1. Why do the seals in reverse osmosis equipment swell?

Reverse osmosis equipment in water treatment systems requires three types of sealing rings to achieve sealing and isolation between different sections of the membrane shell. To reduce installation resistance, clean water or glycerin should be applied to the surface of each sealing ring during system installation.

It should be noted that lubricants such as Vaseline or other petroleum-based oils should be used cautiously, otherwise it will cause cracking of the freshwater pipe, especially swelling of the sealing rings. The swelling of the sealing rings generally does not directly affect the operation of the system, but it will affect the reloading after the system is unloaded, that is, the swollen sealing rings are difficult to enter the slot during loading.

2. Is the water production of each component in the reverse osmosis equipment process consistent?

In reverse osmosis equipment, due to the pressure difference between the feed end and the concentrate end of the membrane element, that is, the transmembrane pressure drop, and because the salt concentration of each element is higher than that of the feed water, the osmotic pressure of each element's feed water continuously increases along the system process.

If the freshwater backpressure and osmotic pressure are ignored, the water production of each membrane element along the system process will be proportional to the difference between its working pressure and osmotic pressure, that is, the water production of each membrane element gradually decreases.

3. Does pH affect the removal rate and lifespan of the reverse osmosis membrane?

Reverse osmosis equipment is the main filtration process in water treatment equipment. When raw water enters the reverse osmosis membrane, will the pH value of the raw water cause damage to the reverse osmosis membrane? Generally speaking, the material of the reverse osmosis membrane is mostly composite membrane material. When this membrane material is used, if it is within the pH range specified by the product, generally 2-11, then the damage and impact of the pH value on the membrane itself is relatively small.

As for the effect of pH on the desalination rate of reverse osmosis, generally speaking, the pH value during normal operation should be close to neutral, that is, the pH value is around 7. This is because (1) the desalination rate of the reverse osmosis membrane is the highest at 7.5-7.8. (2) The equilibrium relationship of the carbonate system.

Therefore, pH still has a great impact on the desalination rate of certain impurities. Similarly, if the reverse osmosis membrane has zero removal rate for CO ₂ is zero, increase the pH value of the raw water, let CO ₂ convert to CO ₃ ^2- then the reverse osmosis membrane can effectively desalinate. However, the scaling problem of the reverse osmosis membrane should be paid special attention to at this time.

4. How should the reverse osmosis equipment be operated for the first time?

Use low pressure and low flow rate to remove the air in the pipeline. Only when the air in the pipeline is absent can the equipment operate normally. First, the pressure should be maintained between 0.2~0.4MPa. When using low-pressure flushing and venting, the generated concentrate and product water should be discharged into the sewer.

If the pressure rises rapidly during operation, there is air in the membrane element, which will generate a radial impact force of the water flow. In this case, the outer skin of the membrane may rupture, causing irreparable damage to the reverse osmosis membrane.

During the first use, the operating pressure of the membrane must be adjusted to 0.2~0.4MPa for flushing, and it must be ensured that the reverse osmosis system will automatically flush the reverse osmosis membrane at low pressure each time it starts.

5. How to replace the security filter element in the reverse osmosis equipment?

After a period of use, the water quality processed by the safety filter will change. At this time, the filter element will be clogged. The filter element should be replaced according to the pressure difference before and after the filter. When the pressure difference is greater than 0.03MPa, replacement should be considered.

Replacement method: Turn off the reverse osmosis system. Remove the pressure, press the button of the pressure relief valve on the equipment until the pressure gauge indicates zero. Use a professional wrench to rotate and open the filter bottle. Remove the old filter element and replace it with a new one. Use a professional wrench to rotate and tighten the filter bottle.

6. How to clean and disinfect the reverse osmosis system?

Generally, the cleaning of the reverse osmosis system requires professional technicians to perform, and customers cannot clean it themselves. If the reverse osmosis system needs to be cleaned, professional manufacturers should be contacted to complete it. The following conditions are prerequisites for chemical cleaning, which can be performed if they occur.

Prerequisites for chemical cleaning When the water production of the system is reduced by 5%-10% compared to the initial or last cleaning operation. When the desalination rate of the system is reduced by 2.5%-5% compared to the initial or last cleaning operation. When the pressure difference of each section of the system is 1-2 times that of the initial or last cleaning operation. Protect with protective solution when the system needs to be shut down for a long time.

7. Is the defluorination effect of reverse osmosis equipment good?

If people use excessive fluoride water, it will cause harm to the human body. In order to avoid people suffering from the harm of fluoride in life, reverse osmosis equipment can be used for defluorination. The fluoride ions in groundwater mostly come from the erosion and dissolution of surrounding rocks, and the water also contains a large number of soluble ions. When defluorination is carried out, the influence of defluorination on other molecules must be considered. The defluorination rate is not very high in groundwater with high salinity using reverse osmosis equipment. However, compared with other methods, the reverse osmosis method is simple to operate and has good treatment effect.

8. What are the basic requirements for the water quality of purified water equipment?

The purified water produced by purified water equipment is used in the pharmaceutical, biomedical and other industries. But what are the basic standards for purified water quality? The Chinese Pharmacopoeia and the European Pharmacopoeia both clearly point out that the raw water for pharmaceutical water must at least meet the standards of drinking water.

If it does not meet the standard, it should be purified first until it meets the standard. In addition to Escherichia coli, which has a clear regulation, other bacteria must not exceed 100/ml. In the process of producing water with purified water equipment, there will also be internal pollution, and various water treatment devices in purified water equipment may become pollution sources.

Therefore, it is essential to regularly clean and disinfect the purified water equipment. Additionally, a sterilization device should be installed at the end of the purified water equipment.

9. What are the characteristics of the water quality produced by the purified water equipment?

The water quality of the purified water produced by the purified water equipment meets the national hygiene standards and the actual production standards of the enterprise. The purified water produced by the purified water equipment has two characteristics.

One characteristic is that the number of disinfection and sterilization devices installed in the purified water equipment is gradually increasing; another characteristic is that the pipeline distribution system of the purified water equipment is replaced by a circulating pipeline instead of the traditional water supply pipeline. These two characteristics are to control microbial contamination and the increase of bacterial endotoxins.

At the same time, attention should also be paid to the influence of the flow rate in the pipe on the reproduction of microorganisms, that is, if the flow rate in the pipe is too low or blocked, it may cause the reproduction of microorganisms to increase, affecting the water quality.

10. What are the key points in choosing the installation location of the water softener?

The water softener has good water quality and stable system operation, and is used by many enterprises. When installing the water softener, the following points should be noted:

1) The water softener should be as close as possible to the drain.

2) If other water treatment equipment is needed, the installation location should be reserved.

3) Because salt is frequently added to the salt tank, a salt placement location should be set.

4) Do not install the water softener within 3 meters of the boiler, otherwise hot water will flow back into the water softener, causing damage.

5) Do not place the water softener in an environment where the room temperature is below 1°C and above 49°C.

11. What are the precautions for using the water softener?

The water softener is a water treatment equipment that removes Ca, Mg and other ions in the water, reduces the hardness of the water, and softens the water. After long-term use of the water softener, certain precautions should be followed.

1) When the water softener is in use, the inlet should be kept open, unless the equipment is under maintenance. If water is not needed, the outlet valve can be closed.

2) If the water quality is unqualified due to incomplete regeneration of the water softener, manual regeneration can be performed.

3) When the water softener is shut down for a long time, the brine should be sucked into the tank for protection.

4) When put back into use, just prepare the same brine as normal operation, open the inlet valve first, then connect the power supply, let the equipment reset itself, and then manually regenerate it once, and then the outlet valve can be opened.

5) If the industrial salt used is too dirty, the salt tank should be cleaned once a year to ensure the smooth progress of the salt absorption process.

12. What are the installation standards for ultrapure water equipment?

The ultrapure water equipment has good water quality and is suitable for the production needs of various enterprises, and its application range is gradually expanding. The installation standards for ultrapure water equipment are:

1) The equipment installation site should be chosen in a flat, clean environment, close to the power supply and water source.

2) Do not place it near a fire source or any heating body to avoid affecting its operating efficiency due to heat.

3) In northern areas, the equipment should not be installed outdoors to prevent the equipment from freezing and damaging the instruments and filter elements.

4) The equipment installation location should facilitate drainage and keep the equipment's drain pipe unobstructed.

5) The working pressure of the water pump used in the system should be ensured to be 1.0-1.2Mpa, ensuring that the water pump operates within its rated head range.

13. Booster pump, high-pressure pump does not suck water

Solution: If it is 380v voltage, check whether the booster pump and high-pressure pump are reversed. If reversed, change any two of the three power connection terminals of the pump. If not reversed, open the pump's vent valve to vent or fill it with water.

220v voltage booster pumps and high-pressure pumps will not reverse. Just open the pump's vent valve to vent or fill the pump body with water.

14. High-pressure pump does not start

Solution: Check whether the relay connected to the high-pressure pump is engaged, whether the wire terminals of the connecting plug are loose, detached, or whether the low water indicator light is on; if the low water indicator light is on, it means that the raw water source is not enough for the booster pump to use. In order to prevent the high-pressure pump from idling and damaging the high-pressure pump, a water shortage protector is used to cut off the power supply of the high-pressure pump, thus protecting the high-pressure pump. If sufficient water source is provided, the pressure of the water shortage protector reaches the working pressure requirement of the high-pressure pump, the water shortage protector indicator light goes out, and the high-pressure pump can be started.

15. The high-pressure pump makes an unusual noise

Solution: Check whether the high-pressure pump is idling. Sometimes, the high-pressure pump will make some unusual noises when the water has not completely entered. Usually, it will disappear automatically in 1 to 3 minutes. If it does not disappear after 3 minutes, open the vent valve of the high-pressure pump to vent or add water.

16. Pipeline Burst

Due to the poor water quality in some areas, there are many impurities, or because the velvet spray filter element has not been replaced and the RO membrane has not been cleaned for a long time, the RO membrane will be blocked, resulting in increased pressure in the pipeline, causing the pipeline to burst.

Solution: In this case, first check whether the velvet spray filter element needs to be cleaned or replaced, and then clean the RO membrane. Poor quality raw water will cause frequent blockage of the RO membrane. In this case, we should add ion exchange equipment or add scale inhibitors to the raw water to remove impurities in the water, thereby improving the water production quality and extending the service life of the RO membrane.

17. The water output is getting smaller and smaller

Some equipment users will find that the equipment's water output is getting smaller and smaller (this phenomenon basically does not occur in equipment using tap water as raw water). This is because some groundwater has poor water quality and many impurities, causing partial blockage of the RO membrane, thereby reducing the equipment's water output.

Solution: At this time, we should regularly backflush the pretreatment, replace the velvet spray filter element, clean the RO membrane, or replace the raw water from very poor quality groundwater with tap water (in the absence of tap water, it is better to configure a set of ion exchange antiscaling system, which will basically eliminate this phenomenon).

18. Fine white or black suspended particles appear in the purified water

This is caused by pipeline contamination, leading to bacterial growth.

19. Residual gas in the reverse osmosis equipment operates under high pressure, and the formation of water hammer will damage the membrane

There are usually two situations:

1) After the equipment is drained, when it is restarted, the gas is not completely discharged before rapid pressurization operation. The remaining air should be discharged at a pressure of 2-4 bar before gradually increasing the pressure.

2) When the joint between the pretreatment equipment and the high-pressure pump is not well sealed or leaks (especially the microfiltration and subsequent pipelines leak), the pretreatment water supply is insufficient. If the microfiltration is blocked, due to the vacuum, some air will be sucked in at the place where the seal is not good. In this case, the microfiltration should be cleaned or replaced to ensure that the pipeline does not leak.

In short, the pressure should be gradually increased when there are no bubbles in the flow meter. If bubbles are found during operation, the pressure should be gradually reduced to check the cause.

20. Incorrect shutdown method of reverse osmosis equipment damages the membrane

Two reasons:

2) Rinsing with pretreated water containing chemical reagents. Because water containing chemical reagents may cause membrane pollution during equipment shutdown.

Solution: When the reverse osmosis water treatment equipment is ready to shut down, stop adding chemical reagents, gradually reduce the pressure to about 3 bar, and rinse with pretreated water for 10 min until the TDS of the concentrate is very close to the TDS of the raw water.

21. Poor disinfection and maintenance of reverse osmosis equipment lead to microbial contamination

This is a common problem in the use of composite polyamide membranes, because polyamide membranes have poor chlorine resistance. If chlorine and other disinfectants are not added correctly during use, and users do not pay enough attention to the prevention of microorganisms, it is easy to cause microbial contamination. Many manufacturers' pure water microbial exceedances are caused by poor disinfection and maintenance.

Main manifestations: At the time of leaving the factory, the RO equipment did not use disinfectant maintenance; after the equipment was installed, the entire pipeline and pretreatment equipment were not disinfected; intermittent operation did not adopt disinfection and maintenance measures; the pretreatment equipment and reverse osmosis equipment were not disinfected regularly; the maintenance solution failed or the concentration was insufficient.

22. Poor residual chlorine monitoring of reverse osmosis equipment

Such as adding NaHSO ₃ Pump failure or reagent failure, or membrane damage due to residual chlorine when activated carbon is saturated.

23. Membrane performance damage caused by untimely cleaning and incorrect cleaning methods

During the use of the equipment, in addition to the normal attenuation of performance, the attenuation of equipment performance caused by pollution is more serious.

Common pollution of high-purity water equipment mainly includes chemical scaling, organic matter and colloid pollution, and microbial pollution. Different pollutions show different symptoms. Different membrane companies have some differences in the symptoms of membrane pollution.

In the project, we found that the duration of pollution is different, and the symptoms are also different.

For example: When the membrane is contaminated with calcium carbonate scale, when the pollution time is one week, the main manifestation is a rapid decrease in desalination rate, a slow increase in pressure difference, and no significant change in water production. Citric acid cleaning can fully restore performance. The pollution time is one year (a certain pure water machine), the salt flux increases from the initial 2mg/L to 37mg/L (raw water is 140mg/L～160mg/L), the water production decreases from 230L/h to 50L/h, and after citric acid cleaning, the salt flux decreases to 7mg/L, and the water production increases to 210L/h.

Furthermore, pollution is often not single, and its symptoms are also different, making pollution identification more difficult.

To identify the type of pollution, the raw water quality, design parameters, pollution index, operation records, equipment performance changes, and microbial indicators should be comprehensively judged:

1) Colloid pollution : When colloid pollution occurs, it is usually accompanied by the following two characteristics: A, the microfiltration filter in the pretreatment is blocked very quickly, especially the pressure difference increases quickly, B, the SDI value is usually above 2.5.

2) Microbial pollution : When microbial pollution occurs, the total number of bacteria in the permeate and concentrate water of the RO equipment is relatively high, and maintenance and disinfection have not been carried out according to the requirements.

3) Calcium scale : It can be judged according to the raw water quality and design parameters. For carbonate-type water, if the recovery rate is 75%, and scale inhibitors are added during design, the LSI of the concentrate should be less than 1; if no scale inhibitors are added, the LSI of the concentrate should be less than zero, and calcium scale will generally not be produced.

4) A 1/4-inch PVC plastic pipe can be inserted into the component to test the performance changes of different parts of the component.

5) Judge the type of pollution according to the changes in equipment performance.

6) Acid washing (such as citric acid, dilute HNO ₃ ), judge calcium scale according to the cleaning effect and cleaning solution, and further confirm through cleaning solution component analysis.

7) Chemical analysis of the cleaning solution Analyze three samples: raw water, cleaning solution, and cleaning liquid.

After determining the type of contamination, the membrane can be cleaned and then disinfected for use. If the type of contamination cannot be determined, 0.1% HCl (pH 3) cleaning is usually used.

Improper storage and maintenance lead to a decline in membrane performance.

New reverse osmosis membrane elements are usually soaked in 1% NaHSO ₃ and an 18% glycerol aqueous solution and stored in a sealed plastic bag. If the plastic bag is not broken, storage for about one year will not affect its lifespan and performance. Once the plastic bag is opened, it should be used as soon as possible to prevent NaHSO ₃ from oxidizing in the air and adversely affecting the element. Therefore, the membrane should be opened just before use.

After the reverse osmosis equipment is tested, the membrane can be protected using two methods: Run the equipment for two days (15-24h) and then use a 2% formaldehyde solution for maintenance; or run for 2-6h and then use a 1% NaHSO ₃ aqueous solution for maintenance (air should be drained from the equipment pipeline, ensuring that the equipment is leak-proof, and all inlet and outlet valves are closed).

Both methods can achieve satisfactory results. The first method is more expensive and is used when the equipment is idle for a long time, while the second method is used when the equipment is idle for a shorter time.