Additives

A number of granular amendments have been demonstrated to improve nutrient removal from discharge water in BMPs such as bioretention cells, absorbent landscapes, sand filters or green roofs. There are two primary processes involved, 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.

Soil Additives

Material	Benefits	Potential concerns
Biochar	?	Currently expensive Energy intensive to produce
Bold and GoldTM	Documented Phosphorus removal upto 71%	Proprietary
Iron filings (ZVI)	Proven phosphorus retention	May harm plants	?
Red sand	Proven phosphorus retention	?
Sorptive mediaTM	Documented phosphorus retention	Proprietary]
Water treatment residuals	Waste product reuse	Quality control

Gravel, or crushed stone of various size gradations (i.e., diameter), used in construction; void forming material used as bedding and runoff storage reservoirs and underdrains in stormwater infiltration practices.

Any form of rain or snow.

The attachment of gas, vapour or dissolved matter onto the surface of solid materials.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

Surface runoff from at-grade surfaces, resulting from rain or snowmelt events.