Ultrafiltration of wastewater from isolated soy protein production: A comparison of three UF membranes

The proteins of the wastewater from ISP production are small molecules (8–50 kDa) that were not removed during the production process; their recovery would result in large productive and financial advantages. Ultrafiltration appears as good alternative in wastewater treatment; one of the biggest limitations is the decrease in permeate flux. The performance of three UF membranes (5, 20 and 50 kDa) treating the wastewater from ISP production was evaluated. The use of these membranes is very promising regarding organic load and protein content reduction. The 5-kDa membrane presented the best results: the lowest permeate flux reduction, the most elevated retention percentages (34% of COD, 52% of protein, 21% of TS and 86% of TSS) and the wastewater with the best final quality.