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Reverse Osmosis Membrane Polluted Reasons And Solutions

Nov 28, 2017

Reverse osmosis is the most sophisticated liquid separation membrane technology. Reverse osmosis device, we has more than 10 years experience. Summarized the following causes of reverse osmosis membrane pollution, and make up solutions.

Reverse osmosis membrane pollution analysis:

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 (A) The  property of reverse osmosis membrane damage, resulting in membrane pollution.

1. Polyester reinforced non-woven fabric, about 120μm thick;

2. Porous polysulfone material intermediate support layer, about 40μm thick.

3. Polyamide thin separation layer, about 0.2μm thick.

The following reasons:

1. Reverse osmosis membrane maintenance is not standardized.

2. Maintenance meet the requirements, the storage time more than 1 year.

3. Out of running, reverse osmosis membrane maintenance is not standardized.

4. Ambient temperature below 5 ℃.

5. The system is running under high pressure.

6. Shutdown is not appropriate.

(B) Water quality changes frequentcly caused by membrane pollution.

Raw water quality changes, so that pre-treatment load increases, due to influent water containing inorganic, organic matter, microorganisms, particulates and colloids and other impurities increased, so the membrane pollution chance will increase.

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(C) Cleaning is not timely and cleaning methods incorrect.

In use, the membrane in addition to the normal performance degradation, there are not timely cleaning and cleaning methods are not correct.

(D) Do not dosing the right medicine.

In use, due to poor chlorine resistance, the composite polyamide membrane is not properly dosed with disinfectants such as chlorine, and users are not paying enough attention to the prevention of microorganisms and easily lead to microbial contamination.

(E) Membrane surface wear.

Membrane components are blocked by foreign matter or the surface is subject to wear (such as sand, etc.), this situation should be detected using probing components within the system to find damaged components, change preconditioning, replacement of membrane components.

Phenomenon(Common signs)

First, the biological fouling Organic deposits are mainly live or dead microorganisms, hydrocarbon derivatives, natural organic polymers and all carbon-containing substances. Initially manifested as an increase in desalination, pressure drop and water production decreased.

Solution

(A)Perfect  pretreatment.

Improve the pre-treatment reasons:

(1) Prevent contamination on the surface of the membrane and prevent suspended substances, microorganisms, colloidal substances from attaching to the membrane surface, or fouling of components.

(2) Prevent membrane fouling. Due to the concentration of water, some insoluble salts are deposited on the membrane surface.

(3) Ensure that the membrane from mechanical and chemical damage, to ensure that the membrane performance and adequate use of time.

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(B)Cleaning  membrane.

Cleaning principles: understanding of water quality characteristics, chemical analysis of pollutants, choose the best cleaning agents and cleaning methods.

Cleaning conditions:

1. Product water than normal down 5% -10%.

2. After the temperature is corrected, the water supply pressure will increase by 10% -15%.

3. Through the water conductivity (salt content increase) increased by 5% -10%.

4. Multi-stage RO system, through the different sections of the pressure drop increased significantly.

Cleaning method:

System Recoil → Negative Pressure Cleaning → (if necessary) Mechanical Cleaning → Chemical Cleaning → Ultrasonic Cleaning (if possible).

Cleaning steps:

Cleaning single-stage system: configuration of cleaning fluid → low-flow input cleaning fluid → cycle → soak → high-flow pump cycle → flush → restart system

Cleaning for special pollutants include: cleaning sulfate scale, cleaning carbonate scale, cleaning iron and manganese pollution, cleaning organic pollution.

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(C)Membrane for maintenance.

1. System outage in the short term (1-3 days).

The first low-pressure (0.2-0.4MPa), large flow flushing. The time is 14-16 minutes.

2. System outage more than a week (ambient temperature above 5 ℃)

The first low-pressure (0.2-0.4MPa), large flow flushing. The time is 14-16 minutes. Configure 0.5% formalin solution, enter low pressure, and circulate for 10 minutes. Close the valve, sealed.

3. Environment temperature below 5 ℃

The first low-pressure (0.2-0.4MPa), large flow flushing. The time is 14-16 minutes.

Conditions, the bad environment can be increased to 5 ℃ above, and then follow the 1 method.

Unconditionally, one-third of the water produced in the system will flow for a long period of time, ensuring the system runs for 2 hours a day. After cleaning, it will be moved to a place where the ambient temperature is above 5 ° C and soaked in 0.5% formalin solution Flip every two days.

(D)Avoid the film running under high pressure.

1. After the equipment is emptied, the gas is quickly run-up without re-running.

2. Clean or replace the micron filter to ensure that the pipeline does not leak.

3. The operation of the normal operation of the pump, the flow rate and the provisions of the same value to determine the operating pressure.

(E)Pay attention to the shutdown operation.

1. Prepare to shut down, step down to 3bar or so with pre-treated water for 14-16 minutes.

2. Preparation shutdown, should stop dosing chemical reagents.