Reverse osmosis membrane separation technology (referred to as RO technology) is a new and practical water treatment technology. For a specific reverse osmosis system, the long-term stability of its performance is indispensable. The success of the long-term performance of the reverse osmosis system depends on normal operation and maintenance, including the commissioning of the entire system, start-up and shutdown, cleaning and maintenance, etc., membrane fouling and scale prevention, etc.

So, how to ensure the normal operation of the RO system, and what problems should we pay attention to?

First, the first start 

( 1) Before starting the start-up procedure, fully clean the pretreatment part to flush out impurities and other contaminants, and prevent unqualified water from being injected into the membrane element.

( 2) When there is water in the original water tank, open the upper inlet valve and lower exhaust valve of the mechanical filter, and turn on the power supply of the original water pump. At this time, the metering pump will automatically add medicine, the water will enter the mechanical filter from the upper inlet valve, and the lower exhaust valve will be discharged. After the water is clear, open the upper inlet valve and lower outlet valve of the activated carbon filter, the outlet valve of the mechanical filter, and close the lower outlet valve of the mechanical filter. At this time, the water enters the activated carbon filter, and the pollution index of the effluent from the mechanical filter is tested. At the same time, the activated carbon filter emits water. After cleaning, the RO host opens the concentrated water valve, and the pure water is discharged.

( 3) Open the water inlet valve of the RO system, close the lower drain valve of the activated carbon filter, and let the low-pressure and low-flow water flush out the air in the element and the pressure vessel, so that the pressure is 0.2-0.4MPa, and at the same time, open the exhaust valve of the security filter to discharge run out of air

( 4) During the flushing operation, check all pipeline joints and valves for leaks;

( 5) After flushing for a few minutes, after the air is removed, turn on the high-pressure pump, run at low pressure for a few minutes, and then gradually close the return water valve and the concentrated water discharge valve, so that the pressure rises slowly until the ratio of fresh water and concentrated water is close to the design ratio, but Do not exceed, and make the pressure not exceed the design upper limit;

( 6) After the operation is stable and the conductivity of the produced water meets the requirements, open the water inlet valve of the pure water tank, close the pure water discharge valve, and put the qualified water into the pure water storage tank. 

2. Regular startup

Once the RO system starts to operate, it should continue to operate in a stable condition in theory. In fact, the RO system needs to be shut down and started frequently. Every start and close cycle involves changes in pressure and flow. Therefore, Mechanical stress is caused to the membrane element, so try to reduce the number of opening and closing times. At the same time, the smoother the normal start-up procedure, the better. In principle, it should be the same procedure as the first start-up. The most important thing is that the water inlet pressure should rise slowly.

3. Normal shutdown

When closing the RO system, gradually open the high-pressure concentrated water valve before the high-pressure pump is closed, and it is strictly forbidden to suddenly depressurize, and then flush with permeate or high-quality influent water to remove the high salt in the membrane module until the conductivity of the concentrate reaches Influent conductivity value. Flushing is carried out at low pressure (about 3Kg/cm2), and high inflow water flow is beneficial for cleaning.

The water used for flushing must not contain chemicals used for pretreatment, and must not contain scale inhibitors. Therefore, when flushing, the addition of anti-scale agents and sulfuric acid should be stopped.

After flushing, completely close the water injection valve. If the drain at the end of the concentrate line is lower than the pressure vessel, the air outlet in the concentrate line must be located higher than the highest point of the pressure vessel, otherwise the pressure vessel must be evacuated by siphon.

When the system has been shut down for more than 48 hours, care must be taken:

1The element cannot be dried out, the dry element will lose flux and cannot be recovered;

2The system can effectively prevent microbial derivation or flush it regularly every 24 hours. If the membrane tube cannot be flushed with water every 24 hours, the system that has been stopped for more than 48 hours must be stored with a chemical preservation solution;

3The system should be protected from extreme temperature changes.
Fourth, matters needing attention

1. When the high-pressure pump is used for the first time, the exhaust valve must be opened to discharge the residual air of the high-pressure pump.

2. The high-pressure pump is strictly prohibited from idling without water.

3. The purpose of the high pressure pump is to increase the pressure of the reverse osmosis membrane inlet water, and the pressure after the normal pump is 10-12 kg.

4. The RO concentrated water pressure regulating valve is to adjust the pressure at the outlet of the high-pressure pump. It is strictly forbidden to close all the concentrated water regulating valves. The larger the concentrated water pressure regulating valve valve is opened, the smaller the outlet pressure of the high-pressure pump, and the more closed, the higher the outlet pressure of the high-pressure pump. All must be closed.

5. The temperature of the reverse osmosis equipment. It can be inferred according to the temperature of the base, if the temperature measured by the oil hole is more accurate. The temperature of the shaft increases continuously from start to operation. Stabilized after 1-2 hours of operation. If the shaft is not installed correctly, the temperature rises suddenly and high temperature occurs. Mainly because of too much lubricant.

6. The small mechanical manual rotation confirms whether the rotation is smooth. Due to scratches, foreign objects, etc., the rotation is not smooth, mainly due to the poor installation of the base.

7. If the large-scale machinery cannot be manually rotated to confirm, first cut off the power supply, check whether there is vibration, noise, etc., after confirming that there is no abnormality, and it is running.