SOP on Out of Acceptance Limit in Purified Water System

OBJECTIVE: To establish a procedure for action to be taken where critical parameters exceed acceptable limits within the purified water system.

SCOPE: This Standard Operating Procedure applies to the generation and distribution of purified water systems.

SOP on Out of Acceptance Limit in Purified Water System

RESPONSIBILITY: Officer, Executive – Engineering Department.
Head – Engineering Department for overall compliance to this SOP.

Head of Engineering


Soft Water Hardness: If soft water hardness exceeds 5.0 PPM:

  • Stop the Reverse Osmosis system and close the Reverse Osmosis inlet valve.
  • Next, Drain the water from the soft water storage tank.
  • Verify the functioning of the softener unit for regeneration.
  • Manually regenerate the softener unit and recheck hardness.
  • If hardness is within limits, collect water in the soft water tank and restart the RO system.

pH Adjustment:

  • If pH before RO is below 7.5:
  • Increase Sodium Hydroxide (NaOH) solution dosing.
  • If pH before RO is above 8.0:
  • Decrease Sodium Hydroxide (NaOH) solution dosing.

Pressure Drop across MCF-1 micron:

  • If the pressure drops across MCF exceeds 0.8 kg/cm²:
  • Replace the MCF.

Related SOP: SOP on a collection of Swab and Rinse Water samples

ORP Value: If ORP value exceeds 350 mV:

  • Check free chlorine at the softener outlet.
  • If >2 ppm, reduce chlorine dosing to 2 ppm and follow steps 4-7.
  • If 2 ppm, adjust SMBS dosing for chlorine removal.
  • Stop the soft water pump.
  • Drain water from a soft water tank.
  • Collect fresh soft water in the tank.
  • Start soft water pump & SMBS dosing.

RO Conductivity:

  • If RO conductivity exceeds 30 µS/cm:
  • Check RO feed water hardness.
  • Check RO feed water pressure (5.0-9.0 kg/cm²).
  • Inspect RO membrane port ‘0’ rings.

Related SOP: SOP for Operation & Calibration of Water bath

RO Feed Pressure (5.0-9.0 kg/cm²):

  • If RO feed pressure is beyond limits:
  • Check for rupture; replace RO membranes if found.
  • Check for fouling; perform chemical cleaning if fouling is detected.

EDI Conductivity:

  • If EDI conductivity exceeds 1.0 µS/cm:
  • Check EDI feed water conductivity.

Distribution Conductivity:

  • If distribution conductivity exceeds 1.0 µS/cm:
  • Drain storage tank and user points.
  • Collect fresh water in the storage tank.
  • Recheck storage tank water conductivity.
  • If still high, perform hot water sanitization.

UV Tube Intensity (2.4 MW/cm²):

  • If UV tube intensity is less than 2.4 MW/cm²:
  • Replace UV tubes.

SOP: Standard Operating Procedure
RO: Reverse Osmosis

Related SOP: SOP on Microbiological Monitoring of Compressed Air


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