Ozone-Induced Biodegradability Enhancement and Color Reduction of a Complex Pharmaceutical Effluent

The treatment of a complex pharmaceutical effluent using a combination of ozonation and biological treatment is reported with the use of ozonation as a pre- and posttreatment. Pretreatment facilitated biodegradability index (BI = BOD/COD) enhancement of up to 0.44 along with COD and color reduction of up to 42% and 33%, respectively. Subsequent anaerobic biodegradation of effluent indicated negligible biogas generation; however, aerobic biodegradation of pretreated effluent resulted in COD reduction (73%) and color reduction (62%), which was also indicated by the biokinetic parameters. Further, ozonation as a posttreatment led to higher overall COD (87%) and color (93%) removal.     

Biogas Production of Ozone and/or Microwave-Pretreated Canned Maize Production Sludge

The production of canned maize is accompanied by formation of large volumes of waste water, with high contents of starch, and high chemical- and biochemical oxygen demand. In our work the effects of acidic, microwave and ozone pretreatment on the biogas production and aerobic biodegradability of canned maize production sludge were examined and the energy balance of the processes were determined when different sludge pretreatments were used. It was found that ozone treatment decreased the chemical oxygen demand, while the biochemical oxygen demand and the aerobic biodegradability increased. The combination of microwave and ozone treatment increased the biodegradability relative to ozone treatment alone.     

Effect of Ozone on Removal of Dissolved Organic Matter and its Biodegradability and Adsorbability in Biotreated Textile Effluents

A study was conducted on the efficacy of ozonation in removing dissolved organic matter (DOM) in biotreated textile effluents and effects on its biodegradability and adsorbability. Results showed the efficient removal of color and fluorescence compounds were achieved through ozonation, due to increasing hydrophilicity and lowering molecular weight of DOM. A significant biodegradability improvement was also observed, and DOM adsorbability on activated carbon was highly dependent on ozone dosage. As the key parameter, consumed 3.8 g O₃/?g TOC₀ was the optimal dosage in the hybrid process combining ozonation with biological activated carbon (BAC) for wastewater reclamation.     

Soft-Sensor of Ozone Concentration in Ozone Generation System

The soft-sensor of ozone concentration is introduced. Six secondary variables are chosen in the soft-sensor model. The model is built based on the radial basis function neural network and its parameters are confirmed by the Gradient-descent algorithm. The model is implemented on the basis of the monitoring system that is necessary for ozone generation; thus, it requires no additional hardware cost. The response time of the model is less than 0.6 seconds. The experimental results indicate that the relative errors of the soft-sensor are less than 5%.     

Ozonation as a Pre-treatment for Anaerobic Digestion of Waste-Activated Sludge: Effect of the Ozone Doses

The aim of the present study was to improve the anaerobic biodegradability of waste-activated sludge by using ozonation. The effect of different ozone doses was assessed in terms of biogas production, maximum biogas production rate, and concentration of amino acids and long-chain fatty acids in the waste-activated sludge. Four different doses were used: 0.043 gO₃ g_TSS^?1, 0.063 gO₃ g_TSS^?1, 0.080 gO₃ g_TSS^?1, and 0.100 gO₃ g_TSS^?1. The lower doses resulted in biogas production increases and a higher maximum biogas production rate in the anaerobic digestion of waste-activated sludge, while the contrary occurred at higher doses. The amino acids and long-chain fatty acids concentrations decreased when the ozone dose increased. The correlation with the ozone dose was nonlinear for amino acids and linear for long-chain fatty acids. The reaction products of long-chain fatty acids (aldehydes) are proposed as the cause of inhibition observed in the anaerobic digestion of waste-activated sludge treated with higher ozone doses.     

Ozone Application for the Improvement of UASB Reactor Effluent. II. Toxicity Evaluation

In order to improve the effluent from domestic sewage treatment through an anaerobic process in an upflow anaerobic sludge blanket reactor (UASB), CETESB - The Environmental Protection Agency for Sao Paulo State, and FILSAN - Equipamentos e Sistemas S/A, developed a joint program to study the effectiveness of ozonation of the effluent as a post-treatment process. As the effluents treated by this system could contain toxic chemicals, Daphnia similis toxicity tests were applied. Two ozonation conditions were evaluated: (1) contact time of 30 min, mean ozone application dosage of 15.9 mg/L; (2) contact time of 50 min, mean ozone application of 16.7 mg/L. Toxicity reduction occurred for all samples but one. The ozonation system eliminated the residual toxicity associated with the effluent treated by the UASB reactor.     

The Effect of SF6 on Ozone Generation using Dielectric Barrier Discharge

This paper reports the results of an experimental study of effect of SF₆ on ozone generation within a Dielectric Barrier Discharge (DBD) fed by both pure oxygen and dry air. The chemical reaction mechanisms relevant to the process of ozone generation (and destruction) are discussed. The experimental results show the oxygen source should avoid the presence of SF₆ but the addition of a small amount of SF₆ in an air discharge can improve ozone concentration and ozone produce efficiency.     

Ozonation of NSAID: A Biodegradability and Toxicity Study

This work deals with the biodegradability and toxicity of three non-steroidal anti-inflammatory drugs (NSAID) (diclofenac, ibuprofen and naproxen) treated by ozonation. The results show that the total removal of 200 mg L^?1 of diclofenac and 100 mg L^?1 of naproxen is possible using an ozone dose of 0.20 and 0.04 g L^?1, respectively. For 200 mg L^?1 of ibuprofen, 90% removal is achieved using an ozone dose of 2.3 g L^?1. The BOD₅/COD ratio, the Zahn-Wallens test and EC₅₀ toxicity test (Microtox) are chosen as biological and toxicity indicators of NSAID intermediates. The evolution of BOD₅/COD ratio during 1 hour of treatment is evaluated and the results show that ozonation improves the biodegradability for the three NSAID treated solution. The Zahn-Wellens test for diclofenac and ibuprofen solutions shows that biological mineralization, after 28 days, is higher for diclofenac than for ibuprofen solution. According to the Microtox test, the treatment with ozone removes the toxicity of the naproxen solution. Taking into account the results obtained with the biocompatibility tests it could be assumed that ozonation is an adequate treatment for removal NSAID in aquatic medium, and the ozonated effluents could be post-treated in a biological wastewater facility.     

Effect of Ozone in UF-Membrane Flux and Dissolved Organic Matter of Secondary Effluent

The focus of this work was to determine the effect of ozone on the removal of dissolved organic matter (DOM) from a secondary effluent and its relation with the permeated flux behavior in an ultrafiltration membrane. To assess the ozone action, the DOM of the secondary effluent was fractionated into its hydrophobic, transphilic and hydrophilic fractions, using XAD-8 and XAD-4 resins. Ozone increased the hydrophilic fraction from 32% to 42%, and this percentage remained unchanged after ultrafiltration of the secondary effluent. Permeate flux dropped to 52% in the first hour of membrane operation, but when ozone was applied as a pretreatment, it could be maintained at 84% within the first hour.     

The Effects of Preozonation on the Biodegradability of Phenolic Solutions Using a New Gas-Inducing Reactor

To achieve effective COD removal, the combination of preozonation with biological treatment is necessary for phenolic wastewater treatments. Preozonation of 4-cresol, 2-chlorophenol and 4-nitrophenol solutions can be carried out with high ozone utilization rate using a new gas-inducing reactor. During the preozonation, the phenolic compounds can be completely decomposed with 100% ozone utilization rate. This new gas-inducing reactor is beneficial for the preozonation of phenolic solutions, comparing with a conventional gas-liquid reactor. The BOD₅ of preozonized phenolic solution is strongly related to both the degree of decomposition of phenolic compounds and the accumulation of intermediate products in aqueous solution. Based on the high ozone utilization rate, it is suggested that the optimal utilized ozone dose for 4-cresol, 2-chlorophenol and 4-nitrophenol can be chosen as 360, 350 and 400 mg/L, respectively. At those optimal utilized ozone doses, the ratio of BOD₅/COD of preozonized 4-cresol, 2-chlorophenol and 4-nitrophenol solutions increase to 0.33, 0.26 and 0.33, respectively.     

Ozone Decomposition over Cobalt Supported on Olive Stones Activated Carbon: Effect of Preparation Method on Catalyst Activity

Aqueous ozone decomposition was studied over highly dispersed cobalt nanoparticles supported on olive stones activated carbon (AC) prepared by: wetness impregnation (Co/AC_w) and incipient wetness impregnation (Co/AC_iw) with respect to pore volume. Nitrogen adsorption-desorption at 77K, SEM, XRD and XPS analyses were used to characterize the catalysts. Analyses results show that Co/AC_w was more uniformly dispersed on the AC than Co/AC_iw. The effect of the presence of tert-butanol as radical scavenger was also studied. Higher catalytic activity was measured for Co/AC_w than Co/AC_iw. Ozone decomposition extent goes to 99% in only 3 min in the presence of Co/AC_w compared to 60% and 58% using Co/AC_iw catalyst and AC, respectively.     

The Effect of Gaseous Diluents on Ozone Generation from Oxygen

Ozone generation in a negative corona discharge has been experimentally investigated using both a pure oxygen and in binary mixtures of oxygen with several gases. The concentration of ozone (O₃) in such mixtures is found to be dependent both on the input energy density η, dissipated in unit volume of gas mixture and on the type and the concentration of the additives. The experimentally measured dependencies of ozone concentration on the input energy density (O₃) = f(η) have been fitted using the Vasiliev–Kobozev–Eremin formula and the specific rate coefficients for ozone formation K_f and ozone decomposition K_d have been calculated. Using Ar, N₂ or CO₂ as admixtures, an increase in the specific rate coefficient for ozone generation was observed for increasing concentrations of added gaseous impurity into oxygen. In contrast, admixtures with SF₆ or CCl₂F₂ caused a substantial reduction of K_f values. The absolute values of ozone concentration at constant input energy density were observed to decrease with decreasing concentrations of oxygen in all mixtures.     

Examination of in situ Generation of Hydroxyl Radicals and Ozone in a Flow-through Electrochemical Reactor

Generation of hydroxyl radicals and ozone in a low ionic strength influent (0.001 M Na₂SO₄) treated in a continuous flow electrochemical (EC) reactor equipped with a cobalt-promoted lead dioxide anode was examined using p-chlorobenzoic acid (pCBA) and indigotrisulfonate (ITS) probes. EC generation of hydroxyl radicals via the oxidation of water was determined to precede that of ozone. OH· current yields were affected virtually solely by the current density, with almost negligible effects of variations of pH and carbonate concentrations. Absolute values of the current yields of EC generated OH· radicals were close to 1.0% for current densities > 30 mA/cm². The EC generation of ozone was suppressed in the presence of organic species, primarily due to the interception of OH· radicals that react with oxygen to form ozone. Apparent kinetic constants of major reactions associated with the EC generation of ozone were determined based on a steady-state model of an EC-controlled continuous flow reactor.     

High Frequency Testing and Modeling of Silent Discharge Ozone Generators

This paper deals with high frequency modeling of silent discharge ozone generators (OGs). The electrical characteristics of two simple silent discharge OGs operated at low and high frequency are analyzed and compared. An equivalent electric model is proposed for the operation of the OG at high frequency. This model can be used to optimize the electronic power converter used to supply silent discharge OGs at high frequency. Experimental results measured in the laboratory for two particular OGs are presented to validate the proposed model.     

Ozone Application for the Improvement of UASB Reactor Effluent I. Physical-Chemical and Biological Appraisal

Ozonation can improve the effluent characteristics of UASB (upflow anaerobic sludge blanket) reactors treating domestic sewage, by removing organic matter, solids, surfactants, color and microorganisms. In Brazil, part of the effluent of a 120 msup3; UASB reactor, fed with screened domestic sewage at an hydraulic retention time of 7 hours, was post-treated in a two-column ozonation system of 300 liters total volume. With a contact time of 50 minutes and ozone application dosage of 16.7 mg/L, the following removals were obtained at the ozonation step: 51‰ BOD, 56‰COD, 76‰ TSS, 62‰ color, and 91‰ surfactants. Pathogens and indicator organisms were inactivated to over 99.9‰. Ozonation completely destroyed Salmonella, protozoa cysts and helminth eggs and larvae.     

Ozonation and Advanced Oxidation of Wastewater: Effect of O3 Dose,pH, DOM and HO•-Scavengers on Ozone Decomposition and HO• Generation

The decomposition of ozone in wastewater is observed starting 350 milliseconds after ozone addition. It seems not to be controlled by the autocatalytic chain reaction, but rather by direct reactions with reactive moieties of the dissolved organic matter (DOM). A larger ozone dose increases ozone consumption prior to 350 milliseconds but decreases the rate of ozone decomposition later on; this effect is predicted by a second-order kinetic model. Transferred Ozone Dose (TOD) is poorly correlated with ozone exposure (= ∫[O₃]dt) indicating that TOD is not a suitable parameter for the prediction of disinfection or oxidation in wastewater. HO^? concentrations (> 10^?10 M) and R_ct (=∫[HO^?]dt/∫[O₃]dt > 10^?6) are larger than in most advanced oxidation processes (AOP) in natural waters, but rapidly decrease over time. R_ct also decreases with increasing pre-ozonation doses. An increase in pH accelerates ozone decomposition and HO^? generation; this effect is predicted by a kinetic model taking into account deprotonation of reactive moieties of the DOM. DOC emerges as a crucial water quality parameter that might be of use to normalize ozone doses when comparing ozonation in different wastewaters. A rapid drop of absorbance in the water matrix—with a maximum between 255–285 nm—is noticeable in the first 350 milliseconds and is directly proportional to ozone consumption. The rate of absorbance decrease at 285 nm is first order with respect to ozone concentration. A kinetic model is introduced to explore ozone decomposition induced by distributions of reactive moieties at sub-stoichiometric ozone concentrations. The model helps visualize and comprehend the operationally-defined “instantaneous ozone demand” observed during ozone batch experiments with DOM-containing waters.     

Inactivation of Bacillus cereus and Salmonella enterica serovar typhimurium by Aqueous Ozone: Modeling and UV-Vis Spectroscopic Analysis

Antibacterial efficacy of aqueous ozone (O₃) against B. cereus vegetative cells and S. typhimurium by was studied by using GInaFiT tool and results were validated using UV-Vis spectroscopy. Ozone gas was generated using a domestic ozone generator. Buffer solutions containing known amounts (≈10⁸–10⁹ cfu/mL) of bacterial pathogens were treated with aqueous ozone (200 mg/hr or 0.1 mg/l) for 16 min with sampling at 0-, 0.5-, 1-, 2-, 4-, 8- and 16-min intervals. A reduction of 4.6 log of B. cereus and 7.7 log cycle reduction of S. typhimurium was obtained in 16 min. Biphasic shoulder and double Weibull models were good fit for the experimental inactivation kinetics data. Principal Component Analysis showed discrete grouping based on the time of treatment. The highest correct classification results for SIMCA were achieved for both B. cereus and S. typhimurium after 1 and 8 min of treatment, respectively. In partial least squares regression analysis, maximum R² values for calibration and validation were found to be 0.84, 0.80 for B. cereus and 0.90, 0.89 for S. typhimurium, respectively.     

臭氧氧化法在干法腈纶废水处理中的应用研究

将臭氧氧化法应用于干法腈纶废水中,通过实验考察了回流量、进气量以及针阀开度等对废水处理效果的影响。实验结果表明,当针阀完全打开,进气量为2 L/min,回流量为500 L/h时,处理效果最好,CODCr去除率可以达到28.5%,废水的可生化性也有所改善。对预处理和后处理两种方式对比研究表明,臭氧与H2O2联用后处理干法腈纶废水的效果明显好于预处理效果,也明显好于单独臭氧作用的处理效果,反应60 min后,CODCr可去除70.3%,CODCr降至80.59 mg/L。因此,臭氧氧化法尤其是臭氧与H2O2联用适合作为干法腈纶废水的后处理措施。