Desalination method and apparatus utilizing nanofiltration and reverse osmosis membranes

摘要: Apparatus and methods for producing potable water from an aqueous feed such as seawater utilizing a pressure vessel designed operation in the range of about 250 psig to 350 having reverse osmosis (RO) separation elements disposed upstream at least one nanofiltrate element. The supply creates no permeate flow through RO membranes, so flushes side on its way NF element where very substantial flux occurs, substantially depleted divalent ions optionally moderately monovalent ions. is collected holding tank liquid level switches, when desired reached, control system causes pump draw suction while shutting off source. When supplied elements, osmotic that permeation now occurs creating stream good quality water. During both stages operation, energy conserved by routing concentrate leaving recovery device boosts being discharged positive displacement pump.