What are the reasons for the decline in the operating performance of high-purity water systems?

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　　I. The inlet water pressure affects the desalination efficiency and recovery rate of the reverse osmosis membrane. The water pressure of the feed water in ultra-pure water production systems has little impact on the desalination efficiency; however, an increase in inlet water pressure leads to an increase in the net pressure across the reverse osmosis membrane. An increase in the net pressure of reverse osmosis leads to an increased volume of water passing through the membrane, while the desalination efficiency of the membrane remains unchanged. As a result, the increased water output dilutes the amount of salts that pass through the membrane, thereby improving its desalination efficiency. However, when the inlet water pressure exceeds the specified value, the high recovery rate of the reverse osmosis membrane increases the salt content in the water, raising the desalination pressure and leading to an increase in the amount of salts that pass through the membrane. Prolonged instability in the inlet water pressure can significantly affect the performance and quality of operation of the reverse osmosis membrane. 　　II. Reverse osmosis membranes are sensitive to changes in the temperature of the feed water. As the temperature of the feed water increases, the reverse osmosis membrane allows more water to pass through it. Based on the principle of thermal expansion and contraction, the conductivity of the water produced by the reverse osmosis membrane is highly sensitive to changes in water temperature. Every increase of one degree in water temperature leads to an increase in the amount of permeation; therefore, the temperature of the incoming water must be kept within the optimal range, as higher temperatures are not recommended. 　　III. The pH value of the feed water also affects the desalination efficiency of the reverse osmosis membrane. Although the pH value of the feed water has little impact on the water production capacity of the reverse osmosis membrane, it does have a significant effect on its desalination efficiency. Only when the inlet water pH is maintained between 7.5 and 8.5 can the desalination efficiency of the reverse osmosis membrane be optimal.