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✅ Reverse Osmosis in Hemodialysis Water Treatment – MCQ Set 3
21. Which of the following best describes the “rejection rate” in an RO system?
A. The speed of water flow through the system
B. The temperature at which water is rejected
C. The percentage of contaminants removed from feed water
D. The percentage of product water sent to drain
➡️ Answer: C. The percentage of contaminants removed from feed water
22. Which one is NOT commonly monitored in dialysis RO water systems?
A. Conductivity
B. Temperature
C. Chlorine/chloramine
D. Hemoglobin
➡️ Answer: D. Hemoglobin
23. The RO system alarm sounds due to high conductivity. What is the immediate action?
A. Turn off the machine and continue dialysis
B. Continue dialysis and reset alarm
C. Stop dialysis water supply and investigate cause
D. Add salt manually to reduce conductivity
➡️ Answer: C. Stop dialysis water supply and investigate cause
24. AAMI recommends maximum conductivity for dialysis water to be:
A. 0.1 µS/cm
B. 0.5 µS/cm
C. 1.3 µS/cm
D. 3.0 µS/cm
➡️ Answer: C. 1.3 µS/cm
(Higher values may indicate membrane damage or chemical contamination.)
25. Which type of RO membrane is typically used in dialysis systems?
A. Cellulose acetate
B. Polysulfone
C. Thin-film composite (TFC)
D. Polycarbonate
➡️ Answer: C. Thin-film composite (TFC)
26. According to ISO 23500, the action level for endotoxins in RO product water is:
A. 0.25 EU/mL
B. 1.0 EU/mL
C. 2.0 EU/mL
D. 5.0 EU/mL
➡️ Answer: A. 0.25 EU/mL
27. What is the main hazard of chloramine breakthrough into dialysis water?
A. Fever
B. Hypertension
C. Hemolysis
D. Hypokalemia
➡️ Answer: C. Hemolysis
28. The purpose of a water softener in pre-treatment is to remove:
A. Chlorine and chloramine
B. Hard minerals like calcium and magnesium
C. Organic matter
D. Endotoxins
➡️ Answer: B. Hard minerals like calcium and magnesium
(To prevent RO membrane scaling.)
29. Which test is used to measure chlorine/chloramine levels in dialysis water?
A. Conductivity meter
B. DPD (diethyl-p-phenylenediamine) colorimetric test
C. Dipstick pH test
D. Hemoglobin analyzer
➡️ Answer: B. DPD colorimetric test
30. RO system rejection performance is typically measured by comparing:
A. Dialysate to drain water
B. Conductivity of RO water to chlorine content
C. Feed water TDS vs product water TDS
D. Endotoxin count vs temperature
➡️ Answer: C. Feed water TDS vs product water TDS
(TDS = Total Dissolved Solids)
31. What is the main risk if the water softener fails before the RO unit?
A. pH imbalance
B. Increased endotoxins
C. Scaling of the RO membrane
D. Increased conductivity of dialysate
➡️ Answer: C. Scaling of the RO membrane
(Due to calcium/magnesium salts not being removed.)
32. Which of the following organisms can form biofilms in the RO system if not properly disinfected?
A. Staphylococcus aureus
B. Pseudomonas aeruginosa
C. Escherichia coli
D. Clostridium difficile
➡️ Answer: B. Pseudomonas aeruginosa
33. AAMI maximum allowable aluminum concentration in product water is:
A. 0.01 mg/L
B. 0.1 mg/L
C. 0.2 mg/L
D. 0.5 mg/L
➡️ Answer: B. 0.01 mg/L
34. When conducting disinfection of an RO system, which of the following is TRUE?
A. Disinfectants can be used without system flushing
B. Disinfection should be done yearly
C. System must be flushed thoroughly to avoid patient exposure
D. RO membranes do not tolerate chemical disinfectants
➡️ Answer: C. System must be flushed thoroughly to avoid patient exposure
35. The RO system is found to have low permeate flow and increased rejection pressure. This most likely indicates:
A. UV lamp failure
B. Chloramine breakthrough
C. RO membrane fouling
D. High water temperature
➡️ Answer: C. RO membrane fouling
36. Which part of the water treatment system removes particles larger than 5 microns?
A. UV sterilizer
B. Carbon filter
C. Multimedia filter
D. RO membrane
➡️ Answer: C. Multimedia filter
37. Which of the following is NOT recommended as a backup for RO system failure?
A. Bottled sterile water
B. Secondary RO system
C. Ultrafilter bypass
D. Emergency water bypass system
➡️ Answer: C. Ultrafilter bypass
(Ultrafilters are for microbiological control, not a substitute for RO.)
38. What is the primary function of the ultrafilter placed after RO?
A. Remove chlorine
B. Reduce conductivity
C. Remove endotoxins and bacteria
D. Soften water
➡️ Answer: C. Remove endotoxins and bacteria
39. According to AAMI, how frequently should bacterial cultures be taken from dialysis water?
A. Daily
B. Weekly
C. Monthly
D. Annually
➡️ Answer: C. Monthly
(And after system changes, repairs, or contamination events.)
40. The RO reject water is typically:
A. Stored and reused in dialysate
B. Sent to drain
C. Used for disinfection
D. Used as dialysate in emergency
➡️ Answer: B. Sent to drain
