MEMBRANE PROCESSES or membrane technology include various separation methods using a membrane. These include microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (UO) or hyperfiltration. Due to the different pore sizes, not only bacteria or viruses but also ions can be filtered out of the water. The various MEMBRANE PROCESSES are used in water softening (nanofiltration) or drinking water treatment.