Ozone Application during Coagulation of Wastewater: Effect on Dissolved Organic Matter

The aim of this work was to determine the effect of ozone on dissolved organic matter (DOM) during wastewater coagulation using alum. Adding ozone to the coagulation treatment (O₃ECT) enhanced the quality of the final effluent in comparison to conventional coagulation treatment (CT). Final effluents were analyzed by Fourier transform infrared Spectroscopy (FTIR) and UV-Vis spectroscopy. The hydrophilic polar fraction was separated from the hydrophobic fraction using fractionation resins XAD-8 and XAD-4. Wastewater hydrophilic DOM was characterized by molecular weight distribution (MWD), and, BOD₅, TOC and DOC parameters. Results show that FTIR spectra for both effluents were very similar in the frequency range 7000 to 1400 cm^?1; however, some differences occurred in the O₃ECT effluent in the range 1100 to 700 cm^?1, which indicated that amines and aromatics groups were affected. In the same way, the UV-Vis spectra showed that there was an increase in absorbance within the wavelength range 285 to 300 nm for the O₃ECT effluent (when compared with CT) while the absorbance decreased in the range 210 to 455 nm, particularly at 380 nm. With regards to the hydrophilic polar compounds of DOM, the most abundant fraction in raw wastewater was found in the 3–10 kDa range. After CT, the effluents fraction concentrations decreased in all cases, but for O₃ECT the 10–30 kDa range exhibited a marked increase while the smaller (<3 kDa, 3–10 kDa) and larger fractions (>30 kDa) decreased. The ozone application during coagulation slightly increased TOC and DOC percentage removals, 84.4% to 89.1% and 80% to 82.5%, respectively. This suggests that the small dose of ozone transferred (1.47 mg/L) caused only minor changes in DOM. Finally, the O₃ECT effluent exhibits 10 mg/L more of biological oxygen demand (BOD₅) than a single CT.     

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     

Adsorption Equilibrium of DOC by Activated Carbon and the Influence of Preozonation

A linear isotherm model, modified to account for a non-adsorbable fraction, was found to fit adequately the adsorption equilibrium of organic matter from a tertiary treated wastewater. The isotherm slope varied significantly among sample days, but the range of variability did not exceed a factor of two. A moderate ozone dose (0.5 g O₃/g DOC) enhanced adsorbability in both laboratory and full-scale systems, whereas higher doses appeared to decrease adsorption. Preozonation had little effect on the nonadsorbable portion of DOC.     

Effects Of Ozone-Hydrogen Peroxide Combination On The Formation Of Biodegradable Dissolved Organic Carbon

The effects of ozone and ozone/hydrogen peroxide on BDOC formation were studied with the “Ozotest” method, a laboratory technique that permits the assessment of oxidation efficiency. Oxidation treatments were performed on river water and sand filter effluent samples. Ozone consumption, reduction of UV absorbance, and BDOC formation were monitored during the experiments. The ratio of 0.35-0.45 mg H₂O₂ per mg O₃ used to degrade pesticides also was optimal for the oxidation of organic matter. BDOC formation versus ozone dose curves with ozone alone or ozone/peroxide system were similar. BDOC formation was optimum at an applied ozone dose of 0.5-1 mg O₃/mg C (contact time = 10 min). The ozone/peroxide system yielded lower BDOC values than ozone alone, a phenomenon related to differences in byproducts generated by the two oxidative systems. Moreover, reduction of the concentration of DOC was higher with ozone/hydrogen peroxide than with ozone alone. For both oxidant systems, BDOC formation occurred during the first minute of treatment.     

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.     

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).     

Reaction Kinetics of Ozone with Selected Pharmaceuticals and Their Removal Potential from a Secondary Treated Municipal Wastewater Effluent in the Great Lakes Basin

Oxidation kinetics of selected pharmaceutical compounds and their degradation during ozonation of secondary treated municipal wastewater effluent (MWWE) was investigated. The apparent second-order rate constants for the reaction between chlorotetracycline (CTC), enrofloxacin (ENR), gemfibrozil (GEM) and ozone ranged between 6.82 – 52.7 × 10⁴ M^?1s^?1. The measured second-order hydroxyl radical rate constants were several orders of magnitude higher at 8.4 × 10⁹ – 13.1 × 10⁹ M^?1s^?1 with a reactivity sequence of GEM > CTC > ENR. Overall degradation of CTC, ENR and GEM in secondary treated municipal wastewater effluent was >76 % at ozone doses of 0.33 mg O₃/mg DOC or higher.     

The Effect of Ozonation on the Removal of Organics by Coagulation – Flocculation

We present here some works which take place in the particular framework of the study of drinking water treatment of reservoir waters which contain high concentrations of organics, mainly humic substances. Previous studies on coagulation of fulvic acid solutions have proved that the optimal removal of organic matter was reached at acidic pH with 2 mg of ferricion per mg or organic carbon (summarized in this paper). The main question in this study is to know what is the impact of preozonation on the removal of organics by iron (III) coagulation.

The study of the behavior of organics, in terms of UV-absorbance and TOC measurements was made on three aquatic fulvic acids and on two raw waters. The experiments carried out with fulvic acids showed that preozonation (at 0.5 mg O₃/mg C) of fulvic acid appeared to have shifted the region of the optimal DOC removal towards the higher coagulant dose. Furthermore, increasing ozone doses led to a slight decreasing of coagulation efficiency at constant coagulant dose. With two raw waters, preozonation at low ozone doses (0.2 mg 0₃/mg C) was found to improve very slightly the elimination of organic matter, while high ozone doses (0.9 mg O₃/mg C) led to a disturbance of TOC elimination by iron coagulation.     

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.     

Evaluation of Decolorization,Mineralization, and Toxicity Reduction of Tropaeolin O in Water by Ozonation with UV Irradiation

The combination of ozonation with UV irradiation can remove Tropaeolin O (AO6) and its by-products effectively and completely. The ozone dose affects the rate of decolorization, AO6 species removal, and dissolved organic carbon (DOC) reduction significantly. After 240 minutes of ozonation, the average DOC removal efficiency (η_DOC) for O₃ alone was about 0.79, while η_DOC for O₃/UV was 1.0. The average DOC removal rate was low at early stage of ozonation due to decolorization and low DOC. At later stage of ozonation, average DOC removal rate decreases because of the formation of persistent intermediates. The ozone consumption was consistent with η_DOC. The ratio of ozone consumption to ozone applied decreased from 14 to 12% when η_DOC < 40% because the decolorization in the early stage of the ozonation of AO6 may consume a relatively large amount of ozone. It was found that NO₂, NO, CO₂, and small amount of SO₂ was detected in the off-gas. The effective concentration (EC50) increased from 23.48% to 100%, suggesting that the toxic reduction was achieved, and O₃/UV system was superior to O₃ alone system     

Effects Of Ozone On Kraft Process Pulp Mill Effluent

Effluent from a kraft process pulp mill was studied in a batch reactor for ozone doses between 50 and 200 mg O₃/L to identify the relative suitability of ozone application locations in the treatment process and see the improvements in biotreatability of wastewaters from a kraft process pulp mill. Laboratory acclimatized seed were used for BOD tests for ozonated and unozonated samples. The inhibitory effects were minimized by using optimum dilutions. The studies were divided into three major sections: characterization of mill effluent; ozone system calibration, and reactor design; and ozonation of mill effluent. Seed for Biochemical Oxygen Demand tests were acclimatized in batch units for primary, bleach and secondary effluents separately. The inhibitory effects which were noted with unacclimatized seed, were reduced by using laboratory acclimatized seed and optimum dilution which were determined during the characterization phase.

The batch reactor designed for the studies consisted of a cylindrical section for holding effluent, and a top spherical section for ozone/oxygen mixture. The reactor proved to be effective for controlling ozone dose. The variation in the applied ozone dose was less than 5 mg/L.

Bleach and primary effluents were treated with 50 and 100 mg/L ozone doses. Duplicate experiments were conducted for these effluents. Secondary effluent was studied for 50,100,150 and 200 mg/L ozone doses. Six replicate experiments were conducted for 50 and 100 mg/L ozone doses, whereas two experiments were carried out for 150 mg/L and one experiment for 200 mg/L ozone dose.

The results were analyzed using 't' test for paired experiments and ANOVA table for statistical confirmation. Residuals were plotted to check the assumptions of constant variance and normal distribution. The results indicated that 50 and 100 mg O₃/L effectively removed color from bleach effluent and primary effluent, but did not significantly change the BOD. Ozone was found to be effective for secondary effluent, as BOD₅ was increased by 65% for 50 and 100% for 100 mg O₃/L doses. The corresponding reduction in color was 62% and 82%, respectively. K_e and L_o values for the BOD equation were calculated by using the non-linear least square method for the BOD equation, giving joint confidence regions for the calculated parameters. It was concluded that ozone is most effective for the removal of color and the increase of BOD in secondary effluent.     

Ozonation of C.I. Reactive Yellow 3 and Further Decrease in Dissolved Organic Carbon Concentration by Post-Biodegradation

Using C.I. Reactive Yellow 3 as the target compound, the effect of the combined use of ozonation and post-biodegradation on the decrease in dissolved organic carbon (DOC) concentration was investigated, and the synergistic effect (the difference in the amounts of DOC removed by the biological process between solutions with and without ozonation) was estimated. A decrease in DOC concentration was observed during ozonation and ΔO₃/ΔDOC was decreased from 16.0 to 5.2 with increasing ozonation time. Moreover, an enhancement of biodegradability was shown. A further decrease in DOC concentration was observed during the biodegradation after ozonation. The total amount of DOC removed by the combined method was increased from 73.6 mg at 30 min to 159.9 mg at 4 h. The synergistic effect was in the range of 22.7 to 39.2 mg. BOD₅ was a better indicator of the synergistic effect than BOD₅/DOC.     

Effects of O3, O3/H2O2 and Coagulation on Natural Organic Matter and Arsenic Removal from Typical Northern Serbia Source Water

The objectives of this study were to investigate the effects of ozone and the O₃/H₂O₂ process on FeCl₃ coagulation efficiency for the removal of the high content of natural organic matter (NOM) and arsenic (As) from groundwater (DOC = 9.27 ± 0.92 mg/L; 51.7 ± 16.4 µg As/L). Arsenic and NOM removal mechanisms during coagulation/flocculation are well investigated. However, data concerning arsenic removal in the presence of NOM, which is the subject of this article, are still insufficient. Laboratory and pilot plant test results have shown that the competition of NOM and As for adsorption sites on the coagulant surface have great influence on coagulation/flocculation efficiency for their removal. With both oxidation pre-treatments, arsenic content after the coagulation process was less than 2.0 µg/L in treated water. Application of ozone has a lower influence on coagulation efficacy in terms of DOC reduction, compared to the O₃/H₂O₂ process with the same ozone dose.     

Effects Of Ozone On The Production Of Biodegradable Dissolved Organic Carbon (BDOC) During Water Treatment

This article deals with the oxidation effect of ozone on the increasing fraction of biodegradable organic matter with the “ozotest” method, a laboratory technique which simulates the effect of ozonation and allows a complete oxidation assessment. Ozone treatment was performed on river water samples and sand filter effluent samples. Ozone consumption, reduction of UV absorbance and BDOC formation were monitored with applied ozone doses from 0 to 10 mg/L and with contact times from 0 to 60 min. The BDOC formation was optimum at an applied ozone dose of 0.25-0.5 mg O₃ per mg DOC (contact time = 5 min) corresponding to apparition of traces of residual ozone and maximum UV reduction. Maximum ozone consumption, UV reduction and BDOC formation occurred simultaneously during the first two minutes of treatment. Concerning BDOC formation, applied ozone dose showed a greater effectiveness than contact time. For the same quantity of consumed ozone, a short contact time associated with a high ozone dose was preferable to a long contact time and a low ozone dose.     

Ozone,Electron Beam and Ozone-Electron Beam Degradation of Phenol. A Comparative Study

The efficacy of electron beam (EB), ozone (O₃) and the combined EB/O₃ treatment on the removal of phenol, as a prototype for aromatic pollutants in water, is compared on the base of degradation, chemical oxygen demand (COD), total organic carbon (TOC) and toxicity. Complete decomposition of phenol (47?mg/L, 500?µM) was obtained with 14?kGy. Applying simultaneously 27?mg O₃/L a dose of 10.5?kGy was sufficient. By the same amount of only ozone a phenol concentration of 45% remained. A TOC reduction of more than 70% was attained with EB/O₃ (21?kGy/54?mg O₃/L), whereas the identical, separate conditions solely led to 24% (EB) and 14% (O₃). The EB/O₃ treatment showed also the best results in COD decrease (79%, 21?kGy/54?mg O₃/L) and detoxification (7?kGy/18?mg O₃/L).     

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.     

Treatability of Organic Constituents in the Paşaköy Wastewater Treatment Plant Effluent by O3 and O3/H2O2

Effluent from the Pa?aköy Wastewater Treatment Plant was oxidized by using O₃ and O₃/H₂O₂. DOC, COD, UV₂₅₄, total coliform, dissolved ozone and some endocrine disrupting compounds were monitored during oxidation. Results showed that O₃ provided superior disinfection, however, lower reductions in DOC, COD and endocrine disrupting compounds were exhibited compared to O₃/H₂O_2. The highest removal efficiency of DOC, COD and endocrine disrupting compounds were achieved at 0.5 molar ratio of O₃/H₂O_2. The benefit of H₂O₂ addition for advanced oxidation reduced significantly when the mole ratio was increased to 2. Therefore, the mole ratio of H₂O₂ to O₃ is a critical parameter for the design of wastewater oxidation by O₃/H₂O₂.     

The Formation of Filter-Removable Biodegradable Organic Matter During Ozonation

Biodegradable organic matter formed during the ozonation of natural waters was fractionated into rapidly and slowly degradable components based on measurements of biodegradable organic carbon (BDOC). The rapidly degradable fraction (BDOC_rapid) was defined using the specific BDOC reactor incubation time that resulted in biodegradation similar to that in a pilot scale biofilter. Ozone dose was found to increase the formation of BDOC_rapid up to a transferred dose of 1.0 to 1.5 mg O₃/mg DOC. This fraction was insensitive to DOC quantity or character. The formation of BDOC_slow was not sensitive to ozone dose but was sensitive to DOC quantity.     

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.     

Combination of Ozone with Activated Carbon as an Alternative to Conventional Advanced Oxidation Processes

The objective of this study was to compare the efficiency of O₃/granular activated carbon (GAC) to enhance ozone transformation into ·OH radicals, with the common advanced oxidation processes (O₃/OH^?, O₃/H₂O₂). The results obtained with model systems under the given experimental conditions showed that the system O₃/OH^? (pH 9) and O₃/H₂O₂ (pH 7, [H₂O₂] = 1·10^?5 M) are more efficient than O₃/GAC (pH 7, [GAC] = 0.5 g/L) to enhance ozone transformation into ·OH radicals. However, in Lake Zurich water the O₃/GAC process has a similar efficiency as O₃/H₂O₂ for ozone transformation into ·OH radicals. The results also show that the presence of GAC during Lake Zurich water ozonation leads to (i) removal of hydrophilic and hydrophobic micropollutants, (ii) reduction of the concentration of CO₃ ^2?/HCO₃ ^?, and (iii) decrease of the concentration of dissolved organic carbon (DOC) present in the system.