Effect Of Ozone Dosage Research Articles

Pre-ozonation for gravity-driven membrane filtration: Effects of ozone dosage and application timing on membrane flux and water quality

Gravity-driven membrane (GDM) filtration has been proposed as an alternative to sand filtration for drinking water treatment, but its low membrane flux and poor permeate quality hinder its widespread application. This study investigated the effect of pre-ozonation (with various dosages and application timings) on membrane flux, fouling layer characteristics, and permeate quality during GDM filtration of river water. Pre-ozonation with 3 mg/L ozone increased the mean membrane flux by 9–54%, resulting in approximately 30% increased water production and reduced dissolved organic carbon (DOC) and extracellular polymeric substance (EPS) production by 12–35% and 9–18%, respectively. The timing of pre-ozonation significantly affected the time-dependent flux behavior and morphological characteristics of the fouling layers. Pre-ozonation from the beginning of GDM filtration enhanced the initial flux because of organic fouling control but showed a gradual flux decline with time due to EPS accumulation and biologically inactive fouling layers. Pre-ozonation from the middle of GDM filtration period created heterogeneous and porous membrane fouling layers with high biological activity, showing increased membrane fluxes and improved permeate quality by removing DOC and assimilable organic carbon (AOC) via the combined action of ozone oxidation and biodegradation/sorption in the fouling layer. Overall, our results demonstrate pre-ozonation as a potential option to overcome the limitations of GDM filtration.

Degradation of dibutyl phthalate by ozonation in the ultrasonic cavitation-rotational flow interaction coupled-field: performance and mechanism.

Dibutyl phthalate (DBP) is present in hydraulic fracturing flowback and produced water. Degradation of DBP in aqueous by means of ozonation in ultrasonic cavitation-rotational flow interaction coupled-field (UC-RF coupled-field) was studied. The effect of ozone dosage, ozone intake flow, operating temperature, initial pH, DBP initial concentration, liquid flow rate, and ultrasonic power on the DBP removal was investigated. Results indicated that the DBP degradation rate was strongly influenced by the liquid flow rate and the ultrasonic power over the range investigated. HCO3- and Cl- revealed an inhibitory effect on the DBP removal. SO42- seemed to have no effect on DBP removal. The ozone utilization efficiencies in the UC-RF coupled-field were 2.77 and 1.13 times higher than those in the conventional microporous aeration (CMA) and rotating-flow microbubble aeration (RFMA), respectively. The DBP degradation rate was diminished in the presence of tert-butyl alcohol. Cavitation bubbles are considered as innumerable microreactors. Degradation of DBP by direct ozonation, hydroxyl radical (·OH) oxidation, high pressure, and high-temperature pyrolysis was demonstrated. Finally, a possible degradation pathway of DBP is obtained on the basis of the main reaction intermediates.

Effect of Ozone Dosage on Sludge Settleability and Biological Nutrient Removal in SBR System

The effect of ozone dosage on sludge settleability and biological nutrient removal performance in a sequencing batch reactor was investigated by inoculating the bulking sludge with the SVI of 280 mL·g-1 from a wastewater treatment plant in winter. The filamentous mycelium was interrupted, and the SVI was decreased to 125 mL·g-1 after ozone dosage with a low concentration of 0.085 g·g-1(O3/MLSS) for 20 days, which indicated the disappearance of the sludge bulking. The performance of nitrification and phosphorus removal efficiency was not affected obviously. However, the sludge settleability deteriorated with a high dosage of ozone, and the phosphorus removal efficiency was decreased to around 60%. Further study showed that PS/PN had a positive correlation with SVI with the correlation coefficient of 0.9381, which can be used to characterize sludge settleability. A low ozone dosage not only interrupted the filamentous mycelium, but it also affected the content and composition of the EPS, which led to improved settleability.

Application of Advanced Oxidation Process Using Ozonation Assisted with Hydrogen Peroxide for Organic Compounds Removal from Bayer Liquor

ABSTRACT One of the alumina industry’s main problems is the organic matter in the Bayer liquor during the Bayer Process released in the bauxite digestion process and accumulating in the process. It reduces as process efficiency and results in impurities in the final product. Several studies have shown that removing organic matter by ozonation can be attractive for industrial applications since ozone can be generated in situ and achieve faster results. For this reason, the goal of the present work was to study the removal of organic matter from the Bayer liquor. The effect of ozone dosage and O3/H2O2 combination was evaluated at 40 °C and 80 °C. Results indicated that the organic matter mineralization achieved 19% at 80 °C, using 6.5 g/L of O3 and 0.05 mol/L of H2O2, where 95.4% generated carbon dioxide. At the same conditions, 45.6% of oxalate was degraded. The UV/vis analyses demonstrated the decrease in organic chain size and the color of the samples before and after the oxidation process. An advanced oxidation process (O3 and O3/H2O2 combination) effectively removed a range of organic impurities from the Bayer liquor impacting the quality of the final product.

Advanced Treatment of Dry-Spun Acrylic Fiber Wastewater by O3/UV-BAF Process

The dry-spun acrylic fiber wastewater is characterized by its complicated components and high volatility of water quality. Therefore, it is typically difficult to treat. In this paper, the advanced treatment of dry acrylic plant effluent was treated by the joint process of ozone/ultraviolet-biological aerated filter (O3/UV-BAF). The effects of ozone dosage and pH on ozone to degrade COD were discussed, and under the condition of the process running steadily, the removal effect of each unit on COD was investigated. The results showed that with the increase of ozone dosage, the increase of COD removal was generally shown as a slow first, then a fast and then a steady trend. In the ozone dosage from 52.6 to 63.2 mgL-1, the COD removal rate reached 32.7% to 35.3%, and had the best economic feasibility. At pH 9 or so, the COD removal was the highest. The average removal of O3/UV for COD was 32.0%, the average removal of BAF for COD was 32.6%, and the average COD concentration of effluent was 83.4 mgL-1, met its first class discharge standard.

Trichloronitromethane formation from amino acids by preozonation-chlorination: The effects of ozone dosage, reaction time, pH, and nitrite

The formation potentials of trichloronitromethane (TCNMFPs) of four natural amino acids (glycine, threonine, lysine and tryptophane) were investigated during chlorination and preozonation-chlorination. The effects of initial ozone dosage, reaction time, pH, and nitrite concentration on the TCNMFP of selected amino acid (AA) solutions were carried out in detail. During preozonation-chlorination, TCNMFPs of glycine- and lysine-containing solutions were more significant than that containing the other two AAs. Increasing the initial ozone concentration resulted in a considerable increase of TCNMFPs from glycine, lysine, and tryptophane. The concentration of trichloronitromethane (TCNM) of glycine, threonine, and lysine solutions increased during preozonation-chlorination with the ozonation time extended. The effect of pH on TCNMFPs of amino acid by preozonation was compound-specific. In addition, the presence of nitrite ions contributes greatly to TCNMFP for all four types of amino acids. However, as the concentration of NO2− increased to higher levels, there was no significant further enhancement of TCNMFP. For chlorination alone, TCNM formed in all four amino acid solutions, with tryptophane solution having the highest TCNMFP.

The recent development of advanced wastewater treatment by ozone and biological aerated filter.

The combination of ozone and biological aerated filter (O3/BAF) has been widely studied and applied in polishing different biological secondary effluents. O3/BAF has the advantages of high pollutants removal rate, low operating cost, and flexible combination types. The principle and combination, effect of ozone dosage and influent suspended solids (SS) on O3/BAF, applications, current research focuses, and development are discussed. The ozone can break refractory macromolecules into small and biodegradable fragments, increasing the biodegradation. It benefits the operation of BAF. The coupling of ozonation and BAF is efficient in the removal of refractory organic pollutants from different wastewaters. Ozonation can also be used as the post-treatment option after BAF to guarantee the effluent qualities. Normally, the ozone dosage varied from 5 to 125mg/L with the contact time of 4 to 60min, while the hydraulic retention time (HRT) of BAF is usually between 2 to 5h when treating different biological effluents. The effluent COD is normally lower than 50mg/L. Most of the organic micropollutants (OMPs) in the biological effluent, such as antibiotics, pharmaceuticals, personal care products, steroid hormones, and industrial chemicals, can be efficiently removed by O3/BAF. More importantly, the O3/BAF can obviously reduce the toxicity of the wastewater. The residual ozone of about 0.2mg/L in the ozonation effluent benefits the performance of BAF. The future trends of O3/BAF are also discussed in the paper.

Iron doped fibrous-structured silica nanospheres as efficient catalyst for catalytic ozonation of sulfamethazine.

Sulfonamide antibiotics are ubiquitous pollutants in aquatic environments due to their large production and extensive application. In this paper, the iron doped fibrous-structured silica (KCC-1) nanospheres (Fe-KCC-1) was prepared, characterized, and applied as a catalyst for catalytic ozonation of sulfamethazine (SMT). The effects of ozone dosage, catalyst dosage, and initial concentration of SMT were examined. The experimental results showed that Fe-KCC-1 had large surface area (464.56m2g-1) and iron particles were well dispersed on the catalyst. The catalyst had high catalytic performance especially for the mineralization of SMT, with mineralization ratio of about 40% in a wide pH range. With addition of Fe-KCC-1, the ozone utilization increased nearly two times than single ozonation. The enhancement of SMT degradation was mainly due to the surface reaction, and the increased mineralization of SMT was due to radical mechanism. Fe-KCC-1 was an efficient catalyst for SMT degradation in catalytic ozonation system.

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

ABSTRACTThis 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.

Analysis of energy costs for catalytic ozone membrane filtration

Abstract Membrane fouling can be reduced through shear stress generated by cross-flow at the membrane surface. Previous work has shown that presence of ozone can reduce membrane fouling. In this work, the effect of ozonation and cross-flow on both membrane fouling on ceramic membranes and the energy cost for the process was studied. The effect of ozone dosage on membrane fouling was studied in both cross-flow and dead-end configurations. The performance of a manganese oxide coated membrane was compared with that of uncoated titanium oxide membrane. Membrane fouling decreased with increasing ozone dosages in the manganese oxide coated catalytic membrane, although increasing the dosage beyond 10–15 μg/s yielded limited improvement. The most energy-efficient mode of operation was found to be dead-end filtration using a manganese oxide coated membrane and a 10 μg/s ozone injection rate.

Abatement kinetics of highly concentrated 1H-Benzotriazole in aqueous solution by ozonation

Abstract In this work, we investigated the abatement of highly concentrated 1H-Benzotriazole (BTA) in aqueous solution by ozonation. Focusing on the COD removal and BTA degradation, the effects of different operational factors were explored, including different initial BTA concentrations (100–1000 mg/L), ozone dosages (16–48 mg/min) and initial pH values (3–11). It was found that the degradation of BTA was obviously affected by the initial concentration of BTA, pH value and O3 dosage. And the optimized pH value was observed at 11. The increasing of ozone dosage and the pH value would accelerate the degradation efficiency of BTA and COD removal, while the increasing of initial BTA concentration would hamper this process. Based on the effects of ozone dosage, initial BTA concentration and initial pH value, a kinetic model was established with the function of C = C0exp(−8.68QO32.4997C0−2.1262[OH−]0.0444t).

Degradation of di-2-ethylhexyl phthalate in aqueous solution by advanced oxidation process

Aims: This study was conducted to compare the effectiveness of conventional technologies, UV irradiation and ozonation process, and UV/O3 as advanced oxidation processes to remove phthalate from aqueous solutions. Materials and Methods: The initial concentration of di-2-ethylhexyl phthalate (DEHP) was 5 mg/L. The photolysis, ozonation, and UV/O3 processes were conducted separately at different contact times (5-30 min). Then, the DEHP residuals in the solutions were analyzed by gas chromatography mass spectrometry. The effect of ozone dosage was also evaluated in the range of 50-400 mg/h on DEHP degradation. Kinetic and the rate constants were determined. Results: The results indicated that using UV and ozonation alone, the maximum DEHP removal efficiency were 43% and 50%, respectively. The UV/O3 process considerably improved the degradation of DEHP up to 80%. The synergistic effect observed in the combined processes mainly due to the effects of UV in enhancing the ozone decomposition, led to higher degradation for 30 min treatment. A kinetic study showed the degradation in UV/O3 followed the first-order model. In addition, the maximum DEHP removal rate was 74% with 200 mg/h ozone dosage by ozonation alone process, but it was 93% at same condition by UV/O3 process. Conclusion: It could be found that the UV/O3 process is a method for DEHP degradation in aqueous solution and may be recommended as a supplement with other processes for treatment of solutions containing low DEHP concentrations.

Investigation on the Key Factors and the Solution for pH Value Decrease in Carbon Filter in O3-BAC Process

An investigation was carried out to eliminate the decrease of effluent pH value in carbon filter in O3-biological activated carbon process. The influence factors were examined in a pilot test, and pH was adjusted in the pilot and waterworks. Results show that the carbon filter is an acid-base buffer system and the activated carbon is the key factor. Chemical functional groups on activated carbon surface present acid-base properties to buffer the water but decrease with time, so that effluent pH value decreases. The effects of ozone dosage, CO2 in the carbon filter, and the filter influent quality are negligible. A new method to adjust pH is developed: the activated carbon is first modified by soaking in sodium hydroxide solution to make its pH reach the desired value, and then the pH value of inflow is controlled to certain value by dosing lime in sand filter influent. The method is economical and effective.

Control of disinfection by-product formation using ozone-based advanced oxidation processes

The effects of ozone dosage, water temperature and catalyst addition in an ozonation-fluidized bed reactor (O3/FBR) on treated water quality and on the control of chlorinated and ozonated disinfection by-products (DBPs) were investigated. A biofiltration column was used to evaluate its removal efficiency on biodegradable organic matter and to reduce DBP formation. The Dong-Gang River, polluted by agricultural and domestic wastewater in Pingtung, Taiwan, was used as the water source. The treated water quality in terms of dissolved organic carbon (DOC), biodegradable DOC, ultraviolet absorbance at 254 nm (UV254) and specific UV absorbance (SUVA) improved with increasing ozone and catalyst dosages. Catalytic ozonation was more effective than ozonation alone at reducing the formation of DBPs at a given dosage. Experimental results show that water temperature had little effect on the treated water quality with the O3/FBR system used in this study (p>0.05). The combination of O3/FBR and the biofiltration process effectively decreased the amount of DBP precursors. The concentration of total trihalomethanes (TTHMs) was less than the maximum contaminant level (MCL) requirement, which is 80 μg/L, for all treated waters and the concentration of five haloacetic acids (HAA5) fell below 60 μg/L with an ozone dosage higher than 2.5 mg/L.

Performance of polymeric membranes treating ozonated surface water: Effect of ozone dosage

Ozonation may have a significant impact on downstream water treatment unit processes. In this study, the effect of pre-ozonation of the feed surface water on the flux and rejection performance of polymeric nanofiltration (NF) and ultrafiltration (UF) membranes was investigated. The fouling and dissolved organic carbon (DOC) rejection characteristics of the membranes were found to depend on the ozonation dosage. In UF experiments, the DOC rejection was relatively low (11–26%) and was found to increase slightly with an increase in the ozone dosage. The increase in rejection with the ozone dosage was interpreted to stem from the higher polarity of ozonated NOM constituting the DOC-rejecting fouling layer. The propensity of the feed water to foul UF membranes increased with ozone dosage but the increase was statistically significant only at 82% confidence interval. In NF experiments, the increase in ozone dosage led to a statistically significant increase in the permeate flux while rejection remained consistently above 92%. The combined pore blockage-cake filtration model was applied to interpret NF flux data in terms of the dominant fouling mechanisms. Pore blockage, cake filtration and a transition regime were identified. Although pre-ozonation led to the formation of NF membrane cakes with higher specific resistance, the overall added hydraulic resistance due to fouling was lowered apparently due to a decrease in cake thickness.

Azo dye Acid Red 27 decomposition kinetics during ozone oxidation and adsorption processes

To elucidate the effects of ozone dosage, catalysts, and temperature on azo dye decomposition rate in treatment processes, the decomposition kinetics of Acid Red 27 by ozone was investigated. Acid Red 27 decomposition rate followed the first-order reaction with complete dye discoloration in 20 min of ozone reaction. The dye decay rate increases as ozone dosage increases. Using Mn, Zn and Ni as transition metal catalysts during the ozone oxidation process, Mn displayed the greatest catalytic effect with significant increase in the rate of decomposition. The rate of decomposition decreases with increase in temperature and beyond 40°C, increase in decomposition rate was followed by a corresponding increase in temperature. The FT-IR spectra in the range of 1000–1800 cm−1 revealed specific band variations after the ozone oxidation process, portraying structural changes traceable to cleavage of bonds in the benzene ring, the sulphite salt group, and the C-N located beside the -N = N- bond. From the 1H-NMR spectra, the breaking down of the benzene ring showed the disappearance of the 10 H peaks at 7-8 ppm, which later emerged with a new peak at 6.16 ppm. In a parallel batch test of azo dye Acid Red 27 adsorption onto activated carbon, a low adsorption capacity was observed in the adsorption test carried out after three minutes of ozone injection while the adsorption process without ozone injection yielded a high adsorption capacity.

Ozone enhanced activity of aqueous titanium dioxide suspensions for photodegradation of 4-chloronitrobenzene

The TiO 2/UV/O 3 process has been employed to remove 4-chloronitrobenzene (4-CNB) and compared to UV/air, O 3, TiO 2/O 3, TiO 2/UV/O 2 and UV/O 3 five parallel oxidation pathways. The reaction activities of these six processes were tested in aqueous using electron paramagnetic resonance (EPR) spin trapping technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trap. Moreover, the effects of ozone dosage, catalyst dosage and initial solution pH on the degradation of 4-CNB by TiO 2/UV/O 3 process were also investigated. Results showed that the TiO 2/UV/O 3 is the most efficient process for complete mineralization of 4-CNB since the combination of photocatalytic oxidation with ozone has a synergistic effect. The relative intensity of DMPO- OH follows the order of UV/air < O 3 < TiO 2/O 3 < UV/O 3 < TiO 2/UV/O 2 < TiO 2/UV/O 3. In TiO 2/UV/O 3 process, the ozone and catalyst dosage are found to have a significant impact on the process efficiency whereas initial pH has relatively less effect. Chlorine atoms of 4-CNB are absolutely oxidized to chloride anions when the ozone dosage in the range of 5–18 mg/min, or the catalyst dosage ranging from 1.0 to 2.0 g/L. Part of chloride anions would be further oxidized to chlorate(V) ions if the ozone dosage exceeds 24 mg/min, or the catalyst dosage exceeds 2.0 g/L.

Effect of ozone dosage and hydrodynamic conditions on the permeate flux in a hybrid ozonation–ceramic ultrafiltration system treating natural waters

The effect of ozone dosage and hydrodynamic conditions on permeate flux in a hybrid ozonation–ceramic ultrafiltration membrane system treating natural water was studied. Ozone injection into the feed water upstream from the membrane module resulted in an increase in the permeate flux over a wide range of operational conditions. At the same ozone dosage, less fouling was observed at higher cross-flow velocities and lower transmembrane pressures (TMP). At lower ozone dosages, the effects of cross-flow velocity and TMP on the extent of fouling were less pronounced. Ozone transfer efficiency from the gas phase to the bulk liquid phase was found to be higher at higher ozone concentrations, cross-flow velocities and TMPs. The accessibility of foulants to ozone at the catalytic membrane surface is believed to be a key factor affecting fouling behavior. The reduction of fouling observed in the hybrid system is largely due to the reaction of ozone or secondary oxidants, such as OH radical, with the foulants rather than to the effect of scouring by the bubbles present in the feed water. The total organic carbon (TOC) concentrations found in the retentate decreased with increasing ozone dosage. TMP and cross-flow velocity had little effect on retentate TOC levels.

UV/O 3-BAC process for removing organic pollutants in secondary effluents

The UV/O 3-BAC (biological activated carbon) process was employed to treat secondary effluents and compared to the O 3-BAC process. The effects of ozone dosage and empty bed contact time (EBCT) in BAC unit on dissolved organic carbon (DOC) removal were investigated. The results showed that the presence of UV improved ozone utilization and biodegradability of the effluent. DOC removal increased with ozone dosage and EBCT in BAC, however, 3 mg/L ozone dosage with 15 min oxidation time and 15 min EBCT in BAC were more economical and efficient. The synergetic effect in UV/O 3-BAC process is more than that in O 3-BAC process for DOC removal. Except for organic pollutants with MW >10,000 Da, those of other MW range were decomposed much more by UV/O3 process than by O3 process. GC/MS analysis showed dibutyl phthalate, bis(2-ethylhexyl) phthalate, 4-bromo-3-chloroaniline and other phenol derivatives were prevalent organic pollutants found in the secondary effluent. After UV/O3 treatment, some aromatic compounds including 2,4-dichloro-benzenamine, 4-bromo-3-chloroaniline and 3,5-dimethoxy-acetophenone disappeared and some small molecules were formed, but the kinds and concentration of organic pollutants including phthalate esters were greatly reduced by the subsequent BAC unit.

Comparison of O 3-BAC, UV/O 3-BAC and TiO 2/UV/O 3-BAC processes for removing organic pollutants in secondary effluents

Three processes combining different oxidations and subsequent biological activated carbon (BAC), i.e. O 3-BAC, UV/O 3-BAC and TiO 2/UV/O 3-BAC were employed to treat secondary effluents and compared. The effects of ozone dosage and empty bed contact time (EBCT) in BAC unit on dissolved organic carbon (DOC) removal were investigated. The results showed that the presence of UV and TiO 2 improved ozone utilization and biodegradability of the effluent. DOC removal increased with ozone dosage and EBCT in BAC, however, 3 mg/L ozone dosage with 15 min oxidation time and 15 min EBCT in BAC were more economical and efficient. The synergetic effect between oxidation and BAC is in the order: TiO 2/UV/O 3-BAC > UV/O 3-BAC > O 3-BAC. Among three oxidation processes, organic pollutants with molecular weight (MW) < 10,000 Da were mostly removed by TiO 2/UV/O 3, and those with MW > 10,000 Da were mostly removed by O 3 alone. GC–MS analysis showed dibutyl phthalate, bis(2-ethylhexyl) phthalate, 4-bromo-3-chloroaniline and other phenol derivatives were prevalent organic pollutants found in the secondary effluent. After TiO 2/UV/O 3 treatment, some aromatic compounds including 2,4-dichloro-benzenamine, 4-bromo-3-chloroaniline and 3,5-dimethoxy-acetophenone disappeared and some small molecules were formed, but the kinds and concentration of organic pollutants including phthalate esters were greatly reduced by the subsequent BAC unit.