Water Reuse via Membrane Technology: A Case Study for Producing Cooling Water from Soft Drink Wastewater

High volumes of water are used in the soft drink industry, where purification can be achieved via membrane technology, allowing it to be reused in operating cooling towers, steam boilers, and closed-loop systems. In this study, ultrafiltration (UF) and nanofiltration (NF) were applied to produce reclaimed water for cooling towers. In experimental studies conducted under a total recycle mode of operation, two UF membranes with molecular weight cut-offs (MWCO) of 10 kDa and 5 kDa, and one NF membrane were tested. The transmembrane pressure was set to 2 bars for UF and 4 bars for NF. Considering the water quality criteria for cooling towers, removal efficiencies were calculated for total suspended solids (TSS), turbidity, and chemical oxygen demand (COD). TSS and turbidity removal rates were 100% for both UF and NF; however, COD removal rates varied. In UF, feed and permeate COD concentrations were 718 - 796 mg/L and 255 - 286 mg/L, corresponding to a removal efficiency of 64-65%. On the other hand, in NF, the feed and permeate COD concentrations were 207 mg/L and 147 mg/L, indicating a 29% removal. Flux decline was not severe; it ranged from 10% to 20%. It was revealed that further treatment is required to meet the COD criteria of 75 mg/L for cooling towers.