Reverse osmosis, also known as reverse osmosis, is a membrane separation operation that separates the solvent from the solution using pressure difference as the driving force. Because it is opposite to the direction of natural osmosis, it is called reverse osmosis.

In the initial design, due to the good influent water quality, the system operation was relatively stable. However, with the subsequent deterioration of the influent water quality, when the system could not be optimized and improved in pretreatment, the reverse osmosis device produced more serious operational failures.

Specifically, the water production rate decay speed is faster, and the operating pressure and pressure difference increase faster.

Due to the deterioration of the pretreatment equipment performance, the turbidity, SDI value, COD value, etc. of the effluent seriously exceed the influent water quality requirements.

Specifically: CMF or UF membrane fiber breakage; serious breeding of bacteria and microorganisms in the buffer tank; disordered layers or skewed flow of filter media in the multimedia filter; pulverization or serious microbial reproduction of filter media in the activated carbon filter.

When the output of the security filter increases, the filter cartridge is easily deformed or the filtration accuracy does not meet the requirements, causing pollutants to directly enter the reverse osmosis device.

Specifically: the diameter of the security filter cartridge is too small; the quality of the filter cartridge is poor, and the filtration accuracy does not meet the requirements; the filter cartridge is not tightly pressed and is easily deformed.

Scale inhibitors, as the "protector" of the safe and stable operation of reverse osmosis, have become the mainstream of current scale inhibition methods due to their excellent effects and low operating costs. However, many problems have arisen in the selection, addition, and mixing of scale inhibitors.

Specifically: the performance of the scale inhibitor does not match the water quality; the performance of the scale inhibitor metering pump is unreliable; excessive dilution of the scale inhibitor; serious pollution of the scale inhibitor metering tank.

For different water qualities, a certain amount and type of chemicals need to be added to increase the treatment effect of the raw water. However, due to various reasons, the incorrect use and addition of these chemicals can sometimes have serious consequences.

Specifically: unsuitable flocculants cause serious membrane fouling; excessive addition of oxidants causes membrane oxidation; excessive addition of reducing agents causes serious membrane blockage.

At present, imported digital display instruments are generally used on reverse osmosis devices. Some instruments, under the premise of correct installation, display the flow rate very accurately and the readings are stable; however, other types of digital display instruments have a larger fluctuation range in the numerical value during operation, especially some instruments have parameter setting functions, and the displayed water production is controlled by human factors. In this way, the instrument that acts as the eyes of reverse osmosis will affect the technicians' judgment of reverse osmosis.

Specifically:

1. The display of concentrate flow rate is too large (actually smaller), causing the reverse osmosis recovery rate to be too high and scaling to occur;

2. The display of concentrate flow rate is too small (actually larger), causing the reverse osmosis recovery rate to be too low and pressure difference to occur;

3. The fluctuation of the flow meter reading is too large, and it is impossible to judge correctly according to the ratio of 10～15%.

There are many problems with reverse osmosis devices. Some systems have defects in design, while others have deviations in daily operation and maintenance, causing serious operational hidden dangers.

Specifically:

1. In the initial design, the head selection of the high-pressure pump is too low, causing the water production to not meet the design requirements when the temperature or influent water quality changes;

2. Membrane elements are oxidized, causing an increase in water flux and a decrease in water quality;

3. The brine seal is inverted or damaged, causing the actual recovery rate to be too high and causing scaling and water quality degradation;

4. O-ring damage causes a decrease in water quality;

5. Mixing new and old membrane elements and different types of membrane elements causes a decrease in system performance;

6. The brine stop ring in the pressure vessel overlaps or partially overlaps with the brine outlet, causing the recovery rate to be too high and causing scaling;

7. The length of the pressure vessel is too large, causing brine leakage to the product water side, causing a decrease in product water quality;

8. The inter-stage pressure gauge cannot reliably analyze and judge the operation of reverse osmosis;

9. A large pressure difference causes the membrane element to produce a telescope effect and damage;

10. Increasing the product water back pressure causes a decrease in product water volume;

11. Unreasonable arrangement of reverse osmosis causes an increase in water flux of local membrane elements and faster pollution speed;

12. Unreasonable design of reverse osmosis recovery rate and small number of membrane elements;

13. Particulate pollution causes serious mechanical blockage of membrane elements, large pressure difference in one section, and deterioration of water production and quality;

14. Pollutant deposition and bacterial and microbial pollution caused by system shutdown.