Influence of the liquid-phase mass transfer on the performance of a packed-bed bioreactor for wastewater treatment

This paper reports on the influence of the liquid-phase mass transfer on th e performance of a horizontal-flow, anaerobic, immobilized-biomass (HAIB) r eactor treating low-strength wastewater. The HAIB reactor was subjected to liquid superficial velocities (upsilon (s)) ranging from 10 to 50 cm h(-1), corresponding to hydraulic detention time (theta (h)) of 10-2 h. The best performance was achieved at an overall theta (h) of 3.3 h due to the interd ependence of biochemical reactions and mass transfer mechanisms for process optimization. The HAIB reactor was provided with four intermediate samplin g ports, and the values of upsilon (s) were fixed to permit sampling at dif ferent ports corresponding to theta (h) of 2 h as upsilon (s) increased. Th e chemical oxygen demand removal (COD) efficiencies increased from 68% to 8 2% with the increase of upsilon (s) from 10 to 50 cm h(-1). It could be con cluded that the performance of the HAIB reactor was improved significantly by increasing upsilon (s), thus decreasing the liquid-phase mass transfer r esistance. (C) 2001 Elsevier Science Ltd. All rights reserved.