A liquid treatment system (2； 2’； 102； 202； 302) comprising:at least one ultra-violet (UV) light treatment lamp (6) arranged within an elongated protective UV-transparent sleeve (8； 8’) provided along a central longitudinal axis A, said sleeve (8； 8’) having an outer surface (10； 10’) and an essentially circular crosssectional shape； andan elongated reactor (12； 12’； 12”； 312) configured to receive said sleeve (8； 8’), whereby an elongated liquid treatment chamber (4； 4’) for receiving liquid to be treated, is provided between an inner surface (14； 14’； 314) of the reactor (12； 12’； 12”； 312) and the outer surface (10； 10’) of the sleeve (8； 8’)； wherein said liquid treatment system (2； 2’； 102； 202； 302) further comprisesat least one cleaning arrangement (17； 17’； 77； 87) comprising at least one cleaning device (16； 16’； 79； 89), wherein said cleaning arrangement is configured to compress said cleaning device (16； 16’； 79； 89) towards the outer surface (10； 10’) of the sleeve (8； 8’) and to transfer the cleaning device (16； 16’； 79； 89) over the sleeve surface for cleaning the outer surface (10； 10’) of the sleeve (8； 8’), wherein the at least one cleaning device (16； 16’； 79； 89) comprises at least one metal braid.
