Recovery of beverage industry wastewater for reuse in cooling towers

In this thesis study, with the aim of water savings from non-alcoholic beverage industry, wastewaters originating from tank and bottle washing operations, pasteurization units and plant cleaning operations were subjected to membrane processes for recovery and reuse in cooling towers in the same plant. In experimental studies conducted under total recycle mode of operation, two ultrafiltration (UF) membranes with molecular weight cut off (MWCO) values of 10 kDa and 5 kDa and one nanofiltration (NF) membrane were tested. Trans membrane pressure was set to 2 bars for UF and 4 bars for NF. Considering the water quality criteria for cooling towers, removals were calculated for total suspended solids (TSS), turbidity and chemical oxygen demand (COD). TSS and turbidity removals were 100% for UF and NF, however COD removals varied. In UF, a feed COD concentration of 796 mg/L resulted in a permeate COD concentration of 286 mg/L (63% removal). On the other hand, in NF, a feed COD value of 207 mg/L resulted in a permeate COD of 147 mg/L (31% removal). Flux decline was in the range of 10% - 20%. It was revelaed that both processes could not meet the water quality criteria of 75 mg/L COD for cooling towers. In the cost study for a possible investment, the volume of wastewater from the relevant facility was taken into consideration. As a result, the current cost for the NF system is calculated as 6.601 USD. It is possible to use the treated wastewater in cooling towers by either mixing with clean water at the required ratios or applying additional treatment.