Patent ID: 9067801
Filing Date: 2015-06-30
Classification: B01D,C02F

Abstract:
1. A method of removing hardness, suspended solids and dissolved solids from a feedwater stream by pretreating the feedwater stream and thereafter directing the feedwater stream through at least one reverse osmosis unit, the method comprising: a. removing a majority of the hardness from the feedwater stream through a chemical softening process and reducing the concentration of total hardness in the feedwater stream to less than 55 mg/L as CaCO b. prior to separating the feedwater stream into the concentrated feedwater stream and the clarified feedwater stream mixing a second alkaline reagent with the feedwater stream and raising the pH of the feedwater stream to above 10.5; c. directing the clarified feedwater stream to a filtering unit and further removing suspended solids from the feedwater stream; d. directing the clarified feedwater stream into an ion exchange unit and removing residual hardness from the feedwater stream; e. after subjecting the clarified feedwater stream to treatment in the filtering unit and ion exchange unit, directing the clarified feedwater stream to a reverse osmosis unit and removing dissolved solids from the feed stream and producing a permeate stream and a reject stream where the reject stream includes dissolved solids; and f. generally maintaining the pH at above 10.5 such that when the feedwater stream reaches the reverse osmosis unit the pH of the feedwater stream is above 10.5 which reduces the tendency of one or more membranes forming a part of the reverse osmosis unit to scale.