Removal of Nitrogen in the Acidogenesis Phase and Characteristics of Methane Fermentation of Cattle Manure Using the Liquid from that Phase

Abstract

An economical process is needed for the treatment of digested liquid to overcome the problems that ammonium nitrogen remains at high concentrations and carbon sources are reduced in the liquid. To develop this process, the author studied a process for the treatment of cattle manure that utilizes in combination the biological nitrification/denitrification process for the removal of nitrogen in wastewater and the two-phase methane fermentation process. This process reduces the amount of wastewater treatment by returning the digested liquid to adjust the concentration of input organic wastes. The author added 1 g/L of nitrate nitrogen to cattle excreta, and confirmed that the nitrate nitrogen was not detected in the liquid in the acid-producing phase. In this instance, dissimilatory nitrate reduction as well as denitrification was observed. The concentration of acetic acid in the input increased from 3.8 g/L to 6.8 g/L after the acid-producing reaction, indicating that the essential acid-producing function was carried out. In the methane fermentation using the liquid in the acidproducing phase, 463 L/kg-VS of biogas was produced, the concentration of methane was 64%, and no adverse effects were observed even when the denitrification function was provided.