ASBR with mechanical agitation and draft tube: Operating feasibility applied to wastewater treatment

Abstract

An investigation was carried out on anaerobic sequencing batch reactor (ASBR) configurations treating low-strength (synthetic wastewater) and high-strength wastewater (cheese whey) containing granulated biomass in systems with and without draft tube. Assays were performed at 30°C and feeding occurred in 10 min in 8-h cycles. In each cycle 2.0 l medium was fed and the total medium volume in the reactor was 5.0 L. Wastewaters used were synthetic wastewater (low-strength) with 800 mgCOD/L and cheese whey (high-strength) at 1000, 2000 and 4000 mgCOD/L. The stirring system consisted of impellers placed inside an internal axial-flow-promoting tube (draft tube). The diameter of the draft tube corresponded to 1/3 the reactor diameter. Impellers used for treating the synthetic wastewater were 45°-inclined-flat-blade paddle and three-blade helix impeller. For the treatment of cheese whey only the three-blade helix impeller was used. Results showed that in the treatment of both synthetic wastewater and cheese whey use of a draft tube increased organic matter removal efficiency, quantified by the kinetic constants obtained by fitting a first order kinetic model to the experimental values. Hence, the conclusion arrived at was that the presence of the draft tube in the ASBR, treating low-strength and high-strength wastewaters with granulated biomass, significantly increased mass transfer efficiency between the liquid and solid phases. © 2013 Nova Science Publishers, Inc.