Low-pressure UV Lamp Research Articles

Photodegradation kinetics of iopamidol by UV irradiation and enhanced formation of iodinated disinfection by-products in sequential oxidation processes

The photochemical degradation of iopamidol with low-pressure UV lamps and the formation of iodinated disinfection by-products (I-DBPs) during sequential oxidation processes including chlorine, monochloramine and chlorine dioxide were investigated in this study. Iopamidol can be effectively decomposed by UV irradiation with pseudo-first order reaction kinetics. The evaluated quantum yield was found to be 0.03318 mol einstein−1. Results showed that iopamidol degradation rate was significantly increased by higher UV intensity and lower initial iopamidol concentration. However, the effect of solution pH was negligible. Degradation of iopamidol by UV photolysis was subjected to deiodination and hydroxylation mechanisms. The main degradation products including –OH substitutes and iodide were identified by UPLC-ESI-MS and UPLC-UV, respectively. Increasing the intensity of UV irradiation promoted the release of iodide. Destruction pathways of iopamidol photolysis were proposed. Enhanced formation of I-DBPs were observed after iopamidol photolysis followed by disinfection processes including chlorine, monochloramine and chlorine dioxide. With the increase of UV fluence, I-DBPs formation were significantly promoted.

Removal of halogenated by-products precursors in photocatalysis process enhanced with membrane filtration

In the article, the results of the research on removal of halogenated by-products precursors in a photocatalysis (PC) process enhanced with membrane filtration have been presented. In the research, the following by-products were analyzed as follows: trihalomethanes (trichloromethane, bromodichloromethane, dibromochloromethane, tribromomethane), haloacetic acids (monochloroacetic acid, monobromoacetic acid, dichloroacetic acid, bromochloroacetic acid, dibromoacetic acid, trichloroacetic acid), haloacetonitriles (bromochloroacetonitrile, dibromoacetonitrile, dichloroacetonitrile, trichloroacetonitrile), haloketones (1,1-dichloro-2-propanone, 1,1,1-trichloro-2-propanone), chloropicrin, and chloral hydrate. The analyses were conducted on the model solutions of humic and fulvic acids and also on the samples of surface water taken from the Goczalkowice Reservoir. These water samples were treated in a sequence of PC and membrane filtration. The PC process was conducted using TiO2 and low-pressure monochromatic UV lamps. The samples of untreated water and the one obtained as a result of those processes were chlorinated with sodium hypochlorite in a dose which resulted in 3–5 mg/L of free chlorine after 24 h. After that time, the formed chlorination by-products were analyzed with gas chromatography, and the formation potential was calculated for each considered group of halogenated organic compounds.

Simultaneous Removal of MTBE and Benzene from Contaminated Groundwater Using Ultraviolet-Based Ozone and Hydrogen Peroxide

Efficiency of ultraviolet-ozone (UV/O3) and ultraviolet-hydrogen peroxide (UV/H2O2) processes was investigated for simultaneous removal of methyl tertiary butyl ether (MTBE) and benzene from contaminated ground water. The photoreactor employed housed 15-watt low pressure (LP) and 150-watt medium pressure (MP) mercury UV lamps. Oxidation of contaminants was studied at two different levels of ozone and hydrogen peroxide. Brackish groundwater samples were spiked with MTBE and benzene up to a concentration of 500 μg L−1. Removal potential was evaluated at different parameters such as UV type and intensity and peroxide and ozone dosages, as well as contact time. Results indicated that no removal of the contaminants was attained when treated with hydrogen peroxide or ozone alone. However, about 50% and 30% removal of MTBE were achieved in 30 minutes when irradiated with MP-UV and LP-UV lamps, respectively. On the other hand, UV/H2O2process was found to be superior in removal of MTBE (90% in 10 min.) and benzene (95% in 5 min.) compared to UV/O3process. Furthermore, removal of benzene was comparatively easier than MTBE in both approaches. It is hence concluded that higher UV intensities and elevated doses of H2O2accelerate simultaneous removal of MTBE and benzene from water.

Inactivation of Viruses by Combination Processes of UV and Chlorine

Adenoviruses, the most UV resistant microorganism currently known, are posing concerns in UV treated drinking water. To reduce the risk from adenovirus infection, combination processes of UV and chlorination are attractive. Bacteriophage MS2 and adenovirus 5 (AdV5) were used in this study, and inactivated by low-pressure UV (LPUV) lamp, chlorination, sequential processes (UV-Cl2 and Cl2-UV) and a simultaneous process (UV/Cl2). MS2 was more resistant against chlorine than AdV5, and CT values for 2 log reduction of MS2 and AdV5 were 0.77 and 0.033 mg-min/L, respectively. However, AdV5 was more resistant to UV than MS2 and required a 101 mJ/cm2 of fluence for 2 log reduction. Compared to the application of UV or chlorine separately, an increasing trend of MS2 inactivation rate was found in the sequential processes, which was statistically significant (p ‹ 0.05, ANCOVA). The simultaneous process of UV/Cl2 for MS2 provided about 2.3 times higher inactivation rate than a summation of inactivation rates by the separate application of either chlorine or UV, even at the same UV fluence rate and the same initial chlorine concentration. The combination processes of UV and chlorine, either sequential or simultaneous application, seemed to be more effective than a standalone process in viral inactivation.

The impact of power supply frequency of a low pressure UV lamp on bacterial viability and activities

We propose in this study to explore the impact of the power supply frequency and the spectral radiant flux emitted by a germicidal UV lamp on the bacterial viability and activities. Two types of power supplies are used, a traditional electromagnetic ballast taken as a reference and electronic ballast allowing modulating frequencies. To evaluate energy emitted in the UV bandwidth, a photometric system composed of an integrating cylinder, a monochromator, and a CCD camera is mounted. The bacterial viability and activities were repressed when we used a high-frequency UV lamp. Accordingly, the regulation of traditional UV lamp at a high frequency supply can provide an enhancement of UV disinfection process and guarantee the safety of treated water, without any environmental and sanitary hazards.

Photocatalytic decolourization of the X3B textile dye in aqueous solutions using iron-rich montmorillonite

Photocatalytic decolourization of textile dye X3B in aqueous solutions was investigated, using iron-rich montmorillonite (MMt, 2·24%Fe2O3) under a 15 W low-pressure UV lamp (λ = 254 nm, I = 48·4 μW/cm2). Hydroxyl radicals (•OH) were detected by tert-butyl alcohol (TBA) in aqueous MMt suspensions under UV irradiation and were found to be responsible for the degradation of X3B. Free iron ions dissolved in MMt suspensions, structural iron in the MMt solid, and the charged surface of nano clay are responsible for hydroxyl radical (•OH) production. Low pH values are favorable for the decolourization of X3B. The •OH concentration increased with increasing aqueous MMt concentrations in the range of 0 – 2·0 g/L; higher concentrations, for example, 5·0 g/L MMt, inhibited the •OH production. The addition of oxalate was favorable for X3B photodegradation in acid-washed MMt suspensions. This study shows that iron-rich MMt is a potential photocatalyst for the treatment of dye wastewater.

Aniline degradation in aqueous solution by UV-aeration and UV-microO3 processes: Efficiency, contribution of radicals and byproducts

The use of combination of air and UV irradiation for organic matters removal has drawn attention since degradation efficiency would be significantly enhanced in the presence of oxygen. Considering the fact that a low-pressure mercury UV lamp (emitting at 254nm and 185nm) could dissociate oxygen in gas phase and generate ozone, UV irradiation with addition of ozone enriched air, generated by the same UV lamp, was introduced. This technology was called UV-microO3 because the concentration of ozone generated by UV irradiation was relatively low (lower than 1mgL−1). The degradation of aniline by UV-aeration and UV-microO3 processes was comparatively analyzed. It was shown that aniline underwent much faster and more complete degradation in UV-microO3 process than in UV-aeration system. Hydroxyl radical (OH) exposure in UV-microO3 process was 2.46times of that in UV-aeration system. Furthermore, increasing inlet air flow rate would be of benefit to maintaining high dissolved oxygen (DO) level in UV-aeration system, thus the aniline removal was improved. While concentration of ozone generated by UV irradiation increased at first and then declined as the air flow rate increased from 1.8Lmin−1 to 4.8Lmin−1 in UV-microO3 process, and similar trend for aniline removal rate was observed. The contributions of radicals on aniline removal in UV-aeration and UV-microO3 processes were calculated to be 23.1% and 67.7%. The formation of 4-aminophenol, 4-Hydroxydiphenylamine, azobenzene and 4-Phenylazophenol was observed as the major intermediates in UV-aeration and UV-microO3 processes, mechanism of aniline degradation was proposed based on experimental evidence.

Oxidative–reductive photodecomposition of perfluorooctanoic acid in water

This article aims to elucidate on usefulness of vacuum ultraviolet (VUV) for photoreductive degradation of perfluorooctanoic acid (PFOA), a representative perfluorinated compound (PFC), in water for the first time. Bench-scale tests were conducted on oxidative and reductive (with aquated electron: e aq − ) mineralization of PFOA using low-pressure UV (LPUV) lamps and potassium iodide. Unlike with 254 nm wavelength (UVC), the reductive mineralization with VUV was very inefficient compared to the corresponding oxidative mineralization. The inefficiency is attributed to low reactivity of e aq − with PFOA and its fluorinated products than that of 185 nm photons. Direct VUV photolysis of PFOA and its products in reductive reaction conditions was not apparent due to a very big difference in reactivity of 185 and 254 nm photons with iodide. The results demonstrated that highly energetic VUV photons are not suitable for photoreductive degradations of PFCs involving e aq − , but they can be best used for oxidative degradations. These findings should serve as an important reference on VUV usage to decompose refractory micropollutants.

PHOTOCATALYTIC DECOLOURIZATION OF TEXTILE EFFLUENT CONTAINING REACTIVE RED 120 DYE WITH UV/TIO<SUB>2</SUB>

The efficiency of degradation of an aqueous solution of reactive red 120 dye using Advanced Oxidation Process (AOP) was evaluated. A low pressure UV lamp and a combination of UV/TiO2 were tested using ten different dye concentrations (50 - 500 mg/L) at several retention times (5.2-60 min) a pH of 10.5. The effect of acidic pH (pH = 3) on dye removal efficiency and the Chemical Oxygen Demand (COD) of the treated effluents were also investigated. When the alkaline (pH = 10.5) reactive red 120 dye solutions were treated using a low pressure (380 nm intensity) UV lamp, a maximum degradation efficiency of 27.01% was obtained for the least concentrated dye (50 mg/L) solution and only a degradation efficiency of 0.33% was obtained for the most concentrated (500 mg/L) dye solution. When the alkaline (pH = 10.5) reactive red 120 solutions were exposed to a combination of UV/TiO2, a maximum degradation efficiency of 46.70% was obtained for the lease concentrated (50 mg/L) dye solution after 60 min and only a degradation efficiency of 2.84% was obtained for the most concentrated (500 mg/L) dye solution after 60 min. When the pH of the reactive red 120 dye solution was reduced to 3, a degradation efficiency of 56.45% was obtained for the least concentrated (50 mg/L) dye solution at 60 min and a degradation efficiency of 14.94% was obtained for the most concentrated (500 mg/L) dye solution at 60 min. However, the increase in degradation efficiency obtained in this study does not justify the cost of chemicals added to adjust the pH to 3 before treatment and then to 7 before final disposal. Also, the addition of chemicals (to adjust the pH) increases the COD of the dye solution thereby necessitating a further costly treatment.

Pilot Plant Results with Three Different Types of UV Lamps for Advanced Oxidation

Three different types of ultraviolet lamps were tested for the advanced oxidation process application on pre-treated surface water in a pilot plant. The pilot setup consisted of three parallel reactors with either medium pressure, low pressure or dielectric barrier discharge UV lamps. Four model compounds (atrazine, bromacil, ibuprofen and N-nitroso-dimethylamine (NDMA)) and 0, 5 or 10 ppm hydrogen peroxide were dosed. Low pressure lamps were shown to have the lowest energy demand, calculated as electrical energy per order, followed by dielectric barrier discharge lamps and then medium pressure lamps. Medium pressure lamps gave the highest formation of genotoxic activity and nitrite formation, whereas no formation of genotoxic activity was observed for either of the other lamp types.

Prediction of advanced oxidation performance in various pilot UV/H2O2 reactor systems with MP- and LP- and DBD-UV lamps

The UV/H2O2 advanced oxidation process is increasingly applied as a barrier against organic micro pollutants in drinking water treatment. Adequate modeling of the purification process, resulting in a reliable prediction of the reactor performance, would make it possible to optimize the operating parameters as a function of seasonal or diurnal fluctuations in the influent composition, and thus save energy while still guaranteeing safe drinking water. We recently developed two design tools to predict full scale performance of UV/H2O2 reactors: the UVPerox I and II models. UVPerox I is based on a kinetic model, describing both photolysis and oxidation. By means of Computational Fluid Dynamics (CFD) calculations of the reactor the UV dose distribution inside the reactor can be calculated, while the kinetic model gives the conversion as a function of the UV dose. UVPerox I is shown to be applicable to reactors equipped with Low Pressure (LP) or Dielectric Barrier Discharge (DBD) UV lamps, using a broad range of organic compounds, resulting in a <5–10% deviation from experimental data for different water matrix compositions. The conversion of micro pollutants as a function of the UV dose can also be experimentally determined, using a collimated beam (CB) set-up. The dose response curves thus obtained can also be directly implemented in the CFD-model of the reactor (UVPerox II). Using several model compounds UVPerox II is shown to be applicable to reactors equipped with three kinds of UV lamps (LP-, MP- UV and DBD lamps), each with its own emission spectrum. The deviation from experimental data was found to be <5–10%, independent of the composition of the water matrix. Both models were applied to several reactor geometries. Good agreement was obtained between both models and the actual conversion data for three types of UV lamps in various pilot reactors and water types.

Elimination of pharmaceutical residues in biologically pre-treated hospital wastewater using advanced UV irradiation technology: A comparative assessment

UV irradiation technology as a membrane bioreactor (MBR) post-treatment was investigated and assessed. Both UV low pressure (LP) and medium pressure (MP) lamps were examined. The technology was installed in a pilot plant treating hospital wastewater to provide the study with adequate field data.The effect of the UV irradiation was enhanced with varying dosages of H2O2 to establish an advanced oxidation process (AOP). The efficiency of the pharmaceutical removal process was assessed by examining 14 micropollutants (antibiotics, analgesics, anticonvulsants, beta-blockers, cytostatics and X-ray contrast media) which are typically released by hospitals and detected with liquid chromatography coupled tandem mass spectrometry (LC–MS/MS).While the MBR treatment generally showed only a low degradation capacity for persistent pharmaceuticals, much better degradation was obtained by applying UV irradiation and H2O2 as AOP. The “conventional” cost-benefit analysis of the different technology options taking into account both electrical energy consumption and pharmaceutical removal efficiency, revealed clearly better performance of low pressure UV lamps as AOP. However, a holistic comparison between the different scenarios was carried out by evaluating their environmental impacts using the life cycle assessment (LCA) methodology. Decisive advantages were highlighted to include this approach in the decision making process.

Transformation of atrazine, carbamazepine, diclofenac and sulfamethoxazole by low and medium pressure UV and UV/H2O2 treatment

Differences in the degradation and transformation of atrazine (ATZ), carbamazepine (CBZ), diclofenac (DCF), and sulfamethoxazole (SMX) in deionized water during UV and UV/H2O2 treatment using low-pressure (LP) and medium pressure (MP) UV lamps, were assessed using a collimated beam apparatus. UV doses ranged from 300–700mJ/cm2 and H2O2 doses ranged from 0–10mg/L. Liquid chromatography with tandem mass spectrometry (LC–MS/MS) was used to measure concentrations of the parent compounds and quadrupole time-of-flight mass spectrometry (QToF-MS) was used to screen for transformation products following treatment. In general, there was little difference in compound degradation and transformation between LP and MP UV lamps in both UV and UV/H2O2 treatments. Removal of ATZ, SMX and DCF was largely attributed to direct photodegradation whereas CBZ was not appreciably removed by UV or UV/H2O2 treatment. All four compounds yielded transformation products following UV or UV/H2O2 treatment with LP and MP lamps. Transformation pathways were determined using accurate mass estimation to determine elemental composition, and relative abundance was determined using ion counts. For ATZ and CBZ, the transformation pathway was non-sequential, whereas for DCF and SMX, the transformation pathway was sequential. The approach outlined in this paper can be used to assess unknown transformation products formed during oxidation of organic micropollutants during water treatment.

Combination of O3/H2O2 and UV for multiple barrier micropollutant treatment and bromate formation control - an economic attractive option

Advanced Oxidation Processes (AOP) are known as an effective treatment barrier for micropollutants. Well known AOP combinations are UV/H2O2 and O3/H2O2. This paper will present a more detailed view on how to use the different options combining UV; ozone and H2O2. The focus of this investigation is on treatment effects (reduction of specific contaminats), water matrix, energy consumption and cost calculation (CAPEX, OPEX). The presented data are extracted from extended pilot trials carried out at DUNEA in 2009 and 2010. Dunea (The Netherlands,The Hague) produces drinking water from the Meuse River, which contains a variety of organic micropollutants as a result from upstream activity. Dunea is performing research to extend the current multiple barrier treatment (e.g. pre-treatment, artificial recharge and recovery (ARR), post-treatment) with an advanced oxidation processes (AOP), situated at the pre-treatment location in Bergambacht, before ARR. The degradation of organic micropollutants as a result of advanced oxidation using different combinations of hydrogen peroxide, ozone, low pressure (LP) UV lamps has been assessed by means of pilot-scale (5 m3/h) experiments. The influent was pre-treated river water, with an yearly average UV-transmission of 80% and a DOC concentration of 4 mg/L.The peroxide doses were varied as 0, 5 and 10 ppm, the ozone doses were varied as 1, 2 and 3 g ozone/m3. The UV doses were varied between 300 and 650 mJ/cm2. The installed power for the LP reactor was 0.26 kWh/m3. Atrazine, bromacil, ibuprofen and NDMA were spiked (10-20 µg/L) and used as model compounds. Bromacil was completely (&amp;gt;99%) removed by ozone/peroxide. Atrazine and ibuprofen were good (58% and 85% respectively) removed by O3/H2O2 and NDMA was not (9%) removed by this technique, whereas NDMA showed good (82%) removal by UV/H2O2. Atrazine, bromacil and ibuprofen were degraded by UV/H2O2 at 53, 46 and 59 %, respectively. In addition also combined AOP was tested; spiked water was treated by O3/H2O2 first and let over the LP-UV reactor directly afterwards. All four compounds showed highest degradation during combined AOP treatment. With this combined AOP, lower ozone dose and lower UV dose result in comparable degradation compared to single AOP treatment. For all these techniques a detailed capital expenditure operational expenditure (CAPEX / OPEX) evaluation was carried out based on a daily water flow of 240,000 m3/d. This evaluation resulted in the finding, that the combined AOP is the most economical solution with the best treatment result. Other advantages of the combined AOP are limited by-product formation, especially bromate, and a future barrier against OMPs encompassing a broad spectrum of properties.

Factors influencing UV photodecomposition of perfluorooctanoic acid in water

With the view of their importance in photochemical reactions, impacts of five selected parameters (UV wavelength/transmission, perfluorooctanoic acid (PFOA) concentration, dissolved oxygen (DO), solution pH and water quality) on PFOA photodecomposition in water were investigated for the first time in our knowledge. Laboratory batch tests using a glass reactor (1.5 L), a low pressure UV (LPUV) lamp (20 W) and two types of lamp sleeves were carried out. Ultrapure water (UPW), tap water and urban river water were used in “water quality effect” tests, while UPW was used in all other tests. UV wavelength and transmission showed profound impacts on PFOA photodecomposition. The compound was more easily decomposed by vacuum UV (VUV: 185 nm) than by UVC (254 nm). No visible impact of PFOA concentration (0.12–2.42 μM) on its elimination ratio was observed. The inverse correlation observed between defluorination ratio and PFOA concentration was attributed to UV photon-limited condition for larger PFOA concentrations combined with stepwise photodecomposition of PFOA. DO in reaction solution had negative impact on PFOA elimination, while abundant DO in solution was detrimental for its photomineralization. Though no clear-cut impact of solution pH (3.0–10.0) on PFOA photomineralization was observed, pH 3.0 was relatively better. Water quality also profoundly impacted PFOA photomineralization. Organic constituents and bicarbonates were directly and indirectly responsible for drastic decrease in PFOA photomineralization in organic-rich waters. These findings may serve as basic information for photodecomposition of similar other perfluorinated compounds (PFCs).

Growth and Repair Potential of Three Species of Bacteria in Reclaimed Wastewater after UV Disinfection

Objective The growth and repair potential of three typical microorganisms in reclaimed water after UV disinfection was investigated to assess the effects of photo-reactivation and dark repair of microorganisms, and the microbial safety of reclaimed water following this procedure. Methods The growth and repair potential of Escherichia coli, a fecal coliform strain and Bacillus subtilis in the effluent of a biological wastewater treatment plant disinfected by a low-pressure UV lamp were investigated. Results Any increase in bacterial numbers in the effluent after UV disinfection was due to damage repair. Exposure to photo-reactivating light for 8-10 h after UV irradiation with a dose of 5 mJ/cm 2, the highest percentage of photo-reactivation observed for E. coli and the fecal coliform strain was 29% and 15% respectively. B. subtilis showed little photo-reactivation under these conditions. The percentage of photo-reactivation was related to the UV dose and the photo-reactivating time, and a function was developed to forecast the final concentrations of E. coli and the fecal coliform strain after UV disinfection with possible photo-reactivation. Conclusion Different species of bacteria displayed different responses to UV light and different repair potentials. The repair of indigenous bacteria in wastewater needs to be investigated in future work.

Prediction of advanced oxidation performance in UV/H2O2 reactor systems with LP-UV lamps

Advanced oxidation processes, like UV/H2O2 oxidation, are important barriers against organic micro pollutants in drinking water treatment. In order to guarantee safe drinking water, it is important to be able to predict the reactors' performance to adjust the operating conditions to the actual influent water characteristics (like UV transmission) and lamp performance. Therefore, a design tool was developed, which is based on a kinetic model that describes and predicts the direct photolysis and oxidation of organic compounds in pilot experiments, using Low Pressure (LP) UV-lamps. This model has been combined with computational fluid dynamics (CFD), in order to be able to accurately predict the results of pilot and full scale installations, and also to design reactor systems. The model was applied to three model compounds (atrazine, ibuprofen and NDMA) in two different pilot reactors, and it has been shown that reactor performance can be fairly predicted by applying this ‘UVPerox’ model. The model takes into account the water quality and power of the lamps, and the properties of the compounds involved.

Transformation kinetics of biochemically active compounds in low-pressure UV Photolysis and UV/H2O2 advanced oxidation processes

Factors controlling photolysis and UV/H2O2 photooxidation rates of the biochemically active compounds (BACs) sulfamethoxazole, sulfamethazine, sulfadiazine, trimethoprim, bisphenol A, and diclofenac were determined. Experiments were conducted with a quasi-collimated beam apparatus equipped with low-pressure UV lamps. The effects of pH, H2O2 concentration, and background water matrix (ultrapure water, lake water, wastewater treatment plant effluent) on BAC transformation rates were evaluated. For the sulfa drugs, solution pH affected direct photolysis rates but had little effect on the hydroxyl radical oxidation rate. For sulfamethoxazole, the neutral form photolyzed more easily than the anionic form while the reverse was the case for sulfamethazine and sulfadiazine. For trimethoprim, the hydroxyl radical oxidation rate was higher for the cationic form (pH 3.6) than for the neutral form (pH 7.85). Quantum yields and second order rate constants describing the reaction between the hydroxyl radical and BACs were determined and used together with background water quality data to predict fluence-based BAC transformation rate constants (k′). For both the lake water and wastewater treatment plant effluent matrices, predicted k′ values were generally in good agreement with experimentally determined k′ values. At typical UV/H2O2 treatment conditions (fluence = 540 mJ cm−2, H2O2 dose = 6 mg L−1), BAC transformation percentages in North Carolina lake water ranged from 43% for trimethoprim to 98% for diclofenac. In wastewater treatment plant effluent, BAC transformation percentages were lower (31–97%) at the same treatment conditions because the hydroxyl radical scavenging rate was higher.

Photooxidation in Combination with Nanotechnologies - Principles, Developments and R&amp;D Approaches of an Advanced Technology for Water and Air Treatment - Uviblox®

AbstractMany organic and oxidizable inorganic substances are main targets for oxidation and destruction during treatment, purification and disinfection of contaminated ground water, waste water, air, soil and waste gas and odor. Uviblox® technology uses the effects of photooxidation and photocatalytical processes by middle and low pressure UV lamps for technical systems. There are many possibilities for combination and optimisation of photooxidation with other technologies like nanotechnologies. Degradation processes can be enforced by nano structures of photocatalysts significantly. Different approaches are strongly pursued in research &amp; development projects like NanoAqua, Fe-NANOSIT and nanoblox. These projects search for different ways of applying and handling the photocatalytical nano particles like TiO

Photodegradation and toxicity changes of antibiotics in UV and UV/H 2O 2 process

The photodegradation of three antibiotics, oxytetracycline (OTC), doxycycline (DTC), and ciprofloxacin (CIP) in UV and UV/H 2O 2 process was investigated with a low-pressure UV lamp system. Experiments were performed in buffered ultrapure water (UW), local surface water (SW), and treated water from local municipal drinking water treatment plant (DW) and wastewater treatment plant (WW). The efficiency of UV/H 2O 2 process was affected by water quality. For all of the three selected antibiotics, the fastest degradation was observed in DW, and the slowest degradation occurred in WW. This phenomenon can be explained by R OH,UV, defined as the experimentally determined OH radical exposure per UV fluence. The R OH,UV values represent the background OH radical scavenging in water matrix, obtained by the degradation of para-chlorobenzoic acid (pCBA), a probe compound. In natural water, the indirect degradation of CIP did not significantly increase with the addition of H 2O 2 due to its effective degradation by UV direct photolysis. Moreover, the formation of several photoproducts and oxidation products of antibiotics in UV/H 2O 2 process was identified using GC–MS. Toxicity assessed by Vibrio fischer (V. fischer), was increased in UV photolysis, for the photoproducts still preserving the characteristic structure of the parent compounds. While in UV/H 2O 2 process, toxicity increased first, and then decreased; nontoxic products were formed by the oxidation of OH radical. In this process, detoxification was much easier than mineralization for the tested antibiotics, and the optimal time for the degradation of pollutants in UV/H 2O 2 process would be determined by parent compound degradation and toxicity changes.