In-situ generation of effective coagulant to treat textile bio-refractory wastewater: Optimization through response surface methodology

Abstract

The discharge of textile industries wastewaters into waterbodies remains a constant threat for environment. Through this study, we aim to optimize Textile Bio-refractory Wastewater (TBW) treatment by electrocoagulation (EC) process. EC runs were carried out in batch mode using an electrolytic cell equipped with iron electrodes, in parallel monopolar (MPP) configuration. TBW’s characterization has revealed a low biodegradability index value (BOD5/COD = 0.02). Most of optimizations studies have focused on traditional “one-factor-at-a time” methodology. However, this approach is visibly time consuming, does not take into account interactions effects and could give unreliable results. Therefore, we opted for Response surface methodology (RSM) which is a powerful statistical-based technique for modelling and optimization of complex processes. In this perspective, factorial experimental design (FD: 2k=3) was used to determine the influent parameters on textile pollutants removal. Electrolysis time (X1) and Current intensity (X2) were the main influential parameters with a cumulative contribution superior to 94 % for each of the three responses studied (turbidity, COD, Absorbance) whereas interactions and pH contributions are almost negligible (< 4% for pH). Afterwards, a central composite design (CCD) has been used to determine optimal conditions that maximize simultaneously all responses. Experimental results predicted by RSM model (99.95 % of Turbidity; 78.87 % of COD; 84.91 % Absorbance) under optimal conditions (75 min; 2.61 A and pH = 6.83) were close to the theoretical ones. EC process operated under optimal conditions involves a total cost of 4.95 US$/ m3 of treated TBW including chemicals, energy and electrode consumption.