Patent ID: 6126834
Filing Date: 2000-10-03
Classification: B01D,C02F,Y10S

Abstract:
A control method for producing high purity product water using resistivity of product water, the method having the ability to produce high purity product water having a resistivity in the range of 0.8 to greater than 4 megohm-cm, the method comprising the steps of:(a) providing a feedwater to be purified;(b) providing a first reverse osmosis unit having a first high pressure side and a first low pressure side and having a first permeate produced at said first low pressure side;(c) monitoring the pH of said feedwater to be introduced to the high pressure side of said first reverse osmosis unit;(d) introducing said feedwater maintained at a temperature in a range of 45.degree. to 72.degree. F. to the high pressure side of said first reverse osmosis;(e) providing a second reverse osmosis unit having a second high pressure side and a second low pressure side for producing high purity product water;(f) passing the first permeate from the first reverse osmosis unit to the high pressure side of said second reverse osmosis unit;(g) measuring the resistance of said product water produced at said second low pressure side of said second reverse osmosis unit to provide a resistance measurement;(h) relaying said resistance measurement to a programmable logic controller;(i) in said programmable logic controller, comparing said resistance measurement with a previous resistance measurement to provide a comparison; and(j) in response to said comparison, maintaining or changing the pH of said feedwater upwardly or downwardly to produce said high purity water having said desired resistivity.