Capacity Increase without Invasive Retrofits – Maximize Digester Efficiency with Biological Hydrolysis

Existing infrastructure in place to anaerobically digest domestic sewage sludge typically utilizes common anaerobic reactors to accomplish all phases of anaerobic digestion, namely hydrolysis, fermentation, Acetogenesis, dehydrogenation and methane fermentation. It is widely accepted that hydrolysis is the rate limiting step of the overall anaerobic digestion process, and therefore to accomplish satisfactory stabilization of sludge, extended hydraulic retention times of sludge are designed into the digester volume. Biological Hydrolysis technology, which has been pioneered in the United Kingdom at the beginning of this century addresses this rate limiting step by adding a set of serial flow reactors up front of a mesophilic anaerobic digester, to provide optimum conditions to maximize the rate of sludge hydrolysis. When implemented, Biological Hydrolysis shows to increase digester capacity by 2 to 3 times by reducing the required digester retention time, as well as increases biogas yield from sludge. Furthermore, as a result of the increased biogas yield, the remaining biosolids exiting a digester is reduced. This paper will examine the performance of existing wastewater treatment plants which have employed biological hydrolysis and the benefits these plants experience.