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Using sewage sludge as fertilizer.

University of Arizona researchers at the National Science Foundation supported Industry/University Cooperative Research Center on Water Quality (also known as the Arizona Water Quality Center or WQC) have documented that the use of treated sewage sludge as an agricultural fertilizer is unlikely to expose humans and the environment to disease-causing microorganisms.


The scientists undertook their work in the wake of a published report that raised concerns about bacterial infections detected in some individuals living near sites where so-called biosolids--organic residues produced by treating municipal sewage to remove bacteria and other human pathogens--had been applied to farmland. Conducted at geographically diverse sites around the United States, the WQC's research has shown that the risks of exposure to pathogenic organisms, including bacteria and viruses that inhabit the human digestive system, are very low as little as 60.96 meters (200 feet) away from the sites where biosolid fertilizers are applied.

Although the land application of biosolids is highly controversial in many communities, to date there has been little scientific evidence to quantify the risks of off-site human exposure to disease-causing organisms.

Communities are often concerned about whether the use of biosolid fertilizers could lead to migration of bacteria and viruses away from the site of application, for instance in aerosols carried by air currents or by movement of pathogens through soil and into groundwater. WQC scientists have devoted particular attention to the issue of human exposure to bioaerosols, analyzing more than 1,000 air samples collected at various biosolid application sites around the country.

The study is the first to examine the potential for exposure to actual human enteric (that is, gut-dwelling) viruses, including the viruses that cause polio and encephalitis. Exposure was also assessed for several different bacterial species including Salmonella, E. coli, and Staphylococcus aureus.

WQC's analysis shows that human exposure takes place only during actual application of biosolids. The potential for exposure exists for less than one minute and only in the vicinity of equipment that spreads biosolids on agricultural fields. Just a short distance from the application site, the risk of exposure to pathogens in bioaerosols drops dramatically.

For more information, contact Ian Pepper, 520-626-3328,
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Title Annotation:Update
Publication:Resource: Engineering & Technology for a Sustainable World
Geographic Code:1USA
Date:May 1, 2004
Previous Article:'Shocking' research points to ways to protect technology.
Next Article:Nutrient management: dairy farm manure treatment to make solids and liquids usable.

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