Adsorptive-Filtration of Runoff Subject to Controlled and Uncontrolled Hydraulic and Water Chemistry Loadings

Field-based adsorptive-filtration (A-F) for metals, phosphorus (P), and particulate matter (PM) transported in urban runoff has advanced over the last decade. Testing, modeling, and monitoring of media to provide secondary/tertiary treatment has been coupled with primary clarification to provide flow and chemistry equalization, enhancing sustainability for engineered A-F media otherwise subject to transient loadings. As a result, A-F media is now deployed through disparate substrates that range from alumino-silicates, recycled residuals, clays, engineered concrete, sands, and organic or polymeric materials. Each of these substrates when combined with oxides of Al, Fe, Mn, Si, or combinations thereof, provides a range of A-F behavior. Examination of this behavior (equilibrium, kinetics, breakthrough, leaching) is carried out under controlled lab conditions before field testing. Results of a Cincinnati paired A-F system with Fe-oxide and porous concrete are illustrated. This paired application of linear exfiltration demonstrated that water chemistry management in the system was responsible for the success of one paired half of the system for the A-F of metals; while a lack of management was responsible for failure of the other paired half. A radial A-F system in Baton Rouge with Al-oxide showed the benefits of hydraulic controls for A-F of P and PM. A radial A-F system in Gainesville with Al-oxide examined the management of P at higher loadings without hydraulic control. The role of primary treatment before A-F is to provide attenuation of transients; system design, management and maintenance, and inter-event partitioning is critical, albeit unique for metals, P and N.