Method and apparatus for recovery of water containing silica
Disclosed are embodiments of a method and apparatus for the treatment of water containing silica in order to recover as much treated water from a water source as possible while minimizing the generation of waste products. Other embodiments include removing specific elements from the water source and utilizing those elements. Embodiments of the method and apparatus uses in-line physical and physio-chemical treatment methods to remove potential biological, colloidal and hardness foulants continually so that there is minimal loss of water from the water source stream and minimal addition of chemicals to accomplish removal or reduction of these potential recovery-limiting foulants.
1. A method of removing elements from feed water comprising the steps of
a) receiving feed water containing silica and hardness ions and at a natural pH of about 8.1,
b) treating the feed water with a weak-acid cation-exchange resin to reduce the hardness to less than 1 mg/L, followed by
c) treating with a 1 micron cartridge filter to reduce the SDI to less than 1.0,
d) further treating the treated feed water to a low-pressure reverse osmosis (RO) process at about 85% recovery,
e) injecting about 3.5 mg/L of a silica-specific antiscalant into the low-pressure RO reject stream,
f) treating the antiscalant-injected low pressure RO reject stream in a high-pressure RO system to obtain a final recovery of greater than 90%, with the final RO reject stream containing super-saturated silica at about 4 times the saturation level of silica in water.
2. The process of claim 1 wherein the recovery in the final RO reject stream is about 98%.