Ozonation of Dyestuffs and Intermediates and Further Decrease in Dissolved Organic Carbon by Post-Biodegradation

Four each of water-soluble dyestuffs, intermediates and reference compounds were examined to determine the effect of the combined use of ozonation and post-biodegradation on the decrease in the amount of dissolved organic carbon (DOC) and the synergistic effect induced by ozonation. The amount of DOC removed by ozonation was increased initially with increasing ozonation time, and showed a plateau thereafter. The amount of ozone required to remove 1 mg of DOC (ΔO₃/ΔDOC) ranged from 5.2 to 18.6 mgO₃/mgC for the dyestuffs and the intermediates. The DOC concentrations of all the ozonized solutions were decreased with incubation time. In the case of the dyestuffs and the intermediates, the total amounts of DOC removed were increased with increasing ozonation time and showed a plateau thereafter. The synergistic effect (the ozonation-induced increase in the amount of DOC removed by the biological process) was dependent on the initial biodegradability, and was observed in all the dyestuffs and the intermediates in the range of 0.2 to 42.7 mgDOC. On the other hand, no synergistic effect was observed in the reference compounds of high biodegradability.     

Characterization procedure for adsorption of DOC (Dissolved Organic Carbon) from synthetic wastewater

A characterization method to evaluate the composition of background organic matters in terms of adsorbability was presented and applied to synthetic and domestic wastewater. The binomial distribution of DOC (Dissolved Organic Carbon) fraction in relation of a characterizing variable, the Freundlich coefficient, k, was proposed to describe the initial composition of wastewater by a finite number of pseudospecies. This method was tested for removal of DOC by using granular and powdered activated carbons. These experiments enable us to get information on the distribution function of species in the solution. From the results obtained in this work, kinetic experimental data were predicted on the assumption that the diffusion coefficients were unchanged during the experiments. It was confirmed to be effective in determining the initial composition and describing the equilibria of the DOC. From the experiments, it was found that this synthetic solution has a sigmoid type isotherm on activated carbons. This implies that there are two different adsorption regions in a system, favourable and unfavourable cases, depending on the solution concentration. This unfamiliar problem can be solved by using a characterization method based on IAST-Freundlich model.     

Removal of Dissolved Organic Carbon and Color from Dyeing Wastewater by Pre-ozonation and Subsequent Biological Treatment

The effects of pre-ozonation and subsequent biological treatment on the decrease in dissolved organic carbon (DOC) and color from dyeing wastewater were investigated. Moreover, the compositions of organic compounds in raw wastewater (RW) and the respective treated waters were estimated, and microscopic observations of the mixed liquor were conducted. The amount of ozone required to remove 1 mg of DOC and the DOC removal rate brought about by pre-ozonation ranged from 6.6 to 13.2 mgO₃/mgC and 12 to 15%, respectively. The total amount of DOC removed was increased by the combined use of pre-ozonation and subsequent biological treatment, and pre-ozonation did not necessarily lead to an increase in the amount of DOC removed by biological treatment. However, this combined method was effective in decreasing color and adsorbable organic halide formation potential (AOXFP). The rates of the dyestuff in RW and the respective treated waters were less than 10% of total DOC, and those of the other non-biodegradable compounds were much higher than those of the dyestuff. The morphological difference was observed in the predominant bacteria in RW with and without pre-ozonation.     

Improvement of a Biological Treatment by Prior Ozonation

The operating process used to study the improvement of biodegradability of synthetic waste by ozonation used two biodisk pilot units in parallel. After progressively acclimatizing the micro-organisms to the substrates in the presence and absence of ozonation, the change in purification efficiency of the two biodisks was compared. The results obtained for the compounds studied (paranitroaniline, anthraquinone-2-sulfonic acid, and polyethylene glycol, M.W. 8,000) showed that ozonation significantly improved biodegradation of the solutions.     

The Effect of Ozonation and Filtration on AOC (Assimilable Organic Carbon) Value of Water from Eutrophic Lake

The effects of applying ozone into the source water of Cheng-Ching Lake Water Works (CCLWW) on the analysis of AOC (assimilable organic carbon) were compared in the laboratory and pilot-scale tests. CCLWW takes its raw water from an eutrophic lake. A pilot plant, established in CCLWW in southern Taiwan, was performed to improve the quality of water obtained by the former treatment processes. The direct application of ozone to the source water of CCLWW is called the pre-O₃ process. The post-O₃ process involves the treatment of effluent with ozone through a sand filter, following other treatments, including pre-O₃, coagulation and sedimentation. In a laboratory test, a 0.45 μm membrane filter was used to replace the facility of filtration for a sand filter. AOC_Total comprises AOC_P17 and AOC_NOX, which were determined using the P. fluorescens strain P17 and the Spirillum species strain NOX, respectively. During over 2 years' sampling in eutrophic lake, it revealed that AOC_P17 contributed substantially to AOC_Total. However, the filtrate from the source water obtained by filtering through a 0.45 μm membrane filter had an AOC_Total much lower than that of the source water, especially for the considerable decrease of AOC_P17. Also, the AOC value in source water is increased with algae number but not with NPDOC (non-purgeable dissolved organic carbon). This result indicated that algae numbers existing in the eutrophic lake might affect the analysis of AOC. Following the pre-O₃ process at the pilot-scale plant, the AOC_P17 was markedly lower than that of the source water, and AOC_NOX was slightly higher than that of the source water. However, when post-O₃ was added to the effluent from a sand filter at the pilot-scale plant, AOC_NOX exceeded that before post-O₃, while AOCP17 differed slightly from that before post-O₃. Apparently, this difference may be due to the algae number existing in the water samples. These results were verified by applying ozone to the source water, and to filtrate obtained by filtering through a 0.45 μm membrane filter in a lab-scale test, respectively.     

Catalytic Ozonation of Oxalic Acid in the Presence of Fe2O3-Loaded Activated Carbon

ABSTRACT

The activity and optimum condition of metal-loaded activated carbon catalyst (Me/AC) for oxalic acid (OA) ozonation were evaluated. Results showed that Fe-loaded activated carbon (Fe/AC) showed better activity in five kinds of Me/AC catalysts prepared by a dipping method. Fe catalyst, crystallizing as γ-Fe₂O₃, dispersed well on AC surface. Fe₂O₃/AC, with 1.12% Fe weight ratio and 450°C calcination temperature and showed better activity for OA ozonation. 89.2% of OA was removed in the Fe₂O₃/AC/O₃ process, which was higher than those in AC/O₃ (79.6%) and O₃ (3.2%) processes. The calcination process helped to promote adsorption capability and catalytic activity of AC. In addition, Surface hydroxyl groups played a key role in Fe₂O₃/AC’s catalytic activity. Acidic condition was more favorable for OA removal in the Fe₂O₃/AC/O₃ process. A hydroxyl radical (?OH) oxidation mechanism was proven in Fe₂O₃/AC/O₃. The catalytic activity of Fe₂O₃/AC remained satisfactory after several cycles, indicating that Fe₂O₃/AC had a good reusability property.     

Degradation of Refractory Organic Pollutants by Catalytic Ozonation—Activated Carbon and Mn-Loaded Activated Carbon as Catalysts

A novel catalyst for the ozonation process was prepared by loading manganese on the granular activated carbon (GAC). Nitrobenzene was used as a model refractory organic micropollutant in this study. The catalytic activity of GAC and the Mn-loaded GAC were studied respectively. The removal efficiency of nitrobenzene by Mn-loaded GAC catalyzed ozonation could reach 34.2–49.9%, with the oxidation efficiency being about 1.5–2.0 times higher than that achieved in GAC catalyzed ozonation and 2.0–3.0 times higher than that achieved by ozonation alone. The effect of pH and the t -butanol on the GAC/ozone process was discussed. The optimum condition for preparing the catalyst was studied.     

Removal of Dissolved Organic Carbon and Color from Dyeing Wastewater by Pre-Ozonation and Subsequent Biological Treatment Using Test-Scale Plant

The effects of pre-ozonation and subsequent biological treatment process on the decrease in dissolved organic carbon (DOC) and color were investigated in a test-scale plant of 5 m³/d capacity using actual raw wastewater (RW) from a dye works. Ozone dosage rate and contacting time were around 70 mg/L on average and 30 min, respectively. The DOC concentration was gradually decreased from 36.1 to 19.3 mg/L on average through the process and the DOC removal rates were 24.4% after ozonation and 46.5% after subsequent biological treatment. The average color value was rapidly decreased from 1.75 to 0.20 after ozonation, and the color removal rate was 88.6%. The values of adsorbable organic halide formation potential (AOXFP) and trihalomethane formation potential (THMFP) were gradually decreased by each treatment process, indicating the increased safety of the treated water. Slight morphological differences due to decomposition of the predominant bacteria by residual ozone were observed. The DOC removal rate brought about by pre-ozonation was slightly higher than that by the process consisted of biological treatment and post-ozonation, although no obvious difference in the color removal was observed between them.     

Application of characterization procedure in water and wastewater treatment by Adsorption

The background organics in water and wastewater are necessary to fractionate into groups or components according to the difference in adsorbability. In this study, the background organics were fractionated in terms of the adsorptive strength described by the Freundlich isotherm constants k and n with the assumption that the fractionated components differ in the value of k but have the same value of n based on the IAST (Ideal Adsorption Solution Theory) using binomial concentration distribution. A simple characterization for water and wastewater with a certain amount of DOC in terms of adsorbability was applied to three types of organic mixtures contained in different water sources. The composition of each organic mixture was successfully evaluated to describe the IAE (Integral adsorption experiments) data of the total organic carbon by using this characterization procedure. Batch experiments as well as the membrane-PAC hybrid system experiments were conducted with three different types of PACs.     

The Effects of Ozonation,Biological Filtration and Distribution on the Concentration of Easily Assimilable Organic Carbon (AOC) in Drinking Water

The concentration of easily assimilable organic carbon (AOC) as determined with growth measurements using wo bacterial cultures, increased linearly with ozone dosage at values below 1 mg O₃/mg of C. Moreover, a linear relationship was found between AOC increase and the decrease of UV absorbance of water after ozonation with various dosages. Biological filtration in water treatment reduced AOC concentrations, but the remaining values were above the AOC concentration before ozonation. This AOC removal was attended with an increased colony count in the filtrate. The AOC concentration of drinking water produced by the application of ozone in water treatment decreased during distribution. The greatest decrease was observed with the highest AOC concentration. Also in this situation, the highest colony counts were found. To date, ozonation is applied in seven water treatment plants in the Netherlands.     

Effective Ozonation of Secondary Effluents with Initial Ozone Demand

It is clarified that the ozone consumption during the initial stage of ozonation before dissolved ozone appears is the same value as that during the initial 20 seconds in batch mode experiment. This initial ozone consumption was defined as initial ozone demand (IOD) in this study. IOD of secondary effluent was shown to be 0.3–0.5 mgO₃/mgC₀. More than 90% of 17β-estradiol (E2) was reduced, and formation of ozonation by-products was controlled within this ozone demand. This state can be also characterized by reduction of the values of UV₂₅₄, fluorescence intensity at 345 nm (Excitation)/435 nm (Emission) and that at 240 nm/435 nm to 0.06 /cm, 35 and 15, 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.     

Degradation of Carbamazepine by Photo-assisted Ozonation: Influence of Wavelength and Intensity of Radiation

This article presents the results of an investigation into the function of UV in a photo-assisted ozonation process for treatment of carbamazepine (CBZ) in treated domestic wastewaters. Experiments were conducted on synthetic spiked water and secondary treated municipal wastewater. Degradation of CBZ was studied for various combination of O₃ dosage ranging from 4.8 to 14.4 mg/h and UV intensities with varying intensity and wavelength (UVC: λ = 254 nm and UVA: 352 nm). In synthetic spiked water, CBZ was degraded to below detectable limits within 0.5 min for ozone dose of 14.4 mg/h. The rate of degradation of CBZ increased exponentially with increase in ozone dose following a zero-order rate at each dose level. The degradation rate of CBZ in wastewater was slower compared to deionized water (DI) water by 40–75% for various doses of ozone, presumably due to the presence of organic matter remaining in treated wastewater. Optimal UV intensities for UVA and UVC were obtained as 0.62 and 0.82 mW/cm² for all doses of ozone in synthetic spiked water samples and UV intensities beyond this resulted in lower rates of degradation of CBZ. For photo-assisted ozonation with ozone doses of 9.6 and 14.4 mg/L, rate constants were two times higher for UVA irradiations as compared to UVC irradiation. Contrary to observations in DI water, experiments in wastewater showed increase in rate of degradation with higher UV intensities. Overall, photo-assisted ozonation was found to be appropriate for both water and wastewater treatment by exploiting the benefit of direct attack of ozone and of produced ^?OH radicals to yield a greater extent of mineralization of CBZ.     

Reduction of Biocide-Polluted Wastewater Using O3 and H2O2/O3 Oxidation Processes

The objective of the presented study was to test various oxidation processes with the aim being to reduce the concentration and toxicity of biocide wastewater from a Slovenian phytopharmaceutical factory. Laboratory-scale experiments employing two AOP processes – ozonation (O₃) and peroxone (H₂O₂/O₃) – were applied to reduce the concentration of the active components involved, i.e., methylisothiazolone (MI), chloromethylisothiazolone (CMI) and dichloromethylisothiazolone (DCMI). The reduction of the biocide wastewater load for the performed oxidation processes was evaluated using ecological parameters. The H₂O₂/O₃ oxidation procedure using an O₃ flow rate of 1g/L h, at a pH value of 10 and with the addition of 5 ml of H₂O₂ (0.3 M) proved to be the most effective treatment. The toxicity of the biocide-load wastewater with an initial EC₅₀ = 0.38%, decreased to EC₅₀ (24h) >100% and EC₅₀ (48h) = 76%.     

Variation of organic halide formation potential of dyestuffs during ozonation and correlation with color

The control of the discharge of precursors to trihalometanes (THMs) derived from industrial wastewater is indicated to be important as well as the countermeasures in drinking water plants. Effluents containing various dyestuffs, intermediates and auxiliaries, which are typically biorefractory, are known to have high trihalomethane formation potential (THMFP) as well as intense color. In this study, fourteen water‐soluble dyestuffs were ozonated to investigate the variations of total organic halide formation potential (TOXFP) and THMFP, and then correlated with color. Phenol was selected as a target compound because it had a fundamental molecular structure. The ratio of THMFP to TOXFP (THMFP/TOXFP) varied from 0.12 to 0.54 before ozonation. The variation patterns of TOXFP and THMFP were roughly divided into two groups: (1) compounds showing a maximum in the initial stage and (2) compounds showing a uniform decrease. In spite of the different variation patterns and initial values, long‐term ozonation decreased both TOXFP and THMFP. The difference in THMFP/TOXFP became slighter after ozonation. From the relationship between TOXFP, THMFP and color, long‐term ozonation, especially ozonation after decolorization was found to be necessary for the removal of organic halides.     

Electrochemical degradation of azo dye C.I. Reactive Red 195 by anodic oxidation on Ti/SnO2-Sb/PbO2 electrodes

This study investigated the electrochemical degradation of C.I. Reactive Red 195 (RR195) in aqueous solution on a Ti/SnO₂-Sb/PbO₂ electrode. The influence of operating variables on the mineralization efficiency was studied as a function of the current density, the initial pH, the initial concentration of the dye and the addition of NaCl. The efficiency of RR195 mineralization decreased with increased initial concentration, from 100 mg L⁻¹ to 400 mg L⁻¹. The current density had both a positive and a negative effect on degradation rates, and no significant effect of initial pH on RR195 mineralization was observed. Measurement of absorbance was used to discriminate the effect of NaCl in the electro-oxidation process. We found that the decolouring efficiency increased whereas the mineralization efficiency decreased with the increasing concentration of NaCl. The intermediates formed during the degradation were detected by gas chromatography-mass spectrometry, and the major aromatic intermediates identified were 1-(3,6,8-trihydroxy-1-naphthyl)urea, nitrobenzene, benzo-1,4-quinone, (3,6,8-trihydroxy-1-naphthyl)carbamic acid and phthalic acid. Quantitative measurement of organic and inorganic ions was done by ion chromatography. On the basis of the reaction products identified, a possible degradation pathway for the anodic oxidation of RR195 in aqueous solution is proposed.     

Self Assembly and Properties of C:WO3 Nano-Platelets and C:VO2/V2O5 Triangular Capsules Produced by Laser Solution Photolysis

Laser photolysis of WCl₆ in ethanol and a specific mixture of V₂O₅ and VCl₃ in ethanol lead to carbon modified vanadium and tungsten oxides with interesting properties. The presence of graphene’s aromatic rings (from the vibrational frequency of 1,600 cm⁻¹) together with C–C bonding of carbon (from the Raman shift of 1,124 cm⁻¹) present unique optical, vibrational, electronic and structural properties of the intended tungsten trioxide and vanadium dioxide materials. The morphology of these samples shows nano-platelets in WO _x samples and, in VO _x samples, encapsulated spherical quantum dots in conjunction with fullerenes of VO _x . Conductivity studies revealed that the VO₂/V₂O₅ nanostructures are more sensitive to Cl than to the presence of ethanol, whereas the C:WO₃ nano-platelets are more sensitive to ethanol than atomic C.     

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.     

Deactivation of V2O5-WO3-TiO2 SCR catalyst at biomass fired power plants: Elucidation of mechanisms by lab- and pilot-scale experiments

In this work, deactivation of a commercial type V₂O₅-WO₃-TiO₂ catalyst by aerosols of potassium compounds was investigated in two ways: (1) by exposing the catalyst in a lab-scale reactor to a layer of KCl particles or fly ash from biomass combustion; (2) by exposing full-length monolith catalysts to pure KCl or K₂SO₄ aerosols in a bench-scale reactor. Exposed samples were characterized by activity measurements, SEM-EDX, BET/Hg-porosimetry, and NH₃ chemisorption. The work was carried out to support the interpretation of observations of a previous study in which catalysts were exposed on a full-scale biomass fired power plant and to reveal the mechanisms of catalyst deactivation.Slight deactivation (about 10%) was observed for catalyst plates exposed to a layer of KCl particles at 350 °C for 2397 h. No deactivation was found for catalyst plates exposed for 2970 h to fly ash (consisting mainly of KCl and K₂SO₄) collected from an SCR pilot plant installed on a straw-fired power plant. A fast deactivation was observed for catalysts exposed to pure KCl or K₂SO₄ aerosols at 350 °C in the bench-scale reactor. The deactivation rates for KCl aerosol and K₂SO₄ aerosol exposed catalysts were about 1% per day and 0.4% per day, respectively.SEM analysis of potassium-containing aerosol exposed catalysts revealed that the potassium salt partly deposited on the catalyst outer wall which may decrease the diffusion rate of NO and NH₃ into the catalyst. However, potassium also penetrated into the catalyst wall and the average K/V ratios (0.5–0.75) in the catalyst structure are high enough to explain the level of deactivation observed. The catalyst capacity for NH₃ chemisorption decreased as a function of exposure time, which reveals that Brønsted acid sites had reacted with potassium compounds and thereby rendered inactive in the catalytic cycle. The conclusion is that chemical poisoning of active sites is the dominating deactivation mechanism, but physical blocking of the surface area may also contribute to the loss of activity in a practical application. The results support the observation and mechanisms of deactivation of SCR catalysts in biomass fired systems proposed in a previous study [Y. Zheng, A.D. Jensen, J.E. Johnsson, Appl. Catal. B 60 (2005) 253].