Ozone Dose Research Articles

Ozone combined with mechanical agitation to enhance sludge cell lysis and provide an alternative carbon source for nitrogen removal of bioreactors

The activated sludge method results in the production of significant amounts of excess sludge. Moreover, biological nitrogen removal requires an external carbon source, which presents environmental and economic challenges. To address these challenges, this study combined ozone with mechanical agitation to achieve sludge cell lysis. Through both experiments and COMSOL Multiphysics simulations, optimal conditions were identified. These conditions include a six-bladed disk turbine stirrer speed of 800 rpm, an ozone concentration of 40 mg/L, and an ozone dose of 100 mg·g−1 MLSS (Mixed Liquid Suspended Solids). Notably, the sludge solubilization efficiency improved by 20.1 % when compared to using ozone alone. After the sludge dissolution, this paper observed elevated concentrations of soluble chemical oxygen demand (SCOD), total nitrogen (TN) and total phosphorus (TP) in the supernatant, reaching 3126 mg/L, 144.3 mg/L, and 49.6 mg/L, respectively. This study also investigated the feasibility of using this supernatant as an external carbon source in a sequencing batch reactor. The results showed that while the supernatant had minimal impact on COD removal, it significantly enhanced nitrogen removal. Compared to using glucose as an external carbon source, the TN removal rate increased by 16.9 %. However, TP removal was inhibited.

The Role of Ozonation as an Advanced Oxidation Process for Attenuation of 1,4-Dioxane in Potable Reuse Applications

ABSTRACT The combination of ozone and hydrogen peroxide (O3/H2O2), or the peroxone process, has often been used as an advanced oxidation process (AOP) in groundwater remediation and drinking water applications. This historical precedent sometimes leads to the misconception that H2O2 addition is required to achieve AOP conditions during ozonation. This is not the case for secondary or tertiary wastewater effluent applications, in which ozone reacts with abundant dissolved organic carbon (DOC) to generate hydroxyl radicals (∙OH). This study demonstrates the use of ozone with and without H2O2 addition to yield ∙OH exposures (up to 10−9 M-s) capable of achieving > 0.5-log10 attenuation of the industrial contaminant and probable human carcinogen 1,4-dioxane. This low molecular weight compound is commonly used as a surrogate when establishing AOP design criteria for potable reuse applications. DOC-normalized ozone doses (i.e., O3/DOC ratios) of ~ 1.0 and ~ 1.3 achieved 0.5-log10 attenuation of 1,4-dioxane with O3/H2O2 and O3, respectively. Also, a predictive model based on ∙OH exposure was accurate within approximately ± 10%. These results suggest that ozonation’s role as an AOP, even in the absence of H2O2, should be acknowledged in regulatory frameworks to reduce unnecessary treatment redundancy and facilitate broader implementation of potable reuse.

Food Industrial Effluent Treatment with Oxygen and Ozone Using Activated Carbon for Catalytic Oxidation

ABSTRACT A catalytic oxidation treatment to remove coloration and chemical oxygen demand (COD) in an effluent from a food industry was carried out using oxygen and ozone as oxidizing agents and activated carbon as a catalytic. Different experiments of oxidation were conducted using 25, 50 and 100 mL of activated carbon bed to treat 100 mL of sample and constant flow of oxygen 7.2 g/min and ozone 0.034 mg/min, maintaining initial pH of industrial effluent. Almost a complete coloration removal and COD reduction of the sample was achieved for catalytic processes; however, time of treatment and agent oxidant doses were different in each case. According to volume of activated carbon beds, ozone doses for discoloration and COD removal were 8.5, 2 and 1.7 mg/L, whereas the oxygen doses were 2860, 770 and 500 g/L, respectively. Consequently, to eliminate the color in the industrial effluent, the dose of oxygen was higher than that of ozone. In addition, the oxidation agents promoted the regeneration of activated carbon, showing that its activity is declined after 60 cycles of effluent treatment with ozone, whereas with oxygen treatment, the total depletion was observed in 18 cycles. In turn, single adsorption showed activated carbon depletion in 5 cycles of effluent treatment.

Degradation of chromosomal and plasmid encoded extracellular and intracellular resistance genes across different types and sizes in water matrices during ozone-based oxidation process

Antimicrobial resistance is a major and growing threat to public health and imposes significant environmental and economic burden worldwide. This study evaluates the degradation kinetics of resistance genes from ciprofloxacin (gyrAR), levofloxacin (qnrSR), tetracycline (tetAR), and mobile genetic elements (intl-1, plasmids) in water matrices by O3 treatment. For extracellular antibiotic resistance genes (e-ARGs) in deionized water, 3.6–5.2 logs removal was obtained, whereas intracellular ARGs (i-ARGs) in phosphate buffer saline, exhibited a removal of 3.5–4.5 logs at an O3 dosage of 3.7 × 10−2 M.s. While there was no significant impact of the wastewater matrix on e-gyrAR and e-intl-1 degradation as compared to deionized water (p > 0.05), the e-qnrSR reduction was higher (4.8–5.2 logs) at an ozone dosage of 3.7 × 10−2 M.s. For i-plasmid and e-plasmid encoded ARGs in wastewater, 4.0–5.5 logs removal was observed for the same dosage. Electrical Energy per Order (EEO, kWh/m3) was estimated, and the energy consumption on the degradation of the ARGs in the wastewater ranged between 0.68 and 1.1 kWh/m3. The findings of this study provide quantitative data for evaluating the fate and degradation of different ARG forms/types during ozone treatment of wastewater to mitigate the risk of AMR dissemination in the environment.

Cleaning efficiency and mechanism of ozone micro-nano-bubbles on ceramic membrane fouling

Membrane separation technology using ceramic membrane as carrier has attracted wide attention in drinking water treatment. However, the inevitable problem of irreversible contamination requires high intensity chemical cleaning in place (CIP) to ensure efficient ultrafiltration performance. Therefore, this study discussed the causes of membrane pollution, and further evaluated the purification effects of sodium hypochlorite, different aeration methods and different dosage of ozone as cleaning agents on membrane pollution. Comparison of the physicochemical properties and surface morphology of ceramic membranes before and after cleaning showed that ozone micro-nano-bubbles (O3-MNBs) had excellent cleaning efficiency at the same dosage. MNBs could provide shear forces, while their high mass transfer efficiency increased the dissolved ozone concentration rapidly. The degradation of fouling on the membrane surface was achieved by direct ozone oxidation and indirect oxidation by the generation of OH, resulting in a 100% flux recovery rate in a short time. Our results suggest that O3-MNBs, as a promising CIP method for ceramic membranes, not only significantly improves cleaning efficiency, but also reduces the negative environmental impact of chemical agents.

The Role of Ozone as an Nrf2-Keap1-ARE Activator in the Anti-Microbial Activity and Immunity Modulation of Infected Wounds.

Ozone is an allotrope of oxygen, widely known to exert an anti-oxidant potential. The ability of low, controlled and standardized doses of ozone in the ozone adjunct treatment of bacterial infections, which occur in wounds, is engaging clinical research to deepen the role of ozone in eradicating even multidrug-resistant bacteria. Ozone activates the nuclear factor erythroid 2-related factor 2 (Nrf2), and this activation triggers a complex cascade of events, which ultimately leads to macrophage training and an improvement in their ability to operate a clearance of bacteria in the patient's anatomical districts. In this review, we try to elucidate the recent evidence about the mechanisms with which ozone can actually remove bacteria and even multi-drug-resistant (MDR) bacteria, accounting on its complex ability in modulating immunity.

Regulating ferroelectricity in Hf0.5Zr0.5O2 thin films: Exploring the combined impact of oxygen vacancy and electrode stresses

Hf0.5Zr0.5O2 (HZO) is a promising candidate for low-power non-volatile memory due to its nanoscale ferroelectricity and compatibility with silicon-based technologies. Stress and oxygen vacancy (VO) are key factors that impact the ferroelectricity of HZO. However, their combined effects have not been extensively studied. In this study, we investigated the impact of the VO content on HZO thin films’ ferroelectricity under different electrode stresses by using TiN and tungsten (W) top electrodes and controlling ozone dose time during HZO deposition. The HZO thin films with W top electrodes exhibit elevated stress levels and a greater abundance of orthorhombic/tetragonal phases, and the HZO thin films with TiN top electrode shows an increase in the monoclinic phase with increasing ozone dose time. The residual polarization (Pr) of the capacitors with TiN and W top electrodes displayed different or even opposing trends with increasing ozone dose time, and the VO content decreases with increasing ozone dose time for both sets of capacitor samples. We propose a model to explain these observations, considering the combined influence of electrode stresses and VO on the free and formation energy of the crystalline phase. Increasing the VO content promotes the transformation of the tetragonal phase to the orthorhombic phase in HZO films with TiN top electrodes, and with W top electrodes, a higher VO content prevents the tetragonal phase from transforming into the orthorhombic/monoclinic phase. Additionally, an alternative explanation is proposed solely from the perspective of stress. These findings provide valuable insights into the regulation of ferroelectricity in HZO thin films.

Tertiary/quaternary treatment of urban wastewater by UV/H2O2 or ozonation: Microplastics may affect removal of E. coli and contaminants of emerging concern

The aim of this study was to investigate the interference of polyethylene microplastics (MPs) on ultraviolet irradiation/hydrogen peroxide (UV/H2O2) and ozonation processes in the inactivation of E. coli bacteria (tertiary treatment) and removal of contaminants of emerging concern (CECs) (quaternary treatment) from simulated and real secondary treated urban wastewater. Three pharmaceuticals were investigated as model CECs, namely carbamazepine, sulfamethoxazole and trimethoprim. Experimental results showed that disinfection efficiency of UV/H2O2 treatment decreased (2.4, 1.8 and 1.3 log reductions of E. coli, initial H2O2 dose of 30 mg/L, 2.5 min treatment) as the initial concentration of MPs was increased (0.25, 0.5 and 1.0 g/L, respectively). Similarly, an increase in MPs concentration (0.25, 0.5 and 1.0 g/L) reduced the inactivation (4.7, 4.1 and 3.7 log reductions) of the target bacteria after 60 min of ozonation treatment. Although the disinfection efficiency of both treatment processes was negatively affected by the presence of MPs, UV/H2O2 was more effective than the ozonation, despite ozonation being investigated at high doses to better discriminate the effect of MPs. Noteworthy, CECs degradation by UV/H2O2 under realistic operating conditions was affected to some extent by MPs, while a lower effect was observed for ozonation, at not realistic ozone dose.

Process design for removal of pharmaceuticals in wastewater treatment plants based on predicted no effect concentration (PNEC)

Increasing concern on water contamination by micropollutants like pharmaceuticals fuels the development and implementation of technologies to remove micropollutants from municipal wastewater treatment plants (WWTP). However, often the targets and criteria for process design of such technologies are not clarified. This study was conducted to test whether predicted no-effect concentrations (PNEC) can be used as a design parameter for advanced treatment technologies to achieve pharmaceutical levels in WWTP effluents. This goal is consistent with environmental requirements, currently being discussed both by the Danish authorities and the European goals on zero emissions as documented in the draft of the Urban Wastewater Directive. The effluent of a conventional activated sludge WWTP was treated by ozonation and granular activated carbon (GAC) and monitored for 50 pharmaceuticals and iodinated X-ray contrast media, as well as 23 transformation products. Treatment with GAC alone initially achieved concentrations below PNEC for all targeted compounds, but after treating 3,000 – 5,000 bed volumes, the removal for several compounds decreased and the effluent concentrations for clarithromycin and venlafaxine were no longer below PNEC. Ozonation alone effectively reduced the concentrations of most of the compounds with standard ozone dosing of 0.5 mg O3/mg DOC. However, ozonation was unable to remove bicalutamide and oxazepam to reach target concentrations. The operation of both technologies in combination achieved concentrations of all measured pharmaceuticals below the PNEC (even with ozone concentrations of below 0.5 mg O3/mg DOC). Nonetheless, this study suggests that proper steering of WWTP design via the PNEC values alone is obstructed by lack of reliable primal PNEC data and absence of PNEC references for emerging pollutants and potential biologically active transformation products.

The Effect of Ozone Dosage of Sunflower and Olive Oils on Their Biological Activities and Chemical Properties

ABSTRACT The ozonation process of vegetable oils is commonly monitored by peroxide value (PV). However, PV methodology has been adapted from vegetable oils, with protocol divergences. In addition, few studies are based on the minimum level of ozonation to ensure biological activity. This study aimed to optimize the PV methodology for sunflower oil with different ozone dosage aiming to discriminate these samples. Also, to establish the relationship between its physicochemical properties with the biological activity. The optimized PV method was also applied to ozonated olive oil, as well as the other analytical techniques of iodine value (IV), acidity value (AV), density, viscosity, gas chromatography, infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), differential scanning calorimetry and thermogravimetry (DSC and TG). The PV method discriminated the ozonation level of the samples. Both ozonated sunflower and olive oils need to reach an intermediary ozone dosage to perform the in vitro bactericidal and fungicidal activity (MIC ≤2.5%), and anti-inflammatory activity (inhibition of nitric oxide release in Raw cells). These results point to the importance of standardizing the ozone dosage for each oil and the analytical methodologies used in its characterization.

Magnetically recoverable copper ferrite for catalytic ozonation of surfactant-containing simulated laundry wastewater

Laundry detergent wastewater is a valuable renewable resource released in vast quantities that can be reused to alleviate water shortage issues. The primary contaminant found in laundry wastewater, which is the surfactant has harmful impacts on the ecosystem, resulting in the eutrophication of lakes and rivers. This study examines the effectiveness of catalytic ozonation treatment using a magnetically recoverable copper ferrite to treat surfactant-containing laundry wastewater. A magnetically recoverable copper ferrite was successfully prepared using a modified sol-gel method for the remediation of detergent wastewater. The modified sol-gel method uses a low calcination temperature (350 °C) synthesis process to prepare spinel-structured copper ferrite. The physicochemical properties of the prepared copper ferrite were evaluated using XRD, FT-IR, XPS, FESEM, BET, and VSM analyses. Various process parameters such as initial concentration, solution pH, catalyst dosage, and ozone dosage were investigated to reveal the ozone activation capability and catalytic mechanism. The surfactant degradation performance in catalytic ozonation was compared with the non-catalytic ozonation, respectively. Results indicated that the copper ferrite exhibited excellent ozone activation ability, with 98.4% of surfactant degradation at an initial concentration of 10 ppm, a reaction time of 30 min, a catalyst dosage of 0.2 g/L, an initial pH of 7 and an ozone dosage of 3.68 mg/min. The chemical oxygen demand (COD) elimination rate at this setting was 79.5% compared to 26.7% for non-catalytic ozonation. The biochemical oxygen demand (BOD) removal percentages for ozonation and catalytic ozonation were 33.3% and 93.3%, respectively. Simple economical assessment using electrical energy per order (EE/O) showed that low electrical energy was consumed by the catalytic ozonation (60.31 kWhm−3order−1) compared to the ozonation process (381.68 kWhm−3order−1). The copper ferrite can be quickly recovered from the treated water by applying an external magnet, enabling catalyst reuse and easy collection of treated water. Several limitations restrict its application, including metal leaching and catalyst agglomeration. This is the first application of copper ferrite-catalysed ozonation for the remediation of laundry effluent-containing surfactants. These findings showed a vast application potential of catalytic ozonation using copper ferrite for surfactant-containing laundry wastewater treatment.

Catalytic ozonation of a petrochemical wastewater containing high concentration of dinitrotoluene

Catalytic ozonation of a real industrial wastewater containing recalcitrant nitroaromatic compounds was investigated by different catalysts, and removal of color and COD was tracked over time. The effects of operational parameters such as catalyst type (MnO2, Nano-MnO2, ZnO, SnO2, Fe3O4, nZVI, and diatomite earth), initial pH, ozone dosage, and catalyst dosage on the removal efficiency were studied. Experimental results showed that MnO2 performed significantly better than other catalysts, with Nano-MnO2 resulting in over 80% COD removal, from 21750 to 3915 mg/L. Conventional MnO2 catalyst, on the other hand, resulted in only 66% COD removal. Besides, biodegradability of the recalcitrant initial wastewater improved from 0.29 to 0.88 after 3 h of ozonation. Color removal efficiency was nearly complete (>99%) for both conventional and Nano-MnO2. An analysis of complete degradation using GC–MS indicated that 2,4-DNT and other organics were completely removed; whereas, 2,6-DNT was partially degraded.

Microcystin-LR Removal by Ozone (O3) and Vacuum-UV (VUV): The Effect of Chloride Ions

ABSTRACT Removal of microcystin-LR (MC-LR) by ozone (O3), vacuum-UV (VUV), and their combination was investigated in the presence of chloride as one of the main solutes present in water. In general, the combined VUV/O3 process provided the greatest MC-LR removal, with the presence of chloride enhancing the removal efficacy. Formation of chlorine radical species was the primary reason for the observed improvement. The order of MC-LR removal by different processes using UV fluence of around 300 mJ cm−2, ozone dose of 0.1 mg L−1, and chloride concentration of 120 mg L−1 was as follows: VUV/O3/Chloride > VUV/O3 > VUV/Chloride > VUV > O3. Comparing MC-LR removal by O3, VUV and VUV/O3 in synthetic lab samples, spiked with Suwannee River NOM and natural water samples of the same organic concentration, showed the significance of background organics in scavenging ozone in the process. For a given ozone dosage, MC-LR removal by O3 or VUV/O3 in natural water was lower than that in the synthetic water samples. The standalone VUV was not affected and the MC-LR removals were identical in both synthetic and natural waters.

Is the increased ozone dosage key factor for its anti-inflammatory effect in an experimental model of mesenteric ischemia?

Ischemia/reperfusion injury of the intestines is a severe surgical condition. This study aimed to reveal ozone therapy effects with relatively increased ozone dosage in a created ischemia/reperfusion injury model. In this study, 24 albino Wistar rats were examined in three groups. Rats in the control group (CG, n=8) underwent only a laparotomy. In the sham group (SG, n=8) and ozone group (OG, n=8), the superior mesenteric artery (SMA) of the rats was occluded for 1 h. After de-occluding the SMA, the abdomen was closed, physiological saline was infused intraperitoneally in the SG, and an increased ozone/oxygen mixture dose (from 0.7 mg/kg to 1 mg/kg) was infused intraperitoneally in the OG. Small intestine samples were obtained at the 24th h for histopathological examination of intestinal mucosal injury and evaluated according to the Chiu score. In addition, Malondialdehyde and Myeloperoxidase levels were evaluated for oxidant levels, whereas, Glutathione (GSH) enzyme activity was measured to evaluate the tissue antioxidant system. Histopathologically, the Chiu score was the lowest in the CG. It was lower in the OG compared to the SG showing the ameliorating effect of ozone on the intestinal mucosa. Chiu score in the OG was higher compared to that in the CG, but not statisti-cally significant. A significantly higher GSH level was observed in the OG compared to the SG, proving antioxidant activity. In this experimental model of ischemia/reperfusion in rats, treatment with an increased ozone level decreased the inflammatory process through antioxidant mechanisms and reduced intestinal mucosal damage. However, the effectiveness of ozone therapy depends on its dosages.

Ecotoxicological mixture risk assessment of 35 pharmaceuticals in wastewater effluents following post-treatment with ozone and/or granulated activated carbon

Reducing the risk posed by mixtures of pharmaceuticals is a goal of current initiatives such as the European Green Deal to reduce anthropological environmental impacts. Wastewater effluent typically contains large numbers of active pharmaceutical ingredients (APIs). For some APIs, existing technology such as conventional activated sludge (CAS) wastewater treatment plants (WWTPs) have removal rates below 20 %, thus the WWTP discharges are adding to the toxic burden of receiving waters.We present an environmental risk assessment of mixtures of 35 APIs in effluent samples from 82 Northern European WWTPs using the concentration addition model, and identify the respective risk-driving APIs. This is then compared to a corresponding mixture risk assessment of effluent samples from the Danish Hillerød WWTP subjected to post-treatment with varying specific ozone doses (0.15–1.05 mgO3/mgDOC) and/or granulated activated carbon (GAC).All 82 WWTP effluent samples exceeded risk thresholds by at least a factor of 30, with a median RQSUM of 92.9, highlighting the need for effluent post-treatment and/or a substantial dilution in the recipient waters. Antibiotics, analgesics and anti-depressants were among the top risk drivers with 99 % of the average mixture risk attributable to azithromycin, diclofenac, venlafaxine, clarithromycin and mycophenolic acid. Effluent mixture risk was reduced by ozonation in a concentration-dependent manner, decreasing below threshold levels to a median RQSUM of 0.83 following treatment with 0.65 mgO3/mg DOC. Fresh GAC was also effective at reducing the mixture risk both alone and with ozone treatment, with median RQSUM of 0.04 and 0.07 respectively.To our knowledge, this is the first study to present a risk assessment of pharmaceutical mixtures in effluent comparing “conventional” WWTP processes with additional post-treatment with ozone and/or GAC for reducing the joint risks of pharmaceutical mixtures for recipient waters. We demonstrate the need for additional WWTP treatment technologies, and the efficacy of GAC and ozonation in decreasing the risk to the aquatic environment from pharmaceutical mixtures to below acceptable threshold limits.

Treatment of Textile Wastewater by a Novel Clay/TiO2/ZnO-Based Catalyst, Applying a Synergic Catalytic Ozonation–Electroflocculation Process

This study aims to investigate the treatment of real textile wastewater using a novel bentonite clay/TiO2/ZnO-based ozonation catalyst. In this study, synergic electroflocculation/catalytic ozonation, catalytic ozonation, and ozonation processes are applied in a modified hybrid reactor. To the authors’ knowledge, this is the first application of bentonite clay/TiO2/ZnO as an ozonation catalyst for treating real textile wastewater. The four operational variables—ozone dose (0.2–0.8 mg/min), reaction time (0–120 min), DC voltage supply (5–15 V), and catalyst dose (0.5–2 g/L)—were studied for decolorization and for the removal of chemical oxygen demand (COD). The results showed that the combined process (electroflocculation + clay/TiO2/ZnO/O3) had the highest removal efficiencies for COD and color (97.86% and 97.90%, respectively) at optimum parameters of 10 DC volts. an ozone dose of 0.8 mg/min, and a catalyst dose of 2 g/L in textile wastewater. The results further revealed that the initial pH of wastewater plays an essential role in the process’s overall performance. The studied synergic process was efficient for real wastewater treatment under alkaline pH (6–9). Based on empirical work, we established that the synergic process is suitable for effectively treating textile wastewater.

Techno-economic assessment of coupling ozonation and biodegradation process for the dye wastewater treatment

The biological processes have been outlined as an economical and sustainable technique for the treatment of a variety of organic pollutants. However, these processes are limited when wastewater contained recalcitrant pollutants which cause a lower biodegradability index (BOD5: COD <0.2). The present study made an effort to develop a coupled system to enhance the performance of the biological processes, and subsequently treat the low biodegradability index wastewater. The performance and feasibility of the integrated system were studied for the complete mineralization of Congo red dye from wastewater. The ozonation was carried out for 25 min with an ozone dose of 69.97 mg/L to enhance the BOD5/CODratio from 0.114 to 0.44, to make the sample suitable for biological treatment. The ozonated sample was further mineralized by biodegradation. Identification of intermediate metabolites was carried out by GC–MS analysis and the end product matches closely with fragments such as 2-Amino-1-propanol (m/z = 75) and Oxaluric acid (m/z = 132). Techno–economic assessment showed that the coupling of ozonation with biodegradation could save 34 % unitary expense in comparison to a single ozonation process.

Elucidating the relation between residual oxidants formation behavior and quinolone antibiotic removal efficiency on catalytic ozonation in seawater-based aquaculture wastewater

Owing to the recent developments in aquaculture, the discharge of antibiotic-laden wastewater has become a growing concern. Quinolone antibiotics, which cause central nervous system and cardiac conduction disorders, are commonly detected in aquaculture wastewater. To remove antibiotics in wastewater, the ozone process is a commonly utilized method. In the process of seawater ozone treatment, bromide ions (Br−) produce total residual oxidant, such as hypobromous acid (HOBr). However, the oxidation potential of the total residual oxidant (TRO) is lower than that of ozone, and the presence of inhibitors, such as ammonium, and dimethyl sulfide can reduce the residual oxidant concentration. Therefore, the seawater ozone process requires a higher ozone injection than freshwater. In this study, various factors affecting TRO production were evaluated to determine the optimal ozone-catalytic process using gamma-alumina and elucidate the relationship between TRO production and antibiotic removal efficiency for efficient seawater-based wastewater treatment. The removal rates of representative quinolone antibiotics, such as enrofloxacin, ciprofloxacin, and oxolinic acid, were evaluated using liquid chromatography-fluorescence detection. The addition of a catalyst enabled the reaction to maintain a higher TRO concentration and improves antibiotic removal efficiency, even in the presence of ammonium in the aquaculture wastewater with the same ozone dosage applied. The results reveal that the ozone-catalyst process contributes to increased TRO production to suppress bacterial growth and effectively remove non-degradable organic matter, such as antibiotics, in seawater-based wastewater treatment.

Significance of ozonation on surfactant-polymer flooding produced water coagulation: Water quality deterioration inhibition, high-standard reinjection and mechanism

Surfactants and polymers are extensively being used to enhance oil recovery resulting in the generation of surfactant-polymer (SP) flooding produced water, which is more challenging to treat for reinjection compared with conventional produced water. Aiming at high-standard SP flooding produced water reinjection, this study investigated the coagulation-based treatment processes for the treatment of SP flooding produced water. The conventional coagulation process with two typical coagulants, poly-aluminum chloride (PAC) and poly-ferric sulfate (PFS), was applied. However, the effluent did not meet the reinjection requirements for suspended solids (SS) ≤ 2 mg/L, oil ≤ 6 mg/L and median diameter d50 ≤ 1.5 μm according to the water quality standard for oilfield injecting waters in clastic reservoirs (SY/T 5329–2012). The presence of adsorbed surfactant (betaine) and polymer (hydrolyzed polyacrylamide, HPAM) on oil and suspended solids increased the difficulties in agglomeration and charge-neutralization. In addition, water quality deterioration occurred within 5 h leading to increased turbidity, suspended solids and d50. X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis implied that water quality deterioration was caused by souring (producing sulfide), leading to the generation of suspended solids mainly containing sulfur and calcium carbonate (CaCO3). To address these challenges, the pre-ozonation coagulation (POC) and hybrid ozonation-coagulation (HOC) processes were compared. The effluent from both processes, using either PAC or PFS, met the reinjection requirements while inhibiting water quality deterioration. Additionally, higher removal efficiency and significantly reduced optimal ozone dosage were also achieved in the HOC process compared with the POC process. The enhanced generation of hydroxyl radicals (•OH) and polymeric hydrolysed coagulant species in the HOC process contributed to higher removal efficiency of HPAM, betaine and COD. Kinetics analysis revealed that •OH oxidation and coagulation played important roles in betaine and HPAM removal, respectively. The reaction pathways of betaine and HPAM in the ozonation and HOC processes were also analysed. Furthermore, the HOC process can effectively inhibit the accumulation of small molecular weight organic matter, facilitating the simultaneous coagulation.

Impact of ozonation on disinfection byproducts formation from phenylalanine during chlorination

As a strong oxidizing agent, ozone is used in some water treatment facilities for disinfection, taste and odor control, and removal of organic micropollutants. Phenylalanine (Phe) was used as the target amino acid to comprehensively investigate variability of disinfection byproducts (DBPs) formation during chlorine disinfection and residual chlorine conditions subsequent to ozonation. The results showed that subsequent to ozonation, the typical regulated and unregulated DBPs formation potential (DBPsFP), including trichloromethane (TCM), dichloroacetonitrile (DCAN), chloral hydrate (CH), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and trichloroacetamide (TCAcAm) increased substantially, by 2.4, 3.3, 5.6, 1.2, 2.5, and 6.0 times, respectively, compared with only chlorination. Ozonation also significantly increased the DBPs yield under a 2 day simulated residual chlorine condition that mimicked the water distribution system. DBPs formations followed pseudo first order kinetics. The formation rates of DBPs in the first 6 hr were higher for TCM (0.214 hr−1), DCAN (0.244 hr−1), CH (0.105 hr−1), TCAcAm (0.234 hr−1), DCAA (0.375 hr−1) and TCAA (0.190 hr−1) than thereafter. The peak DBPsFP of TCM, DCAN, CH, TCAcAm, DCAA, and TCAA were obtained when that ozonation time was set at 5–15 min. Ozonation times > 30 min increased the mineralization of Phe and decreased the formation of DBPs upon chlorination. Increasing bromine ion (Br−) concentration increased production of bromine- DBPs and decreased chlorine-DBPs formation by 59.3%–92.2% . Higher ozone dosages and slight alkaline favored to reduce DBP formation and cytotoxicity. The ozonation conditions should be optimized for all application purposes including DBPs reduction.