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✅ Reverse Osmosis in Hemodialysis – MCQ Set 5
41. Which type of RO membrane cleaning is typically required when scaling occurs?
A. Acid cleaning
B. Alkaline cleaning
C. Alcohol-based rinsing
D. UV disinfection
➡️ Answer: A. Acid cleaning
(Used to remove calcium and magnesium deposits.)
42. If an RO system’s rejection rate drops significantly, the first check should be:
A. RO membrane pH
B. Source water temperature
C. Conductivity of product and feed water
D. Dialysate temperature
➡️ Answer: C. Conductivity of product and feed water
(This helps assess membrane efficiency.)
43. A properly functioning RO system typically produces how much product water compared to feed water?
A. 90–95%
B. 75–80%
C. 50–70%
D. 10–20%
➡️ Answer: C. 50–70%
(The rest is waste/reject water.)
44. Which water treatment component protects the RO membrane from mechanical damage due to particles?
A. UV filter
B. Carbon tank
C. Micron prefilter (e.g. 5 or 1 micron)
D. Deionizer
➡️ Answer: C. Micron prefilter
45. According to AAMI, the action level for total viable bacteria in dialysis water is:
A. 50 CFU/mL
B. 100 CFU/mL
C. 200 CFU/mL
D. 500 CFU/mL
➡️ Answer: B. 50 CFU/mL
(Action level = initiate corrective action. Maximum allowable = 100 CFU/mL.)
46. What is the ideal temperature range for RO water entering the membrane?
A. 5–10°C
B. 10–15°C
C. 20–30°C
D. 40–60°C
➡️ Answer: C. 20–30°C
(High temperatures can damage membranes; cold water reduces efficiency.)
47. An RO system alarm indicates low pressure in the feed water line. The technician should first:
A. Replace the membrane
B. Check incoming water supply and booster pump
C. Call biomedical engineer
D. Ignore and restart the system
➡️ Answer: B. Check incoming water supply and booster pump
48. What is the AAMI maximum allowable level of nitrate (as nitrogen) in dialysis water?
A. 0.1 mg/L
B. 1.0 mg/L
C. 2.0 mg/L
D. 10.0 mg/L
➡️ Answer: C. 2.0 mg/L
49. What is the recommended location for collecting water samples for endotoxin testing in a dialysis unit?
A. Directly from the city water source
B. After carbon filter
C. After RO system, before entering dialysis machine
D. From drain line of RO unit
➡️ Answer: C. After RO system, before entering dialysis machine
(Sampling should represent the water patients are exposed to.)
50. According to best practice, how often should carbon tanks be tested for total chlorine/chloramine breakthrough?
A. Before each dialysis shift
B. Once per week
C. Only when patients report symptoms
D. After every water softener regeneration
➡️ Answer: A. Before each dialysis shift
51. What is the recommended pore size of an ultrafilter used after the RO system in dialysis?
A. 10 µm
B. 5 µm
C. 0.2 µm
D. 1.0 µm
➡️ Answer: C. 0.2 µm
(Used to remove bacteria and endotoxins post-RO.)
52. In a double-pass RO system, the second RO membrane receives water from:
A. City water directly
B. Final dialysate line
C. Product of the first RO pass
D. Reject line of first RO pass
➡️ Answer: C. Product of the first RO pass
(Double-pass improves purity by passing product water again.)
53. What is the most sensitive method for detecting endotoxins in dialysis water?
A. Total chlorine strip
B. Turbidity test
C. Limulus Amebocyte Lysate (LAL) assay
D. Dipstick urinalysis
➡️ Answer: C. Limulus Amebocyte Lysate (LAL) assay
54. Which condition can lead to increased bacterial contamination in RO systems?
A. Low water temperature
B. Daily disinfection
C. Continuous recirculation
D. Stagnant water in dead legs
➡️ Answer: D. Stagnant water in dead legs
(Dead legs allow biofilm growth.)
55. Which of the following would be a cause of high product water conductivity in the RO system?
A. Fresh carbon filter
B. Proper membrane rejection
C. Compromised RO membrane
D. Cold incoming water
➡️ Answer: C. Compromised RO membrane
56. Which one is a benefit of continuous loop distribution of RO water in dialysis units?
A. Reduces energy use
B. Eliminates bacteria completely
C. Minimizes stagnation and bacterial growth
D. Reduces flow rate
➡️ Answer: C. Minimizes stagnation and bacterial growth
57. According to AAMI, the minimum RO rejection percentage for proper performance is:
A. 70%
B. 75%
C. 80%
D. 90%
➡️ Answer: D. 90%
58. Which disinfection method is commonly used for heat-tolerant RO systems?
A. Citric acid flush
B. Chlorine flush
C. Heat disinfection (pasteurization)
D. UV light
➡️ Answer: C. Heat disinfection (pasteurization)
59. Which of the following is not removed effectively by RO and requires pretreatment?
A. Sodium
B. Lead
C. Chloramines
D. Fluoride
➡️ Answer: C. Chloramines
60. In dialysis centers, why is conductivity monitoring of RO product water performed continuously?
A. To ensure the correct dialysate temperature
B. To detect membrane failure in real time
C. To monitor bacterial count
D. To measure chlorine/chloramine
➡️ Answer: B. To detect membrane failure in real time
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