Ozonation of complex industrial park wastewater: effects on the change of wastewater characteristics

BACKGROUND: Ozonation of complex industrial park wastewater was carried out in a semi‐batch reactor. The variation of wastewater characteristics was evaluated based on the analysis of 5‐day biochemical oxygen demand (BOD₅) concentration, BOD₅/chemical oxygen demand (COD) ratio, COD fractionation, and dissolved organic carbon (DOC) molecular size distribution before and after ozonation. RESULTS: The experimental results indicated that low efficiency of COD removal with increasing tendency of BOD₅ concentration generally appeared after ozonation. Also, the BOD₅/COD ratio increased from an initial of 0.27 to a maximum of 0.38. The COD fractionation tests revealed that most of the inert soluble COD was transformed to biodegradable soluble COD at 30 min of reaction time. Additionally, the DOC molecular size distribution tests showed that the fraction larger than 500 kDa was significantly decreased and the fraction smaller than 2 kDa was increased when the reaction time was prolonged to 240 min. CONCLUSION: This study verified that partial oxidation of the complex industrial park wastewater by ozonation could enhance wastewater biodegradability. The biodegradability enhancement was primarily because the inert soluble COD fraction was converted to the biodegradable soluble COD and the high molecular weight fraction of DOC was shifted toward the low molecular weight fraction. Copyright © 2009 Society of Chemical Industry     

Experimental and theoretical study on catalytic ozonation of humic acid by ZnO catalyst

Ozonation and catalytic ozonation of humic acid (HA) in the presence of ZnO were examined in a batch scale reactor. The degradation of HA by catalytic ozonation was found to be much more effective than ozonation alone. The quantum chemistry calculations showed that the reaction of the O₃ disproportionation on the surface of ZnO corresponds to the barrierless mechanism. The activation energy of the transition state formation was ?5.25 eV. The active oxygen atom formed on the surface of ZnO was found as interacting with both water molecules and dissolved organic molecules, which might lead to further oxidizing reactions.     

Ozonation of the reactive dye intermediate 2‐naphthylamine 3,6,8‐trisulphonic acid (K‐Acid): kinetic assessment,ozonation products and ecotoxicity

Ozonation of the commercially important, recalcitrant reactive dye intermediate 2‐naphthylamine 3,6,8‐trisulphonic acid (K‐Acid) was investigated. Ozonation performance was examined by following ozone absorption rates and K‐Acid, chemical oxygen demand and total organic carbon removals. Mean oxidation states and unidentified organic products were also determined. At pH 3, where direct ozone reactions are dominant, the second‐order rate constant between K‐Acid and molecular ozone was determined as 20 m ^?1 s^?1 for steady‐state aqueous ozone concentration. The competition kinetics approach was also adopted where a reference compound, phenol, and K‐Acid were subjected to ozonation. By applying this method, the second‐order reaction rate constant was found to be 76 m ^?1 s^?1. Common oxidation products formed during ozonation at pH 3, pH 7 and pH 7 with 1 mm hydrogen peroxide were identified as methoxy‐phenyl‐oxime, phenol, benzene, benzaldehyde and oxalic acid via high‐performance liquid chromatography and gas chromatography/mass spectrometry analyses. Continuous nitrate and sulphate evolution were observed during K‐Acid ozonation as a consequence of the abrupt release and subsequent oxidation of its amino and sulphonate groups. The number and amount of reaction products were most intensive for K‐Acid ozonation at pH 7 with 1 mm hydrogen peroxide. According to the acute toxicity tests conducted with Vibrio fischeri, ozonation products were not less toxic than the original K‐Acid solution that caused only 15% inhibition.     

Ozone‐induced changes in natural organic matter (nom) structure

Hydrophobic organic acids (combined humic and fulvic acids), obtained from an Antarctic Lake with predominantly microbially derived organic carbon sources and two US river systems with terrestrial organic carbon sources, were ozonated. Several analyses, including ¹³C‐NMR, UV absorbance, fluorescence, hydrophobic/transphilic classification, and potentiometric titrations, were performed before and after ozonation. Ozonation reduced aromatic carbon content, selectively reducing phenolic carbon content. Ozonation of the samples resulted in increased aliphatic, carboxyl, plus acetal and ketal anomeric carbon content and shifted towards less hydrophobic compounds.     

Effect of Ozonation on Degradation of Organochlorine Compounds in Biosludge of Pulp and Paper Industry

The waste-activated sludge in the pulp and paper industry has been classified as hazardous waste due to the presence of organochlorine compounds. The fate of organochlorine compounds during ozonation of biosludge as well as subsequent treatment in activated sludge process has been studied. Ozonation of biosludge at 45.3 ± 2.1 mg O₃/g dry solid dosage resulted in 23 ± 2 and 26 ± 4% removal of adsorbable organic halides and extractable organic halides compounds, respectively. Out of 12 chlorophenolic compounds identified by USEPA for regulation, 10 compounds were detected in the biosludge and 19–68% removal of the individual compounds was observed during ozonation. High molecular weight chlorinated compounds were decomposed to low molecular weight ones with partial dechlorination. The ozonation followed by biological treatment can remove more than 80% of organochlorine compounds.     

Impact of extraction method on yield of lipid oxidation products from oxidized and unoxidized walnuts

The objective of this study was to measure and compare differences in oxidized products of oil extracted from unoxidized and oxidized walnuts using five different extraction methods: (i) mechanical pressing, or solvent extraction with (ii) hexane, (iii) methylene chloride, (iv) chloroform/methanol, or (v) supercritical carbon dioxide (SC−CO₂). Of the extraction methods evaluated, only chloroform/methanol and methylene chloride provided reasonable results for all parameters measured (total lipid yield, FA profile, PV, conjugated dienes, FFA content, and volatile content); however, chloroform/methanol extracted significantly greater levels of volatile compounds. The SC−CO₂ extraction with purified gas was simple and accurate for all data except collection of volatile compounds, as these materials are lost during the lipid extraction. Pressing was neither quantitative nor qualitative, and hexane extraction retrieved significantly lower levels of volatiles than the other methods, except for SC−CO₂.     

Integration of continuous biological and chemical (ozone) treatment of domestic wastewater: 1. Biodegradation and post‐ozonation

The continuous treatment of domestic wastewater by an activated sludge process and by an integrated biological–chemical (ozone) oxidation process were studied in this work. Chemical oxygen demand (COD), biochemical oxygen demand (BOD), absorbance at 254 nm (UV₂₅₄) and nitrogenous compound content were the parameters followed in order to evaluate the performance of the two processes. Experimental data showed that both UV₂₅₄ and COD reductions are improved in the combined biological–chemical oxidation procedure. Thus, reductions of 59.1% and 37.2% corresponding to COD and UV₂₅₄, respectively were observed after the biological process (hydraulic retention time = 5 h; mixed liquor volatile suspended solids concentration = 3142 g m⁻³) compared with 71.0% and 78.4% obtained when a post‐ozonation step ( D _O3 = 41.7 g m⁻³) was included. During conventional activated sludge treatment, appropriate nitrification levels are only achieved with high hydraulic retention time and/or biomass concentration. Ozonation after the secondary treatment, however, allows improved nitrogen content reduction with total nitrite elimination. Post‐ozonation also leads to a higher biodegradability of the treated wastewater. Thus, the ultimate BOD/COD ratio goes from 0.16 after biological oxidation to 0.34 after post‐ozonation with 41.7 g O₃ m⁻³. © 1999 Society of Chemical Industry     

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.     

Ozonation of Humic Substances: Effects on Molecular Weight Distributions of Organic Carbon and Trihalomethane Formation Potential

Four different sources of humic substances were studied to determine the effects of ozonation on molecular weight-distributions, based on dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP). Solutions of two soil-derived fulvic acids and a one soil-derived humic acid, as well as dissolved organic matter (DOM) associated with a natural water source were studied. Both gel permeation chromatography (GPC) and ultrafiltration (UF) were employed to define apparent molecular weight (AMW). Applied ozone doses ranged from 2.0 to 2.5 mg O₃/mg DOC. Overall samples of untreated and ozonated waters, as well as individual molecular weight fractions, were characterized according to DOC, UV absorbance, and THMFP. Ozonation resulted in a significant disappearance of higher AMW material with a corresponding increase in lower AMW material. Although little overall reduction in DOC concentration was observed, significant overall reductions in UV absorbance and THMFP levels were observed.     

Photocatalytic ozonation of gallic acid in water

Aqueous solutions of gallic acid have been treated with five different oxidation‐radiation processes: visible and ultraviolet A radiation (VUVA), TiO₂ adsorption, ozonation, VUVA/TiO₂ photocatalysis and VUVA/O₃/TiO₂ photocatalytic ozonation. With the exception of VUVA radiation and TiO₂ adsorption, ozone and photolytic processes allow for the total removal of gallic acid in a period between 50 and 90 min. The time taken to achieve 100% gallic acid conversion depends on the oxidation process applied, photocatalytic ozonation being the most effective technique. Throughout the process, oxalic and formic acids were identified as byproducts. Some other unidentified compounds probably related to pyruvic, malonic and maleic acids were also detected. The appearance of these compounds can be justified from direct reactions of both hydroxyl radical and ozone in water. Only photocatalytic ozonation leads to total mineralisation of the organic matter in less than 90 min. The photocatalyst used, TiO₂, showed good activity and stability (no leaching was observed) after five consecutive photocatalytic ozonation runs with the same semiconductor‐catalyst mass. Copyright © 2006 Society of Chemical Industry     

Removal of organic contaminants in paper pulp effluents by AOPs: an economic study

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     

Soil Fulvic Acid Degradation By Ozone In Aqueous Medium

Armadale Armadale soil fulvic acid (SFA) was found to contain several loosely bound organic impurities which could be removed by ethyl acetate extraction. The ozonation of purified Armadale SFA at a variety of dosages was characterized by monitoring the UV absorbance, weight loss, pH changes, total acidity, molecular weight and elemental composition. SFA could only be partially degraded even under ozone dosages as high as SFA/O₃ (w/w) of 1:6. At high ozone dosages (SFA/O3 1:6) mostly aliphatic compounds rich in oxygen were produced, whereas at low ozone dosages (SFA/O₃ < 1:0.5) mainly benzene polycarboxylic acids and polyhydroxy benzene polycarboxylic acids were found. The solid material bisolated from the chlorination (0.5 mg/L residual level) of residues from the ozonation (SFA/O₃ 1:0.2 to 1:0.5) of Contech SFA did not contain any chlorinated products.     

Ozonation of chloronitrobenzenes in aqueous solution: kinetics and mechanism

BACKGROUND: Chloronitrobenzenes (ClNBs) are a family of toxic and bio‐resistant organic compounds. Ozone treatment is specifically suitable for partial or complete oxidation of non‐biodegradable components. However, few studies on the decomposition of ClNBs by ozone are available, and kinetics and mechanisms of ClNBs ozonation have not been thoroughly investigated. The kinetics and mechanism of ozonation degradation of ClNBs in aqueous solution were investigated, and the contribution of both molecular ozone and hydroxyl radicals was also evaluated. RESULTS: The results demonstrated that the decomposition of ClNBs was a pseudo‐first‐order reaction with respect to the pollutant concentration and the overall rate constant increased with an increase in pH. It declined, however, with an increase in pollutant and radical scavenger concentration. Furthermore, TOC removal rate was significantly lower than that of ClNBs, but the same order o‐ClNB < m‐ClNB < p‐ClNB was followed. Ozonation could not reduce TOC significantly, p‐chlorophenol, p‐nitrophenol, 2‐chloro‐5‐nitrophenol and 5‐chloro‐2‐nitrophenol were detected as primary degradation intermediates in ozonation of p‐ClNB. Rate constants of the direct reaction between ozone and ClNBs at 25 °C had been found to be lower than 1 M^?1S^?1. More than 95% of ClNBs removal was due to hydroxyl radical oxidation at pH ≥ 7. CONCLUSION: Advanced oxidation processes may be the preferred choice for the elimination of ClNBs from the environment. Copyright © 2008 Society of Chemical Industry     

Effect of ozonation on chemical oxygen demand fractionation and color profile of textile wastewaters

Filtration and ultrafiltration with a size range of 2–1600 nm were used to evaluate the effect of ozonation on the particle size distribution‐based chemical oxygen demand (COD) and color profiles of textile wastewater before and after biological treatment. Ozonation induced a net effect of 9% COD reduction in the influent and 15% in the effluent. However, a more in‐depth evaluation based on particle size distribution and mass balance for the influent revealed different mechanisms of ozonation, which were interpreted as total oxidation in the soluble range, replenishment of soluble COD through solubilization of organics into simpler compounds and polymerization towards the upper size range (>220 nm). For the biological treatment effluent, the greatest effect of ozonation was in the lower particle size range (<8 nm). Ozone was very effective for color removal, giving 80–93% optical density reductions in the influent and 96–99% in the effluent, depending on the excitation wavelength selected. Ozonation of the influent removed practically all color fractions, except in the particulate range. In the effluent, the particulate fraction was removed by biological treatment and settling and consequently the remaining color were almost entirely removed by ozonation. Copyright © 2005 Society of Chemical Industry     

Evaluation of Estrogenicity for 17 β-Estradiol Decomposition During Ozonation

To evaluate the decomposition and formation characteristics of estrogenic compounds during ozonation, semibatch ozonation experiments were conducted using the prototypical estrogen, 17β-estradiol (E₂). Ozonation was shown to be very effective for decomposition of E₂ and decrease of estrogenicity. An E₂ equivalent concentration index was introduced based on the estrogenicity intensity measured with Estrogen Competition Binding Assay (ECB Assay). The importance of evaluation of estrogenicity by ECB Assay was shown by the difference in removal efficiencies between E₂ equivalent concentration and the E₂ itself. Through this research, ozonation was shown to be a promising method to remove E₂ without any formation of estrogenic by-products from secondary-treated sewage, which contained E₂ of ngL level and total organic carbon (TOC) of several mgL.     

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     

Compositional Changes of Hydrocarbons of Residual Oil in Contaminated Soil During Ozonation

Ozonation is an effective method to remove recalcitrant weathered oil in contaminated soil. The purpose of this study was to characterize the compositional changes of hydrocarbons in residual oil during ozonation. A bioremediated soil containing residual oil was ozonated for up to 15 h. A total of 102 compounds in the residual oil were analyzed by GC/MS and 36 diagnostic ratios (DRs) were calculated based on quantitative or semi-quantitative results in order to evaluate the susceptibility of the residual oil compositions to ozonation and the effects of ozonation on the fingerprint profile of the residual oil. The total ozonation removal rates were in the following order: triaromatic steranes (TAS) > steranes, polycyclic aromatic hydrocarbons, terpanes > alkanes. Ozone kept the fingerprints of n-alkanes, C₂₇- to C₃₄-terpanes, steranes and TAS, separately. Branched alkanes (i.e., pristane and phytane) showed a higher removal rate than n-alkanes. Ozone reactivity of PAHs depended on the number of rings, presence of heteroatoms and level of alkylation. Four- to six-ring PAHs and PAHs with a high level of alkylation showed higher reactivity, while dibenzothiophene and alkylated dibenzothiophenes were found to be resistant to ozonation. Some of the biomarker source ratios remained stable and could still be used for source identification even after some of the biomarkers were removed by >90% by ozonation.     

Effects of thermally oxidized triglycerides on the oxidative stability of soybean oil

Soybean oil purified by silicic acid column chromatography did not contain peroxides, free fatty acids, phospholipids or oxidized polar compounds. The purified soybean oil was thermally oxidized at 180°C for 96 hr in the presence of air. The thermally oxidized compounds (31.3%) were separated from the purified soybean oil by gradient elution silicic acid chromatography. Thermally oxidized compounds contained hydroxyl groups, carbonyl groups andtrans double bonds according to the infrared spectrum. Thermally oxidized compounds were added to soybean oil and purified soybean oil at 0, 0.5, 1.0, 1.5 and 2.0% to study the effects of these compounds on the oxidative stability of oil. The oxidative stabilities of oils were determined by gas chromatographic analysis of volatile compound formation and molecular oxygen disappearance in the headspace of oil bottles. The thermally oxidized compounds showed prooxidant effects on the oxidative stabilities of both refined, bleached and deodorized soybean oil and purified soybean oil. Duncan’s Multiple Range Test showed that thermally oxidized compounds had a significant effect on the volatile compound formatiion and oxygen disappearance in the headspace of oil at α=0.05.     

Cost analysis for the degradation of highly concentrated textile dye wastewater with chemical oxidation H2O2/UV and biological treatment

The efficiency and cost‐effectiveness of H₂O₂/UV for the complete decolorization and mineralization of wastewater containing high concentrations of the textile dye Reactive Black 5 was examined. Oxidation until decolorization removed 200–300 mg g^?1 of the dissolved organic carbon (DOC). The specific energy consumption was dependent on the initial dye concentration: the higher concentration required a lower specific energy input on a weight basis (160 W h g^?1 RB5 for 2.1 g L^?1 versus 354 W h g^?1 RB5 for 0.5 g L^?1). Biodegradable compounds were formed, so that DOC removal could be increased by 30% in a following biological stage. However, in order to attain 800 mg g^?1 overall mineralization, 500 mg g^?1 of the DOC had to be oxidized in the H₂O₂/UV stage. A cost analysis showed that although the capital costs are much less for a H₂O₂/UV stage compared to ozonation, the operating costs are almost double those of ozonation. Thus, while H₂O₂/UV can compete with ozonation when the treatment goal only requires decolorization, ozonation is more cost‐effective in this case when mineralization is desired. Copyright © 2006 Society of Chemical Industry