Cleaning Chemicals

 

Cleaning Chemicals
In many cases, RO elements can be effectively cleaned with a high pH sodium hydroxide solution (NaOH) followed by a low pH citric acid/HCl solution. The common chelating agent, EDTA, can be add to the sodium hydroxide solution if necessary.

Cleaning Procedure:

1.    Flush all vessels with RO permeate until the feed-concentrate process water is completely displaced.

2.    Prepare a high pH NaOH solution per the allowable pH and temperature guidelines.

3.    Introduce cleaning solution at a rate of 75 l/min per 8-inch diameter vessel.

4.    Recirculate the cleaning solution at a rate of 151 l/min per 8-inch diameter vessel for a period of 45 minutes.

5.    Allow solution to soak if it has been determined that an extended soak time is beneficial to the cleaning process. Extended soak times typically range from 1-12 hours.

6.    Flush the high pH cleaning solution from the vessels using RO permeate until the flush water pH exiting the vessel is close to the flush water pH entering the vessel.

7.    Closely monitor the pH of the cleaning solution during the cleaning process and adjust the pH as needed.

8.    Measure the temperature and flow of the cleaning solution during the start, middle and end of the recirculation periods.

9.    Never allow the vessel pressure drop to exceed 4 bar (60 psi) during any point in the cleaning.

10. Proceed with a low pH cleaning using citric acid. HCl or the combination of Citric Acid and HCl can be used for making the low pH cleaning solution.

11. Once the low pH cleaning is complete, flush the spent solution from the vessels using RO permeate until the flush water pH exiting the vessel is close to the flush water pH entering the vessel.

12. Cleaning chemicals may be present in the permeate after cleaning. Upon restart (post-cleaning), RO permeate should be directed to drain for a minimum of 10 minutes. Please note that the permeate conductivity is usually elevated after a cleaning and may take some time to stabilize.