ABSTRACT
The treatment of synthetic oily wastewater having the characteristics of a typical petroleum refinery wastewater (PRW) by electrocoagulation (EC) using iron and aluminum electrodes was conducted in an electrolytic reactor equipped with fluid recirculation. During the treatment, the emulsion stability was followed by the measurement of Zeta potential and particle sizes. Effects of some operating conditions such as electrodes material, current density and electrolysis time on removal efficiencies of turbidity, and chemical oxygen demand (COD) were investigated in detail. The PRW purification by the EC process was found to be the most effective using aluminum as the anode and cathode, current density of 60â A/m(2) and 30â min of electrolysis time. Under these conditions, the process efficiencies were 83.52% and 99.94%, respectively, for COD and turbidity removals which correspond to final values of 96â mg O2/L and 0.5 NTU. A moderate energy consumption (0.341â kWh) was needed to treat 1â m(3) of PRW. Besides, the ecotoxicity test proved that toxic substances presented in the PRW, and those inhibiting the germination growth of whet, were eliminated by the EC technique.
Subject(s)
Electrocoagulation/methods , Industrial Waste/analysis , Petroleum , Waste Disposal, Fluid/methods , Wastewater/chemistry , Water Purification/methods , Biological Oxygen Demand Analysis , Oil and Gas IndustryABSTRACT
Organic compound is the main pollutant in industrial effluent. Conventional wastewater treatment processes are inefficient for the removal of toxic or non-biodegradable organic pollutants. Advanced electrochemical depollution is a very efficient and economic method, suitable when the wastewater contains toxic and recalcitrant organic pollutants. The aim of the present study was to investigate the application of the electro-Fenton (EF) process for the degradation and mineralization of a stable oil-in-water emulsion (0.01% in v/v). The effects of operating parameters such as cathode material (graphite, Ti/Pt and steel), nature (Na2SO4, NaNO3 and NaCl) and dose of electrolyte (25-75â mM), initial ferrous ions concentration (1-75â mM), current intensity (0.1-0.2â A) and operating time, on chemical oxygen demand (COD) removal efficiency, were studied. Results showed that the EF method can be used efficiently for the degradation of stable cutting oil emulsion. For considered initial conditions (bubbling compressed air at 1â L/min, 0.15â A, pH 3, [Na2SO4]=0.05â M, [FeSO4]=0.015â M, COD0=400â mgâ O2/L), the best removal efficiencies were obtained under the following conditions: graphite as cathode material, 180â min for treatment duration and 0.05â M [Na2SO4]. For these conditions, treatment of 250â mL of emulsion led to 93.6% of cutting fluid mineralization, which correspond to 25â mgâ O2/L of final COD, 19â kWh/m3 of treated wastewater and 24.039â kWh/kg of COD removal.
Subject(s)
Hydrogen Peroxide/chemistry , Iron/chemistry , Minerals/isolation & purification , Oils/isolation & purification , Water Pollutants, Chemical/isolation & purification , Water Purification/methods , Electrochemistry/methods , Electrolysis/methods , Hydrogen Peroxide/radiation effects , Iron/radiation effects , Minerals/chemistry , Oils/chemistry , Oils/radiation effects , Radiation Dosage , Wastewater/chemistry , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/radiation effectsABSTRACT
The treatment of very concentrated oil-water emulsions by electrocoagulation (EC) was experimentally investigated as a pre-treatment step prior to a membrane process. The oil-water emulsion was prepared from a cutting mineral oil B22 currently used for drilling and machining operations. The electrocoagulation progress was followed by the measurement of COD, turbidity and pH in a batch process with recirculation of the liquid. This study is mainly focused on the effects of operating parameters such as initial pH, current density, oil concentration and recirculation rate, on the de-emulsification efficiency. Kinetic curves showed that the EC process exhibits two phases: a "reactive phase" during which the COD and the turbidity removals increase with electrolysis, and a stationary phase for which further aluminium dissolution is useless in the pollution abatement. The results showed that the treatment efficiency increases with increasing current density, but decreases with oil concentration. It appears that treatment of the considered cutting oil is completed through dissolution of around 10mgAl/g oil, with a slight positive effect of the liquid flow rate. Best results are also obtained with initial pH near 7.