Boron can be found in seawater at levels up to 5 ppm and at lower levels in brackish waters where inland seas once existed. Boron is not a foulant. The removal of boron to ppb levels is an important issue in the electronics industry as it adversely affects the process in some applications. The removal of boron is important in the production of potable/irrigation water in seawater desalination, with suggested limits of 0.5 ppm boron. The element boron exists in equilibrium as the borate monovalent anion B(OH)4- at higher pH and as non-ionized boric acid B(OH)3 at lower pH. The relative concentrations of borate and boric acid are dependent on pH, temperature and salinity. The borate ion becomes more prevalent at higher pH, higher salinity and higher temperature. The rejection of boron by RO is better for the borate ion due to its charge. The rejection of non-ionized boric acid is low due to its smaller size and lack of electric charge.