There are several factors that can affect the performance of an ultra filtration system. A brief discussion is given below. Flow Across the Membrane surface : The permeate rate increases with the flow velocity of the liquid across the membrane surface. Flow velocity is especially critical for liquids containing emulsions or suspensions. Higher flow also means higher energy consumption and larger capacity pumps. Increasing the flow velocity also reduces the fouling of the membrane surface. Generally an optimum flow velocity is arrived at by a compromise between the pump horsepower and increase in permeate rate. Operating Pressure : Permeate rate is directly proportional to the applied pressure across the membrane surface. However, due to increased fouling and compaction the operating pressures rarely exceed 100 psig and are generally around 50 psig. In some of the capillary-type ultra filtration membrane modules, the operating pressures are even lower due to the physical strength limitation imposed by the membrane module. Operating Temperature : Permeate rates increases with the increasing temperature. However, temperature generally is not a controlled variable. It is important to know the effect of temperature on membrane flux in order to distinguish between a drop in permeate due to a drop in temperature and the effect of other parameters.