Water treatment residuals
From LID SWM Planning and Design Guide
What is it?Water Treatment Residuals (WTR) are primarily sedimentSoil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls., metal (alumunium, iron, or calcium) oxide/hydroxides, activated carbon, and lime removed from raw water during the water purification process. The effectiveness of WTR in reducing soluble phosphorus depends on several factors, including source water characteristics, water treatment methods, and length of residual storage time prior to land application. Different water treatment facilities create different physical and chemical compositions and phosphorus sorption capability of WTR.
How is it being used?
No projects have been found in Ontario to date.
BenefitsPast research done on the efficiency of the use of WTR for phosphorus reduction is promising. Laboratory studies have shown that WTRs adsorb large amounts of phosphorus and increase the phosphorus-sorbing capacity of soils. This decreases phosphorus losses in runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. and leaching. Surface application of WTRs showed an 88% reduction in runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. and leachate dissolved phosphorous. Agyin-Birikorang et. al. also state that phosphorous sorption by aluminum-based WTRs is practically irreversible.  Results from another study state that WTR can be used for phosphorous removal in engineered wetlands and it carries the benefits of reuse of a by-product that promotes sustainability.  It is estimated that the phosphorous adsorptive capacity of amended bioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation. filter media, which was mixed with 4% of WTR, was 4 times as high as the traditional media under the same conditions. 
- Agyin-Birikorang S, O’Connor G, Obreza T. Drinking Water Treatment Residuals to Control Phosphorus in Soils. UF/IFAS Extension. 2016.
- Babatunde AO, Zhao YQ, Burke AM, Morris MA, Hanrahan JP. Characterization of aluminum-based water treatment residual for potential phosphorus removal in engineered wetlands. Environmental Pollution 157 (2015) 2830-2836. doi: 10.1016/j.envpol.2009.04.016
- Wang JJ, Li T, Zhang Y. Water treatment residual as a bioretention media amendment for phosphorus removal. Huan Jing ke xue: Huanjing kexue 12:35 (2014) 4642-4647.