Additives
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A number of granular amendments have been demonstrated to improve nutrient removal from discharge water in BMPs such as bioretention systems, absorbent landscapes, sand filters or green roofs. There are two primary processes involved, chemical precipitation and adsorption. Both mechanisms are ultimately finite, but have been shown in come cases to make significant improvements on the discharged water quality over several years.
| Material | Benefits | Potential concerns |
|---|---|---|
| Biochar | Renewable Enhances soil aggregation, water holding capacity and organic carbon content |
Currently expensive Energy intensive to produce Some sources say ineffective for phosphorus removal |
| Bold & GoldTM | Documented total phosphorus removal of up to 71%[1] | Proprietary |
| Fly ash | Ref [2] | |
| Iron filings (ZVI) | Proven phosphorus retention Retained phosphorus is stable |
May harm plants[3] Removal efficiency declines with increased concentration of incoming phosphorus |
| Red sand | Proven phosphorus removal Also removes TSS |
Poor orthophosphate removal in hypoxic or anoxic conditions |
| Smart SpongeTM | Removes phosphorus, as well as TSS, fecal coliform bacteria and heavy metals Non-leaching |
1-3 year lifespan, after which the product is removed as solid waste Proprietary |
| Sorbtive mediaTM | High phosphorus removal efficiency | Proprietary |
| Water treatment residuals | Waste product reuse | Quality control (capabilities depend on source, treatment methods, storage time, etc of WTR) |
- ↑ Hood A, Chopra M, Wanielista M. Assessment of Biosorption Activated Media Under Roadside Swales for the Removal of Phosphorus from Stormwater. Water. 2013;5(1):53-66. doi:10.3390/w5010053.
- ↑ http://rgvstormwater.org/wp-content/uploads/2016/09/Fly-Ash-Brown.pdf
- ↑ Logsdon SD, Sauer PA. Iron Filings Cement Engineered Soil Mix. Agron J. 2016;108(4):1753. doi:10.2134/agronj2015.0427.