Water Treatment for Hemodialysis
In the early days of HD (HemoDialysis), potable city water was routinely used to prepare dialysate. The assumption made at that time was that if potable water from a community water treatment system was safe to drink it was also safe to use for HD. As chronic HD treatment became more popular and widespread, evidence began to accumulate linking chemical and microbiological water-borne contaminants to adverse reactions in patients. Specifically, it was found that organic and inorganic chemicals in the water used to prepare dialysate could diffuse through the dialyzer membrane and enter the patient's blood (2). We now realize that the quality of the water used to prepare dialysate is an extremely important aspect of HD. Some of the most serious dialysis patient injuries reported in the medical literature are related to inadequate or improper water treatment.
A water treatment system provides water in which levels of contaminants known to be toxic to dialysis patients are consistently kept below recommended limits (Table 2). In practice, a water treatment system utilizes several devices and processes for adequate water treatment because different substances are removed with various modalities applied in series. The quality of the water supply, the amount of water required and economic considerations all play a role in the choice of these devices and their combination. In general, no schema exists which defines a water product standard for all HD units; the number and order of devices in the system must be arranged to best suit the needs of any given unit.
Table 2. The Association for the Advancement of Medical Instrumentation: HD water quality standards: maximum chemical contaminant levels (3). |
Contaminant | Suggested maximum level (mg/L) | Contaminant | Suggested maximum level (mg/L) |
Calcium | 2 (0.1 mEq/L) | Sulphate | 100 |
Magnesium | 4 (0.3 mEq/L) | Copper, Barium, Zinc | 0.1 |
Sodium | 70 (3 mEq/L) | Aluminum | 0.01 |
Potassium | 8 (0.2 mEq/L) | Arsenic, Lead, Silver | 0.005 |
Fluoride | 0.2 | Cadmium | 0.001 |
Chlorine | 0.5 | Chromium | 0.014 |
Chloramines | 0.1 | Selenium | 0.09 |
Nitrate | 2 | Mercury | 0.0002 |
