Ozone Degradation of Iodinated Pharmaceutical Compounds

This study investigates the aqueous degradation of four iodinated x-ray contrast media (ICM) compounds (diatrizoate, iomeprol, iopromide, and iopamidol) by ozone and combined ozone and hydrogen peroxide. In laboratory scale experiments, second-order kinetic rate constants for the reactions of the ICM compounds with molecular ozone and hydroxyl radicals, and overall at pH 7.5, were determined. For the four ICM compounds the degradation rate constants with molecular ozone were low and in the range of 1–20?M?1?s?1, whereas the rate constants with hydroxyl radicals were in the range of 1×109–3×109?M?1?s?1. Diatrizoate had the lowest rate constant of the four compounds with respect to molecular ozone reactions. At pH 7.5, the extent of compound degradation was proportional to the applied ozone dose and inversely related to the initial compound concentration at a given ozone dose. At this pH approximately 90% of the degradation could be attributed to hydroxyl radical reactions. Enhancement of the radical mechanism by the addition of hydrogen peroxide during ozonation led to complete removal of the nonionic compounds, and >80% removal of diatrizoate, at relatively low oxidant mass ratios (H2O2/O3<0.25). A similar enhancement in compound degradation was evident with the presence of small concentrations of humic substances ( ～ 4–5?mg?L?1). Ozone oxidation led to major cleavage of the ICM compounds and the release of inorganic iodine; the proportion of iodine release was similar among the nonionic ICM compounds but much greater for diatrizoate.     

Bromate Formation by Ozone-VUV in Comparison with Ozone and Ozone-UV: Effects of pH, Ozone Dose, and VUV Power

The formation of bromate by ozone–vacuum ultraviolet (VUV) (185+254??nm) process in comparison with ozone and ozone-ultraviolet (UV) (254?nm) processes of coagulated and softened water was studied. The effects of pH (7, 9, and 11), ozone dosage (1, 2, and 4?mg O3/mg C), and VUV power (30, 60, and 120?W) were investigated. Bromate concentrations formed by the ozone-VUV process were up to four and six times less than those by the ozone and ozone-UV processes, respectively. Among the variables studied, ozone dosage had the most effect on bromate formation by the ozone-VUV process. Approximately 64 and 213% increases of bromate concentration were observed when the ozone dosage was increased from 1 to 2 and 4?mg O3/mg C with VUV power of 120?W at pH 7. The bromate formation also increased as VUV power and pH increased. Hydroxyl radical exposure had a positive relationship with ozone dosage and bromate formation. Results further indicated that it might be difficult to achieve the drinking water standard for bromate and high organic matter removal concurrently.     

Reaction Kinetics of Ozone in Variably Saturated Porous Media

A kinetic model based on the mass balance principle with equilibrium partitioning of gaseous ozone into pore water was developed to delineate the reactions of ozone in variably saturated porous media contaminated with phenanthrene. Dimensionless fraction factors were used in the kinetic model to account for the reactions of ozone with soil organic matter (SOM), metal oxide (MO), and phenanthrene as a function of water saturation. The enhanced removal of phenanthrene resulting from heterogeneous catalytic reactions between ozone and soil organic matter and metal oxide was incorporated as lumped parameters in the reaction rate coefficients of gaseous and dissolved ozone with phenanthrene. Laboratory experiments employing 5 cm long mini column reactor systems were conducted to estimate the reaction constants for three porous medium types (glass beads, baked field soil, and field soil) at various water-saturation levels. Water saturation and SOM were found to significantly affect the decomposition of gaseous ozone in both uncontaminated and contaminated porous media. It was found that water saturation over 75% completely eliminates gas-to-solid interfacial ozone reactions with SOM and MO. The kinetic model, with the reaction parameters estimated in this study, predicted reasonably well the experimental data obtained from both the mini column reactor and 20 cm long columns packed with field soil, suggesting that the kinetic model would be suitable for describing the fate and reactions of ozone in variably saturated porous media for soil types and experimental conditions similar to those tested in this study.     

Inactivation of Cryptosporidium Oocysts in a Pilot-Scale Ozone Bubble-Diffuser Contactor. I: Model Development

A mathematical model was developed to simulate the performance of a pilot-scale ozone bubble-diffuser column. The reactor hydrodynamics was represented with the axial dispersion reactor model. An analytical solution was developed for the liquid and gas phase ozone mass balances in which dissolved ozone decomposes by first-order kinetics. Numerical approximations were provided for the mass balances for viable microorganisms and the more general case of dissolved ozone decomposition through a second-order reaction with fast ozone demand in natural organic matter. Model components required to predict the liquid and gas phase ozone concentration and viable microorganism number density profiles throughout the bubble-diffuser column included input parameters (liquid and gas flow rates, influent gas and dissolved ozone concentrations, temperature, and countercurrent or cocurrent operation mode), empirical correlations (dispersion number, volumetric mass transfer coefficient, Henry’s law constant), and batch or semibatch kinetic information (ozone decomposition rate constants and fast-ozone demand, and microorganism inactivation lag phase and rate constant). A sample model run for the case of first-order ozone decomposition revealed that the analytical and numerical solutions were practically identical.     

Inactivation of Cryptosporidium Oocysts in a Pilot-Scale Ozone Bubble-Diffuser Contactor. II: Model Validation and Application

The axial dispersion reactor (ADR) model developed in Part I of this study was successfully validated with experimental data obtained for the inactivation of C. parvum and C. muris oocysts with a pilot-scale ozone-bubble diffuser contactor operated with treated Ohio River water. Kinetic parameters, required to model the effect of temperature on the decomposition of ozone in treated Ohio River water and oocyst inactivation, were determined from batch and semibatch ozonation experiments. The ADR model was used to simulate the effects of operating conditions (feed-gas ozone concentration, liquid flow rate, and gas flow rate), and water quality related parameters (fast ozone demand, first and second order ozone decomposition rate constants, and temperature) on the performance of the pilot-scale contactor. The model simulation provided valuable insight into understanding the performance of ozone disinfection systems and recommendations for ozone contactor design and optimization. For example, the simulation revealed that meeting inactivation requirements for C. parvum oocysts would be more challenging at relatively lower temperatures.     

Ozone Inactivation Kinetics of CRYPTOSPORIDIUM in Phosphate Buffer

The rate of inactivation of Cryptosporidium parvum oocysts by ozone in 0.05 M phosphate buffer at pH 6, 7, and 8 was studied at 22 ± 1°C in batch reactors. Infectivity in neonatal CD-1 mice was used as the criterion for oocyst viability. Ozone inactivation data were fitted to the Incomplete gamma Hom (I.g.H.) and Chick-Watson (n = 1) model, both of which incorporate a first-order rate constant for the disappearance of aqueous ozone during the contact time. For a 0.05 M phosphate buffer ranging in pH from 6 to 8, a single I.g.H. model was found to adequately describe the kinetics of Cryptosporidium inactivation by ozone at 22°C. The I.g.H. model for pH 6–8 was found to provide a significantly better fit to the ozone inactivation data when compared with the Chick-Watson model. The effect of pH on ozone inactivation kinetics was associated with ozone residual stability over the pH range of 6–8. The sensitivity of Cryptosporidium to ozone at 22°C was therefore not statistically different at pH 6 when compared with pH 8. The inactivation behavior of Cryptosporidium by ozone was characterized by a tailing-off effect, with approximately equal importance of ozone concentration and contact time. The I.g.H. model for pH 6–8 can be used as an aid in the design of ozone disinfection systems, and this robust fitted model was used to formulate ozone design criteria—the initial oxone residual required for a given contact time for 1, 2, and 3 log units inactivation of Cryptosporidium at 22°C. Uncertainty associated with the ozone design criteria for 2 log units inactivation was quantified using inverse prediction intervals. An ozone design criterion was established that gives a 95% probability of achieving 2 log units inactivation of Cryptosporidium at 22°C, corresponding to an approximate safety factor of 0.7 log units.     

Oxidation of Methyl Tert-Butyl Ether in Aqueous Solution by an Ozone/UV Process

In this paper, the oxidation of methyl tert-butyl ether (MTBE) in aqueous solution by an ozone/ultraviolet (UV) process was described. The oxidation process was investigated experimentally in a semibatch reactor under various operational conditions, i.e., ozone gas dosage, UV light intensity, and water quality in terms of varying bicarbonate concentration. The ozone/UV process was very successful in oxidizing MTBE. The rate of removal of MTBE increased when the incident UV light intensity increased for the same concentration of influent ozone gas. Similarly, an increase in influent ozone gas concentration resulted in faster removal of MTBE for the same incident UV light intensity. However, bicarbonate in the range of 2–8?mM showed no significant effect on MTBE removal for MTBE concentration ( ～ 1.0?mM) used in this study. Moreover, it was observed that the reaction intermediates could react well in the ozone/UV process, and complete mineralization could be achieved by the ozone/UV process, if desired.     

Modeling the Transformation of Chromophoric Natural Organic Matter during UV/H2O2 Advanced Oxidation

This research developed a differential kinetic model to predict the partial degradation of natural organic matter (NOM) during ultraviolet plus hydrogen peroxide (UV/H2O2) advanced oxidation treatment. The absorbance of 254?nm UV, representing chromophoric NOM (CNOM) was used as a surrogate to track the degradation of NOM. To obtain reaction rate constants not available in the literature, i.e., reactions between the hydroxyl radical (?OH) and NOM, experiments were conducted with “synthetic” water, using isolated Suwannee River NOM, and parameter estimation was applied to obtain the unknown model parameters. The reaction rate constant for the reaction between ?OH and total organic carbon (TOC), k?OH,TOC, was estimated at 1.14(±0.10)×104??L?mg-1?s-1, and the reaction rate constant between ?OH and CNOM, k?OH,CNOM, was estimated at 3.04(±0.33)×104??L?mol-1?s-1. The model was evaluated on two natural waters to predict the degradation of CNOM and H2O2 during UV/H2O2 treatment. Model predictions of CNOM degradation agreed well with the experimental results for UV/H2O2 treatment of the natural waters, with errors up to 6%. For the natural water with additional alkalinity, the model also predicted well the slower degradation of CNOM during UV/H2O2 treatment, owing to scavenging of ?OH by carbonate species. The model, however, underpredicted the degradation of H2O2, suggesting that, when NOM is present, mechanisms besides the photolysis of H2O2 contribute appreciably to H2O2 degradation.     

Decomposition of Aqueous 2,2,3,3-Tetra-Fluoro-Propanol by UV/O3 Process

2,2,3,3-Tetra-fluoro-propanol (TFP) has been extensively used in compact disk-recordable and digital versatile disk-recordable manufacture and a large amount of wastewater containing the chemical is being discharged. This investigation evaluates the feasibility and effectiveness of the use of UV, O3, and UV/O3 to degrade aqueous TFP. TFP oxidation tests were performed with initial TFP concentrations of 772–887?mg/L with various solution pH values (acidic, alkaline, uncontrolled), solution temperatures (26, 37, 48, and 60°C), and UV wavelengths (254 and 185?nm). Experimental results demonstrated that alkaline conditions favor the TFP degradation and increase the mass of TFP decomposition per unit mass of ozone consumption, in both UV254?nm/O3 and UV185?nm/O3 processes. There was no significant difference in the rate of TFP degradation when using either UV254?nm or UV185?nm. TFP exhibited zero-order degradation kinetics when sufficient ozone was supplied. A higher oxidation temperature was found to be no help for the UV/O3 oxidation of TFP in the tested concentration and temperature ranges. The cost of the UV254?nm/O3 or UV185?nm/O3 per unit volume of wastewater with an initial TFP concentration of 3,387?mg/L is comparable to that of the Fered–Fenton process as described in the literature.     

Fenton-Like Oxidation of Polycyclic Aromatic Hydrocarbons in Soils Using Electrokinetics

An integrated electrochemical oxidation process that utilizes electrokinetics (EK) to deliver the oxidant (5–10% hydrogen peroxide, H2O2) and chelant [40 mM of ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA)] or iron chelate (1.4 mM Fe-EDTA or Fe-DTPA) to oxidize polycyclic aromatic hydrocarbons (PAHs) in soils was investigated. Batch and bench-scale EK experiments were conducted using: (a) kaolin, a low permeability clayey soil, spiked with phenanthrene at 500 mg/kg, and (b) former manufactured gas plant (MGP) soil, a high buffering silty soil, contaminated by a variety of PAHs (1493 mg/kg). Batch experiments showed that chelant solutions dissolve native iron minerals to form soluble Fe-chelates that remain available even at higher pH conditions of soil for the Fenton-like oxidation of the PAHs. In EK experiments, a 5–10% H2O2 solution was delivered from the anode and a chelant solution or iron-chelate was delivered from the cathode. Preflushing of soil with 5% ethanol and ferrous sulfate (1.4 mM) prior to oxidant delivery was also investigated. An electric potential of 2 VDC/cm was applied in all tests to induce electroosmotic flow for 5–8 days for kaolin and 25 days for the MGP field soil. In the absence of any chelating agent, phenanthrene oxidation was catalyzed by native iron present in kaolin soil, and 49.8–82.3% of phenanthrene was oxidized by increasing H2O2 concentration from 5–10%. At 5% H2O2 concentration, phenanthrene oxidation was not increased by using 40 mM EDTA, 40 mM DTPA or 1.4 mM Fe-DTPA, but it increased to 70% using 1.4 mM Fe-EDTA. Maximum phenanthrene oxidation (90.5%) was observed by 5% ethanol preflushing and then treating with 5% H2O2 at the anode and 1.4 mM Fe-EDTA at the cathode. However, preflushing with 1.4 mM ferrous sulfate did not improve phenanthrene oxidation. The results with the MGP field soil indicated that delivery of 5% H2O2 alone resulted in oxidation of 39.8% of total PAHs (especially 2- and 3-ring PAHs). The use of EDTA and Fe-EDTA did not increase PAHs oxidation in this soil. Overall, the results reveal that an optimized in situ combined technology of EK and Fenton-like process has the potential to oxidize PAHs in low permeability and/or high buffering soils.     

Effect of Temperature on Ozone Inactivation of Cryptosporidium parvum in Oxidant Demand-Free Phosphate Buffer

Ozone inactivation of Cryptosporidium parvum oocysts was studied at bench-scale in 0.05 M phosphate buffer at 1 to 37°C, pH 6–8. Animal infectivity using neonatal CD-1 mice was used for evaluation of oocyst infectiousness following treatment. Survival curves of ozone inactivation were characterized by a tail-off effect, with an initial shoulder most evident at low temperature. Temperature was a critical factor for ozone inactivation kinetics with a significant decrease of ozone efficacy at low temperature. Accounting for ozone residual stability at different pH conditions, pH was found to have no significant effect on the activation of C. parvum by ozone. Inactivation kinetics at different temperatures were expressed as an Incomplete gamma Hom model with different reaction rate constants, adjusted for water temperature using the van't Hoff-Arrhenius relationship. Between 1 and 37°C, for every 10°C decrease in the water temperature, the inactivation rate constant decreased by a factor of 2.2, corresponding to activation energy of 51.7 kJ∕mol. Ozone disinfection design criteria for 1.0 and 2.0 log-units of inactivation of Cryptosporidium were developed for various water temperatures, and 90% confidence intervals are also provided.     

A novel method for endpoint temperature prediction in RH

Based on Cloud Model, a novel method was proposed to predict the endpoint temperature in Ruhrstahl Heraeus (RH) for Interstitial-free (IF) steel production, considering the starting temperature, scrap and refining cycle. 300 sets of RH production data was collected, mined and reasoned by Cloud Model. The prediction results of the Cloud Model are compared with BP neural network methods. The final results show that in the error scope from ?10 to 10°C, Cloud Model acquired the 93.32% hit rate, BP neural network acquired the 89.33% hit rate. Compared with the BP neural network, the Cloud Model has higher accuracy and stronger generalisation ability.     

Co-capping studies reveal CD8/TCR interactions after capping CD8 beta polypeptides and intracellular associations of CD8 with p56(lck)

A reaction-diffusion model was developed to predict the fate of nitric oxide (NO) released by cells of the immune system. The model was used to analyze data obtained previously using macrophages attached to microcarrier beads suspended in a stirred vessel. Activated macrophages synthesize NO, which is oxidized in the culture medium by molecular oxygen and superoxide (O2-, also released by the cells), yielding mainly nitrite (NO2-) and nitrate (NO3-) as the respective end products. In the analysis the reactor was divided into a "stagnant film" with position-dependent concentrations adjacent to a representative carrier bead and a well-mixed bulk solution. It was found that the concentration of NO was relatively uniform in the film. In contrast, essentially all of the O2- was calculated to be consumed within approximately 2 microm of the cell surfaces, due to its reaction with NO to yield peroxynitrite. The decomposition of peroxynitrite caused its concentration to fall to nearly zero over a distance of approximately 30 microm from the cells. Although the film regions (which had an effective thickness of 63 microm) comprised just 2% of the reactor volume and were predicted to account for only 6% of the NO2- formation under control conditions, they were calculated to be responsible for 99% of the NO3- formation. Superoxide dismutase in the medium (at 3.2 microM) was predicted to lower the ratio of NO3- to NO2- formation rates from near unity to <0.5, in reasonable agreement with the data. The NO3-/NO2- ratio was predicted to vary exponentially with the ratio of O2- to NO release rates from the cells. Recently reported reactions involving CO2 and bicarbonate were found to have important effects on the concentrations of peroxynitrite and nitrous anhydride, two of the compounds that have been implicated in NO cytotoxicity and mutagenesis.     

Prediction of Ozone Formation Based on Neural Network

The atmospheric ozone concentration in Seoul was forecasted using an artificial neural network and spatiotemporal analysis. The artificial neural network was trained by using hourly pollutant and meteorological data that resulted in complex patterns of ozone formation. The finite-volume method was employed in the spatiotemporal analysis in order to take into account the effects of wind. Time horizons in the forecasts were 1–6 h and 16–21 h. The resulting predictions of ozone formation were compared to measured data. From the comparison, it was found that the neural network method gave reliable accuracy within a limited prediction horizon.     

Evaluation of UV LEDs Performance in Photochemical Oxidation of Phenol in the Presence of H2O2

A novel application of ultraviolet (UV) light emitting diodes (LEDs) as a light source for the degradation of organic contaminant has been investigated. Photocleaving of hydrogen peroxide (H2O2) via UV LEDs photolysis resulted in the generation of hydroxyl radicals. It was found that phenol removal was insignificant in the absence of hydrogen peroxide, therefore oxidation of phenol was attributed to the formed radicals. Two criteria were selected to provide detailed information on the performance of UV LEDs in phenol oxidation: (1) the reaction quantum efficiency and (2) the energy consumption. Statistical tools such as the response surface methodology and the ANOVA were applied to estimate the influence of various process parameters such as the wavelength (255, 269, and 276 nm) and H2O2 to phenol molar ratio (5, 50, and 100) on phenol degradation reaction quantum efficiency. The decay of phenol (initial concentration of 1.06 mM) was the most pronounced at 255 nm and H2O2 to phenol molar ratio of 50. Finally, the “figure-of-merit” was used to estimate the specific energy consumption of the UV LED-based process.     

Modeling Water Treatment Chemical Disinfection Kinetics

Various empirical and probabilistic kinetic inactivation models that can be used to assist in the design and analysis of potable water disinfection systems were reviewed. Models were derived for both disinfectant demand-free and demand conditions. Ozone was used to inactivate heterotrophic plate count bacteria that were grown in natural water under low nutrient conditions and enumerated using R2A agar at 20°C for 7 days. Experiments were conducted at 22°C in 0.05 M (pH 6.9) phosphate buffer in bench-scale, batch 250 mL reactors. This disinfection data set, characterized by tailing-off behavior, was used to assess Chick–Watson, Hom-type, Rational, Hom–Power law, and Selleck model fit to the observed logarithmic survival ratios. It was found that the Chick–Watson model did not adequately represent the ozone disinfection kinetics. A Hom-type model incorporating a first-order disappearance term for ozone residual was found to best describe the observed inactivation of heterotrophic plate count bacteria. Named the incomplete gamma Hom model, it was found to be a robust kinetic model. The proposed incomplete gamma Hom model can be used to generate simple design charts for a wide range of disinfectant types, organisms, and conditions, as an aid to the design of water disinfection systems.     

Verification of Full-Scale Ozone Contactor Inactivation Performance Using Biodosimetry

A biodosimetric technique was used to verify the concentration-contact time (CT) values [CT10, CT integrated disinfection design framework (CT-IDDF), CT segregated flow analysis (CT-SFA)] of the ozone contactors of the DesBaillets water treatment plant (Montreal), using indigenous aerobic spore formers (ASFs) as indicators of disinfection efficiency. ASF measurement in ozonated water was performed using a large water sample concentration method. Four assays, completed over a 6-week period, involved the implementation of biodosimetric calibration curves using an ozone pilot apparatus and followed by full-scale verifications. ASF inactivation kinetics were well described by a simple Chick–Watson model. The most accurate data also indicated that the CT10 underestimates the effective CT (by 1.2–1.9-fold), whereas the CT-IDDF and CT-SFA overestimate it (by 1.0–1.7-fold and 0.9–1.5-fold, respectively). Underestimation from CT10 was more pronounced with increased ozone dose while overestimation from CT-IDDF and CT-SFA is most likely due to the difficulty in obtaining a representative ozone residual profile within the contactor. The use of segregated flow analysis provided the best estimate of disinfection performance. Biodosimetry is useful in measuring the effective CT transferred, in verifying model predictions, and in determining the influence of water quality on microbial inactivation.     

Calibration of Reactive Transport Models for Remediation of Mine Drainage in Solid-Substrate Biocolumns

Experimental data pertaining to two pairs of solid-substrate sulfate-reducing biocolumns for remediation of mine drainage were used for calibrating and testing new reactive transport models based on sulfate reduction and sulfide precipitation linked to rate-limiting solid-substrate hydrolysis. First-order (F) and Contois (C) kinetics for decomposition as well as different numbers of pools of decomposable materials were proposed in different models (F1–F3 and C1–C3). Effluent sulfate concentrations for one of the columns were used as the basis for calibrating the different models and, due to limitations in the calibration data set, the number of adjustable model parameters was limited using parameter tying. Calibrated models were ranked using Akaike information criterion, and Model C2, followed by Model C1, based on Contois kinetics, emerged as the models that were supported to a greater extent by the data. For an independent experimental data set, model testing was performed using Models C2 and C1 with parameters from the previous calibration resulting in good approximations of effluent sulfate. For the calibration data set, longer-term model predictions for effluent sulfate, decomposable substrates, and microbial populations also were performed. The reactive transport models represent a potentially valuable tool for the design of solid-substrate bioreactors used for the treatment of mining influenced water, although future model validation using longer-term field data sets will be necessary to confirm the model predictions.     

Simple Metal Sorption Model for Heterogeneous Sorbents: Application to Humic Materials

A semiempirical equilibrium model to simulate proton and metal binding to heterogeneous sorbents is presented. In the simple metal sorption (SiMS) model, proton and metal binding reactions to a heterogeneous surface are conceptualized as reactions with a single, composite “site,” with empirical correction factors to the equilibrium constants that are represented as simple power functions of hydrogen ion concentration, metal-to-ligand ratio (MeT∕LT), and ionic strength (I). That is, the observed metal-binding equilibrium constant, KMe,app, is represented as KMe,app = KMe{H+}α(MeT/LT)βI?. The validity of this approach is tested by fitting the model to a hypothetical multiligand data set and three data sets from the literature involving proton and metal binding to humic materials (two data sets involving Cu2+ and H+ binding, and one data set for binding of Co2+ and H+). Independent data sets involving Cu2+ binding are used for model prediction. The fitted models are used to contrast the three humic materials in terms of acid∕base characteristics and H+∕Me exchange ratios. A theoretical limitation of the model is that it does not satisfy the Gibbs-Duhem equation for thermodynamic consistency. The major advantages of the SiMS model are simplicity (i.e., few fitting parameters), flexibility in describing proton and metal binding to heterogeneous sorbents, and ease of application (model results presented in this paper were done on a standard spreadsheet). The model is presented not as a new development in the conceptual understanding of metal-humate interactions, but rather a practical engineering tool that can easily be incorporated into general fate and transport models.     

Degradation and Mineralization of Simazine in Aqueous Solution by Ozone/Hydrogen Peroxide Advanced Oxidation

Advanced oxidation of simazine in aqueous solution by the peroxone (hydrogen peroxide/ozone) treatment was investigated using Box-Behnken statistical experiment design and response surface methodology. Effects of pH, simazine and H2O2 concentrations on percent simazine and total organic carbon (TOC) removals were investigated. Ozone concentration was kept constant at 45?mg?L?1. The optimum conditions yielding the highest simazine and TOC removals were also determined. Both simazine and peroxide doses affected simazine removal while pH and pesticide dose had more pronounced effect on mineralization (TOC removal) of simazine. Nearly 95% removal of simazine was achieved within 5 min for simazine and peroxide concentrations of 2.0 and 75?mg?L?1, respectively at pH = 7. However, mineralization of simazine was not completed even after 60 min at simazine doses above 2?mg?L?1 indicating formation of some intermediate compounds. The optimum H2O2/pH/Simazine ratio resulting in maximum pesticide (94%) and TOC removal (82%) was found to be 75/11/0.5(mg?L?1).