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Land Application of Biosolids: A Review of Research Concerning Benefits, Environmental Impacts, and Regulations of Applying Treated Sewage Sludge

The Water Quality Act of 1972 that mandated development of technologies to treat, dispose, and recycle nutrients in wastewaters and sludges dramatically increased land application of sewage sludge by municipalities across the nation. Sewage sludge is produced from wastewater treatment plants operated by municipalities. Land-applied sewage sludge undergoes chemical and biological transformations that affect plant nutrient availability and determine the environmental fate of its constituents. After land application, most organics are rapidly adsorbed, volatilized, or decomposed and present little risk to the food chain. Land application of sewage sludge benefits crop production by supplying a wide range of plant nutrients. Forages grown on sludge-fertilized lands have been utilized by grazing ruminants, principally beef cattle, while grain crops from these sites have been used by both monogastrics and ruminants. Sludge utilization projects on forestland for reforestation, biomass production, and fertilization have been established in 23 states. Several research studies have examined the effect of land application of sewage sludge because of the concern that it could contaminate surface or ground waters. Use of sewage sludge as a source of plant nutrients and as a soil amendment on native ecosystems such as forest and grassland has been studied. Because native ecosystems are sensitive to mechanical disturbances and may show long-term effects of such treatments, sewage sludge should be surface-applied. Land application of sewage sludge has been used to reclaim coal strip-mine spoils, gravel spoils, coal refuse, clay strip-mine spoils, iron ore tailings, abandoned pyrite mine spoils, and sites devastated by toxic fumes. Many of the trends associated with land application of sewage sludge established during the last 25 years are likely to continue. Land application will increase, and incineration, landfilling, and other alternative sludge disposal methods will decrease. The next 25 years will bring an increase in beneficial land application of new waste materials including municipal solid waste and possibly “designer sludges.” Knowledge gained from sewage sludge research and methods used to regulate land application will be essential for beneficial land application of new materials.




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