The Gas Chromatographic Analysis of the Digestion Gases and the Offensive Compounds Produced in the Process of the Night Soil Treatments

Abstract

In this paper, the gas chromatographic analysis of the offensive components in the night soil treatment plants was carried out at Funaigun Plant in Kyoto Prefecture, Toyonaka & Itami Plant, Neyagawa Plant and Takatsuki Plant in Osaka Prefecture, where the anaerobic digestion method has been employed.The results of the investigation were as follows:1) The gases in the digestion tanks contained 20.6 to 27.4% CO2, 51.7 to 66.0% CH4 and 0.9 to 2.0% O2. The gases in the tightly sealed trickling filter contained 15.0% CO2, 30.4% CH4 and 20.4% O2.2) The determination of aliphatic amines, ammonia, hydrogen sulfide was carried out using the Triton X-100 and Quadol column after the samples were collected into the distilled water. Total amines (40.2 to 61.0ppm), ammonia (440 to 1, 220ppm) and hydrogen sulfide (3, 180 to 8, 060ppm) were found in the digestion tanks.3) The determination of aliphatic aldehydes and ethanol was carried out using Tricresyl Phosphate+Polyethylene Glycol and Ucon oil 50HB column. The concentration of total aldehydes was 16.6 to 25.0ppm and ethanol was 38.8 to 46.6ppm in the digestion tanks.4) The determination of lower aliphatic mercaptans and thioether was carried out using Tricresyl Phosphate and Ucon oil 50HB column. The concentration of total mercaptans and thioether was 8.6 to 12.0ppm in the digestion tanks.5) The determination of indol and skatol was carried out using Silicon DC HV grease and Silicon KF-96 column, after they were collected into benzene. The total amount of indols was 6.1 to 21.5×10-2ppm.6) A tentative method to evaluate the intensity of offensive odor was proposed. The ratio of the observed values to the olfactory thresholds was calculated for each offensive component. It was 104 to 105 for marcaptans and skatol, and was 103 for hydrogen sulfide. But the ratio for ammonia was found very low.From these results, it might be suggested that mercaptans and skatol in the digestion tanks have large effects but ammonia has little effcts to the human olfaction.