Evaluation of COD and turbidity removal from woodchips wastewater using biologically sequenced batch reactor

The wood industry consumes a lot of water. Due to the reduction of water resources in the world, the treatment of this contaminated water is very essential. In this study, the removal efficiencies of the chemical oxygen demand (COD) and turbidity from woodchips wastewater with the use of a sequencing batch reactor (SBR) were studied at a bench scale. Woodchips wastewater samples were collected with a COD of 1300 mg L-1 and a turbidity of 93 NTU. The optimization of the SBR process was investigated by response surface methodology (RSM) based on a central composite design (CCD). A quadratic polynomial model was fit to the data with R-2 of 0.9919 for COD reduction, R-2 of 0.9910 for turbidity removal, and R-2 of 0.9945 for sludge volume Index (SVI), respectively. The effect of three parameters, including initial COD, mixed liquor suspended solids (MLSS), and Hydraulic retention time (HRT) on the COD reduction and turbidity removal were evaluated. The initial COD (A), MLSS (B), cycle time (C), AB, AC, BC, A(2), B-2, and C-2 were considered as the affective parameters in the COD reduction. Initial COD (A), MLSS (B), A(2), B-2, C-2, AC, and BC were observed as the remarkable model terms on the turbidity removal. Also, initial COD (A), MLSS (B), cycle time (C), B-2, C-2, and BC were the significant model factors in SVI index. At optimal conditions, involving an initial COD of 1000 mg L-1, an organic loading rate (OLR) of 0.450 kg COD/m(3)d, MLSS of 3000 mg L-1, and cycle time of 24 h, we observed 94.6% of COD reduction, 98.5% turbidity removal, and 79 mL g(-1) SVI. The results also showed that the kinetic of COD reduction and turbidity removal could be represented by the pseudo-second-order model. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.