A monovalent anion. Fluoride is found naturally at low levels in some well waters, but normally its presence is due to injection into municipal water to provide a residual up to 2.5 ppm for the control of dental caries. Fluoride levels in potable waters above 5 ppm can cause mottled and brittle teeth. The rejection of fluoride by a RO membrane is pH dependent. Rejections with polyamide membranes in the basic pH range can be greater than 99% due to fluoride being in the salt form. Rejections in the acidic pH range can drop below 50% due to fluoride being in the acid form.
Leave a Reply