Performance evaluation of ozonation and an ozone/hydrogen peroxide process toward development of a new sewage treatment process—Focusing on organic compounds and emerging contaminants

Performance of ozonation and an ozone/hydrogen peroxide process under a new concept centering on ozonation and/or ozone/hydrogen peroxide processes in sewage treatment processes comprising only physical and chemical processes are discussed, with focus on the removal of matrix organic compounds and emerging contaminants. Matrix organic compounds of filtrated primary sewage effluents were removed to as low as 3.2 mgC/L in the ozone/hydrogen peroxide process at an ozone consumption of around 400 mg/L. Linear relationships between ozone consumption and removal amounts of organic compounds were observed, in which the amounts of ozone required to remove 1 mg of organic carbon were 9.5 and 8.3 mg (2.4 and 2.1 mol-O₃/mol-C) in ozonation and the ozone/hydrogen peroxide process, respectively. Ratios of hydroxyl radical exposure to ozone exposure were in the order of 10^–9 to 10^–8 for ozonation and 10^–7 to 10^–6 for the ozone/hydrogen peroxide process. Experiments and a kinetic evaluation showed that ozonation and/or the ozone/hydrogen peroxide process have high elimination capability for emerging contaminants, even in primary sewage effluent with the thorough removal of matrix organic compounds. Newly found reaction phenomena, the temporal increase and decrease of dissolved ozone and accumulation of hydrogen peroxide in the early stage of oxidation with the continuous feeding of hydrogen peroxide, were presented. Possible reaction mechanisms are also discussed.     

EFFECTS OF pH,INITIATOR, SCAVENGER,AND SURFACTANT ON THE OZONATION MECHANISM OF AN AZO DYE (ACID RED-151) IN A BATCH REACTOR

In this study, an initiator (Fe²⁺) and a scavenger (CO₃ ^2?) were used at different concentrations in a batch reactor to investigate the reaction mechanism of ozonation of a model azo dye, namely Acid Red-151 (AR-151). Also, the effect of a nonionic surfactant known as a major pollutant in many industrial wastewaters, namely polyethylene glycol (PEG), was observed on the degradation rate of AR-151. The experimental parameters and their ranges were: pH (2.5–10), initiator (0.8–50 mg/L of Fe²⁺), surfactant (10–200 mg/L of PEG), and scavenger (10–500 mg/L of CO₃ ^2?); the initial concentration of the azo dye was kept constant at 20 mg/L in all the experiments. Results showed that decomposition of ozone was enhanced with increasing pH and increasing initiator (Fe²⁺) concentration at a scavenger concentration of 100 mg/L, when there is no dye in the medium. A scavenger concentration of 100 mg/L CO₃ ^2? was not sufficient to terminate the chain reactions of ozone decomposition. It was concluded that the dominant mechanism in the degradation of AR-151 was its direct oxidation with ozone molecules in water. The data obtained for the dye and chemical oxygen demand (COD) removals and total oxidation rate constants at different operating conditions were assessed in order to estimate the possible contribution of dye-oxidation by free radicals.     

Response Surface Optimized Ultrasonic-Assisted Extraction of Quercetin and Isolation of Phenolic Compounds From Hypericum perforatum L. by Column Chromatography

The effects of ultrasonic-assisted extraction factors for the main phenolic compound (quercetin) from Hypericum perforatum L. were optimized using the Box–Behnken design (BBD) combined with response surface methodology. The BBD was employed to evaluate the effects of extraction temperature (30–70°C), extraction time (20–80 min), methanol concentration (20–80%, v/v), and HCl concentration (0.8–2.0 M) on the content of one of the major phenolic compounds of quercetin. The extracts were analyzed by high performance liquid chromatography (HPLC). The major phenolic compounds of H. perforatum were isolated and the antioxidant capacity and total phenol content were determined in crude extract and fractions. The optimum conditions were determined as extraction temperature 67°C, extraction time 67 min, methanol concentration 77% (v/v), and HCl concentration 1.2 M. The predicted content of quercetin was 10.81 mg/g dried plant under the optimal conditions and the subsequent verification experiment with 11.09 mg/g dried plant confirmed the validity of the predicted model. The isolated compounds were identified as quercetin, cyanidin, protocatechuic acid, and kaempferol.     

The Combination of Ozone/Hydrogen Peroxide and Ozone/UV Radiation for Reduction of Trihalomethane Formation Potential in Surface Water

Applied ozone dosages of 20, 25, and 30 mg/L to lake water utilized by the city of Shreveport, LA produced no significant reductions in trihalomethane formation potentials (THMFP). However, the addition of 20 mg/L of hydrogen peroxide and/or 0.67 W/L of UV radiation (254 nm) in combination with ozone produced decreases in THMFP of over 60% in 60 minutes. Smaller THMFP decreases were seen with shorter contact times. The use of H₂O₂ and/or UV in combination with O₃ increased the percentage of applied ozone consumed by the lake water (i.e., enhanced the ozone mass transfer) five times over simple ozonation.     

Removal Characteristics of Organic Pollutants in Sewage Treatment by a Pre-Coagulation,Ozonation and Ozone/Hydrogen Peroxide Process

The applicability of a sequential process of ozonation and ozone/hydrogen peroxide process for the removal of soluble organic compounds from a pre-coagulated municipal sewage was examined. 6–25% of initial T-COD_Cr was removed at the early stage of ozonation before the ratio of consumed ozone to removed T-COD_Cr dramatically increased. Until dissolved ozone was detected, 0.3 mgO₃/mgTOC₀ (Initial TOC) of ozone was consumed. When an ozone/hydrogen peroxide process was applied, additional COD_Cr was removed. And we elucidated that two following findings are important for the better performance of ozone/hydrogen peroxide process; those are to remove readily reactive organic compounds with ozone before the application of ozone/hydrogen peroxide process and to avoid the excess addition of hydrogen peroxide. Based on these two findings, we proposed a sequential process of ozonation and multi-stage ozone/hydrogen peroxide process and the appropriate addition of hydrogen peroxide. T-COD_Cr, TOC and ATU-BOD₅ were reduced to less than 7 mg/L, 6 mgC/L and 5 mg/L, respectively after total treatment time of 79 min. Furthermore, we discussed the transformation of organic compounds and the removal of organic compounds. The removal amount of COD_Cr and UV₂₅₄ had good linear relationship until the removal amounts of COD_Cr and UV₂₅₄ were 30 mg/L and 0.11 cm^?1, respectively. Therefore UV₂₅₄ would be useful for an indicator for COD_Cr removal at the beginning of the treatment. The accumulation of carboxylic acids (formic acid, acetic acid and oxalic acid) was observed. The ratio of carbon concentration of carboxylic acids to TOC remaining was getting higher and reached around 0.5 finally. Removal of TOC was observed with the accumulation of carboxylic acids. When unknown organic compounds (organic compounds except for carboxylic acids) were oxidized, 70% was apparently removed as carbon dioxide and 30% was accumulated as carboxylic acids. A portion of biodegradable organic compounds to whole organic compounds was enhanced as shown by the increase ratio of BOD/COD_Cr.     

Ozonolysis Post-Treatment of Anaerobically Digested Distillery Wastewater Effluent

ABSTRACT

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

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.     

Enhancing Biodegradability of Textile Wastewater by Ozonation Processes: Optimization with Response Surface Methodology

ABSTRACT

In this study, an ozonation process was used to increase biodegradability of textile wastewater by considering chemical oxygen demand (COD) and color removal. Response surface methodology was applied in order to determine the significance of independent variables which are initial pH, reaction time and ozone dose. While a biological oxygen demand (BOD)/COD rate of 0.315 was obtained at optimum conditions, which are pH 9, 75 min of reaction time and 26 mg/L ozone dose, color and COD removal was obtained at 74% and 39%, respectively. BOD/COD ratio value increased from 0.18 to 0.32 by ozonation process. In addition, k coefficient for BOD also increased from 0.21 to 0.30 d^?1.     

Effect of Catalytic Ozonation Coupling with Activated Carbon Adsorption on Organic Compounds Removal Treating RO Concentrate from Coal Gasification Wastewater

This paper reports a novel system of catalytic ozonation coupling with activated carbon adsorption for removing the organic compounds treating in the RO concentrate from coal gasification wastewater. The effect of ozone dosage, catalyst dosage, reaction time, influence pH, and temperature on organic compounds removal were examined for the processes. In the catalytic ozonation process, increasing solution pH, dosages ozone, and catalyst were statistically significant for improving the performance. In addition, the high salinity with chloride concentration of 15 g/L could reduce the catalyst specific surface area by 18%. Thus, high salinity showed negative influence on the catalytic effect in TOC removal. Regarding activated carbon adsorption process, modified activated carbon by NaOH revealed advantages in adsorbing organic compounds treating catalytic ozonation effluent. With the ozone dosage of 120 mg/L, catalyst dosage of 2.0 g/L, catalytic ozonation reaction time of 1 h, and modified activated carbon adsorption time of 1 h, the average TOC removal efficiencies were maintained at the stable level of 58% with the TOC concentration of 26 mg/L.     

Catalytic ozonation with non-polar bonded alumina phases for treatment of aqueous dye solutions in a semi-batch reactor

Semi-batch experiments were conducted to investigate the effects of catalyst type, pH, initial dye concentration and production rate of ozone on the catalytic ozonation of the dyes, namely Acid Red-151 (AR-151) and Remazol Brilliant Blue R (RBBR). The used catalysts were alumina, 25% (w/w) perfluorooctyl alumina (PFOA), 50% (w/w) PFOA and 100% (w/w) PFOA. The results showed that the overall percent dye removal after 30 min of the reaction was not affected significantly by the catalyst type. However, highest COD reduction was achieved by ozonation with alumina for AR-151, and 100% PFOA for RBBR at pH 13. The behavior of COD reduction with the increasing amount of perfluorooctanoic (PFO) acid amount can be explained by the enhancement of catalytic activity of PFOA with alkyl chains. For both of the dyes, the highest dye and COD removals were reached at pH 13. The overall dye reduction after 30 min of ozonation was almost independent of the initial dye concentration at relatively low values while at the higher concentrations, it changed with the initial dye concentration for both of the dyes. Similarly, COD reduction changed on a limited scale with the increasing initial dye concentration from 100 mg/L to 200 mg/L; however, an increase of initial dye concentration to 400 mg/L decreased the COD reduction significantly. All the studied production rates of ozone were sufficient to provide almost 100% dye removal in 30 min, whereas the COD removal percentage was increased gradually by the increasing ozone input to the reactor. The reaction kinetics for the ozonation of each dye with and without catalyst was investigated and discussed in the paper.     

Ozone oxidation of β-lactam antibiotic molecules and toxicity decrease in aqueous solution and industrial wastewaters heavily contaminated

In this work, ozone oxidation of the antibiotics amoxicillin (AMX), cephalexin, and ceftriaxone was investigated in different samples: (i) aqueous solutions (100 mg L^?1), (ii) an industrial wastewater containing AMX at 125 mg L^?1 (chemical oxygen demand 6000 mg O₂ L^?1), and (iii) a heavily contaminated industrial wastewater containing the antibiotics at a total concentration of 320 mg L^?1. High performance liquid chromatography, molecular absorption spectrophotometry in the ultraviolet/visible region, and total organic carbon measurements showed that ozonation of antibiotics solutions led to removal higher than 95% with 10–20% mineralization. Industrial wastewater also showed very good efficiency for antibiotic removal (80–98%) after ozonation. Moreover, Microtox® test showed 86% toxicity reduction for the industrial wastewater.     

Removal of phenolic compounds present in olive mill wastewaters by ozonation

The aim of this work is to study a pre-treatment process of olive mill wastewaters based on ozonation. The efficiency of the process depends on the removal of pollutants and on ozone mass transfer performance. In order to choose an appropriate gas/liquid contactor, the rate constants of three phenolic compounds (gallic acid, p-hydroxybenzoic acid and p-coumaric acid) were determined by using competition kinetic model. These constants, obtained at pH 5, were found to be high (from 3.8 × 10⁴ L/mol s to 2.9 × 10⁵ L/mol s), inducing a diffusion controlled regime (Ha > 3). Thus, to obtain an efficient ozonation process, gas/liquid contactor should be adapted to this regime. An ejector was chosen as gas/liquid contactor. In a first time, treatment of synthetic effluent containing the three phenolic compounds was performed to evaluate efficiency of the process. Experimental conditions were chosen to obtain a diffusion controlled regime (Ha > 3). It appeared that this gas/liquid contactor permits obtaining complete and fast removal of pollutants with a very efficient ozone mass transfer (up to 90% during removal of phenolic compounds). So, this process was used to perform the ozonation treatment of olive mill wastewaters from Sfax (Tunisia). It was proved to be very efficient: up to 80% of phenolic compounds were removed and ozone mass transfer reached 95% during this oxidation.     

Ozone Degradation of Cyclophosphamide – Effect of Alkalinity and Key Effluent Organic Matter Constituents

The influence of three effluent organic matter (EfOM) model compounds (alginic acid, peptone and natural organic matter-NOM) and alkalinity on the ozonation of cyclophosphamide (CPD) was investigated. The rate of ozone decay increased with increasing model compounds concentration in the order of peptone > NOM > alginic acid. Increasing alkalinity inhibited ozone decay at all concentrations of alginic acid and at low concentrations of NOM and peptone (DOC < 3 mg/L), while at high NOM and peptone concentrations the effect of alkalinity on ozone decay was minor. Presumably, ozone decay was mainly controlled by direct reaction with these two model compounds, resulting in ?OH (hydroxyl radical) formation yield of 29% and 19%, for peptone and NOM respectively. In the presence of alginic acid ?OH formation through a radical chain reaction resulted in a yield of 30%. Cyclophosphamide (CPD) removal decreased with increasing alkalinity and model compounds concentration (most pronounced for peptone and less pronounced for alginic acid); most likely due to increase in the scavenging effect on ?OH.     

Ozone/H2O2 Performance on the Degradation of Sulfamethoxazole

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

Pilot Study on Pre-Ozonation Enhanced Drinking Water Treatment Process

The enhancement of TOC, COD_Mn, and UV₂₅₄ reduction in the conventional drinking water treatment process by pre-ozonation was investigated in South China on treating dam source water with a pilot plant consisting of pre-ozonation, coagulation-sedimentation, and filtration units. Pre-ozonation enhanced the reduction of NOM in the conventional coagulation-sedimentation and filtration process, and the total removals of UV₂₅₄, COD_Mn and TOC were improved for 34.6%, 18.1% and 15.3%, respectively by the adoption of pre-ozonation under an ozone dose (in ozone consumption base) of 0.85 mg/L. The enhancement of UV₂₅₄ and COD_Mn removals was mainly achieved through direct ozonation on humic substances, and that for TOC removal was achieved through biodegradation in sand filtration. In comparison with the TOC removal of 38%, a removal of 49% was acquired for SDS-THM under a pre-ozonation dose of 0.80 mg/L, indicating the selective removal of THMFP. The reduction of SDS-THM paralleled the reduction of COD_Mn to a significant degree, suggesting that the COD_Mn might be an effective surrogate parameter for SDS-THM if the raw water does not contain the reductive inorganic matters. Although the source water contains 13.2–27.0μg/L bromide, the formation of bromate was negligible when the ozone dose was below 1.0 mg/L.     

Joint Treatment of Wastewater from Table Olive Processing and Urban Wastewater. Integrated Ozonation – Aerobic Oxidation

Integrated ozonation‐aerobic biodegradation of table olive wastewater (diluted 1:25 with synthetic urban wastewater) is presented as a suitable technology to purify this kind of effluent. Use of ozone is recommended as a pre‐treatment step since it shows a high reactivity toward phenolic compounds (found in this type of wastewater) reducing, at the same time, the alkalinity of the media for further biological processing. An ozone dose of 45 mg L^–1 (flow rate 20 L h^–1) for a period of 35 min has been found to achieve the following goals: decrease pH, decrease phenolic content, and increase of biodegradability. The aerobic oxidation process followed first order kinetics as measured by COD depletion profiles versus time. The Arrhenius expression k = 183exp(–2214/T) was obtained for experiments of ozonated wastewater biodegradation completed at different temperatures and neutral pH.     

Remediation of phenanthrene contaminated soils by nonionic surfactants enhanced soil washing coupled with ozone oxidation

In the present work, soil washing followed by ozone oxidation for remediation of phenanthrene (PHE) contaminated soils was investigated. The PHE removal efficiencies of TX-100 and Brij-35 at 3000 mg/L were 80.2% and 73.8%, respectively. In the ozone oxidation process, the oxygen supply rate was more rapid and the ozone concentration in the water rose quickly after 2 h. The degradation efficiencies for PHE, Brij-35, and TX-100 at 20 mg/L ozone concentration were 99%, 99%, and 45%, respectively. Our investigation suggests that coupling ozone oxidation with surfactant-enhanced soil washing is an effective method for removing hydrophobic compounds from soils.     

Systematic Analysis of the Biochemical Characteristics of Activated Sludge During Ozonation for Lowering of Biomass Production

Properties of activated sludge during ozonation were analyzed. The structure and surface characteristics altered with the increase of ozone dosage. At low ozone dosage, the floc structure was completely dismantled. Floc fragments reformed through reflocculation at an ozone dosage greater than 0.20 g O₃·g^?1 mixed liquor suspended solids (MLSS). Inactivation of microorganisms in the activated sludge mixture was caused by ozonation. Microbial growth decreased by up to 65% compared to the control. Simultaneously, 92.5% of nucleotide and 97.4% of protein in microbial cells of the sludge were released. Organic substance, nitrogen and phosphorus were released from the sludge during the ozonation process. The initial value of soluble chemical oxygen demand (SCOD) was 72 mg·L^?1. When the ozone dosage was 0.12 g O₃·g^?1 MLSS, the value of SCOD rapidly reached 925 mg·L^?1, increased by almost 12-fold. Simultaneously, 54.7% of MLSS was reduced. The composition of MLSS was changed, indicating that the inner water of cells and volatile organic substance decreased during the ozonation process.     

Heterogeneous Catalytic Ozonation of Refinery Wastewater over Alumina-Supported Mn and Cu Oxides Catalyst

An economical method was proposed to develop an efficient alumina-supported manganese (Mn) and copper (Cu) oxides (Mn-Cu-O/Al₂O₃) catalyst with a high surface area, 184.06 cm² g^?1. The catalyst was utilized for degradation refinery wastewater by heterogeneous catalytic ozonation. The effects of various operating variables including pH, ozone and catalyst dosages, and temperature were systematically investigated in detail to obtain the optimized conditions for accelerated degradation of refinery wastewater. The optimum values were as follows: ozone dose 50.0 mg L^?1, catalyst dose 3.0 g L^?1, initial pH = 6.8, T = 17 °C. Refinery wastewater samples were analyzed by chemical oxygen demand (COD) and the results indicated that kinetics of COD followed a pseudo–first-order degradation. Moreover, hydroxyl radical mechanism rather than absorption was proposed, indicating that the surface hydroxyl groups were the active sites that played a significant role in catalytic ozonation.     

Pilot Studies of Ozonation for Inactivation of Artemia salina Nauplii in Ballast Water

A pilot-plant study was conducted in the Republic of Croatia to determine the applicability of ozonation for inactivation of non-indigenous species and to provide necessary information regarding use of ozone as a ballast water treatment option. Nauplii of the brine shrimp Artemia salina were used as model organisms to investigate the efficacy of ozonation at three different ozone dosages (2.4, 3.7 and 10.9 mg L^?1). Mortality of Artemia nauplii at 98.6%, was achieved after 3 h of exposure in ozone-treated water with the highest ozone dosage. Our results indicated that ozonation is a promising treatment for controlling non-indigenous and potentially invasive species; however, to draw more general conclusions, several species with higher level of resistance to ozone are required and will be studied in the future.