9. Disinfection
9.9 BACTERIA CONTAMINATION
9.9.1 Contributors
Table 9-10 is a list of elements influencing the total bacteria count
of the water in a hemodialysis system (Favero, 1985, and AAMI,
1990, pp. 81-94). Even water that is chlorinated by water
treatment facilities can contain low levels of microorganisms.
Table 9-10. Contributors to Bacteria Growth
Element Comment
Water Supply Source
1. Filtration
a. particulate filter Prefiltering used to protect the dialysis machine, but
does not remove microorganisms and can increase
bacteria levels.
b. absolute filters Membrane types. Temporarily removes bacteria, but
clogs. Gram-negative bacteria can grow through
filter. Need frequent replacement and disinfection.
c. activated carbon filter Does not remove bacterial endotoxin. Removes
organics and available chlorine. With chlorine
removed from water, it becomes a reservoir for
bacteria growth.
2. Water treatment devices
a. softeners & deionizers Both are reservoirs for bacteria and they do nothing to
remove the bacterial endotoxin.
b. reverse osmosis Removes bacteria and endotoxin, but must be
disinfected frequently; requires high water pressure.
c. ultraviolet light Endotoxin not affected and UV-immune bacteria can
grow.
d. ultrafilter Membrane similar to RO, but operates on normal line
pressure. Less proficient in removing organics or
salts. When positioned as a last step in treatment
process, will remove bacteria and endotoxin.
Distribution System
3. Water & dialysate
distribution lines
a. size and length
Inside diameter and length can provide spaces where
bacteria can grow if larger or longer than necessary.
b. construction quality Bacteria growth will be caused by bad joints, dead
spaces, and unused branches.
c. outlet tap's elevation Prevent loss of disinfectant by locating as high as
possible.
4. Storage tanks Can provide reservoir for water bacteria. Need
regular disinfection.
Dialysis Machine
All fluid and exposed parts of the machine should be
disinfected regularly.
157-1278-916, Rev A 9-35
March 2004
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