01 Nov 2024
How to extend the service life of reverse osmosis equipment?
Pretreatment and debugging of reverse osmosis equipment
The quality of pretreatment is the key to the stable operation of reverse osmosis equipment. When the water inlet of reverse osmosis equipment is groundwater, there is no problem with the pretreatment of quartz sand and activated carbon, but it is different when using surface water.
1. Reverse osmosis equipment pretreatment reagents The reagents used in the treatment include coagulants, flocculants, oxidants, reductants, scale inhibitors, etc., especially coagulants and scale inhibitors. The selection, dosage and even the method of drug preparation of these reagents will have a great impact on the operation of reverse osmosis.
Usually, we will pay attention to the detection of the iron content of the influent water. In fact, the high aluminum content in the influent water will also cause pollution of the reverse osmosis membrane. Aluminum pollution of membrane is caused by aluminum hydroxide precipitation. Aluminum hydroxide precipitation usually exists in the form of colloids. It is an amphoteric hydroxide with very low solubility in the pH range of 6.5-6.7. If the aluminum coagulation process is carried out at too high or too low pH, aluminum ions will enter the reverse osmosis device and cause pollution of the reverse osmosis membrane. Therefore, for the pretreatment system using aluminum salt as a coagulant, its pH value is best controlled at 6.5-6.7 to minimize the solubility of aluminum. Pay attention to timely adjust the dosage according to the water quality. If possible, regularly test the aluminum content in the pretreated water and control it below 0.05 mg/L.
In order to prevent scaling on the concentrated water side, we usually add scale inhibitors. The current scale inhibitors are compounded with some organic acids and organic phosphates to achieve the purpose of scale inhibition and dispersion. If improperly selected or controlled, these organic substances will foul the reverse osmosis membrane elements, and it will also become a breeding ground for bacterial microorganisms and bring greater harm to the operation of reverse osmosis.
2. Temperature
Perhaps everyone knows that temperature has a great influence on the flux of reverse osmosis membrane elements. Therefore, when calculating the water output, the temperature must be checked for comparison. Therefore, in places where the water temperature is low in winter, heating equipment will be designed in the reverse osmosis pretreatment system, which can effectively ensure that the reverse osmosis equipment can also achieve the designed output in winter.
In fact, the SiO₂ precipitation in the membrane element is also closely related to the inlet water temperature of the reverse osmosis device. The silica concentration in the concentrated water cannot exceed 100 mg/l at 25°C and cannot exceed 25 mg/l at 5°C. Therefore, when there is no heating equipment in the pretreatment system, in winter, it is necessary to pay close attention to the pollution of silica precipitates on the membrane elements, and strictly control the content of silica in the concentrated water, and its value cannot exceed the solubility at that temperature.
Operation and management of reverse osmosis equipment
1. Regular inspection of reverse osmosis equipment Regularly inspect and replace the filter element of the safety filter in time to prevent the particle contamination of the reverse osmosis membrane caused by leakage of the filter element due to installation or quality problems. When the inlet pressure difference of the safety filter is greater than 0.15MPa, the filter element should be replaced. Generally, it should be inspected once a month. The filter element should not be used for more than 6 months. During operation, it should also be checked frequently to see if there is enough gas in the safety filter to prevent air from entering.
Training of operators of reverse osmosis equipment
The level of operators' ability depends on whether they can timely discover and correctly deal with defects and hidden dangers in the system, which is an important factor affecting the operation of reverse osmosis equipment. Misoperation by operators is more harmful to the system, and damage to such membrane elements is often irreversible. The flushing work before and after the restart of the reverse osmosis equipment must be done well to prevent residual gas in the equipment from running under high pressure, forming air hammers that will damage the membrane, and the concentration of inorganic salts on the concentrated water side of the membrane is higher than that of the raw water, which is easy to scale and pollute the membrane.
2. Inspection of reverse osmosis membrane elements
(1) Generally, every six months (the time can be shortened if necessary), each set of reverse osmosis first and second stage membrane elements should be inspected.
(2) Open the end cover of the pressure vessel (use special tools and be operated by skilled technicians).
(3) Check whether there are mechanical impurities, metal oxide deposition, bacterial microbial growth, membrane element color changes, and membrane scaling in the water inlet section. (4) If necessary, the reverse osmosis membrane element can be pulled out for detailed inspection. When pulling out the water inlet membrane element, it must not be pulled out directly, but it must be pushed out of the pressure vessel according to the direction of water flow. The same applies to installation.
(5) Detailed records should be made after each inspection for comparison.
3. Calibrate each meter regularly to ensure the accuracy and reliability of the instrument.
4. Analyze and count the operation data of the reverse osmosis equipment regularly.
Operating pressure, recovery rate (or concentrated water discharge), SDI (pollution index) of the inlet water, pH, residual chlorine and temperature are the main operating control parameters of the reverse osmosis device; desalination rate, water production and pressure difference are the three main monitoring performance parameters. They must be strictly observed in operation management, and the operating conditions must not be changed at will. In particular, it is necessary to prevent the increase of recovery rate to increase water production, which will lead to scaling of the reverse osmosis membrane surface; to prevent continued operation when the SDI value exceeds the standard, which will lead to blockage of the reverse osmosis membrane; to prevent continued operation above the maximum allowable pressure difference, which will cause destructive damage to the membrane element.
If you want to buy water treatment equipment, please contact us
The quality of pretreatment is the key to the stable operation of reverse osmosis equipment. When the water inlet of reverse osmosis equipment is groundwater, there is no problem with the pretreatment of quartz sand and activated carbon, but it is different when using surface water.
1. Reverse osmosis equipment pretreatment reagents The reagents used in the treatment include coagulants, flocculants, oxidants, reductants, scale inhibitors, etc., especially coagulants and scale inhibitors. The selection, dosage and even the method of drug preparation of these reagents will have a great impact on the operation of reverse osmosis.
Usually, we will pay attention to the detection of the iron content of the influent water. In fact, the high aluminum content in the influent water will also cause pollution of the reverse osmosis membrane. Aluminum pollution of membrane is caused by aluminum hydroxide precipitation. Aluminum hydroxide precipitation usually exists in the form of colloids. It is an amphoteric hydroxide with very low solubility in the pH range of 6.5-6.7. If the aluminum coagulation process is carried out at too high or too low pH, aluminum ions will enter the reverse osmosis device and cause pollution of the reverse osmosis membrane. Therefore, for the pretreatment system using aluminum salt as a coagulant, its pH value is best controlled at 6.5-6.7 to minimize the solubility of aluminum. Pay attention to timely adjust the dosage according to the water quality. If possible, regularly test the aluminum content in the pretreated water and control it below 0.05 mg/L.
In order to prevent scaling on the concentrated water side, we usually add scale inhibitors. The current scale inhibitors are compounded with some organic acids and organic phosphates to achieve the purpose of scale inhibition and dispersion. If improperly selected or controlled, these organic substances will foul the reverse osmosis membrane elements, and it will also become a breeding ground for bacterial microorganisms and bring greater harm to the operation of reverse osmosis.
2. Temperature
Perhaps everyone knows that temperature has a great influence on the flux of reverse osmosis membrane elements. Therefore, when calculating the water output, the temperature must be checked for comparison. Therefore, in places where the water temperature is low in winter, heating equipment will be designed in the reverse osmosis pretreatment system, which can effectively ensure that the reverse osmosis equipment can also achieve the designed output in winter.
In fact, the SiO₂ precipitation in the membrane element is also closely related to the inlet water temperature of the reverse osmosis device. The silica concentration in the concentrated water cannot exceed 100 mg/l at 25°C and cannot exceed 25 mg/l at 5°C. Therefore, when there is no heating equipment in the pretreatment system, in winter, it is necessary to pay close attention to the pollution of silica precipitates on the membrane elements, and strictly control the content of silica in the concentrated water, and its value cannot exceed the solubility at that temperature.
Operation and management of reverse osmosis equipment
1. Regular inspection of reverse osmosis equipment Regularly inspect and replace the filter element of the safety filter in time to prevent the particle contamination of the reverse osmosis membrane caused by leakage of the filter element due to installation or quality problems. When the inlet pressure difference of the safety filter is greater than 0.15MPa, the filter element should be replaced. Generally, it should be inspected once a month. The filter element should not be used for more than 6 months. During operation, it should also be checked frequently to see if there is enough gas in the safety filter to prevent air from entering.
Training of operators of reverse osmosis equipment
The level of operators' ability depends on whether they can timely discover and correctly deal with defects and hidden dangers in the system, which is an important factor affecting the operation of reverse osmosis equipment. Misoperation by operators is more harmful to the system, and damage to such membrane elements is often irreversible. The flushing work before and after the restart of the reverse osmosis equipment must be done well to prevent residual gas in the equipment from running under high pressure, forming air hammers that will damage the membrane, and the concentration of inorganic salts on the concentrated water side of the membrane is higher than that of the raw water, which is easy to scale and pollute the membrane.
2. Inspection of reverse osmosis membrane elements
(1) Generally, every six months (the time can be shortened if necessary), each set of reverse osmosis first and second stage membrane elements should be inspected.
(2) Open the end cover of the pressure vessel (use special tools and be operated by skilled technicians).
(3) Check whether there are mechanical impurities, metal oxide deposition, bacterial microbial growth, membrane element color changes, and membrane scaling in the water inlet section. (4) If necessary, the reverse osmosis membrane element can be pulled out for detailed inspection. When pulling out the water inlet membrane element, it must not be pulled out directly, but it must be pushed out of the pressure vessel according to the direction of water flow. The same applies to installation.
(5) Detailed records should be made after each inspection for comparison.
3. Calibrate each meter regularly to ensure the accuracy and reliability of the instrument.
4. Analyze and count the operation data of the reverse osmosis equipment regularly.
Operating pressure, recovery rate (or concentrated water discharge), SDI (pollution index) of the inlet water, pH, residual chlorine and temperature are the main operating control parameters of the reverse osmosis device; desalination rate, water production and pressure difference are the three main monitoring performance parameters. They must be strictly observed in operation management, and the operating conditions must not be changed at will. In particular, it is necessary to prevent the increase of recovery rate to increase water production, which will lead to scaling of the reverse osmosis membrane surface; to prevent continued operation when the SDI value exceeds the standard, which will lead to blockage of the reverse osmosis membrane; to prevent continued operation above the maximum allowable pressure difference, which will cause destructive damage to the membrane element.
If you want to buy water treatment equipment, please contact us