Anaerobic fixed film wastewater treatment

Abstract The anaerobic methane fermentation process has long been used in the field of wastewater engineering in sludge processing, mainly for waste stabilization and solids reduction. Recently, major advances in the fundamental understanding of the process microbiology and biochemistry, along with the development of new reactor configurations have promoted a resurgence of interest in the use of this technology for the processing of liquid industrial and municipal wastewaters. Three of these new processes, the anaerobic filter, expanded/fluidized bed, and upflow anaerobic sludge blanket, are discussed. Each of these processes is a fixed film process, which enables the attainment of high solids retention times for good system efficiency and stability, with low hydraulic retention times for system economy. Fixed film anaerobic processes are able to realize many of the benefits of anaerobic processes while overcoming many of the problems historically associated with anaerobic processes. Each of the processes is described, and examples are presented for industrial and municipal applications. Finally, the processes are qualitatively compared. At present, it is not possible to say which reactor configuration is best. In fact, the selection is often dependent on wastewater characteristics, local factors, and several other factors. More full-scale data and operating experience along with basic research needs are needed to clarify further this situation, and to design these systems optimally.