Reverse osmosis systems are highly favored by various industrial water industries due to their advantages such as simplicity, ease of operation, control and maintenance. Among them, it holds a very important position in the seawater desalination and brackish water desalination industries.
Due to the strict requirements of reverse osmosis devices for feed water quality, if the pretreatment is improper, it will cause problems such as scaling and pollution to the reverse osmosis devices. Contamination of reverse osmosis components will deteriorate the quality of the produced water, reduce the water production rate, deteriorate the desalination performance and increase energy consumption. If it is not cleaned in time, it will lead to a shortened membrane lifespan, irreparable wear and tear, and even the need to replace the membrane. Therefore, regular cleaning is the key to ensuring the normal operation of the membrane throughout its lifespan.
Pollutant
Among the contaminants that contaminate reverse osmosis membranes, common ones include various calcium ions, metal oxide precipitates, silicon deposits, inorganic or organic precipitate mixtures, natural organic matter, synthetic organic matter, microorganisms, etc.
Cleaning method
The cleaning methods of reverse osmosis membranes are classified into physical cleaning (such as low-pressure flushing), chemical cleaning, and physical-chemical cleaning, among which chemical cleaning is the most widely used.
Cleaning cycle
The normal cleaning cycle for reverse osmosis membranes is once every 3 to 12 months. If the reverse osmosis pretreatment system is cleaned more than once a month, further inspection, adjustment or redesign of the system is required. If the cleaning frequency is once every three months, the existing equipment needs to be renovated. When the performance of the membrane element drops to 30% to 50% of the normal value, cleaning cannot fully restore the performance of the membrane element. At this point, it is necessary to consider replacing the membrane element.
Chemical cleaning
Sometimes, choosing the appropriate chemical cleaning agents and a reasonable cleaning plan involves many factors. To achieve a good cleaning effect, sometimes a combination of different chemical cleaning agents is used for cleaning.
Acidic cleaning can be used to remove inorganic salt scale deposited on reverse osmosis membranes, while alkaline cleaning can be used to remove organic matter and colloidal contaminants.
A typical procedure is to first use acidic cleaning to remove inorganic contaminants, and then use alkaline cleaning to remove organic contaminants.
Note: There are slight differences among various reverse osmosis membrane manufacturers. When cleaning, you can refer to the product manual of each membrane manufacturer.
