Detection of endotoxins in reclaimed and conventionally treated drinking water

Abstract

The Windhoek (Namibia) and Cape Flats (South Africa) reclamation plants, which use different disinfection methods, were compared for their ability to remove endotoxins from feed water. Endotoxins were assayed using the Chromogenic Limulus Amoebocyte Lysate Assay (LAL). The Cape Flats reclamation plant, in which ozonation was used for disinfection prior to active carbon column treatment, was found to be more effective in endotoxin removal than the Windhoek plant in which only breakpoint chlorination steps were used. Both plants showed a significant increase in the level of endotoxins after active carbon column treatment. The level of endotoxins in the final water was found to be related to the level in the effluent after active carbon column treatment. Breakpoint chlorination was shown to contribute to the removal but not to the elimination of the endotoxins. The level of endotoxins in the final reclaimed water was compared to the level in surface and groundwater. The Cape Flats final water had lower levels than conventionally treated drinking water, and slightly higher levels than groundwater.