Drinking water denitrification using a membrane bioreactor

Abstract

A membrane bioreactor (MBR) was investigated for denitrification of nitrate (NO 3 −) contaminated drinking water. In the MBR, NO 3 − contaminated water flows through the lumen of tubular microporous membranes and NO 3 − 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 NO 3 − 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 NO 3 − mass transfer in the MBR, investigate the effect of shell and lumen velocity on NO 3 − mass transfer and investigate the effects of NO 3 − and organic carbon loading on denitrification rate and product water quality. A mathematical model of NO 3 − mass transfer was developed, which fit abiotic mass transfer data well. Correlations of dimensionless parameters were found to underestimate the overall NO 3 − mass transfer coefficient by 30–45%. The MBR achieved over 99% NO 3 − removal at an influent concentration of 200 mg NO 3 −-N L −1. The average NO 3 − flux to the biomass was 6.1 g NO 3 −-N m −2 d −1. Low effluent turbidity was achieved; however, approximately 8% of the added methanol partitioned into the product water.