USING WATER TREATMENT RESIDUALS TO REDUCE RUNOFF P ENTERING URBAN WATERS

A 3 acre pond, with a large population of over-wintering geese, has become a nuisance in an affluent neighborhood. For a period of time the geese have been the blame for the buildup of algae and aquatic weeds in the pond. A runoff study was conducted to propose a solution to the problem. The objective of this study was to reduce the runoff P concentration entering the pond using water treatment residuals (WTR), thus lowering P risk scores. A larger but similar lake was used for the rainfall simulations. Runoff was collected in an area where geese were fed corn for the purpose of having fresh manure for the study. The runoff was found to have less than 0.5 ppm of soluble P. Although this is considered to be a eutrophic runoff P concentration for small terminal water bodies, larger bodies of water with a constant through-flow of water can handle a larger concentration of P in the runoff. Runoff from residential land contains P from commercial fertilizer rather than animal manure. Diammonium Phosphate (DAP) fertilizer was applied to runoff plots at a rate of 180 kg ha−11. The runoff P concentration was 386 ppm. WTR from the OSU water treatment plant was applied as a buffer strip at rates of 0, 25, 60, and 100 Mg ha−1. The resulting decrease in soluble P in the runoff was 0, 30, 37, and 44 percent, respectively. A curve linear fit (r2= 0.84) was found to be the best estimation for predicting the application rates of the OSU WTR.