What precautions should be taken when starting the system for the first time

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Release Date:

2023-09-08

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First startup inspection

1. All pipelines, equipment, and connectors should meet the design pressure;

2. A clean filter element has been installed inside the security filter;

3. The pre-treatment equipment has been backwashed and cleaned to ensure that the effluent meets the design requirements, with SDI<5, turbidity<1 NTU, residual chlorine<0.1ppm, temperature<45 ℃, and pH=3-10.

4. Adjust the opening of the high-pressure pump outlet valve or bypass regulating valve to control the inlet flow of the membrane system to be less than 50% of the operating inlet flow;

5. The drugs and their concentrations in each dosing box are accurate and reliable, the settings and operating status of each drug dosing device are correct, and the interlocking and alarm devices are correctly set;

6. All instruments have been installed correctly and calibrated;

7. A pressure safety relief valve has been installed, set correctly, and measures have been taken to ensure that the product water pressure does not exceed the inlet or concentrated water pressure by 0.3 bar (5 psi);

8. The setting of high-voltage and low-voltage protection devices is correct;

9. When using oxidants for sterilization during pre-treatment, ensure that these oxidants are completely removed before entering the reverse osmosis or nanofiltration host;

10. Check if the automatic control electrical components used for the membrane system are working properly.

 

First startup steps

To ensure that the system operating parameters meet the design parameters, the water quality and yield of the system meet the design goals, and to prevent damage to the membrane due to exceeding the limit of inflow flow and pressure or water hammer, it is necessary to operate in the correct startup sequence.

Before starting the system, on the premise of ensuring that raw water does not enter the components, check each item according to the pre startup inspection items. Thoroughly rinse the pre-treatment part of the raw water, flush out impurities and other pollutants, and prevent them from entering the high-pressure pump and membrane components. Especially, check whether the SDI15 value of the pre-treatment water is qualified, and whether the inlet water contains no residual chlorine or other oxidants;

2. Check all valves and ensure that all settings are correct. The system's produced water discharge valve, inlet control valve, and concentrated water control valve must be fully opened;

3. Use low-pressure and low-flow qualified pre-treatment water to remove air from the membrane components and pressure vessels, with a flushing pressure of 0.2~0.4MPa (30~60psi) and a flushing flow rate of 0.6~3.0m for each 4-inch pressure vessel ³/ h. Each 8-inch pressure vessel has a flushing flow rate of 2.4-12.0 meters ³/ h. All produced water and concentrated water during the flushing process should be discharged into the sewer;

4. During the flushing operation, check all valves and pipeline connections for leakage points, tighten or repair the leakage points;

5. After flushing the system with a wet membrane for at least 30 minutes, close the membrane inlet control valve. Systems with dry film installed should be continuously flushed at low pressure for at least 6 hours or first flushed for 1-2 hours, soaked overnight, and then flushed for about 1 hour. During low pressure and low flow flushing, it is not allowed to add scale inhibitors to the pre-treatment section;

6. Start the high-pressure pump, slowly adjust the bypass control valve of the high-pressure pump, and gradually increase the inlet flow rate of the reverse osmosis/nanofiltration pressure vessel; At the same time, slowly close the concentrated water control valve and increase the pressure until the system recovery rate and water production reach the design value; The time for the pressure boosting process shall not be less than 30-60 seconds, and the time for the increase in inlet flow shall not be less than 20-30 seconds; Check if the system operating pressure and membrane component pressure drop exceed the limit value;

7. Check whether the dosage of various drugs in the system is consistent with the design value;

8. Measure the conductivity of reverse osmosis or nanofiltration influent, each pressure vessel, and total produced water, compare the produced water conductivity of each parallel pressure vessel, and determine whether there are leaks or other faults in membrane components, connectors, and pressure vessel sealing rings. Measure the pH value, conductivity, calcium hardness, alkalinity, etc. of the concentrated water, calculate the LSI and S&DSI index of the concentrated water, and determine whether there is CaCO3 fouling formation in the reverse osmosis or nanofiltration system under these operating conditions;

9. Allow the system to run continuously for 1 hour. Once the production water is qualified, first open the qualified production water delivery valve and then close the production water discharge valve to supply water to subsequent equipment.

10. Record all operating parameters of the first group;

11. After continuous operation for 24-48 hours, check all recorded system performance data, including inlet pressure, pressure difference, temperature, flow rate, recovery rate, and conductivity. Simultaneously sample and analyze the ion composition of influent water, concentrated water, and total system produced water. The system operating parameters at this time serve as the benchmark for system performance;

12. Compare design parameters with actual system performance parameters; It takes some time for newly put reverse osmosis or nanofiltration membrane components to transition from initial performance to stable state, with wet membrane components achieving stable performance after 10 hours of continuous operation, while dry membrane components may only achieve stable performance after 3 days of continuous operation.

 

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