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 microg 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 microg 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.

Degradation of Aqueous Pharmaceuticals by Ozonation and Advanced Oxidation Processes: A Review

“…However, a large number of recent studies have demonstrated persistence of these pharmaceuticals in the aquatic environment. The occurrence of several pharmaceutical compounds have been reported in sewage treatment plant effluents as well as in surface waters in Germany (Ternes, 1998;Hirsch et al, 1999;Putschew et al, 2000), the Netherlands (Belfroid et al, 1999), Switzerland (Soulet et al, 2002), Canada Miao et al, 2004), Brazil , Italy (Castiglioni et al, 2004), Spain (Rodrı´guez et al, 2003), and the United States (Drewes et al, 2001; Kolpin et al, 2002). The detected compounds included antibiotics, anticonvulsants, painkillers, cytostatic drugs, hormones, lipid regulators, beta-blockers, antihistamines, and X-ray contrast media.…”

“…In addition, the removal of triiodinated X-ray contrast media by sorption is poor due to their high hydrophilicity. These contrast agents are excreted with no marked metabolic transformation and contribute to the increase of absorbable organic halogens (AOX) in hospital wastewater (Gartiser et al, 1996), as well as high concentration of absorbable organic iodine (AOI) in sewage treatment plant effluent (5 to 40 mg I/L) (Drewes et al, 2001), surface water and raw drinking water (11 to 13 mg I/L) (Putschew et al, 2000). Although it has been suggested that no environmental risk is evident based on a battery of acute and chronic toxicity test data of triiodinated X-ray contrast media (Steger-Hartmann et al, 1999), their relatively high environmental concentrations, persistence, mobility, as well as the lack of information regarding potential sub-lethal effects have generated interests in the application of advanced water and wastewater treatment processes including ozonation and AOPs.…”

“…Triiodinated benzene derivatives are widely used for this purpose because of their high water solubility and biologically inert (i.e., stable) nature. However, these biologically stable compounds are also proven highly resistant to biodegradation and thus persistent in the aquatic environment (Ternes and Hirsch, 2000;Drewes et al, 2001). In addition, the removal of triiodinated X-ray contrast media by sorption is poor due to their high hydrophilicity.…”

“…As a result, they have been found in some sewage treatment plant effluents as well as in surface water and groundwater in many countries (Ternes, 1998;Sacher et al, 2001; Soulet et al, 2002;Miao et al, 2004). In addition, non-therapeutic medical agents such as X-ray contrast agents (also known as radiocontrasts) and some veterinary drugs have been also found in the aquatic environment (Ternes and Hirsch, 2000;Drewes et al, 2001;Ku¨mmerer, 2001). Although some of these pharmaceuticals and their metabolites can be partially removed through sorption and biotic or abiotic degradation in the environment, they can eventually reach drinking water sources.…”

“…Some unused, surplus, or expired drugs may be disposed into toilets, although this kind of practice is not recommended nowadays. Wastewater from the hospitals may be treated separately or combined with municipal wastewater and then treated at sewage treatment plants.Some of the pharmaceuticals and (human) metabolites in wastewater are degraded completely or partially, giving rise to a mixture of parent compounds and a variety of microbial metabolites (Ternes, 1998;Drewes et al, 2001;Miao et al, 2002;Soulet et al, 2002;Jones et al, 2005b). Some pharmaceuticals such as ibuprofen and bezafibrate are relatively biodegradable, while others such as carbamazepine and diazepam are practically non-biodegradable (Larsen et al, 2004).…”