Removal of bromate and associated anions from water by Donnan dialysis with anion-exchange membrane

Abstract

Ozone is considered as a strongest oxidizer and disinfectant applied in drinking water treatment. If the water to be ozonated contains bromides, this will lead to the formation of bromates, ions with potential carcinogenic implications to human organisms. We proposed Donnan dialysis process with an anion-exchange membrane to remove bromate ions from water. The rate and efficiency of anion removal (BrO3 –, SO4 2–, HCO3 –) from the natural water were examined with the use of two types of anion-exchange membranes: Selemion AMV and Neosepta ACS and with the use of varying salt concentration in the receiver: 50, 100 or 200 mM NaCl. Bromate ions were removed from natural water with 90% efficiency in the process with the Neosepta ACS (of a highly cross-linked surface layer) when salt concentration in the receiver equalled 100 mM NaCl. The application of the Selemion AMV yielded similar efficiency of bromate removal (94%) but NaCl concentration in the receiver had to be twice as high as with Neosepta ACS (200 mM). However, Neosepta ACS rejected bicarbonates ranged between 35 and 53% and almost entirely rejected sulphates (in 97%). In turn, the Selemion AMV enabled flow of sulphates (93% of removal) and bicarbonates (ranged from 60 to 87% of removal).