Electrochemical Processes Coupled to a Biological Treatment for the Removal of Iodinated X-ray Contrast Media Compounds (original) (raw)
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Electrochemical oxidation of iodinated X-ray contrast media by boron-doped diamond electrodes
DESALINATION AND WATER TREATMENT
Iodinated X-ray contrast media (IXCM) represent widespread water pollutants due to their poor elimination by common waste water treatment techniques such as aerobic and anaerobic biodegradation. In this study, we demonstrate the removal of six IXCM (iotalamic acid, iopamidol, iohexol, iopromide, iomeprol, diatrizoate) by electrochemical treatment with boron-doped diamond electrodes. Experiments were performed with model solutions and field water samples. Electrochemical treatment of IXCM in synthetic solution resulted in complete deiodination and generation of the oxidation product iodate. We observed a DOC decrease of 30 to 80% in IXCM solutions, indicating partial mineralisation. Electrochemical IXCM degradation followed pseudo first-order kinetics. In experiments with surface water and effluent from a waste water treatment plant, successful degradation of IXCM was achieved despite the high DOC background. These results demonstrate that electrochemical treatment is a promising method for iodinated X-ray contrast media removal. Further studies into biodegradation of transformation products are recommended.
Degradation of X-ray contrast media diatrizoate in different water matrices by gamma irradiation
Journal of Chemical Technology & Biotechnology, 2013
BACKGROUND: This study analyzes the effectiveness of gamma irradiation in removing diatrizoate contrast from different water matrices: ultrapure water, surface water, groundwater and wastewater. The use of gamma irradiation for degradation is influenced by coexisting substances in natural waters and wastewaters. The influence of the presence of anions Cl − , NO − 2 , NO − 3 , SO 2− 4 and CO 2− 3 /HCO − 3 on the degradation of diatrizoate by gamma irradiation was investigated. RESULTS: Study results indicate that: (1) diatrizoate radiolysis fits pseudo-first-order kinetics; removal of 91.9% of the diatrizoate was achieved at a dose of 1000 Gy; (2) diatrizoate degradation depends on the type of water matrix, with the radiolysis being affected by the presence of anions, as follows: (i) high concentrations of Cl − increase the efficacy of the process; and (ii) low concentrations of NO − 2 markedly decrease the degradation rate, because nitrite ions act as scavengers of e − aq , hydroxyl radical and hydrogen radical; (3) TOC values showed that diatrizoate does not mineralize at a dose of 1000 Gy. CONCLUSIONS: Radiolysis degrades diatrizoate by more than 90%; results obtained indicate that it is not mineralized, with TOC values remaining constant in all waters studied.
Journal of Environmental Science and Health, Part A, 2001
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 mg 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 mg iodine/L was observed in groundwater recharge systems after travel times of 8 to 10 years. Beside 1633 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.
Fate and occurrence of X-ray contrast media in the environment
Analytical and Bioanalytical Chemistry, 2007
Interest in the presence of pharmaceuticals in the environment has recently increased. Despite continuous research efforts there is still a large gap in our knowledge of their fate and effects on the ecosystem. This review covers current information on the occurrence of iodinated X-ray contrast media (ICM) in the environment and developments in the analysis of these highly polar organic micropollutants in aqueous environmental samples. Findings from monitoring surveys conducted on wastewater-treatment plants (WWTP), surface waters, and drinking waters are compiled, and strategies for removal of the compounds in WWTP and waterworks using advanced treatment are reported. Characteristics and advantages of different compound-specific or element-specific mass spectrometric techniques used to monitor ICM in the environment are compared, and applications in elucidation of the structures of biotransformation products, generated in laboratory-scale experiments that simulate sewage treatment or river water/ sediment systems, are described.
Analytical and Bioanalytical Chemistry, 2009
Potentiostatic-controlled electrochemical reduction of iomeprol was used to deiodinate iomeprol (IMP), a representative of the iodinated X-ray contrast media. The reduction process was followed by product analysis with liquid chromatography-electrospray ionization-tandem mass spectrometry and ion chromatography-inductively coupled plasma-mass spectrometry. The identification is mainly based on the interpretation of the mass fragmentation. The product analysis showed a rather selective deiodination process with the successive occurrence of IMP-I, IMP-2I, IMP-3I, and a transformation product (TP), respectively. The TP was formed from IMP-3I by a further cleavage of an amide bond and release of a (C = O)CHOH group from the side chain of IMP. The iodine mass balance on the basis of IMP and iodide showed a gap of about 26% at the beginning of the electrolysis process which could be completely closed by taking the intermediates IMP-I and IMP-2I into consideration. This means that the major intermediates and the TPs were considered and that the reduction process is a rather selective one to remove organically bound iodine from X-ray contrast media. An attractive application area would be the electrochemical deiodination of X-ray contrast media in urine of patients or hospital effluents.
Chemical Engineering & Technology
CIP waters from X-ray contrast material production are currently incinerated, thereby causing considerable disposal costs. As a more economically feasible alternative to incineration, a two-stage nanofiltration process was designed which yields a permeate with concentrations below the legal limit and reduces the remaining volume for incineration to approx. 5 %. In membrane screening and module experiments, rejection of contrast media was greater than 99 % at transmembrane pressures of 20±40 bar and resulting fluxes of up to 200 L/(m 2 h). Required membrane areas for both stages, design considerations and cost estimations are given. As adsorption appeared to cause a significant resistance to both solvent and solute flux, parameters of an extended solution-diffusion model were fitted to account for this physical effect.
Degradation of medical X-ray film developing wastewaters by advanced oxidation processes
Water Research, 2001
Abstract}Effluents from X-ray film developing processes feature high contaminant load (COD about 200 g/l). Identification of the main organics present in these wastewaters was performed by using liquid chromatography-mass spectrometry in electron impact mode, LC-(EI)MS. Both, unconsumed ingredients and sulphonated/hydroxylated derivatives and dimers yielded from the developing agents hydroquinone and phenidone were found to be the main organics contributing to the contaminant load of these effluents. Their potential degradation by oxidation with both photo-and thermal-Fenton reactions was investigated and the optimal degradation conditions were determined. Under these conditions the initial COD was reduced by about 97% within 6 h of treatment. The intermediates detected by LC-(EI)MS in the oxidation of hydroquinone and phenidone during the treatment were essentially hydroxylated derivatives and dimers and the residual organic matter was mainly made up of carboxylic acids. Reaction pathways for the oxidation of the developing agents hydroquinone and phenidone were proposed. The presence of many organic and inorganic components in the wastewaters did not affected the favoured oxidation route of these developers. The results obtained allow to assess the reduction of costs permitted in the treatment of X-ray effluents with the photo-and thermal-Fenton reaction without affecting the degradation degree and quality of the discharge. #
Applied Microbiology and Biotechnology, 2003
Hexachlorobenzene (HCB), pentachlorobenzene (QCB), all three isomers of tetrachlorobenzene (TeCB), 1,2,3-trichlorobenzene (1,2,3-TCB), and 1,2,4-TCB were reductively dechlorinated by enrichment cultures in the presence of lactate, glucose, ethanol, or isopropanol as the electron donor. The enrichment cultures originated from percolation columns filled with Rhine River sediment in which dechlorination of TCBs and dichlorobenzenes (DCBs) occurred. A stable consortium obtained by transfer on lactate as the energy and carbon source in the presence of 1,2,3-TCB dechlorinated this isomer stoichiometrically to 1,3-DCB. Dechlorinating activity could only be maintained when an electron donor was added. Lactate, ethanol, and hydrogen appeared to be the best substrates. Optimal temperature and pH for dechlorination were 30°C and 7.2, respectively. The specificity of the enrichment on lactate and 1,2,3-TCB was tested after approximately 60 transfers (after 2.5 years). HCB and QCB were stoichiometrically dechlorinated to 1,3,5-TCB and minor amounts of 1,2,4-TCB. 1,3,5-TCB was the sole product formed from 1,2,3,5-TeCB, while 1,2,3,4-TeCB and 1,2,4,5-TeCB were converted to 1,2,4-TCB. 1,2,4-TCB, 1,3,5-TCB, and the three isomers of DCB were not dechlorinated during 4 weeks of incubation. For further enrichment of the 1,2,3-TCB-dechlorinating bacteria, a two-liquid-phase (hexadecane-water) system was used with hydrogen as the electron donor and 1,2,3-TCB or CO2 as the electron acceptor. Methanogens and acetogens were the major substrate-competing (H2-CO2) microorganisms in the two-liquid-phase system. Inhibition of methanogenesis by 2-bromoethanesulfonic acid did not influence dechlorination, and acetogens which were isolated from the enrichment culture did not have dechlorinating activity. These results indicated that bacteria were present which used 1,2,3-TCB as the terminal electron acceptor. Although dechlorination was found in dilutions as low as 10-8 from the two-liquid-phase system, attempts to isolate a bacterium in pure culture able to use 1,2,3-TCB as the terminal electron acceptor failed. Chlorinated benzenes are widely used as solvents, intermediates, odorizers, insect repellents, and fungicides. Therefore, they became almost ubiquitous pollutants in surface waters, groundwater, sediments, soils, and sewage (32, 34, 40, 49). In the absence of light, biodegradation is the only possible means of transforming these chemically stable chloroaromatics into harmless compounds. Aerobic mineralization is well documented for chlorobenzenes with up to four chlorine substituents in microcosms and by pure cultures (6, 18, 26, 33, 37, 39, 43, 48). Bacteria described in these studies used chlorobenzenes as the sole energy and carbon source. Reports on anaerobic biotransformation of chlorobenzenes are very scarce. Laboratory studies with sediment columns, biofilm reactors, and batch cultures inoculated with sewage sludge or aquifer material revealed that chlorobenzenes are biologically transformed by reductive dechlorination (4, 14, 15, 19, 25, 30). In most cases, a stoichiometric conversion to less-chlorinated isomers, but no mineralization, was observed. One exception is the 14C02 production from 14C-monochlorobenzene (MCB) in batch