Irradiation as a means to minimize public health risks from sludge-borne pathogens

The purpose of the Federal Water Pollution Control Act of 1972 (PL 92-500) and later amendments was to improve the quality of U. S. surface and groundwater supplies, which had been seriously degraded through the years by the disposal of wastes into this convenient me dium. Industry is a major source of toxic chemicals that are waste products of many commercial processes. An other major source of surface water contamination is the discharge of toxic chemicals and nutrients from the wastewater treatment plants that serve growing popu lations often concentrated in metropolitan areas. The implementation of the Clean Water act has forced industry and municipalities to provide additional purifying treatments so that the effluents discharged to receiving waters would have much lower levels of un desirable contaminants. These additional treatments have dramatically helped to clean up municipal and in dustrial effluents. However, this success has proved a mixed blessing. As effluents have become cleaner, the volume of treatment by-products has increased in direct proportion. These by-products, known as sludge, are made up of the particulate material removed from liquid waste as it progresses through various treatment pro cesses. About 8.1 M dry metric tons of sludge annually, and greatly increased amounts by the end of the decade, create special disposal problems. The same (and similar) environmental legislation has limited the options for managing the increasing volume of sludge. Ocean dumping has been severely curtailed, and its ultimate fate is under review. The energy costs and air pollution associated with the incineration of sludge generally make this disposal option undesirable. Increasing population pressures on land area and soaring transportation costs have decreased the attractiveness of landfilling. The Resource Conservation and Recovery Act (PL 94-580) and a general national interest in resource re cycling and conservation have prompted a new per spective toward sludge management options. Sludge has been shown to be an excellent source of macronutrients and trace minerals for soils as well as of organic matter