Decolorization of baker’s yeast wastewater by nanofiltration membrane and performance evaluation using response surface methodology (RSM)

In this study, a polyamide membrane (NF-CSM 4040 commercial membrane) was examined in the treatment of baker’s yeast wastewater (BYW). The response surface methodology (RSM) used in the present study was a face-centered central composite design (CCFD). The nanofiltration process was analyzed and modeled with three numerical independent factors, namely concentration of feed chemical oxygen demand (COD) (1000–5000 mg/L), pH (3–9) and operating pressure (3–6 bar) using RSM. In order to analyze the process, two dependent parameters (flux and rejection) were studied as the process responses. Concentration of feed COD had a reverse impact on flux and rejection, while pH did not show a significant effect on the responses. The operating pressure showed a sharp increasing effect on flux. Maximum flux was found to be about 37 kg/m2.h, at a concentration of feed COD of 1000 mg/L, an operating pressure of 6 bar and a pH of 6. Maximum rejection (91%) was obtained at a COD of 5000 mg/L, a pH of 6 and an operating pressure of 3 bar. Consequently, the membrane technology could be a promising approach to the removal of natural dye from BYW.