Biosolids are the materials resulting from the treatment of domestic sewage that has been sufficiently processed to permit the material to be safely land applied.

The key words here are, sufficiently treated. Not all materials coming from waste treatment plants are the same. The name biosolids are used to distinguish these materials from sewage sludge, which has been under-treated and may contain large amounts of pollutants.

Biosolids are produced primarily through biological treatment of domestic wastewater. Physical and chemical processes are often employed to improve the handling characteristics, increase the economic viability of land application and reduce the potential for public health, environmental and nuisance problems associated with land application.

These processes sanitize wastewater treatment solids to control disease-causing organisms and reduce characteristics that might attract rodents, flies, mosquitoes or other organisms capable of transporting infectious disease.

The suitability of biosolids for land application can be determined by biological, chemical and physical analysis.

The composition depends on what went into the plant and the treatment processes.

The resulting properties will determine if the product is suitable for land application and, if so, the application method and rate, and the degree of regulatory control required.

Nutrients are elements required for plant growth. The nutrients in biosolids provide their economic value. The biosolids produced by the Butler County Department of Environmental Services (BCDES) contain about 45-50 pounds of available nitrogen per dry ton.

In addition, phosphorus, potassium, calcium, magnesium, sulfur, boron, copper, iron, manganese, sodium, molybdenum and zinc are all contained in biosolids in varying amounts.

Trace elements are found in low concentrations in biosolids. These trace elements are commonly referred to as heavy metals. Some of these trace elements such as copper, molybdenum and zinc are nutrients needed for plant growth in low concentrations.

All of these elements can be toxic to humans, plants or animals in high concentrations. Federal and state regulations have established standards for nine trace elements. Biosolids can be considered as a waste to be disposed of or as a beneficial soil amendment. In 2005, about 33 percent of the biosolids generated by BCDES was land applied. The rest were disposed of through landfill.

BCDES is working to increase the percentage that is land applied. For those interested in learning more about land application, call at 887-3722 or 424-5351, ext. 3722.

The views and opinions expressed in this column are those of the author and not necessarily those of Farm World. Readers with questions or comments for Steve Bartels may write to him in care of this publication.

This farm news was published in the April 5, 2006 issue of Farm World.