OCCURRENCE OF IODINATED X-RAY CONTRAST MEDIA IN DOMESTIC EFFLUENTS AND THEIR FATE DURING INDIRECT POTABLE REUSE

Abstract

This study investigated the occurrence of pharmaceuticals, emphasizing triiodinated benzene derivatives used as X-ray contrast media, in domestic effluents and their fate during subsequent groundwater recharge. Organic iodine measurements were used as a surrogate for triiodinated benzene derivatives. Seven wastewater treatment facilities in Texas, Arizona and California were studied and organic iodine concentrations at these facilities varied between 5 and 40 μg iodine/L. The highest concentrations were observed on weekdays reflecting the common practice of employing X-ray examinations between Monday and Friday. Organic iodine compounds in secondary treated effluents were not removed by advanced wastewater treatment using ozone. However, organic iodine was efficiently removed by reverse osmosis membrane treatment. Based on laboratory biodegradation experiments and field studies negligible removal occurred under aerobic redox conditions while anoxic conditions led to partial removal of organic iodine. However, a concentration range of 8–15 μg iodine/L was observed in groundwater recharge systems after travel times of 8 to 10 years. Beside appropriate redox conditions, bioavailable organic carbon seems to be a key factor for organic iodine biodegradation in the environment. No environmental risk is expected from the parent compounds of triiodinated contrast media, however, toxicological effects associated with the metabolites are unknown.

Keywords:

• Groundwater recharge
• Indirect potable reuse
• Pharmaceuticals
• Wastewater treatment
• X-ray contrast agents

ACKNOWLEDGMENTS

The authors gratefully acknowledge the technical support they received from the cities of Houston, Phoenix, Mesa, Scottsdale, Pima County, the County Sanitation Districts of Los Angeles County, and the Berliner Wasser Betriebe. The authors thank Dr. Anke Putschew and Hella Schmeisser for conducting the AOI analysis.

Partial funding for this research project was provided by the German Ministry for Research and Education and the Berliner Wasser Betriebe (BMBF 02WA9253/4). Additional funding for this project was provided by the City of Mesa, the City of Phoenix, the City of Scottsdale, the City of Tempe, the City of Glendale, Tucson Water, County Sanitation Districts of Los Angeles County, the AWWA Research Foundation (AWWARF), and the U.S. Environmental Protection Agency (EPA). The funding agencies assume no responsibility for the content of the research reported in this publication or for the opinions or statements of fact expressed.