Biological Denitrification of Groundwater by a Composite Membrane Bioreactor

Abstract

A composite membrane bioreactor (CMBR) integrating the immobilized cell technique and the membrane separation technology was developed for biological denitrification of groundwater. In CMBR the groundwater and external carbon source (ethanol solution) are separated by the composite membranes consisting of a microporous membrane facing the groundwater and a plate-like immobilized cell membrane facing the ethanol solution. Nitrate and ethanol molecules diffused from the respective frames into the plate-like immobilized cell membrane where nitrate was reduced to gaseous nitrogen by the denitrifying bacteria present there with ethanol as carbon source. The microporous membrane attached to one side of plate-like immobilized cell membrane was used to separate product water from a plate-like immobilized cell membrane for retention of the disaggregated bacteria. Using the CMBR for groundwater denitrification, the over dosed external carbon source can be reused, and its treatment performance was perfect during continuous operation up to 98 days, and almost all effluent NO3--N, NO2--N, and CODMn concentrations are below their maximum contaminant levels as the NO3--N loading was less than 4.968 g.m-2.d-1.