Common pollutants of reverse osmosis membrane and its removal method

Common pollutants and their removal methods:

1 Calcium carbonate scale

When the scale inhibitor addition system fails or the acid addition system appears to cause the pH of the feed water to rise, then calcium carbonate may be deposited. The occurrence of calcium carbonate scale precipitation should be detected as early as possible to prevent the growth of crystals from damaging the membrane surface If calcium carbonate scale is found early, it can be removed by reducing the pH of the feedwater to 3.0 to 5.0 for 1 to 2 hours. For calcium carbonate scale with longer settling time, RT-818A cleaning solution should be used for cyclic cleaning or overnight soaking.

Note: Make sure that the PH value of any cleaning solution is not lower than 2.0. The cup may damage the RO membrane element, especially when the temperature is high, and the highest pH should not be higher than 11.0. Check the use of ammonia to increase the pH, use sulfuric acid or hydrochloric acid to lower the PH value.

2 Calcium sulfate scale

The cleaning agent is the best way to remove calcium sulfate scale from the surface of the reverse osmosis membrane.

3 Metal oxide scale

The method of removing calcium carbonate scale described above can be used to easily remove the deposited hydroxide (such as ferric hydroxide).

4 Silica scale

For silicon scales that are not symbiotic with metallization or organic matter, they can only be removed by special cleaning methods. Please contact the company for detailed methods.

5 Organic deposits

Organic deposits (such as microbial slime or mildew stains) can be removed with a cleaning agent. In order to prevent reproduction, a sterilizing solution can be used to circulate and soak in the system. Generally, it takes a long time to soak to be effective. It is best to use disinfection treatment at the time, please consult with the company to determine the appropriate fungicide.

6 Cleaning solution

It is recommended to use RO membrane system cleaning agent when cleaning reverse osmosis membrane elements. It is very important to determine the chemical analysis of the pollutants before cleaning. Detailed analysis and comparison of the analysis results can ensure the selection of the best cleaning agent and cleaning method. The cleaning method and the cleaning effect obtained every time should be recorded. Provide the basis for finding the best cleaning method under water supply conditions.

All cleaning can be carried out at a maximum temperature of 40 degrees Celsius or below for 60 minutes. The amount of supplies required is calculated per 100 gallons (379 liters). When preparing the cleaning solution, add drugs and cleaning water in proportion, and use free chlorine. The reverse osmosis product water to prepare a solution and mix well.

During cleaning, the cleaning solution is circulated on the high pressure side of the membrane at a low pressure and a large flow rate. At this time, the membrane element is still installed in the pressure vessel and a special cleaning device is needed to complete the work.

General steps for cleaning reverse osmosis membrane elements:

1. Use a pump to pump clean, free chlorine-free reverse osmosis product water from the cleaning tank (or corresponding water source) into the pressure vessel and drain for a few minutes.

2. Prepare clean liquid in clean box with clean product water.

3. Circulate the cleaning fluid in the pressure vessel for 1 hour or a preset time. For an 8-inch or 8.5-inch pressure vessel, the flow rate is 35 to 40 gallons/minute (133 to 151 liters/minute), for a 6-inch pressure The vessel flow rate is 15-20 gallons/minute (57-76 liters/minute), and for 4-inch pressure vessels the flow rate is 9-10 gallons/minute (34-38 liters/minute).

4. After cleaning, drain the cleaning tank and rinse it, then fill the cleaning tank with clean product water for the next flush.

5. Use the pump to pump clean, free chlorine-free product water from the cleaning tank (or corresponding water source) into the pressure vessel and drain for a few minutes.

6. After flushing the reverse osmosis system, run the reverse osmosis system with the product water discharge valve open until the product water is clean, free of foam or cleaning agent (usually 15 to 30 minutes).

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