Thread Content
This post was last edited by hesonchang214 on 2020-3-16 at 11:45. In ultra-pure water production, the reverse osmosis system is very important; when using such a system, special attention must be paid to the pretreatment of the raw water. To prevent clogging of the reverse osmosis system, the raw water should be pre-treated to remove suspended solids and reduce its turbidity; in addition, sterilization should be carried out to prevent the growth of microorganisms. Since reverse osmosis has high requirements for suspended solids in the raw water, a pollution index based on water quality and the degree of suspension contamination is commonly used to assess water quality. This method essentially determines the degree of fouling of the reverse osmosis system by suspended solids in the water. The pollution index of water entering the reverse osmosis system should be no more than 5; the recommended value is generally less than 3. The pH value of the incoming water should also be taken into account during preprocessing. Various semi-permeable membranes have their optimal operating pH value; therefore, the pH of the feed water needs to be adjusted according to the requirements of the reverse osmosis membrane. The temperature of the incoming water should also be taken into account during preprocessing. The water permeability of the membrane increases as the water temperature rises, but excessively high temperatures accelerate the hydrolysis rate of the cellulose acetate membrane and soften the organic membrane, making it easier to compress. Therefore, for organic membranes, it is advisable to maintain the temperature within the range of about 20–40°C, while for composite membranes, the temperature should be kept within the range of about 5–45°C.