PH16 Metals in the Environment: Chemistry and Fate Issues
Exhibit Hall
8:00 AM - Thursday, 13 November 2003
(PH157) Are Ligands in Wastewater Effluent Like Those in Natural Organic Matter?
Cheng, T1, Sarathy, V1, Allen, H1, 1 University of Delaware, Newark, Delaware, USA
ABSTRACT- Metal complexation by wastewater treatment plant (WWTP) effluents is important in understanding bioavailability and potential metal toxicity. Models such as WHAM or BLM do not independently consider WWTP organic matter from that of natural organic matter (NOM). We characterized organic matter from surface waters and a wastewater treatment plant and studied their copper and zinc complexing properties using ion-selective electrode potentiometry and square wave anodic stripping voltammetry (SWASV). NOM and organic matter from WWTP have ligands with similar binding constants, but the metal binding of WWTP effluents is not well predicted by WHAM especially at low metal concentrations (below 10-6 M). Experimental data also showed that the concentration of strong ligands at low metal concentrations was about 15 times higher for the WWTP DOM than for the DOM sampled from the Edisto River, South Carolina. This could be due to the presence of sulfide in wastewater effluents that binds strongly to metal, which is not considered by WHAM. However the consideration of sulfide alone does not fully explain the deviation of experimental data from WHAM predictions. Non-humic ligands that probably come from proteins and other biological macromolecules, which account for the strong metal binding, may also be present.
Key words: copper, complexation, zinc, wastewater