Measurement and Treatment of Nuisance Odors at Wastewater Treatment Plants
As population expansion has caused odorous industries to encroach on residential neighborhoods, measurement and control of odors has become essential. Wastewater treatment plants (WWTPs) are an odorous industry found in most communities and a proper understanding of the odorous compounds responsible is necessary to prevent odor nuisance. The primary objectives of this dissertation were to thoroughly evaluate and characterize nuisance odors at wastewater treatment plants and to evaluate the ability of a seashell biofiltration system to treat those types of odors. Odors at several WWTPs were evaluated through the use of the Odor Profile Method, using Odor Wheels to establish odor character and the Flavor Profile Analysis scale to measure odor intensity, and broad-spectrum gas chromatography with mass spectrometry (GC-MS) and olfactometry (GC-Sniff) in order to select the appropriate types of chemical compounds to be measured. Reduced sulfide compounds including hydrogen sulfide, methyl mercaptan, dimethyl sulfide, and dimethyl disulfide were typically found to be the major odorants detected. In addition to sulfide odors, musty odors and fecal odors were detected at many WWTP processes. A seashell biofiltration system was evaluated for its ability to treat some of the major odorants detected at WWTPs. Because seashells are composed of calcium carbonate, they are expected to provide buffering of sulfuric acid produced during the biodegradation of reduced sulfides. In the field, the system was able to successfully treat sulfide odors throughout the duration of the study. Hyphomicrobium and Thiobacillus species were found to be the main sulfide removing organisms in the field biofilter, and while the community composition changed with time, the biofilter still performed adequately. In the laboratory, the seashell biofiltration system was able to adequately remove hydrogen sulfide after seeding with a Pseudomonas organism. However, the biofilter began to support other microorganisms found in the laboratory that took over the biofilter following a pH decline of the system. In both the field and the laboratory, it was found that the pH of the recirculating water needed to be monitored and controlled which challenged the theoretical advantage of using a seashell media bed.