Odor is the biggest concern and restraint in wastewater and similar industries. A solid-phase microextraction technique was applied to analyze several predetermined odorants. A carboxen-polydimethylsiloxane fiber was used for the analysis of an amine, and several sulfur compounds, and a polyacrylate fiber for the analysis of predetermined volatile fatty acids. Calibration curves were developed within the ranges 0.0004 and 2.9943 ppmv for sulfides and 0.0228 and 2.3309 ppmv for fatty acids and showed R2 greater than 0.99 . A one year study of the odorants and operation parameters was carried out in a large wastewater treatment plant to develop a correlation between odorants and sludge characteristics to determine factors controlling odor production. Methyl mercaptan and dimethyl sulfide showed highest odor indexes meaning higher human perception. A correlation was found between ORP and sulfides. The DAF thickened sludge and the blended sludge had the highest odor indexes and the lowest ORP's measured.