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1.
The chemical treatment of cork‐processing wastewater by ozonation, alone and in combination with hydrogen peroxide and UV radiation was investigated. A reduction of the chemical oxygen demand (COD) ranging from 42% to 76% was obtained during ozonation after 3 h of reaction, depending on the experimental conditions. The additional presence of hydrogen peroxide and UV radiation enhanced the efficiency of the ozonation treatment due to the contribution of the OH radicals formed in the decomposition of ozone. Thus, final reductions of the COD higher than 90% and a complete elimination of phenolic compounds and absorbance at 254 nm were achieved in both Advanced Oxidation Processes (AOPs), O3/H2O2 and O3/UV. Therefore the effluent resulting from the ozonation treatments can be reused in the cork‐processing industry. In a second step, the chemical treatment was conducted by means of UV radiation alone and by the action of hydroxyl radicals, which were generated by the following AOPs: UV/H2O2, Fenton's reagent, and photo‐Fenton system. The single photochemical process resulted in 9% of the organic matter present being removed, while the AOPs significantly enhanced this reduction with values in the range 20–75%. Kinetic studies for both groups of treatments were performed, and apparent kinetic rate constants were evaluated. In the ozone‐based experiments, the rate constants ranged from 1846 to 10922 dm3 mol?1 O3 h?1, depending on the operating conditions. In the oxidation experiments using oxidants other than ozone, the rate constants varied between 0.06 and 1.19 h?1. Copyright © 2004 Society of Chemical Industry  相似文献   

2.
Several advanced oxidation processes for the destruction of cyanide contained in waste waters from thermoelectric power stations of combined‐cycle were studied. Thus, oxidation processes involving ozonation at basic pH, ozone/hydrogen peroxide, ozone/ultraviolet radiation and ozone/hydrogen peroxide/ultraviolet radiation have been carried out in a semi‐batch reactor. All these methods showed that total cyanide can be successfully degraded but with different reaction rates, and the decrease in the total cyanide concentration can be described by pseudo‐first order kinetics. The influence of pH and initial concentration of hydrogen peroxide was studied to find the optimal conditions of the oxidation process. Experimental results of the single ozone treatment indicated that total cyanide is destroyed more rapidly at higher pH (12), while ozonation combined with H2O2 and/or UV is faster at pH 9.5. The optimum concentration of H2O2 was 20.58 × 10?2 M because an excess of peroxide decreases the reaction rate, acting as a radical scavenger. The total cyanide degradation rate in the O3/H2O2(20.58 × 10?2 M ) treatment was the highest among all the combinations studied. However, COD reduction, in the processes using UV radiation such as O3/UV or O3/H2O2/UV was about 75%, while in the processes with H2O2 and/or O3/H2O2 was lower than 57% and was insignificant, when using ozone alone. Copyright © 2003 Society of Chemical Industry  相似文献   

3.
This treatability study evaluated the overall effectiveness of advanced oxidation processes (AOPs) to treat membrane concentrates containing the pesticides bromoxynil and trifluralin. The results of study indicate that high levels of pesticide degradation were achieved using ozone (O3) plus hydrogen peroxide (H2O2) for all concentrate matrices. However, the toxicity of the samples during the O3/H2O2 process was higher than that obtained during ultraviolet (UV) light combined with H2O2. Low levels of pesticide oxidation were observed in experiments using a mixture of pesticides during all treatment options.  相似文献   

4.
Model dyeing and laundering wastewaters produced during two basic technological operations of the textile industry were subjected to treatment by advanced oxidation processes (AOPs). The following agents were used: ozone (O3), hydrogen peroxide (H2O2) and UV radiation. They were applied separately and in all possible combinations: O3 + UV, O3 + H2O2, UV + H2O2, as well as all three at the same time: O3 + UV + H2O2. Effluents before and after the treatment were analyzed according to requirements of the Polish Standards that included pH, color threshold, COD and concentration of anionic and non-ionic surfactants. Ozonation was carried out in a lab-scale bubble column reactor with a centrally located UV burner. The most effective version of AOPs proved to be the simultaneous use of all three agents. In the case of such treatment of dyeing wastewaters nearly complete discoloration and full decomposition of surface-active substances were obtained at 80% reduction of COD. A similar tendency was observed in the case of laundering wastewater, though in that case the results were slightly worse, which may be explained by much higher initial concentrations of the pollutants. Good treatment effects have also been obtained in combined treatment by simultaneous use of hydrogen peroxide and ozone.  相似文献   

5.
The additional removal of trace organic contaminants (TOrCs) provided by advanced water and wastewater treatment inevitably requires additional financial costs, which must be estimated to support utility planning and compare alternatives. This study presents conceptual-level (Class 4) capital and annual operations and maintenance (O&M) cost curve equations to aid evaluations of advanced treatment trains for water reuse. The cost curve equations are broadly applicable to the water reuse community, particularly those interested in ozone-based treatment trains. Unit processes include microfiltration or ultrafiltration membranes (MF/UF), nanofiltration or reverse osmosis membranes (NF/RO), ozone (with or without hydrogen peroxide, H2O2), ultraviolet (UV) treatment with H2O2 (UV/H2O2), and biological activated carbon (BAC); all cost curves are for a unit process and can be added together to obtain costs for a combined treatment train. The cost curves indicate that at all plant capacities (1 to 500 MGD), membrane treatment (e.g., MF or RO) represents the highest cost unit process, ozone the least, and BAC or UV/H2O2 fall in between. Additionally, the relationship between ozone dose and TOrC removal is discussed with a demonstration of how costs change with increasing ozone dose to achieve desired TOrC destruction.  相似文献   

6.
The present study investigates the degradation of PGMEA and its TOC removal using O3, UV/O3, O3/H2O2, and UV/H2O2 processes under various experimental conditions. Ozonation of PGMEA was substantially enhanced in the presence of UV light and H2O2. Approximately 33% of TOC enhancement was noted in UV/O3 process over ozonation process. A linear relationship between PGMEA and H2O2 decomposition was observed in O3/H2O2 and UV/H2O2 processes. The influence of solution pH on the decomposition of PGMEA was investigated and found that basic medium was the most efficient in all AOPs. After 60 minutes 62.4%, 100%, 90% and 54% of PGMEA decomposition at pH 10.0 was observed in O3, UV/O3, O3/H2O2, and UV/H2O2 processes, respectively. It is concluded that UV/O3 process is a promising approach for the oxidation and removal of PGMEA.  相似文献   

7.
The efficiency of ozonation and advanced oxidation processes such as ozone/UV, ozone/H2O2 and H2O2/UV was assessed for chlorinated hydrocarbons using a closed batch-type system. 1,1-Dichloropropene (DCPE), trichloroethylene (TCE), 1-chloropentane (CPA), and 1,2-dichloroethane (DCA) were used as model compounds.

The direct reaction between substrates and ozone predominated at lower pH, which resulted in the efficient oxidation of the olefin, DCPE. At higher pH, ozonation resulted in more efficient oxidation of the chlorinated alkanes, with a corresponding decrease in the efficiency of DCPE oxidation. Consistent results were observed for ozone/H2O2 and ozone/UV treatment. Due to slow UV-induced decomposition of H2O2, the process using H2O2/UV (254 nm) resulted in very slow oxidation of all four compounds.

The total ozone requirement to achieve a given degree of elimination (to 37% of the original concentration), δ0.37, was used to assess the combined effects of the direct and indirect reactions for different types of waters.  相似文献   


8.
The degradation of the organic content of a bleaching Kraft mill effluent was carried out using Advanced Oxidation Processes (AOPs). The study was focused on the identification of the AOP, or combination of AOPs, that showed the highest efficiency together with the lowest cost. Direct UV photolysis (UV), TiO2 assisted‐photocatalysis (TiO2/UV), Fenton, Fenton‐like, and photo‐Fenton reactions (Fe(II)/H2O/UV), UV‐assisted ozonation (O3/UV) and addition of Fe2+ and/or H2O2 to the TiO2/UV and the O3/UV systems, were used for the degradation of a conventional cellulose bleaching effluent. The effluent was characterized by the general parameters TOC, COD and color, and analyzed for chlorinated low molecular weight compounds using GC–MS. The costs of the systems per unit of TOC reduction were compared. Fenton, Fenton‐like and photo‐Fenton reactions achieved better levels of TOC degradation than photocatalysis and with lower cost's than photocatalytic treatments. Ozonation is an effective but rather expensive process. The use of UVA light, however, increased the effectiveness of ozonation with a significant decrease (>25%) in the operational cost. © 2002 Society of Chemical Industry  相似文献   

9.
The degradation of 1,4-dioxane was investigated on a laboratory scale. The extents of degradation and/or removal of 1,4-dioxane by ozonation at pH 6–8, UV irradiation, aeration, and addition of H2O2 were very limited. On the other hand, the degradation of 1,4-dioxane by O3/UV and O3/H2O2 was accelerated compared with the above respective methods. The amounts of 1,4-dioxane degraded per amount of ozone consumed in O3/UV and O3/H2O2 were also higher than in ozonation. The amount of 1,4-dioxane degraded in O3/UV was affected by the intensity of UV irradiation, and that in O3/H2O2 was affected by the amount of H2O2 added only in the case of a high initial concentration of 1,4-dioxane.  相似文献   

10.
Both the direct ozone reaction and the indirect hydroxyl radical reaction are important in the ozonation of drinking water. This paper investigates the effectiveness of ozone versus ozone coupled with hydrogen peroxide (peroxone) with respect to trihalomethanes formation. The investigation was conducted on a pilot-scale at various H2O2:O3 dose ratios of 0.1, 0.2, and 0.35 and change in peroxide addition point (pre- and post-ozonation). It was observed that the addition of peroxide, either before or after ozonation, increased trihalomethane concentrations and that increasing H2O2:O3 increased trihalomethane concentrations. In comparing the addition point of peroxide, addition prior to ozonation better controlled trihalomethane formation than after ozonation.  相似文献   

11.
The discoloration of a biologically pretreated wastewater stream from a molasses processing by ozonation and two advanced oxidation processes (O3/H2O2 and O3/γ-irradiation, respectively) was studied. Color removal occurred with all three processes with almost the same efficiency. The main difference between the methods applied was reflected by the BOD increase during the discoloration period. By ozonation it was much higher than by AOPs, but it also appeared with AOPs. AOPs therefore, were not appropriate as an effective BOD control during discoloration.  相似文献   

12.
The present studies covered investigations of advanced oxidation of detergents in industrial wastewater with the use of ozone, hydrogen peroxide, UV and ionizing radiation separately and in combinations: O3+UV, UV+H2O2, H2O2+O3, O3+H2O2+UV, O3+ ionizing radiation in the flow systems taking into account specific features of subsequent versions. The aim of these studies was to present results of detergent decomposition in the applied versions and also in the flow systems compared to stationary systems. The radiation processes were carried out with high efficiency in all stationary and flow systems tested. The best results of detergent decomposition were achieved in the samples exposed to simultaneous radiation and ozonation.  相似文献   

13.
The performance of the O3, O3/UV and UV/H2O2 processes for degradation of six chlorophenols (4-chlorophenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol) were studied in laboratory reactors. Comparative study showed that chlorophenols can be degraded successfully by all of the methods studied, whilst traditional ozonation at high pH was determined to be the most effective method to treat chlorophenols. Even though the molar absorptivity of chlorophenols is known to be relatively high in the UV-region, the combination of UV-radiation with ozone did not accelerate the degradation of chlorophenols further. The toxicity of degradation products formed during ozonation of chlorophenols has been compared with the toxicity of pure chlorophenols utilizing Daphnia magna 24 hours test. Ozonation of chlorophenols yielded less toxic or even nontoxic products for Daphnia magna compared with parent compounds.  相似文献   

14.
This study analyzes the performances of 2 methods of oxidation based on ozone, namely ozonation and ozone combined with hydrogen peroxide (O3/H2O2), on two biotreated municipal wastewater effluents. The main parameters monitored to evaluate the effectiveness of the processes were Chemical Oxygen Demand (COD), Dissolved Organic Carbon (DOC) and Biochemical Oxygen Demand (BOD5). Ozonation and O3/H2O2 treatment removed 44% and 48%, respectively, of the COD, after 90 min, of the secondary effluent of Calafell wastewater treatment plant (Spain). On the secondary effluent from the Grasse wastewater treatment plant (France), these same treatments (O3; O3/H2O2) achieved, respectively, a degradation of 52% and 100% of the COD after 60 min. The transferred ozone dose (TOD) during Calafell and Grasse effluents' ozonation were 122 mg·L?1 and 77 mg·L?1 after 90 min, respectively. A low removal of DOC was monitored during both O3 or O3/H2O2 treatments applied to Calafell wastewater, respectively 12% and 14%. Better DOC reductions were obtained on the water of Grasse treated with O3 or O3/H2O2, respectively, 48% and 60%. In addition, ammonia nitrogen was oxidized to nitrate nitrogen thus giving rise to an over ozone consumption. And finally, both processes proceeded with an increase of pH values. These results highlight the strong dependency of O3 or O3/H2O2 treatment effectiveness in terms of dissolved organic matter (DOM) removal and ozone consumption on wastewater composition (organic and inorganic substances).  相似文献   

15.
This paper reports a study using ozone (O3) and combined ozone/ultraviolet (O3/UV) processes for color removal and caffeine degradation from synthetic coffee wastewater using a second-order response surface methodology (RSM) with a three-level central composite face-centered (CCF) design. The effects of O3 concentration, initial pH, and reaction time were examined for both processes. The reaction time and pH were statistically significant for caffeine degradation and color removal. In the ozonation process, higher caffeine degradation and color removal were observed in alkaline pH, indicating that ozone attacks indirectly, consequently generating hydroxyl radicals. Regarding the ozone/UV process, it was observed that lower caffeine degradation and color removal occurred at neutral pH, indicating an adverse effect due to lower ozone dissolution and consequently the production of a smaller amount of free hydroxyl radicals. The achieved results showed that the techniques were efficient for color removal (85% and 99%, respectively) and caffeine degradation (88% and 98%, respectively).  相似文献   

16.
Diazinon is a widely used organophosphorus insecticide that is an important pollutant in aquatic environments. The chemical removal of diazinon has been studied using UV radiation, ozone, Fenton's reagent, UV radiation plus hydrogen peroxide, ozone plus hydrogen peroxide and photo‐Fenton as oxidation processes. In the photodegradation process the observed quantum yields had values ranging between 2.42 × 10?2 and 6.36 × 10?2 mol E?1. Similarly, the ozonation reaction gave values for the rate constant ranging between 0.100 and 0.193 min?1. In the combined systems UV/H2O2 and O3/H2O2 the partial contributions to the global oxidation reaction of the direct and radical pathways were deduced. In the Fenton's reagent and photo‐Fenton systems, the mechanism of reaction has been partially discussed, and the predominant role of the radical pathway pointed out. Additionally, the rate constant for the reaction between diazinon and the hydroxyl radicals was determined, with the value 8.4 × 109 L mol?1 s?1 obtained. A comparison of the different oxidation systems tested under the same operating conditions revealed that UV radiation alone had a moderate oxidation efficiency, which is enhanced in the case of ozone, while the most efficient oxidant is the photo‐Fenton system. Copyright © 2007 Society of Chemical Industry  相似文献   

17.
The aim of this study was to investigate the effectiveness of chemical oxidation by applying ozonation, combination of ozone and hydrogen peroxide and Fenton's processes for decolorization and residual chemical oxygen demand (COD) removal of biologically pretreated pulp and paper industry effluents. The batch tests were performed to determine the optimum operating conditions including pH, O3, H2O2, and Fe2+ dosages. H2O2 addition reduced the reaction times for the same ozone dosages; however combinations of ozone/hydrogen peroxide were only faintly more effective than ozone alone for COD and color removals. In the Fenton‘s oxidation studies, the removal efficiencies of COD, color and ultraviolet absorbance at 254 nm (UV254) for biologically treated pulp and paper industry effluents were found to be about 83, 95, and 89%, respectively. Experimental studies indicated that Fenton oxidation was a more effective process for the reduction of COD, color, and UV254when compared to ozonation and ozone/hydrogen peroxide combination. Fenton oxidation was found to have less operating cost for color removal from wastewater per cubic meter than the cost for ozone and ozone/hydrogen peroxide applications.  相似文献   

18.
Applied ozone dosages of 20, 25, and 30 mg/L to lake water utilized by the city of Shreveport, LA produced no significant reductions in trihalomethane formation potentials (THMFP). However, the addition of 20 mg/L of hydrogen peroxide and/or 0.67 W/L of UV radiation (254 nm) in combination with ozone produced decreases in THMFP of over 60% in 60 minutes. Smaller THMFP decreases were seen with shorter contact times. The use of H2O2 and/or UV in combination with O3 increased the percentage of applied ozone consumed by the lake water (i.e., enhanced the ozone mass transfer) five times over simple ozonation.  相似文献   

19.
Photocatalytic degradation of polyvinylpyrrolidone (PVP) by titanium dioxide and ozone in an annular reactor was investigated using a 125-W mercury vapor lamp as the light source. It was observed that the TiO2/O3/UV process presented a greater efficiency than the TiO2/UV process. In fact, around 90% of the mineralization was obtained in 1 h of reaction, reflecting the synergistic effect of the combination of O3 and TiO2 under UV light, because the sum of the rate constants of the individual processes is less than the rate constant of the combined process. The effects of the initial PVP concentration, photocatalyst dosage, ozone input flow rate and pH on the PVP degradation rate were studied. In general, the results suggest that PVP can undergo a cross-linking process when the TiO2/O3/UV treatment is applied. The reaction rate was increased when the photocatalyst dosage was increased up to 2.0 g L?1; however, increasing the initial PVP concentration led to a drop in the reaction rate. The efficiency also decreased at basic pH, because ozone is decomposed under alkaline conditions. In addition, it was noted that most of the nitrogen atoms of the macromolecules of PVP can be transformed into nitrate and ammonia during photocatalytic ozonation.  相似文献   

20.
Disinfection of anaerobically treated effluent (UASB) was carried out to eliminate the enteric pathogens by using UV irradiation, peracetic acid, H2O2, O3 and advanced oxidation processes (O3/H2O2, O3/UV and H2O2/UV). Re-growth potential of these pathogens was monitored in terms of time and temperature. Inactivation of pathogens by ozone at the rate of 300 mg/h for 20 minutes approached 99%. UV irradiation resulted in 99% pathogen removal at irradiation time of 120 seconds. A dose of 170 mg/L H2O2 eliminated more than 99% pathogens. Samples disinfected with UV, H2O2 and O3 showed gradual re-growth with an increase in time and temperature (from 20 to 35°C). However, disinfection with AOPs proved to be the most effective tool resulting in reduction of treatment time taken by individual processes, also the disinfected samples showed minimal re-growth revealing the superiority of their combined effects.  相似文献   

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