Shochu Distillery Wastewater Treatment using Methane Fermentor Incorporating Ultrafiitration Membrane Separator

Abstract

Using a pilot-scale methane fermentor incorporating an ultrafiltration membrane separator, we studied on Shochu distillery wastewater treatment. In order to avoid inhibition by NH₄⁺, the fermentor was fed with diluted wastewater. When the membrane separator worked effectively, a high concentration of microorganisms in the fermentor was maintained and the performance of the fermentor was stable to obtain a digested gas yield from 0.4 to 0.6m³/kg-VS and a VA concentration of the efnuent from 1000 to 2000mg/l. However, when the filtration rate of the membrane (flux) did not correspond to the increase of the feeding rate, the membrane flushing was frequently conducted, which resulted in drainage of the fermented liquid in the separator's pipe lines. Consequently the concentration of microorganisms decreased and the methane fermentation process was inhibited by the accumulation of VA. On the other hand, it was shown that the NH₄⁺ concentration was maintained at ca. 2000mg/l to avoid NH₄⁺ inhibition by feeding diluted wastewater. As a result, this fermentor showed that the design value of the loading rates of VS was determined to be between 4.8 and 8.0kg-VS/m³·d for obtaining a high yield or production rate of gases and 2.5 and 4.8kg-VS/m³·d for a high VA removal ratio, respectively.