Optimum Ozone Dosage of Preozonation and Characteristic Change of Refractory Organics in Landfill Leachate

Preozonation on landfill leachate was carried out. COD removal rate has an obvious inflection at ozone dosage 0.186 mg_O3/mg_COD in ozonation process. Seven sets of identical O₃-SBR combined process under different ozone dosages were studied. The results indicated that the best COD removal rate of synergetic effect is also at 0.186 mg_O3/mg_COD. New organic substances produced after ozonation was confirmed by an excitation-emission matrix (EEM). Carbon dioxide production increased from 36.3 mg to 75.7 mg after ozonation, confirming that biodegradability of refractory organics in landfill leachate was enhanced. All the arguments indicated that the inflection point of COD removal by ozonation has a great significance for preozonation.     

Degradation of methylene blue in aqueous solution by ozone-based processes

The aim of this study was to compare the efficiency of conventional ozonation and catalytic ozonation (ozone/activated carbon (O₃/AC) and ozone/TiO₂/activated carbon (O₃/TiO₂/AC)) in the degradation of methylene blue (MB) component from MB aqueous solution. The removal rates of color and chemical oxygen demand (COD_Cr) were assessed to screen the most appropriate oxidative process of MB treatment. In this experiment conditions, the color was completely disappeared in the presence of TiO₂/AC catalyst, after 40 min of reaction time. However, only ozone system still existed 11.8% MB in aqueous solution, while in case of O₃/AC system MB of 4.6% was not removed. In the COD removal experiment, the catalytic ozonation process showed a superior performance, compared to that of the conventional ozonation. COD removal efficiency was significantly promoted in the presence of catalysts such as AC and TiO₂. O₃/TiO₂/AC was found to be the most effective approach to eliminating the color and enhancing COD removal efficiency. The catalyst of TiO₂/AC was characterized by using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).     

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     

Application of Regression Analysis for Ozone and Catalytic Ozonation of Organic Compounds from Landfill Leachate with Ceramic Raschig Rings and Natural Manganese Ore

Treatment of landfill leachate could be improved by adding ceramic raschig rings and manganese ore as catalysts for ozonation. Regression analysis were carried out to assess effects of parameters (pH, reaction time, the amount of H₂O₂, the surface area of ceramic raschig rings and the amount of manganese ore) on removing organic compounds from landfill leachate by ozone alone, peroxone, ozone/ceramic raschig rings, peroxone/ceramic raschig rings, ozone/manganese ore and peroxone/manganese ore. Results showed that parameters of reaction time, the amount of H₂O₂ and the amount of manganese ore were the high effects on removal of organic compounds from landfill leachate, following by pH paremeter. Ceramic raschig rings did not have significant effect on color, COD and TOC removal.     

Post-Treatment of Pulp and Paper Industry Wastewater by Advanced Oxidation Processes

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, H₂O_2, 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.     

Oxidation of Aged Raw Landfill Leachate with O3 Only and O3/H2O2: Treatment Efficiency and Molecular Size Distribution Analysis

An aged raw landfill leachate was taken from the equalization storage tank at Clover Bar Landfill Leachate Treatment Plant, Edmonton, Alberta, Canada. The average quality parameters of this leachate were: COD=1,090mg/L, BOD₅=39mg/L, color=1,130 TCU, NH₃-N=455mgN/L, alkalinity=4,030mg/L as CaCO₃and pH=8.30. The major fraction of this leachate was large refractory organic compounds. Ozone (O₃) only and O₃ combined with hydrogen peroxide (O₃/H₂O₂) were applied to treat this leachate, aiming at enhancing COD and color reduction and increasing its biodegradability (i.e., the ratio of BOD₅/COD). All of the O₃ only and O₃/H₂O₂ oxidation experiments were performed in a gas washing bottle equipped with a fine bubble diffuser. The used ozone dose ranged from 1.2 to 12.5g O₃/L leachate for O₃ only treatment, and 1.8 to 13.8g O₃/L leachate for O₃/H₂O₂ treatment. H₂O₂ dose for O₃/H₂O₂ treatment was 0.63g H₂O₂/L leachate. COD, BOD₅, color, NH₃-N, nitrite+nitrate, and alkalinity were measured before and after treatment. Meanwhile the molecular size distribution of the leachate, before and after treatment, was analyzed by using a high-performance liquid chromatograph (HPLC) with gel filtration column and UV detector at 254nm. The addition of H₂O₂ had an insignificant effect (at 5% significance level) on enhancing COD and color reduction. After oxidation, the maximum BOD₅ increase was about 110% for O₃/H₂O₂ treatment and about 141% for O₃ only treatment at a used ozone dose of 3.6g O₃/L leachate and 2.6g O₃/L leachate for O₃/H₂O₂ and O₃ only, respectively. As the used ozone dose increased, NH₃-N and alkalinity decreased considerably, and nitrite+nitrate increased accordingly. Treatment efficiency models, which describe the changes in COD, BOD₅/COD, NH₃-N, nitrite+nitrate, and alkalinity as functions of the used ozone dose, were developed. Statistically (at 5% significance level), the treatment efficiency models for both treatments are not different. According to the results of molecular size distribution analysis, no correlation was observed between the BOD₅ increase and oxidation by-products’ formation.     

Ozonation as a Means to Optimize Biological Nitrogen Removal from Landfill Leachate

In this study, we investigate factors that can affect nitrification and denitrification in a moving bed biofilm system, treating partly stabilized landfill leachate. The optimization of biological treatment by means of controlled ozonation is additionally evaluated. Results obtained with a laboratory-scale, continuous-flow biofilm system suggest that nitrogen removal can be limited by the low influent biodegradable substrate concentrations, and that autotrophic nitrification can be adversely impacted by the high alkalinity buffer and ammonium/ammonia concentration. Our results suggest an optimum ozone dosage as high as 0.5 g/L O₃ can be required to effectively decrease the effluent soluble COD concentration and pH profile in the aerobic reactors, improve the biodegradable COD production from inert compounds, and induce chemical nitrification in the system. The specific cost of ozonation evaluated is 0.36–0.73 euro/m³ with 911 mg/L average effluent soluble COD measured in the biofilm system.     

Ozone/H2O2 Performance on the Degradation of Sulfamethoxazole

This work aims to analyze the contribution of H₂O₂ on ozonation of Sulfamethoxazole (SMX). A single ozonation was able to totally remove SMX. TOC and COD depletion rates after a transferred ozone dose of 60 mg/L was related to the formation and decomposition of H₂O₂. An increase on O₃ gas inlet concentration from 10 g/m³ to 20 g/m³ improved COD abatement from 11% to 36%. When the presence of H₂O₂ at the beginning of ozonation was tested, it was verified that COD and TOC degradation were enhanced, attaining maximum values of 76% and 32%, respectively, when compared with 35% and 15% reached in a single ozonation.     

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).     

Ozonolysis Post-Treatment of Anaerobically Digested Distillery Wastewater Effluent

ABSTRACT

In this study, the ozonolysis of real anaerobically digested distillery wastewater (DWW) was carried out. The effect of operating parameters, such as pH, initial concentration, and ozone dosage, on the efficiency of ozone utilization, color removal, and sludge solubilization was studied. The highest ozone utilization of 99% was observed at the highest initial concentration (COD of 3000 mg/L) and lowest ozone flowrate (22.5 mg O₃/L/min), but with a very low color reduction of 20%, after 60 minutes of ozonolysis. To achieve a higher color reduction >80% and at ozone utilization >95%, the DWW had to be diluted twice (COD 1500 mg/L), and the flowrate doubled to 45 mg O₃/L/min. The reduction in color signified the oxidation of the color causing biorecalcitrant aromatic melanoidin compounds. This was confirmed by the 47% reduction in ultraviolet absorbance at 254 nm indicating the breakdown of the complex aromatic compounds into low molecular weight organics. Moreover, increases in average oxidation state from ?0.6 to ?0.2 suggested a decline in aromaticity and formation of easily biodegradable aliphatic compounds. The ozonolysis process was found to follow the first-order reaction kinetic model with the highest rate constant of 0.0326 min^?1 obtained. A reduction in suspended COD by 88% indicated solubilization of the sludge contained in the effluent.     

Ceramic Raschig Rings—Improving Removal of Organic Compounds from Landfill Leachate by Perozone (O3/H2O2)

For improving the treatment of landfill leachate by combination O₃/H₂O₂, ceramic Raschig rings (CRR) with different surface areas were added to enhance mass transfer of ozone into liquid phase. To determine optimal conditions of reaction, pH and reaction time was also studied. The optimal pH range of 8–9, optimal reaction time of 80 min was identified in this research. CRR contribute to the significant improvement of efficiency of landfill leachate treatment by O₃/H₂O₂ systems. With added CRR of 728 m²/m³ surface area, color, COD and TOC removal was increased in comparison with experiment without CRR is 8%, 14%, and 9%, respectively. In this condition, the ozone utilization efficiency was also higher than that of experiment without CRR. Content of O₃ was also identified uses 3.441 kg O₃/kg COD.     

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.     

混凝—臭氧氧化处理垃圾中转站渗滤液的试验研究

以垃圾中转站渗滤液为研究对象,分析了混凝-臭氧氧化工艺对渗滤液COD和色度的影响。结果表明:在pH=11.2,FeCl_3加量为900 mg/L,臭氧反应时间为20 min,臭氧流量为35 mg/L的优化条件下,垃圾中转站渗滤液的COD、色度分别可去除78.39%与95.34,BOD5/COD由反应之前的0.152提升到了0.415,可生化性明显改善。     

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.     

The Ecoclear® Process. Results from Full-Scale Installations

Ecoclear® a heterogeneous catalytic ozonation process, has been in commercial operation since 1992 at an ozone consumption of 1.7 kg ozone per kg COD removed. Chlorinated hydrocarbon concentrations in contaminated groundwater are reduced to less than 10 μg/L. A second full scale installation was commissioned early in 1996 for leachate treatment. It is incorporated in the Biomembrat®-Plus process, a combination of biological treatment, nanofiltration and catalytic ozonation, at an ozone consumption of less than 1.0 kg ozone per kg COD removed.     

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).     

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     

Ozonation of Primary Sludge and Digested Sludge to Increase Methane Production in a Chemically Enhanced Primary Treatment Facility

The purpose of this research was the investigation of the ozonation of sludge as a method to improve anaerobic digestion performance in a chemically enhanced primary treatment facility. Batch tests were conducted to evaluate the effect of ozonation on the physicochemical characteristics of both primary and digested sludge. Then, the performance of semi-continuous anaerobic digesters in combination with ozone treatment was investigated (pre-ozonation and post-ozonation). Ozonation of primary sludge did not increase the soluble COD nor the biodegradable COD, but resulted in the mineralization of a fraction of the organic matter into CO₂. However, the ozonation of anaerobic digested sludge resulted in an increase in soluble COD and biodegradable COD and in a small level of mineralization at the dose of 90 mg O₃/g COD. Pre-ozonation of primary sludge was not effective in enhancing the performance of the anaerobic digester. The coupling of ozonation and anaerobic digestion by means of the post-ozonation of digested sludge was found to be effective in improving methane production (+16%), for COD removal efficiency and for the dewaterability of anaerobic digesters compared to the control digester.     

臭氧氧化处理渗滤液纳滤浓缩液的试验研究

采用臭氧为主工艺处理垃圾渗滤液纳滤浓缩液,试验结果表明:先通过混凝沉淀、臭氧氧化,再采用MBR处理,可取得良好的处理效果。当三氯化铁的投加量为2 kg/m3,PAM的投加量为0.1 kg/m3,絮凝时间在30~40 min,沉淀时间2~3 h的条件下,混凝沉淀COD的去除率为45%~60%;臭氧用量在25 g/h,水力停留时间为90 min左右,B/C比可提高至0.45;氧化后废水在MBR作用下出水COD为1000 mg/L左右,COD去除率为50%;如出水达到GB16889-2008标准限值的要求,需增加深度处理。     

Removal of a Toxic Anthraquinone Dye by Combination of Red Mud Coagulation and Ozonation

Removal of a toxic anthraquinone dye—Disperse Blue 56 (DB56) by single red mud (RM) coagulation, single ozonation and combined RM coagulation/ozonation (RM/O₃) was carried out in laboratory-scale experiments. RM/O₃ treatment exhibited more effective in toxicity removal, color removal and chemical oxygen demand (COD) reduction than the other two methods. The effect of several operational parameters, including initial dye concentration, pH value, RM coagulant dose and O₃ dose, on color removal and COD reduction was also investigated. Among these factors, pH value had the most important effect.