Ultraviolet irradiation to preserve high reverse osmosis water quality

Abstract

The use of ultrapure dialysate decreases hemodialysis patients' morbidity. Bacterial and endotoxin content of reverse osmosis (RO) water is usually lowered or eliminated by a combination of bacterial filtration and regular disinfection of the distribution. Whether bacterial filtration may be replaced by UV irradiation is unknown. One, and subsequently two UV lamps were inserted in a complex RO water distribution circuit, devoid of bacterial filters. RO water bacterial content was checked weekly between RO water distribution disinfections. With one UV lamp on the departure of the RO water circuit, bacterial results remained negative (< 1 cfu/ml) till the second week after disinfection. Disinfection of the circuit was required every four weeks to comply with the AAMI Guidelines (< 200 cfu/ml). Failure of the lamp was followed by bacterial growth (up to 500 cfu/ml), promptly aborted after replacement of the failed lamp. Subsequent addition of a second UV lamp on the return line of the water circuit kept bacteria < 1 cfu/ml for up to five weeks. Endotoxin levels remained < 0.125 EU. UV irradiation preserves a low RO water bacterial/endotoxin content in the distribution line and is not associated with a measurable endotoxin increase.