臭氧降解水中邻苯二甲酸二甲酯的效能及动力学

利用臭氧降解含较高浓度邻苯二甲酸二甲酯(DMP)的模拟废水,考察了pH、DMP初始浓度、臭氧投加量和温度对臭氧降解DMP效果的影响,并对臭氧降解DMP的效能及动力学进行了研究。结果表明,pH为5～10时DMP的降解效果较好;DMP初始浓度越大,DMP降解率越小,但DMP降解量增加;臭氧投加量的增加有利于DMP降解,但臭氧利用效率降低;温度低时,升高温度DMP降解率增大,24℃后提高温度对DMP降解率影响不大。在pH为5～10、DMP初始浓度为14～66 mg·L^-1、O₃投加量为14～24 mg·min^-1、20～30℃条件下反应40 min,DMP降解率达85%以上。在实验条件范围内,臭氧降解DMP符合拟一级动力学,建立了幂指数表达的动力学模型。在pH为2～12范围内,因臭氧反应机理不同,表观动力学常数k_obs与pH不呈线性关系,pH为2～5时,k_obs快速增加,pH为5～9时,k_obs缓慢增加,pH大于9时k_obs反而降低,pH为9时k_obs最大,为0.0929 min^-1。     

Ozone treatment of textile effluents and dyes: effect of applied ozone dose,pH and dye concentration

The ozonation of wastewater supplied from a treatment plant (Samples A and B) and dye‐bath effluent (Sample C) from a dyeing and finishing mill and acid dye solutions in a semi‐batch reactor has been examined to explore the impact of ozone dose, pH, and initial dye concentration. Results revealed that the apparent rate constants were raised with increases in applied ozone dose and pH, and decreases in initial dye concentration. While the color removal efficiencies of both wastewater Samples A and C for 15 min ozonation at high ozone dosage were 95 and 97%, respectively, these were 81 and 87%, respectively at low ozone dosage. The chemical oxygen demand (COD) and dissolved organic carbon (DOC) removal efficiencies at several ozone dose applications for a 15 min ozonation time were in the ranges of 15–46% and 10–20%, respectively for Sample A and 15–33% and 9–19% respectively for Sample C. Ozone consumption per unit color, COD and DOC removal at any time was found to be almost the same while the applied ozone dose was different. Ozonation could improve the BOD₅ (biological oxygen demand) COD ratio of Sample A by 1.6 times with 300 mg dm^?3 ozone consumption. Ozonation of acid dyes was a pseudo‐first order reaction with respect to dye. Increases in dye concentration increased specific ozone consumption. Specific ozone consumption for Acid Red 183 (AR‐183) dye solution with a concentration of 50 mg dm^?3 rose from 0.32 to 0.72 mg‐O₃ per mg dye decomposed as the dye concentration was increased to 500 mg dm^?3. © 2002 Society of Chemical Industry     

Ozone-Based Processes Applied to Municipal Secondary Effluents

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).     

Evaluation of Decolorization,Mineralization, and Toxicity Reduction of Tropaeolin O in Water by Ozonation with UV Irradiation

The combination of ozonation with UV irradiation can remove Tropaeolin O (AO6) and its by-products effectively and completely. The ozone dose affects the rate of decolorization, AO6 species removal, and dissolved organic carbon (DOC) reduction significantly. After 240 minutes of ozonation, the average DOC removal efficiency (η_DOC) for O₃ alone was about 0.79, while η_DOC for O₃/UV was 1.0. The average DOC removal rate was low at early stage of ozonation due to decolorization and low DOC. At later stage of ozonation, average DOC removal rate decreases because of the formation of persistent intermediates. The ozone consumption was consistent with η_DOC. The ratio of ozone consumption to ozone applied decreased from 14 to 12% when η_DOC < 40% because the decolorization in the early stage of the ozonation of AO6 may consume a relatively large amount of ozone. It was found that NO₂, NO, CO₂, and small amount of SO₂ was detected in the off-gas. The effective concentration (EC50) increased from 23.48% to 100%, suggesting that the toxic reduction was achieved, and O₃/UV system was superior to O₃ alone system     

Ozonation of estrone, estradiol, diethylstilbestrol in waters

The ozonation of three environmental endocrine disrupters (EDCs), estrone(E₁), estradiol(E₂), and diethylstilbestrol(DES), in aqueous solutions were investigated. Batch experiments were carried out to research the effect of initial EDCs concentrations, initial pH values and ozone dosages on the degradation efficiency. At pH 9.0, the degradation efficiency of estrone (E₁) reached to 94% after 8 min; diethylstilbestrol could be totally degraded after 6 min, and even estradiol was completely degraded after only 4 min. After 6 min for ozonation, the degradation efficiency of E₂ was nearly 48% with ozone dosage of 0.13 mg min^− 1. Compared with the ozone dosage of 0.38 mg min^− 1, E₂ entirely degraded after 6 min. Ozone dosage on degradation of E₁ was in a similar way. DES had analogous rule. At four different concentration solutions (5-20 mg L^− 1) of EDCs exposed to ozone, the higher the initial EDCs concentration, the lower EDCs degradation efficiency was obtained. During the ozonation process, the rapid decreasing of pH and the sharp increasing of electrical conductivity indicated the higher polarity by-products were produced during ozonation, which was confirmed by high performance liquid chromatography (HPLC) analysis. The results could provide some useful information for the potential treatment of EDCs by ozonation in waters.     

Simultaneous removal of COD and NH3‐N in secondary effluent of high‐salinity industrial waste‐water by electrochemical oxidation

BACKGROUND: Electrochemical oxidation has been applied successfully in industrial waste‐water treatment. The simultaneous removal of COD_Cr and NH₃‐N, as well as the corresponding mechanisms and reaction zone, were examined in this study. The reaction kinetics and the significant factors that affect removal performance were also studied. RESULTS: The COD_Cr removal efficiency without chlorides in waste‐water was only 11.8% after 120 min of treatment, which was much lower than the efficiency with chlorides, and agitation did not improve the performance. When the current density was increased from 2.5 to 10 mA cm^?2, the removal efficiency was improved. The removal efficiencies of COD_Cr and NH₃‐N were less at initial pH = 11 than at pH = 3 and 8.7 (without adjustment). The COD_Cr and NH₃‐N removal efficiencies were decreased by about 30% and 50%, respectively, when the electrode distance was increased from 4 to 12 cm. Instantaneous current efficiency decreased with increase in current density. CONCLUSIONS: The degradation of pollutants occurred mainly at the boundary layer between the electrode and the bulk solution. The indirect oxidation by active chlorine generated from the chlorides was proven to be the primary mechanism of electrochemical oxidation treatment. The removal of COD_Cr in this study followed a pseudo‐first‐order kinetic model. Copyright © 2011 Society of Chemical Industry     

臭氧/活性炭组合工艺降解甲基红印染废水的试验研究

文章采用臭氧/活性炭组合工艺对甲基红印染废水进行降解试验,考察了甲基红废水的pH、活性炭投加量、温度和臭氧流量等参数对印染废水色度和CODCr去除率的影响,确定了臭氧/活性炭组合工艺降解甲基红印染废水的最佳工艺条件。结果表明,在pH为3.5,温度为25℃,活性炭投加量为120 mg/L,臭氧流量为0.83 L/min,初始浓度为10 mg/L的条件下降解10 min,臭氧/活性炭组合工艺对甲基红废水的脱色率达到97.4%,CODCr去除率达到85.2%。该组合工艺能有效地去除印染废水的色度和CODCr,使出水水质达到处理标准。     

Fe(Ⅱ)(EDTA)/O3工艺处理含聚废水实验

采用Fe(Ⅱ)(EDTA)/O₃工艺处理含聚废水,研究EDTA浓度、Fe²⁺浓度、水力停留时间（HTR）、初始pH对聚丙烯酰胺（PAM）去除率和COD降解效能的影响,探讨了Fe(Ⅱ)络合催化臭氧反应动力学特征及其机理。结果表明：当EDTA浓度为0.050mmol/L、Fe²⁺浓度为0.050mmol/L和HRT为120min时,PAM去除率为75%;增加水样初始pH有利于提高PAM去除率,同时水样pH随HRT增加缓慢下降;废水COD值在HRT为30min内逐渐增至最大,随后逐渐减小并达到稳定。Fe(II)(EDTA)/O₃工艺处理含聚废水的反应符合二级动力学反应,初始PAM质量浓度在50~100mg/L范围内,二级反应速率常数为2.35×10^-4~3.35×10^-4L/(mg·min)。     

pH Effect on Ozonation of Ampicillin: Kinetic Study and Toxicity Assessment

Ampicillin (AP) is a penicillin-type antibiotic and one of the most widely used bacteriostatic antibiotics in human and veterinary medicine. A kinetic study was performed under different pH conditions (5, 7.2, and 9) to determine the degradation efficiency of AP by ozonation. The second-order rate constants for the direct reaction of AP with ozone were measured to be 2.2 ?5.4×10⁵ M^?1s^?1 under the pH conditions tested. The rate constants were greater at higher pH. The potential toxicity of the AP intermediates formed after ozonation under the various pH conditions were examined using a bioluminescence assay on Vibrio fischeri species. The biodegradability of the AP degraded products was also determined by measuring the BOD₅/COD of the ozonated samples under the different pH conditions. A lower biodegradability and acute toxicity was observed at the lowest pH (pH 5). These results suggest that higher pH conditions are needed for the removal of AP by ozonation in order to mitigate the residual toxicity that can remain even after complete removal of the parent compound by ozonation.     

Process Control For Ozonation Systems: A Novel Real-Time Approach

For real-time control of ozonation processes in water works, a sequencing batch reactor was constructed to measure the ozone decay rate constant (k_O3) in short time intervals of about 15 min. The batch reactor is filled during the production process, immediately after dissolving ozone in water by a static mixer. On the basis of k_O3 and the initial ozone concentration ([O₃]₀), and the experimentally determined ratio of the concentrations of ^?OH radicals to ozone (R_ct), the degradation of micropollutants in ozone reactors (modeled as Continuously Stirred Tank Reactors - CSTRs) were calculated for compounds with known reaction rate constants with ozone and ^?OH radicals. Calculated degradation of atrazine, iopromide, benzotriazole and acesulfame are in good agreement with measured data. For acesulfame the following rate constants were determined in this study at 20 ^oC: reaction rate constant with ozone = 88 M^?1s^?1, reaction rate constant with ^?OH radical = 4.55?×?10⁹ M^?1s^?1. For the ozone reaction an activation energy of 35 kJ/mol was determined. Similarly to micropollutants, the relative inactivation of microorganisms (N/N₀) can be calculated based on the inactivation rate constant for ozone and if applicable the lag phase. The pI-value (=??logN/N₀) was introduced and implemented in the process management system to calculate online the log inactivation of reference microorganisms such as B. subtilis spores. The system was tested for variation of pH (6.5–8.5), DOC (1.2–4.2 mg/L) flowrate 3.2–12 m³/h and temperature (5.7–9 ^oC). Furthermore, a given pI-value, e.g. 1 for a 1-log inactivation of B. subtilis spores, can be set as control parameter in the process management system. The ozone gas flow is then adjusted until the set pI-value is reached. The process control concept was validated with B. subtilis spores. Generally, a good agreement was found between calculated and measured inactivation data. It was also demonstrated, that a constant ozone residual may lead to insufficient disinfection or overdosing of ozone. The new process control concept for ozonations based on onsite measurement of the ozone decay rate constant and the pI-value allows to assess disinfection and degradation processes quantitatively in real-time.     

Ozonation of Phenol-Containing Wastewater Using O3/Ca(OH)2 System in a Micro Bubble Gas-Liquid Reactor

The degradation of phenol in aqueous solution was investigated in an integrated process consisting of O₃/Ca(OH)₂ system and a newly developed micro bubble gas-liquid reactor. The effects of operating parameters such as Ca(OH)₂ dosage, reactor pressure, liquid phase temperature, initial phenol concentration and inlet ozone concentration on degradation and mineralization (TOC removal) were studied in order to know the ozonation performance of this new integrated process. It is demonstrated that the degradation and TOC removal efficiency increased with increasing inlet ozone concentration and increasing Ca(OH)₂ dosage before 2 g/L, as well as decreasing initial phenol concentration. The optimum Ca(OH)₂ dosage should exceed Ca(OH)₂ solubility in liquid phase. The reactor pressure and liquid phase temperature have little effects on the removal and TOC removal efficiency. When Ca(OH)₂ dosage exceeded 3 g/L, the degradation and TOC removal of phenol almost reached 100% at 30 and 55 min, respectively. The intensification mechanism of Ca(OH)₂ assisted ozonation was explored through analysis of the precipitated substances. The mechanism for Ca(OH)₂ intensified mineralization of phenol solution is the simultaneous removal of CO₃^2- ions, as hydroxyl radical scavengers, due to the presence of Ca²⁺ ions. Results indicated that the proposed new integrated process is a highly efficient ozonation process for persistent organic wastewater treatment.     

Enhancement of Ozone Mass Transfer by Stainless Steel Wire Mesh and Its Effect on Hydroxyl Radical Generation

ABSTRACT

In order to improve the mass transfer efficiency of ozone in water, stainless steel wire mesh (SSWM) corrugated structure was packed into a microbubble ozone reactor to enhance the mass transfer efficiency. The results showed that the SSWM/O₃ system could effectively improve the mass transfer efficiency. When the concentration of ozone in the liquid phase reached a stable state, it was about 21 mg/L, which was about 14% higher than that of ozone alone; the apparent mass transfer coefficient (K_La) was 0.7255 min^?1, which was about 51% higher than that by ozone alone systems. The hydroxyl radicals in the SSWM/O₃ system were more generated than that of ozone alone. After 6 min of operation, the concentration of hydroxyl radicals increased by 60 µmol/L compared with that in ozone alone system. The Chemical Oxygen Demand (COD) removal efficiency of biologically treated leachate by SSWM/O₃ system was about 10% higher than that of ozone alone system after 120 min of reaction. The effects of pressure, temperature, ozone inlet concentration, and flow rates on the ozone concentration in the liquid phase and the generation of hydroxyl radicals were also investigated. The results indicated that reactor pressure has little effect on ozone concentration in liquid phase, but increasing pressure helps to generate ·OH; ozone concentration and ·OH generation in liquid phase increase with the increase of inlet ozone concentration and flow rate; ozone concentration in the liquid phase decreases with the increase of temperature, but ·OH generation increases with the increase of temperature. Our results indicate that the system consisting of SSWM and microbubble column reactor is an efficient process for the intensification of ozone-based advanced oxidation processes.     

Degradation of azo dye from aqueous solutions using nano-SnO2/Ti electrode prepared by electrophoretic deposition method: Experimental Design

In this work, degradation of C.I. Acid Red 33 (AR33) in aqueous solutions was investigated. The combined electrolysis–ozone (ECO) process optimized based on SnO₂ nanoparticles electrode (nano-SnO₂/Ti) as anode using response surface methodology (RSM) involving a five-level central composite design (CCD). The nano-SnO₂/Ti electrode was prepared using electrophoretic deposition (EPD) method. The electrode was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV). The initial pH, current density, reaction time and electrolyte concentration were selected as independent variables in central composite design while color removal efficiency was considered as the response function. Based on analysis of variance (ANOVA), the coefficient of determination value (R² = 0.981) was high. In optimum conditions, maximum color removal efficiency (93.2%) was obtained after 16 min; and the removal of chemical oxygen demand (COD) was reduced to 57.1% after 60 min.     

Removal of Ethylenediaminetetraacetic acid (EDTA) from Pulp Mill Effluents by Ozonation

Ozone application was investigated for its effectiveness in the removal of ethylenediaminetetraacetic acid (EDTA) from bleaching effluent. The objectives were to compare the efficiency of ozone reaction on Na-EDTA solution with pure Fe³⁺-EDTA complex and EDTA complexes in bleaching effluent, and to test if changing pH and addition of hydrogen peroxide (H₂O₂) increases the removal of EDTA. Small ozone doses destroyed high proportions of Na-EDTA. This effect was diminished when EDTA formed complexes with other metal ions. It was shown that EDTA present in bleaching effluent was more easily oxidizable than in pure Fe³⁺-EDTA solution. Variation of initial pH value had no significant influence on the removal of Na-EDTA. Addition of hydrogen peroxide did not increase degradation of EDTA in bleaching effluent.     

Application of Response Surface Methodology for Coffee Effluent Treatment by Ozone and Combined Ozone/UV

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).     

Examining the Role of Effluent Organic Matter Components on the Decomposition of Ozone and Formation of Hydroxyl Radicals in Wastewater

The impact of wastewater derived effluent organic matter (EfOM) on the decomposition of ozone and formation of hydroxyl radicals (HO^●) was evaluated for four wastewaters (sites A, B, C1 and C2). The reactivity of EfOM was assessed by fractionation into four apparent molecular weight (AMW) fractions (<10 kDa, <5 kDa, <3 kDa, and <1 kDa). The R_CT, defined as the ratio of HO^● exposure to ozone exposure (∫HO^●dt?/?∫O₃dt), was measured for all fractions and bulk waters (at times greater than 5 seconds), with an initial ozone dose equal to the total carbon concentration of EfOM (ozone:DOC ratio of 1). The R_CT of all the samples and ozone first-order decay rates of two of the waters increased significantly (95% confidence) from the bulk sample to the <10 kDa fraction, and decreased with AMW. This indicates that the intrinsic capacity of different molecular weight fractions of the EfOM have different reactivity with ozone.     

Impact of Water Temperature on Resolving the Challenge of Assuring Disinfection While Limiting Bromate Formation

Intensive pilot studies were performed to study the impact of ozone dose (0.6 to 3.5 mg/L), pH (6.0 to 7.5), and contact time (12 to 38 min) on bromate (BrO₃) formation, for different sand-filtered water qualities from the Neuilly-sur-Marne Treatment Plant (COT = 1.3 to 2.2 mg/L, TAC = 190 to 230 mg CaCO₃, [Br^?] = 25 to 50 μg/L, and T = 5°C to 26°C). Whatever the water quality studied, the main factors influencing bromate formation were ozone dose, pH, and a cross factor between them. Bromate formation was shown to be proportional to bromide concentration, and to increase only slightly with temperature, depending on the ozone dose and the pH. As on the contrary temperature has an important impact on disinfection, especially when considering Cryptosporidium inactivation, resolving the challenge of ensuring disinfection while limiting bromate formation was shown to be quite easily achievable, at intermediate temperature, and with more stringent conditions at high temperature (because of bromate formation) or at low temperature (because of disinfection).     

Combination of biological and chemical processes for the treatment of textile wastewater containing reactive dyes

The treatment of a segregated textile wastewater containing reactive dyes was investigated in two continuous‐flow process trains using ozonation and biological processes. The degree of decolorization and dissolved organic carbon (DOC) removal achieved by ozonation followed by aerobic treatment (two‐stage) was compared with that found when an anaerobic and aerobic pretreatment was added (four‐stage). Although the biological pretreatment reduced color by ～70%, similar amounts of ozone were required in both trains to achieve high degrees of overall removal of color and DOC. In both trains, ozonation increased biodegradability in the following aerobic reactor, however, in order to reach ～80% overall DOC removal, a specific ozone absorption (A*) of ～6 gO₃ gDOC_o^?1 was required and >50% of the DOC was mineralized in the ozone reactor. A comparison of cost estimates based on investment and operating costs for the process alternatives showed that a four‐stage train would reduce costs only if it enabled a decrease in A* to less than 2 gO₃ gDOC_o^?1. Difficulties in comparing treatment processes for segregated vs full‐stream wastewaters are discussed. Copyright © 2003 Society of Chemical Industry     

Efficiency of EDTA,SDS, and NaOH Solutions to Clean RO Membranes Processing Swine Wastewater

The increasing use of membranes to treat a broad range of wastewaters requires the development of efficient cleaning strategies. The objective of this study was to optimize the efficiency of EDTA-SDS-NaOH solutions to recover flux and remove proteins and bacteria from RO membranes filtering swine wastewater. At 60-min cleaning time, flux recovery (FR) increased with SDS concentrations up to 18 mM, but decreased at 36 mM. Adding up to 20 mM EDTA to the SDS solutions did not improve FR. The SDS-NaOH solutions yielded higher FRs at pH 11/40°C and pH 12/33°C than pH 10/45°C, indicating that increasing pH had a greater impact on cleaning efficiency than increasing temperature. At pH 11/40°C and pH 10/45°C, increasing cleaning time from 60 to 120 min decreased FR at all SDS concentrations, probably because of surfactant adsorption on membrane surface, as opposed to inadequate foulant removal, since residual protein concentration was lower on membranes cleaned for 120 than 60 or 30 min. At pH 12/33°C, however, increasing cleaning time to 120 min improved FR at all SDS levels. The lower temperature or higher pH may have prevented surfactant attachment to the membrane. At pH 12/33°C and 120 min, a solution containing NaOH only yielded similar FRs than an 18-mM SDS solution after up to four consecutive fouling-cleaning cycles. Increasing cleaning time and pH would thus eliminate the need to add a surfactant to the cleaning solution.     

Post-Treatment of Composting Leachate by Ozonation

The post-treatment of composting leachate via an ozonation process in laboratory scale was studied in batch mode. According to the experiments, the COD removal was 47% after 30 min of ozonation via 0.4 g/h ozone (equivalent to 2.8 mg O₃/mg COD removed) at pH 9. In this circumstance, the removal of color and turbidity was also 86% and 89%, respectively. Increasing the ozone mass flow rate higher than 0.4 g/h had no considerable effect on the process variables. However, increasing the reaction time had a significant effect on both the removal of color and on COD of the leachate. Experimental data indicated that complete removal of color and 51% removal of COD were achieved after about 40 min of ozonation via 0.4 g/h ozone (equivalent to 3.3 mg O₃/mg COD removed). The ozone consumption rate increased as the reaction progressed and reached 4.1 mg O₃/mg COD removed after 60 min.