Seawater RO treatment of RO concentrate to extreme silica concentrations

Abstract

Severe restrictions exist in the disposal of the concentrate from the 15 mgd (2370 m3/h) reverse osmosis (RO) plant in El Paso, Texas (i.e., 15 mgd blended to 27.5 mgd). The current permit for the disposal by deep well injection limits the total dissolved solids in the brine to 10,000 mg/l. This limits water recovery in the plant and drives up the cost of sending a large volume of the concentrate a long distance for discharge. We have continued to work on developing a concentrate treatment process aimed at zero liquid discharge or a greatly reduced concentrate volume suitable for evaporation ponds. This is an interim report documenting an exciting demonstration of the feasibility of using a seawater RO system and synergistic antiscalant and low pH inhibition of reactive silica polymerization to concentrate the primary brackish water RO concentrate to total silica concentrations exceeding 1000 mg/l. This approach makes possible the use of tandem brackish RO followed immediately by a seawater RO (SWRO) to a...