Reverse osmosis membrane 5"phenomena", how to form?
Reverse osmosis is a water treatment process that developed rapidly in the 1960s. At present, it has been used in urban water, boiler recharge water, power plant boiler recharge water, industrial wastewater and seawater desalination and solute separation in various solutions. The working principle of reverse osmosis membrane is to separate the solvent in the solution by the pressure as the driving force, which has a good application in the food, electronics, medicine, printing and dyeing industries, and some problems will inevitably occur in the long-term use process. How are some of the "phenomena" in the application process of reverse osmosis membrane formed?
1. Scaling phenomenon
Users in the use of pure water equipment, occasionally there will be problems, such as reverse osmosis membrane scaling, pure water equipment joint leakage. At first, I don't care much, but as time goes on, the problem will become more and more serious. The following with the small series to look at the reasons for reverse osmosis membrane scaling.
First of all, when the purified water equipment is in operation, fresh water will be produced during the low-pressure washing process, and the concentration of water on both sides will naturally deepen, and it will also lead to the deepening of the concentration of salt, which contains a large amount of precipitation over time, there will be scaling.
Secondly, uneven dosing is also an important reason for scaling of reverse osmosis membranes. If the scale inhibitor device leakage is more serious, it is likely to affect the dosage of scale inhibitor. The staff did not pay enough attention in the operation process, and many times they did not wash in time during the shutdown process, which will also lead to scaling of the reverse osmosis membrane.
2. Oxidation phenomenon
The oxidation phenomenon of reverse osmosis membrane is also a phenomenon that is easy to appear in the process of using reverse osmosis membrane, and the oxidation phenomenon will inevitably affect the performance. Several common reverse osmosis membrane oxidation phenomena:
Residual chlorine attack: chlorine-containing fungicides are added to the water in the reverse osmosis system, and after pretreatment, they are not completely consumed, but enter the reverse osmosis system, and oxidation will occur. The small amount of residual chlorine and the heavy metal ions in the influent have catalytic oxidation reaction in the desalting layer. The reverse osmosis membrane uses oxidizing fungicides other than residual chlorine in the water treatment process, such as chlorine dioxide, potassium permanganate, ozone, hydrogen peroxide, etc., which will cause oxidation.
In the process of use, we should take some measures to prevent the oxidation of the reverse osmosis membrane, first of all, to ensure that the reverse osmosis membrane does not contain residual chlorine in the water: generally before the water will be tested, through some instruments to reverse test, to ensure that there is no residual chlorine use. When taking bactericidal measures, the appropriate bactericide should be selected, and the reverse osmosis membrane system should also be cleaned separately from other configuration systems.
3. Rupture phenomenon
If the back pressure of the water producing end of the reverse osmosis membrane is encountered, the diaphragm will be separated, damaged and other problems. If the back pressure of the water producing end is not prevented, the bursting film can be installed on the water producing side. When the back pressure of the water producing end rises to the bursting limit pressure of the bursting film due to poor pipeline and closed valve, etc., the bursting film will be damaged, and a new bursting film can be replaced.
4. Pollution phenomenon
Reverse osmosis device in operation for a period of time, because the water pollutants will pollute the filtration equipment,RO membrane is the core technology of reverse osmosis work, in order to quickly determine whether the reverse osmosis device is contaminated, it is necessary to master the pollution phenomenon and state of reverse osmosis.
Membrane degradation: Degradation of cellulose acetate membrane elements due to low or high PH values caused by hydrolysis of Hyde's reverse osmosis membrane elements, oxidation (such as various oxidants), and mechanical damage, such as water compression, film protrusion, overheating, wear due to fine carbon or sand materials, can cause degradation of reverse osmosis membrane elements.
Sediment deposition: If insufficient measures are taken or adequate measures are taken improperly, sediment deposition can be caused, common sediments include carbonate scale, sulfuric acid scale, silicon scale, etc.
Colloidal deposition: Colloidal deposition is generally caused by metal oxides and various other colloids.
Organic deposition: Natural organic matter, oil, excessive scale inhibitor and iron precipitation, excessive cationic polymer (from pre-treated filters) are the root cause of organic matter.
Biological contamination: Microorganisms will form biological slime on the surface of the Hyde reverse osmosis membrane element, and bacteria will cause erosion of the acetate cellulose membrane, these microorganisms include algae, fungi, etc.
5. Telescope phenomenon
When doing the appearance inspection of reverse osmosis membrane, it mainly includes visual appearance inspection and component quality weighing. Visual inspection is to observe and record in detail the contamination and wear of the end cap, end face, film roll, outer wound glass steel, center pipe, sealing ring and other parts of the membrane element, and determine whether there is a "telescope" phenomenon through inspection.
So, speaking of this, there must be a lot of people to ask, how did reverse osmosis membrane become a "telescope"? In fact, the "telescope" phenomenon of reverse osmosis membrane is a mechanical damage, the outer envelope of the membrane element and the membrane element staggered and moved downstream, sometimes even on the next membrane element. A slight "telescope" phenomenon will not necessarily damage the membrane element, but in severe cases, it may cause adhesive wiring and rupture of the diaphragm.
The so-called "telescope phenomenon" refers to the fact that the pressure difference between the reverse osmosis inlet side and the concentrated water side exceeds the limit value, causing the diaphragm and the diaphragm in the reverse osmosis membrane element, the diaphragm and the center tube to slip, forming the membrane element with one end of the diaphragm concave and one end of the diaphragm protruding, similar to the appearance of a telescope.
The 8-inch membrane element is more prone to this phenomenon because of the larger membrane cross-section area. It is necessary to ensure that a stress ring is installed in the membrane pressure vessel to support the 8 inch membrane element's outer envelope. The smaller diameter membrane element is supported by its production pipe and its stress absorber to prevent the outer envelope from slipping. After the telescope phenomenon occurs, the damaged membrane element should be replaced with a new element and the cause should be eliminated.
Where there is effect, there is cause, and what is the cause of this "telescope" phenomenon?
First of all, the installation or disassembly is not in accordance with the requirements, resulting in relative dislocation between the reverse osmosis membrane and the membrane;
Secondly, the rigid strength of the membrane shell is not enough, and the membrane shell is deformed when the pressure is applied.
Another important reason is that the water inlet pressure of the system rises too fast when the high pressure pump is started.
