Water for haemodialysis (WFH), which is manufactured on-site in haemodialysis hospitals, is indispensable for haemodialysis therapy. Water treatment systems for manufacturing WFH primarily consist of membrane separation technologies: reverse osmosis (for chemical contaminants) and ultrafiltration (for microbial contaminants). To further improve the quality of WFH, we successfully apply adsorption technology, namely electrodeionization (EDI), after reverse osmosis to remove additional chemical contaminants and microbial contaminants from WFH. When the DC current was supplied to the EDI system, we found that single-stranded bacterial DNA could also be removed by the EDI, as well as viable bacteria and endotoxins.