Efficient removal of organic matter and NH 4+ from pot ale by a combination of methane fermentation and biological denitrification and nitrification processes

Abstract

Malt whisky pot ale (MW) without saccharification was treated by methane fermentation using an upflow anaerobic filter (UAF) process. The maximum TOC removal rates using laboratory-scale and bench-scale systems were 12 and 14 g l −1 d −1, respectively, corresponding to removal efficiencies of 86 and 80%. NH 4 + remaining in the effluent of the anaerobic UAF process reactor was further treated by biological denitrificaton and nitrification with recirculation. A biological treatment system was used to effectively remove 97% of the remaining NH 4 +. The need for a supplemental electron donor such as methanol was precluded by recirculation through denitrification, activated sludge and nitrification unit processes. With this scenario, the activated sludge unit was effective in preventing blockage of the packed bed zone in the nitrification reactor due to growth of BOD oxidizing bacteria.