Product information

This product supersedes product no: L770007


  • Liquid product
  • Suitable for RO membrane preservation and dechlorination


  • Helps to maintain RO performance
  • Concentrated product
  • Easy to handle



  • Approved by The Norwegian Food Safety Authority

Safety Data Sheet (SDS)


Directions for use


A. De-Chlorination

If the feed water to the RO system contains free chlorine it must be removed otherwise it can breakdown the RO membrane. NALFLEET™ RO Bisulphite is a 40% solution of Sodium Bisulphite (NaHSO3) It undergoes the reaction below with free chlorine:

2NaHSO3 + 2HOCl → H2SO4 + 2HCl + Na2SO4

A dose rate of 3.66ml/m3 of NALFLEET™ RO Bisulphite should be applied for each 1ppm of free chlorine in the feed water. Use a suitable free chlorine test kit to monitor reduction in free chlorine levels. For continuous applications a suitable storage tank and chemical dosing pump should be used.

The solution should be dosed as close to the RO system as possible (to keep as much of the pre-treatment as possible in contact with chlorine e.g. after the cartridge filters). However, if the free chlorine level is high, the solution should be dosed prior to the antiscalant injection point (or antiscalant dosage adjusted to compensate for chlorine attack, as some antiscalants are attacked by free chlorine). The antiscalant and NALFLEET™ RO Bisulphite dosing point should be far enough apart to prevent neat product mixing.

B. Lay up and preservation of Reverse Osmosis and Nano-Filtration membranes and systems. (Polyamide, TFC, CPA membranes)

It is necessary to preserve membranes when the RO or NF system is taken out of production for more than 24 hours. Failure to do so may allow biofilms to form on the surface of the membranes which will cause operational problems upon restarting the system.Prior to shutdown, the RO needs to be cleaned in-line with operational guidelines and MUST be flushed with RO permeate. After flushing with permeate, the preservation solution can be pumped into the RO system. Note: It has to be verified that the plastic materials (including pressure vessels) used in the membrane plant are resistant to sodium bisulphite. Otherwise cracks might occur in the plastic materials.

  1. Prepare a solution of 2.5 % NALFLEET™ RO Bisulphite
  2. Fill the entire system to be preserved with the solution
  3. It is recommended to measure the pH regularly. A fresh solution is needed when the pH < 3 A fresh solution is also needed when the liquid becomes turbid or changes colour. Regular inspections (weekly) are recommended.

NALFLEET™ RO Bisulphite conforms to the requirements of NSF/ANSI Standard 60 - Drinking Water Treatment Chemicals - Health Effects.