Sanitization of Reverse Osmosis system and Removal of Biofilm by Chemical methods

Reverse osmosis system

Reverse osmosis process retains salts, organic compounds and also organisms and bacteria.

The membrane for reverse osmosis should hold a reduction of 3 log or 99.9% of bacteria.

If level of bacteria is more than feed water than product water then it may cause for the bacterial growth at the surface.

Precautions:

• RO systems should be of good design without ball valves, threaded connections and dead legs or cracks.
• The pores in PVC pipe should be perfect.
• Water should not be stagnant.
• Nutrients in the system should be minimum
• Chemical control should be provided either on continuous or intermittent basis.

Chemical sanitization of Reverse osmosis system

• Initially any inorganic or organic foulants should be removed by treating with acid cleaner and then with sodium hydroxide respectively
• Sanitizers like formaldehyde, hydrogen peroxide or hydrogen peroxide with Peracetic acid should be circulated for 15-30 minutes and maintained in the same state for 20-30 minutes
• The process should be started periodically for every 5 – 10 minutes and then washed with purified water
• It should be done regularly

Removal of biofilm

Many purified water systems have biofilms within their distribution systems. Precaution should be taken in identifying and removing it. Proper maintenance should be done to control it.

Total viable bacteria enumeration method can be used in identifying biofilm in relation to bacteria levels.

Techniques like distribution loop sanitization with hot water and steam and two phase flow by condensation of pure steam doesn’t remove the biofilm effectively.

Chemical sanitizers help in eliminating the biofilm effectively. Chemical sanitization can be used along with cartridge membrane filtration to remove bacteria. The important criteria to be considered are the method and the agent that is used along with exposure time.

Among the chemical sanitization the most effective method is by using Peracetic acid and Hydrogen Peroxide at a concentration of 0.08% and 1% respectively.

General Method

1. Any organic or inorganic compounds can be removed by using high and low p^H cleaners respectively.
2. Any sanitizer like formaldehyde, chlorine or hydrogen peroxide with Peracetic acid can be used.
3. A 1% solution of hydrogen peroxide together with Peracetic acid is introduced into storage and distribution system.
4. When the concentration of 1% sanitizer is verified then time of the day is recorded and recirculated for 15 minutes.
5. After 15minutes the distribution pumps are put off.
6. The sanitizer is left for 24 hours which removes the biofilm by diffusion driven by difference in concentration.  
7. Rinse with purified water by repeating the procedure for 5-10 times

Biofilms can be further removed by using p^H cleaners or other sanitizers like formaldehyde and chlorine and then rinsing with purified water.

Chemical sanitizers, sanitization, biofilm, reverse osmosis system, hydrogen peroxide

• maintenance of water system. http://drug.fda.moph.go.th/zone_gmp/files/gmp2555/maintenance_of_water_system.pdf. accessed may 20 2016.