Drinking water denitrification using a membrane bioreactor.
A membrane bioreactor (MBR) was investigated for denitrification of nitrate (NO3(-)) contaminated drinking water. In the MBR, NO3(-) contaminated water flows through the lumen of tubular microporous membranes and NO3(-) diffuses through the membrane pores. Denitrification takes place on the shell side of the membranes, creating a driving force for mass transfer. The microporous membranes provide a high NO3(-) permeability, while separating the treated water from the microbial process, reducing carryover of organic carbon and sloughed biomass to the product water. Specific objectives of this research were to develop a model for NO3(-) mass transfer in the MBR, investigate the effect of shell and lumen velocity on NO3(-) mass transfer and investigate the effects of NO3(-) and organic carbon loading on denitrification rate and product water quality. A mathematical model of NO3(-) mass transfer was developed, which fit abiotic mass transfer data well. Correlations of dimensionless parameters were found to underestimate the overall NO3(-) mass transfer coefficient by 30-45%. The MBR achieved over 99% NO3(-) removal at an influent concentration of 200 mg NO3(-)-NL(-1). The average NO3- flux to the biomass was 6.1g NO3(-)-Nm(-2)d(-1). Low effluent turbidity was achieved; however, approximately 8% of the added methanol partitioned into the product water.