Speciation, Equilibria and Kinetics for Rainfall-Runoff Metals in Adsorptive-Filtration Unit Operations and Processes

Populations transferred by rainfall runoff can have many adverse effects livings and people. Treatment of rainfall-runoff continues to pose unique challenges due to the unsteady nature of processes including mobilization, partitioning and transport of heavy metals as well as other constituent loads. BMPs that incorporate heavy metal removal are generating more attention as the nature of stormwater is better understood. This dissertation focused on metal partitioning and speciation in rainfall-runoff through the in-situ Partial Exfiltration Reactor (PER) and exposed to various redox circumstances, and metal removal by sorptive engineered manganese oxides coated media. Adsorption capacity of three manganese oxides coated media for Cu, Cd, Pb, and Zn was evaluated through isotherm study. Adsorption kinetics was investigated respect to various pH and hydraulic loading. In-situ control PER illustrated outstanding removal capability for dissolved and particulate-bound Zn, Cu, Cd, and Pb. Hydrology of rainfall runoff influenced metal partitioning. Metal speciation was changed by the PER with respect to DOM species decrease and carbonate species increase. Metal carbonate species were the dominant under aerobic condition. Cu+, Cd(HS)2, Pb(HS)2, and ZnS were the dominant species in negative redox condition. In adsorption study, Freundlich type adsorption isotherms were observed in metal adsorption study on manganese oxides coated media In terms of adsorption capacity and pH in equilibrium solutions, MOKB was the best media among three manganese oxide coated media (MOPM, MOCM and MOKB). The metal adsorption capacity onto manganese oxides coated media followed the trend of Pb \u3e Cu \u3e Cd \u3e Zn. Effect of pH on metals adsorption onto MOPM was the most pronounced, and then was followed by MOKB and MOCM. This trend is consistent with the reverse order of their PZC (PZCMOPM \u3c PZCMOKB \u3c PZCMOCM). Kinetics study indicated that potential driving model fit experimental data excellently. Result inferred that under typical rainfall runoff pH (6-8) level and possible applied EBCT (30-120sec.) in fixed-bed filtration with MOKB media, metals adsorption removal rate may keep constant and stable