Ozonation and reductive deiodination of iopromide to reduce the environmental burden of iodinated X-ray contrast media.

The potential of ozonation for the removal of iodinated X-ray contrast media (ICM) with focus on the oxidation products was examined. Iopromide used as model compound was dissolved in tap water, respectively in the effluent of a membrane bioreactor and was ozonated. Ozone (10 mg/L) was continuously introduced into a semi-batch reactor (35 L/h). After 30 minutes the ozone concentration was increased to 30 mg/L. In all experiments the iopromide concentration decreased very fast, whereas the decrease of the amount of organic bound iodine (AOI) was much lower. The concentration of iodate, the inorganic oxidation product increases with time, depending on the AOI decrease. The data clearly show that the ozonation of iopromide using a common applied ozone dosage leads to the formation of numerous iodinated transformation products, which are detectable by LC-ESI-MS. As an alternative treatment, especially for the treatment of urine or hospital waste water, the source for the contamination, it was tested if iopromide can be deiodinated by zero-valent iron. First experiments done in stirred batch reactors using iopromide dissolved in ultra pure water and urine with an initial pH of 2 showed that iopromide can be deiodinated completely by zero-valent iron. Even in contaminated urine collected in a hospital a deiodination of ICM was possible. Kinetic studies at constant pH showed that the deiodination can be described by pseudo-first order for equal iopromide and iron concentrations. The observed rate constant kobs increased with decreasing pH with a maximum at pH 3 with 4.76x10(-4) s(-1). The concentration of iopromide can be decreased by ozonation and by the reductive dehalogenation. In case of ozonation iodinated organic compounds are the main reaction products, whereas the reductive dehalogenation leads to transformation products which are not iodinated and are thus most probable biodegradable.     

臭氧技术在污水处理中的应用

臭氧作为一种强氧化剂,主要用于污水的深度处理。本文介绍了臭氧氧化的机理,探讨了臭氧及臭氧高级氧化在污水深度处理以及降解痕量有机物方面的应用,并在此基础上对今后的研究方向进行了展望,提出如何避免副产物的产生将是今后的研究重点。     

SUVA as control parameter for the effective ozonation of organic pollutants in secondary effluent.

Recent research projects have shown a good suitability of the ozonation process to transform trace concentrations of most pharmaceuticals in wastewater treatment plant (WWTP) effluents. The concentrations of carbamazepine and 17 alpha-ethinylestradiol, for instance, were reduced below their detection limits by use of ozone dosages resulting in a specific ozone consumption of 0.5 mg O3/mg DOC0. At the same time a good disinfection performance was achieved. The given hygienic requirements of the EU bathing water directive (e.g. 2,000 N/100 mL faecal coliforms) are fulfilled without the formation of bromate (<10 microg/L). As technical control parameter of the ozonation process usually the residual ozone in the liquid phase or in the off-gas are used. However, at very low specific ozone consumptions, ozone reacts instantaneously with dissolved compounds and cannot be detected. Hence, alternative parameters should be used for effective operation control. The present paper evaluates the relation between UVA decrease and the removal of different compounds (endocrine disrupting compounds, pharmaceuticals, iodinated X-ray contrast media), microbial parameters and bromate formation. The results can be used as a guideline for the control of the oxidation performance at large scale ozonation units.     

AOPs with ozone and UV radiation in drinking water: contaminants removal and effects on disinfection byproducts formation.

In this study, the advanced oxidation with ozone and UV radiation (with two low pressure UV lamps, at 254 and 185 nm wavelength) were experimented on a surface water in order to study the removal of two odorous compounds (geosmin and 2-methylisoborneol) and a pesticide (metolachlor), the influence on organic compounds (UV absorbance and THM precursors) and bromate formation. Different batch tests were performed with ozone concentration up to 10 mg/L, UV dose up to 14,000 J/m2 and a maximum contact time of 10 minutes. The main results show that metolachlor can be efficiently removed with ozone alone while for geosmin and MIB a complete removal can be obtained with the advanced oxidation of ozone (with concentration of 1.5-3 mg/L and contact time of 2-3 minutes) with UV radiation (with doses of 5,000-6,000 J/m2). As concerns the influence on the organic precursors, all the experimented processes show a medium removal of about 20-40% for UV absorbance and 15-30% for THMFP (trihalomethanes formation potential). As concerns bromate formation, the advanced oxidation of ozone/UV 254 nm shows a bromate formation that is about 40% lower with respect to conventional oxidation with ozone.     

A kinetic study of enhancing effect by phenolic compounds on the hydroxyl radical generation during ozonation.

Ozone decomposition in aqueous solution proceeds through a radical type chain mechanism. These reactions involve the very reactive and catalytic intermediates O2- radical, OH radical, HO2 radical, OH-, H2O2, etc. OH radical is proposed as an important factor in the ozonation of water among them. In the present study, the enhancing effects of several phenolic compounds; phenol, 2-, 3-, 4-monochloro, 2,4-dichloro, 2,4,6-trichlorophenol on OH radical generation were mathematically evaluated using the electron spin resonance (ESR)/spin-trapping technique. OH radical was trapped with a 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a stable adduct, DMPO-OH. The initial velocities of DMPO-OH generation in ozonated water containing phenolic compounds were quantitatively measured using a combined system of ESR spectroscopy with stopped-flow apparatus, which was controlled by homemade software. The initial velocities of DMPO-OH generation increased as a function of the ozone concentration. The relation among ozone concentration, amount of phenolic compounds and the initial velocity (v0) of DMPO-OH generation was mathematically analyzed and the following equation was obtained, v0 (10(-6) M/s) = (A' x [PhOHs (10(-9) M)] + 0.0005) exp (60 x [ozone (10(-9) M)]). The equation fitted very well with the experimental results, and the correlation coefficient was larger than 0.98.     

Removal of geosmin and 2-methylisoborneol by biological filtration.

The quality of drinking water is sometimes diminished by the presence of certain compounds that can impart particular tastes or odours. One of the most common and problematic types of taste and odour is the earthy/musty odour produced by geosmin (trans-1, 10-dimethyl-trans-9-decalol) and MIB (2-methylisoborneol). Taste and odour treatment processes including powdered activated carbon, and oxidation using chlorine, chloramines, potassium permanganate, and sometimes even ozone are largely ineffective for reducing these compounds to below their odour threshold concentration levels. Ozonation followed by biological filtration, however, has the potential to provide effective treatment. Ozone provides partial removal of geosmin and MIB but also creates other compounds more amenable to biodegradation and potentially undesirable biological instability. Subsequent biofiltration can remove residual geosmin and MIB in addition to removing these other biodegradable compounds. Bench scale experiments were conducted using two parallel filter columns containing fresh and exhausted granular activated carbon (GAC) media and sand. Source water consisted of dechlorinated tap water to which geosmin and MIB were added, as well as, a cocktail of easily biodegradable organic matter (i.e. typical ozonation by-products) in order to simulate water that had been subjected to ozonation prior to filtration. Using fresh GAC, total removals of geosmin ranged from 76 to 100% and total MIB removals ranged from 47% to 100%. The exhausted GAC initially removed less geosmin and MIB but removals increased over time. Overall the results of these experiments are encouraging for the use of biofiltration following ozonation as a means of geosmin and MIB removal. These results provide important information with respect to the role biofilters play during their startup phase in the reduction of these particular compounds. In addition, the results demonstrate the potential biofilters have in responding to transient geosmin and MIB episodes.     

Effects and mechanism of ozonation for degradation of sodium acetate in aqueous solution

The degradation efficiencies and mechanism of ozonation for the degradation of sodium acetate in aqueous solution were investigated under atmospheric pressure at room temperature (293 K). The effects of the initial pH value, reaction time, and concentrations of HCO3-, CO32-, CaCl2, and Ca(OH)2 on the removal rate of chemical oxygen demand (COD) were studied. The results indicated that ozonation obviously improved the degradation rate of sodium acetate when the pH value of the solution was not less than 8.5. A suitable long reaction time may be helpful in increasing the COD removal rate, and a removal rate of 36.36% can be obtained after a 30-minute treatment. The COD removal rate increased firstly and decreased subsequently with the increase of the HCO3- concentration (from 0 to 200 mg/L), and under the same experimental condition it reached the optimum 34.66% at the HCO3- concentration of 100 mg/L. The COD removal rate was 5.26% lower when the concentration of was 200 mg/L than when there was no HCO3-. The COD removal rate decreased by 15.68% when the CO32- concentration increased from 0 to CO32- 200 mg/L. has a more obvious scavenging effect in inhibiting the formation of hydroxyl radicals than HCO3-. CaCl2 and Ca(OH)2 could increase the degradation efficiency of sodium acetate greatly, and the COD removal rates reached 65.73% and 83.46%, respectively, after a 30-minute treatment, 29.37% and 47.10% higher, respectively, than with single ozone oxidation. It was proved that the degradation of sodium acetate in the ozonation process followed the mechanism of oxidization with hydroxyl free radicals (·OH).     

Oxidative processes for olive mill wastewater treatment.

The present work describes an experimental study carried out in order to investigate the efficiency and feasibility of physical (lime coagulation) and advanced oxidation processes (Ozone and Fenton's process) for olive oil mill wastewater treatment. Particular attention was paid to the degradation of both organic and phenolic compounds. Lime coagulation reaches maximum removal at a pH of 12, with a TP (total polyphenols) and COD reduction of 37 and 26%, respectively. Ozone oxidation is also pH-dependent, showing the higher removal efficiency (91% for TP and 19% for COD) with an initial pH value of 12. Experimental results show a lower efficiency of Fenton's process than ozone in TP removal, reaching a maximum value of 60%. Oxidation trials carried out on gallic and p-coumaric synthetic solutions confirmed ozone and Fenton's efficiency at degrading phenolic compounds. Biological trials, both aerobic and anaerobic, highlighted a significant increase of biodegradability of treated OMW samples if compared to the untreated ones. Respirometric tests showed an increase in BOD of about 20% and anaerobic batch tests provided a methane production up to eight times higher.     

The effect of the textile industry dye bath additive EDTMPA on colour removal characteristics by ozone oxidation.

In this study, the effects of the phosphonic acid based sequestering agent EDTMPA used in the textile dye baths on colour and organic matter removal by ozone oxidation was experimentally investigated. Procion Navy HEXL dyestuff that has been commonly used for the reactive dyeing of cellulose fibers was selected as the model component. The organic matter oxidation by ozone was determined to obey the pseudo-first order kinetics as they are treated singly or in combination. COD removal rates obtained from pseudo-first order reaction kinetics showed that oxidation of Navy HEXL alone (0.0947 L/min) was faster than that of EDTMPA (0.0171 L/min) and EDTMPA with dye (0.0155 L/min) at pH 3.0. It was also found that reaction rates of single EDTMPA removal and EDTMPA and dye mixture removal increased as the reaction pH was increased from 3.0 to 10.5.     

Ozonation parameter for removal of oestrogenicity from secondary effluent without by-products.

The purposes of this study are to investigate ozonation characteristics, to evaluate oestrogenicity and to confirm behaviours of by-products during ozonation of secondary effluent. For the ozonation of secondary effluent, TOC was decreased only 10% when 4 (mgO3/mgC) of ozone consumption per initial TOC. However, UV254 and SUVA was decreased approximately 65% until ozone consumption of 2 (mgO3/mgC). Ozonation was also shown to be very effective for decrease of oestrogenicity in secondary effluent. Bromate ion started to form obviously when the ozone consumption per initial TOC exceeded 2 (mgO3/mgC) and increased while the time of ozonation became longer. From these results, ozone consumption per initial TOC was shown to be an appropriate operation parameter to reduce SUVA effectively and E2 equivalent concentration to less than 0.1 nM without significant formation of bromate ion, and its value was determined to be 2 (mgO3/mgC) in ozonation of secondary effluent.     

Advanced treatment of benzothiazole contaminated waters: comparison of O3, AC, and O3/AC processes.

Benzothiazole (BT) is a toxic and poorly biodegradable contaminant, usually found in wastewater from rubber related applications. This compound could be effectively eliminated using advanced treatment processes. This paper compares experimental results on detoxification systems based on ozone oxidation, activated carbon adsorption, and simultaneous adsorption-oxidation using ozone in the presence of activated carbon. The effect of pH (2-11), and the presence of radical scavengers (tert-butyl alcohol and sodium carbonate) on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1 L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with activated carbon adsorption increases the overall BT oxidation rate with respect to the ozonation process and activated carbon adsorption. In the presence of free radical scavenger, only a 44% reduction in BT removal rate is observed in the simultaneous treatment, as compared with 72% when ozonation treatment is used, suggesting that BT oxidation reactions mainly take place on the activated carbon surface.     

臭氧氧化工艺溴酸盐控制中试研究

通过1m3/h的中试装置研究了臭氧氧化工艺处理引黄水库水时溴酸盐控制技术。结果表明,在臭氧投加量为1.5mg/L时,臭氧氧化后溴酸盐产生量为0.006mg/L,活性炭过滤出水溴酸盐为0.002mg/L;在相同臭氧投加量条件下,降低原水pH、投加高锰酸钾和过氧化氢后溴酸盐生成量分别减少了50%、33%和100%,活性炭后出水中均未检出溴酸盐,同时提高了有机物去除率。     

Contribution of brominated organic disinfection by-products to the mutagenicity of drinking water.

The activity inducing chromosomal aberrations of the mixture of brominated disinfection by-products (DBPs) was approximately three times higher than that of the chlorinated counterparts for the same hypohalous acid dose. With the combination of chromosomal aberration test and a new analytical technique to differentiate total organic chlorine (TOCl) and total organic bromine (TOBr), it was found that TOBr was correlated to the mutagenicity of chlorinated waters. It was also implied that for a bromide-to-TOC ratio of 0.1 (mg/mg C), brominated DBPs could account for at least 29% of the total toxicity of DBPs formed during chlorination. On the other hand, bromate ion, a major ozonation DBP, was not a major contributor to the activity inducing chromosomal aberrations of the water treated with an ozone/chlorine sequential process. Therefore, ozonation is one possible option to reduce the health risk caused by DBPs even in the presence of bromide.     

臭氧在饮用水处理中的应用

阐述臭氧在水处理中的氧化消毒机理,其强氧化性能破坏了有机物的分子结构,将一部分有机物彻底分解,同时将大分子有机物生成小分子有机物,改变了有机物性质,提高了其可生化性。介绍臭氧在水处理中的应用,如预氧化对微污染水中有机物、无机物、藻类及颗粒物的去除,以及对饮用水消毒杀菌。     

硅酸锌催化臭氧氧化净水效能连续流实验研究

以实验室制备的硅酸锌为催化剂,考察了在连续流实验中催化臭氧氧化对滤后水水质的影响。结果表明,与单独臭氧氧化相比,在相同实验条件下,硅酸锌的存在能够提高水体中的臭氧浓度。硅酸锌催化臭氧氧化对滤后水的总有机碳(TOC)和天然有机物的去除效果均好于单独臭氧氧化。连续运行10 h,硅酸锌催化臭氧氧化系统中TOC的去除效果稳定,并且Zn2+的溶出非常少。生物可同化性有机碳(assimilable organic carbon,AOC)的测定结果表明,经过硅酸锌催化臭氧化处理后,滤后水中的大分子有机物所占比例明显降低,小分子有机物含量增高。GC-MS分析结果表明,单独臭氧氧化可使滤后水中有机物的种类从41种减少到27种;而硅酸锌催化臭氧化效果明显优于单独臭氧氧化可以使水中有机物种类减少到21种。     

活性炭去除饮用水中溴酸盐的研究进展

臭氧氧化过程中产生的溴酸盐的问题已经成为目前臭氧大规模应用于饮用水中的最大制约因素。活性炭去除法是国内外最常用的去除溴酸盐的方法,且由于活性炭常作为臭氧氧化工艺必备的联用工艺,容易实现生产应用,且不需要增加额外的投资,引起了研究者的极大关注。本文全面阐述了关于活性炭／生物活性炭对溴酸盐的去除效能、去除机理及影响因素的研究进展。针对活性炭去除饮用水中溴酸盐的研究现状,提出了今后研究的主要方向和亟需解决的问题。     

Ozone-based reclamation of an STP effluent

The system ozone and hydrogen peroxide was used to reclaim wastewater from the secondary clarifier from a Sewage Treatment Plant (STP) of Alcalá de Henares (Madrid-Spain). The assays were performed by bubbling a gas mixture of oxygen and ozone, with approximately 24 g Nm(-3) of ozone concentration, through a volume of wastewater samples for 20 minutes at 25 degrees C. The removal of dissolved micropollutants such as Pharmaceutical and Personal Care Products (PPCPs) and Organic Carbon (TOC) was enhanced by adding periodic pulses of hydrogen peroxide while keeping pH above 8.0 throughout the runs. Removal efficiency ratios in the range of 7-26 mg O3/mg TOC and 0.24 mg O3/ng micropollutants at 5 minutes of ozonation were assessed as reference data to reclaim wastewater from STP. The relation between the extent of TOC removed and ozone doses used was related by a second-order kinetic model in which the time-integrated ozone-hydrogen peroxide concentration was included.     

Ozone catalysed with solids as an advanced oxidation process for landfill leachate treatment.

Heterogeneous catalytic ozonation (HCO) of wastewater is gaining both research and industrial interests. It is proved to be an advanced oxidation process since it involves hydroxyl radicals as oxidation species. Few studies have been carried out to test HCO in the treatment of landfill leachates. This work has been carried out to test three types of catalysts: activated carbon (AC), expanded perlite (EP) and titanium dioxide (TiO2) combined with ozone at 80 g/m3 gas concentration for the treatment of a leachate generated by Jebel Chakir landfill site near Tunis-capital of Tunisia. The work has shown a reduction in COD of about 45% and an increase in biodegradability (BOD5/COD) from 0.1 to 0.34. A catalyst concentration of 0.7 g/L was found optimal for the treatment of the leachate.     

The occurrence of micopollutants in the aquatic environment: a new challenge for water management.

The occurrence of micropollutants in the aquatic environment has become a crucial topic in the last two decades owing to the innovative development of analytical instrumentation such as LC tandem MS. Using these new techniques it became obvious that pesticides, pharmaceuticals, ingredients of personal care products, biocides, flame retardants, and perfluorinated compounds are entering rivers and streams via treated wastewater. Also contamination of bank filtrates, groundwater and in a few cases even drinking water was identified. Wastewater treatment plants are not designed to remove polar persistent organic pollutants occurring in the sub-mg/L range and hence many of these organic pollutants are passing WWTPs to a high extent. Waterworks with a potential pesticide contamination in their raw water are equipped with advanced techniques such ozonation, activated carbon or nanofiltration enabling the removal of a high variety of other organic compounds. However, waterworks without an expected pesticide contamination are frequently equipped with common treatment processes not enabling the removal of these kinds of organic pollutants. Therefore, comprehensive management activities for protection of aquatic environments and water resources must consider the removal of all micropollutants relevant to water quality and ecology, independent of their usage or origin.     

Catalyzed ozonation process with GAC and metal doped-GAC for removing organic pollutants.

The purpose of this study was to investigate the catalytic role of granular activated carbon (GAC), and metal (Mn or Fe) doped-GAC, on the transformation of ozone into more reactive secondary radicals, such as hydroxyl radicals (*OH), for the treatment of wastewater. The GAC doped with Mn showed the highest catalytic performance in terms of ozone decomposition into OH radicals. Likewise, activated carbon alone accelerated the ozone decomposition, resulting in the formation of *OH radicals. In the presence of promoters, the ozone depletion rate was enhanced further by the Mn-GAC catalyst system, even under aqueous acidic pH conditions.