Influence of agitation rate on the performance of an anaerobic sequencing batch reactor containing granulated biomass treating low-strength wastewater

Abstract

The present work reports on the influence of the mechanical agitation rates on the performance of a stirred anaerobic sequencing batch reactor with a six-vertical-blade disk turbine on the basis of chemical oxygen demand (COD). The reactor containing granulated biomass treating synthetic domestic wastewater was operated at 30 °C and an 8-h cycle was applied to treat approximately 2.0 l of the synthetic substrate with COD of nearly 500 mg/l. The studied agitation rates ranged from no agitation to 75 rev./min. The system attained non-filtered and filtered substrate removal efficiency of 80 and 88%, respectively, at the agitation rate of 50 rev./min, presenting a relatively good solid retention and no granule break-up. Moreover, the use of agitation mainly increased the efficiency throughout the cycle of the reactor and, consequently, enabled reduction of the total cycle time. An empirical equation and a first order kinetic model with a residual organic matter concentration were proposed to analyze the influence of agitation rates on the reactor's performance. © 2002 Elsevier Science Ltd. All rights reserved.