A report on the collaborative project of three water utilities (Pennsylvania American Water Company , Tulsa Metropolitan Utility Authority, and Denver Water) looking at managing water treatment residuals (WTRs) generated by drinking water treatment facilities. The goal is to exploit the unique characteristics of WTR for beneficial use, specifically to improve phosphorus management of agricultural lands by controlling the release of phosphorus.
Phosphorus in surface runoff from agricultural lands is often implicated in the degradation of surface water quality. Many states are developing soil phosphorus application limits. Utilities must develop and implement new best management practices (BMPs) to control phosphorous. The objective of this project was to investigate the beneficial use of water treatment residuals (WTRs) to control non-point source (NPS) phosphorus pollution and protect surface water quality. Specifically, the researchers planned to examine the unique chemical characteristics of WTRs, namely the large concentration of aluminum and iron hyrdroxides, to combine them with phosphorus in high phosphorus soils, biosolids, and manures to reduce the likelihood of phosphorus release to aquatic environments. Several types of WTRs were selected and characterized based on the coagulant used (aluminum and iron based) and their form - dewatered or liquid. The research developed valuable new insight for the beneficial use of WTRs and demonstrated WTRs' potential as a BMP for phosphorus control in surface runoff from agricultural lands and for protecting surface water quality. In particular, the potential role of WTRs in Phosphorous Index programs was confirmed. Future research and full-scale demonstrations are needed to confirm the potential of land applied WTRs as a BMP for phosphorus control in runoff from agricultural lands. Land application of WTRs within a utility?s source water watershed, while subject to local and state regulations, can be implemented as part of an overall watershed protection program.
Incorporation of Al-WTR to a depth of 10 cm decreased SP concentrations in subsurface flow and leachate by 37 and 11%, respectively. However, with incorporation of Al-WTR to a depth of 20 cm, both subsurface flow and leachate SP concentrations were reduced by approximately 90%. The incorporated Al-WTR reduced soil water-extractable P (WEP) by approximately 70%. However, Mehlich-1 P concentrations were not affected by the incorporation of Al-WTR in the soil. Care must be taken to ensure complete incorporation of Al-WTR throughout the P-impacted layer, as Al-WTR is only effective in reducing SP concentrations when it is in contact with the impacted soil. Shoot and root growth of stargrass were not adversely affected by the Al-WTR applied at a rate of 2.5% of soil weight.
This research report presents the results of a study to determine both the longlasting effects of a single WTR-biosolids co-application (applied in 1991) and the short-term impacts of a repeated WTR-biosolids co-application (applied in 2002) on native rangeland soil phosphorus dynamics. This report covers from the time of application (1991 or 2002) along with changes between sampling periods, with field soil sampling occurring in October 2003 and October 2004. Specifically looked at were quantify changes in inorganic soil P associated with a single or repeated WTR-biosolids co-application and identify which inorganic P phase dominates using a sequential extraction technique along with same for organic soil P.
Excess nutrient loading to the Great Lakes Basin from agricultural runoff has negatively impacted water quality, resulting in harmful algal blooms. Best management practices, including constructed wetlands and sedimentation basins, can be used to reduce phosphorus losses from agricultural fields. Constructed wetlands are efficient in the removal of particulate phosphorus; however, removal of dissolved phosphorus is limited and requires further treatment to improve surface water quality. Several types of filter media (composed of Ca, Fe, and/or Al) can be used to further reduce the amount of dissolved phosphorus that enters surface water, and a media consisting of low-cost waste residual would be beneficial to adoption. Drinking water treatment residuals (DWTR) that often contain Al could be reused as an adsorbent for dissolved phosphorus. We evaluated the use of modified drinking water treatment residuals for removing dissolved phosphorus from wastewater. DWTR were mixed with binders, made into pellets to create an insoluble media with mechanical strength, and pyrolyzed to create a reactive media pellet. Pellets were evaluated using flow through columns and included experiments to determine the impact of pH (i.e. 6, 8, and 10), retention time (i.e. 1, 5, and 10 min), and field-collected agricultural runoff on dissolved P removal. Cement was found to be the best binding material to create an insoluble pellet with mechanical strength. The P removal capacity of the pellet consisting of the cement binder (1,397 mg P/kg) was within the range of previously evaluated steel slag (120-10,210 mg P/kg), a common reactive media for P removal. The addition of drinking water treatment residual and metals decreased the P removal capacity of the cement binder at pH 6-1 min retention at exhaustion. Increasing retention time increased the P removal capacity of the filter media tested. Wastewater pH has a minimal impact on the P removal capacity of all media except the pyrolyzed DWTR + cement binder media. Evaluated media was negatively impacted by real agricultural runoff with a measured decrease in P removal capacity (43-146 mg/kg decrease) compared to P-spiked distilled water at the same retention time. The pyrolyzed cement pellet was the most cost-effective reactive media, due to an increased P removal capacity. Pyrolyzed DWTR + cement binder would be more costly than the pyrolyzed cement binder alone but could provide a solution for the disposal of DWTR.
