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.     

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

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

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     

Abatement of 4-Chlorophenol in Aqueous Phase by Ozonation Coupled with a Sequencing Batch Biofilm Reactor (SBBR)

The aim of this work was to assess the mineralization of 100 and 200 mg L^?1 4-chlorophenol (4-CP) solutions by ozonation-biological treatment. The results show that starting from a 4-CP initial concentration from 100 to 500 mg L^?1 and using an ozone flow rate of 5.44 and 7.57 g h^?1, 4-CP was completely removed. A kinetic constant around 9·10^?2 min^?1 was calculated for the ozone direct attack. The biodegradability (BOD₅/COD) of the pre-ozonated solutions increased from 0 until a range between 0.2–0.37. The combination of the ozonation and aerobic biological treatment in an aerobic sequencing batch biofilm reactor (SBBR) gave an abatement of more than 90% of the initial TOC.     

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 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     

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     

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.     

Ozonation Impact on Degradation and Toxicity of Non-Ionic Surfactants

Aqueous solutions of five selected non-ionic surfactants: Triton (i-octylphenolethoxylates), Tergitol (2,6,8-trimethyl-4-nonanoloxethylates), Symperonic (n-nonylphenol-oxethylates) and Brij (fatty alcohol ethoxylates) were investigated in this study. Using the bioluminescent bacteria Vibrio fischeri the toxicity of the surfactants solutions were determined. An attempt was made to relate rather low biodegradability of nonionic surfactant solutions measured by the BOD₅/COD ratio (ranging from 1 to 17%) to their toxicity. The ozonation process was carried out in a 1.5 dm³ stirred cell reactor equipped with two ozone detectors. The following parameters were analyzed: pH, COD, BOD₅, DOC, TOC, polarography as well as UV spectrum. The positive effect of ozonation, represented by decay of UV absorption, was visible in almost complete destruction of the surfactants, with exception of Triton X-705 (only 65% degradation after absorption of 2000 mgO₃/dm³). The most striking results were obtained in toxicity tests for ozonated solutions of the non-ionic surfactants – an increase of the bacterial growth inhibition (1.5 to 4 times increase in toxicity due to ozonation). The obtained results were discussed taking into account the literature and our own experimental data on mechanisms of ozonation and biodegradation of non-ionic surfactants of the Triton-type and similar chemical structures.     

Enhancing Agro-Industrial Wastewaters Depuration by Ozone Oxidation

This article explores the application of several ozone-based technologies on the abatement of a bio-refractory stream coming from an elderberry juice plant (BOD₅/COD = 0.26). The impact of ozone inlet concentration and pH was addressed firstly, followed by the analysis of the O₃+H₂O₂ combined system. Finally, the activity and stability of two solid catalysts (Mn-Ce-O and Fe-Mn-O) was assessed. None of the approaches produced values within the legal thresholds for direct discharge into water-courses. It is advisable to integrate the chemical treatment with a bio-reactor. Thus, single ozonation at pH = 3 (BOD₅/COD = 0.48), O₃+[H₂O₂] = 32.5 mM (BOD₅/COD = 0.46) and O₃+Mn-Ce-O at pH = 3 (BOD₅/COD = 0.44) are promising strategies.     

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).     

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.     

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.     

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.     

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.     

Ozonation of NSAID: A Biodegradability and Toxicity Study

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

Advanced Oxidation Treatment of Drinking Water: Part II. Turbidity,Particles and Organics Removal from Lake Huron Water

Pre-coagulation ozonation has been reported to be effective in drinking water treatment processes. Limited data are available on the impact of advanced oxidation processes (AOPs) on Lake Huron water which serves as a primary source of drinking water for many communities around the Great Lakes region. Impact of ozone/hydrogen peroxide based AOP on Lake Huron water was studied. The results show that AOPs can achieve higher particles removal in finished water and deliver improved filtered water turbidity compared to the conventional treatment process. Sharp decline in ultraviolet absorbance at 254 nm (UV₂₅₄) was observed immediately following AOP treatment while only minimal overall decrease in dissolved organic carbon (DOC) was achieved.     

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.     

Iron and Manganese Removal with Ozonation in the Presence of Humic Substances

The conditions for the removal of iron and manganese contained in slightly mineralized water, rich in humic substances, were determined in a case where an intermediate oxidation was provided in a conventional potabilization line comprising a coagulationflocculation stage with iron salts.

The experiments were conducted both on a synthetic water, with or without addition of humic substances, and on raw water from the Moulin-Papon dam. While iron was easily removed by simply increasing the pH measurement from 8.2 to 8.5 without intermediate oxidation, ozonation applied to water with a pH of nearly 8.4 did not enable the manganese to be removed with a low ozone dose (about 1 mg/L) unless a significant amount of bicarbonates (120 to 130 mg/L as CaCO₃) were injected prior to the ozonation-filtration stage.

As it removes the manganese from the water, intermediate ozonation also removes the abatement of organics on the filters, and lowers the THM buildup potential.