USE OF MUNICIPAL SLUDGE TO RESTORE AND IMPROVE SITE PRODUCTIVITY IN FORESTRY - THE PACK FOREST SLUDGE RESEARCH-PROGRAM

Municipal wastewater residuals-sludge or biosolids-represent a major waste by-product from society that must be managed in responsible ways, and not released into aquatic systems or allowed to contaminate ground waters. Because of its high nutrient and organic matter content, sludge can be beneficially recycled into forest sites for site improvement purposes. Research to date on forest application of sludge has been very encouraging, clearly demonstrating the validity of this management technique. Forest sites typically display benefits in two ways: (1) an immediate growth response by both overstory and understory species; (2) a long-term improvement to the productivity of the site. However, for this practice to have broad utility and acceptance, it is critical that the concerns of the regulatory agencies and general public be addressed regarding public health and environmental issues through continued research. These concerns include the fate of trace metals, including movement, uptake and potential phytotoxicity, and passage into wildlife and human food chain, the fate of pathogens, and leaching of nitrates into ground water systems. Many concerns are a result of misconceptions or misunderstandings of the potential problems involved and require working with these agencies and the general public through education and demonstration programs. This paper addresses the opportunities and problems that researchers at the University of Washington, College of Forest Resources have encountered while working in forest sludge applications during the past 20 years.