Process water supply unit for supplying a medical treatment unit with process water (BW), containing biocide, comprising: a container receptacle for receiving a pressurised water container; a compressed air inlet for connecting the process water supply unit to a compressed-air source; a compressed-air connection, via which compressed air (DL) originating from the compressed-air inlet can be introduced into the pressurised water container; and a process water connection, via which the process water (BW) which is to be delivered out from the pressurised water container by the compressed air (DL) introduced into the pressurised water container can be dispensed to the medical treatment unit, wherein the process water supply unit has a sterile air filter which is integrated into a compressed-air path between the compressed-air inlet and the compressed-air connection or into a compressed-air path between the external compressed-air source and the compressed-air connection.