With the arrival of winter, the temperature drops, causing a decrease in water production of RO membrane elements, and an increase in the desalination rate. Why is this?
As the feedwater temperature drops, the temperature of the permeated water molecules decreases. As the a result, viscosity of the water molecules increases, and the diffusion performance weakens, causing a decrease in the water production. As the feedwater temperature drops, the permeability of the solute decreases, and the desalination rate on the water production side increases.
Within the range of 15-35°C, the water production changes by about 3% whenever water temperature changes 1°C. Due to the special properties of water at 4°C (such as maximum density, and minimum volume), the temperature curve for RO membrane manufacturers starts from 5°C.
So how do we maintain our membrane elements properly in winter?
01 Membrane maintenance during system operation
① The RO system should be operated when the ambient temperature is greater than 5℃
② Increase the feedwater temperature or increase the feedwater pressure
③ When the raw water temperature is below 10℃, it is recommended to use a raw water heater to heat it to 20-25℃.
02 Membrane maintenance during system shutdown
① Keep the temperature between 5℃-45℃
② Low temperature is conducive to the preservation of membrane elements, but the system should be prevented from freezing.
03 Maintenance of unused membrane elements
① Dry membrane elements should be preserved in a cool, dry place without direct sunlight, with the ambient temperature below 45℃. However,
② wet membrane elements should be preserved between 5℃ and and 45℃.
③ If the membrane elements are frozen, they should be slowly “defrosted” at room temperature in case of damage, and pressurized operation should only be performed after they are completely ice-free.
04 Maintenance of RO Equipment in winter
① If the RO equipment is intalled indoors, the room temperature shall not be below 0℃. The equipment shall be heated if necessary.
② If the feedwater pipe cannot supply water due to freezing or the water supply is insufficient, it is prohibited to forcibly operate the RO equipment Instead, adhere to the feedwater requirements of the RO membrane elements. It is prohibited to blindly increase the pressure.
③ If the RO equipment is installed outdoors, antifreezing measures must be taken. The water treatment equipment must be stopped if the temperature falls below zero.