Improvement of COD and color removal from UASB treated poultry manure wastewater using Fenton's oxidation

The applicability of Fenton's oxidation as an advanced treatment for chemical oxygen demand (COD) and color removal from anaerobically treated poultry manure wastewater was investigated. The raw poultry manure wastewater, having a pH of 7.30 (+/-0.2) and a total COD of 12,100 (+/-910) mg/L was first treated in a 15.7 L of pilot-scale up-flow anaerobic sludge blanket (UASB) reactor. The UASB reactor was operated for 72 days at mesophilic conditions (32+/-2 degrees C) in a temperature-controlled environment with three different hydraulic retention times (HRT) of 15.7, 12 and 8.0 days, and with organic loading rates (OLR) between 0.650 and 1.783 kg COD/(m3day). Under 8.0 days of HRT, the UASB process showed a remarkable performance on total COD removal with a treatment efficiency of 90.7% at the day of 63. The anaerobically treated poultry manure wastewater was further treated by Fenton's oxidation process using Fe2+ and H2O2 solutions. Batch tests were conducted on the UASB effluent samples to determine the optimum operating conditions including initial pH, effects of H2O2 and Fe2+ dosages, and the ratio of H2O2/Fe2+. Preliminary tests conducted with the dosages of 100 mg Fe2+/L and 200 mg H2O2/L showed that optimal initial pH was 3.0 for both COD and color removal from the UASB effluent. On the basis of preliminary test results, effects of increasing dosages of Fe2+ and H2O2 were investigated. Under the condition of 400 mg Fe2+/L and 200 mg H2O2/L, removal efficiencies of residual COD and color were 88.7% and 80.9%, respectively. Under the subsequent condition of 100 mg Fe2+/L and 1200 mg H2O2/L, 95% of residual COD and 95.7% of residual color were removed from the UASB effluent. Results of this experimental study obviously indicated that nearly 99.3% of COD of raw poultry manure wastewater could be effectively removed by a UASB process followed by Fenton's oxidation technology used as a post-treatment unit.     

A statistical experiment design approach for advanced oxidation of Direct Red azo-dye by photo-Fenton treatment

Advanced oxidation of an azo-dye, Direct Red 28 (DR 28) by photo-Fenton treatment was investigated in batch experiments using Box-Behnken statistical experiment design and the response surface analysis. Dyestuff (DR 28), H(2)O(2) and Fe(II) concentrations were selected as independent variables in Box-Behnken design while color and total organic carbon (TOC) removal (mineralization) were considered as the response functions. Color removal increased with increasing H(2)O(2) and Fe(II) concentrations up to a certain level. High concentrations of H(2)O(2) and Fe(II) adversely affected the color and TOC removals due to hydroxyl radical scavenging effects of high oxidant and catalyst concentrations. Both H(2)O(2) and Fe(II) concentration had profound effects on decolorization. Percent color removal was higher than TOC removal indicating formation of colorless organic intermediates. Complete color removal was achieved within 5min while complete mineralization took nearly 15min. The optimal reagent doses varied depending on the initial dyestuff dose. For the highest dyestuff concentration tested, the optimal H(2)O(2)/Fe(II)/dyestuff ratio resulting in the maximum color removal (100%) was predicted to be 715/71/250 (mgL(-1)), while this ratio was 1550/96.5/250 for maximum mineralization (97.5%).     

Optimization of decolorization of methylene blue by lignin peroxidase enzyme produced from sewage sludge with Phanerocheate chrysosporium

Optimization of decolorization of methylene blue (MB) dye by lignin peroxidase (LiP) enzyme produced by white-rot fungus Phanerochaete chrysosporium using sewage treatment plant (STP) sludge as a major substrate was carried out in the laboratory. Optimization by the one-factor-at-a-time (OFAT) and statistical approach was carried out to determine the process conditions on optimum decolorization of MB dye using LiP enzyme in static mode. The OFAT method indicated that the optimum conditions for decolorization of MB dye (removal: 14-40%) was at temperature 55 degrees C, pH 5.0 with hydrogen peroxide (H(2)O(2)) concentration 4.0mM, MB dye concentration 20mg/L and LiP activity 0.487U/ml. The addition of veratryl alcohol to the reaction mixtures did not contribute any further increases in decolorization. The initial concentration of MB and the activity of LiP enzyme were further optimized using response surface methodology (RSM). The contour and surface plots suggested that the optimum initial concentration of MB and LiP activity predicted were 15mg/L and 0.687U/ml, respectively for the removal of 65%. The validation of the model showed that the decolorization process gave the higher removal of 90% in agitation mode compared to the static mode with 65% for 60min of incubation time by LiP enzyme.     

Landfill leachate treatment with a novel process: anaerobic ammonium oxidation (Anammox) combined with soil infiltration system

A novel combined process was proposed to treat municipal landfill leachate with high concentrations of ammonium and organics. This process consisted of a partial nitritation reactor (PNR), an anaerobic ammonium oxidation (Anammox) reactor (AR) and two underground soil infiltration systems (USIS-1 and USIS-2). Based on the optimum operating conditions obtained from batch tests of individual unit, the combined process was continuously operated on a bench scale for 166 days. Partial nitritation was performed in a fixed bio-film reactor (PNR, working volume=12 L). Ammonium nitrogen-loading rate (Nv) and DO were combined to monitor partial nitritation, and at T=30+/-1 degrees C, Nv=0.27-1.2 kg/(m3.d), DO=0.8-2.3 mg/L, the ratios of nitrite nitrogen (NO2--N) to ammonium nitrogen (NH4+-N) were successfully kept close to 1.0-1.3 in the effluent. Nitrate nitrogen (NO3--N) less than 43 mg/L was observed. The effluent of PNR was ideally suited as influent of AR. Sixty-nine percent CODcr from the raw leachate was degraded in the PNR. Anammox was carried out in a fixed bio-film reactor (AR, working volume=36 L). At T=30+/-1 degrees C, Nv=0.06-0.11 kg/(m3.d), about 60% NH4+-N and 64% NO2--N in the influent of AR were simultaneously removed. Inhibition of high-strength NO2--N (up to 1011 mg/L) should be responsible for the low removal rate of nitrogen. About 35% aquatic humic substance (AHS) was degraded in the AR. With the same working volume (200 L), USIS-1 and USIS-2 were alternately performed to treat the effluent from AR at one cycle of about 30 days. At hydraulic loading rate (HLR)=0.02-0.04 m3/m3.d, pollutant loading rates (PLR)=NH4+-N相似文献   

Fenton's peroxidation and coagulation processes for the treatment of combined industrial and domestic wastewater

As a consequence of the population growth, major efforts have been made by the Egyptian government to construct new industrial areas. Tenth of Ramadan City is one of the most important industrial cities in Egypt. The wastewater generated from various industrial activities was highly contaminated with organic matters as indicated by COD (1750-3323 mg/L), TSS (900-3000 mg/L) and oil and grease (13.2-95.5 mg/L). All overall appraisals of the analytical data from the industrial wastewater indicate that pretreatment is required for all industrial sectors to achieve compliance with the Egyptian Environmental law which requires effective pretreatment of industrial wastewater prior to its discharge into public sewers. Treatability studies via conventional and Fenton processes have been investigated. The efficiency of conventional treatment methods led to 63% COD and 44% color removal by using FeCl(3) as coagulant. Various coagulant aids and powdered activated carbon (PAC) were added to 400mg/L FeCl(3) in order to enhance the removal of color. It was found that polyacrylamide polymer, bentonite and PAC increased the efficiency of the treatments where the color removal increased to 79%, by cationic polymer, 73% by anionic polymer, 84.5% by bentonite and 95% for 0.4 g/L PAC. Fenton process was investigated which under the operating conditions (pH 3.0+/-0.2, Fe(2+) dose=400 mg/L and H(2)O(2)=550 mg/L), color removal up to 100% and more than 90% of COD removal were achieved.     

The decolorization and mineralization of acid orange 6 azo dye in aqueous solution by advanced oxidation processes: a comparative study

The comparison of different advanced oxidation processes (AOPs), i.e. ultraviolet (UV)/TiO(2), O(3), O(3)/UV, O(3)/UV/TiO(2), Fenton and electrocoagulation (EC), is of interest to determine the best removal performance for the destruction of the target compound in an Acid Orange 6 (AO6) solution, exploring the most efficient experimental conditions as well; on the other hand, the results may provide baseline information of the combination of different AOPs in treating industrial wastewater. The following conclusions can be drawn: (1) in the effects of individual and combined ozonation and photocatalytic UV irradiation, both O(3)/UV and O(3)/UV/TiO(2) processes exhibit remarkable TOC removal capability that can achieve a 65% removal efficiency at pH 7 and O(3) dose=45mg/L; (2) the optimum pH and ratio of [H(2)O(2)]/[Fe(2+)] found for the Fenton process, are pH 4 and [H(2)O(2)]/[Fe(2+)]=6.58. The optimum [H(2)O(2)] and [Fe(2+)] under the same HF value are 58.82 and 8.93mM, respectively; (3) the optimum applied voltage found in the EC experiment is 80V, and the initial pH will affect the AO6 and TOC removal rates in that acidic conditions may be favorable for a higher removal rate; (4) the AO6 decolorization rate ranking was obtained in the order of O(3)相似文献   

Removal and degradation pathway study of sulfasalazine with Fenton-like reaction

The Fenton-like degradation of sulfasalazine solution is studied in this work. The effects of reaction parameters such as Fe(3+) concentration, initial H(2)O(2) dosage and the reaction temperature are evaluated. For sulfasalazine of 100mg/L, the removal of sulfasalazine, chemical oxygen demand (COD) and total organic carbon (TOC) reached 99.5%, 84.2% and 41% in 60 min with 0.20mM Fe(3+) and 16 mM H(2)O(2) at 35°C, respectively. The complexed Fe(3+) presents a reaction constant of 0.062 min(-1)mM(-1) while that of free Fe(3+) is 2.526 min(-1)mM(-1) for sulfasalazine degradation. LC-MS technology was used to analysis the possible degradation intermediates. The degradation of sulfasalazine principally begins with the attack of hydroxyl radical on the azo-group as well as the sulfanilamido group. Both intramolecular rearrangement and bimolecular reaction occur simultaneously after the hydroxyl radical attack. Further attack of the active oxidative species results in the cleavage of the aromatic rings and the production of CO(2). The degradation of industrial sulfasalazine wastewater with a COD of 3425 mg/L has also been achieved by Fenton reaction with different dosage of H(2)O(2). Relatively better removal efficiency is observed at moderate Fe/H(2)O(2) molar ratio from 1/5 to 2/5 for industrial sulfasalazine wastewater treatment.     

Removal of organic carbon from wastepaper pulp effluent by lab-scale solar photo-Fenton process

The bleaching wastewater effluent from a pulp and paper mill (located in Tianjin, China) was treated with solar photo-Fenton process in a lab-scale reactor (22 cm x 15 cm thermostatic dish). The mill used wastepaper as raw material and the effluent contained 332 mgL(-1) of total organic carbon (TOC) and 1286 mg L(-1) of COD. The treatment involved a constant intensity of irradiation (0.2 kW/m(2)) with a solar simulator of 250 W xenon lamp and various conditions of pH, temperature, and initial concentrations of H(2)O(2) and Fe(II). The better treatment conditions were searched for in the ranges of initial Fe(II) concentration from 31 to 310 mgL(-1) (initial pH 3.0, 30 degrees C), initial H(2)O(2) concentration from 0.5 to 3 Dth (1 Dth=1883 mg L(-1) for TOC mineralization) (initial pH 3.0, 30 degrees C), initial pH from 2.0 to 6.0 (1 and 2 Dth, 10:1 of H(2)O(2)/Fe(II), 30 degrees C), and temperature from 30 to 50 degrees C (1 Dth, 10:1 of H(2)O(2)/Fe(II), initial pH 2.8). TOC removal generally showed the initial fast increase stage within the first sampling time of 15 min, followed by the gradual increase stage in the remaining sampling time of 180 min experimental time course. The highest percentage of TOC removal in the first stage was about 60% when the initial pH was either 2.8 (H(2)O(2)=1 Dth, ratio=10:1, temperature=30-50 degrees C) or 3.5 (H(2)O(2)=2 Dth, ratio=10:1, temperature=30 degrees C). Also under the latter condition, the value reached 82% at 120 min and was projected to reach 94% at 180 min. According to the positive effect of temperature increase on TOC removal observed in this experiment, further increase above these maximum values is possible if the temperature of the above condition were increased from 30 to 40 degrees C or 50 degrees C. Furthermore, under most of the treatment conditions, the TOC removal reached or was projected to reach over 60% toward the end of the experiments. The result indicated that the solar photo-Fenton process has a potential to effectively remove TOC from the wastepaper pulp effluent on a large scale.     

The decolorization of C.I. Reactive Black 5 in aqueous solution by electrocoagulation using sacrificial iron electrodes

The removal of color from synthetic wastewater containing Reactive Black 5 was experimentally investigated using direct current electrocoagulation at iron electrodes. The effects of operational parameters such as current density, initial pH, electrolysis time, initial dye concentration and solution conductivity on color removal efficiency were investigated in this study. The optimum operating range for each of these operating variables was experimentally determined. The experimental results show that the color of Reactive Black 5 in the aqueous phase was removed effectively. Under the conditions of an initial dye concentration of 100 mg L(-1), initial pH of 5, current density of 4.575 mAcm(-2), salt concentration of 3000 mg L(-1), temperature of 20 degrees C, and interelectrode distance of 2.5 cm, the color removal efficiency reached 98.8%. Electrical energy consumption in the above conditions for the decolorization of the dye solution containing Reactive Black 5 was 4.96 kWh/kg dye. Results show that the first-order rate equation provides the best correlation for the decolorization rate of Reactive Black 5.     

Characterization and photo-Fenton treatment of used tires leachate

In this study the leachates derived from used tires were firstly characterized by means of the evaluation of their organic matter content. The leachate from tire powder presented a COD value of 508 mg O(2) l(-1) and a TOC of 214 mg Cl (-1). The main identified organic substances were constituents of the rubber structure: benzothiazole derivatives, phthalates, phenolic derivatives, hydrocarbons and fatty acids. The application of photo-Fenton treatment was investigated in order to obtain the maximum organic matter removal. When a solar chamber as light source was used (light intensity=500 Wm(-2)), the best operational conditions were the following: [H(2)O(2)]=3703 mg l(-1), [Fe(2+)]=92.1 mg l(-1), initial pH 2.7-3.0, reaction time=100 min. After the photo-Fenton treatment at optimum conditions, the reached COD and TOC reduction was 64% and 48%, respectively. The main initial organic substances were eliminated after the reaction and no significant by-products were identified. A complementary treatment consisted of coagulation-flocculation carried out with FeCl(3) x 6H(2)O at pH 12 produced a maximum organic matter removal of 43% as COD and 39% as TOC. A combination of photo-Fenton followed by coagulation-flocculation enhanced the organic matter removal: a reduction of 77% of COD and 64% of TOC was attained.     

Decolorization of alkaline TNT hydrolysis effluents using UV/H(2)O(2)

Effects of H(2)O(2) dosage (0, 10, 50, 100 and 300 mg/l), reaction pH (11.9, 6.5 and 2.5) and initial color intensity (85, 80 and 60 color unit) on decolorization of alkaline 2,4,6-trinitrotoluene (TNT) hydrolysis effluents were investigated at a fixed UV strength (40 W/m(2)). Results indicated that UV/H(2)O(2) oxidation could efficiently achieve decolorization and further mineralization. Pseudo first-order decolorization rate constants, k, ranged between 2.9 and 5.4 h(-1) with higher values for lower H(2)O(2) dosage (i.e., 10 mg/l H(2)O(2)) when the decolorization occurred at the reaction pH of 11.9, whereas a faster decolorization was achieved with increase in H(2)O(2) dosage at both pH 6.5 and 2.5, resulting in the values of k as fast as 15.4 and 26.6 h(-1) with 300 mg/l H(2)O(2) at pH 6.5 and 2.5, respectively. Difference in decolorization rates was attributed to the reaction pH rather than to the initial color intensity, resulting from the scavenging of hydroxyl radical by carbonate ion. About 40% of spontaneous mineralization was achieved with addition of 10 mg/l H(2)O(2) at pH 6.5. Efficient decolorization and extension of H(2)O(2) longevity were observed at pH 6.5 conditions. It is recommended that the colored effluents from alkaline TNT hydrolysis be neutralized prior to a decolorization step.     

Pre-treatment of penicillin formulation effluent by advanced oxidation processes

A variety of advanced oxidation processes (AOPs; O3/OH-, H2O2/UV, Fe2+/H2O2, Fe3+/H2O2, Fe2+/H2O2/UV and Fe3+/H2O2/UV) have been applied for the oxidative pre-treatment of real penicillin formulation effluent (average COD0 = 1395 mg/L; TOC0 = 920 mg/L; BOD(5,0) approximately 0 mg/L). For the ozonation process the primary involvement of free radical species such as OH* in the oxidative reaction could be demonstrated via inspection of ozone absorption rates. Alkaline ozonation and the photo-Fenton's reagents both appeared to be the most promising AOPs in terms of COD (49-66%) and TOC (42-52%) abatement rates, whereas the BOD5 of the originally non-biodegradable effluent could only be improved to a value of 100 mg/L with O3/pH = 3] treatment (BOD5/COD, f = 0.08). Evaluation on COD and TOC removal rates per applied active oxidant (AOx) and oxidant (Ox) on a molar basis revealed that alkaline ozonation and particularly the UV-light assisted Fenton processes enabling good oxidation yields (1-2 mol COD and TOC removal per AOx and Ox) by far outweighed the other studied AOPs. Separate experimental studies conducted with the penicillin active substance amoxicillin trihydrate indicated that the aqueous antibiotic substance can be completely eliminated after 40 min advanced oxidation applying photo-Fenton's reagent (pH = 3; Fe(2+):H2O2 molar ratio = 1:20) and alkaline ozonation (at pH = 11.5), respectively.     

Photodegradation of Reactive Black 5, Direct Red 28 and Direct Yellow 12 using UV, UV/H(2)O(2) and UV/H(2)O(2)/Fe(2+): a comparative study

The photodegradation of three commercially available dyestuffs (C.I. Reactive Black 5, C.I. RB5, C.I. Direct Yellow 12, C.I. DY12, and C.I. Direct Red 28, C.I. DR28) by UV, UV/H(2)O(2) and UV/H(2)O(2)/Fe(II) processes was investigated in a laboratory-scale batch photoreactor equipped with an 16W immersed-type low-pressure mercury vapour lamp. The experimental results were assessed in terms of absorbance and total organic carbon (TOC) reduction. The initial concentration was kept constant at 100 mg l(-1) for all dyes. Initial results showed that, color removal efficiencies by UV or H(2)O(2) alone were negligible for all dyes. Almost complete disappearance of C.I. RB5 (99%) and DY12 (98%) in UV/H(2)O(2) process was possible to achieve after 60 min of irradiation. The maximum color removal efficiency of C.I. DR28 after 60 min of irradiation, however, was only 40% and reached a maximum value of 70% after 120 min of irradiation. Corresponding mineralization efficiencies were 50, 55 and 7-12%, respectively. The addition of Fe(II) to the system, so-called the photo-Fenton process, greatly enhanced the color removal, the efficiencies being 98, 88 and 85% for C.I. RB5, C.I. DY12 and C.I. DR28 only after 5 min of irradiation. Corresponding mineralization efficiencies were 98% for 45 min irradiation, 100% for 60 min irradiation and 98% for 90 min irradiation, respectively. However, marginal benefit was less significant in the higher range of both H(2)O(2) and Fe(II). Furthermore, decreases in both decolorization and mineralization were observed at higher concentrations of oxidant and catalyst due to the scavenging effect of excess H(2)O(2) and OH radicals. The degradation of all dyes was found to follow first-order reaction kinetics.     

Oxidation of various reactive dyes with in situ electro-generated active chlorine for textile dyeing industry wastewater treatment

The present investigation revealed that all the reactive dyes were degraded in chlorine mediated electrochemical oxidation. Titanium based dimensionally stable anode (DSA) was used for in situ generation of chlorine in the dye solution. All classes of reactive dyes (100 mg/L) showed a complete color removal at a supporting electrolyte concentration of 1.5 g/L NaCl and 36.1 mA/cm(2) current density. The chemical oxygen demand (COD) and total organic carbon (TOC) removals were from 39.5 to 82.8% and from 11.3 to 44.7%, respectively, for different reactive dyes. It can be concluded in general that the triazine containing higher molecular weight diazo compounds takes more time for complete de-colorization than the mono azo or anthraquinone containing dye compounds. The degradation rate of mixed dye compounds was affected by reaction temperature, current density, NaCl concentration and initial dye concentration. However, the initial pH of the dye solution ranging from 4.3 to 9.4 did not show significant effect on de-colorization. A complete color removal with 73.5% COD and 32.8% TOC removals were obtained for mixed reactive dyes (200 mg/L) at the end of 120 min of electrolysis under the optimum operating conditions of 4 g/L NaCl concentration and 72.2 mA/cm(2) current density.     

Use of advanced oxidation processes to improve the biodegradability of mature landfill leachates

Two advanced oxidative processes (Fe2+/H2O2/UV and H2O2/UV systems) were used for the pre-treatment of mature landfill leachate with the objective of improving its overall biodegradability, evaluated in terms of BOD5/COD ratio, up to a value compatible with biological treatment. At optimized experimental conditions (2000 mgL(-1) of H2O2 and 10 mgL(-1) of Fe2+ for the photo-Fenton system, and 3000 mgL(-1) of H2O2 for the H2O2/UV system), both methods showed suitability for partial removal of chemical oxygen demand (COD), total organic carbon (TOC) and color. The biodegradability was significantly improved (BOD5/COD from 0.13 to 0.37 or 0.42) which allowed an almost total removal of COD and color by a sequential activated sludge process. In addition, gel permeation chromatography (GPC) has showed a substantial agreement on the cleavage of large organic compound into smaller ones.     

Application of the central composite design and response surface methodology to the advanced treatment of olive oil processing wastewater using Fenton's peroxidation

The central composite design (CCD) technique was used to study the effect of the Fenton's peroxidation on the removal of organic pollutants from olive oil mill wastewater (OMW). The ratio of hydrogen peroxide-to-Fe(II) (x1) was between 1.67 and 8.33. Fe(II) concentration was constant at 0.03 M while the H2O2 concentration was set at three levels: 0.05, 0.15 and 0.25 M. Based on the molarity ratio, the selected ratio were in the low range of Fe(II)-to-H2O2 ratio (<1). While based on the wt/wt ratio, the tested Fe(II)-to-H2O2 ratios were in the range of < or =1:5. pH (x2) was between 3 and 5. The concentration of OMW (x3) was varied between 40 and 100%. The influence of these three independent variables on the four dependent variables, i.e. COD, total phenolics (TP), color and aromaticity removal was evaluated using a second-order polynomial multiple regression model. Analysis of variance (ANOVA) showed a high coefficient of determination (R2) value of 0.902-0.998, thus ensuring a satisfactory adjustment of the second-order regression model with the experimental data. H2O2-to-Fe(II) ratio had significant effect on all the four dependent variables. The positive sign for the regression coefficient of this regressor variable indicated that the level of the pollutant removal increased with the increased levels of factor x1 from 1.67 to 8.33 and this effect was the most pronounced for TP removal. pH had also significant effect on the pollutant removal and the effect was the most noticeable for TP reduction. The negative coefficient of this variable (pH) indicated that level of the pollutant removal decreased as the pH increased from 3 to 5. The negative coefficient of the interaction between variable x1 and x2 indicated that a simultaneous increase in H2O2-to-Fe(II) ratio with decrease in the pH of the reaction led to an increase in the COD, TP and color removal. Quadratic models were predicted for the response variable, i.e. pollutant removal, and the maximum model-predicted removals were 56, 100, 33 and 32% for COD, TP, color and aromaticity, respectively. Optimum conditions for this wastewater treatment was obtained based on the performance of the Fenton's peroxidation in the experiment where the H2O2-to-Fe(II) ratio was at its high level (8.33) and the pH and OMW concentration were 4 and 70%, respectively.     

Use of Fenton oxidation to improve the biodegradability of a pharmaceutical wastewater

The applicability of Fenton's oxidation to improve the biodegradability of a pharmaceutical wastewater to be treated biologically was investigated. The wastewater was originated from a factory producing a variety of pharmaceutical chemicals. Treatability studies were conducted under laboratory conditions with all chemicals (having COD varying from 900 to 7000 mg/L) produced in the factory in order to determine the operational conditions to utilize in the full-scale treatment plant. Optimum pH was determined as 3.5 and 7.0 for the first (oxidation) and second stage (coagulation) of the Fenton process, respectively. For all chemicals, COD removal efficiency was highest when the molar ratio of H(2)O(2)/Fe(2+) was 150-250. At H(2)O(2)/Fe(2+) ratio of 155, 0.3M H(2)O(2) and 0.002 M Fe(2+), provided 45-65% COD removal. The wastewater treatment plant that employs Fenton oxidation followed by aerobic degradation in sequencing batch reactors (SBR), built after these treatability studies provided an overall COD removal efficiency of 98%, and compliance with the discharge limits. The efficiency of the Fenton's oxidation was around 45-50% and the efficiency in the SBR system which has two reactors each having a volume of 8m(3) and operated with a total cycle time of 1 day, was around 98%, regarding the COD removal.     

Electrochemical oxidation of phenol in a parallel plate reactor using ruthenium mixed metal oxide electrode

In this study, electrochemical oxidation of phenol was carried out in a parallel plate reactor using ruthenium mixed metal oxide electrode. The effects of initial pH, temperature, supporting electrolyte concentration, current density, flow rate and initial phenol concentration on the removal efficiency were investigated. Model wastewater prepared with distilled water and phenol, was recirculated to the electrochemical reactor by a peristaltic pump. Sodium sulfate was used as supporting electrolyte. The Microtox bioassay was also used to measure the toxicity of the model wastewater during the study. As a result of the study, removal efficiency of 99.7% and 88.9% were achieved for the initial phenol concentration of 200 mg/L and chemical oxygen demand (COD) of 480 mg/L, respectively. In the same study, specific energy consumption of 1.88 k Wh/g phenol removed and, mass transfer coefficient of 8.62 x 10(-6)m/s were reached at the current density of 15 mA/cm(2). Electrochemical oxygen demand (EOD), which can be defined as the amount of electrochemically formed oxygen used for the oxidation of organic pollutants, was 2.13 g O(2)/g phenol. Electrochemical oxidation of petroleum refinery wastewater was also studied at the optimum experimental conditions obtained. Phenol removal of 94.5% and COD removal of 70.1% were reached at the current density of 20 mA/cm(2) for the petroleum refinery wastewater.     

Preparation of adsorbents made from sewage sludges for adsorption of organic materials from wastewater

The carbon-bearing adsorbents were prepared from biochemical and surplus sludges by physical activation and chemical activation. The results indicated that the adsorbents made by way of chemical activation were better, with the optimum activator being complex of ZnCl(2) and H(2)SO(4). Moreover, the optimum preparation conditions were concentration of two activators 5 mol/L (the ratio of ZnCl(2) and H(2)SO(4) was 2:1), at the activating temperature of 550 degrees C, in the proportion of solid to liquid 1:2.5, in a period of 2h. Contrasting the active carbon, the carbon-bearing adsorbents were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS), scanning electron microscope (SEM), BET and BJH. By application of those adsorbents to treatment of wastewater of urban, the treatment effect of the carbon-bearing adsorbents were better than the active carbon. On the condition that the concentration was 0.5%, the COD, P and chromaticity color removal rates of carbon-bearing adsorbent made from the biochemical sludge of sewage were higher, which were 79.1, 98.3 and 87.5%, respectively, and the dynamic adsorption capacity was 47.8 mg/g.     

Decolorization kinetics of Procion H-exl dyes from textile dyeing using Fenton-like reactions

The decolorization kinetics of three commercially used Procion H-exl dyes was studied using a Fenton-like reagent. The effect of the major system parameters (pH, concentration of H(2)O(2) and Fe(3+) and initial dye concentration) on the kinetics was determined. For comparison, the effect of the use of UV irradiated Fenton-like reagent and of Fenton reagent on the kinetics was also examined. In addition, mineralization rates and the biodegradability improvement as well as the effect of the addition of Cl(-), CO(3)(2-) or HCO(3)(-) on the decolorization rates was studied. The reactions were carried out in a 300 ml stirred cylindrical reactor with the capability of UV irradiation. The dye half-life time goes through a minimum with respect to the solution pH between 3 and 4. It also exhibits a broad minimum with respect to Fe(3+) and H(2)O(2) at molar ratios of H(2)O(2)/Fe(3+) from about 100 to 10. The addition of CO(3)(2-) and HCO(3)(-) substantially reduces the decolorization rates, while this effect is significantly less pronounced with Cl(-). At an optimum range of parameters, the mineralization rate (TOC reduction) is very slow for the Fenton-like process (TOC decrease from an initial 49.5 to 41.1 mg/l after 30 min and to only 35.2 mg/l after 600 min), but it increases significantly for the photo-Fenton-like process (to TOC values of 39.7 and 11.4 mg/l, respectively). The biodegradability, as expressed by the BOD/COD ratio, increases significantly from an initial value of 0.11-0.55 for the Fenton-like and to 0.72 for the photo-Fenton-like processes.