Odor-causing volatile organic compounds in wastewater treatment plant units and sludge management areas

Odors due to malodorous gas and vapor emissions from units of Izmir Wastewater Treatment Plant (WWTP) were studied and evaluated with respect to chemical composition. Altogether 29 target compounds consisting of 4 different groups of chemicals were identified and quantified in the odorous gas samples from wastewater and sludges. Total volatile malodorous organic compounds (VMOC) consisted of reduced sulfur compounds (RSCs) and different volatile organic compounds (VOCs) including volatile organic compounds (VOCs), aldehydes, monoaromatics (BTX) and some halogenated organics. Among these components the most abundant group was the monoaromatics (69% of the total VOC). A statistically significant linear relationship was found between odor concentrations determined by olfactometry and total VOC concentrations (r(2) = 0.89, n = 5, P < 0.05) in the samples of odorous gases. Based on the odor contribution ratios of the compounds studied, the results of the study revealed that hydrogen sulfide, propanal and toluene were dominating in the odor emissions and these were explaining 99% of the variability in odor concentrations (r(2) = 0.99, n = 5, P 0.05). It was shown that not only the hydrogen sulfide and RSCs but also other organics were important in forming the odors from sludge units and sludge management areas.