Application of Ozone Involving Advanced Oxidation Processes to Remove Some Pharmaceutical Compounds from Urban Wastewaters

Different UVA radiation and advanced oxidation systems, most of them involving ozone, have been applied to remove mixtures of three contaminants of pharmaceutical type: diclofenac (DCF), sulfamethoxazole (SMT) and caffeine (CFF), both in ultrapure and secondary treated wastewater. The influence of the water matrix has been studied in terms of individual compound concentration and TOC removal. Also, biodegradability of the treated wastewater before and after the advanced oxidation process, as BOD/COD ratio, the partial oxidation yield, the increment of average state of carbon oxidation and ozone consumption have been determined. For mgL^?1 to 100 μgL^?1 concentrations and regardless of the ozone process and water type, DCF and SMT are removed in less than 10 min mainly by direct reaction with ozone, especially in the case of DCF. CFF, on the contrary, is mainly removed through hydroxyl radicals. For lower concentration (≤100 μgL^?1), DCF still disappears by direct ozonation, CFF by hydroxyl radicals oxidation and SMT through both direct ozonation and hydroxyl radical oxidation. Once DCF and SMT have disappeared, TOC is removed by reacting with hydroxyl radicals, regardless of the water matrix. Photocatalytic ozonation allows the highest TOC degradation rate, partial oxidation yield, increment of average state of carbon oxidation and biodegradability together to the lowest ozone consumption per mg TOC eliminated.     

Effect of Ozonation on Biodegradability Characteristics of Surplus Activated Sludge

The study investigates the effect of sludge ozonation on solid matter species, disintegration properties, sludge components, and solubilization characteristics under different operating conditions. Ozonation of surplus activated sludge samples taken from the secondary settling tank of a domestic wastewater treatment plant indicates that soluble nitrogen, phosphorus and COD concentrations proliferate as a consequence of extending the ozone feeding time. A steady increase both in soluble nitrogen concentration and ratio of organic phosphorus to soluble phosphorus is observed through ozonation where specific ozone doses range between 4 and 11 mg O₃/g SS. Combined treatment of chemical oxidation and aerobic biodegradation to surplus activated sludge is also applied to improve the biodegradability of organic matter by partial chemical oxidative pretreatment with as little specific ozone consumption as possible. The partial oxidation by integrated ozonation is operated as a pre-oxidation step for the subsequent biological degradation, due to the fact that the competition with biological degradation in removing biodegradable organic compounds is avoided and most probably a more biodegradable sludge composition is obtained by means of ozonation. Combined treatment of chemical oxidation and aerobic biodegradation conducted to scrutinize the synergic effect of the coupled treatment system reveals that TS and COD removal efficiencies of ozonated sludge samples cannot be improved beyond the third aerobic biodegradation step.     

Effect of Catalytic Ozonation Coupling with Activated Carbon Adsorption on Organic Compounds Removal Treating RO Concentrate from Coal Gasification Wastewater

This paper reports a novel system of catalytic ozonation coupling with activated carbon adsorption for removing the organic compounds treating in the RO concentrate from coal gasification wastewater. The effect of ozone dosage, catalyst dosage, reaction time, influence pH, and temperature on organic compounds removal were examined for the processes. In the catalytic ozonation process, increasing solution pH, dosages ozone, and catalyst were statistically significant for improving the performance. In addition, the high salinity with chloride concentration of 15 g/L could reduce the catalyst specific surface area by 18%. Thus, high salinity showed negative influence on the catalytic effect in TOC removal. Regarding activated carbon adsorption process, modified activated carbon by NaOH revealed advantages in adsorbing organic compounds treating catalytic ozonation effluent. With the ozone dosage of 120 mg/L, catalyst dosage of 2.0 g/L, catalytic ozonation reaction time of 1 h, and modified activated carbon adsorption time of 1 h, the average TOC removal efficiencies were maintained at the stable level of 58% with the TOC concentration of 26 mg/L.     

Biodegradability Improvement of Aqueous 2,4-Dichlorophenol And Nitrobenzene Solutions By Means of Single Ozonation

The possibility of the integration of ozonation and biological processes as an economical way to treat biorecalcitrant organic compounds such as nitrobenzene and 2,4-dichlorophenol was investigated. In the pre-treatment step, stoichiometric coefficients and pseudo first-order kinetic constants were obtained. Biodegradability was monitored throughout the ozonation step, in order to evaluate the optimum ozone doses. The low TOC reduction after these ozone doses allowed much of the organic carbon to be removed in the biological stage. In the case of 2,4-dichlorophenol, the biodegradability improvement was checked in an aerobic bioreactor. By means of the combined ozonation-biological oxidation, up to 80% of the initial organic content was removed. Results presented in this study show the feasibility of using the combination of ozone and conventional biological treatments to treat wastewaters containing these pollutants.     

Application of Ozonation to Dyeing Wastewater Treatment—Case Study in Nishiwaki Treatment Plant

Three treatment methods, raw wastewater (RW)?→?coagulation?→?biological treatment (RCB), RW→?pre-ozonation?→?biological treatment (ROB) and RW?→?biological treatment?→?post-ozonation (RBO), were investigated to clarify their effectiveness in treating dyeing wastewater from a treatment plant. The decrease in dissolved organic carbon (DOC) was in the following order: RCB?≥?RBO?>?ROB. DOC removal of 200 mg/L by biological treatment of RW was clearly higher than that of 12 mg/L by ozonation. On the other hand, only DOC removal of 108 mg/L was observed by biological treatment in RW after ozonation. The decrease in biological oxygen demand (BOD₅) was in the following order: ROB?≥?RCB?>?RBO. Because of the enhancement of biodegradability brought about by ozonation, BOD₅ after ozonation in RBO was higher than that of RW after biological treatment. Color was effectively removed by ozonation for both RW and RW after biological treatment, and the decrease in color was in the following order: RBO?>?ROB?≥?RCB. Adsorbable organic halide formation potential (AOXFP) and toxicity unit (TU15, exposure time is 15 min) were more effectively decreased by biological treatment than by coagulation or ozonation, although the differences among RCB, ROB and RBO were very small.     

Toxicity and Biodegradability Behavior of Xenobiotic Chemicals Before and After Ozonation: A Case Study with Commercial Textile Tannins

Ozonation of a natural tannin (NT; COD_o?=?1195 mg/L; TOC_o?=?342 mg/L; BOD_5,o?=?86 mg/L) and a synthetic tannin ST; COD_o?=?465 mg/L; TOC_o?=?55 mg/L; BOD_5,o?=?6 mg/L) being frequently applied in the polyamide dyeing process was investigated. Synthetic wastewater samples containing these tannins individually were prepared and subjected to ozonation at varying ozone doses (625– 1250 mgO₃/L wastewater), at pH?=?3.5 (the application pH of tannins) and pH?=?7.0 at an ozone dose of 1125 mgO₃/L wastewater. The collective environmental parameters COD, TOC, BOD₅, UV₂₅₄ and UV₂₈₀ (UV absorbance at 254 nm and 280 nm, representing aromatic and unsaturated moieties, respectively) were followed during ozonation. Changes in the biodegradability of the tannins were evaluated in terms of BOD₅ measurements conducted before and after ozonation. In addition, activated sludge inhibition tests employing heterotrophic biomass were run to elucidate the inhibitory effect of raw and ozonated textile tannins towards activated sludge biomass. Partial oxidation (45% COD removal at an ozone dose of 750 mg O₃/L wastewater and pH?=?3.5) of ST was sufficient to achieve elimination of its inhibitory effect towards heterotrophic biomass and acceptable biodegradability improvement, whereas the inhibitory effect and biodegradability of NT could not be reduced via ozonation under the same reaction conditions.     

Enhancement in mineralization of some natural refractory organic compounds by ozonation–aerobic biodegradation

Two schemes, the first involving ozonation followed by final aerobic biodegradation (phase I experiments), and the second involving initial aerobic biodegradation, followed by ozonation and subsequent final aerobic biodegradation (phase II experiments), were examined for enhanced mineralization of refractory model compounds, viz. gallic acid, tannin and lignin. In all cases, and irrespective of the applied scheme, chemical oxygen demand (COD), total organic carbon (TOC), COD/TOC ratio, and specific UV absorbance at 280 nm attributed to the model compounds decreased with application of increasing ozone dose. The residual organic matter remaining after ozonation exhibited enhanced aerobic biodegradability in all cases. Further, in all cases and irrespective of the applied scheme, the overall amount of COD and TOC removed through the combination of ozonation and biodegradation processes increased with increase in ozone dose for all three model compounds, and more than 90% COD removal could be achieved with an ozone dose of 3 mg ozone absorbed per mg initial TOC, as compared with approximately 40% COD removal when no ozone was applied. Treatment by the first scheme resulted in the fraction of starting COD removed through biodegradation decreasing with increase in ozone dose in all cases, while this fraction increased or remained constant during treatment using the second scheme. In the case of tannin and lignin, similar overall COD removal could be achieved at lower ozone doses using scheme II. Due to incorporation of the initial aerobic biodegradation step in scheme II, the ozone requirement for additional mineralization, ie mineralization over and above that achieved by aerobic biodegradation, was also lower than that in scheme I. Copyright © 2005 Society of Chemical Industry     

Effect of Ozone on Removal of Dissolved Organic Matter and its Biodegradability and Adsorbability in Biotreated Textile Effluents

A study was conducted on the efficacy of ozonation in removing dissolved organic matter (DOM) in biotreated textile effluents and effects on its biodegradability and adsorbability. Results showed the efficient removal of color and fluorescence compounds were achieved through ozonation, due to increasing hydrophilicity and lowering molecular weight of DOM. A significant biodegradability improvement was also observed, and DOM adsorbability on activated carbon was highly dependent on ozone dosage. As the key parameter, consumed 3.8 g O₃/?g TOC₀ was the optimal dosage in the hybrid process combining ozonation with biological activated carbon (BAC) for wastewater reclamation.     

Incidence of an Ozonation Stage on the Treatment of Cherry Stillage by Activated Sludge

This article presents a laboratory study of the ozonation of diluted cherry stillage, a high-strength wastewater. Influence of variables, kinetics, and the effects of an ozonation stage coupled with the biological treatment by activated sludge are addressed. Single activated sludge processing was shown effective to remove biological oxygen demand (BOD) and chemical oxygen demand (COD) but polyphenols were reduced to a lesser extent. On the other hand, direct wastewater ozonation did not reduce COD and total organic carbon (TOC) appreciably, and foaming problems were experienced when a high gas flow rate was applied. However, polyphenols and UV₂₅₄ absorbance decreased substantially by means of ozonation. To best achieve complete cherry stillage purification, two ways of coupling ozonation with activated sludge are proposed. Ozonation prior to activated sludge is advised for high-concentration wastewater to reduce polyphenol concentration, thus removing inhibiting effects. For wastewater with low polyphenol concentration the sequence activated sludge–ozonation–activated sludge is preferred to enhance the overall process performance in terms of oxidation efficiency and sludge settling.     

Integrated Wet Air Oxidation and Biological Treatment of Polyethylene Glycol-Containing Wastewaters

The treatment of a model wastewater containing polyethylene glycol (PEG) of molecular weight 10000 in an integrated wet air oxidation–aerobic oxidation process was investigated. Partial wet air oxidation under mild operating conditions was capable of converting the original polymer to lower molecular weight compounds, such as oligomers and short-chain organic acids. The effect of molecular weight on the aerobic biodegradability of polyethylene glycol was assessed by performing shake flasks experiments with various polyethylene glycols in a molecular weight range from 200–35000 and it was found that biodegradability generally decreased with increasing molecular weight. Aqueous solutions of PEG 10000 were subjected to continuous wet air oxidation at a temperature of 423 K and a residence time of 30 min and the oxidised effluents were then subjected to subsequent continuous aerobic oxidation at residence times varying between 0·5 and 4 days. Simultaneously, continuous aerobic oxidation experiments on solutions of PEG 10000 were performed and used to compare the efficiency of the integrated treatment process with that of the direct biological treatment. Partial pretreatment by wet air oxidation under mild operating conditions resulted in effluents whose biodegradation rates were significantly higher than those of the original, unoxidised wastewater, as assessed by total organic carbon (TOC) removal rates. The original wastewater was practically non-biodegradable at a 0·5-day residence time with direct biological treatment, while an 80% TOC removal was achieved when biological treatment was coupled with a preceding wet air oxidation step. Conversely, with a 4-day residence time for the direct biological treatment the original wastewater was only partially degradable with 60–70% TOC removal recorded; with the integrated treatment process at a 4-day residence time in the bioreactor the overall TOC removal was greater than 90%. © 1997 SCI     

Remediation of Kraft Effluent by Ozonation: Effect of Applied Ozone Concentration and Initial pH

In this study, the impact of ozone concentration (14 and 7mg/L^?1 applied for 120min) and pH (10 and 12) on color removal, and reduction of dissolved organic matter (DOC) and total phenol of Kraft E₁ effluent was investigated. The degradation kinetics for the all parameters at pH 12 were slower than of those at pH 10. The degradation at pH 10 ceased after approximately 120min, while for the ozonation at pH 12, ozone was still being consumed even after 5h of treatment. When the ozone dose was increased, the removal efficiency increased; however, the DOC removal efficiency continued limited.     

A Comparative Study: Degradation of 2,5-Dichlorophenol in Wastewater and Distilled Water by Ozone and Ozone-UV

The effectiveness of ozone and ozone-UV processes on effluents containing chlorophenol was evaluated. Experiments were performed using 3.06 mM of 2,5-dichlorophenol in distilled water and wastewater at pH 7 with ozone dose of 37 mg/L. An ozone dose of 1.2 g/h was effective in completely degrading 2,5-dichlorophenol and reducing the toxicity of its by-products. Overall, ozone-UV process was more effective in the oxidation of 2,5-DCP. Ozone-UV treatment of wastewater showed the highest mineralization (53%), dechlorination (100%), COD removal (75%), and biodegradability (BOD₅/COD = 0.85). The organic/inorganic matters in wastewater seem to have a positive effect on the oxidation of 2,5-DCP and supports the use of ozone and ozone-UV processes for industrial effluent treatment.     

预臭氧化过程水样可生化性的简易评估方法

研究了几种生化难降解有机物在预臭氧化过程可生化性（BOD₅/COD_Cr,即5天生化需氧量与化学耗氧量的比值）的变化情况,并提出了一个氧化度（即有机物的氧化程度,定义为：（4TOC-COD_Cr）/4TOC,其中TOC为总有机碳）的概念。结果表明,在预臭氧化硝基苯、邻苯二甲酸二甲酯和磺基水杨酸模拟水样过程中,水样的氧化度和可生化性均有不同程度的提升,而且两者存在一定的正相关性。当体系氧化度大于0.65时,水样的BOD₅/COD_Cr一般均在0.2以上,可直接进行生化处理。对某酸性化工废水进行了预臭氧化处理（Ti（Ⅳ）/H₂O₂/O₃）,120 min后COD_Cr和TOC的去除率分别达到了66.09%和34.09%,此时水样的氧化度从原来的0.346升至0.664,BOD₅/COD_Cr值从原来的0.05升至0.332,显示了较好的正相关性。利用易测的氧化度来预判水样的可生化性,这对推广预臭氧化技术在实际难降解废水处理中的应用具有重要的实际意义。     

Impact of ozonation on subsequent treatment of azo dye solutions

BACKGROUND: Aqueous solutions of four azo‐dyes, Acid Red 14 (AR14), Congo Red (CR), Reactive Black 5 (RB5), and Reactive Violet 5 (RV5) were treated with ozone, and the impact of ozonation on their subsequent treatability by aerobic biodegradation processes was investigated. RESULTS: In all cases, ozonation at the highest ozone doses investigated could remove more than 96% of the original dye, and the corresponding residual colour of the azo dye solutions declined to less than 20 on the Pt‐Co scale. Ozonation also resulted in reduction of chemical oxygen demand (COD), total organic carbon (TOC) the COD/TOC ratio and pH, while in all cases electrical conductivity of the dye solutions increased. Activity of the microbial colonies present in domestic wastewater was not inhibited when un‐ozonized solutions of these dyes were mixed in a 1:1 volumetric ratio with domestic wastewater, although the dyes themselves were not degraded. Also, no significant inhibition of microbial activity was observed in 1:1 mixtures of ozonized dye solutions and domestic wastewater, especially when the initial dye concentration was low and the applied ozone dose was high. In almost all cases, progressively enhanced BOD exertion was observed in mixtures containing dye solutions ozonized with progressively higher doses. This indicated that some ozonation by‐products of the above dyes could be degraded by microorganisms present in domestic wastewater. CONCLUSIONS: It was concluded that the above dye solutions, after ozonation for partial or complete colour removal, could be mixed with domestic wastewater for subsequent treatment by aerobic biological processes, with no adverse impact on the activity of the microbial colonies present in domestic wastewater. Copyright © 2007 Society of Chemical Industry     

Ozonation of NSAID: A Biodegradability and Toxicity Study

This work deals with the biodegradability and toxicity of three non-steroidal anti-inflammatory drugs (NSAID) (diclofenac, ibuprofen and naproxen) treated by ozonation. The results show that the total removal of 200 mg L^?1 of diclofenac and 100 mg L^?1 of naproxen is possible using an ozone dose of 0.20 and 0.04 g L^?1, respectively. For 200 mg L^?1 of ibuprofen, 90% removal is achieved using an ozone dose of 2.3 g L^?1. The BOD₅/COD ratio, the Zahn-Wallens test and EC₅₀ toxicity test (Microtox) are chosen as biological and toxicity indicators of NSAID intermediates. The evolution of BOD₅/COD ratio during 1 hour of treatment is evaluated and the results show that ozonation improves the biodegradability for the three NSAID treated solution. The Zahn-Wellens test for diclofenac and ibuprofen solutions shows that biological mineralization, after 28 days, is higher for diclofenac than for ibuprofen solution. According to the Microtox test, the treatment with ozone removes the toxicity of the naproxen solution. Taking into account the results obtained with the biocompatibility tests it could be assumed that ozonation is an adequate treatment for removal NSAID in aquatic medium, and the ozonated effluents could be post-treated in a biological wastewater facility.     

Ozonolysis Of Humic Acid And Its Effect On Decoloration And Biodegradability

The objectives of this research were to investigate the reactivity of humic acid (HA) with ozone and to evaluate its effect on decoloration and biodegradability. Reagent HA was selected as a target compound, and the change in overall water quality parameters, molecular weight distribution, color and biodegradability during ozonation were investigated. Partial oxidation such as decoloration was observed, though the complete destruction represented by TOC removal was not significant. The rate of ozone usage decreased as the reaction proceeded. Degradation to the lower molecular weight fragments was confirmed by ultrafiltration. The close relationship between color and fragmentation was verified. Decoloration was represented by a pseudo-first order reaction. Formic, acetic, oxalic and glyoxylic acids were identified by HPLC and ion chromatography as typical low molecular weight organic acids. The biodegradability of ozonated HA solutions, represented in terms of the ratio of BOD₅ to TOC, was improved.     

Ozonation of a Complex Industrial Effluent: Oxidation of Organic Pollutants and Removal of Toxicity

This work deals with the ozonation of a chemical industry wastewater, which contains many complex organic pollutants and presents high chloride content and toxicity. Batch experiments were carried out until ozone absorption reached 0.1 to 3 gO₃/L. Ozonation promoted low to moderate levels of organic matter removal even when high ozone doses were applied. Organic matter removal tended to decrease when chloride content increased. Toxicity removal increased with the ozone dose up to 0.5 gO₃/L. High or complete toxicity removal was attained after ozonation of the wastewater samples. Ozonation was also very effective in removing the polycyclic aromatic compounds found in the wastewater.     

Catalytic Ozonation of Sulfosalicylic Acid

The investigation of heterogeneous catalytic ozonation of sulfosalicylic acid (SSal) in aqueous solution is reported in this paper. It was found that catalytic ozonation in the presence of V-O supported on silica gel had a more positive effect on the removal rate (62% in 30 min) of total organic carbon (TOC) than that of ozonation alone (20% in 30 min), and the catalyst supported on TiO₂ had similar results. The experimental results also showed that the ozone dosage should be sufficient for achieving the catalytic effect. Efficient removal of TOC in catalytic ozonation was probably attributed to producing more powerful oxidants than molecular ozone.     

Removal Characteristics of Organic Pollutants in Sewage Treatment by a Pre-Coagulation,Ozonation and Ozone/Hydrogen Peroxide Process

The applicability of a sequential process of ozonation and ozone/hydrogen peroxide process for the removal of soluble organic compounds from a pre-coagulated municipal sewage was examined. 6–25% of initial T-COD_Cr was removed at the early stage of ozonation before the ratio of consumed ozone to removed T-COD_Cr dramatically increased. Until dissolved ozone was detected, 0.3 mgO₃/mgTOC₀ (Initial TOC) of ozone was consumed. When an ozone/hydrogen peroxide process was applied, additional COD_Cr was removed. And we elucidated that two following findings are important for the better performance of ozone/hydrogen peroxide process; those are to remove readily reactive organic compounds with ozone before the application of ozone/hydrogen peroxide process and to avoid the excess addition of hydrogen peroxide. Based on these two findings, we proposed a sequential process of ozonation and multi-stage ozone/hydrogen peroxide process and the appropriate addition of hydrogen peroxide. T-COD_Cr, TOC and ATU-BOD₅ were reduced to less than 7 mg/L, 6 mgC/L and 5 mg/L, respectively after total treatment time of 79 min. Furthermore, we discussed the transformation of organic compounds and the removal of organic compounds. The removal amount of COD_Cr and UV₂₅₄ had good linear relationship until the removal amounts of COD_Cr and UV₂₅₄ were 30 mg/L and 0.11 cm^?1, respectively. Therefore UV₂₅₄ would be useful for an indicator for COD_Cr removal at the beginning of the treatment. The accumulation of carboxylic acids (formic acid, acetic acid and oxalic acid) was observed. The ratio of carbon concentration of carboxylic acids to TOC remaining was getting higher and reached around 0.5 finally. Removal of TOC was observed with the accumulation of carboxylic acids. When unknown organic compounds (organic compounds except for carboxylic acids) were oxidized, 70% was apparently removed as carbon dioxide and 30% was accumulated as carboxylic acids. A portion of biodegradable organic compounds to whole organic compounds was enhanced as shown by the increase ratio of BOD/COD_Cr.     

Enhancing Biodegradability of Textile Wastewater by Ozonation Processes: Optimization with Response Surface Methodology

ABSTRACT

In this study, an ozonation process was used to increase biodegradability of textile wastewater by considering chemical oxygen demand (COD) and color removal. Response surface methodology was applied in order to determine the significance of independent variables which are initial pH, reaction time and ozone dose. While a biological oxygen demand (BOD)/COD rate of 0.315 was obtained at optimum conditions, which are pH 9, 75 min of reaction time and 26 mg/L ozone dose, color and COD removal was obtained at 74% and 39%, respectively. BOD/COD ratio value increased from 0.18 to 0.32 by ozonation process. In addition, k coefficient for BOD also increased from 0.21 to 0.30 d^?1.