Color removal and COD reduction of biologically treated textile effluent through submerged filtration using hollow fiber nanofiltration membrane Original Research Article

Color removal and chemical oxygen demand (COD) reduction of biologically treated textile effluent through submerged filtration using nanofiltration membrane were investigated in this study. Submerged filtration tests of biologically treated textile effluent were conducted under different trans-membrane pressures (TMP) and various volume concentrating factors (VCF) employing lab-made hollow fiber membrane modules. It was found that the color and COD presented in the biologically treated textile wastewater could be effectively removed through submerged filtration using hollow fiber nanofiltration membranes with molecular weight cut-off of about 620 Da, while the electrolytes presented in the effluent were retained by the membrane to a very small extent, especially under VCF higher than 2.0, so that the nanofiltration membrane module could be operated under a low suction pressure. The increase of TMP and/or VCF resulted in a decline in water permeability and an increase in both color removal and COD reduction. Under the TMP of 0.8 bar and VCF of 4.0, the submerged nanofiltration system exhibited a steady permeate flux of 5.15 l/m2 h, a color removal rate of 99.3% and a COD reduction rate of 91.5%. Furthermore, the submerged nanofiltration system possessed high water cleaning efficiency of more than 93.0%.