Use of Water Treatment Residuals to Reduce Soil Phosphorus Loss and Protect Surface Water Quality: an Interregional Study

Drinking water treatment residuals (WTR) are traditionally disposed of in landfills, stored on-site, discharged to streams, or discharged into sanitary sewer systems. Beneficial use options are rapidly becoming more popular. Beneficial use of WTR as phosphorus (P) sorbents to protect surface water quality could provide an economical disposal option for utilities and economic and environmental benefits for communities. The role of P in runoff water from agricultural land in the degradation of surface water has been well documented. Too often, manure or biosolids are land applied based on crop nitrogen (N) requirements resulting in a two to threefold excess P application. Because WTR are rich in amorphous aluminum (Al) or iron (Fe) oxides that are reactive to P, they can be used as a best management practice (BMP) to protect surface water quality by removing dissolved P from agricultural runoff water and decreasing P solubility in manure / biosolids and soil.The objectives of this research project (funded by AWWA Research Foundation as a Tailored Collaboration project) are to (i) evaluate the ability of different WTR types to reduce P loss from agricultural land, (ii) develop tailored recommendations for all participating utilities for use of their WTR, and (iii) calibrate land application of WTR as a BMP.After chemical characterization of all WTR, three land application methods will be investigated. Incorporation of WTR into soil will reduce soil test P by reducing P solubility, decreasing risk of P loss by leaching or runoff from agricultural land. Surface application of WTR will remove dissolved P from agricultural runoff water. Co-application of WTR with manure or biosolids will reduce P solubility in the waste material prior to land application.Participating utilities include Pennsylvania-American Water Company, Tulsa Metropolitan Utility Authority, and Denver Water. Results of this project will provide tailored recommendations to the participating utilities, as well as general guidelines for beneficial use of WTR for all utilities. Specifically, the results of this work will provide information for utilities and regulators of the expected performance of different WTR to serve as a P BMP based on chemical characteristics of the WTR.