Differentiating ozone direct and indirect reactions on decomposition of humic substances

Advancements in Inorganic Membrane Filtration Coupled with Advanced Oxidation Processes for Wastewater Treatment

Membrane filtration is an effective water recycling and purification technology to remove various pollutants in water. Inorganic membrane filtration (IMF) technology has received widespread attention because of its unique high temperature and corrosion resistance. Commonly used inorganic membranes include ceramic membranes and carbon-based membranes. As novel catalytic inorganic membrane processes, IMF coupled with advanced oxidation processes (AOPs), can realize the separation and in situ degradation of pollutants, thus mitigating membrane contamination. In this paper, the types and performance of IMF are discussed. The influencing factors of inorganic membranes in practical wastewater treatment are summarized. The applications, advantages, and disadvantages of the coupled process of IMF and AOPs are summarized and outlined. Finally, the challenges and prospects of IMF and IMF coupled with AOPs are presented, respectively. This contributes to the design and development of coupled systems of membrane filtration with inorganic materials and IMF coupled with AOPs for practical wastewater treatment.

Comprehensive review of industrial wastewater treatment techniques

Water is an indispensable resource for human activity and the environment. Industrial activities generate vast quantities of wastewater that may be heavily polluted or contain toxic contaminants, posing environmental and public health challenges. Different industries generate wastewater with widely varying characteristics, such as the quantity generated, concentration, and pollutant type. It is essential to understand these characteristics to select available treatment techniques for implementation in wastewater treatment facilities to promote sustainable water usage. This review article provides an overview of wastewaters generated by various industries and commonly applied treatment techniques. The characteristics, advantages, and disadvantages of physical, chemical, and biological treatment methods are presented.

Treatment of organic pollutants in coke plant wastewater by micro-nanometer catalytic ozonation, A/A/O and reverse osmosis membrane

Coking wastewater has a complex and highly concentrated chemical composition which is toxic and does not biodegrade easily. Treating the organic pollutants in this wastewater is very challenging. The toxic substances in this wastewater make traditional biotechnological treatments inefficient. Current wastewater treatment studies are based on unit processes, and no full process studies could be found. This study used the micro-nanometer catalytic ozonation process as a pretreatment unit, and reverse osmosis membrane treatment as a depth processing unit to improve the effect of the coking wastewater degradation. The micro-nanometer catalytic ozonation pretreatment greatly improves the biodegradability of the coking wastewater and promotes the coking wastewater degradation in the anoxia/anaerobic/oxic (A/A/O) system. The integrated coagulation air flotation-micro-nanometer catalytic ozonation-A/A/O-reverse osmosis membrane system can remove 98% of the chemical oxygen demand, which meets the direct emission standard of the new national standard (China). The dominant genera in the A/A/O biochemical reactor were Thioalkalimicrobium, Proteiniphilum, Azoarcu, Bacillus, Fontibacter, and Taibaiella. This work provides a novel approach for the degradation of high-concentration organic wastewater and lays a solid foundation for the restoration of environmental water bodies.

Removal of Micropollutants by Ozone-Based Processes

Micropollutants and emerging substances pose a serious problem to environmental sustainability and remediation, due to their widespread use and applications in everyday life. This group of chemicals is diverse but with common toxic and harmful properties. Their concentration in the environment is often very low; however, due to their recalcitrant nature, they are persistent in air, water, and soil. From an engineering point of view, the challenge is not straightforward. It is difficult to remove these contaminants from complex mixtures of substances by conventional methods used in wastewater and drinking water treatment. Ozonation and ozone-based AOPs are accepted processes of degradation of resistant substances or at least enhancement of their biodegradability. The aim of this review paper is to present research trends aimed at solving problems in the research and application of ozone-based processes in the removal of micropollutants from wastewater, thus preventing leakage of harmful substances into surface water, soil, and groundwater and facilitating the reuse of wastewater. Priority substances, micropollutants and emerging pollutants, as well as processes and technologies for their transformation and elimination, are briefly specified. Results obtained by the authors in solving research projects that were aimed at eliminating selected micropollutants by ozonation and ozone-based AOPs are also presented. This review focuses on selected alkylphenols, petroleum substances, and organochlorine pesticides.

Cysteine enhanced degradation of monochlorobenzene in groundwater by ferrous iron/persulfate process: Impacts of matrix species and toxicity evaluation in ISCO

Monochlorobenzene (MCB), a solvent and synthetic intermediate, has been widely detected in groundwater at industrial contaminated sites. Cysteine (Cys) enhanced Fe²⁺/persulfate (Fe²⁺/Cys/PS) process with high degradation efficiency of organic pollutants has the potential for in-situ chemical oxidation of MCB. In this study, we systematically explored the impacts of common anions (CO₃^2-, HCO₃^-, SO₄^2-, NO₃^-, NO₂^-, PO₄^3-, HPO₄^2-, H₂PO₄^-, Cl^-, Br^-), cations (NH₄⁺, Mg²⁺, Al³⁺, Mn²⁺, Cu²⁺) and natural organic matter (NOM) on the degradation kinetics of MCB by the novel Fe²⁺/Cys/PS process and evaluated the ecotoxicity. The results showed that the removal of MCB in absence of matrices was enhanced by Cys due to its reduction and complexation ability. All of the anions inhibited the MCB degradation through the scavenging of SO₄^•- and HO^•, though the inhibition degree of SO₄^2-and NO₃^- was slight. Cations such as NH₄⁺, Mg²⁺ and Al³⁺ hardly interfered with the reaction. Low concentrations of Cu²⁺ and NOM promoted the MCB oxidation, but the promotion strength weakened and turned into inhibition with the increased concentration of Cu²⁺ and NOM. The toxicity assessment of the transformation products (TPs) in the presence of Cl^- and Br^- based on the quantitative structure-activity relationships model showed the potentially higher toxicity of some TPs than their parent MCB. These results indicate that groundwater matrices may interfere with the MCB oxidation process. To accurately evaluate the effects of groundwater matrices on Fe²⁺/Cys/PS process for MCB oxidation and its potential toxicity, the field tests should be carried out in the future.

Behavior of trace elements and micronutrients in manure digestate during ozone treatment

Digestate treatment techniques have recently been proposed as a strategy to increase the ultimate biogas yield from dairy manure and to improve the digestate quality as an organic fertilizer. These studies however rarely take the trace elements (TE) and nutrient partitioning into account. This study focusses on ozone treatment (5-40 g O₃ kg^-1 Total Solids (TS)) as a digestate treatment technique to control the concentration of TE and nutrients in the liquid phase of the digestate. Controlling the TE and nutrient concentrations in the liquid and solid digestate can improve the agronomic value of dairy manure digestate. The ozone concentration of the gas stream entering reactor was 48.53 g O₃/Nm³ or 3.4% w/w O₃ in O₂-gas. The experiments were repeated using pure oxygen gas to investigate its influence. The results from ozonation and oxygenation of the dairy manure digestates revealed that O₃ treatment up to 40 g O₃ kg^-1 TS did not have a more pronounced effect on the biochemical parameters compared to supplementation of pure O₂. Ozonation of the digestate and the supernatant showed that the TE concentration in the liquid phase followed a parabolic profile. The observed initial increase in this parabolic profile was explained by the release of TE from the organic matter to the supernatant causing an increase in TE concentration, followed by a decrease due to precipitation of TE as hydroxides and sulfides, due to the increasing pH and sulphur concentrations.

Adsorption - Membrane process for treatment of stabilized municipal landfill leachate

The aim of this study was to investigate the efficiency of removal of difficult-to-biodegrade organic compounds from real stabilized landfill leachate with a membrane process alone and in combination with powdered-activated-carbon (PAC) adsorption. For filtration, ceramic membranes were used. The characteristics of the raw leachate were 788 mg COD/L and color of 0.4458 cm^-1. With all combinations of PAC-adsorption and a membrane process (MF, UF, fine-UF) and with fine-UF alone, leachate treatment was highly efficient. For each membrane, treatment was more efficient when the membrane process was combined with PAC addition. This means that adsorption (PAC dose 3 g/L, adsorption time 30 min) made the largest contribution to leachate treatment (COD and color removal efficiency of 73.1% and 94.4%, respectively). In all cases, organic particles bigger than 100 kDa were removed most efficiently, whereas particles smaller than 3 kDa were removed least efficiently. The efficiency of leachate treatment with PAC + MF, PAC + UF and PAC + fine-UF did not differ significantly (>87% COD and > 97% color). With regard to membrane flux, however, these combinations can be ranked in the following order: PAC + MF > PAC + UF > PAC + fine-UF. Therefore, PAC + MF (0.3 MPa) was selected as the most effective solution (COD and color removal efficiencies of 87.8% and 97.2%, respectively; permeate flux of 167.6 L/(m²∙h)), as it combined efficient pollutant removal with low membrane pressure.

Ozone-driven processes for mature urban landfill leachate treatment: Organic matter degradation, biodegradability enhancement and treatment costs for different reactors configuration

In this work, the application of ozone-driven processes for the treatment of mature landfill leachate was investigated by testing different system setups. As a first approach, ozonation (O₃-only) was tested, using a porous ceramic diffuser combined with a bubble column (BC), and the best operational conditions were established for leachate treatment (initial pH = 9.0; inlet ozone dose = 18 mg O₃/min). Then, a novel photoreactor (FluHelik) was coupled in series with the bubble column, using a diffuser or a Venturi to inject ozone into the fluid stream. The FluHelik/BC-Venturi setup led to the highest efficiency, treating 50% more leachate than BC-alone using the same ozone dose and reaction time (3 h). Following, the oxidation ability of ozone combined with H₂O₂ and/or UVC for leachate treatment was assessed. The highest synergistic effect was obtained for the O₃/UVC process, with pseudo-first-order rate constant for DOC and COD removal, 2.0 and 1.4 times higher than for the O₃-only, respectively. Ozone-driven processes considerably enhanced the leachate biodegradability from 17% to 79% (O₃/H₂O₂), 81% (O₃-only), 85% (O₃/H₂O₂/UVC) and 91% (O₃/UVC), after a 3 h reaction period. With FluHelik/BC-Venturi system, the O₃/UVC process stands out as the most efficient and cost-effective (6.0 €/m³), ensuring an effluent that meets discharge legal limit for COD (150 mg/L) after further biological oxidation.

Analysis of the effect of the operational conditions in a combined adsorption–ozonation process with granular activated carbon for the treatment of phenol wastewater

Analysis of phenol ozonation using a G–L–S model: through mass transfer, chemical reaction and adsorption parameters.

Intensifying ozonation treatment of municipal secondary effluent using a combination of microbubbles and ultraviolet irradiation

Ozonation treatment of municipal secondary effluent is complicated by the low solubility of ozone and inefficient production of hydroxyl free radicals from ozone decomposition. To resolve these problems, this study investigated methods for intensifying ozonation treatment, using a combination of microbubbles and ultraviolet (UV) irradiation (UV/MBO). The high efficiency of the method was illustrated by treating river water containing refractory components derived from secondary effluent in a wastewater treatment plant. The results showed that the ozone mass transfer coefficient in a microbubble system was an order of magnitude compared with a conventional macrobubble system at the initial stage. The amount of ·OH generated during the treatment was quantified using a fluorescent probe analysis. The amount of ·OH in the UV/MBO system was almost 2-6 times more than the amount found with conventional ozonation using macrobubbles (CO), CO with UV irradiation (UV/CO), and microbubble ozonation (MBO) units. The UV/MBO system achieved chemical oxygen demand (COD), UV₂₅₄, and UV₄₀₀ removal performance rates of up to 37.50%, 81.15%, and 94.74% respectively. These levels were 2-36% higher than those in other systems. The coupling UV/MBO treatment significantly reduced all five categories of substances according to EEM spectra and fluorescence regional integration. The distribution of fractions with different molecular weights (MW) was altered and the UV₂₅₄ of MW (< 500 Da) increased by 15.8%. The biodegradability of the water was significantly improved, as indicated by the TOC/UV₂₅₄. This is ascribed to the enhanced degradation of refractory organics in the water. The combination of the UV/microbubble technique with ozonation could provide an efficient approach for advanced wastewater treatment. Graphical abstract.

Degradation of Thiol Collectors Using Ozone at a Low Dosage: Kinetics, Mineralization, Ozone Utilization, and Changes of Biodegradability and Water Quality Parameters

Ozonation at a high O3 dosage can achieve high efficiencies in removing flotation reagents but it has a low ozone-utilization rate. The ozonation of potentially toxic thiol collectors (potassium ethyl xanthate (EX), sodium diethyl dithiocarbamate (SN-9), O-isopropyl-N-ethyl thionocarbamate (Z-200) and dianilino dithiophoshoric acid (DDA)) was investigated in an ozone-bubbled reactor at a low O3 dosage of 1.125 mg/(min·L). The degradation kinetics, mineralization, ozone utilization, changes of biodegradability, and water quality parameters were studied, and the degradation behaviors of four collectors were compared. Thiol collectors could be effectively degraded with a removal ratio of >90% and a mineralization ratio of 10‒27%, at a low O3 dosage. The ozonation of thiol collectors followed the pseudo first-order kinetics, and rate constants had the order of kSN-9 > kEX > kZ-200 > kDDA. The Z-200 and DDA were the refractory flotation reagents treated in the ozonation process. After ozonation, the biodegradability of EX, SN-9, and DDA solutions was remarkably raised, but the biodegradability of Z-200 only increased from 0.088 to 0.15, indicating that the Z-200 and its intermediates were biologically persistent organics. After ozonation, the solution pH decreased from 10.0 to 8.0‒9.0, and both the conductivity and oxidation-reduction potential increased. The ozone utilization ratio in decomposing thiol collectors was above 98.41%, revealing almost complete usage of input O3. The results revealed that thiol collectors could be effectively degraded by O3, even at a low dosage, but their degradation behaviors were quite different, due to intrinsic molecular properties.

Impacts of ozonation on the competition between organic micro-pollutants and effluent organic matter in powdered activated carbon adsorption

This study investigates if ozonation of wastewater treatment plant (WWTP) effluent can reduce the negative impacts of effluent organic matter (EfOM) on the adsorption of organic micro-pollutants (OMP) onto powdered activated carbon (PAC). Pre-treatment of the water included membrane filtration for the removal of suspended/colloidal organics, ozonation with various specific ozone consumptions, and subsequent OMP spiking to comparable initial concentrations in all of the ozonated waters. This approach allowed for comparative PAC adsorption tests. Adsorption analyses show that the adsorbability of EfOM decreases with increasing specific ozone consumptions. This is also reflected by liquid chromatography with online carbon and UV254 detection (LC-OCD) which shows the ozone-induced disintegration of large EfOM into smaller fragments. Also, small organic neutrals are decreased while the small organic acids peak continuously increases with rising specific ozone consumptions. UV254 demonstrates that the aromaticity of all LC-OCD fractions continuously declines together with increasing specific O3 consumptions. This explains the varying EfOM adsorbabilities that occur due to ozonation. The ozone-induced decrease of EfOM adsorbability directly translates into reduced adsorption competition against the adsorption of OMP. With higher specific ozone consumptions, OMP removal and OMP loadings increase. The reduced adsorption competition is reflected in the outputs from equivalent background compound (EBC) modeling. In each of the ozonated waters, correlations between the OMP removals and the UV254 removal were found.

Inactivation of Escherichia coli in fresh water with advanced oxidation processes based on the combination of O3, H2O2, and TiO2. Kinetic modeling

The purpose of this work was to study the efficiency of different treatments, based on the combination of O3, H2O2, and TiO2, on fresh surface water samples fortified with wild strains of Escherichia coli. Moreover, an exhaustive assessment of the influence of the different agents involved in the treatment has been carried out by kinetic modeling of E. coli inactivation results. The treatments studied were (i) ozonation (O3), (ii) the peroxone system (O3/0.04 mM H2O2), (iii) catalytic ozonation (O3/1 g/L TiO2), and (iv) a combined treatment of O3/1 g/L TiO2/0.04 mM H2O2. It was observed that the peroxone system achieved the highest levels of inactivation of E. coli, around 6.80 log after 10 min of contact time. Catalytic ozonation also obtained high levels of inactivation in a short period of time, reaching 6.22 log in 10 min. Both treatments, the peroxone system (O3/H2O2) and catalytic ozonation (O3/TiO2), produced a higher inactivation rate of E. coli than ozonation (4.97 log after 10 min). While the combination of ozone with hydrogen peroxide or titanium dioxide thus produces an increase in the inactivation yield of E. coli regarding ozonation, the O3/TiO2/H2O2 combination did not enhance the inactivation results. The fitting of experimental values to the corresponding equations through non-linear regression techniques was carried out with Microsoft® Excel GInaFiT software. The inactivation results of E. coli did not respond to linear functions, and it was necessary to use mathematical models able to describe certain deviations in the bacterial inactivation processes. In this case, the inactivation results fit with mathematical models based on the hypothesis that the bacteria population is divided into two different subgroups with different degrees of resistance to treatments, for instance biphasic and biphasic with shoulder models. Graphical abstract ᅟ.

Degradation of DEET by ozonation in aqueous solution

This study was undertaken in order to understand the factors affecting the degradation of an insect repellent, N,N-diethyl-m-toluamide (DEET) by ozonation. Kinetic studies on DEET degradation were carried out under different operating conditions, such as varied ozone doses, pH values of solution, initial concentrations of DEET, and solution temperatures. The degradation of DEET by ozonation follows the pseudo-first-order kinetic model. The rate of DEET degradation increased exponentially with temperature in the range studied (20-50 degrees C) and in proportion with the dosage of ozone applied. The ozonation of DEET under different pH conditions in the presence of phosphate buffer occurred in two stages. During the first stage, the rate constant, k(obs), increased with increasing pH, whereas in the second stage, the rate constant, k(obs2), increased from pH 2.3 up to 9.9, however, it decreased when the pH value exceeded 9.9. In the case where buffers were not employed, the k(obs) were found to increase exponentially with pH from 2.5 to 9.2 and the ozonation was observed to occur in one stage. The rate of degradation decreased exponentially with the initial concentration of DEET. GC/MS analysis of the by-products from DEET degradation were identified to be N,N-diethyl-formamide, N,N-diethyl-4-methylpent-2-enamide, 4-methylhex-2-enedioic acid, N-ethyl-m-toluamide, N,N-diethyl-o-toluamide, N-acetyl-N-ethyl-m-toluamide, N-acetyl-N-ethyl-m-toluamide 2-(diethylamino)-1-m-tolylethanone and 2-(diethylcarbamoyl)-4-methylhex-2-enedioic acid. These by-products resulted from ozonation of the aliphatic chain as well as the aromatic ring of DEET during the degradation process.