Use of Water Treatment Residuals as a Best Management Practice to Bind P in Upland and Wetland Ecosystems.
Jeff Novak1, Ariel A. Szogi2, Don Watts1, Nicholas Basta3, Elizabeth Dayton1, and Thecan Caesar4. (1) USDA-ARS, Coastal Plains Soil, Water and Plant Research Center, 2611 W Lucas St., Florence, SC 29501-1242, (2) USDA-ARS Coastal Plain Soil, Water and Plant Research Center, 2611 W. Lucas St., Florence, SC 29501, (3) The Ohio State Univ, 2021 Coffey Road, Columbus, OH 43210-1085, (4) USDA-ARS-NPARL, 1500 N Central Ave., Sidney, MT 59270
Phosphorus (P) is an essential nutrient for terrestrial and aquatic plants; however, when transported into surface water systems in excess, it deteriorates water quality. Phosphorus can be transported via erosion, runoff and leaching into ground and surface water systems. Phosphorus movement into water systems can be reduced through the use of nutrient management strategies. Nutrient Best Management Practices (BMPs), such as grass buffer strips, riparian zones, wetlands and soil amendments have been used to varying degrees of success. While most of the BMPs currently use physical processes to reduce sediment-bound P and runoff enriched with P, novel strategies involving the addition/application of agricultural or municipal byproducts are being developed and refined. One such byproduct is drinking Water Treatment Residuals (WTR), a by-product produced from the flocculation/sedimentation process during drinking water purification of ground and surface water sources. Water treatment municipalities commonly add flocculants such as alum [Al2(SO4)3], polymers, or Fe salts to raw water to settle out impurities. Consequently, these residuals contain insoluble Al and Fe oxides and hydroxides which have a high propensity to sorb P relative to unamended soils. Water treatment residual additions to soils can increase their P sorption capacity, reduce extractable P concentrations, reduce runoff P losses, and decrease water column P concentrations in wetland ecosystems. Although, recent laboratory reports have shown the favorable uses of some byproducts, questions about potential risks from trace element contaminants and soil fertility imbalances may limit approval at state or county regulatory levels. Specifically, byproduct concerns include unanswered technical questions such as byproduct P sorption variability, application rates, treatment efficiency, mode of application, and availability, prevent the water treatment professionals to invest in the WTR-recycle technology. Field research is also needed to show the risk and benefits to soil fertility, soil biology, plant production, and the environment when byproducts are used on land or near wetland systems. The purpose of this presentation is to demonstrate how WTRs can serve as a BMP to lower extractable P concentration in soils and manures treated with WTRs, to reduce runoff P losses, and to enhance P sorption in constructed wetlands used to treat animal waste. This presentation will: 1) examine strategies for determining WTRs land application rates to achieve target P reductions, and 2) determine potential release of associate elements from the WTRs that could causes plant nutrient imbalances and/or create conditions unfavorable for plant/microbial growth.