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Session Chair: Richard Boyle, Clean Water Services;
3:00pm - 3:45pm
Removal Efficiencies, Uptake Mechanisms, and Competitive Effects of Copper and Zinc in Various Stormwater Filter Media
Portland State University, United States of America;
Polluted stormwater, if not treated, can compromise water quality throughout our hydrologic cycle, adversely affecting aquatic ecosystems. Common stormwater pollutants, copper and zinc, have been identified as primary toxicants in multiple freshwater and marine environments. For small-scale generators, stormwater management can be cumbersome and implementation of common BMPs impractical thus catch basins are popular though not the most environmentally conscious and sustainable option. This study aims to characterize the potential of a mobile media filter operation for the treatment and on-site recycling of catch basin stormwater. The removal capacities of various commercially available filter media (e.g., a common perlite; Earthlite™, a medium largely composed of biochars; and Filter33™, a proprietary porous medium) were measured using binary injection solutions modeled after local catch basin stormwater characteristics. The results of filtration experiments, rapid small-scale column tests (RSSCTs), indicate that the transport of metals in Perlite is primarily impacted by nonspecific sorption whereas in Earthlite™ and Filter33™ both nonspecific and specific sorption are present. For all media and experimentation, there was a consistent preferential uptake of copper such that copper displayed delayed arrival and/or greater removal than zinc. Moreover, the observed snow plow effects and concentration plateaus in Earthlite™ and Filter33™ RSSCTs suggest rate limited ion exchange and specific sorption in addition to ion competition. Earthlite™ exhibited an approach velocity dependent removal efficiency in the RSSCTs and pseudo second-order uptake behavior for zinc in kinetic batch experiments. At the lab-scale equivalent of the proposed field-scale flow rate, Filter33™ displayed the greatest average zinc removal of 8.6 mg/g. In all, this research indicates that test parameters (i.e., pH, competitive ions solutions, empty bed contact time, flow rate) based on the natural environment and field scale operation can greatly impact removal efficiency in filter media.
3:45pm - 4:30pm
Remediating Stormwater: Effects of a Bioretention Swale on Coliforms and Metals
Lacy R. Lackey
Washington State University; Whatcom Community College;
Lower Fever Creek in Bellingham, WA (a tributary of Bellingham Bay) is listed as Category 5 under 303(d) of the Clean Water Act by Washington State Water Quality Assessment for zinc, coliform bacteria, and dissolved oxygen concentrations. The City of Bellingham Public Works Department installed a bioretention swale in an effort to remediate the urban stormwater runoff entering Lower Fever Creek for metals concentrations and suspended solids. This project evaluates the effectiveness of the bioretention swale for its remediation of zinc, copper, lead, and coliform bacteria.
We determined concentrations of the analytes before the installation of the bioretention swale at three different flow rates. We quantified zinc, copper and lead by ICP-MS, and quantified coliform bacteria by membrane filtration. After the swale was installed, we determined concentrations of the analytes directly upstream and downstream of the swale, by the same methods.
Results from before the swale’s installation indicated that concentrations of the analytes (copper, zinc, and coliforms) increased with the flow rate of the discharge. Lead concentrations were not quantifiable.
Soon after the swale's installation, results indicated that zinc concentrations decreased after passing through the swale, coliform concentrations decreased, copper concentrations increased, and lead concentrations were not quantifiable.
In a high flow event when stormwater discharge overtopped the spillway, coliform concentrations decreased after passing through the swale, and zinc and copper concentrations were not significantly affected by passing through the swale.
Results indicated possible matrix effects in the stormwater discharge. After these were quantified, results – from samples taken in spring – indicated that the concentrations of both copper and zinc were lower after passing through the swale.
In all, the swale's treatment of zinc and coliform concentrations was consistently effective, except in very high flow events. Early on, copper concentrations discharging from the swale were higher than concentrations feeding into the swale. From autumn to spring, the swale's treatment of copper concentrations improved, such that copper concentrations were lower after passing through the swale. The swale's effects on lead concentrations were not quantifiable.
4:30pm - 5:15pm
Investigation Of Oregon Native Plants For Remediation Of Trace Metals and Organic Pollutants in Stormwater
Richard Hilliard, Tyler Radniecki
Oregon State Univeristy, United States of America;
Stormwater collects dissolved and particulate phase pollutants from improved surfaces and carries these to receiving water bodies, degrading their quality. Pollutants of concern include heavy metals, trace organics, sediments, and nutrients. Infiltration systems of various designs are increasingly being used to provide passive treatment of these waters. Inclusion of plants in these systems provides potential for phytoremediation, prevention of erosion, increased soil porosity, and an aesthetic quality against the built environment. However, plants and their associate microbes vary greatly in their abilities to provide additional degradation and removal of stormwater pollutants. In this study, 20 native Oregon plants were investigated for potential treatment of Cu2+, Zn2+, PCBs, PAHs, and PFASs in surface runoff collected from a public works utility site. Treatment was evaluated by final concentrations of constituents in plant roots and shoots compared with the accumulation in the soil phase and total removal was calculated with mass balances on the treated water. Enrichment of plant microbiomes in the rhizosphere and the bulk soil was evaluated by metagenomic profiling of 16SrRNA, mono-, and di-oxygenase genes.