Failure Analysis of Reverse Osmosis System Operation


1. Failure caused by the deterioration of inlet water quality

In the initial design, the inlet water quality was good, so the operation of the RO Water System was stable. However, with the subsequent deterioration of inlet water quality, the reverse osmosis system had a serious operation failure when the system could not be optimized and improved by pretreatment.

Specific performance: water yield decays rapidly, operating pressure and pressure difference rise rapidly, etc.


2. Failure caused by attenuation of pretreatment performance

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

Specific performance: CMF or UF membrane breaks; Bacteria and microorganisms in buffer water tank multiply seriously; The filter in multi-media filter tank is disorderly or biased; The activated carbon filter in the tank is pulverized or microbial reproduction is serious.


3. Failure caused by using inferior filter element in filter housing

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

Specific performance:

The diameter of filter element is too small; The quality of filter element is poor, and the filtering accuracy can't meet the requirements; The filter element is not pressed tightly and easily deformed.


4. Faults caused by improper selection and dosing of scale inhibitor

As the "protector" of the safe and stable operation of RO System Manufacturer, scale inhibitor has become the mainstream at present with its excellent effect and low operating cost. But there are still many problems in scale inhibitor selection, dosing and mixing.

Specific performance:

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; Scale inhibitor metering box is seriously polluted.


5. Faults caused by improper addition of other chemicals

According to different water quality, it is necessary to add a certain amount and category of chemicals to increase the treatment effect of raw water. However, due to various reasons, some of these chemicals will have serious consequences if they are not used and added correctly.

Specific performance:

Inappropriate flocculants bring serious membrane fouling; Excessive addition of oxidant causes membrane oxidation; Excessive addition of reducing agent causes serious fouling of membrane.


6. Faults caused by device design defects and improper operation and maintenance

There are many problems in reverse osmosis drinking water system, some of which have defects in design, and some of which have some deviations in daily operation and maintenance, which cause serious hidden dangers in operation.

Specific performance:

A. In the initial design, the lift of high-pressure pump is low, and the water yield can't meet the design requirements when the temperature or water quality changes;

B. The membrane element is oxidized, resulting in the increase of water flux and the decrease of produced water quality;

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

D. The damage of O-ring causes the quality of produced water to decrease;

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

F. Overlapping or partial overlapping of the feed water thrust ring of the pressure vessel with the feed water outlet leads to high recovery rate and scaling phenomenon;

G. The length of the pressure vessel is too long, which causes the feed water to leak to the water-producing side, and the quality of the produced water decreases;

H. No pressure gauge between sections can reliably analyze and judge the reverse osmosis operation;

I. Large pressure difference causes the membrane element to produce telescope effect and be damaged;

J. The increase of back pressure of water production leads to the decrease of water production;

K. Unreasonable reverse osmosis arrangement leads to the increase of water flux of local membrane elements and the acceleration of pollution speed;

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

M. Particulate pollution causes serious mechanical fouling of membrane elements, resulting in a large pressure difference in the first stage, and deterioration of water yield and water quality;

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