1. What is the maximum allowable concentration of silica in reverse osmosis membrane influent?
The maximum allowable silica concentration depends on temperature, pH, and scale inhibitor. Usually the maximum allowable concentration at the concentrated water end is 100ppm without scale inhibitor. Some scale inhibitors can allow silica concentration in concentrated water up to 240ppm.
2. How does temperature affect the amount of water produced?
The higher the temperature, the higher the water yield, and vice versa. When operating under higher temperature conditions, the operating pressure should be lowered so that the water yield remains the same, and vice versa.
3. What is the effect of pH on removal rate, water yield and membrane life?
Reverse osmosis membrane products correspond to the pH range, generally 2 ~ 11, pH has little influence on the film performance itself, which is one of the significant characteristics different from other membrane products, but the characteristics of many ions in water are greatly affected by pH. Due to the same ion, the degree of charge is high, the removal rate of the membrane is high, the degree of charge is low or no charge, the removal rate of the membrane is low, so the pH has a great impact on the removal rate of some impurities.
4. Why is the pH of RO produced water lower than that of inlet water?
The best answer to this question can be found when the balance between CO2, HCO3 and CO3 is understood. In a closed system, the relative contents of CO2, HCO3 and CO3 change with pH. At low pH, CO2 is the dominant part, and in the moderate pH range, HCO3 is the dominant part. In the high pH range, CO3 is the main value. Since the RO film can remove dissolved ions but not dissolved gases, the CO2 content in the RO water is basically the same as that in the RO water, but HCO3 and CO3 can often be reduced by 1 ~ 2 orders of magnitude, which will break the balance between CO2, HCO3 and CO3 in the water. In a series of reactions, CO2 will combine with H2O for the following equilibrium transition until a new equilibrium is established.
5. What is the relationship between inlet TDS and electrical conductivity?
When the inlet conductivity value is obtained, it must be converted into a TDS value so that it can be input during software design. For most water sources, the conductivity /TDS ratio is between 1.2 and 1.7. For ROSA design, 1.4 ratio is used for seawater and 1.3 ratio is used for brackish water conversion. Generally, a good approximate conversion rate can be obtained.
