Purification of dialysis fluid: historical background and perspective

When dialysis became a chronic therapy, certain clinical symptoms could be connected to the fluid quality and some form of water treatment had to be introduced. The required equipment was empirically developed and consisted of sedimentation filters, carbon filters and softeners. In the mid-1970s the toxic effect of aluminum accumulation was discovered and led to the introduction of reverse osmosis modules. When these components - prefilters, softeners and RO modules - are properly maintained, they produce water of a quality that should meet modern standards. However, the water quality could be ruined by bacterial contamination from the distribution pipes, unless the entire flow path is hygienically designed and frequently disinfected. The quality of the concentrate is also important, especially the bicarbonate component which is prone to bacterial growth. The extent of the microbiological burden in water and dialysis fluid has been brought to the attention of the dialysis community through new and sensitive detection and quantification methods for bacteria and endotoxin.