Identification of the bacteriologicalcontamination of a water treatment line used for haemodialysis and its disinfection.

Renal haemodialysis care units in hospitals use enormous amounts of potable water for the functioning of 'artificial kidneys'. In order to avoid complications with patients' blood this water has to be specially treated. However, the treatment line itself can induce problems due to a high concentration of bacteria in the water. A high bacterial load, as well as bacterial toxins, can provoke immunological reactions in the patients. This paper shows that a granular activated carbon (GAC) filter is a source of bacterial contamination of the water due to the presence of a biofilm on the medium's surface. The majority of the bacteria released are Gram-negative. Because sloughing events in the biofilm can lead to dangerously high concentrations of bacteria and endotoxin levels in water, it is important to control this phenomenon. In treatment lines, GAC filters are regularly chlorinated. Our pilot experiment studied the disinfection of the filter with sodium hypochlorite and peracetic acid. Our results show that both disinfectants have a weak and transient effect on the biomass in the filter. It appears that chemical treatment of the filter is not the ideal solution to the bacteriological threat. Moreover, disinfection of the GAC filter transiently increases the contamination of the water. Alternative solutions to the use of chemical disinfection procedures are discussed.