Treatment of phenol in an anaerobic fluidized bed reactor (AFBR): continuous and batch regime

Results of this study describe the feasibility of anaerobic treatment of highly concentrated phenol synthetic wastewater using an anaerobic fluidized bed reactor (AFBR) in both continuous and batch modes. Wastewater with a maximum load of 2,100 mg C center dot l(-1) was prepared using phenol (maximum concentration of 1,600 mg C center dot l(-1)) as substrate and a mixture of acetic, propionic and butyric acids (500 mg C center dot l(-1)) as co-substrate. AFBR reached total organic carbon (TOC) and phenol removal efficiency over 95% treating the highest organic loading rate (OLR) containing phenol studied for this kind of reactor (5.03 g C center dot l(-1)center dot d(-1)). The phenol loading rate rise caused volumetric biogas rate increase up to 4.4 l center dot l(-1)center dot d(-1) (average yield of 0.28 l CH4 center dot g(-1) CODremoved) as well as variation in the biogas composition; the CO2 percentage increased while the CH4 percentage decreased. Morphological examination of the bioparticles at 4.10 g C center dot l(-1)center dot d(-1), revealed significant differences in the biofilm structure, microbial colonization and bacterial morphological type development. The five batch assays showed that phenol degradation may be favoured by the presence of volatile fatty acids (VFAs) (co-metabolism), whereas VFAs degradation may be inhibited by phenol. AFBR reached initial phenol degradation velocity of 0.25 mg C center dot l(-1)center dot min(-1).