Cleaning method of a water-filtration system under operation

A method for cleaning a filtration system under operation, said filtration system comprising:

• a cross-flow filtration membrane having:
• a feed side fed with a feed stream,
• a permeate side wherein a permeate stream is recovered and
• a retentate side wherein a retentate stream is recovered,
• a hydraulic circuit Cp connecting the permeate side of said cross-flow filtration membrane to the feed side of said cross-flow filtration membrane, said hydraulic circuit Cp allowing the recycling of a proportion of the permeate stream to the feed side of said cross-flow filtration membrane, and/or
• a hydraulic circuit Cr connecting the retentate side of said cross-flow filtration membrane to the feed side of said cross-flow filtration membrane, said hydraulic circuit Cr allowing the recycling of a proportion of the retentate stream to the feed side of said cross-flow filtration membrane,
• said method comprising:
• injecting an amount of a chemical product into the filtration system which is under operation in the hydraulic circuit Cp or in the hydraulic circuit Cr or upstream of said cross-flow filtration membrane,
• setting the proportion of recycled permeate stream or recycled retentate stream collected in the hydraulic circuit Cp and Cr to enable the recycling of a significant amount of unreacted chemical product having passed through said cross-flow filtration membrane to the feed side of said cross-flow filtration membrane.