preface

Reverse osmosis, also known as reverse osmosis, is a membrane separation operation driven by pressure difference to separate solvent from solution. Because it is opposite to the direction of natural infiltration, it is called reverse osmosis.

Faults caused by poor inlet water quality

In the initial design, due to the good inlet water quality, the system operation is relatively stable. However, with the subsequent deterioration of inlet water quality, when the system cannot be optimized and improved for pretreatment, the reverse osmosis device has a serious operation failure.

Specific performance in

The water yield decreases rapidly, and the operating pressure and pressure difference rise rapidly.

Failure caused by performance degradation in preprocessing

Due to the poor performance of pretreatment equipment, the turbidity, SDI value and COD value of effluent seriously exceed the requirements of influent quality.

Specifically:

CMF or UF membrane filament is broken; Serious bacterial and microbial reproduction in buffer tank; The filter material of multi-media filter is disordered or biased; The filter material in the activated carbon filter is seriously powdered or microbial reproduction.

Failure caused by inferior filter element of security filter

When the output of the security filter increases, the filter element is easy to deform or the filtering accuracy cannot meet the requirements, so that the pollutants directly enter the reverse osmosis device.

Specifically:

The diameter of the filter element of the security filter is too small; The quality of filter element is poor, and the filtering accuracy can not meet the requirements; The filter element is not tightly pressed and is easy to deform.

Faults caused by improper selection and dosing of scale inhibitor

As the "protection god" for the safe and stable operation of reverse osmosis, scale inhibitor has become the mainstream of the current scale inhibition form because of its excellent effect and low operation cost, but there are many problems in the selection, dosing and mixing of scale inhibitor.

Specifically:

The performance of scale inhibitor does not match the water quality; The performance of scale inhibitor metering pump is unreliable; Excessive dilution of scale inhibitor; The scale inhibitor metering tank is seriously polluted.

Faults caused by improper dosing of other chemicals

For different water quality, a certain amount and category of chemicals need to be added to increase the treatment effect of raw water. However, due to various reasons, the improper use and addition of these chemicals will have serious consequences.

Specifically:

Unsuitable flocculant brings serious membrane pollution; Excessive addition of oxidant causes membrane oxidation; Excessive addition of reducing agent causes serious fouling and blockage of the membrane.

Failure caused by instrument failure

At present, imported digital display instruments are generally used in reverse osmosis devices. On the premise of correct installation, some instruments have very accurate flow display and stable reading; However, the value of other types of digital display instruments fluctuates greatly during operation. In particular, some instruments have the function of parameter setting, and the displayed water production is controlled by human factors. In this way, the instrument acting as the eye of reverse osmosis will affect the judgment of technicians on reverse osmosis.

Specifically:

1. Too large concentrated water flow display (actually small) causes too high reverse osmosis recovery rate and scaling;

2. The display of concentrated water flow is too small (actually large), resulting in too low reverse osmosis recovery rate and pressure difference;

3. The reading fluctuation of flowmeter is too large to judge correctly according to the proportion of 10 ~ 15%.

Faults caused by device design defects and improper operation and maintenance

There are many problems in reverse osmosis devices. Some systems have defects in design, and some have some deviations in the process of daily operation and maintenance, resulting in serious hidden dangers in operation.

Specifically:

1. In the initial design, the head selection of high-pressure pump is low, and the water yield fails to meet the design requirements when the temperature or inlet water quality changes;

2. The oxidation of membrane element causes the increase of water flux and the decline of produced water quality;

3. The actual recovery rate is too high due to the inversion or damage of brine seal ring, resulting in scaling and water quality decline;

4. The damage of O-ring causes the decline of produced water quality;

5. The mixed use of new and old membrane elements and different types of membrane elements leads to the decline of system performance;

6. The concentrated water thrust ring of pressure vessel overlaps or partially overlaps with the concentrated water outlet, resulting in excessive recovery rate and scaling;

7. The length of the pressure vessel is too long, which causes the concentrated water to leak to the water production side and reduces the water quality of the water production;

8. The operation of reverse osmosis cannot be reliably analyzed and judged without interstage pressure gauge;

9. The membrane element is damaged due to telescope effect due to large pressure difference;

10. The increase of water production back pressure causes the decrease of water production;

11. The unreasonable arrangement of reverse osmosis causes the increase of water flux and pollution speed of local membrane elements;

12. The design of reverse osmosis recovery rate is unreasonable, and the number of membrane elements is too small;

13. Granular pollution causes serious mechanical fouling of membrane elements, large pressure difference in one section, and poor water production and quality;

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