Ion Exchange Membrane Bioreactor for Selective Removal of Nitrate from Driking Water:Control of Ion Fluxes and Process Performance

摘要

An ion exchange membrane bioreactor (IEMB),consisting of a monoanion permselective membrane dialyzer coupled to a stirred anoxic vessel with an enriched mixed dentrifying culture,has been studied for nitrate removal from drinking water.The influence of nitrate and chloride concentrations on the selectivity of nitrate transport in the IEMB process was investigated.With appropriate dosing of chloride ions to the IEMB biocompartment,it was possible to regulated the net bicarbonate flux in the system,thus maintaining the bicarbonate concentration in the treated water at the desired level.The latter was not possible to achieve in Donnan dialysis,operated as a single process in which,besides the lower nitrate removal efficiency found,bicarbonate was co-extracted together with nitrate fromthe polluted water stream.Residual carbon source(ethanol)and nitrite wer not detected in the treated water produced in the IEMB system.With a concentration of nitrate in the plluted water three times higher than the maximum contaminant level of 50mg L~(-1) allowed,the IEMB process was successfully operated for a period fo a month before exceeding this limit.