Membrane technology is a process that has not been widely used in potable water treatment, except for reverse osmosis applications. Because of increasingly stringent regulations, this technology is being examined for the potential application of ultrafiltration, microfiltration, and nanofiltration to water treatment processes. Membranes can be used as the primary means to remove materials from water, but they can also be used in conjunction with other physical, chemical, or biological processes to separate phases, isolate organisms, or to bring two phases into contact with each other.