Reverse osmosis membrane separation technology (RO Technology for short) 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 long-term performance of reverse osmosis system depends on normal operation and maintenance, including commissioning, start-up and shutdown, cleaning and maintenance of the whole system, membrane fouling and scale prevention, etc.

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

First boot

(1) Before starting the startup procedure, fully clean the pretreatment part, wash away impurities and other pollutants, and do not inject unqualified water into the membrane element.

(2) When there is water in the raw water tank, open the upper inlet valve and lower discharge valve of the mechanical filter and turn on the power supply of the raw water pump. At this time, the metering pump will automatically add medicine. The water enters the mechanical filter from the upper inlet valve and is discharged from the lower discharge valve. After the water is clear, open the upper inlet valve and lower discharge valve of the activated carbon filter, the outlet valve of the mechanical filter, and turn off the lower discharge valve of the mechanical filter. At this time, the water enters the activated carbon filter, Test the pollution index of the outlet water of the mechanical filter. After the outlet water of the activated carbon filter is cleaned, the RO host opens the concentrated water valve and discharges the pure water

(3) Open the inlet valve of RO system, close the lower discharge valve of activated carbon filter, let the low-pressure and low flow water flush out the air in the element and pressure vessel to make the pressure 0.2-0.4mpa, and open the exhaust valve of security filter to exhaust the air;

(4) During flushing operation, check all pipeline contacts and valves for leakage;

(5) After several minutes of flushing and air removal, start the high-pressure pump and operate at low pressure for several minutes, and then gradually close the return valve and concentrated water discharge valve to make the pressure rise slowly until the proportion of fresh water and concentrated water is close to the design proportion, but not exceed, and the pressure does not exceed the design upper limit;

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

Normal boot

Once the RO system starts to operate, it should continue to operate under a stable condition in theory. In fact, the RO system needs to be closed and started frequently. Each startup and shutdown cycle involves changes in pressure and flow, which causes mechanical stress to membrane elements. Therefore, the number of opening and closing times should be reduced as far as possible. At the same time, the more stable the normal startup procedure is, the better, In principle, the procedure should be the same as that for the first startup. The most important thing is that the inlet pressure should rise slowly.

Normal shutdown

When the RO system is closed, open the high-pressure concentrated water valve gradually before the high-pressure pump is closed. Sudden pressure reduction is strictly prohibited, and then flush with penetrant or high-quality influent to remove the high salt in the membrane module until the conductivity of the concentrated solution reaches the influent conductivity value. Flushing is carried out at low pressure (about 3kg / cm2), and high water inlet flow is beneficial to cleaning.

The water used for flushing shall not contain chemicals used for pretreatment, and there shall be no scale inhibitor. Therefore, during flushing, the addition of anti scale agent and sulfuric acid shall be stopped.

After flushing, completely close the water injection valve. If the end of the concentrated liquid pipeline enters the drainage place and is lower than the pressure vessel, the air outlet in the concentrated liquid pipeline must be higher than the highest point of the pressure vessel, otherwise the pressure vessel must be evacuated by siphon.

When the system is shut down for more than 48 hours, you must pay attention to:

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

2. The system can effectively prevent microbial derivation or wash the membrane tube regularly every 24 hours. If the membrane tube cannot be washed with water every 24 hours, the system stopped for more than 48 hours must be preserved with chemical preservation solution;

3. The system shall be protected from extreme temperature changes.

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 shall not idle without water.

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

4. Ro concentrated water pressure regulating valve is to regulate the pressure at the outlet of high-pressure pump. It is strictly prohibited to close all concentrated water regulating valves. The larger the valve of the concentrated water pressure regulating valve is opened, the smaller the outlet pressure of the high-pressure pump is, and the closer it is closed, the greater the outlet pressure of the high-pressure pump is. It must be strictly prohibited to close all.

5. Temperature of reverse osmosis equipment. It can be inferred from the temperature of the base. If the oil hole is used to measure the temperature, it is more accurate. The shaft temperature rises continuously from start to operation. Stable after 1-2 hours of operation. If the shaft is not installed correctly, the temperature rises suddenly and high temperature occurs. Mainly because there is too much lubricant.

6. Small machinery rotates manually to confirm whether the rotation is smooth. Due to scratches and foreign matters, the rotation is not smooth, mainly due to the poor installation of the base.

7. If large machinery cannot be rotated manually, first cut off the power supply and check whether there is vibration, noise, etc. after confirmation, it is running without abnormality.