Temperature can significantly impact membrane performance. Water temperature has a significant impact on water density and viscosity, which impacts MF and UF membrane flux - the rate of product flow through the membrane, typically expressed in gallons per day per square foot of membrane area (gfd). As the viscosity and density increase, the transmembrane pressure required to pass the water through the membrane also increases, resulting in an increase in the specific flux, which is the flux divided by the transmembrane pressure. Feed water quality conditions can also affect the flux because the rate of plugging Flux rates for MF and UF membranes typically range between 40 and 100 gfd. The design flux is typically determined by bench or pilot testing since it is dependent on specific water quality conditions and temperatures.