Odor determination at wastewater collection systems: Olfactometry versus H2S analyses

H2S is usually the main indicator parameter to assess when nuisance odors arise in wastewater handling systems. However, sampling and measurement of H2S need to be made with utmost care and analytical methods are neither easy nor cheap. Although Jerome meters from Arizona Instruments are used in some parts of the world, the cost and difficulty of measuring H2S in odorous gases is a general problem. It should also be kept in mind that a simple linear relationship between H2S concentrations and odor perception by the public is not available, especially in complex odorous gas mixtures. This leads to the conclusion that measuring the H2S alone is neither easy nor accurate in describing and resolving public complaints due to odors from wastewater collection and treatment systems. In this study, data for odors and H2S measurements from two pumping stations of the wastewater collection system of Cesme, Izmir, Turkey are evaluated. Concentrations of H2S were measured with chemical methods. Results indicated concentrations several orders of magnitude above the odor threshold level, which is generally accepted as 0.1 mu g/m(3) for pure H2S in air. The statistical relationships between analytical and sensory odor data were established. Correlations indicated power law relationships between odor and H2S concentrations (R-2 between 0.88-0.92). Steven's law between the intensity of human perception and concentration of stimulants is obeyed.