SOP For passivation of purified water storage tank and distribution piping is described in this post which you can follow in the section of the General Industry SOP.

OBJECTIVE
To lay down the procedure for the passivation of purified water storage tank and distribution piping.
SCOPE
This SOP shall be applicable for the purified water storage tank and distribution piping.
RESPONSIBILITY
Engineer
ACCOUNTABILITY
Head of Department
PROCEDURE
  • Collect the Reverse Osmosis (RO) product water in the purified water storage tank.
  • Flush the storage tank with RO water by filling and draining the tank twice.
  • Again take the fresh RO water in the storage tank and flush the interconnecting piping in the open loop and then in the closed loop.
  • Drain out the storage Tank.
  • Prepare the Nitric acid solution (about 10 % solution) in the purified water storage tank. 
  • Take about 350 liters of RO product Water; add 35 liters of Nitric acid.
  • Circulate the above Nitric acid solution in the interconnecting piping in the closed loop distribution system for 2hrs.
  • Stop the distribution pump and drain all the Nitric acid solution.
  • Collect the RO water into purified water storage tank and flush the distribution system till the pH is in between 7-8 and then drain the water.
  • Collect the RO water into the purified water storage tank and heat it to 80ºC to 85ºC and circulate through distribution loop system for a minimum of 1hr to sanitize the loop system.
  • Check the pH values of RO water and outlet of the storage tank.
  • If the pH values of RO water and outlet of storage tank differ by more than +/- 0.5, again flush the distribution system till traces of Nitric acid are removed. pH should be within +/- 0.5 of the RO outlet water.
  • Use proper hand gloves duly disinfected with IPA or chlorinated water while preparing the solution.
  • Use safety goggle and mask while preparing the solution.