Recently EC-MBR (Elctrocoagulation - Membrane Bio Reactor) has been suggested as one of alternative processes to overcome membrane fouling problems. Most important operational parameters in the EC-MBR are known to current density and contact time. Their effect on membrane filtration performances has been reported well, however, quantitative interrelationship between both parameters not been investigated yet. The purpose of this study is to give a kinetic model suggesting the current density and the contact time required to reduce the membrane fouling. The 4 different set of current densities (2.5, 6, 12 and 24 A/m2) and contact times (0, 2, 6 and 12 hr) were selected as operational parameters. After each electro-coagulation under the 16 different conditions, a series of membrane filtration was carried out. The membrane fouling decreased as the current density and contact time increased, Total fouling resistances under different conditions, Rt(=Rc+Rf) were calculated and compared to those of the controls (R0), which were calculated from the data of experiments without electro-coagulation. A kinetic approach for the fouling reduction rate (Rt / R0) was carried out and the equation ρi0.46t=7.0 was obtained, which means that the product of current density and the contact time needed to reduce the fouling in certain amounts (in this study, 10% of fouling reduction) is always constant.

Microalgae is known as one alternative energy source of the fossil fuel with the small size of 5 ~ 50 µm and negative charge. Currently, the cost of microalgae recovery process take a large part, about 20 - 30% of total operating cost. Thus, the microalgae recovery method with low cost is needed. In this study, the optimum current for Scenedesmus dimorphus recovery process using electrocoagulation techniques was investigated. Under the electrical current, Al metal in anode electrode is oxidized to oxidation state of Al3+. In the cathode electrode, the water electrolysis generated OH- which combine with Al3+ to produce Al(OH)3. This hydroxide acts as a coagulant to harvest microalgae.Before applying in 1.5 L capacity electrocoagulation reactor, Scenedesmus dimorphus was cultured in 20 L cylindrical reactor to concentration of 1 OD.The microalgae recovery efficiency of electrocoagulation reactor was evaluated under different current conditions from 0.1 ~ 0.3 A. The results show that, the fastest and highest recovery efficiency were achieved at the current or 0.3 A, which the highest energy efficiency was achieved at 0.15 A.

There is a need for a method that can effectively remove wastewater containing small-sized particles such as TiO2. In this study, we attempted to remove TiO2 wastewater using electrocoagulation-electroflotation two-step separation. The TiO2 wastewater was effectively removed via batch electrocoagulation-electroflotation separation. However, in the batch process, the simultaneous operation of electrocoagulation and electoflotation was challenging due to the high residual turbidity. In the continuous operation, electrocoagulation and electoflotation reactors were kept separate. The turbidity removal in continuous operation was similar to that in the batch process, nevertheless, the residual Al concentration was high, leading to the conclusion that counterterm ensures against residual Al were necessary.

The Electrocoagulation-Flotation (ECF) process has great potential in wastewater treatment. ECF technology is effective in the removal of colloidal particles, oil-water emulsion, organic pollutants such as microalgae, and heavy metals. Numerous studies have been conducted on ECF; however, many of them used a conventional plate-type aluminum anode. In this study, we determined the effect of changing operational parameters such as power supply time, applied current, NaCl concentration, and pH on the turbidity removal efficiency of kaoline. We also determined the effects of different electrolyte types (NaCl, MgSO4, CaCl2, Na2SO4, and tap water), as well as the differences caused by using a plate-type and mesh-type aluminum anode, on the turbidity removal efficiency. The results showed that the optimal values of ECF time, applied current, NaCl concentration, and pH were 5 min, 0.35 A, 0.4 g/L NaCl in distilled water, and pH 7, respectively. The results also revealed that the turbidity removal efficiency of kaoline in different electrolytes decreased in the following sequence, given the same conductivity: tap water > CaCl2 > MgSO4 > NaCl > Na2SO4. The turbidity removal efficiency of the mesh-type aluminum anode was significantly greater than the plate-type aluminum anode.

In this study, HA removal by electrocoagulation (EC) using Aluminum (Al) electrodes was evaluated based on Al species and HA was characterized to investigate the HA removal mechanisms. Results showed that Al electrodes were better than Fe electrodes, wherein Al flocs were found to be positively charged by which the negatively charged HA can be attracted. HA removal was 88.9% at 10 min and 91.3% at 20 min, at the initial pH of 4.5 and 6.5, respectively. The Ferron analysis showed that the formation of monomeric Al species (Ala), medium polymer Al species (Alb), and colloidal or solid Al species (Alc) was dependent on initial pH and current density (CD). At higher pH, higher concentration of colloidal or solid Al species (Alc)wasobserved. At higher CD, the HA removal was faster than at low CD, and Alcspecie in the floc was dominant. The spectroscopic analysis of the residual soluble HA showed the preferential removal of highly condensed structures of HA, regardless of CD. The results in this study showed that Alb and Alc, especially Alc, contribute much to the HA removal and that the highly conjugated moieties of HA are readily removed by EC. Specific UV absorbance (SUVA) analysis reveals that aromatic compounds were decreased by the oxidation at the anode. Size exclusion chromatography reveals that high molecular weight (MW) fractions were preferentially removed by EC than the low MW component.

The separation of TiO2 wastewater carried out by an electrocoagulation/flotation process, which had various operating parameters. The effect of electrode material (aluminum and four dimensionally stable electrode), applied current (0.07∼0.5 A), electrolyte concentration (0∼1 g/L), solution pH (3∼11), initial turbidity (1000∼20000 NTU) and suspended solid concentration (5000∼25000 mg/L) were evaluated. Turbidity removal efficiency of the soluble anode (aluminum), which could produce metal ions, was higher than that of the dimensionally stable electrode. Considering operation time, turbidity removal and electric power, optimum current was 0.19 A. The more NaCl dosage was high, the less electric power was required. However, optimum NaCl concentration was 0.125 g/L considered removal efficiency, operation time and cost. Initial TiO2 concentration did not affected turbidity removal on the electrocoagulation/ flotation operation. The electrocoagulation/flotation process was proved to be a very effective separation method in the removal of TiO2 from wastewater.

This research studied the characteristics and applicability of electrocoagulation using aluminium electrode for the color and COD removal in textile wastewater. Electrocoagulation reactor used two different electrode, Fe and Al, since in the general chemical wastewater treatment, aluminium and ferrous salts were used as coagulants. Aluminium electrode showed higher removal efficiency of color and COD than ferrous electrode did. The COD and color removal efficiency improved at the 0.192A/dm2 current density. Thus, the electrocoagulation process with bipolar aluminium electrode showed better efficiency in the decolorization and COD removal rate of textile wastewater effluent than custom coagulants did.