ADSORPTION OF TOXIC SHOCKS ON CARRIERS IN ANAEROBIC BIOFILM FLUIDIZED-BED REACTORS

The influence of different carrier materials on the performance of single stage anaerobic biofilm fluidized bed reactors by toxic shock loadings was studied in parallel experiments. The carrier materials investigated were porous glass (Siran), quartz sand, pumice, shale, activated carbon and anthracite. Since the composition and morphology of the biofilm is influenced by the individual wastewater, vapor condensate from a sulfite cellulose process and mixed brewery wastewaters were used as substrates. The phenol adsorption characteristics were measured on bare and biofilm-coated carriers. Biofilm-coated carriers adsorbed larger amounts of phenol than bare carriers. It was observed that the biofilm morphology and the corresponding adsorption capacity of biofilm carriers depended on the individual wastewater characteristics. It was also shown that activated carbon (and partly anthracite) adsorbed large amounts of phenol, mostly irreversibly. The performance of the individual reactors was studied under short-term dynamic phenol shocks (constant hydraulic retention time (HRT) 10 h, loading rate increase from 12 to 20 kg COD/m3d during the shock period of ca. 10 h). During the toxic loading in continuous operation, an increase of phenol concentration was observed in the effluent, coupled with an up to 20% decrease in the gas production rates. During this period, acetic acid accumulation was also observed, indicating the inhibition of methane formation. Following the shock, all reactors showed a relatively rapid recovery to the original activity after 2-3 hydraulic retention times.