Studies on the Treatment of Night Soil. VIII. Removal of Volatile Fatty Acids by Bacteria Isolated from Aerobic Treatment Plant of Undiluted Night Soil

Abstract

The mechanism of the removal of night soil components by bacteria at the aerobic treatment plant of undiluted night soil was studied. For the removal of volatile fatty acids by bacteria iselated from this plant, E. coli. communior, B. megaterium, and propionic acid-utilizing bacteria were examined. Dissimilation rates for acetic acid and propionic acid by E. coli were 41.1% and 49.1%, respectively, but butyric acid was not used. From the removal pattern of these acids by E. coli, it was recognized that acetic acid inhibited the removal of propionic acid. Dissimilation rates for acetic acid by B. megaterium was 20.3% but propionic acid and butyric acid could not be used. In the case of propionic acid-utilizing bacteria, dissimilation rates for acetic, propionic, and butyric acids were 50.0%, 62.9%, and 38.2%, respectively. These rates were higher than those by E. coli and B. megaterium, and the speed of removal of propionic acid was higher than that of butyric acid by propionic acid-utilizing bacteria. In this plant, removal of substrates were carried out by all kinds of these bacteria.