Patrick Drogui

Effectiveness of electrocoagulation process in removing organic compounds from slaughterhouse wastewater using monopolar and bipolar electrolytic cells

Slaughterhouse wastewaters contain varied and high amounts of organic matter (e.g., proteins, blood, fat). In order to produce an effluent suitable for stream discharge, electrochemical techniques have been particularly explored at the laboratory pilot scale for organic compounds removal from poultry slaughterhouse (PS) effluent. Electrocoagulation (EC) process was tested using either mild steel or aluminium electrodes arranged in bipolar (BP) or monopolar configuration system. Results showed that the best performance was obtained using mild steel BP electrode system operated at a current intensity of 0.3A, through 60 or 90 min of treatment. Under these conditions, removals of 86+/-1% and 99+/-1% were measured for BOD and oil and grease, respectively, whereas soluble COD and total COD were removed by 50+/-4% and 82+/-2%, respectively. EC is also efficient for decolorization (red-color) and clarification of the PS effluent. Removals of 89+/-4% and 90+/-4% have been measured for total suspended solids and turbidity, respectively. Electrochemical coagulation operated under the optimal conditions involves a total cost of 0.71 USD

Electrochemical degradation of polycyclic aromatic hydrocarbons in creosote solution using ruthenium oxide on titanium expanded mesh anode.

per cubic meter of treated PS effluent. This cost includes energy and electrode consumptions, chemicals, and sludge disposal.

Removal of metals in leachate from sewage sludge using electrochemical technology

In this study, expanded titanium (Ti) covered with ruthenium oxide (RuO(2)) electrode was used to anodically oxidize polycyclic aromatic hydrocarbons (PAH) in creosote solution. Synthetic creosote-oily solution (COS) was prepared with distilled water and a commercial creosote solution in the presence of an amphoteric surfactant; Cocamidopropylhydroxysultaine (CAS). Electrolysis was carried out using a parallelepipedic electrolytic 1.5-L cell containing five anodes (Ti/RuO(2)) and five cathodes (stainless steel, 316 L) alternated in the electrode pack. The effects of initial pH, temperature, retention time, supporting electrolyte, current density and initial PAH concentration on the process performance were examined. Experimental results revealed that a current density of 9.23 mA cm(-2) was beneficial for PAH oxidation. The sum of PAH concentrations for 16 PAHs could be optimally diminished up to 80-82% while imposing a residence time in the electrolysis cell of 90 min. There was not a significant effect of the electrolyte (Na(2)SO(4)) concentration on oxidation efficiency in the investigated range of 500-4000 mg/L. However, an addition of 500 mg Na(2)SO(4)L(-1) was required to reduce the energy consumption and the treatment cost. Besides, there was no effect of initial PAH concentration on oxidation efficiency in the investigated range of 270-540 mg PAHL(-1). Alkaline media was not favourable for PAH oxidation, whereas high performance of PAH degradation could be recorded without initial pH adjustment (original pH around 6.0). Likewise, under optimal conditions, 84% of petroleum hydrocarbon (C(10)-C(50)) was removed, whereas removal yields of 69% and 62% have been measured for O&G and COD, respectively. Microtox and Daphnia biotests showed that electrochemical oxidation using Ti/RuO(2) could be efficiently used to reduce more than 90% of the COS toxicity.

Photoelectrocatalytic degradation of chlortetracycline using Ti/TiO2 nanostructured electrodes deposited by means of a Pulsed Laser Deposition process

Abstract Heavy metals in acidic leachates from sewage sludge are usually removed by chemical precipitation, which often requires high concentration of chemicals and induces high metallic sludge production. Electrochemical technique has been explored as an alternative method in a laboratory pilot scale reactor for heavy metals (Cu and Zn) removal from sludge leachate. Three electrolytic cell arrangements using different electrodes materials were tested: mild steel or aluminium bipolar electrode (EC cell), Graphite/stainless steel monopolar electrodes (ER cell) and iron‐monopolar electrodes (EC‐ER cell). Results showed that the best performances of metal removal were obtained with EC and EC‐ER cells using mild steel electrodes operated respectively at current intensities of 0.8 and 2.0A through 30 and 60 min of treatment. The yields of Cu and Zn removal from leachate varied respectively from 92.4 to 98.9% and from 69.8 to 76.6%. The amounts of 55 and 44 kg tds‐1 of metallic sludge were respectively produced using EC and EC‐ER cells. EC and EC‐ER systems involved respectively a total cost of 21.2 and 13.1 CAN

Review of Electrochemical Technologies for Environmental Applications

per ton of dry sludge treated including only energy consumption and metallic sludge disposal. The treatment using EC‐ER system was found to be effective and more economical than the traditional metal precipitation using either Ca(OH)2 and/or NaOH.

Di 2-ethylhexylphtalate in the aquatic and terrestrial environment: A critical review

Ti/TiO(2) electrode was prepared by means of the Pulsed Laser Deposition method and used in a photoelectrocatalytic oxidation (PECO) process in order to degrade chlortetracycline (CTC). The deposited TiO(2) coatings were found to be of rutile structure. High treatment efficiency of CTC was achieved by the PECO process compared to the conventional electrochemical oxidation, direct photolysis and photocatalysis processes. Several factors such as current intensity, treatment time, UV lamp position and initial concentration of CTC were investigated. Using a 2(4) factorial matrix, the best performance for CTC degradation (74.3% of removal) was obtained at a current intensity of 0.5A during 120 min of treatment time and when the UV lamp was immersed in the solution in the presence of 25 mg L(-1) of CTC. The current intensity and treatment time were the main parameters influencing the degradation rate of CTC. Subsequently, a central composite design methodology has been investigated to determine the optimal experimental parameters for CTC degradation. The PECO process applied under optimal conditions (at current intensity of 0.39 A during 120 min with internal position of the UV lamp) is able to oxidize around 74.2 ± 0.57%, of CTC.

Selective recovery of Cr and Cu in leachate from chromated copper arsenate treated wood using chelating and acidic ion exchange resins

This review deals with electrochemical methods for water, wastewater, wastes and soils treatment. The electrochemical technique combines both physical chemistry and electronic science and has widely proved to be a clean, flexible and powerful tool for the development of new methods for waste and water treatment. Likewise, electrochemical treatment is generally characterized by simple equipment, ease of operation, short retention time and negligible equipments for adding chemicals. Besides, electrolytic cells can be easily automated and coupled with other processes including, biological, chemical and physical processes to enhance the efficiency of the treatment. A particular focus is given to electrocoagulation (EC), electrodeposition (ED), electroflotation (EF), electrokinetic (EK) and electrooxidation (EO) processes. These technologies are effective in improving the treatment quality of industrial wastes, wastewaters and drinking water on integration into a treatment plant or replacement of conventional processes that are found to be less effective to eliminate specific organic and inorganic pollutants EC can be used for clarifying water or to eliminate organic, inorganic and microbial pollutants from wastewater. The technology delivers in situ coagulant by anodic dissolution of sacrificial electrodes aluminium or iron) and is finding wider applications with the possible improvements in the reduction of energy consumption and metallic sludge production ED is a well-established process for toxic metal removal whose effectiveness can be greatly improved by selecting suitable electrode material (type and geometry of the electrode). EF technology is effective in removing suspended solids, colloidal particles and oil & grease suspension. EK technology is a promising method to remove toxic metals from the matter with low hydraulic permeability or to enhance dewaterability of wastes including soils and sludge. The development of new, more stable and active catalytic electrodes has led to a renewed interest in EO for degrading refractory organic pollutants This paper covers both established and recent developments in the field of electrochemical technologies for waste, water and wastewater treatment based on more than 158 patents and publications cited or analyzed.

Optimization of a chemical leaching process for decontamination of CCA-treated wood

Phthalates are being increasingly used as softeners-plasticizers to improve the plasticity and the flexibility of materials. Amongst the different plasticizers used, more attention is paid to di (2-ethylhexylphtalate) (DEHP), one of the most representative compounds as it exhibits predominant effects on environment and human health. Meanwhile, several questions related to its sources; toxicity, distribution and fate still remain unanswered. Most of the evidence until date suggests that DEHP is an omnipresent compound found in different ecological compartments and its higher hydrophobicity and low volatility have resulted in significant adsorption to solids matrix. In fact, there are important issues to be addressed with regard to the toxicity of this compound in both animals and humans, its behavior in different ecological systems, and the transformation products generated during different biological or advanced chemical treatments. This article presents detailed review of existing treatment schemes, research gaps and future trends related to DEHP.

Review on fate and mechanism of removal of pharmaceutical pollutants from wastewater using biological approach.

The purpose of this study was to selectively remove chromium and copper from CCA-treated wood acid leachates (initial concentrations of 447-651 mg As l(-1), 374-453 mg Cu l(-1) and 335-622 mg Cr l(-1)) using ion exchange resins and precipitation techniques. Batch experiments revealed that the chelating resin Dowex M4195 had a high copper selectivity in the presence of chromium while the Amberlite IR120 resin had a high chromium sorption capacity. Combining M4195 and IR120 resins in four successive columns, made with Plexiglas tube, led to 96% copper extraction and 68% chromium extraction. NH(4)OH (4M) efficiently eluted copper from the chelating resin while H(2)SO(4) (10%v/v) was used for IR120 resin elution. Copper and chromium recovery by elution reached 94% and 81%, respectively. Successive sorption and elution steps using M4195 and IR120 ion exchange resins presented similar metal removal capacities over the five cycles. No resin deterioration was observed but the results suggested arsenic bulk diffusion into the M4195 resin. Successive treatments of CCA-treated wood leachate with M4195 and IR120 allowed for copper and chromium removal while arsenic could be extracted by coagulation treatment with ferric chloride and precipitation with Ca(OH)(2) at pH 5.7. This final process led to 99.9% arsenic removal. The final effluent contained less than 1 mg l(-1) of arsenic, chromium and copper.

Effectiveness of soil washing, nanofiltration and electrochemical treatment for the recovery of metal ions coming from a contaminated soil.

Increasing volumes of discarded Chromated Copper Arsenate (CCA)-treated wood require the development of new treatment and recycling options to avoid the accumulation of wood wastes in landfill sites, resulting in dispersion of contaminants in the environment. The aim of this study is to design an economic chemical leaching process for the extraction of arsenic, chromium and copper from CCA-treated wood. Choice of chemical reagent, reagent concentration, solid-to-liquid ratio, temperature, reaction time and wood particle size are parameters which have been optimized. Sulphuric acid was found to be the cheapest and most effective reagent. Optimum operation conditions are 75 degrees C with 0.2N H(2)SO(4) and 150 g wood L(-1). Under these conditions, three leaching steps lasting 2h each allowed for 99% extraction of arsenic and copper, and 91% extraction of chromium. Furthermore, arsenic concentration in TCLP leachate is reduced by 86% so the environmental hazard is reduced. Decontamination process cost is estimated to 115US