Ozone-based Advanced Oxidation Processes Research Articles

Pilot Assessment of Impacts of Ozone and Ozone/Hydrogen Peroxide Treatment on the Fate of Per- and Polyfluoroalkyl Substances and Precursors.

Per- and polyfluoroalkyl substances (PFAS) make up a large class of anthropogenic micropollutants prevalent in wastewater. Oxidative processes commonly used in wastewater potable reuse treatment may affect transformation of PFAS precursors, leading to elevated concentrations of perfluorinated alkyl acids (PFAAs) that are significant health concerns. This work conducted a pilot-scale investigation to assess the influence of ozonation (O3) and ozone/hydrogen peroxide (O3/H2O2) advanced oxidation process (AOP), respectively, on the fate of PFAS in a wastewater effluent subjected to reuse. The study evaluated 40 target PFAS and associated precursors [based on the total oxidizable precursor (TOP) assay] under various treatment conditions, including different ozone doses (1.0-4.0 mg·L-1), H2O2 doses (0-0.20 mg·L-1), and contact time (0-20 min). Results indicated that short-chain (C3-C7) PFAAs dominated in concentrations, while overall PFAA concentrations were elevated by both oxidative treatment processes, particularly after high-dose ozonation treatment. TOP assays revealed that there were considerable amounts of PFAA precursors in the reuse wastewater, and their concentrations were decreased after the oxidative treatment with an increase of some of the PFAAs. This pilot study demonstrated that ozone and ozone-based AOP treatments can have a moderate influence on the transformation of PFAS and increase in PFAA levels under practical conditions.

The effect of pre-treatments on atrazine removal from source water by microbubble ozonation.

Ozone-based advanced oxidation processes (AOPs) have emerged a promising avenue for water treatment, offering effective removal of micropollutants. Recent research underscores the potential of ozone microbubbles to enhance ozone mass transfer during water treatment, particularly when combined with pre-treatment steps. This study aimed to evaluate the efficacy of three different combined processes (chlorine/KMnO4/PAC pre-treatment followed by ozonation) in removing atrazine, a common micropollutant from natural source water. Results revealed that all combined processes achieved higher atrazine removal rates compared to individual pre-treatment or ozonation methods. Notably, the highest atrazine removal rates were observed under alkaline pH conditions, with treatment outcomes influenced by oxidant dose and pH levels. Among the combined processes, chlorine pre-treatment followed by ozonation emerged as the most effective approach, achieving a removal rate of 59.7% that exceeded the sum of individual treatments. However, this treatment efficacy was affected by water quality parameters, particularly the presence of organic matter and elevated ammonia nitrogen concentration (> 0.5mg/L). This study highlights the potential for utilizing ozone micro/nanobubbles to enhance ozone mass transfer and offers valuable insights for optimizing the combined application of pre-treatment and ozonation strategies for efficient atrazine removal from natural water sources.

The treatment of high concentration wastewater in the natural gas processing industry.

The operation of the Cansolv tail gas treatment device in natural gas plants generates acidic and alkaline wastewater from the venturi unit and amine purification unit (APU), respectively. The APU wastewater is complex in composition and contains hard-to-degrade organic matter, which can adversely impact the normal functioning of the water treatment system. This study assesses the efficacy of three ozone-based advanced oxidation processes (ozone (O3), ozone/hydrogen peroxide (O3/H2O2), and ozone/Fenton (O3/Fenton)) for treating Cansolv wastewater, with chemical oxygen demand (COD) and total organic carbon (TOC) serving as indicators of organic degradation. The findings demonstrate that all three processes effectively eliminate coloration and reducible sulfur, with O3/Fenton exhibiting superior performance in removing organic substances. The treated wastewater has a clarified light-yellow appearance with residual COD levels at 43 mg L-1. Under the optimum Fenton oxidation conditions (initial pH 5, H2O2 dosage 97.8 mmol L-1, FeSO4·7H2O dosage 550 mg L-1), average TOC and COD removal rates reached 50% and 97%, respectively. After a treatment duration of 60 minutes, the wastewater demonstrated an enhanced membrane-specific flux, confirming the effectiveness of the O3/Fenton oxidation process in mitigating membrane fouling while ensuring the stable operation of the wastewater treatment system.

Application Of Advanced Oxidation Process Based on Ozone in Water Treatment

Wastewater treatment is an effective way to address water scarcity. Advanced oxidation processes (AOPs) are a wastewater treatment technology that is currently attracting a lot of attention, and it is a technology that uses physical or chemical pathways such as ozone, ultraviolet light, and the Fenton reaction to generate free radicals and then treats pathogens and organic pollutants by oxidation of the free radicals.Ozone is very strong oxidising agent and it has a powerful ability to break down wide range of organic and inorganic pollutants. However its usage in the wastewater treatment is still not very popular due to several drawbacks it posses, as it not possible to achieve the goal of wastewater treatment by ozone alone due to its mass transfer limitations, slow reaction rates, non specific for certain under low reaction rates pollutants select,may costs relatively higher thanother treatment processes etc. By combining ozone with H2O2, UV light, and catalysts, the efficiency of the wastewater treatment process will be increased because it will help make more hydroxyl radicals. This review discusses various ozone-based AOPs such as ozone/UV, ozone/hydrogen peroxide, and catalytic ozonation, focusing on their mechanisms and applications in wastewater treatment.

Integrated model of ozone mass transfer and oxidation kinetic: Construction, solving and analysis

Ozone-based advanced oxidation process (O3-AOPs) is rapidly evolving, but the surge of emerging pollutants brings new challenges for ozone oxidation research. Herein, we proposed a state-of-the-art model for simultaneously analyzing both ozone mass transfer and oxidation kinetics during ozone oxidation of emerging organic contaminants. The numerical solution and graphical representations of the integrated model were utilized to analyze the dynamics of ozone and pollutant concentration. An in-depth analysis of the integrated model revealed that the reaction rate constants in this present study were higher than previously reported apparent reaction rate constants, and catalysts were not always necessary. Finally, we developed an installable mobile application (APP) that allowed the simulation of the dynamic process for ozone oxidizing organic pollutants in the laboratory, which offered theoretical support for the selection of experimental conditions. The results of model simulation not only provide scientific explanations for counter-intuitive experimental phenomena, but also optimized experimental conditions to enhance ozone utilization.

Degradation of Odor Compounds in Drinking Water by Ozone and Ozone-Based Advanced Oxidation Processes: A Review

Degradation of Odor Compounds in Drinking Water by Ozone and Ozone-Based Advanced Oxidation Processes: A Review

Control of N-nitrosodimethylamine (NDMA) formation from N,N-dimethylhydrazine compounds by ozone-based advanced oxidation processes

N-nitrosodimethylamine (NDMA) is formed during ozonation of model compounds with dimethylhydrazine groups, such as daminozide (DMZ) and 2-furaldehyde 2,2-dimethylhydrazone (2-F-DMH) at pH 7 with yields of 100 % and 87 %, respectively. In this study, ozone/hydrogen peroxide (O3/H2O2) and ozone/peroxymonosulfate (O3/PMS) were investigated to control NDMA formation, and O3/PMS (50–65 %) was more effective than O3/H2O2 (10–25 %) with a ratio of H2O2 or PMS to O3 of 8:1. The reaction of PMS or H2O2 to decompose ozone could not compete with the ozonation of model compound because of the high second-order rate constants of the ozonation of DMZ (5 ×105 M−1 s−1) or 2-F-DMH (1.6 ×107 M−1 s−1). The Rct value of the sulfate radical (SO4•−) showed a linear relationship with NDMA formation, indicating that SO4•− significantly contributed to its control. NDMA formation could be further controlled by injecting small quantities of ozone numerous times to minimize the dissolved ozone concentration. The effects of tannic acid, bromide and bicarbonate on NDMA formation were also investigated during ozonation, O3/H2O2, and O3/PMS processes. Bromate formation was more pronounced in the O3/PMS process than in the O3/H2O2 process. Therefore, in practical applications of O3/H2O2 or O3/PMS processes, the generation of NDMA and bromate should be detected.

Combination of ozone-based advanced oxidation process and nanobubbles generation toward textile wastewater recovery

The intricate nature of various textile manufacturing processes introduces colored dyes, surfactants, and toxic chemicals that have been harmful to ecosystems in recent years. Here, a combination ozone-based advanced oxidation process (AOP) is coupled with a nanobubbles generator for the generation of ozone nanobubbles (NB) utilized the same to treat the primary effluent acquired from textile wastewaters. Here we find several key parameters such as chemical oxygen demand ammonia content (NH3), and total suspended solids indicating a substantial recovery in which the respective percentages of 81.1%, 30.81%, and 41.98%, upon 300 min residence time are achieved. On the other hand, the pH is shifted from 7.93 to 7.46, indicating the generation of hydrogen peroxide (H2O2) due to the termination reaction and the self-reaction of reactive oxygen species (ROS). We propose that the reactive oxygen species can be identified from the negative zeta potential measurement (−22.43 ± 0.34 mV) collected in the final state of treatment. The combined method has successfully generated ozone nanobubbles with 99.94% of size distributed in 216.9 nm. This highlights that enhancement of ozone’s reactivity plays a crucial role in improving the water quality of textile wastewater towards being technologically efficient to date.

Hybrid peroxi-coagulation/ozonation process for highly efficient removal of organic contaminants

Aromatic compounds such as phenols presented widely in coal chemical industry wastewater (CCW) render the treatment facing great challenge due to their biorefractory characteristics and potential risks to the environment and human health. Ozone-based advanced oxidation processes show promising for these pollutants removal, but the mineralization via ozonation alone is unsatisfactory and not cost-effective. Herein, a hybrid peroxi-coagulation/ozonation process (denoted as PCO) was developed using sacrificial iron plate as an anode and carbon black modified carbon felt as cathode in the presence of ozonation. An enhanced phenol removal of ∼100% within 20 min and phenol mineralization of ∼80% within 60 min were achieved with a low energy consumption of 0.35 kWh/g TOC. In this novel process, synergistic effect between ozonation and peroxi-coagulation was observed, and beside O3 direct oxidation, peroxone played a dominant role for phenol removal. In the PCO process, the hydrolyzed Fe species enhanced the generation of reactive oxygen species (ROS), while •OH was dominantly responsible for pollutant degradation. This process also illustrated high resistance to high ionic strength and better performance for TOC removal in real wastewater when compared with ozonation and peroxi-coagulation process. Therefore, this process is more cost-effective, being very promising for CCW treatment.

Comparison of ozone-based AOPs on the removal of organic matter from the secondary biochemical effluent of coking wastewater

ABSTRACT Advanced oxidation processes (AOPs) based on ozone are gaining continuously growing popularity in wastewater treatment. This study explored the treatment of coking wastewater using a combination of ozonation (O3), ultraviolet (UV), and hydrogen peroxide (H2O2) process expressed by % chemical oxygen demand (COD) removal, % total organic carbon (TOC), % UV254, % fluorescence intensity removal and its electrical energy consumption. The obtained results demonstrated that, the combination of O3, UV, and H2O2 which is denoted by O3/UV/H2O2 in this study achieved great success in COD removal (92.08%), TOC removal (78.25%), and reduction of fluorescence intensity (99.82%). Compared with the O3 and O3/UV processes, O3/UV/H2O2 improved the COD removal by approximately 54–69% and 38–51%, respectively. In addition, the energy consumption was reduced by 53–67%. The TOC removal rate in the effluent ranged 71% and 83%, while the UV254 removal rate was up to 90%. The fluorescence spectroscopy showed that the O3/UV/H2O2 combination process reduced the fluorescence intensity by almost 97% within 10 min. Furthermore, the total polycyclic aromatic hydrocarbons (PAHs) concentration in the effluent was less than 10μg/L (removal efficiency > 80%) and the most toxic benzo(a)pyrene (BaP) was less than 0.03 μg/L (0.018μg/L). In addition, the energy consumption of the O3/UV/H2O2 process was 53–67% lower than those of O3 and O3/UV processes. Furthermore, the energy consumption was 80.26 kWh m−3 after 60 min of reaction time when the COD (69.3 mg/L) met the standard discharge. Finally, the O3/UV/H2O2 process could be an effective method for improving the mineralisation of refractory organic matter.

Enhanced Hydraulic-driven piezoelectric ozonation performance by CNTs/BaTiO3 nanocatalyst for Ibuprofen removal

The performance of hydraulic-driven piezoelectric catalysis process is not satisfactory for refractory organics degradation. Although the ozonation process catalyzed by carbon nanotubes (CNTs) can increase the removal of refractory organics, the CNTs can be destroyed by ozone to reduce catalytic activity. Hence, a carbon nanotubes/BaTiO3 (CNTs/BT) composite was prepared and employed to catalyze ozone for ibuprofen (IBP) removal under hydraulic force. The removal rate of IBP in the CNTs/BT-O3 process was significantly higher than that in CNTs-O3 and BT-O3 processes. This outstanding performance was attributed to the adsorption and surface diffusion of CNTs, efficient electron transfer, as well as strong piezo-potential for abundant active species generation (such as OH and O2−). Notably, the removal of IBP only decreased by 3.19 % after 5 cycles of CNTs/BT composite with no metal ions leakage. In terms of energy consumption, the CNTs/BT-O3 process is not only superior to traditional ozone-based advanced oxidation processes (such as US-O3, UV-O3, and E-O3), but also outperforms the recently proposed piezoelectric ozonation process. Moreover, various refractory pollutants were effectively removed in CNTs/BT-O3 process, and satisfactory removal of IBP was observed in the actual water matrix. This study provides an effective and stable approach to removing refractory organics.

Comparison of macro and micro-pollutants abatement from biotreated landfill leachate by single ozonation, O3/H2O2, and catalytic ozonation processes

Micropollutants (MPs) in landfill leachate have attracted increasing attention because they pose a potential threat to the aquatic environment and ecosystems once discharged into nearby aquifers without proper treatment. Although ozone-based oxidative techniques perform well for the removal of MPs in low-strength water streams, their role in leachate containing high dissolved organic matter (DOM) concentration requires further exploration. Moreover, it is unclear the mechanism of different ozone-based processes in advanced treatment for biotreated landfill leachate. This study compared the single ozonation and two ozone-based advanced oxidation processes (AOPs, heterogeneous catalytic ozonation and O3/H2O2 process) for polishing biotreated leachate. The mechanism of different ozone-based processes during leachate treatment was explored, which facilitates selecting of the appropriate process based on leachate quality and target treatment requirements. The removal efficiency and energy requirements of the macro and micro-pollutants were evaluated. The results revealed that the role of catalytic ozonation is mainly to enhance the direct ozone oxidation, whereas the O3/H2O2 process is to promote the indirect oxidation. The strengthening effect was most visible in the early stage (specific transferred ozone dose (STOD) < 2 gO3/gDOC) for catalytic ozonation, whereas it was more pronounced in the later stage for the O3/H2O2 process. The removal of UV-quenching substances correlated well with the elimination of MPs (R2 > 0.95), which provides a surrogate-based predictive model for the removal of MPs from high-strength leachate. Catalytic ozonation consumed the least amount of energy when the desired chemical oxygen demand (COD) removal was ≤ 35 %, otherwise, the O3/H2O2 process was the most energy-efficient. In any process, MPs with O3 or OH reactivity could achieve more than 90 % elimination when the COD removal exceeded 30 %.

Elimination of neonicotinoids by ozone-based advanced oxidation processes: Kinetics and performance in real water matrices

The Decision 2018/840 included some neonicotinoid insecticides (thiamethoxam (TMX), imidacloprid (ICP), clothianidin (CTD), thiacloprid (TCP), and acetamiprid (AMP)) within the watch list of substances for Union-wide monitoring in the field of water policy due to their potential risk to human health and the environment. In this work, the study of the elimination of these five neonicotinoids present in waters by ozone-based oxidation treatments has been carried out. While AMP and TCP presented very low rate constants with ozone and were hardly degraded, CTD (ozone rate constant of 116 M−1 s−1 at pH ≥ 7) and TMX (ozone rate constant of 22.7 M−1 s−1 for the studied pH range) were partially degraded by ozone. Furthermore, ICP ozonation showed a great pH dependence, with increasing ozone rate constant values from 2.7 M−1 s−1 at pH 5 to 160 M−1 s−1 at pH 9. In addition, rate constants for the reaction of neonicotinoids with hydroxyl radicals (•OH) were determined to be in the range (2.0–4.5)·109 M−1 s−1. The specific contribution of direct ozonation and radical pathways to the overall neonicotinoid degradation was evaluated, being the indirect oxidation with •OH dominant over direct ozone reactions. The influence of real water constituents such as dissolved organic matter (DOM) and bicarbonate, both acting as radical scavengers, on the ozonation process was negative. The ozone dose and the specific ozone dose required to remove neonicotinoids from real water matrices were higher than 5 mg/L and 1 mg O3 mg DOC-1, respectively, typically applied in water treatment. However, the application of the ozone-based advanced oxidation processes O3/H2O2 and O3/activated carbon provided an appreciable improvement in the elimination of neonicotinoids compared to ozone alone. Therefore, ozone-based advanced oxidation processes are needed to sufficiently abate neonicotinoids in contaminated waters.

Insights into the mechanism of electrostatic field promoting ozone mass transfer in water: A molecular dynamics perspective

Ozone is the main role of ozone-based advanced oxidation process for organic wastewater treatment, which is usually added in water by aeration. However, the low solubility of ozone in water seriously affects the degradation efficiency. In this article, the external electrostatic field (EF) was proposed to improve the ozone solubility in water. The mass transfer characteristics of ozone in a gas-liquid two-phase system under EF were studied by molecular dynamics (MD) simulation. The microscopic mechanism of ozone mass transfer in water promoted by external EF was revealed by analyzing Gibbs dividing surface (GDS) interface structure, interfacial water molecular orientation, surface tension, liquid phase viscosity, hydrogen bond network and ozone self-diffusion coefficient. Our findings reveal that EF can enhance the thickness of GDS region (from 0.4648 nm to 0.4996 nm when EF is 0.2 V/nm) as well as its ozone content. The dipole moment orientation of water molecules also tends to point in the EF direction due to the influence of EF, making the difference in dipole moment orientation of water molecules in the first and second layers of GDS region gradually disappear. In addition, compared with the absence of EF, the existence of external EF can decrease the surface tension (from 77.6162 mN/m to 73.3480 mN/m when EF is 0.2 V/nm) at the gas-liquid interface and the viscosity of liquid phase (from 0.293 mPa·s to 0.162 mPa·s when EF is 0.2 V/nm), break the network of hydrogen bond in liquid phase, and increase the mobility of ozone (self-diffusion coefficient of ozone changes from 1.3232 × 10−6 cm2·s−1 to 1.8812 × 10−6 cm2·s−1 when EF is 0.2 V/nm). All these properties changes indicate that the presence of external EF enhances the ability of ozone to penetrate the interface of the two-phase system, and then improves the ozone mass transfer efficiency in water.

Effect of pre-coagulation on catalytic ozonation in the tertiary treatment of coking wastewater: Kinetic and ozone consumption analysis

The ozone-based advanced oxidation process in wastewater effluent degrades refractory organics efficiently and significantly. Nevertheless, high energy consumption is a challenge that hinders its widespread application. In this work, the pre-coagulation enhanced catalytic ozonation process for the treatment of biologically treated coking wastewater (BTCW) was investigated. The chemical oxygen demand (COD) removal results indicated that catalytic ozonation has an inadequate removal effect on the organic pollutants in BTCW. Moreover, the two-stage degradation occurred in the COD ozonation process, of which the slow reaction rate in the second stage was the main reason that limited its overall effect. The pre-coagulation overcame the obstacle of the limited effect of catalytic ozonation treatment of BTCW because of its ability to remove hydrophobic organics. The combination of pre-coagulation with catalytic ozonation could increase the COD removal efficiency from 45% to 69% compared with catalytic ozonation alone. There was a linear relationship between specific ozone consumption and ozone dosage regardless of whether BTCW was subjected to pre-coagulation. The fact that the slope of this linear relationship with pre-coagulation was much smaller than that without pre-coagulation. It indicates that pre-coagulation could significantly reduce ozone consumption. The primary role of pre-coagulation was to reduce ozone consumption considerably in the second stage of the ozonation process. The ozone consumption per unit mass of COD in the second stage reached 24.3 gO3/gCOD without pre-coagulation, while that was only 6.8 gO3/gCOD with pre-coagulation.

Degradation of Organics and Change Concentration in Per-Fluorinated Compounds (PFCs) during Ozonation and UV/H2O2 Advanced Treatment of Tertiary-Treated Sewage

This study aimed to investigate the effect of H2O2 addition, ozone feed rate, and UV addition on the change in the concentration of organics such as CODMn, CODCr, TOC, and PFCs in tertiary-treated effluent from a sewage treatment plant (STP) during the O3 and UV/H2O2 process. The degradation of organic pollutants from tertiary effluent is a significant challenge because biological treatment cannot degrade these recalcitrant pollutants. Therefore, the O3/UV/H2O2 process was an effective method for treating recalcitrant organics. Several batch tests were conducted to investigate the direct UV photolysis, UV/H2O2, and ozone-based advanced oxidation process to degrade CODMn, CODCr, TOC, and PFCs. The chemical oxygen demand (COD) and total organic carbon (TOC) with UV irradiation showed 95% and 50% removal efficiency percentages under optimal conditions (initial pH = 6.7, H2O2 dosage = 50 mg/L, ozone feed rate = 5.8 mg/L/min. Moreover, UV irradiation, with the addition of H2O2, and a sufficient dose of ozone, demonstrated the efficient removal of organic compounds by the indication of radical oxidation. (·OH) is the dominant mechanism. However, AOPs are not sufficient to fully treat the PFC compound; thus, additional procedures are required to degrade PFCs. In this study, the removal of organic recalcitrant contaminants and the change in added PFC concentration in tertiary-treated sewage were investigated by applying the ozone-based advanced oxidation process.

Comparative study of ozone-based AOPs for degradation of Reactive Red 120

The present work focuses on the comparative study of ozone-based advanced oxidation processes (AOPs): O3, O3/UV and O3/UV/PS to degrade synthetic wastewater containing Reactive Red 120 (RR120) dye. The effect of various parameters: pH, ozone flow rate, initial concentration of dye, persulfate dosage and UV light intensity was analyzed to assess the performance efficiency of AOPs. All three AOPs' performance was evaluated on decolorization, %TOC removal and ozone consumption. The highest degradation rate of 86.83% was achieved for O3/UV/PS, followed by 71.53% and 66.82% for O3/UV and O3 respectively. This better efficiency of O3/UV/PS is attributed to the fact that persulfate ions (S2O8 2-) upon activation produce sulfate radical (SO4 - ●), which is a powerful oxidant capable of degrading a wide variety of recalcitrant organic compounds. The study reveals that the efficiency of degradation of RR120 follows the order: O3/UV/PS &gt; O3/UV &gt; O3.

Elimination of Neonicotinoids by Ozone-Based Advanced Oxidation Processes: Kinetics and Performance in Real Water Matrices

Elimination of Neonicotinoids by Ozone-Based Advanced Oxidation Processes: Kinetics and Performance in Real Water Matrices

A new insight into catalytic ozonation of sulfasalazine antibiotic by plasma-treated limonite nanostructures: Experimental, modeling and mechanism

This study investigates the application of novel natural and plasma-treated iron (III) oxide-hydroxide (limonite) catalysts on the degradation/mineralization of sulfasalazine (SSZ) antibiotic by ozone-based advanced oxidation processes (AOPs). The limonite nanostructures were prepared by non-precursor, environmentally friendly, and fast glow discharge plasma technology under oxygen (PTL/O2) and oxygen/argon (PTL/O2/Ar) gaseous atmosphere.The characteristic analysis demonstrated enhanced surface area, morphology, active surface sites, and physical stability after the plasma treatment. It was found that SSZ degradation/mineralization was effectively improved (36%) in the heterogeneous catalytic ozonation process (HCOP) using PTL/O2/Ar compared to sole ozonation. Modeling and optimization of SSZ degradation through the central composite design (CCD) and artificial neural network (ANN, topology of 4:7:1) showed that complete SSZ degradation can be achieved at the optimized condition (initial pH = 7, ozone concentration = 15 mg L-1, catalyst loading = 1.5 g L-1 and treatment time = 50 min). The effect of organic and inorganic salts confirmed that the reactive oxygen species, mainly hydroxyl radicals, were responsible for SSZ degradation by HCOP. The main intermediates during SSZ oxidation were identified. The toxicity of SSZ solution and electrical energy consumption were decreased using PTL/O2/Ar nanocatalysts in HCOP. Economic studies demonstrated 46% reduction in energy consumption of HCOP using PTL/O2/Ar compared to NL samples. For the first time, molecular dynamics simulation was applied to provide a deeper insight into the adsorption mechanisms of SSZ and ozone onto limonite surface (111) during HCOP.

Treatment of Leachate from Open Dumpsite of Municipal Solid Waste by Ozone Based Advanced Oxidation Process

ABSTRACT Open dumping of Municipal Solid Waste (MSW) results in generation of leachate that contains large amounts of organic matter, ammonia, heavy metals, chlorinated organics, phenolic compounds, phthalates, and pesticide residues which irreparably contaminate both surface and groundwater. Advanced Oxidation Processes (AOP) have been reported as one of the effective treatment methods, especially in improving the biodegradability of the leachate as well as effective in removing recalcitrant organics. With AOP pre-treatment rendered the leachate becomes more amenable to further treatment using biological treatment, adsorption, or ion-exchange processes. The study reported in this paper mainly aims at assessing the suitability of ozone and peroxone (O3+H2O2) based advanced oxidation processes (AOP) for the treatment of MSW leachate from the open dumpsite. The effect of reaction time, impact of O3 dose, and H2O2 concentration on the efficiency of COD removal, improvement in the biodegradability of the leachate, and pH change were determined as the performance parameters for the treatment process. The maximum COD removal efficiency was found to be 46% and 82% with ozone alone (3975 mg/L) and with ozone (9275 mg/L) + 50 mg/L H2O2 each with 120 min. reaction time. It is also found that the BOD5/COD ratio has been increased from 0.09 to 0.58 at optimum O3 + 50 mg/L H2O2 treatment would offer as an effective method for increasing the biodegradability.