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Copper complexation by dissolved organic matter from surface water and wastewater effluent
Vaishnavi Sarathy1, Herbert E Allen
1Department of Civil and Environmental Engineering, Center for the Study of Metals in the Environment, University of Delaware, 301 DuPont Hall, Newark, DE 19716-3120, USA.
Ecotoxicology and Environmental Safety
|June 1, 2005
Summary
Wastewater organic matter (WWOM) binds copper differently than natural organic matter (NOM). Current models like WHAM poorly predict WWOM copper complexation, suggesting WWOM requires new modeling approaches.
Area of Science:
- Environmental Chemistry
- Water Quality Analysis
- Organic Geochemistry
Background:
- Copper complexation with natural organic matter (NOM) is well-studied.
- Organic matter from wastewater treatment plants (WWOM) has received less attention regarding copper complexation.
- Understanding copper binding is crucial for predicting its environmental fate and toxicity.
Purpose of the Study:
- To investigate and compare copper complexation between WWOM and NOM.
- To evaluate the predictive accuracy of the Windermere Humic Aqueous Model (WHAM) for WWOM.
- To identify potential reasons for discrepancies in copper binding predictions.
Main Methods:
- Acid-base titrations were performed on both NOM and WWOM.
- Copper titrations were conducted on both organic matter types.
- Experimental copper complexation data were compared against WHAM V. VI predictions.
Main Results:
- NOM and WWOM exhibit similar proton binding characteristics.
- WHAM V. VI significantly underpredicted WWOM copper complexation, particularly at low copper concentrations (<10^-6 M).
- Ligand concentrations crucial at low copper levels were approximately 15 times higher in WWOM than predicted.
Conclusions:
- Existing models like WHAM may not accurately represent copper complexation by WWOM.
- The high concentration of specific ligands in WWOM, potentially non-humic substances like biological macromolecules, necessitates alternative modeling approaches.
- WWOM should be considered as a distinct ligand type in environmental models like the Biotic Ligand Model (BLM) for accurate toxicity and speciation predictions.