Demonstration Bio Media for Ultra-urban Stormwater Treatment

In ultra-urban areas, there is limited aboveground space for stormwater facilities. Limited space to build both roadways and stormwater facilities results in excessively high construction costs. To complete a roadway, frequently selected are alternate roadway corridors to keep construction cost within budget. One technique used by transportation engineers to construct roadways and stormwater facilities in ultra-urban areas with limited space is to build underground facilities and use a highly effective sorption material called BAM (Biosorption Activated Media) to trap pollutants. The information in this report addresses the life expectancy of the media for nutrient removal as well as a documentation of the chemical and biological mechanisms for removal. The form of BAM used is BOLD & GOLDTM. Laboratory experimentation shows that the probable causes for nitrogen and phosphorus removal are sorption and precipitation. In addition, removal of nitrogen occurs biologically if converted to gas in the form of nitrate. Researchers conducted experiments using BAM in underground detention facilities in ultra-urban environments. Two general filtration options were used, namely an on-line filter and an off-line filter. The authors monitored full-scale operating filters for the removal of total and dissolved nutrients as well as for copper and zinc. The results of the nutrient and metal monitoring showed the filters operated as designed, if regularly maintained. For maintenance purposes, keep the filters clear of solids that cause filtration rate to decrease and replace the media when it is exhausted. The authors present an example problem that shows how to calculate the volume of media needed to achieve the frequency of replacement required for regulatory certification.