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Abstract

An adaptive control method for producing high purity water, the method having the ability to produce high purity water on a continuous basis having a resistivity in the range of 0.8 to 4 megohm-cm. The method comprises the steps of providing a feedwater to be purified and 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 the first low pressure side. The pH of the feedwater to be introduced to the high pressure of the first reverse osmosis unit is monitored before introducing the feedwater to the high pressure side of the first reverse osmosis unit. A second reverse osmosis unit is provided having a second high pressure side and a second low pressure side for producing high purity product water. The first permeate from the first reverse osmosis unit is passed to the high pressure side of the second reverse osmosis unit and the resistance of the product water produced at the second low pressure side of the second reverse osmosis unit is measured to provide a resistance measurement. The resistance measurement is relayed to a programmable logic controller where it is compared to previous resistance measurements to provide a comparison. In response to the comparison, the pH of the feed water is either maintained or is changed upwardly or downwardly to produce high purity water having the desired resistivity.

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First Claim