The installation of the reverse osmosis (RO) system mainly involves the installation of the membrane elements and pipe connections. In order to ensure a precise connection between the membrane elements and the membrane housing, the water treatment engineer recommends applying a small amount of Vaseline or a lubricating material to the end of the membrane element with a seal ring when installing the RO membrane element. This makes it easier to insert the entire membrane element and also serves as an effective seal. Traditional connections between membranes require the use of continuous joints, and it is important to note that too much Vaseline should not be applied at the connection point, as this may cause membrane element contamination after system operation.
I. Basic Principles of RO System
Reverse osmosis membrane separation technology is the opposite of osmosis. Its principle is that water is separated from a solution by a permeable membrane, and water flows from the water side to the solution side due to the osmotic pressure. If a pressure greater than the osmotic pressure is applied to the solution side, the water in the solution will flow in the opposite direction. Reverse osmosis is used to obtain desalted water, where the feed water is subjected to sufficient pressure to become pure water through the permeable membrane, while the dissolved and suspended matter in water that did not pass through the membrane becomes more concentrated.
For a specific pure water system, its long-term stability is essential. The success of the RO system's long-term performance depends on normal operation and maintenance, including the test, startup, shutdown, cleaning and maintenance of the entire system. Membrane surface fouling and scaling prevention is not only important in the pretreatment design, but also requires appropriate operation. At the same time, the preservation of records and the daily report of RO operating parameters are very important, which can not only reflect the real situation of the operation of the system, but also the reference when taking corrective measures.
II. Water inlet and environmental requirements of reverse osmosis equipment
Power supply: 380V 50Hz
Water supply: 3.0m3/h
Water inlet requirements:
Water inlet temperature: 5-45℃
Influent PH: 3.0-10.0
Water inlet SDI (15 minutes) <5
Influent turbidity <2NTU
Free residual chlorine concentration <0.1ppm
The equipment should be placed indoors to avoid accelerating the aging of the mechanical components of the equipment.
A drainage ditch should be provided where the equipment is located. Displacement maximum 1.5T/H.
Where the equipment is located, lighting facilities should be provided for easy operation.
The equipment shall be located in a place with sufficient operating space for operation and maintenance.
Avoid contact with corrosive fumes.
III. Equipment operation
(1) Boot
1. Check electrical appliances and pipelines to ensure there is water in the original water tank;
2. Open the water supply switch before the incoming water solenoid valve;
3, open [flush solenoid valve/automatic], [raw water pump/automatic], [high pressure pump/automatic], [Main power /ON].
4. The system starts to run automatically.
(2) Shut down
Open [Flush solenoid valve/manual] and flush for 2 minutes.
Call to 【 Main power/OFF 】
To [Flush solenoid Valve/automatic]
(3) Manual flushing of reverse osmosis membrane
Flush: Make sure that there is water in the original water tank and water is filled, open [flush solenoid valve/manual]
Turn to 【 Raw water pump/manual 】【 High pressure pump/manual 】
Rinse appropriate time and then turn to 【 raw water pump/stop 】【 High pressure pump/stop 】【 Flush solenoid valve/stop 】
(4) Reverse osmosis valve adjustment
The flow rate and pressure of reverse osmosis system operation have certain requirements, and the equipment should be adjusted to the appropriate state according to the requirements to ensure the stable operation of the reverse osmosis system, which only needs to be adjusted once, and the manual valve opening can be kept unchanged later.
1. Check the electrical appliances and pipelines to ensure there is water in the original water tank;
2. Open the water supply switch before the incoming water solenoid valve;
3. Fully open RO high pressure pump back ball valve, concentrated water discharge valve, close the return valve;
4. Open [raw water pump/manual], [high pressure pump/manual], [main power supply /ON];
5. The RO system starts to run;
6. Adjustment of the pressure switch before the high-pressure pump: The pressure switch before the high-pressure pump is mainly used to prevent the high-pressure pump from running when the water pressure is insufficient, thereby avoiding damage to the equipment. Adjust the high-pressure pump front pressure switch to 0.5 kg/cm2, and close the high-pressure pump rear valve slightly to prevent the high-pressure pump from starting frequently.
7. Adjustment of the concentrated water discharge valve (reduce the flow): The RO membrane inlet pressure is about 0.8-1 MPa, and the concentrated water flow is about 0.6 m3/h, and the pure water flow is about 1.5 m3/h. Adjust the backwash valve to make the concentrated water flow about 0.6-1.0 m3/h, and the RO membrane inlet pressure is about 0.8-1 MPa (when all the drainage can be used, it is recommended to close the backwash valve to benefit from extending the life of the membrane).
Automatic control process of the RO main system:
Flow chart: When all the switches are set to automatic mode, the equipment will perform the following procedures as follows:
When starting up, the raw water solenoid valve and the flushing solenoid valve are fully open, and the high-pressure pump is delayed for 5 seconds before starting, and flushed for 30 seconds. Then, the flushing solenoid valve is closed, and the system enters the normal water supply state.
When the system is equipped with a pure water high-level control (floating ball switch), the system will automatically open the flushing solenoid valve and close the high-pressure pump when the water is full. The low-pressure flushing is carried out for 20 seconds before closing the raw water pump and the inlet solenoid valve. When the original water tank has water and the pure water tank is at a low level, the original water pump and the high-pressure pump will be automatically started and the inlet solenoid valve will be opened to produce water.
When the pretreatment system is automatically flushed or regenerated, the high-pressure pump stop, water inlet solenoid valve closed.
IIII. Pre-processing operation panel description
A1 - Inlet valve A2 - Outlet valve A3 - Backwash inlet valve A4 - Backwash drain valve A5 - forward wash drain valve
(1) Sand filter
1. Specification: φ400×SS1650,
2. Quantity: 1 set
3. Material: FRP
4. Filter material type: refined quartz sand
Function: effectively remove the suspended matter and impurities in the water and reduce the influent turbidity.
(1) Operation
During normal startup, firstly open the inlet valve A1 and the forward washing drainage valve A5, and control the inlet flow rate at 1.0T/H. After running for 3-5 minutes, gradually open the outlet valve A2 and close the forward washing drainage valve A5, and then the sand filter will work normally.
(2) Backwash
With the increase of the operation time of the pure water machine, the intercepted dirt gradually increases, and the water flow resistance becomes larger, at this time, backwashing should be carried out to restore the filtration capacity of the sand filter. First open the backwash drain valve A4 and backwash inlet valve A3, the backwash flow rate is controlled at about 1-2T/H, backwash for 5 minutes (depending on the pollution blockage), and the debris and bubbles in the filter material are flushed out until the water is clear.
(3) Washing
After backwashing, the forward wash should be carried out, open the inlet valve A1 and forward wash drain valve A5, control the flow rate at 1T/H, and wash until the water is clear and qualified (about 3 to 4 minutes). Turn on the water outlet valve A2. Turn off the forward wash drain valve A5 and turn it into the normal working state.
(2) Carbon filter
1. Specification: φ400×SS1650
2. Quantity: 1 set
3. Material: FRP
4. Filter material type: water purification grade coconut shell activated carbon
Function: effectively remove organic matter and residual chlorine content in water.
Operation method: The pipe valve arrangement of the carbon filter is shown in the figure above. Operation method is the same as sand filter.
IIIII. Pre-treatment flushing cycle setting
Sand column: once a day
Carbon column: once every 3 days
Filter cartridge replacement: depending on the pollution, generally 1-2 weeks.
Daily replacement of 5μm PP filter cartridge and carbon core:
In order to ensure the normal operation of the reverse osmosis system and extend the service life of the RO membrane, the PP filter element with a pore size of 5μm is used in the system, which has the characteristics of high filtration accuracy and long service life. The replacement cycle is generally one week according to the water quality, and the replacement condition is that the filter element is seriously polluted in a large area, turning black and yellow.
The service life of the filter cartridge is directly related to the operating condition of the pretreatment equipment. If the pretreatment equipment runs well, it can remove most solid particles and suspended sediments, organic matter, etc., thereby reducing the load on the microfilter and extending the service life of the filter cartridge.
The filter cartridge should be replaced regularly to ensure its retention function. Otherwise, it may cause irreparable damage to the RO membrane.
Replacement method:
1. Use a wrench to loosen the filter housing.
2. Remove the old filter cartridge.
3. Insert the new filter cartridge, paying attention to placing the "O"-type seal ring properly. The filter cartridge should be placed in the center of the filter housing so that the water line seals it properly.
4. Tighten the filter housing with a wrench.
IIIIII. Maintenance of reverse osmosis equipment
1. After each batch of water production, the reverse osmosis components should be flushed for protective washing for 20 minutes.
2. As the operating time increases, impurities will accumulate on the membrane surface, affecting the water permeability, and periodic cleaning of the RO elements is required. Cleaning should be carried out according to different pollution conditions.
3. The high-pressure pump should be regularly inspected and repaired, and the lubricating oil should be replaced in accordance with the requirements of the equipment manual.
4. Regular inspection and testing of the conductivity meter and pressure gauges should be carried out to ensure normal and accurate operation.
5. The RO system can be shut down temporarily (less than 3 days) by using low-pressure washing with water from the security filter for 0.5 hours per day to ensure that the components are full of water.
6. If the RO system is shut down for a long time (more than 3 days), 1% formaldehyde solution should be used to fill the RO components, and then all valves should be closed. The solution should be checked once a month, and in summer the environment temperature should be controlled to prevent mould, in winter the environment temperature should be controlled to prevent freezing. If necessary, 10-20% glycerin can be added.
The new reverse osmosis membrane elements are usually soaked with 1%NaHSO3 and 18% glycerol solution and stored in sealed plastic bags. In the case that the plastic bag is not broken, it is stored for about 1 year, and it will not affect its life and performance. When the plastic bag is opened, it should be used as soon as possible to avoid adverse effects on the components due to the oxidation of NaHSO3 in the air. Therefore, the membrane should be opened as far as possible before use.
After the reverse osmosis equipment was tested, we used two methods to protect the membrane. The equipment is run for two days (15 ~ 24h), and then maintained with 2% formaldehyde solution; Or after operation for 2 ~ 6h, use 1% NaHSO3 aqueous solution for maintenance (should exhaust the air in the equipment pipeline, ensure that the equipment does not leak, close all the inlet and outlet valves).
