Category: Stormwater Symposium
Georgian Court comprises a full-scale (3,900 sq. ft.) side by side research facility treating 12 acres of parking lot and institutional land uses. Constructed in in 2015, this facility compared a second-generation advanced bioretention system (ABS) facility to three different subsurface gravel wetlands (SGWs) designed for N removal. The original U. New Hampshire (UNH) SGW design was compared to two NJDEP systems designed for New Jersey’s Barnegat Bay program. One was 2 feet deep (NJDEP2) and one 3 feet deep (NJDEP3). All systems removed NH4 and ON, with the ABS showing the greatest reductions of 62% and 50%, respectively. This demonstrates the high nitrification and ON hydrolysis rates of the ABS system. Due to the resultant NO3 production compared to very low influent concentrations, NO3 was exported from the ABS, while the NJDEP SGWs retained NO3. The poor NO3 removal by the UNH system was unexpected. As a result, the UNH facility did not remove TN, compared to removals of 36% by NJDEP2, 29% by NJDEP3, and 33% by the ABS. It is likely that system malfunctions reduces SGW effectiveness.
Given the improved media formulation, P removal by the ABS was very effective. The mean PO4-P concentration was always below the detection limit of 5 μg/L, removing 73% even at very low influent concentrations. In contrast, the UNH system exported substantial PO4-P, while the NJDEP systems had minimal removal. Dissolved organic P (DOP) removal by the ABS was 86%, while the SGWs had removal trends similar to that observed for PO4-P. TP removal by the ABS was 84%, with a mean concentration of 11 μg/L. IN contrast, the SGWs had retained considerably less P, with higher discharge concentrations. The UNH system exported P. Since each SGW had the same constituents, this disparity between them for P is unexpected.
William Lucas– Principal, Environmental Engineering, Green Earth Operations, Malvern, Pennsylvania