Advanced Bioretention Systems: Results from Four Years of Mesocosm Studies and Two Years of Field Studies

William C. Lucas and Margaret Greenway


This presentation is a follow up to our mesocosm studies on advanced bioretention systems (ABS) designs that substantially improve removal of nitrogen (N) and phosphorus (P) from runoff. These findings are now being confirmed in field and pilot scale studies in WA, VA, DE, NJ, and MD, as well as Singapore and Shenzhen, PRC. Another year of mesocosm research will also be presented, with novel findings about processes involved in P retention.

The WA studies comprise the most rigorous and extensive experimental bioretention studies ever conducted. Completed in November 2010, initial results showed that the high compost media had considerable losses of N and P, even when inflow runoff concentrations were negligible. While this may highlight potential drawbacks from the compost used in current media recipes, results will be presented on how these systems responded when runoff was applied at higher concentrations after the systems had become well established.

The DE facility treats 20 acres of agricultural and urban runoff in a full scale facility. It will have been established for over two years, with most the first year’s data obtained. The VA facilities comprise a bioretention cell treating half an acre of parking, plus a planter trench system for ultra-urban retrofits. These systems will have been established for over a year as well. The NJ system will have been established for almost 3 years, thus representing a fully mature facility. Currently in the design phase, the MD system is designed to remove nutrients found at much higher concentrations in agricultural runoff.

The Shenzhen University system comprises three bioretention cells, all of which utilize the ABS outlet system. The experiment uses spiked roof runoff applied to three different media. Constructed in late 2012, results from the initial year of the observations will be presented. The Singapore system comprises a facility treating 12 acres of agricultural runoff at prodigious rainfall depths (10 feet per year). As in case of the MD system, it is designed to remove nutrients found at much higher concentrations in agricultural runoff. If obtained, initial results from this facility will also be presented.

The current paradigm in nutrient management urgently needs scientifically valid observations to improve current technologies. Taken together, this array of experimental facilities represents a capital installation and monitoring budget well into 7 figures. Such depth of research in so many different settings is essential if nutrient removal technologies are to mature to the point at which they can be deployed effectively. This research aims to address these objectives.

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