Abstract: A system for cleaning feed water of variable quality, the system comprising an inlet for selectively delivering feed water to one or other of at least two feed chambers, each feed chamber having a delivery pipe for delivering feed water to a reverse osmosis or nanofiltration; a pump to deliver the feed water from one of the chambers through its associated delivery pipe to the reverse osmosis or nanofiltration to create a concentrated feed stream and a product water stream; return pipes for selectively returning the concentrated feed stream to one or other of the at least two feed chambers; a product water outlet for removal of the product water; and means for switching the delivery of the concentrated feed stream between the selectable return pipes upon detection of a predetermined reduction in efficiency within one or another of the feed chambers.

Abstract: A water intake and pretreatment system (10) comprising an inlet for delivering water from a natural source to a reservoir (12); said inlet to reservoir having a net screen (16) to prevent entry of organisms above a predetermined size and including a one-way gate (30) to allow organisms to exit the reservoir; said reservoir further comprising a granular filter media for water and algae filtration; and a drainage layer for removal of filtered water from the granular filter media to a drainage outlet. A local backwashing apparatus (40) is included for localized backwashing of the granular filter media.