Reverse Osmosis Membrane Cleaning Steps

Reverse osmosis membranes of various types have a specific working time after which they must be cleaned or replaced. This is determined based on a number of factors, which we will explain below. Whether the reverse osmosis device is cleaned every three months or cleaned every month. It is necessary to improve the operating conditions and improve the pretreatment effect.

Determine the cleaning condition

• If the standard freshwater production decreases by more than 10%.
• If the uniform salt penetration rate increases by more than 10%.
• The pressure difference between the feed water and the concentrated water after temperature calibration increases by more than 10%.
• In order to maintain the normal flow of fresh water,
• There are serious contaminants and scales in the internal device.
• Before the RO system does not work for a long time.
• Routine maintenance of the RO system.

Check the cleaning of the reverse osmosis system

Before checking the cleaning of the reverse osmosis system, the following other reasons that may cause the above phenomenon should also be considered comprehensively:

• Low operating pressure (pressure controller failure and high-pressure pump abnormal).
• Low inlet water temperature (heater failure or seasonal changes cause water temperature to drop).
• The increased salt content of the outlet.
• Abnormal treatment.
• Concentrated water leaks into fresh water due to membrane damage, misalignment of the center tube of the tandem membrane element, and insufficient O-ring sealing of the pressure vessel.

Contaminants

• Reverse osmosis membrane elements mainly include CaCO3, CaSO4, BaSO4, and SrSO4
• Common contaminants in reverse osmosis membrane elements mainly include CaCO3, CaSO4, BaSO4, SrSO4, metal oxides, silicon deposits, organic matter, and biological slime. When the scale inhibitor dosing system or acid addition system fails, CaCO3 may be deposited in the membrane elements, and chemical cleaning methods of periodic cleaning or overnight soaking should be adopted.
• Different contaminants cause different degrees of damage to the membrane, and different cleaning solutions are used for different contaminants.

Read more about how to choose the right reverse osmosis membrane.

Reverse Osmosis Cleaning System (CIP) Equipment

• Reverse Osmosis Cleaning (CIP) system is generally composed of cleaning pump, chemical dosing tank, 5-20um safety filter, heater, relevant pipeline valves and controls.
• The cleaning methods include static soaking and periodic cleaning. Static soaking uses cleaning fluid to absorb the membrane. The time depends on the degree of contamination, which is approximately 1-15 hours.

The general steps of periodic cleaning are:

1. Use a pump to send fresh water from the chemical dosing tank to the pressure vessel, and empty it for a few minutes.
2. Prepare the cleaning solution with fresh water in the chemical tank
3. Circulate the cleaning fluid in the pressure vessel for 1 hour or reach a predetermined time. The cleaning flow can be determined according to the following table. When the contamination is serious, the cleaning flow can be increased to 150% of the resin in the table.
4. At this time, the cleaning pressure drop is relatively large and is generally controlled not to exceed (0.10-0.14MPa) / root membrane element or 0.4MPa / root membrane group. At the beginning of the cleaning of the drug, use 50% of the flow value in the table to inject the hot cleaning fluid into the pressure vessel to control the pressure so that it can overcome the pressure drop between the inlet and outlet water and there is no freshwater flow. In order to prevent the cleaning fluid from being diluted, the concentrated water drain valve can be opened to drain the system water before cleaning. The reverse osmosis system can be cleaned in sections. The cleaning direction is the same as the operating direction. Reverse cleaning is not allowed, otherwise, it may cause the membrane roll to protrude and damage the membrane element.
5. After the cleaning cycle is finished, clean the chemical tank with fresh water.
6. Rinse the above-mentioned pressure vessel with fresh water.
7. After rinsing, run the reverse osmosis system with the freshwater outlet valve open until the freshwater is clean, without foam or cleaning fluid, which usually takes 15-30 minutes.

Reverse Osmosis Membrane Replacement

After the reverse osmosis equipment has been operating normally for a period of time, the reverse osmosis membrane elements will be contaminated with suspended solids or insoluble salts that may be present in the feed water, and the following symptoms will appear:

1. The weight of the membrane element in the reverse osmosis equipment increases.
2. The removal rate of the RO membrane is significantly increased or decreased.
3. Under standard pressure, the water output of the reverse osmosis equipment has decreased significantly.
4. In order to achieve standard water output, the operating pressure must be improved.
5. The pressure drop between the inlet water and the concentrated water of the reverse osmosis equipment increases.
6. Take the membrane element out of the pressure vessel and pour water on the inlet side of the installed membrane element. If the water cannot flow through the membrane element, it will only overflow from the end surface, indicating that the inlet flow channel is blocked.