The different water purification systems used in hemodialysis are reviewed here. Discussions concerning the waterborne contaminants to which hemodialysis patients are exposed and the methods of monitoring water purification systems used in hemodialysis are presented separately. (See "Contaminants in water used for hemodialysis" and "Maintaining water quality for hemodialysis".)
RATIONALE FOR WATER PURIFICATION SYSTEMS
All dialysis facilities require a properly designed and maintained water treatment system to safeguard patients . No municipal water can be considered safe for use in hemodialysis applications in the absence of a treatment system since some of the most toxic contaminants arise from municipal water treatment practices.
Hemodialysis patients are particularly vulnerable to contaminants in the water used to prepare concentrate and dialysis fluid, or in water used for reprocessing dialyzers (see "Reuse of dialyzers", section on 'Reprocessing techniques'). This vulnerability is due to the following:
●Since water is the major constituent of dialysis fluid, compared with individuals who are not on hemodialysis, hemodialysis patients are exposed to extremely large volumes of water. The estimated water intake of a healthy individual is 2 L per day or 14 L per week. By comparison, during a single dialysis treatment lasting four hours, performed at a dialysis fluid flow rate of 800 mL/min, a hemodialysis patient is exposed to 192 L of water, or to 576 L per week, if treated three times weekly.
●Hemodialysis patients have inadequate barriers to such contaminants. In healthy individuals who are not on dialysis, the gastrointestinal tract separates blood from contaminants in the water. By comparison, the barrier between blood and water in hemodialysis patients is the membrane within the hemodialyzer through which transfer of contaminants is limited only by the molecular or particulate size of the contaminant.