Title: Utilizing water treatment residuals to reduce phosphorus runoff from biosolids Authors
Submitted to: Journal of Environmental Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 4, 2013
Publication Date: N/A
Interpretive Summary: Inputs of water-soluble phosphorus (P) into natural water systems can have major detrimental impacts on these ecosystems. The main effect is the acceleration of the eutrophication process which causes algal blooms and the depletion oxygen levels leading to a reduction in aquatic life. Sources of water-soluble P include runoff water from agricultural fields fertilized with organic manures. Recent research has focused on the effect of applied sewage sludges (biosolids) on water-soluble P in runoff water and techniques to reduce these high P levels. Co-application of biosolids with alum-treated water treatment residuals (WTR) are an inexpensive and efficient answer because the WTRs contain aluminum hydroxides (formed as part of the water treatment process) which can bind phosphorus and significantly reduce water-soluble P levels. Runoff water was collected and analyzed for dissolved reactive P (DRP) following rainfall simulations on grassed field plots in 2006 and 2007. The effect of different amendments (alum, ferric chloride, 20%WTR) blended with biosolids were compared with an untreated biosolids application in 2006. The following year, amendments containing 15% and 30% WTRs that had been allowed to incubate for three weeks prior to application were compared to an untreated biosolids control. The total DRP runoff load observed for the 20% WTR treatment was not significantly different from the other chemical treatments and resulted in a 48% reduction in soluble P runoff compared with the untreated application. Dissolved reactive P runoff loads in 2007 for the 15% and 30% WTR treatments resulted in significantly lower soluble P compared to untreated biosolids and led to DRP runoff load reduction of 78% and 85%, respectively. The greater load reduction observed in 2007 indicates that longer storage times may allow for greater P adsorption. Treating biosolids with WTRs will allow for greater land application of biosolids and WTRs and reduce or eliminate the economic costs associated with landfilling and incineration of these two resources.
Technical Abstract: Approximately 40% of biosolids (sewage sludge) produced in the U.S. are incinerated or landfilled rather than land applied due to concern over non-point source phosphorus (P) runoff. The objective of this study was to determine the impact of chemical amendments on water-extractable P (WEP) in applied treatments and dissolved reactive P (DRP) in runoff from biosolids-amended soils. Rainfall simulations were conducted in 2006 on field plots fertilized with biosolids that had been treated with alum [(Al2SO4)3 . 14 H2O], ferric chloride (FeCl3) or an alum-based water treatment residual (WTR) at a rate of 20% (wt/wt) to reduce DRP in runoff. In 2007, rainfall simulations were conducted using WTR/biosolid blends of 15% and 30% (wt/wt) that were allowed to incubate for three weeks prior to application. Cumulative DRP runoff load observed for the 20% WTR treatment was not significantly different from other chemical treatments and resulted in a 45% reduction in DRP runoff as compared to the untreated biosolids application. Cumulative DRP runoff load in 2007 for the 15% and 30% WTR treatments resulted in significantly lower DRP loads compared to untreated biosolids and led to DRP runoff load reductions of 78% and 85% (compared to the untreated biosolids application), respectively.