Reverse osmosis water treatment technology
Reverse osmosis process principle
The principle of reverse osmosis membrane separation technology is described by explaining the following professional terms:
1) Semi-permeable membranes: membranes that only allow the passage of solvent molecules but do not allow solute molecules to pass are called ideal semi-permeable membranes.
2) Penetration: Under the same external pressure, when the solution is separated from the pure solvent by a semi-permeable membrane, the phenomenon that the pure solvent passes through the semi-permeable membrane is a phenomenon that the solution is thinned, which is called infiltration.
3) Osmotic balance: During the permeation process, the number of solvent molecules passing through the semipermeable membrane from two opposite directions per unit time is equal to each other, ie, the osmotic equilibrium is reached.
4) Osmotic pressure: When the semipermeable membrane separates the solution from the pure solvent, the additional pressure added to the original solution to prevent it from just entering the solution is called the osmotic pressure. The more concentrated the solution, the greater the osmotic pressure of the solution.
5) Reverse osmosis: If the pressure applied to the solution exceeds the osmotic pressure, the solvent in the solution will instead flow to the pure solvent. This process is called reverse osmosis.
Technical characteristics of reverse osmosis process
1) The solute and water can be separated under the condition that the phase change does not occur at room temperature, which is suitable for the separation and concentration of heat-sensitive substances, and the energy consumption is lower than the phase change separation method.
2) The wide range of impurity removal can not only remove dissolved inorganic salts, but also remove various organic germanium impurities.
3) Higher salt removal rate and reuse rate of water can retain solute with particle size of more than a few nanometers.
4) Since only pressure is used as the driving force for membrane separation, the separation device is simple, easy to operate, self-controlled and maintained.
5) The reverse osmosis device requires that the influent water reaches a certain index before it can operate normally. The doctor must use certain pre-treatment measures before entering the reverse osmosis device. In order to prolong the service life of the membrane, it is also necessary to periodically clean the membrane to remove the dirt.
Typical process flow: The reverse osmosis system generally includes three main parts: pretreatment, reverse osmosis device, and post-treatment.
Reverse osmosis process flow
Similar to the microfiltration and ultrafiltration processes, good pretreatment is necessary for long-term stable operation of reverse osmosis devices.
Its main purpose is:
a. National removal of suspended solids and colloids to reduce turbidity;
b. Controlling the growth of microorganisms;
c. inhibiting and controlling the deposition of slightly soluble salts;
d. Adjustment of inlet temperature and pH;
e. removal of organic matter;
f. Precipitation control of old metal oxides and silicon;