Combined Ozone and Ultrasound for the Removal of 1,4-Dioxane from Drinking Water

Ozone, ultrasound, and ozone/ultrasound processes were evaluated for the removal of 1,4-dioxane from tap water using a continuous flow reactor with on-line aqueous ozone measurement. The addition of ultrasound to ozone was found to significantly boost removal. The removal of 1,4-dioxane by ozone/ultrasound process exceeded the sum of the removals from ozone alone and ultrasound alone. Ultrasound alone showed less than 20% removal of 1,4-dioxane. The effects of reactor pressurization and bicarbonate as a hydroxyl radical scavenger were also studied. It was observed that at constant aqueous ozone concentration, additional pressure in the reactor tended to mute the 1,4-dioxane removal boost noted in the ozone/ultrasound process, while additional pressure did not affect 1,4-dioxane removal via ozone alone. The removal of 1,4-dioxane was found to be dependent on the consumption of aqueous ozone, and the consumption of ozone was found to be increased by either the addition of ultrasound or by increasing pH. Rate constants were calculated for various ozone concentrations for the ozone and ozone/ultrasound processes and the systems were fitted to a Chick–Watson model.     

Removal of 1,4-Dioxane and Volatile Organic Compounds from Groundwater Using Ozone-Based Advanced Oxidation Process

Ozone and ozone/peroxide processes were evaluated for the removal of 1,4-dioxane from laboratory water and site groundwater. The effect of process parameters such as solution pH and dosage of peroxide was studied. Ozone alone was not very effective in removing 1,4-dioxane from water (≤ 20% removal). Enhanced oxidation of 1,4-dioxane was achieved by increasing the solution pH or by adding peroxide at neutral pH. Pseudo–first-order rate constants were calculated for the removal of 1,4-dioxane using ozone. Correlations were developed for the consumption of ozone per 1,4-dioxane removed. Acidic and neutral pH conditions resulted in higher consumption of ozone per dioxane removed. Basic solution pH and presence of hydrogen peroxide enhanced the dioxane removal, which resulted in lower consumption of ozone per dioxane removed. Following the lab study, ozonation was used for the remediation of site groundwater contaminated with 1,4-dioxane and chlorinated volatile organics. Presence of 5 mg/L of hydrogen peroxide during ozonation resulted in simultaneous removal of 1,4-dioxane and volatile organics from groundwater to target levels. For the AOP process, removal kinetics was approximately 50% slower in groundwater compared to the lab DI water.     

1,4-二氯苯在乙腈-水两相系统中的电化学氧化降解途径

研究了乙腈-水两相中Pt电极上1,4-二氯苯的降解途径和氧化特性。实验结果表明,1,4-二氯苯在乙腈-水两相中的氧化电位区间约为2.0～2.3 V(vs SCE),且氧化反应是受扩散控制的不可逆过程。液相色谱、液相色谱-质谱联用、离子色谱等的分析结果表明,乙腈-水两相中1,4-二氯苯氧化中间产物包括对氯苯酚、对苯醌、2,5-二氯对苯醌、草酸根离子、乙酸根离子、甲酸根离子、顺丁烯二酸根离子和氯离子,最终产物为H_2O和CO_2。得出了1,4-二氯苯主要的降解途径有两种。     

Impact of chemical oxidation on biological treatment of a primary municipal wastewater. 1. Effects on cod and biodegradability

Municipal wastewaters taken from a primary sedimentation tank were subjected to different chemical oxidation processes (ozonation or UV radiation alone or combined with hydrogen peroxide) to observe the evolution of COD and BOD/COD ratios. Ozonation of wastewater led to different increases of COD level reduction depending on pH and carbonate‐bicarbonate ion concentrations. Direct photolysis or hydrogen peroxide alone were found to be inappropriate technologies. On the other hand, advanced chemical oxidation, that is, oxidation with ozone or UV radiation combined with hydrogen peroxide, increased COD level reduction only when wastewater was previously decarbonated. Thus, elimination of carbonate‐bicarbonate ions, increase of pH and addition of hydrogen peroxide (10^‐3 M) yield increases COD level reduction rates. Finally, preozonation also allows improvement of wastewater biodegradability.     

The Effect of Bicarbonate on Ozone-Enhanced Particle Removal in Water Treatment

Ozone is known to enhance the removal of particles in coagulation-filtration systems under certain circumstances. In this work it was observed that bicarbonate is required in order for ozone, applied prior to coagulant addition, to have a beneficial effect on coagulation-filtration and that, in the absence of bicarbonate, ozone has a detrimental effect. It is hypothesized that ozone acts in a positive manner via direct molecular reactions and in a negative manner by the hydroxyl radical pathway, with bicarbonate serving as a hydroxyl radical scavenger.     

Removal of chloride from simulated acidic wastewater in the zinc production

The removal of chloride from the zinc electrolyte produced during hydrometallurgical zinc production is challenging. The ion-exchange method is a promising way to remove chloride if the resin washing wastewater can be recycled. This paper focuses on chloride removal from resin washing wastewater to enable its reuse.Various processing factors including the oxygen gas velocity, temperature, and reaction time were investigated systematically. The results show that the optimal conditions for dechlorination are an oxygen gas velocity of 0.5 L·min~(-1), a reaction temperature of 80 ℃, and a reaction time of 30 min. A dechlorination efficiency of 80% with a residual chloride ion concentration less than 200 mg·L~(-1) was achieved, which meets the requirements for the recycling of wastewater. The presence of manganese accelerates the dechlorination by forming a Mn~(2+)–MnO_2–MnO_4~-–Mn~(2+) redox cycle. In this process, about 15 kg of the MnO_2 and all of the zinc can be recovered from 100 m~3 wastewater, and the wastewater can be reused, which makes the ion-exchange method a promising technique for chloride removal.     

Contribution of free radicals to ozonation of spent reactive dyebaths bearing aminofluorotriazine dyes

Laboratory-scale ozonation of spent dyebath simulations bearing aminofluorotriazine-type reactive dyes was investigated. It was particularly aimed at interpreting the kinetic behaviour of ozone by applying a simple fractional hydroxyl radical scavenger (carbonate/bicarbonate alkalinity) test at varying pH in the absence and presence of sodium carbonate. Complete decolorisation (first-order decolorisation rate constant k _D, 0.5–1.0 1/min at λ 436 nm) as well as partial mineralisation (TOC removal, 5–9%) and dearomatisation (UV₂₅₄ removal, 55–83%) could be achieved after 1 h of ozonation, whereas detoxification was only improved from ED₂₀ 30 to 53%. This study demonstrated that in the presence of sodium carbonate, neither molecular ozone nor hydroxyl radicals play an important role in dye oxidation. It has been proposed that other free radicals (carbonate or bicarbonate radicals) might be the dominant oxidising agents.     

Optimization of High-Strength Semiconductor Wastewater by Sequential Fenton Oxidation and Gas-Induced Ozonation

Treatment of organic-containing wastewater from a semiconductor plant treated by chemical oxidation was experimentally investigated. The wastewater was characterized by strong color, high chemical oxygen demand (COD) and low biodegradability. Treatment of this wastewater by traditional activated sludge method was essentially impossible. In the present work, advanced chemical oxidations by Fenton’s reagent and ozonation were utilized to tackle the problems of wastewater color and low biodegradability. To facilitate the particulate removal after Fenton oxidation, chemical coagulation using polyaluminum chloride and polymer was adopted as an integral part of the Fenton process. Experimental tests were conducted to determine the effectiveness and the optimum operating conditions of the chemical oxidation methods. Test results demonstrate that the two advanced oxidations were able to lower the wastewater COD concentration from as high as 15,000 mg/L to below 150 mg/L and completely eliminating the wastewater color, resulting in very good quality of the treated wastewater. A generalized kinetic model was employed to describe and elucidate the oxidation mechanisms of oxidation processes and the kinetic parameters of the models were appropriately identified using the test data.     

Evaluation of O3/UV and O3/H2O2 as Practical Advanced Oxidation Processes for Degradation of 1,4-Dioxane

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.     

Electrochemical treatment of ammonia in wastewater by RuO<Subscript>2</Subscript>–IrO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript>/Ti electrodes

This study investigated the removal of ammonia in wastewater by an electrochemical method using titanium electrodes coated with ruthenium and iridium (RuO₂–IrO₂–TiO₂/Ti) with low chlorine evolution over-voltage. The effects of operating parameters, including chloride ion concentration, current density and initial pH, were also investigated. The results were evaluated primarily by considering the efficiency of the elimination of NH₄⁺-N. The removal of ammonia by electrochemical oxidation mainly resulted from the indirect oxidation effect of chlorine/hypochlorite produced during electrolysis. The direct anodic oxidation efficiency of ammonia was less than 5%, and the current efficiency was less than 10%. The ammonia removal followed pseudo-first-order kinetics. The electrochemical process can be applied successfully as a final polishing step, or as an alternative method to biological nitrification. The process seems to be most beneficial for small coastal cities     

某些物质对亚硫酸盐氧化的阻滞作用

通过除氧试验和空气氧化试验,了某些物质对亚硫酸盐氧化的阻滞作用,结果发现,下列三类物质够阻滞亚硫酸盐与氧的反应;第一类物质是自由基链反应终止剂,通过消除亚硫酸盐氧化过程中生成的自由基而抑制反应;第二类物质是螯合剂,通过螯合亚硫酸盐溶液中的过渡族金属元素催化剂杂质的而减缓反应速度;第三类物质是链反应引发剂,早于添加过量而由引发剂转变为终止剂,试验结果为亚硫酸直氧化的自由基机理提供了有力的证据,也为防     

Ozone,Hydrogen Peroxide/Ozone And UV/Ozone Treatment Of Chromium- And Copper-Complex Dyes: Decolorization And Metal Release

Metal-complex azo dyes constitute a significant fraction of the dyes used in the textile industry and exhibit properties such as superior light- and wash-fastness. While effluent color is not always regulated, the textile finishing industry often decolorizes wastewater using processes including chemical oxidation. In this study, the use of ozone, hydrogen peroxide/ozone and UV/ozone oxidant systems was examined for treatment of two common metal-complex (premetalized) dyes, Acid Black 52 (chromium) and Direct Blue 80 (copper). Oxidant dosages required for decolorization of these dyes were determined. The effect of bicarbonate alkalinity on the ozonation and the hydrogen peroxide/ozone processes also was examined.     

电化学氧化法处理高浓度氨氮废水的研究

采用间歇试验的方法对电化学氧化处理模拟高浓度氨氮废水的影响因素进行研究。分别考察了电流密度、极板间距、氯离子浓度、反应初始pH值对氨氮和总氮去除率的影响。试验结果表明,电化学氧化法去除氨氮和总氮的最佳电流密度为80mA/cm2,极板间距为30mm,氯离子质量浓度为7000mg/L,pH值为9～11。在上述条件下,反应7h,总氮的质量浓度从3000mg/L降到379.4mg/L,去除率达到87.35%。电化学氧化法对总氮的去除基本符合一级反应动力学规律。     

Paired electrooxidative degradation of phenol with in situ electrogenerated hydrogen peroxide and hypochlorite

The oxidants, hydrogen peroxide and hypochlorite, were generated by the cathodic reduction of oxygen and anodic oxidation of chloride ion in a paired electrolysis process and used for phenol degradation. The degradation of phenol with electrogenerated hydrogen peroxide was slightly affected by pH and ferrous ion concentration. The oxidative degradation of phenol with paired electrogenerated hydrogen peroxide and hypochlorite was significantly affected by phenol concentration. In comparison with the cathodic and anodic degradation of phenol, the removal of phenol increased by 56.1 and 178.1%, respectively, in the case of paired electrooxidative phenol degradation. The COD decreased from 3222 and 3222 ppm to 2253 and 2746 ppm in the anodic and cathodic compartments when the charge passed increased from 0 to 2500C.     

FeOOH/H2O2体系去除水中对氯硝基苯

引言国内外的研究表明,常规的混凝、沉淀、过滤等水处理工艺对大量有机污染物特别是溶解态有机物的去除率甚微,仅能达到20%～30%[1],随着水质标准的不断提高,寻找新型有效的深度处理技     

Ozonation and Advanced Oxidation Treatment of Emerging Organic Pollutants in Water and Wastewater

A vast number of persistent organic pollutants have been found in wastewater effluent, surface water, and drinking water around the world. This indicates their ineffective removal from water and wastewater using conventional treatment technologies. In addition to classical persistent organics such as organochlorine insecticides, solvents, and polychlorinated biphenyls, a growing number of emerging pollutants of both synthetic and natural origins have been identified as major environmental pollutants in recent years. A variety of advanced and conventional treatment options have been suggested for the removal and/or destruction of these persistent organics in water and wastewater, such as chemical oxidation, activated carbon adsorption, and membrane filtration. Of these options, chemical oxidation using ozone, alone or in combination with additional physical/chemical agents (i.e., advanced oxidation), has been proved a highly effective treatment process for a wide spectrum of emerging aqueous organic pollutants, including pesticides, pharmaceuticals, personal care products, surfactants, microbial toxins, and natural fatty acids. In this paper, we discuss the emerging organic pollutants of concern in the aquatic environment and focus on the issues associated with their removal using ozonation and advanced oxidation processes.     

生物质水解发酵废水中钙离子的去除研究

采用二氧化碳与助剂A联合法对生物质水解发酵废水中Ca~(2+)的去除进行了研究.研究表明.在助剂A的作用下,pH为9～10时,对Ca~(2+)的去除效果较好,去除规律符合线性相关.同时.体系中的碳酸氢盐碱度和总碱度增长较大,为后续厌氧处理提供了良好的条件.     

腈纶废水生化处理脱氮影响因素研究

针对聚氨酯泡沫微生物固定化载体的序批式生物膜反应器(SBBR),通过平行对比实验,考察生物脱氮过程中DO、碱度、温度、C/N等因素对实际腈纶废水的处理效果及影响,结果表明:在进水pH=8,DO在2~4 mg/L,投加碳酸氢钠0.4 g/L,温度为32℃,HRT为48 h的条件下,COD去除率可达到65%以上,氨氮去除率达99%以上。     

Oxidation Of Iron And Manganese By Ozone

The oxidation of iron and manganese by ozone was studied in the laboratory. Model waters both with and without organic matter were used. Results showed iron to be very rapidly oxidized to an insoluble form in the absence of organic matter. However, in the presence of organic matter the iron was protected from oxidation by ozone and precipitation. The degree to which this occurred depended on the nature of the organic matter and the chemical environment at the time of mixing the iron stock and the dissolved organic matter.

Experiments with manganese allowed the determination of second order rate constants for the reaction of ozone with manganese at various pH values. The oxidation of manganese in the presence of organic matter occurred in competition with oxidation of the organic matter. As a result, high ozone doses were required to achieve the same degree of removal of manganese. An increase in bicarbonate alkalinity from 50 mg/L to 200 mg/L did not result in an acceleration of the manganese oxidation in the absence of organic matter. However, in the presence of organic matter, higher levels of bicarbonate created conditions that resulted in more complete oxidation of the manganese following total consumption of the dosed ozone.     

Comparative study of copper behaviour in bicarbonate and phosphate aqueous solutions and effect of chloride ions

Copper oxidation in aqueous solutions of pH 8 showed some differences in the presence of bicarbonate and phosphate ions. The bicarbonate ions did not interfere with Cu₂O film formation but the Cu²⁺ ions were stabilized by the complexing action of CO _2– ³ anions. In phosphate solutions, copper dissolved in the range of potentials associated with the Cu(I) oxidation state and the Cu(II) compound on the surface resulted in an extensive passivation region. In both solutions, a higher ion concentration caused an increase in the anodic current, suggesting that the copper ions were stabilized by the complexing action of the electrolyte. The copper oxidation current in a bicarbonate solution was higher than that observed in a phosphate solution of the same concentration. The thickness of the Cu(II) film rather than the Cu(I) layer appears to be the important factor related to the stability of the passive layer on the copper surface. The shift in the breakdown potential toward more positive values indicates that both bicarbonate and phosphate ions inhibit localized corrosion due to the presence of chloride ions. Their protective effect depends on the concentration of each anion, although the concentration of chloride ions necessary for pitting is larger in phosphate solutions than in bicarbonate solutions. In both solutions, long-term immersion of copper under anodic polarization results in the precipitation of a protective coating.