What are the 24 most common problems with reverse osmosis machine ?

1、Why do the seals in reverse osmosis machine swell?

Water treatment machine in reverse osmosis machine in order to achieve the membrane vessel between the zones of sealing isolation, the membrane vessel requires three types of sealing rubber ring. In order to reduce the installation resistance system should be installed in each seal ring surface coated with water or glycerin.
It should be noted that petroleum jelly or other petroleum-based grease lubricants should be used with caution, as they will cause cracking of the freshwater tubes and, in particular, swelling of the seals. The expansion of the rubber ring generally does not directly affect the operating effect of the system, but will affect the system after unloading and loading again, i.e., it is difficult to enter the tank when loading the expanded rubber ring.

2、Does the reverse osmosis machine process produce the same amount of water for each element?

In reverse osmosis machine, because of the pressure difference between the feed water end and the concentrated water end of the membrane element, that is, the membrane pressure drop, and because the salt content of the concentrated water of each element is higher than the salt content of the feed water, so the permeate pressure of the feed water of each element rises continuously along the system process.
If we ignore the fresh water back pressure and osmotic pressure, the water yield of each membrane element along the system process will be proportional to the difference between the respective working pressure and osmotic pressure, i.e. the water yield of each membrane element gradually decreases.

3、Does pH have any effect on the removal rate and life of the reverse osmosis membrane?

Reverse osmosis machine as the main filtration process in the water treatment machine, so in the raw water into the reverse osmosis membrane, the pH value of raw water will not bring harm to the reverse osmosis membrane, generally speaking, the material of reverse osmosis membrane is mostly composite membrane material, this membrane material in use if the pH value of the product according to the range, generally 2-11, then the pH value of the membrane itself to bring harm and influence is relatively small. The effect of pH on the membrane itself is less.
As for the effect of pH on the desalination rate of reverse osmosis membranes, it is affected by the properties of the ions in the water itself, which are determined by the acidity, alkalinity, decomposition, and charge of the ions themselves, all of which can lead to a reduction in the desalination rate of the membrane.
This shows that pH has a significant impact on the desalination rate of certain impurities. Similarly, if the CO2 removal rate of the reverse osmosis membrane is zero, increasing the pH of the raw water and converting CO2 to CO32- will allow the membrane to effectively desalinate. However, special attention should be paid to the scaling of the reverse osmosis membrane at this time.

4、How should the reverse osmosis machine operate when it first runs?

The air in the pipeline will be driven away by low pressure and low flow rate, only when the air in the pipeline does not exist can the equipment operate normally. First of all, the pressure should be kept between 0.2~0.4MPa. When using low pressure flushing and venting, discharge the thick and produced water to the sewer.
If the pressure rises quickly during operation, this is when the membrane element contains air, which will cause water flow and radial impact. This may cause the outer skin of the membrane to rupture, resulting in a non-repairable reverse osmosis membrane.
For the first time, be sure to adjust the pressure of membrane operation to 0.2~0.4MPa for flushing, to ensure that the reverse osmosis system will automatically flush the reverse osmosis membrane function at low pressure every time it is started.

5、How to replace the security filter core in a reverse osmosis machine?

After using the security filter for a period of time, the water quality processed will be different due to the long service life. The replacement of the filter cartridge should be based on the pressure difference between the front and rear of the filter, and should be considered when the pressure difference is greater than 0.03MPa.
Replacement method: Turn off the reverse osmosis system. Remove the pressure and press the button of the pressure relief valve on the equipment until the indication on the pressure gauge is zero. Open the filter bottle of the filter with a professional wrench rotary type. Pull out the old filter cartridge and replace it with a new one. Use a professional wrench to tighten the filter bottle of the filter by rotation.

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

Generally for the reverse osmosis system cleaning requirements are professional technicians to carry out, customers are not able to clean their own, if the reverse osmosis system needs cleaning should contact professional manufacturers to complete. The following conditions are the prerequisites for chemical cleaning, and if they occur, cleaning can be carried out.
Chemical cleaning prerequisites: the system’s water production is 5-10% lower than at the beginning or at the last operation cleaning. When the desalination rate of the system is 2.5-5% lower than the initial or the last operation cleaning. When the pressure difference of each section of the system is 1-2 times that of the initial or last operation cleaning. When the system needs to be protected by a protective solution during long-term shutdown.
Note: Water production and desalination rate will be affected by the water temperature, so the test results should be in the case of the same water temperature results.

7、Is the fluoride removal effect of reverse osmosis machine good?

If people use super fluoride water, it will cause harm to human body. In order to avoid people suffering from fluoride in their lives, reverse osmosis machine can be used to remove fluoride. Most of the fluoride ions in groundwater come from the dissolution of the surrounding rock erosion, and there are also a large number of soluble ions in the water, so the impact of fluoride removal on other molecules must be considered when fluoride removal is carried out. The removal rate of fluoride in groundwater with excessive salt content is not too high using reverse osmosis machine. But the reverse osmosis method and compared with other methods, it is easy to operate, the treatment effect is good.

8、What are the basic requirements of ultra-pure water machine water quality?

Ultra-pure water system to make purified water in the pharmaceutical, biological medical and other industries. But what is the basic standard of ultra-pure water quality? The Chinese Pharmacopoeia and the European Pharmacopoeia both clearly state that the raw water for pharmaceutical water should at least meet the standard of drinking water.
If it does not meet the standard, it is first evolutionary treatment until it meets the standard. In the process of water purification equipment, there will be internal pollution, ultrapure water system in a variety of water treatment devices may become a source of pollution.
Therefore, we must often clean and disinfect ultrapure water equipment, in addition, the end of ultrapure water system should also be installed sterilization device.

9、What are the characteristics of ultra-pure water system water quality?

Ultra-pure water system to produce water quality in line with national health standards, in line with the actual production standards of enterprises. Ultra-pure water system water – purified water has two characteristics. One feature is the gradual increase in the installation of ultra-pure water system for disinfection and sterilization.
Another feature is that the pipeline distribution system of ultra-pure water system by the circulation pipeline instead of the traditional water supply pipeline, both of these features are to control microbial contamination and the increase of bacterial endotoxin.
At the same time, attention should also be paid to the impact of the flow rate in the pipe on the reproduction of microorganisms, that is, the flow rate in the pipe is too low or blocked, it may cause an increase in the reproduction of microorganisms, affecting water quality.

10、What are the key points in the selection of the installation location of water softening plant?

water softening plant has good water quality and stable system operation, and is used by many enterprises. While installing water softening plant, the following points should be noted:
1) Water softening equipment should be as close as possible to the drainage.
(2) If other water treatment machine is required, the installation location should be reserved.
(3) Due to the regular addition of salt to the salt tank, should be set up to put the salt in place.
(4) Do not install the water softening plant within 3 meters from the boiler, otherwise the hot water will flow back into the water softening plant and cause damage.
(5) To place the water softening plant in an environment where the room temperature is below 1°C and above 49°C.

11、What are the precautions for the use of water softening plant?

water softening plant is to remove Ca, Mg plasma in water, reduce the hardness of the water, so that the water softening water treatment plant. water softening plant after a long time of use, to follow certain precautions.

(1) water softening plant in the use of water inlet should be open for a long time, unless it is necessary to close in the case of equipment maintenance. If you do not need water, you can close the water valve.

(2) If the water softening plant regeneration is incomplete resulting in water failure can be manually regenerated.

3） When the water softening plant is out of use for a long time, the brine needs to be sucked into the tank for protection.

(4) when put into use again, just prepare and work as normal brine, first open the inlet valve, and then connected to the power supply, let the equipment reset itself and then manually regenerate once after the completion of the water valve can be opened.

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

12、What are the installation standards for ultrapure water machine?

The water quality of ultrapure water machine is good, suitable for the production needs of various types of enterprises, and the scope of use is gradually expanding. This article mainly introduces the installation of ultrapure water machine when the standard description.

(1) equipment installation site should be selected in the flat, clean environment, close to the power supply, water supply environment.

(2) Do not approach the fire source and any heat generator to avoid heat affecting the efficiency of its operation.

3） Do not install the equipment outdoors in cold places to prevent the equipment from freezing inside and damaging the instruments and filtering elements.

4) The equipment should be installed in a position that allows for easy drainage, so that the drainage pipe of the equipment is kept smooth.

(5) The working pressure of the pump used in the system should be ensured at 1.0-1.2Mpa to ensure that the pump works within its rated head.

13、Booster pump, high-pressure pump does not absorb water

Solution: If the voltage is 380v, check whether the booster pump, high pressure pump is reversed, if found reversed, the three power terminals of the pump should be switched to any two, such as not reversed need to open the exhaust valve of the pump or filled with water.

220v booster pump, high pressure pump will not reverse the phenomenon, as long as the pump exhaust valve to open the air or fill the pump body with water.

14、High pressure pump does not start

Solution: Check whether the relay docked with the high-pressure pump is sucked, the wire of the wiring plug is not loose, off or underwater indicator light; such as water shortage indicator light, indicating that the original water source is not enough booster pump, in order not to make the high-pressure pump idle and thus damage the high-pressure pump, so use the water cut-off protector to cut off the high-pressure pump power, thus playing a role in protecting the high-pressure pump. If you provide sufficient water, so that the water cut-off protector pressure to reach the working pressure requirements of the high-pressure pump, the water cut-off protector light off, you can start the high-pressure pump.

15, high-pressure pump makes a strange noise

Solution: Check whether the high-pressure pump is idling, sometimes the high-pressure pump in the water is not fully entered will make some strange sound, usually in 1 ~ 3 minutes automatically disappear, such as in the case of 3 minutes after the disappearance, the high-pressure pump exhaust valve should be opened, bleeding or water injection.

16、Pipe bursting

Solution: Due to the poor water quality in some areas, more impurities, or due to a long time without replacing the velvet spray cartridge and cleaning RO membrane, will lead to RO membrane blockage, resulting in high pressure in the pipe, resulting in pipe bursting.

In this case, you should first check whether the velvet spray cartridge needs to be cleaned or replaced, and then clean the RO membrane. Poor quality raw water will lead to RO membrane often clogged, at this time we should add ion exchange equipment or add scale inhibitor in raw water to eliminate impurities in the water, so as to improve the quality of water production, increase the service life of the RO membrane.

17, the water output is getting smaller and smaller

Solution: Some equipment users will find that the equipment output is getting smaller and smaller (using tap water for raw water equipment basically does not appear this phenomenon), this is because some groundwater quality is poor, more impurities, resulting in partial clogging of the RO membrane, so that the equipment output is reduced.

At this time we should regularly backflush the pretreatment, velvet spray cartridge for replacement, RO membrane cleaning, or the raw water from the poor quality of groundwater replaced with tap water (in the absence of tap water in the case of good configuration of a set of ion exchange scale inhibition system, basically will eliminate the occurrence of such phenomena).

18、Pure water with fine white or black suspended particles

Solution: This is because the pipeline is contaminated, resulting in the growth of bacteria. This situation should be dissolved caustic soda into the precision filter, the operation of the regulating valve to turn off the waste water, pure water to a high point, start the high-pressure pump, the pure water outlet outflow into the precision filter to circulate the water for about 30 minutes. Equipped with a pipeline disinfection machine equipment should be opened in time to disinfect the pipeline disinfection machine for pure water pipeline.

19, reverse osmosis machine has residual gas running under high pressure, the formation of gas hammer will damage the membrane

There are two situations that often occur:

(1) after the equipment is emptied, re-running, the gas is not exhausted on the rapid ramp-up operation. The remaining air should be exhausted at a pressure of 2 to 4 bar, and then gradually increase the pressure.

(2) When the joint between the pretreatment machine and the high-pressure pump is not sealed well or leaked (especially the microfilter and the pipeline after it is leaked), when the pretreatment water supply is not sufficient, such as the microfilter is blocked, the vacuum will absorb some air in the place where the seal is not good. Should clean or replace the microfilter, to ensure that the pipeline does not leak.

In short, there should be no bubbles in the flowmeter to gradually increase the pressure of the operation, the bubbles found in the operation should gradually reduce the pressure to check the cause.

20, reverse osmosis machine shutdown incorrect method of damage to the membrane

(1) shutdown when the rapid depressurization is not thoroughly flushed. As the concentration of inorganic salts on the thick water side of the membrane is higher than that of the raw water, it is easy to scale and contaminate the membrane.

2) Flushing with pretreatment water with chemical reagents. Because the water containing chemical reagents may cause membrane contamination during equipment shutdown.

Reverse osmosis water treatment equipment in preparation for shutdown, should stop adding chemical reagents, and gradually lower the pressure to about 3 bar with pretreatment water rinse 10min, until the TDS of concentrated water and the original water TDS is very close.

21, reverse osmosis machine disinfection and maintenance is not effective, resulting in microbial contamination

This is a common problem in the use of composite polyamide membrane, because the polyamide membrane residual chlorine resistance is poor, in the use of chlorine and other disinfectants are not properly added, coupled with the user’s prevention of microorganisms do not pay enough attention to the microbial contamination, easily lead to microbial contamination. Many manufacturers produce pure water microorganisms exceed the standard, is the disinfection, maintenance is not enough to cause.

The main performance is: factory, RO machine does not use disinfectant maintenance; equipment installed after the entire pipeline and pretreatment machine disinfection; intermittent operation does not take disinfection and maintenance measures; no regular disinfection of pretreatment machine and reverse osmosis machine; maintenance solution failure or insufficient concentration.

22、Reverse osmosis machine residual chlorine monitoring is not effective

If the pump of NaHSO3 fails or the liquid fails, or the membrane is damaged by residual chlorine when the activated carbon is saturated.

23、Incorrect cleaning and cleaning methods lead to damage of membrane performance

Equipment in the process of use, in addition to the normal decay of performance, the decay of equipment performance due to pollution is more serious.

EDI high-purity water equipment usually pollution are mainly chemical scale, organic and colloidal contamination, microbial contamination, etc.. Different contaminants show different symptoms. The symptoms of membrane contamination also vary from one membrane company to another.

In the project, we found that the symptoms of contamination are not the same as the duration of contamination.

For example, if the membrane is contaminated with calcium carbonate scale, the main symptoms are rapid decrease of desalination rate, slow increase of pressure difference, and no significant change of water production, and complete recovery of performance by citric acid cleaning. Pollution time for a year (a pure water machine), salt flux from the initial 2mg / L rose to 37mg / L (the original water for 140mg / L ~ 160mg / L), water production from 230L / h down to 50L / h, after cleaning with citric acid, salt flux down to 7mg / L, water production rose to 210L / h.

Furthermore, pollution is often not a single, the symptoms of its performance also have some differences, making the identification of pollution more difficult.

Identify the type of pollution to be integrated raw water quality, design parameters, pollution index, operating records, equipment performance changes and microbial indicators to determine:

(1) colloidal contamination: colloidal contamination occurs, usually accompanied by the following two characteristics: A, pre-treatment in the microfilter clogged very quickly, especially the differential pressure increases quickly, B, SDI value is usually above 2.5.

(2) Microbial contamination: When microbial contamination occurs, the total number of bacteria in the permeated water and concentrated water of RO machine is relatively high, and usually must not be maintained and disinfected as required.

(3) calcium scale: can be judged according to the raw water quality and design parameters. For carbonate-type water, if the recovery rate is 75%, when the design is added scale inhibitor, the LSI of the concentrated solution should be less than 1; when no scale inhibitor is added, the LSI of the concentrated solution should be less than zero, and generally no calcium scale will be produced.

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

(5) Judging the type of contamination according to the change of equipment performance.

6）Acid cleaning (such as citric acid, dilute HNO3) can be used to judge the calcium scale according to the effect of cleaning and cleaning fluid, which is further confirmed by the analysis of cleaning fluid composition.

(7) chemical analysis of the cleaning fluid: take the original water, cleaning fluid, cleaning fluid, three sample analysis.

After determining the type of contamination, can be cleaned according to the method in Table 1, and then disinfected and used. When the type of contamination can not be determined, usually use the cleaning (3) disinfection 0.1% HCl (pH 3) step cleaning.

24, improper storage and maintenance methods lead to the decline of membrane performance

The new reverse osmosis membrane element is usually moistened with 1% NaHSO3 and 18% glycerin solution and stored in a sealed plastic bag. In the case of plastic bags do not break, storage for about 1 year, will not affect its life and performance. When the plastic bag is opened, it should be used as soon as possible to avoid adverse effects on the components due to the oxidation of NaHSO3 in the air. Therefore, the membrane should be opened before use as much as possible.

After the commissioning of the reverse osmosis machine, we have used two methods to protect the membrane. After two days of commissioning (15~24h), we use 2% formaldehyde solution for maintenance; or after 2~6h of operation, we use 1% aqueous solution of NaHSO3 for maintenance (we should exhaust the air in the pipeline of the equipment to ensure that the equipment does not leak and close all the import and export valves).

Both methods can get satisfactory results. The first method is more costly and used when idle for a long time, and the second method is used when idle for a shorter time.