The land application of biosolids (non-hazardous sewage sludge) has been in practice in Arizona since the 1960s. The controlled use of biosolids in agriculture and land reclamation provides numerous benefits. Biosolids are an excellent renewable source of plant nutrients such as nitrogen, phosphorous, copper and zinc, see table below. Biosolids provide much needed organic matter to our desert soils, improving their structure, water holding capacity and ease of management. The use of biosolids as fertilizers helps reduce the dependence on oil- derived commercial synthetic fertilizers and saves valuable landfill space. However, even treated municipal biosolids can contain organisms (pathogens) capable of transmitting and producing diseases and very low (trace) levels of toxic chemicals. Therefore, there are potential risks associated with the repeated use of biosolids, including the accumulation and uptake of pollutants in soils and plants, and groundwater and surface water pollution. But alternate forms of sludge disposal, such as land filling, incineration (not allowed in Arizona) and ocean dumping (practiced in coastal states but banned since 1988) are costly and pose greater risks to our health and the environment.
The following sections describe how biosolids are produced, summarize federal and Arizona regulations that control their disposal on land, present an overview of the research on biosolids at the University of Arizona, and answer some common questions about the land application of biosolids. All humans produce waste, so we are all part of the problem. The continued safe use of biosolids depends on an informed public and its participation. It is also important to support biosolids research and monitoring programs and regulations that are responsive to new health and environmental protection concerns, as they arise.