Reverse Osmosis membrane CANNOT be backwashed like most of filtration process (sand, ultrafiltration). There 3cleaning procedures:

- Post-service rinsing
- Routine chemical cleaning : 1 to 4 times a year (average)
- Specific chemical cleaning: check the Troubleshooting table

Post service rinse

Seawater flows tangentially along the membrane, creating an salt concentration gradient along the membranes length, the last element having the most concentrated brine bulk.

When the RO is stopped or in stand-by, natural osmosis will happen between the permeate side and the concentrate side containing high salinity brine. This can damage the feed spacers by creating a vacuum in the permeate line, as water will naturally flow back to the concentrate side, driven by osmotic pressure.

To avoid this natural damaging osmosis to happen, seawater and brine are flushed off the membranes after service by permeate water taken from the permeate tank (before chlorination) and pushed in the membrane by a low pressure pump (i.e., feed pump, distribution pump or specific cleaning pump)

Membrane Chemical cleaning

Seawater flows tangentially along the membrane, creating an horizontal concentration gradient on the membranes length.

Membranes have to cleaned typically when:
- Normalized Permeate flow varies by 10-15%
- Normalized Permeate conductivity varies by 10-15%
- Normalized Pressure drop between feed and concentrate varies by 10-15%

Normalized values take into account temperature and salinity variations in feed water.

In order to ease chronicle cleaning, our systems can be equipped with cleaning In Place (CIP) station, readily connected to the membranes rack:

The CIP station, depending on the plant size includes a chemical tank with mechanical or manual stirrer, a CIP pump and a fine filter to avoid debris to enter the membranes. The chemical tank depends on the  number of membranes to be cleaned at the same time.

Alkaline and Acid Cleaning solutions are recirculated around the membranes for at least 30 minutes.

We determine routine cleaning chemicals and procedures upon desalination plant layout and fouling identification:

RO Troubleshooting table: Analyzing the problem:

Contact us for routine and specific cleaning procedures adapted to your system

Desalination Key issues

Seawater Intake

Desalination Pretreatments

Desalination Post-treatments

Reverse Osmosis Desalination Process

Reverse Osmosis Desalination Membranes

Desalination and Energy Costs

Brine Disposal

Membranes cleaning

Storage and Distribution

Containerization / Tropicalization

Instrumentation and Control (SCADA)