Copper is a divalent cation similar to cadmium, lead, and calcium. It is therefore removed very well by membrane process. A typical RO membrane should give 97-99% rejection of copper. Well waters or surface waters may contain very low levels of Copper, generally less than 0.001 mg/L. [....]
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 [....]
Ion Exchange and boiler water chemists frequently report the concentration of hardness as "Grains per Gallon (as calcium carbonate equivalents)". One Grain per U.S. Gallon (as calcium carbonate) is equal to 17.1 ppm (as calcium carbonate). [....]
Color is a non-specific test that measures the relative level of organic compounds in water based on their contribution to adding color and is reported in APHA units relative to the platinum standard. [....]
A monovalent anion. The solubility of chloride salts is high and does not create a RO scaling problem. Chloride, in seawater, is the prevalent anion. Chloride is the anion used to automatically balance a RO feed water analysis. The recommended upper limit for chloride in potable water by the US EPA and WHO is 250 ppm based on taste [....]
A divalent anion. The solubility of calcium carbonate is low and can cause a RO scaling problem in the back-end of a RO. Calcium carbonate solubility is measured using LSI (Langlier Saturation Index) for brackish waters or SDSI (Stiff-Davis Index) for seawaters and is lower with increasing temperature and increasing pH. Carbonate is one component of alkalinity and its [....]