Development of novel electrocoagulation reactor (ECR) for turbidity removal and decolorization from textile industry wastewater

Abstract

High concentration of dyes together with turbidity were frequently found in the effluents of textile industry wastewater, which are the toxic substances. To remove these contaminants, the combination between electrocoagulation process (EC) and separation has been proposed in this study. The objective of this present work is to design and evaluate the new electrocoagulation reactor (ECR) for treating dye and turbidity from synthetic textile wastewater. The optimization of electrode configuration and design parameter were examined with the batch column reactor for containing 4 liters of wastewater. The result showed that monopolar arrangement within the inner gap 1.5 cm and current density 1.5 mA/cm2 were the optimal condition in terms of gas flow rate over electrode loss ratio (Qg/Loss). It was then studied the removal kinetic of the design parameters for ECR such as hydraulic retention time, optimal current density, and settling overflow rate. Removal kinetic was studied with initial concentration 250 NTU and 6,000 ADMI of turbidity and reactive dye, respectively. The optimal current density 4.5 mA/cm2 was obtained with 25 to 30 minutes of EC electrolyze time in order to achieve the treatment efficiency 95% of both bentonite and dye. Moreover, the comparative analysis between electrocoagulation (EC) and chemical coagulation (CC) was examined. Both EC and CC are possibly used for removal turbidity and color, however, the economization will be subsequently studied. Estimation of the treatment cost through both processes was examined. It can be concluded that if there was only turbidity in wastewater with low concentration, about 50 NTU, conventional system is preferred. However, it is usually co-existed with color and high concentration. Therefore, EC is more suitable for treating turbidity and color from textile wastewater in terms of economic aspect for high concentration. ECR was finally designed in rectangular shape, which was combined between EC and separation process in continue operation. The internal flow pattern in ECR was studied by residence time distribution (RTD) method and the result showed that ECR tended to be plug flow reactor with homogenous baffles of 3 baffles (90% - 90% - 90%). ECR could remove turbidity and dye individually up to 95% with flow rate 3 LPM, and 97% with flow rate 1 LPM, respectively. For simultaneous pollutants, the results showed that removal efficiency can be achieved up to 94% (turbidity) and 96 % (color) with flow rate 2 LPM. Furthermore, the improvement by adding tube settler was studied and expressed that the 2 modules at the higher position could improve the treatment efficiency of turbidity about 10 - 15 % at 50 minutes. The design criteria of ECR for removal of turbidity and dye from textile wastewater was finally proposed.