Watts PWR4021 - Manual (Page 11)

11
G. PWR4021 Troubleshooting
RO Membrane Troubleshooting Guide
sYmPtoms
salt PassaGe PeRmeate floW PRessuRe DRoP location Possible causes veRification coRRective action
Normal to increased Decreased Normal to increased Predominantly
first stage
Metal oxide Analysis of metal ions in
cleaning solution.
Improved pretreatment to remove met-
als. Cleaning with acid cleaners.
Normal to increased Decreased Normal to increased Predominantly
first stage
Colloidal fouling SDI measurement of feed/
X-ray diffraction analysis of
cleaning sol. residue.
Optimize pretreatment system for
colloid removal. Clean with high pH,
anionic detergent formulation.
Increased Decreased Increased Predominantly
last stage
Scaling (CaSO
4
, CaSO
3
,
BaSO
4
, SiO
2
)
Analysis of metal ions in
cleaning sol. Check LSI of
reject. Calculate maximum
solubility for CaSO
4
, BaSO
4
,
SiO
2
in reject analysis.
Increase acid addition and scale
inhibitor for CaSO
3
and CaSO
4
. Reduce
recovery. Clean with an acid formula-
tion for CaCO
3
, CaSO
4
and BaSO
4
.
Normal to moderate
increase
Decreased Normal to moderate
increase
Can occur in any
stage
Biological fouling Bacteria count in permeate
and reject. Slime in pipes
and vessels.
Shock dosage of sodium bisulfite.
Continuous feed of low conc. bisulfite
at reduced pH. Peracetic acid steriliza-
tion. Clean with alkaline anionic sur-
factant. Chlorine dosage upstream with
dechlorination. Replace cartridge filters.
Decreased or mod-
erately increased
Decreased Normal All stages Organic fouling Destructive testing, e.g. IR
reflection analysis.
Optimization of pretreatment system
(e.g. coagulation process.) Resin/
activated carbon treatment. Clean with
high pH detergent.
Increased Increased Decreased Most severe in
the first stage
Chlorine oxidant attack Chlorine analysis of feed.
Destructive element test.
Check chlorine feed equipment and
dechlorination equipment.
Increased Increased Decreased Most severe in
the first stage
Abrasion of membrane by
crystalline material
Microscopic solids analysis
of feed. Destructive ele-
ment test.
Improved pretreatment. Check all filters
for media leakage.
Increased Normal to increased Decreased At random O-ring leaks, End or side
seal glue leaks.
Probe test. Vacuum test.
Colloidal material passage.
Replace O-rings. Repair or replace
elements.
Increased Normal to low Decreased All stages Conversion too high. Check flows and pressures
against design guidelines
Reduce conversion rate. Calibrate
sensors. Increase analysis and data
collection.