Catalytic Ozonation of Phenolic Wastewater: Identification and Toxicity of Intermediates

A new strategy in catalytic ozonation removal method for degradation and detoxification of phenol from industrial wastewater was investigated. Magnetic carbon nanocomposite, as a novel catalyst, was synthesized and then used in the catalytic ozonation process (COP) and the effects of operational conditions such as initial pH, reaction time, and initial concentration of phenol on the degradation efficiency and the toxicity assay have been investigated. The results showed that the highest catalytic potential was achieved at optimal neutral pH and the removal efficiency of phenol and COD is 98.5% and 69.8%, respectively. First-order modeling demonstrated that the reactions were dependent on the initial concentration of phenol, with kinetic constants varying from 0.038 min−1 ([phenol]o = 1500mg/L) to 1.273 min−1 ([phenol]o = 50mg/L). Bioassay analysis showed that phenol was highly toxic to Daphnia magna (LC50 96 h = 5.6mg/L). Comparison of toxicity units (TU) of row wastewater (36.01) and the treated effluent showed that TU value, after slightly increasing in the first steps of ozonation for construction of more toxic intermediates, severely reduced at the end of reaction (2.23).Thus, COP was able to effectively remove the toxicity of intermediates which were formed during the chemical oxidation of phenolic wastewaters

Equilibrium and kinetics studies of Direct blue 71 adsorption from aqueous solutions using modified zeolite

This study deals with the application of Iranian zeolite as a low cost adsorbent for the removal of the Direct blue 71 (DB 71) from colored solution. Important parameters including equilibrium and contact time, initial dye concentration, effect of pH, and zeolite dosage were evaluated. Maximum dye removal was obtained at about 99.8% for 25 mg/L at 120 min of equilibrium. Higher adsorption efficiency of direct dye was obtained at higher dose and acidic pH. To analyze the adsorption equilibrium and kinetic, Langmuir, Freundlich, and Temkin isotherms as well as four kinetic models encompassing pseudo first-order, pseudo second-order, intraparticle diffusion, and Elovich were evaluated. The Langmuir isotherm (R2 = 0.995) and pseudo second-order models, gave the best fit to equilibrium experimental data. In Langmuir analysis, the maximum adsorption capacity (qm) by 13.66 mg/g was determined. Finally, the characteristics of zeolite including both natural and modified, such as compositions, surface morphology by X-ray diffraction technique (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM) were obtained. According to XRF analysis, it was demonstrated that Al2O3 and SiO2 are the most part of natural and modified zeolite. Furthermore, the clinoptilolite was determined as the significant crystalloid phase by XRD pattern

RESIDUAL METAL CONCENTRATIONS IN ENHANCED COAGULATION WITH FERRIC CHLORIDE AND ALUM FOR TOC REMOVAL

Chemical coagulation with metallic salts has traditionally been used in water treatment for turbidity removal. However, coagulation is also capable of some degree of natural organic matter (NOM) removal, with NOM functioning as a precursor to disinfection by-products (DBPs) formation. Enhanced coagulation is thus introduced to most water utilities treating surface water. Jar-test experiments were conducted to compare the effectiveness of alum and ferric chloride in removing DBPs precursors from eight synthetic water samples, each representing a different element of the USEPA’s 3×3 enhanced coagulation matrix, and the residual metal (aluminum/iron) concentration in the treated water was assessed. Coagulant type influenced the removal of total organic carbon (TOC) and which was enhanced with increasing coagulant dose. For all the treated samples coagulation with ferric chloride proved to be more effective than alum at similar doses and the mean values of treatment efficiencies were 51% and 32%, respectively. Ferric chloride was therefore considered the better chemical for enhancing the coagulation process. The results of residual metal concentration measurements in treated water showed that iron and aluminum concentrations had been increased as expected but the quality of water concerning the residual metal deteriorated much more in cases of under-dosing. Despite expecting high residual Al and Fe concentrations under enhanced coagulation, metal concentrations were frequently remained low and were not increased appreciably

RESIDUAL METAL CONCENTRATIONS IN ENHANCED COAGULATION WITH FERRIC CHLORIDE AND ALUM FOR TOC REMOVAL

Chemical coagulation with metallic salts has traditionally been used in water treatment for turbidity removal. However, coagulation is also capable of some degree of natural organic matter (NOM) removal, with NOM functioning as a precursor to disinfection by-products (DBPs) formation. Enhanced coagulation is thus introduced to most water utilities treating surface water. Jar-test experiments were conducted to compare the effectiveness of alum and ferric chloride in removing DBPs precursors from eight synthetic water samples, each representing a different element of the USEPA’s 3×3 enhanced coagulation matrix, and the residual metal (aluminum/iron) concentration in the treated water was assessed. Coagulant type influenced the removal of total organic carbon (TOC) and which was enhanced with increasing coagulant dose. For all the treated samples coagulation with ferric chloride proved to be more effective than alum at similar doses and the mean values of treatment efficiencies were 51% and 32%, respectively. Ferric chloride was therefore considered the better chemical for enhancing the coagulation process. The results of residual metal concentration measurements in treated water showed that iron and aluminum concentrations had been increased as expected but the quality of water concerning the residual metal deteriorated much more in cases of under-dosing. Despite expecting high residual Al and Fe concentrations under enhanced coagulation, metal concentrations were frequently remained low and were not increased appreciably

Kinetic and degradation efficiency of trichloroethylene (TCE) via photochemical process from contaminated water

Trichloroethylene (TCE) is a common pollutant in groundwater and one of the priority pollutants listed by the U.S. EPA. With regard to concentration ranges in previous studies exceeding environmental levels by far with millimolar concentrations of TCE, this study deals with the degradation of TCE at micromolar concentrations by UV/H2O2. The degradation rate of TCE at different dilute solution levels, 30, 300 and 3000 g L-1 (0.22, 2.28 and 22.83 micromolar) at different initial pHs was examined. In addition, samples were taken from four contaminated wells to measure the degradation rate of TCE. It was shown that thedegradation rate of TCE increased due to the reduction of initial concentration in both aqueous solution and groundwater samples. The TCE degradation constants in groundwater samples increased by a factor of 2.05, while the initial concentration reduced from 1345.7 to 97.7 μg1 L-1. By increasing the molar ratios of H2O2 to TCE from 13 to 129, caused the degradation rates to increase in aqueous solutions. No harmful byproducts such as aloacetic acids (HAAs) were detected at these low levels of initial concentration of TCE during process. This study confirmed that application of UV/H2O2 process could be an effective method in treating contaminated groundwater by TCE at low concentrations

Degradation and toxicity reduction of phenol by ultrasound waves

The effects of parameters such as pH, kinetic constants and initial phenol concentration on the sonochemical degradation of phenol and toxicity assay were studied. The experimental results showed that lower pH and lower concentration of phenol favor the phenol degradation. But the rates of phenol degradation under sonication have always been quite low. It is found that the rate of ultrasonic degradation of phenol for initial concentration of 1 mg/L is 0.018 min-1 but later it reduces with increasing of phenol initial concentration substantially and the experimental data fitted well with pseudo first-order reaction rate equation. Bioassay tests showed that phenol was toxic to Daphnia magna and so resulted in quite low LC50 values. Comparison of toxicity units (TU) between phenol and effluent toxicity showed that the TU value for effluent was 1.21 times lower than that obtained for phenol solely. Thus, the toxicity of metabolites formed during the degradation of phenol is lower than the toxicity of phenol itself. KEY WORDS: Phenol, Ultrasound, Sonochemistry, Toxicity assay  Bull. Chem. Soc. Ethiop. 2007, 21(1), 33-38

Evaluation of dairy industry wastewater treatment and simultaneous bioelectricity generation in a catalyst-less and mediator-less membrane microbial fuel cell

Increased human activity and consumption of natural energy resources have led to decline in fossil fuel. These current methods of energy production are not compatible with the environment. In this study catalyst-less and mediator-less membrane microbial fuel cell (CAML-MMFC) represents a new method for simultaneous dairy industry wastewater treatment and bioelectricity generation. The CAML-MMFC used was designed as two chambered that included an anaerobic anode and aerobic cathode compartment and was separated from each other by a proton exchange membrane. The anode and cathode electrodes were made from graphite plate. Current intensity, power density and voltage produced from wastewater as fuel were measured and the effluent from the anode compartment was examined to evaluate pollutant decrease. The maximum current intensity and power density produced were respectively 3.74 mA and 621.13 mW/m2 on the anode surface, at OLR equal to 53.22 kgCOD/m3 d and at the external resistance of 1 k Ω. The maximum voltage produced was 0.856 V at OLR equal to 53.22 kgCOD/m3 d and at temperature 35oC. The maximum coulombic efficiency of 37.16 was achieved at OLR equal to 17.74 kgCOD/m3 d. The HRT was examined as a factor influencing the power generation and when it was 5 day, maximum voltage and power density were obtained. The maximum removal efficiency of COD, BOD5, NH3, NH4 +, dissolved phosphorus, phosphorus in suspended solids, SO4 2-, TSS, and VSS was respectively achieved at 90.46, 81.72, 73.22, 69.43, 31.18, 72.45, 39.43, 70.17 and 64.6. The results showed that generating bioelectricity and dairy industry wastewater treatment by CAML-MMFC are a good alternative for producing energy and treating wastewater at the same time. © 2014 King Saud University. Production and hosting by Elsevier B.V

Penerapan Strategi Reading Guide Untuk Meningkatkan Keterampilan Membaca Bahasa Arab Pada Siswa Kelas XII SMK Tritech Medan

Penelitian ini diberlatangi oleh kurang keterampilan siswa dalam membaca bahasa arab. Strategi yang digunakan adalah strategi reading guide. Penelitian ini bertujuan untuk meningkatkan keterampilan siswa dalam membaca bahasa arab, karena sebelum menggunakan startegi ini siswa sangat kurang terampil/kurang mahir dalam membaca bahasa arab sehingga menyulitkan siswa dalam menjawab pertanyaan sesuai teks cerita yang diberikan. Jenis penelitian ini yang digunakan adalah penelitian tindakan kelas yang dilaksanakan dalam dua siklus dengan subjek penelitian siswa kelas XII SMK Tritech Medan yang berjumlah 21 siswa. Objek penelitian ini adalah strategi reading guide. Teknik pengumpulan data dilakukan melalui lembar observasi, soal tes, dan refleksi. Berdasarkan hasil peelitian yang dilaksanakan di kelas XII SMK Tritech diketahui adanya peningkatan keterampilan membaca bahasa arab siswa pada siklus I dikategorikan cukup baik dengan presentase 52,38% dengan rata-rata 6,823. Dan kemudian pada siklus II siswa mengalami peningkatan presentase 85,71 % dengan rata-rata 7,585. Hasil refleksi menyatakan bahwa adanya terjadi peningkatan keterampilan membaca bahasa arab siswa setelah menggunakan strategi reading guide