CCHT - Certified Clinical Hemodialysis Technician Water Treatment and Quality 1 — Questions and Answers
Question 1: What is the primary role of carbon tanks in the dialysis water treatment system?
- Remove calcium and magnesium ions through ion exchange
- Adsorb chlorine and chloramines before water reaches the RO membrane (Correct answer)
- Filter out particulate matter larger than 5 microns
- Eliminate bacteria and endotoxins through UV irradiation
Correct answer: Adsorb chlorine and chloramines before water reaches the RO membrane
Carbon tanks use activated carbon to adsorb chlorine and chloramines from the feed water. These chemicals must be removed before the water contacts the reverse osmosis membrane, as they can degrade the membrane and, if they reach the patient, cause hemolytic anemia.
Question 2: According to AAMI standards, what is the maximum allowable endotoxin level in water used for standard hemodialysis?
- 0.03 EU/mL
- 0.25 EU/mL
- 2 EU/mL (Correct answer)
- 10 EU/mL
Correct answer: 2 EU/mL
AAMI standards set the maximum endotoxin level at 2 EU/mL for standard dialysis water, with an action level of 1 EU/mL. Exceeding these limits puts patients at risk for pyrogenic (fever-producing) reactions during treatment.
Question 3: What is the primary mechanism by which a reverse osmosis (RO) system purifies dialysis water?
- Ion exchange resin that traps dissolved minerals
- Forcing water through a semi-permeable membrane under pressure, rejecting 90–99% of dissolved solutes (Correct answer)
- Ultraviolet light that breaks down organic contaminants
- Activated carbon adsorption of heavy metals and ions
Correct answer: Forcing water through a semi-permeable membrane under pressure, rejecting 90–99% of dissolved solutes
The RO system uses hydraulic pressure to push water through a semi-permeable membrane. The membrane's pore size is small enough to reject most dissolved ions, organics, bacteria, and endotoxins, producing highly purified product water while concentrating contaminants in a reject stream.
Question 4: Which reagent is used in the standard colorimetric test to check for free chlorine residual in dialysis water?
- Phenolphthalein
- Sodium thiosulfate
- DPD (N,N-diethyl-p-phenylenediamine) (Correct answer)
- Orthotoluidine
Correct answer: DPD (N,N-diethyl-p-phenylenediamine)
DPD reacts with free chlorine to produce a pink-to-red color, allowing a rapid and accurate colorimetric measurement. It is the AAMI-recommended method for verifying that carbon tank effluent meets the safe chlorine limit (≤0.1 mg/L) before dialysis begins.
Question 5: At minimum, how frequently should dialysis water be tested for bacteriological contamination according to AAMI guidelines?
- Daily
- Weekly
- Monthly (Correct answer)
- Quarterly
Correct answer: Monthly
AAMI guidelines require bacteriological testing of dialysis water at least once per month. Monthly monitoring ensures that any microbial growth in the distribution loop or storage tank is detected before bacterial counts rise to levels that could cause patient infections or pyrogenic reactions.
Question 6: What is the function of a deionizer (DI unit) in a dialysis water treatment system?
- Remove residual chlorine through catalytic reduction
- Exchange cations and anions in water for hydrogen and hydroxyl ions, producing highly purified water (Correct answer)
- Kill microorganisms by exposing water to high-intensity ultraviolet light
- Reduce water pressure to a safe level before it enters the RO membrane
Correct answer: Exchange cations and anions in water for hydrogen and hydroxyl ions, producing highly purified water
A deionizer contains mixed-bed ion exchange resin that replaces dissolved cations (e.g., sodium, calcium) with H⁺ ions and dissolved anions (e.g., chloride, sulfate) with OH⁻ ions. The H⁺ and OH⁻ combine to form water, removing nearly all ionic contamination. Resistivity or conductivity monitoring indicates when the resin is exhausted.
CCHT - Certified Clinical Hemodialysis Technician Water Treatment and Quality 1
What is the primary role of carbon tanks in the dialysis water treatment system?