Abstract: A filtration process has a coagulation step and a membrane filtration step. The membrane filtration step has a permeation step followed by a cleaning step. In the coagulation step, a coagulant is added to feed water during a period of time beginning generally at the start of the permeation step and ending in a range from about 50% to 85% of the duration of the permeation step.

Abstract: A method of cleaning filtering membranes involves scouring the membranes with bubbles while the lumens of the membranes contain a gas at pressure below the bubble point of the membranes. The method may be combined with an integrity test or chemical cleaning process also involving adding a gas to the lumens of the membranes. A tank containing the membranes may be full, draining, refilling, or at a lowered water surface level during the air scouring process. The membranes may be horizontally oriented and assume a concave downward shape during the scouring process.

Abstract: A filtration process has permeation periods and deconcentration periods. The length of the permeation period or periods between backwashes is chosen, or controlled, to allow the system to reach a TMP and flux value at which the system is operating near its mechanical limits.

Abstract: A spiral wound membrane filtration module is operated with a single pass through the feed side and without cross-flow on the permeate side. Recovery is 70% or more and feed side velocities are between 0.05 and 0.4 feet per second. The module may have dams in the spacer material on the shell/feed side to provide a feed path with multiple passes across the membrane leaves. A small-scale system for using such a module, for example to soften and filter water with a nanofiltration membrane, is described. The system includes a chemical cleaning apparatus and process.