Changes

Design innovations to improve water quality treatment performance of filter media mixtures involve the incorporation of additives to enhance retention of reactive or dissolved pollutants.  A number of granular amendments have been demonstrated to improve nutrient removal from discharge water in BMPs such as [[bioretention]] systems, [[stormwater planters]], [[absorbent landscapes]], [[sand filters]] or [[green roofs]].  

Design innovations to improve water quality treatment performance of filter media mixtures involve the incorporation of additives to enhance retention of reactive or dissolved pollutants.  A number of granular amendments have been demonstrated to improve nutrient removal from discharge water in BMPs such as [[bioretention]] systems, [[stormwater planters]], [[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. Determining when additive enhanced filter media needs replacing or maintenance represents a new challenge for stormwater asset managers, as there are no suitable visual indicators.  Erickson et al. (2018) suggest effluent sampling and laboratory testing to identify when enhanced filter media pollutant retention is waning, or periodic sampling and batch (laboratory) testing of filter media to directly measure its capacity to retain the targeted pollutants.<ref>Erickson, A.J., Taguchi, V.J., Gulliver, J.S. 2018. The Challenge of Maintaining Stormwater Control Measures: A Synthesis of Recent Research and Practitioner Experience. Sustainability. 2018, 10, 3666. https://www.mdpi.com/2071-1050/10/10/3666 </ref>

There are two primary processes involved, chemical precipitation and adsorption. Both mechanisms are ultimately finite, but have been shown in some cases to make significant improvements on the discharged water quality over several years. For instance, a two year STEP research study that compared standard bioretention media, to the same media amended with Sorbtive™ in one plot and iron enriched sand (aka red sand) in another showed statistically significant improvements in effluent phosphorus concentrations from the two media amended plots (STEP, 2019)<ref>STEP. 2019. Improving nutrient retention in bioretention. Technical Brief. Accessed: https://sustainabletechnologies.ca/app/uploads/2019/06/improving-nutrient-retention-in-bioretention-tech-brief.pdf</ref>.

 

Determining when additive enhanced filter media needs replacing or maintenance represents a new challenge for stormwater asset managers, as there are no suitable visual indicators.  Erickson et al. (2018) suggest effluent sampling and laboratory testing to identify when enhanced filter media pollutant retention is waning, or periodic sampling and batch (laboratory) testing of filter media to directly measure its capacity to retain the targeted pollutants<ref>Erickson, A.J., Taguchi, V.J., Gulliver, J.S. 2018. The Challenge of Maintaining Stormwater Control Measures: A Synthesis of Recent Research and Practitioner Experience. Sustainability. 2018, 10, 3666. https://www.mdpi.com/2071-1050/10/10/3666 </ref>. Periodic replacement of filter media at inlet locations should be considered as an operation and maintenance best practice to maintain treatment performance.

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