TM 10-4610-241-10
TO 40W4-13-41
2-11. CITRIC ACID FEED
After 20 hours of continuous operation or when pH of brine water rises above 8, feed citric acid solution into filtered water
to remove minor amounts of scale which accumulate during normal operation. Product water will be produced during citric
acid feed.
WARNING
Chemicals used for operating ROWPU can kill you. The chemicals alone or in mixture
can be dangerous. ALWAYS wear protective apron, goggles and gloves and make sure
area is well ventilated.
a .
b.
c.
d.
e.
Using citric acid measure, put 0.75 (3/4) pound of citric acid in pail previously marked CITRIC ACID.
Fill CITRIC ACID pail will 3 gallons of brine water.
Stir chemical and brine water with wood paddle from storage box.
Remove lid from chemical feed can (figure 241) marked CITRIC ACID.
Carefully pour solution into chemical feed can. Use care to avoid making bubbles in the solution as you
pour.
f.
Install lid on chemical feed can. Make sure vent cap is open.
g.
h.
i.
i
Set CITRIC ACID chemical feed pump control knob (figure 2-56) to 10.
While the ROWPU is operating normally, set the CITRIC ACID RUN/PRIME valve to RUN (figure 2-60).
Allow unit to operate for 10 minutes.
Draw a 250-ml water sample from brine hose at backwash tank and check for a pH reading of 5 to 8 (para.
2-15).
k.
If pH reading is over 8, repeat steps a through as required using 1.5 (1-1/2) pounds citric acid mixed with 3
gallons of brine water.
1.
Set CITRIC ACID RUN/PRIME valve to PRIME. CITRIC ACID feed is complete when pH is between 5
and 8.
2-12. R.O. ELEMENT CLEANING METHODS.
It will be necessary to clean the R.O. elements to improve total dissolved solids (TDS) rejection, and reduce operating
pressure (P.S.I.). Two methods of cleaning elements are available. One method, used to remove
mineral deposits such as iron and calcium carbonate, is to feed citric acid solution through the vessels (para. 2-13a). The
second methods is to circulate surfactant (soapy) cleaning solution through the vessels (para. 2-
13b). Surfactant is more effective for removing dirt and silt. The R.O. elements must be cleaned:
a .
b .
When R.O. VESSELS gage (10, figure 2-5) indicates over 100 psid (delta).
When product water TDS is high (over 1000) (refer to troubleshooting first).
2-108
