TOC Degradation Research Articles

Evaluation of Performance of Hybrid Photolysis-DCMD and Photocatalysis-DCMD Systems Utilizing UV-C Radiation for Removal of Diclofenac Sodium Salt From Water

The removal of a non-steroidal anti-inflammatory drug (NSAID) diclofenac sodium salt (DCF, C14H10Cl2NNaO2) from water in two hybrid systems coupling photolysis or photocatalysis with direct contact membrane distillation (DCMD) is presented. A UV-C germicidal lamp was used as a source of irradiation. The initial concentration of DCF was in the range of 0.005-0.15 mmol/dm3 and the TiO2 Aeroxide® P25 loading (hybrid photocatalysis-DCMD) ranged from 0.05 to 0.4 g/dm3. Regardless of the applied hybrid system and the initial concentration of DCF, the model drug was completely decomposed within 4h of irradiation or less. Mineralization was less efficient than photodecomposition. In case of the hybrid photolysis-DCMD process the efficiency of TOC degradation after 5h of irradiation ranged from 27.3-48.7% depending on the DCF initial concentration. The addition of TiO2 allowed to improve the efficiency of TOC removal. The highest degradation rate was obtained at 0.3 gTiO2/dm3. During the process conducted with the lowest DCF initial concentrations (0.005-0.025 mmol/dm3) a complete mineralization was obtained. However, when higher initial amounts of DCF were used (0.05-0.15 mmol/dm3), the efficiency of TOC degradation was in the range of 82.5-85%. The quality of distillate was high regardless of the system: DCF was not detected, TOC concentration did not exceeded 0.7 mg/dm3 (1.9 mg/dm3 in permeate) and conductivity was lower than 1.6 μS/cm.

Compact AOP system

An all-in-one type compact Advanced oxidation process (AOP) system using UV/O3/TiO2 for water purification has been developed. Since all elements are packed in one case, portability and easy installation are facilitated. The ozonizer in this system is newly designed for generating ozone gas just before injection and the extending life time of electrodes. TOC degradation ability is confirmed by using sodium acetate solution. The performance of this AOP system is demonstrated for hydroponics. This system can kill bacteria in fertilizer solution, increase dissolved oxygen and no influence for fertilizer elements. From the results of tomato hydroponic tests, tomato growth using this system is much faster than without the system. It is clearly turned out that this AOP system is suitable for hydroponics.

Mineralization of AV dye in water by solar Fenton-like process

Abstract In this study, treatment of alizarin violet 3B (AV) dye in water by a artificial solar irradiation assisted Fenton-like process was investigated. Optimized reaction conditions based on response surface methodology (RSM) were established under a [H2O2]0/COD ratio of 1.75, a [H2O2]0/[Fe3+]0 molar ratio of 15 and a reaction time of 15 min in which the COD and TOC degradation efficiency of AV would be more than 90%. As compared to conventional Fenton-like process, the solar Fenton-like process with an irradiation of 500 W/m2 increased the mineralization reaction rate by a factor of 6.9, and the mineralization efficiency was increased from 65% to 92% as the temperature of water was raised from 15 to 35 °C due to solar heat irradiation. Accordingly, solar energy consisting of light energy and heat irradiation showed a hybrid promoting effect on the Fenton-like reaction.

The effects of aqueous bicarbonate and calcium ions on uranium biosorption by Arthrobacter G975 strain

Uranium (VI) biosorption was investigated using carbonate-free and carbonate amended synthetic groundwater (SGW) under conditions relevant to Ca-rich carbonate-bearing subsurface environments. SGW was amended with bicarbonate concentrations ranging between 0.5 and 5mM and a G975 Arthrobacter oxydans strain, a soil bacterium previously isolated from Hanford Site soil. Selected treatments were amended with 5mM of calcium to evaluate its effect on U(VI) biosorption. The study confirmed that Arthrobacter sp. G975 can effectively remove soluble U(VI) ions from aqueous solution. The Langmuir, Linear, and Freundlich isotherms were fitted to the experimental data. Based on a higher correlation coefficient, the data was better fit by the Langmuir model. The presence of calcium and bicarbonate ions in SGW affects the sorption behavior of U(VI) due to the formation of highly soluble and stable uranyl-carbonate and calcium uranyl carbonate complexes that reduce adsorption of U(VI). Increasing aqueous bicarbonate concentrations exponentially reduced the U(VI) microbial adsorption compared to values obtained in carbonate-free solutions. The differences in U(VI) uptake generated by calcium additions in bicarbonate-free solutions were small enough to conclude that calcium was not a governing factor in biosorption. Results suggest that in the presence of bicarbonate and calcium, the damage to bacterial cells caused by U(VI) toxicity was reduced, yielding similar values for TOC degradation and cell density compared to U(VI)-free controls.

Decolorization and mineralization of Diarylide Yellow 12 (PY12) by photo-Fenton process: the Response Surface Methodology as the optimization tool

The Response Surface Methodology (RSM) was applied as a tool for the optimization of the operational conditions of the photo-degradation of highly concentrated PY12 wastewater, resulting from a textile industry located in the suburbs of Medellin (Colombia). The Box-Behnken experimental Design (BBD) was chosen for the purpose of response optimization. The photo-Fenton process was carried out in a laboratory-scale batch photo-reactor. A multifactorial experimental design was proposed, including the following variables: the initial dyestuff concentration, the H(2)O(2) and the Fe(+2) concentrations, as well as the UV wavelength radiation. The photo-Fenton process performed at the optimized conditions resulted in ca. 100% of dyestuff decolorization, 92% of COD and 82% of TOC degradation. A kinetic study was accomplished, including the identification of some intermediate compounds generated during the oxidation process. The water biodegradability reached a final DBO(5)/DQO = 0.86 value.

Solar Photocatalytic Degradation of Azo Dye in AqueousTiO2Suspension Assisted by Fresnel Lens

Solar TiO2photocatalytic process assisted by a Fresnel lens was investigated for treating an azo dye wastewater of Acid Orange 10 (AO10). Response surface methodology (RSM) was employed to assess the effect of critical process parameters (including initial pH of wastewater, concentration of TiO2, and reaction time) on treatment performance in terms of COD and TOC degradation efficiency. Optimized reaction conditions based on the analysis of RSM were established under an initial pH of 6.0, a concentration of TiO2of 1 g/L, and a reaction time of 2 h for reaching a 90% COD and TOC degradation of AO10 wastewater. With the assistance of Fresnel lens, the TOC degradation rate of AO10 wastewater increased significantly from 0.606 h−1and 0.289 h−1to 1.477 h−1and 0.866 h−1in summer (June) season (UV280–400 nm nm: 39.9–44.8 W/m2) and winter (December) season (UV280–400 nm nm: 23.9–26.9 W/m2), respectively. This could be mainly due to the concentrating effect of Fresnel lens for solar energy, resulting in an increase of 2~2.5 times of solar light intensity and a raising heat irradiation in terms of 10~15 °C of wastewater temperature. These results revealed that solar energy could be concentrated effectively by using Fresnel lens and showed a significant promoting effect on the TiO2photocatalytic degradation of dye wastewater.

Veruclay – a new type of photo-adsorbent active in the visible light range: modification of montmorillonite surface with organic surfactant

Montmorillonite K10 was treated with VeruSOL-3, a biodegradable and food-grade surfactant mixture of coconut oil, castor oil and citrus extracts, to manufacture a benign catalytic adsorbent that is active in the visible light. Veruclay was characterized by SEM, XRD, TGA, UVDRS, and XPS analysis. The catalytic adsorption of cationic dye methylene blue (MB) and halogenated aromatic dichlorophenol (DCP) in the dark and visible light was assessed through the bench scale experiments. It was found that in the presence of visible light, MB degradation was nearly 100% in 45 min, whereas 75% of DCP was removed in 4 h. Demineralization of the solution in terms of TOC degradation of 18, 59, and 74% was achieved with 0.5, 1, and 2 g L−1 of Veruclay, respectively with DCP as a contaminant. Bacterial (Vibrio fischeri) bioluminescence inhibition assay demonstrated the effectiveness of Veruclay to significantly inhibit the microbial growth even at relatively low (50 mg L−1) Veruclay concentrations. It exhibited excellent stability for up to 7 consecutive runs and regained most of its catalytic activity after intermediate calcination.

Application of Ozone Involving Advanced Oxidation Processes to Remove Some Pharmaceutical Compounds from Urban Wastewaters

Different UVA radiation and advanced oxidation systems, most of them involving ozone, have been applied to remove mixtures of three contaminants of pharmaceutical type: diclofenac (DCF), sulfamethoxazole (SMT) and caffeine (CFF), both in ultrapure and secondary treated wastewater. The influence of the water matrix has been studied in terms of individual compound concentration and TOC removal. Also, biodegradability of the treated wastewater before and after the advanced oxidation process, as BOD/COD ratio, the partial oxidation yield, the increment of average state of carbon oxidation and ozone consumption have been determined. For mgL−1 to 100 μgL−1 concentrations and regardless of the ozone process and water type, DCF and SMT are removed in less than 10 min mainly by direct reaction with ozone, especially in the case of DCF. CFF, on the contrary, is mainly removed through hydroxyl radicals. For lower concentration (≤100 μgL−1), DCF still disappears by direct ozonation, CFF by hydroxyl radicals oxidation and SMT through both direct ozonation and hydroxyl radical oxidation. Once DCF and SMT have disappeared, TOC is removed by reacting with hydroxyl radicals, regardless of the water matrix. Photocatalytic ozonation allows the highest TOC degradation rate, partial oxidation yield, increment of average state of carbon oxidation and biodegradability together to the lowest ozone consumption per mg TOC eliminated.

Wet air oxidation and catalytic wet air oxidation for dyes degradation

Textile industry produces wastewater which contributes to water pollution since it utilizes a lot of chemicals. Preliminary studies show that the wastewater from textile industries contains grease, wax, surfactant, and dyes. The objective of this study was to determine the treatment efficiency of the nickel catalysts supported on hydrotalcites in three-dye model compounds and two types of wastewater. Hydrotalcites were employed to prepare supported nickel catalysts by wetness impregnation technique. Metal loadings from 1 to 10 wt% were tested. Catalysts were characterized by several techniques. They were tested in a catalytic wet air oxidation of three dyes and two wastewaters with different origins. It could be observed that the higher the metal content, the lower the BET area, possibly due to sintering of Ni and the consequent blocking of the pores by the metal. In addition, metallic dispersion was also higher when the metal content was lower. Dye conversion was more than 95% for every catalyst showing no differences with the nickel content. A high degree of dye conversion was achieved. Wet air oxidation (WAO) and catalytic wet air oxidation (CWAO) processes have been proved to be extremely efficient in TOC removal for wastewaters. The CWAO process can be used to remove dyes from wastewater. Three different dyes were tested showing satisfactory results in all of them. TOC degradation and dye removal in the presence of the catalyst were effective. Also, the HTNi catalyst is very active for organic matter and toxicity removal in wastewaters.

Application of ozone based treatments of secondary effluents

The present work was aimed at studying the efficiency of ozone in oxidation processes, coliform inactivation and Disinfection Byproducts (DBPs) formation, associated with the potential of ozone to increase the Biodegradable Dissolved Organic Carbon (BDOC) in secondary effluent with applied ozone doses of 5.0, 10.0 and 15.0 mg/L for contact times of 2, 5 and 10 min. The wastewater used in this work was collected from the Bhagwanpur Sewage Treatment Plant, Varanasi, India. Results of this experiment showed that 10 mg O(3)/L O(3) for 5 min exposure was found most suitable dose for highest degradation of COD, TOC, UV(254), color, turbidity and total nitrogen parameters. The inactivation range of microbial biomass range was found in between 95% and 98%. Experiment revealed the fact that aldehydes and carboxylic acid formation were significantly related with the ozone dose and exposure time and ozone might enhance the treatment efficiency of secondary effluent treatment.

Frequency effects on the sonochemical degradation of chlorinated compounds

The effects of frequency in chlorobenzene, chloroform, and carbon tetrachloride have been experimentally investigated in this study. The irradiation frequencies were 35, 74, 170, 300 and 1000 kHz. The degradation rates of chlorobenzene, chloroform, and carbon tetrachloride were highest at 300 kHz. The results of between formation of hydrogen peroxide concentration and degradation of chlorinated compounds were not a coincidence. Methods of the sonochemical efficiency were needed to review. The concentration of total organic carbon was remained after 4 h of sonication. High power intensity, longer sonication time, addition of catalysts and combination of the AOP process, were needed for the degradation of TOC. The formation of chloride ion in aqueous solution was evident for the degradation of chlorinated compounds. However, the theoretical concentration of chloride ion was higher than the measured concentration. This means that the remaining chlorinated contaminants in each solution cannot complete dechlorination and some intermediated were produced.

Degradation of di-, tri-, tetra-, and pentachlorophenol mixtures in an aerobic biofilter

Chlorophenols are highly toxic xenobiotic compounds, normally found in the effluents of many industries. Due to the high toxicity of these compounds, it is difficult to treat effluent streams containing high concentrations of chlorophenols. The aim of this work is to demonstrate the capabilities of an aerobic submerged filter previously characterized in the degradation of phenol and chlorophenols in the treatment of highly toxic di-, tri-, tetra- and penta- chlorophenols mixtures (200 800 mgL -1 as total phenols concentration). It is shown that the system is capable of treating up to 600 mgL -1 of total chlorophenols with excellent reduction values, and biodegradation rates (BDRs) between 87 - 97%, and 34 - 157 mgL -1 day -1 , respectively (total organic carbon, TOC degradations up to 80%). In the case of the 800 mgL -1 , a strong inhibition due to the high toxicity of the mixture was observed. The system reduced the influent toxicity (EC50 or toxic units) by 48 - 76%, even when the initial toxicities of the mixtures were in the range of 40 - 358 toxic units (classified as very toxic). The kinetics of the phenol and TOC degradation were characterized through a first order kinetic expression. The values of TPho, TOCo, k1 and k2 are reported for the biodegradation of the total phenols and for the TOC, respectively. A system with powerful capabilities in the treatment of industrial streams, contaminated aquifers or accidentally contaminated municipal wastewaters containing high quantities of chlorophenols, is described.

Fenton's oxidation process for phenolic wastewater remediation and biodegradability enhancement

A mixture of six phenolic acids, corresponding to an initial TOC of 370 mgC/L, was studied by Fenton's peroxidation aiming to improve the biodegradability of agro-industrial wastewaters. Input operating variables including the concentration of pollutants, iron and hydrogen peroxide as well as the reaction time were used to assess the mineralization degree through a factorial experimental methodology. A TOC removal in the range of 15.0–58.8% was attained within the operational conditions used. A reduced model was achieved using the statistically important independent factors and interactions to predict TOC degradation. On the hydrogen peroxide injection methodology, the results showed that the continuous introduction of small volumes is advantageous when compared with one single addition of the overall volume at the zero reaction time with a mineralization improvement of 11%. The use of FeSO 4·7H 2O correspondent to a Fe 2+ load of 271 mg; [H 2O 2] = 488.0 mM, injected in twelve aliquots each 30 min during 6 h of reaction reached optimal efficiencies with the parent compounds (quantified by HPLC and the Folin–Ciocalteau method) quickly totally removed and TOC, COD and BOD 5 final values of 123 mgC/L, 180 mgO 2/L and 146 mgO 2/L, respectively. Toxicity assessment by Vibrio fischeri light inhibition revealed that Fenton's process reduces the effluent ecological impact related with the decomposition of the toxic phenolic acids. Indeed, EC 50 changed from 32.2% dilution to no-dilution needed. The analysis of BOD 5/COD ratio pointed out a high improvement of the treated wastewater biodegradability from 0.30 to 0.80 meaning that the application of Fenton's oxidation as a pre-treatment enables a further application of an efficient post-biological technology which was also confirmed by respirometry.

Fenton degradation of 4-chlorophenol contaminated water promoted by solar irradiation

The degradation of 4-chlorophenol (4-CP) contaminated water by Fenton process with or without solar irradiation assistance were investigated. It was found that the COD degradation and mineralization efficiency of 4-CP were more than 90% when a 30 min treatment of solar photo-Fenton oxidation process was applied and under an optimum [H 2O 2] 0/[Fe 2+] 0 ratio of 40, the COD degradation and mineralization efficiency increased 65% as compared to Fenton oxidation. Meanwhile, the AOS values increased from −0.33 to 2.13 in solar photo-Fenton process while no significant improvement for AOS values was found in Fenton process, implying a higher degree of oxidation for 4-CP in solar photo-Fenton process. In addition, increasing the intensity of solar irradiation seemed to be beneficial for treatment of 4-CP contaminated water. Formation of chloride ion as a result of mineralization of organically bounded chlorine was identified during the treatment of 4-CP solution. Near-stoichiometric accumulation of chlorine was observed during the degradation of 4-CP in both Fenton and solar photo-Fenton processes. However, accumulation rate of chloride ions were much faster in solar photo-Fenton process. The degradation of 4-CP was found to obey a pseudo-first-order reaction kinetics. As compared to Fenton process, the presence of solar light in photo-Fenton process increases the reaction rate by a factor of 6.5 and 15.8 for COD and TOC degradation, respectively. In other words, during the treatment of 4-CP contaminated water, solar photo-Fenton process possesses notably higher mineralization efficiency in a relatively short radiation time as compared to Fenton process, and could enhance the degradation treatment of refractory organic wastewater such as 4-CP in a cost-effective approach.

Heterogeneous catalytic wet peroxide oxidation systems for the treatment of an industrial pharmaceutical wastewater

The aim of this work was to assess the treatment of wastewater coming from a pharmaceutical plant through a continuous heterogeneous catalytic wet peroxide oxidation (CWPO) process using an Fe 2O 3/SBA-15 nanocomposite catalyst. This catalyst was preliminary tested in a batch stirred tank reactor (STR), to elucidate the influence of significant parameters on the oxidation system, such as temperature, initial oxidant concentration and initial pH of the reaction medium. In that case, a temperature of 80 °C using an initial oxidant concentration corresponding to twice the theoretical stoichiometric amount for complete carbon depletion and initial pH of ca. 3 allow TOC degradation of around 50% after 200 min of contact time. Thereafter, the powder catalyst was extruded with bentonite to prepare pellets that could be used in a fixed bed reactor (FBR). Results in the up-flow FBR indicate that the catalyst shows high activity in terms of TOC mineralization (ca. 60% under steady-state conditions), with an excellent use of the oxidant and high stability of the supported iron species. The activity of the catalyst is kept constant, at least, for 55 h of reaction. Furthermore, the BOD 5/COD ratio is increased from 0.20 to 0.30, whereas the average oxidation stage (AOS) changed from 0.70 to 2.35. These two parameters show a high oxidation degree of organic compounds in the outlet effluent, which enhances its biodegradability, and favours the possibility of a subsequent coupling with a conventional biological treatment.

Degradation of phenolic aqueous solutions by high frequency sono-Fenton systems (US–Fe2O3/SBA-15–H2O2)

The aim of this work is to establish the influence of different ultrasonic frequencies ranging from 20 to 1142kHz on the efficiency of the US/Fe2O3/SBA-15/H2O2 (sono-Fenton) system. The frequency of 584kHz has been established as the optimum ultrasonic irradiation for the degradation of aqueous phenol solutions by the sono-Fenton system and the effect of different variables, such as hydrogen peroxide concentration or catalyst loadings in the reaction was studied by factorial design of experiments. Catalyst loadings of 0.6g/L and hydrogen peroxide concentration, close to the stoichiometric amount, show high organic mineralization, accompanied by excellent catalyst stability in a wide range of concentrations of aqueous phenol solutions (0.625–10mM). Additionally, the catalyst can be easily recovered by filtration for reuse in subsequent reactions without appreciable loss of activity. The coupling of US (584kHz)/Fe–SBA-15/H2O2 at room temperature is revealed as a promising technique for wastewater treatment. Additionally, a new sono-Fenton variant, the so-called latent remediation has also been studied, using ultrasonic irradiation only as pretreatment for 15min in an attempt at reducing the cost of the degradation process. It has been observed that latent remediation provides TOC degradation of around 21% after 15min sonication followed by 6h silent reaction while the typical sono-Fenton reaction affords 29% TOC reduction after 6h sonication.

Biodegradability of chlorophenol wastewater enhanced by solar photo-Fenton process

The combination of solar irradiation and Fenton reagent have been used to enhance the biodegradability (BOD(5)/COD) of chlorophenol wastewater, including 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), and 2,4-dichlorophenol (2,4-DCP). Results showed that the solar photo-Fenton process improved significantly the biodegradability of chlorophenol wastewater. Basically, increasing initial H(2)O(2) dosage was much more beneficial for increasing biodegradability of wastewater than increasing initial Fe(2 + ) dosage. Among the conditions studied, the optimum condition of increasing biodegradability of chlorophenol wastewater was found with a [H(2)O(2)](0)/[Fe(2 + )](0)/[chlorophenol](0) ratio of 10.0/0.2/1.0, 10.0/0.3/1.0, and 10.0/0.2/1.0 for 2-CP, 4-CP, and 2,4-DCP, respectively. As a result, the value of BOD(5)/COD was increased from 0 for untreated solution up to 0.231, 0.248, and 0.193 for 2-CP, 4-CP, and 2,4-DCP, respectively with a 15-min treatment. Under the operation of optimum conditions, the oxidative state of chlorophenol wastewater could be easily controlled into a higher biodegradability stage. The COD and TOC degradation efficiency could be in excess of 90% on the whole as the preoxidized chlorophenol solution was treated by a following batch-type biological unit. In the meanwhile, the microtoxicity of wastewater reduced more than 95%.

Photodegradation of C.I. Reactive Red 2 in UV/TiO2-based systems: Effects of ultrasound irradiation

This investigation elucidated the decolorization of C.I. Reactive Red 2 (RR2) in US/TiO(2), UV/TiO(2) and UV/US/TiO(2) systems and evaluated the effect of ultrasound (US) irradiation in photocatalysis. The effects of RR2 concentration, temperature and the addition of NaCl, Na(2)S(2)O(8) and radical scavenger were determined. The decolorization reactions obeyed the pseudo-first-order kinetics in all tested systems. In US-related systems, the decolorization rate of RR2 declines as RR2 concentration increases. At pH 7, the decolorization rates followed the order UV/US/TiO(2) (0.94 h(-1))>UV/TiO(2) (0.85 h(-1))>US/TiO(2) (0.25 h(-1)). The promotion efficiencies of adding NaCl in US/TiO(2), UV/TiO(2) and UV/US/TiO(2) systems were 16%, 18% and 29%, respectively. The decolorization rate increased with the temperature; additionally, the decolorization rate in UV/US/TiO(2)/Na(2)S(2)O(8) exceeded that in UV/US/TiO(2). The inhibition of RR2 decolorization by adding 1-butanol reveals that the primary decolorization pathway involves hydroxyl radicals, and that direct oxidation by photogenerated holes is probably important in the UV/TiO(2)-based system. After 120 min of the reaction, the TOC degradation efficiencies of UV/TiO(2) and UV/US/TiO(2) systems were 47% and 63%, respectively.

Preparation of composite zeolite membrane separator/contactor for ozone water treatment

A composite membrane was prepared by coating high surface area γ-Al2O3 on the porous ceramic support of the ZSM-5 membrane. A thin layer of γ-Al2O3 was coated on the surface of the individual ceramic particles to increase the contact surface by about 50m2. Ozone treatment of phthalate contaminated water showed that ozonization with traditional sparger in a batch reactor yielded a 1.1% decrease in TOC, and simply replacing the sparger with a membrane distributor gave a 20% TOC removal. Providing a membrane contactor increases this value to 25%, while simultaneous membrane pervaporation of water resulted in 40% TOC degradation. This shows that it is possible to achieved enhanced ozone water treatment from a compact membrane reactor unit that uses the combined function of membrane as distributor, contactor and separator.

Photocatalytic oxidation of VX-simulation substance

Experimental studies of photocatalytic oxidation (PCO) of VX-gas simulation substance cysteamine-S-phosphate sodium salt (NaHPO3S-CH2-CH2-NH2, CPSS) at various initial concentrations and pH were undertaken. PCO ultimately resulted in complete mineralisation of CPSS. The PCO byproducts of CPSS include acetate, oxalate and trace amounts of formate ions. The formation rates of acetate and phosphate were equal to the rate of degradation of CPSS, which indicates easy breakage of P-S, C-S and C-N bonds. Sulphate was formed more slowly due to stepwise oxidation of reduced sulphur. Amino group, generally transformed to ammonia, was partially oxidised to nitrite and nitrate in alkaline media. The fastest mineralisation in terms of both TOC degradation and phosphate formation was observed in neutral media. Under neutral media conditions, the PCO rate increased linearly with the CPSS concentration increase. The maximum efficiency by TOC degradation was observed as large as 77 mg per Wh of incident UV flux with quantum efficiency 3.8%.