Olfactory quantification of sewage odors

Abstract

Procedures for measuring sewage odor are examined and a standard odor unit is recommended for odor quantification of a mixture of odorous gases. Field experiments involving simultaneous measurements of odor and hydrogen sulfide levels at two wastewater sites handling significantly different types of wastes were carried out. Odor level was measured with a dynamic olfactometer, while hydrogen sulfide concentration was determined with a paper-tape densitometer. Results reveal that the odor concentration (C(s)), of sewage air can be correlated with the hydrogen sulfide concentration [H2S] by an equation of the form C(s) = m[H2S](n), in which m an n are empirical parameters. Different values of m and n are obtained for the two sites investigated. The odor levels exerted by sewage air were also compared against that exerted by a commercially prepared hydrogen sulfide gas standard. These results reveal a natural masking effect of hydrogen sulfide odor in sewage air.