Studies on the Treatment of Night Soil. IV. Transition of Volatile Fatty Acids as a Component of BOD Substances in Feces and Sewage

Abstract

Quantitative separation of volatile fatty acids in feces and sewage was examined by gas chromatography, using 5% free fatty acid phase on Chamelite CS as the column packing and a hydrogen flame ionization detector. This method was applied to the examination of the daily variation of volatile fatty acids and BOD in the treated water from each process of night-soil treatment plants. The concentration of total volatile fatty acids in fresh feces was 6700 ppm and they consisted mostly of acetic, propionic, and butyric acids. After a lapse of 19 days, the concentration of total volatile fatty acids amounted to 4600 ppm, and acetic acid occupied 80% of them. Acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids were detected in the samples obtained from the inlet tank and influent. In the effluent, most of them was acetic acid, and propionic acid was in small quantities. In the process of various treatment plants, the tendency for BOD value in the samples to decrease was similar to that of volatile fatty acids, and acetic acid was the main component in the volatile fatty acids.