O3 Process Research Articles

A framework to determine the optimum contact time and organic micropollutant removal efficiency of the ozone process applied in the context of Cape Flats Managed Aquifer Recharge Water Reclamation Plant

Final wastewater treatment plant effluent is widely recognised as a hazardous water source for human consumption as it may contain organic micropollutants and pathogens. The advanced processes required to adequately remove them are costly, and consequently, it is crucial to investigate how the associated costs can be optimised. One of the key treatment steps in the treatment train of the Cape Flats Managed Aquifer Recharge (MAR) water reclamation plant (WRP) is the advanced ozonation (O3) treatment process. The O3 process was assessed using the T10 and CSTR methods. The O3/TOC dose ratio was used as the main parameter to compare and relate various O3 treatment objectives and assessment methods. Furthermore, an O3 contact time optimisation was performed on the Cape Flats O3 process using capital and operation and maintenance (O&M) costing models, as well as process performance regression models. The optimum contact time, in terms of cost for 2–4 Log virus inactivation by ozone and 1–3 Log giardia inactivation by ozone, was determined to be between 5 and 7 min by the CSTR method, and 5 min by the T10 method. The optimum contact time, in terms of cost for 1–3 log inactivation of cryptosporidium by ozone, was determined to be between 8 and 18 min by the CSTR method, and between 6 and 13 min by the T10 method, depending on the treatment objective and O3 transfer efficiency. The O3 process of the Cape Flats MAR WRP can theoretically reduce more than 87% of the organic micropollutants in the Cape Flats Wastewater Treatment Works (WWTW) final effluent.

Multistage treatment for olive mill wastewater: Assessing legal compliance and operational costs

A treatment train for the remediation of a raw olive mill wastewater (OMW) was investigated, aiming to comply with the emission limit values (ELVs) for direct discharge into water bodies. The following stages were proposed: (i) pre-treatment (filtration and sedimentation), (ii) coagulation, (iii) biological oxidation, and (iv) advanced oxidation process (AOP). Under the best-operating conditions for coagulation (0.8 g L−1 of Al2(SO4)3, pH = 4.5), high removal of total suspended solids (TSS) (97%), turbidity (98%), and phenols (57%) was achieved, along with a decrease in the inhibition of the biological activity. A subsequent biological oxidation stage provided a high removal of organic matter (chemical oxygen demand (COD) removal of 73%). For the third stage, three AOPs were applied and compared – photo-Fenton with UVA radiation (PF-UVA), anodic oxidation (AO), and ozonation (O3). After 3 h of treatment, the PF-UVA process (pH = 2.8, [H2O2] = 400–500 mg L−1, [Total dissolved iron]0 = 100 mg L−1) allowed to meet the ELV for COD, but the other parameters exceeded the threshold, while O3 process (inlet concentration = 100 mg O3 Ndm−3, gas flow = 0.2 Ndm3 min−1) allowed to comply with phenols, TSS, and sulfate limits. The AO process (current density up to 200 mA cm−2) was the least efficient AOP for all studied parameters. The operational costs for the coagulation and biological oxidation stages were estimated at 1.20 € m−3. Regarding the most effective AOPs, ozonation presented an estimated cost 2.3-fold higher than PF-UVA (11.9 € m−3vs. 5.2 € m−3).

A comprehensive study on simultaneous enhancement of sludge dewaterability and elimination of polycyclic aromatic hydrocarbons by Fe2+ catalyzing O3 process

Simultaneous removal of polycyclic aromatic hydrocarbons (PAHs) in the process of enhancement of sludge dewaterability via oxidation of hydroxyl radicals (•OH) and flocculation of Fe3+ by Fe2+-catalyzing O3 were investigated as a novel research focus. The results showed that capillary suction time (CST) and water content of dewatered sludge cake (Wc) were reduced from 57.9 s and 85.1% to 13.6 s and 69.65% under the optimum usage of 60 mg/g dry solids (DS) O3 and 80 mg/g DS FeSO4, respectively. The relevant dewatering mechanism of Fe2+-catalyzing O3 treatment was elucidated. It was found that extracellular polymeric substances-bound (EPS-bound) and intracellular water was dramatically released through destroying sludge cells and EPS gel-like structure by produced •OH. In addition, the results of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and 13C NMR spectroscopy revealed that •OH oxidized and mineralized hydrophilic organic matters intensifying hydrophobicity of sludge surface. Moreover, Fe3+ generated by oxidation of Fe2+ agglomerated fragmented fine particles into large aggregates and decreased exposure of hydrophilic sites by neutralizing negative charge, which promoted water-solids separation. Meanwhile, sludge surface roughness was decreased which was determined by material type upright confocal laser microscope (CLM). As a consequence, •OH and Fe3+ were mainly responsible for enhancement of sludge dewaterability. Moreover, more than 40% of removal rate of PAHs was accomplished by Fe2+-catalyzed O3 treatment mitigating the environmental risks of PAHs spread.

Catalytic ozonation performance and mechanism of Mn-CeOx@γ-Al2O3/O3 in the treatment of sulfate-containing hypersaline antibiotic wastewater

Herein, we attempted to apply an alumina-based bimetallic (Mn-Ce) catalyst as an O3 activator and explored the feasibility of the treatment of hypersaline organic wastewater. Compared with independent O3 (35.00 ± 4.20%), mineralization of ciprofloxacin (CIP) under the Mn-CeOx@γ-Al2O3/O3 (MCAO) process was elevated to 76.04 ± 2.30%. The synergetic corporation among multivalence redox pairs of Mn (III)/Mn (IV), Ce (III)/Ce (IV) promoted the protonation of the surface hydroxyl group (S-OH2+), and subsequently the dominant reactive oxygen species in the MCAO process, OH and O2−, were generated rapidly. However, the mineralization of CIP decreased in MCAO/SO42− system due to the formation of SO4−, which reacted with CIP more slowly (8.4 × 108 M−1 s−1) than OH (4.1 × 109 M−1 s−1). In MCAO/SO42−/Cl− mixture saline conditions, mineralization of CIP was improved at low Cl− concentration (0.5 wt%) due to the generation of Cl, while inhibited with excessive Cl− (≥1.5 wt%) owing to the formation of residual chlorides (Cl2, Cl2− and ClO−). Meanwhile, the MCAO process possessed promising capability to remediate hypersaline wastewater containing dyes, phenol and pesticides, as well as actual salinity-rich wastewater. Based on the above, the present study would provide new insights into hypersaline organic wastewater treatment by the MCAO process.

Characterizing the degradation of refractory organics from incineration leachate membrane concentrate by VUV/O3

In this study, we used a combined vacuum-ultraviolet (VUV) and O3 process treating the chemical precipitation pre-treated incineration leachate membrane concentrate to further decompose substantial refractory organics which led to membrane organic fouling in the subsequent membrane distillation process. The highest removal of COD (88.1%) was achieved when 50 mg/min of O3 dosage was used at a pH of 11.5–12. Multi-spectrum methods, molecular weight distribution (MW), gas chromatography-mass spectrometry (GC–MS), two-dimensional correlation spectroscopy (2D-COS), and hetero-spectral 2D-COS were used to investigate the organics degradation mechanism. The combined action of O3 and hydroxyl radicals (•OH) effectively degraded macromolecular organics with high aromaticity and high conjugation (mainly distributed at 1–3 kDa) into aliphatic products with lower molecular weight (<1 kDa) and simple structures. The order of organics that were oxidized were humic-like acids > fulvic-like acids > protein-like substances. Organic acids (acetate, propionate, and butyrate) also accumulated in the VUV/O3 systems.

Life cycle assessment of sequential and simultaneous combination of electrocoagulation and ozonation for textile wastewater treatment

Electrocoagulation (EC), ozonation (O3) and their combination have attracted the interest of researchers for textile wastewater treatment. However, the lack of an exhaustive comparison among the different approaches, including also the evaluation of their impact on the environment, has hampered full-scale application. As a result, in this study, environmental impacts of simultaneous (-) and sequential (→) combination of EC and O3 were analyzed and compared to EC and O3 alone processes. The effect of type of electrode (Fe or Al) was evaluated in the EC process. The processes were investigated at lab scale and compared through Life Cycle Assessment (LCA), using ReCiPe midpoint and endpoint methods. EC process with Al electrodes resulted in the lowest impact for all the environmental categories due to the lower energy consumption, while O3 process resulted in the highest impact being an energy- and oxygen-intensive process. In particular, when the processes removed COD below 60 mg/L, the higher CO2 emission as the key midpoint method indicator was expected for O3 (81.4 g CO2 eq), while the lower was measured for EC(Al) (1.4 g CO2 eq). Moreover, the higher effect on Human Health, as the key endpoint method indicator, was obtained for O3 (6.65E-6), and the lower one was for EC(Al) (1.35E-7). The environmental impact of simultaneous combination (EC-O3) is still high due to high ozonation time. In sequential combination option (EC→O3), O3 treatment time was very short and environmental impacts decreased significantly besides high purification performance (approximately 50% COD removal). It is worthy to note that the environmental impacts of all processes are strongly related to energy and chemical consumption, that emphasize the importance of optimizing operation conditions. LCA showed that the sequential combination of EC and O3 is the most sustainable solution for textile wastewater treatment among the investigated processes and it can be successfully applied at industrial scale.

Evaluation and Prediction of Removal Efficiency of Pharmaceuticals in the Simulated O3 and UV/H2O2 Process for Drinking Water Treatment Process in the Downstream of Nakdong River

Objectives : In the case of pharmaceuticals with high possibility of inflow into the large drinking water treatment plant (DWTP) located in the downstream of the Nakdong River, we tried to evaluate the removal efficiency of pharmaceuticals in the both ozone (O3) and the UV/H2O2 treatment as an alternative of post-O3 process. It was intended to be used as data for the advanced WTP project by prediction of the removal efficiency in the O3 and UV/H2O2 processes with varying water quality conditions.Methods : O3 and UV/H2O2 process were performed for 19 kinds of pharmaceuticals in the sand-filtered water of DWTP. In order to evaluate the removal efficiency in deionized water (DI) and sand-filtered water (SFW) matrices, 19 pharmaceuticals were spiked at a concentration of 100 ng/L, respectively. In the O3 process, the specific O3 dose was 0.1∼2.0 gO3/gDOC (0.25∼5.0 mgO3/L). In the UV/H2O2 process, H2O2 (5 and 10 mg/L) was added to the sample before UV was irradiated (0∼1,500 mJ/cm2).Results and Discussion : In the case of simulated post-O3 process, the removal efficiency of high-ozone reactive pharmaceuticals (kO3 6.5×102∼2.6×106 M-1 s-1) was up to 92% at the specific O3 dose of 0.2 gO3/gDOC. However, the removal efficiency of iopromide (IPM) and primidone (PRM) was only 36∼45% in the same O3 dose (0.2 gO3/gDOC) due to the low O3 reactivity (kO3 &lt; 1 M-1 s-1). A specific O3 dose of 2.0 gO3/gDOC (=5 mgO3/L) was required to achieve a removal efficiency of over 90% for IPM and PRM, indicating that these O3-refractory pharmaceuticals are difficult to control by O3 process. In the case of simulated UV/H2O2 (10 mg/L H2O2) process, the removal efficiency of 19 pharmaceuticals at the UV fluence of 500 and 1,000 mJ/cm2 were 63∼99% and 87∼99%, respectively, and caffeine (CFN) had the lowest removal efficiency. For the O3-refractory pharmaceuticals (i.e., IPM and PRM), the removal efficiency was higher in the UV/H2O2 process than that in the O3 process due to the high reactivity with OH radical (kOH = 3.3×109 and 5.2×109 M-1 s-1). Prediction of removal efficiency for pharmaceuticals in the O3 and UV/H2O2 process was performed using chemical kinetics model to evaluate the change in removal efficiency with varying DOM concentration. As a result of prediction model for O3, when the DOM concentration increased from 1.5 to 3.0 mg/L, the removal efficiency of IPM and PRM decreased by 22∼24% and 15∼24%, respectively. In the case of UV/H2O2 process (10 mg/L H2O2 and UV fluence of 500~1,000 mJ/cm2), the removal efficiency of 16 kinds of pharmaceuticals was reduced by 0∼29%, and the degree of reduction in the removal efficiency of CFN was the highest.Conclusions : As a result of evaluation and prediction of the removal efficiency of pharmaceuticals in the O3 and UV/H2O2 treatment processes, it is confirmed that the possibility of applying the UV/H2O2 treatment as an alternative process to the O3 to abatement of pharmaceuticals.

Effects of organic matter, ammonia, bromide, and hydrogen peroxide on bromate formation during water ozonation

Ozone is widely applied for disinfection in drinking water treatment and the disinfection by-product bromate would be produced during the ozonation of bromide-bearing water. Hydrogen peroxide (H2O2) addition could effectively control the formation of bromate. However, the bromate depression performance would be impacted by water qualities. In this study, typical source water containing bromide in eastern China was selected to investigate bromate depression effect under different organic matter, ammonia and bromide concentrations during the H2O2–O3 process. The results display that organic matter, ammonia and bromide concentration could influence the formation of bromate significantly. As tyrosine was applied to increase the dissolved organic carbon (DOC) concentration of source water by 2.0 and 3.0 mg/L, the total concentration of bromate produced decreased gradually as the H2O2/O3 (g/g) doses increased from 0 to 1.0 and bromate concentration could be controlled below 10 μg/L as H2O2/O3 (g/g) was 0.5 and 1.0. As ammonia concentration increased by 0.1 and 0.5 mg/L, lower H2O2/O3 (g/g) doses would lead to an increase in bromate generation. As more H2O2 was added in water, the bromate formation would be suppressed. The increase of bromide concentration induced higher bromate formation. When the bromide concentration increased by 50 and 200 μg/L, bromate concentration was 10.7 μg/L and 41.2 μg/L respectively at the H2O2/O3 (g/g) of 1.0, higher than the standard level. As 200 μg/L of bromide was added to the water, bromate concentration increased significantly and then decreased as H2O2/O3 (g/g) increased and more H2O2 would be needed for bromate control.

Ultrafine Particle Removal in the Wafer Cleaning Process Using an Aqueous Solution with a High Concentration of Dissolved O&lt;sub&gt;3&lt;/sub&gt; and HF

Sulfuric Peroxide Mixture (SPM, H2SO4 + H2O2) has been widely used in semiconductor manufacturing processes due to its high reactivity and attractive price. However, SPM releases SO42- ions that can be high impact on the environmental contaminations. Therefore, the SPM process requires a high cost wastewater treatment. So, the development of alternative chemicals has been becoming an important task in the semiconductor manufacturing process. In this paper, we evaluated the feasibility of replacing SPM with dissolved ozone water (DIO3) in the wafer cleaning process, and confirmed that the Particle removal efficiency (PRE) was improved around 68% by mixing with diluted hydrofluoric acid (DHF). And, the PRE was also increased when the concentration of ozone in dissolved ozone water increased. Additionally the PRE was improved up to 98% by combining physical cleaning after O3 process.

Nitrogen selectivity upon catalytic ozonation of ammonia with CTAB-NiO catalyst

In this work, CTAB-NiO catalyst was prepared by solid-state method and employed for oxidizing ammonia (NH4+) in aqueous solution by catalytic ozonation. In order to obtain high N2 selectivity, the effects of operating parameters on catalytic ozonation of ammonia were investigated in detail. Experimental results revealed that initial pH played a crucial role both in single O3 process and CTAB-NiO/O3 process, especially in the decomposition of O3 and the pathway of ammonia being oxidized into final products. Meanwhile, CTAB-NiO catalyst exhibited good performance in treating low concentration NH4+-containing wastewater from rare earth smelting. The results of qualitative and quantitative analysis of the reaction product distribution showed that in the CTAB-NiO/O3 system, about 98 % ammonia mainly converted to N2 at 293 K and ambient atmospheric pressure, with a selectivity of 76 %. The mechanism of catalytic ozonation of ammonia in aqueous solution was investigated by adding tert-butanol to the CTAB-NiO/O3 system. The catalytic ozonation of ammonia in aqueous solution was primarily due to the synergistic effect between the active ingredient from CTAB-NiO catalyst and hydroxyl radicals (·OH) generated by ozonolysis.

Synergistic effects of ultrasonic-assisted ozonation on the formation of hydrogen peroxide

Ultrasonic (US) - assisted ozonation process is an efficient way to enhance the mineralization of organic pollutants in water treatment, in which radical-mediated chain reactions from the ozone (O3) initiation and propagation are enhanced by ultrasonic irradiation. In this work, the evolution and dissociation of H2O2 under different initial pH, in the presence of different active oxidation species scavengers were investigated in the ultrasonic-assisted ozonation process. Variation of H2O2 concentration in ultrapure water, reverse osmosis water, tap water and seawater was also explored. The results showed that HO2¯ was involved in the initiation and propagation of ozone decomposition, and the synergistic effect of ultrasonic irradiation promoted the generation of H2O2 by 54.8%. More than 90% of H2O2 was largely inhibited by the addition of •OH and •O2¯ scavengers, indicating that the primary work of H2O2 generation did not directly involved ozone irradiation by ultrasound. In reverse osmosis treated water, the moderate organic predecessors (0.08 mg/L TOC) promoted H2O2 generation by 26% in O3 process and 29% in O3+US process. This study investigated factors that influence H2O2 evolution during ultrasonic ozonation, leading to methods for enhancing the transformation of ozone and producing hydroxyl radical during water treatment.

Catalytic ozonation assisted by Fe3O4@SiO2@TiO2 in the degradation of Aniline from aqueous solution: modelling and optimisation by response surface methodology

ABSTRACT This work investigated the modelling and optimisation of Aniline degradation using catalytic ozonation with Fe3O4@SiO2@TiO2 nanocomposite based on the response surface methodology (RSM). The sol-gel method was used to synthesise the magnetic nanoparticleFe3O4@SiO2@TiO2. The catalyst characteristics were analysed by FE-SEM, EDS, XRD, VSM and TEM. Effects of pH, contact time, catalyst loading, Aniline concentration, and radical scavengers on the degradation efficiency of Aniline were evaluated. Results showed that 93.35% removal efficiency of Aniline and 79.3% TOC reduction were obtained by Fe3O4@SiO2@TiO2/O3 process under optimised conditions (contact time = 60 min, catalyst loading = 1.7 g/L, pH = 10.0 and concentration of Aniline = 15 mg/L). Results proved that hydroxyl radicals were dominant radical groups for Aniline degradation in the catalytic ozonation process. After eight continuous using cycles, the results indicated that the Aniline removal efficiency decreased to <6%.In brief, the synthesised Fe3O4@SiO2@TiO2is a well synthesised, stable, efficacious and reusable catalyst and could be a desirable alternative material for wastewaters treatment containing Aniline.

Synthesis of CeOx@SiO2 with tandem effect of mass transfer and activation for enhancing sulfanilamide degradation with ozone

In this work, a hollow mesoporous CeOx@SiO2 was synthesized and used to promote sulfanilamide (SA) mineralization in ozonation. SA mineralization was promoted to 68.2% by O3/CeOx@SiO2 in 120 min, but only 30.0% in O3 process. O3/CeOx@SiO2 behaved the better at acidic and alkaline condition than that at neutral condition. CeOx@SiO2 had the great ability in enhancing O3 utility rate. Silanol (SiOH) in pore channel of SiO2 shell was non-reactive with O3 but could provide transmission way for O3 to reach the inner CeOx core. Lewis sites, oxygen vacancies and surface hydroxyl groups induced by CeOx favored for the activation of O3. The excess electron at oxygen vacancies would be transferred to the absorbed O3 molecular, which then generated reactive oxygen species (ROS) to mineralize SA. Hydroxyl radicals (OH) and superoxide radicals (O2−) were the main ROS, which were recorded by EPR. The interfacial electron transfer process was revealed by LSV and ESI characterizations. SA degradation intermediates were also identified by HPLC-MS and IC, a possible degradation pathway was proposed. Moreover, CeOx@SiO2 showed a good reusability, no obvious decline of TOC removal was found in four times’ uses. Water matrix would complete ROS with SA, which inhibited the SA removal of both O3 and O3/CeOx@SiO2 processes, but the better TOC removal efficiency was still obtained by O3/CeOx@SiO2 in actual water.

Combined ultrasound-ozone treatment for reutilization of primary effluent\u2014a preliminary study

The present work is a preliminary study on the potential of low-frequency ultrasound irradiation coupled with O3 process for the disinfection of a primary effluent from a municipal wastewater treatment plant preserving nutrient levels (in particular nitrogen and phosphorous), for its possible reuse in civil, industrial, and agricultural sectors. The treated water could be reused, after appropriate dilution, contributing to the circular economy perspective and reducing the need for both chemical fertilizer addition and freshwater supply. The effect of different specific ultrasonic energies and ozone doses was assessed on a bench-top system, composed of an ultrasonic reactor and a semi-batch ozonation vessel. The results showed that the combined US-O3 process produces a good removal efficiency regarding soluble Chemical Oxygen Demand, sCOD (ca. 60%), anionic surfactants (ca. 50%), and formaldehyde (ca. 50%), and an optimal abatement for Methylene Blue Active Substances (MBAS, > 90%). The process also reached high disinfection performances, obtaining 4 logs for E. coli and 5 log abatement for Total Coliforms. The high removal efficiency is matched by an outstanding retention of nutrients (total nitrogen and orthophosphate) highlighting a high potential value for agricultural reuse of the treated primary effluent, with possible significant saving of chemical fertilizers. It was concluded that low-frequency ultrasound pre-treatment, combined with ozonation, could be a useful process for primary effluent recovery for several purposes. Further studies are expected to be planned and executed to evaluate system scale-up feasibility.

Controllable p‐to‐n Type Conductance Transition in Top‐Gated Graphene Field Effect Transistor by Interface Trap Engineering

AbstractModulating the electronic property of graphene by doping is essential for its device and circuit applications. Unfortunately, controllable p‐ and n‐type doping in top‐gated graphene field effect transistor (GFET) is reported. Here, the O3‐based atomic layer deposited Al2O3 layer as top gate dielectric is chosen. The epoxide functional group formed in the O3 process serves as effective interface trap sites. As the sweeping range of top gate voltage increases, the Dirac point position of GFET moves from positive voltage to negative voltage. The shift of the Dirac point voltage indicates the doping transition of graphene from p‐type to n‐type. The gate voltage dependent doping can be attributed to the charge exchange between graphene and interface trap sites. Furthermore, a trap‐dependent charge model is proposed to explain the transport mechanism in the doping process. This approach is promising to produce the complementary p‐ and n‐type top‐gated GFET for multiple applications.

Effective removal of contaminants from biotreated leachate by a combined Fe(III)/O3 process: Efficiency and mechanisms

Refractory organics and toxic metals are still the main contaminants in the landfill leachate effluents from membrane bioreactors (MBRs) (expressed as biotreated leachate). In this study, a combined Fe(III)/O3 process was employed for the removal of multiple contaminants from a biotreated leachate in Qingdao city, China. Effects of ozone dose, Fe(III) dose, initial pH and reaction time on the removal efficiency of refractory organics were systemically investigated. The degradation mechanisms of organics were discussed based on a combination of microscopic and spectroscopic analyses. In addition, the removal efficiency of toxic metals from biotreated leachate was also performed. The results indicated that refractory organics in the leachate were effectively degraded in the Fe(III)/O3 system. The removal efficiencies of COD, TOC and UV254 were 80.23%, 74.85% and 85.01%, respectively, under the following optimum operational conditions: O3 dose of 100 mg/min, Fe(III) dose of 6 g/L, reaction time of 25 min, and initial pH of 6.5. At this conditions, the effluent COD and BOD5 were satisfied the discharge standard of pollutants to open seas in Qingdao city, China. Spectroscopic analysis suggested that refractory organics in the leachate were effectively destroyed and mineralized during the Fe(III)/O3 process. Additional, in-situ formation of Fe-containing particles (mainly as Fe(OH)3) contributed to the adsorptive removal of organics and toxic metals (i.e., Cu, Ni, As, Cr, Pb and Zn).

Removal of sulfadiazine from simulated industrial wastewater by a membrane bioreactor and ozonation

Ozonation can be used as a polishing treatment for degrading low-concentration pharmaceutical compounds recalcitrant to biological treatment, when large amounts of biodegradable organics have been previously removed by biological processes. Nevertheless, a systematic investigation has not yet been carried out for the coupled MBR + O3 process through an experimental design approach. Thereby, the purpose of this study is to evaluate the performance of different processes (membrane bioreactor-MBR, ozonation; and integrated MBR + O3) for removing the antibiotic sulfadiazine (SDZ) from a synthetic wastewater matrix of industrial interest. The MBR behavior was monitored over seven months for different parameters (pH, temperature, permeate flow, transmembrane pressure, biological oxygen demand-BOD5, chemical oxygen demand-COD, total organic carbon-TOC, solids, and SDZ concentration). Additionally, the amount of SDZ sorbed onto the sludge was characterized, an issue which is scarcely addressed in most research works. Ozonation experiments were conducted in batch mode in a 2-L glass reactor provided with openings for gas flow. For the MBR + O3 process, the effects of gas flow rate (0.1–1.5 L min−1) and inlet ozone concentration (4–12 mg L−1) on SDZ removal from the MBR permeate were systematically assessed using a Doehlert experimental design and response surface methodology. The results indicated that the MBR system showed good performance regarding organic matter removal efficiency, evaluated in terms of BOD5 (91.5%), COD (93.1%) and TOC (96.3%). In contrast, SDZ was partially removed (33%) by the MBR; in that case, the results indicated that the antibiotic was moderately removed with the sludge and partially biodegraded. In turn, the MBR + O3 system showed excellent performance for removing SDZ (100%), TOC (97%), BOD5 (94%) and COD (97%). The statistical analysis confirmed that the influence of ozone gas flow rate upon the SDZ removal rate was more important than that exhibited by inlet ozone concentration. Therefore, coupling MBR and ozone can be considered a promising alternative for point source treatment of antibiotic production wastewater.

Evaluation of chemistry and key reactor parameters for industrial water treatment applications of the UV/O3 process

In this study, the main influence factors of combined UV/O3 process in practical industrial application were explored through laboratory trials and industrial pilot tests. Dimethyl phthalate (DMP) was analyzed as the research subject through different experiments in laboratory. The degradation effect of organic compounds by O3 and UV/O3 processes in different air distribution methods was compared independently, and the mechanism of free radical generation by the two processes was analyzed. This study found that the combined UV/O3 process for organic matter mineralization is clearly better than that of independent effect of O3 process as mixed gas-liquid distribution method was superior to the bubble aeration method. The experimental conditions included inlet O3 concentration between 70 and 75 mg/L, reactor internal relative pressure at 0.3 MPa, contact reaction time of 12 min, DMP mineralization efficiency reaching 63.07%. The calculated dosing ratio of O3 in the dynamic experiment was around 0.74 mg CODCr/mg O3. The results showed that the best effect in wastewater treatment was achieved when the conditions of ultraviolet lamp irradiation intensity and the O3 dosage reached 822.88 W/m2 15 mg/L and utilized in conjunction with biochemical reactions. The resulting CODCr concentration of effluent reached 39.8 mg/L. Finally, it is determined that the main influence factors affecting the economically efficient operation of UV/O3 process were the efficient O3 distribution mode, control of the relative pressure within the reactor, proportion of ozone addition and light source configuration.

Enhanced triallyl isocyanurate (TAIC) degradation through application of an O3/UV process: Performance optimization and degradation pathways

Triallyl isocyanurate (TAIC, C12H15N3O3) has featured in wastewater treatment as a refractory organic compound due to the significant production capability and negative environmental impact. TAIC degradation was enhanced when an ozone(O3)/ultraviolet(UV) process was applied compared with the application of an independent O3 process. Although 99% of TAIC could be degraded in 5 min during both processes, the O3/UV process had a 70%mineralization rate that was much higher than that of the independent O3 process (9%) in 30 min. Four possible degradation pathways were proposed based on the organic compounds of intermediate products identified during TAIC degradation through the application of independent O3 and O3/UV processes. pH impacted both the direct and indirect oxidation processes. Acidic and alkaline conditions preferred direct and indirect reactions respectively, with a pH of 9 achieving maximum Total Organic Carbon (TOC) removal. Both CO32– and HCO3– decreased TOC removal, however only CO32– negatively impacted TAIC degradation. Effects of Cl– as a radical scavenger became more marked only at high concentrations (over 500 mg/L Cl–). Particulate and suspended matter could hinder the transmission of ultraviolet light and reduce the production of HO$ accordingly.

Activated carbon catalyzed ozonation (ACCO) of Reactive Blue 194 azo dye in aqueous saline solution: Experimental parameters, kinetic and analysis of activated carbon properties

Comparative study of Reactive Blue 194 (RB194) degradation using activated carbon catalyzed ozonation (ACCO) as a hydroxyl radical-based advanced oxidation processes (HO-AOPs) and single ozonation (O3) processes was investigated in this study. Furthermore, the effect of chloride ion (Cl−) on the dye reduction and mineralization was evaluated at different pH values. ACCO was more successful in the reduction of UV254 absorbance and chemical oxygen demand (COD) removal. In ACCO, the dye reduction was marginally increased with adding NaCl concentration from 5 to 50 g/L; while in O3 process, no significant differences were found. In ACCO, higher dye removal rate could be attributed to the production of reactive chlorine species. The results exhibited that temperature elevation promoted color, aromaticity, and COD removal in the ACCO process. Regeneration of activated carbon by ozone modified surface characterization through addition of acidic oxygen groups. In summary, the ACCO process can be suggested as a promising technology for dye removal from saline industrial wastewaters.