At present, the double-film process is commonly used for international industrial waste water recycling. This is because the RO reverse osmosis process can regenerate wastewater to extremely high quality and is suitable for all applications. In a typical design, the effluent water is first passed through the MF/UF system to remove particulate matter and larger colloids to reduce the fouling of the RO membrane, and also provides the opportunity to remove biological contamination such as bacteria and spores. The RO program is responsible for the removal of finer colloids and dissolved substances such as divalent ions and partially monovalent ions.
When a semipermeable membrane separates the solution from the pure solvent, the additional pressure, which is added to the solution and just enough to prevent the pure solvent from entering the solution, is called the osmotic pressure. Usually the higher the concentration of the solute in the solution, the higher the osmotic pressure. When the solution is not pressurized on one side, the pure solvent diffuses through the semi-permeable membrane to the side of the solution. This phenomenon is osmosis. On the contrary, if the pressure applied on the solution side exceeds the osmotic pressure, it can be in order to allow the solvent in the solution to flow to the pure solvent side, this process is called Reverse Osmosis.
- Ensure that the maximum SDI15 doesn't exceed 5.0;
- Guarantee turbidity below 1.0 NTU, strive for less than 0.2 NTU;
- Ensure that there is no residual chlorine or similar oxides;
- Ensure that there are no other chemicals that may cause membrane fouling or deterioration.
*Note: SDI value - one of the most important indicators for measuring Reverse Osmosis system influent
|Membrane pollution index||allowance||Solution|
|Suspended matter, etc.||Turbidity||<1 NTU||Filtration, coagulation sedimentation, microfiltration, ultrafiltration|
|Particulates||<100 / ml||Filtration, coagulation sedimentation, microfiltration, ultrafiltration|
|Microorganism||<1 per ml||Sterilization, microfiltration, ultrafiltration|
|Metal oxide||Iron, Fe3+||< 50 μg/L||Oxidation + precipitation or filtration|
|Manganese, Mn||< 50 μg/L||Use dispersants|
|Molecule||CaCO3||LSI<0||Recovery, pH, scale inhibitor|
|CaF2||<1.7 mg/L||Recovery rate|
|Organic matter||Oil||0||Floatation, adsorption|
|TOC||<10 mg/L||Activated Carbon, Filtration, Exchange Resin|
|COD||<10 mg/L||Activated Carbon, Filtration, Exchange Resin|
|BOD||<5 mg/L||Sterilization, microfiltration, ultrafiltration|
|Membrane Deterioration Index||allowance||Solution|
|pH value||3~10||Add acid or alkali adjustment|
|Oxidizer||Residual chlorine||<0.1 ppm||Reducing agent, activated carbon adsorption|
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