Effect of Water Treatment Residuals on Phosphorus in Soils and Leachate

Phosphorus enrichment of lakes, streams and estuaries by surface and subsurface runoff from agricultural land has been implicated as a major cause of the degradation of water quality in the U.S. (Correll, 1998). One possible approach to the problem of reducing P losses from agricultural land is the establishment of vegetative buffer strips between the pollutant source areas and receiving waters. However, the ability of buffer strips to continue to be sinks for pollutants, particularly P, over long periods of time is suspect. For example, Richardson (1985) reported that wetland soils treated with wastewater became saturated with P within a few years and then began to export P. Therefore, increasing the capacity of buffer strips to act as sinks for P, either by removing P from the strip, or by enhancing the strip's ability to adsorb P from runoff water, will greatly affect the ability of these buffer strips to improve water quality in the long run. By using plants that effectively remove P from soil and water, and by amending buffer strips with materials with a high P sorption capacity, the ability of buffer strips to remove P from runoff water over longer periods of time can be increased.One such method of increasing the ability of buffer strips to act as long-term sinks for P is the addition of materials that have a high P sorption capacity, such as drinking water treatment residuals (WTRs). Water treatment residuals have been shown to be effective at decreasing soluble P in soils and in reducing P concentrations in runoff and leachate (Bugbee and Frink, 1985; Heil and Barbarick, 1989; Peters and Basta, 1996; Cox et al., 1997; Butkus et al., 1998; Eaton and Sims, 1999; Gallimore et al., 1999; Ippolito et al., 1999; Basta et al., 2000; Codling et al., 2000; Haustein et al., 2000; Hyde and Morris, 2000). By amending buffer strips with these materials, the concentrations of soluble P and the P sorption capacity of soils in the buffer is increased. This can increase the capacity of buffers to remove P from runoff and leaching waters and reduce the risk of nonpoint P pollution of surface and shallow ground waters. Our objectives were to determine the effectiveness of two types of WTRs (drinking water and industrial) as soil amendments for buffer strips and, in particular, to assess the effects of WTRs on P leaching. The effects of WTRs on soil P and other soil properties that can impact plant growth and the environment were also evaluated.