houses and roads and are designed to protect surface and ground water, human health and to reduce the potential for nuisance complaints. The washing of nutrients and organic matter into streams can harm water quality. Excess nutrients leaching into ground water can create problems with drinking water. The washing of quantities of sewage sludge into streams can cause the water to exceed the bacteria count limit on fecal coliforms for swimming or drinking uses.
The state and federal governments are charged with responsibility to protect the health of the people and the environment that they live in from human and natural impacts. Regulating the treatment and disposal of wastes falls within this function. The long history of the use of manure and sewage sludge in the United States indicates that they can be used safely and beneficially.
Rodney Hendrick, Associate Specialist, Environmental Programs, LSU Agricultural Center, Baton Rouge, La.
(This article was published in the spring 1999 issue of Louisiana Agriculture.)