Anaerobic thermophilic fluidized bed treatment of industrial wastewater:: Effect of F:M relationship

This paper describes the thermophilic (55 degrees c) anaerobic biodegradation of wine distillery wastewater (vinasses) in a laboratory fluidized bed reactor (AFB) with a porous support media. The experimental protocol was defined to examine the effect of the increase of organic loading rate on the efficiency of AFB and to report on its steady-state performance. The AFB reactor was subjected to a programme of steady-state operation over a range of hydraulic retention time, HRTs, of 2.55 - 0.37 days and organic loaging rate, OLRs, up to 5.88 kgCOD/m(3).d in order to evaluate its treatment capacity. Porous support media particles used in AFB were previously colonized in semicontinuous anaerobic fixed-bed reactors treating wine-vinasses. The AFB reactor was initially operated with organic loading rate of 5.88 kgCOD/m(3).d and HRT of 2.55 days. The COD removal efficiency was found to be 96.5% in the reactor while the volumetric methane produced in the digester reached 1.08 m(3)/m(3).d. Over 94 days operating period, an OLR of 32 kgCOD/m(3).d at an F:M ratio of 0.55 kgCOD/kgVS(all).d was achieved with 81.5% COD removal efficiency in the experimental AFB reactor. At this moment, the methane content of biogas produced in the digester reached 9.0 m(3)/m(3).d. Furthermore, the increase of OLR at 40.5 kgCOD/m(3).d, corresponding to 0.37 days HRT, provokes malfunction of the process with a sudden drop in COD removal efficiency and stopping the biogas production. (C) 1999 Elsevier Science Ltd. All rights reserved.