A simple method for the measurement of organic iodine in wastewater and surface water

Total adsorbable organic iodine (TAOI) has been used as a surrogate parameter for X-ray contrast media in municipal wastewater. Available methods require specialized equipment for pyrolyzing these compounds to convert the covalently bound iodine into iodide, which is then measured by ion chromatography. In this study we describe a simple method for liberating iodide from these compounds with Cu(II) and hydrogen peroxide. Concentrations of TAOI were measured in wastewater effluent, surface waters that were expected to be impacted by wastewater, and unimpacted surface waters. TAOI concentrations ranged between 1.9 and 16.3 microg/L I in wastewater with a median of 6.5 microg/L I. The lowest TAOI concentrations consistently were detected in a wastewater treatment plant that apparently had few hospitals within its collection area. In comparison, TAOI concentrations in surface water that was unimpacted by sewage were between 0.3 and 3.5 microg/L I. TAOI concentrations in surface waters that were impacted by sewage were consistent with the expected conservative behavior of TAOI.