High rates conversions of soluble organics with a thermophilic anaerobic attached film expanded bed

Anaerobic digestion has had limited application because of slow bacterial growth rates, relatively low organic removal ef ficiencies, and the sensitivity of the microorganisms to toxic materials, temperature, and pH. Over the last decade, however, interest in anaerobic digestion has increased. Recent efforts have emphasized: the fundamentals of anaer obic digestion; improvements of the more conventional tech niques such as digestion of animal waste and other agricultural residues and secondary wastewater sludge; reactor design.1-3 The anaerobic attached-film expanded bed (AAFEB) process, de veloped by Jewell and colleagues, was in fact a natural devel opment from existing processes and information on the fun damentals of process limitations.4 This process accumulates large quantities of microbial biomass (30 to 40 kg/m3 volatile solids (VS)), which in turn enables it to efficiently convert dilute sub strates (such as wastewater) to biogas, with minimum sludge yields.