Common troubleshooting of reverse osmosis-Hezhong Environment (Beijing) Co., Ltd. was established in 2003

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Common troubleshooting of reverse osmosis

Published Time:

2022-09-22

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Before using the reverse osmosis equipment, check the machine's appearance for any abnormalities. After confirming everything is normal, you can connect the water and power sources. If the equipment malfunctions, try to find the root cause of the problem from these malfunction phenomena, so as to implement maintenance and other countermeasures as soon as possible.

RO membrane reverse osmosis system failures usually involve at least the following situations:

First, when the operating pressure and conductivity are normal, the water production decreases;

Second, the desalination rate decreases after standardization, which is manifested in the reverse osmosis system as an increase in the conductivity of the produced water;

Third, the water production decreases after standardization, and it is usually necessary to increase the operating pressure to maintain the rated water production, that is, the operating pressure increases;

1. Water production decrease after standardization If the RO system shows a decrease in water production after standardization, the cause can be found according to the following three situations:

(1) If the water production of the first stage of the RO system decreases, there is a deposition of particulate pollutants;

(2) If the water production of the last stage of the RO system decreases, there is scaling pollution;

(3) If the water production of all stages of the RO system decreases, there is blockage;

2. The decrease in water production after standardization is one of the most common system failures. The possible causes are:

(1) Reduction in membrane modules; operate according to the designed number of membrane modules;

(2) Low-pressure operation of the reverse osmosis membrane; operate below the designed reference pressure (there may be a throttle valve);

(3) Membrane module compaction; when the reverse osmosis membrane operates at a pressure far exceeding the reference pressure, membrane module compaction will occur, and the membrane module must be replaced;

(4) Decrease in operating temperature; operate at the design temperature of 25 degrees;

(5) Operation under high recovery rate conditions; this will increase the average feed water/concentrate TDS, thus increasing the osmotic pressure. When operating under a recovery rate of 75% or more, the amount of concentrate water decreases, thus increasing the concentration ratio of water in the membrane module, resulting in a serious decrease in feed water quality. Due to the increase in osmotic pressure of this feed water, the permeate volume decreases. In severe cases, salt scaling will precipitate on the membrane surface, and water must be produced at the design recovery rate;

(6) Membrane fouling. Metal oxides or impurities adhere to the membrane surface, causing blockage of the reverse osmosis membrane (the main cause).

(7) The pressure difference of reverse osmosis increases during operation. Improve the operation management of pretreatment, improve the water quality of reverse osmosis, and clean the reverse osmosis components with chemicals;

(8) Oil mixing. Note that oil must not enter the feed water; oil will contaminate the reverse osmosis membrane;

(9) Ensure that the filter cartridges are replaced regularly. Failure to replace them for a long time will cause the filter cartridges to become blocked, thus affecting the feed water volume of the reverse osmosis;

(10) Increase in feed water conductivity; this will increase the osmotic pressure that the produced water must overcome when passing through the membrane.

3. Solutions for increased conductivity

(1) First, confirm that all valves are opened correctly and that the ratio of pure water to concentrate is correct;

(2) Has the feed water conductivity increased? That is, has the feed water conductivity increased compared to before (e.g., during the Humen salt tide, the conductivity increased to 1000 μs/cm);

(3) Is the reverse osmosis membrane contaminated? Such as inorganic scaling CaSO4, MgSO4, BaSO4, organic pollution, metal oxide pollution, etc.;

(4) Has the reverse osmosis membrane come into contact with strong oxidants (such as Cl2), and been degraded by strong oxidants? Contact with any oxidizing substance will damage the membrane element;

(5) O-ring damage or leakage; O-ring leakage will cause the reverse osmosis effluent conductivity to rise rapidly;

(6) The reverse osmosis membrane comes into contact with strong oxidizing substances such as Cl2, O3, etc., and is oxidized and degraded by strong oxidizing substances.

4. Causes and solutions for decreased water production

(1) Is the RO reverse osmosis membrane contaminated or blocked;

(2) Increased feed water conductivity;

(4) Does the operating pressure reach the rated operating pressure of the reverse osmosis membrane? Determine the rated operating pressure according to the model of the reverse osmosis membrane. Appropriately increasing the feed water pressure can increase the water production.

(5) The raw water contains a certain concentration of suspended matter and dissolved substances. Suspended matter mainly includes inorganic salts, colloids, and biological particles such as microorganisms and algae. Dissolved substances mainly include easily soluble salts and sparingly soluble salts, metal oxides, acids and bases, etc. During the reverse osmosis process, the volume of feed water decreases, and the concentration of suspended particles and dissolved substances increases. Suspended particles will deposit on the membrane, blocking the water channels and increasing frictional resistance (pressure drop). When the sparingly soluble salts exceed their saturation limit, they will precipitate from the concentrate, forming scaling on the membrane surface, reducing the flux of the RO membrane, increasing the operating pressure and pressure drop, and leading to a decrease in product water quality.

(6) Influence of water temperature. The rated water production of the reverse osmosis membrane is based on a design of 25℃. For every 1℃ decrease in temperature, the water production decreases by 2-3%.