Patent ID: 8852437

Claim:
Method of producing a product stream of sterile water from raw water during a production cycle by ultrafiltration in at least one membrane unit in a production plant, the method comprising: continuously adding a disinfectant to the product stream of the sterile water downstream of the at least one membrane unit during the production cycle to determine whether the production plant is working properly during the production cycle, the continuously adding comprising adding, at a region of a beginning of a residence time section provided in the product stream, a known concentration of the disinfectant to the product stream; measuring a reduction of concentration of the disinfectant in the product stream between a first position downstream of the residence time section and one or more second positions downstream of the membrane unit and upstream of the residence time section and/or in a beginning portion of the residence time section; evaluating the known concentration of the disinfectant and the measured concentration of the disinfectant to permanently detect a concentration difference measurement indicative of the concentration reduction of the added disinfectant; and determining, based on the concentration difference measurement, whether the production plant is working properly during the production cycle, wherein the determining comprises determining that the production plant is working properly during the production cycle when the detected concentration difference measurement is less than or equal to a predetermined concentration difference measurement representative of a predetermined sterility of the product stream, and wherein the determining comprises determining that the production plant is not working properly during the production cycle when the detected concentration difference measurement exceeds the predetermined concentration difference measurement.