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This study shows for the first time that overlooked mg/L concentrations of industrial dimethyl sulfoxide (DMSO) waste residues in sewage can cause "rotten cabbage" odor problems bydimethyl sulfide (DMS) in conventional municipal wastewater treatment. In laboratory studies, incubation of activated sludge with 1-10 mg/L DMSO in bottles produced dimethyl sulfide (DMS) at concentrations that exceeded the odor threshold by approximately 4 orders of magnitude in the headspace gas. Aeration at a rate of 6 m3 air/m3 sludge resulted in emission of the DMS into the exhaust air in a manner analogous to that of an activated sludge aeration tank. A field study atthe NEWPCP sewage treatment plant in Philadelphia found DMSO levels intermittently peaking as high as 2400 mg/L in sewage near an industrial discharger. After 3 h, the DMSO concentration in the influent to the aeration tank rose from a baseline level of less than 0.01 mg/L to a level of 5.6 mg/L and the DMS concentration in the mixed liquor rose from less than 0.01 to 0.2 mg/L. Finding this link between the intermittent occurrence of DMSO residues in influent of the treatment plant and the odorant DMS in the aeration tank was the keyto understanding and eliminating the intermittent "canned corn" or "rotten cabbage" odor emissions from the aeration tank that had randomly plagued this plant and its city neighborhood for two decades. Sewage authorities should consider having wastewater samples analyzed for DMSO and DMS to check for this possible odor problem and to determine whether DMSO emission thresholds should be established to limit odor generation at sewage treatment plants.

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The purpose of the study was to characterize natural ventilation in full-scale gravity collection system components while measuring other parameters related to ventilation. Experiments were completed at four different locations in the wastewater collection systems of Los Angeles County Sanitation Districts, Los Angeles, California, and the King County Wastewater Treatment District, Seattle, Washington. The subject components were concrete gravity pipes ranging in diameter from 0.8 to 2.4 m (33 to 96 in.). Air velocity was measured in each pipe using a carbon-monoxide pulse tracer method. Air velocity was measured entering or exiting the components at vents using a standpipe and hotwire anemometer arrangement. Ambient wind speed, temperature, and relative humidity; headspace temperature and relative humidity; and wastewater flow and temperature were measured. The field experiments resulted in a large database of measured ventilation and related parameters characterizing ventilation in full-scale gravity sewers. Measured ventilation rates ranged from 23 to 840 L/s. The experimental data was used to evaluate existing ventilation models. Three models that were based upon empirical extrapolation, computational fluid dynamics, and thermodynamics, respectively, were evaluated based on predictive accuracy compared to the measured data. Strengths and weaknesses in each model were found and these observations were used to propose a concept for an improved ventilation model. Water Environ. Res., 83, 265 (2011).

The main objective of this research was to test the hypothesis that bioavailable protein, and, more specifically, the sulfur-containing amino acids within the protein, can be degraded by proteolytic enzymes to produce odor causing compounds, mainly volatile sulfur compounds (VSCs), during biosolids storage. Another objective of this research was to examine the factors that affect protein and amino acid content from different full-scale treatment processes. To achieve these objectives, samples of digester effluent and cake solids were collected at 11 different wastewater treatment plants in North America and the samples were analyzed for protein and amino acid content as well as general protein degrading enzyme activity. Ten of the plants used mesophilic anaerobic digestion and one plant used thermophilic anaerobic digestion. At the same time, cake samples were stored using headspace bottles, and the concentration of VSCs were measured using GC/MS and olfactometry measurements were made by a trained odor panel. The results showed the bound cake protein content from the different sites was well correlated with VSC production as well as the detection threshold (DT) measured by the odor panel. In addition, the sulfur containing amino acid, methionine, was very well correlated with the VSC concentration and well correlated with DT. Protein degrading enzyme activity was not well correlated to odorant production. Operational parameters such as solids retention time generally did not correlate well with the biochemical constituents. However, the total iron content of a digester was negatively correlated with the bound protein concentration, suggesting greater amounts of Fe in the biosolids decreased the amount of protein that could be extracted from the cake.