Sulfur-containing odorants and the effects of high salinity in anaerobically digested biosolids.
The ultimate goal in biosolids management is to reuse them in a beneficial way while taking necessary precautions for environmental and public health. Land application of biosolids is an economically and environmentally attractive means of attaining this goal, maintaining soil fertility by recycling mineral and organic constituents of wastes in a sustainable manner. At present, approximately 8 million dry tons of wastewater biosolids are generated in the United States annually, and over sixty percent of it is land applied.; However, odors generated from biosolids are major impediments to the acceptance of land application practices. Major odor compounds released from biosolids are organic amines and reduced sulfur compounds, such as methane thiol, dimethyl sulfide, dimethyl disulfide, carbon disulfide and hydrogen sulfide. Though the precursors of these odorants have been deduced, the actual causes of their generation had not been demonstrated in previous research.; In this work, it was hypothesized that more severe odors arise in anaerobic digesters under upset conditions---specifically, due to transient conditions such as high salinity. The goal of this research was to test this hypothesis for sulfur-containing odorants for which the human nose has the lowest threshold levels for detection.; To survive osmotic stresses, microbial cells usually adapt by accumulating specific solutes, called osmoregulators or compatible solutes. These solutes balance the osmotic pressure and protect intracellular enzymes against the inhibitory effects of osmotic stress. This research thus evaluated the feasibility of osmoregulator addition to control odor production from biosolids under high salinity conditions.; Effects of high salinity on odor production were tested with batch experiments conducted under anaerobic conditions. Headspace odor analysis was performed by solid-phase microextraction (SPME), followed by gas chromatography-mass spectrometry analyses. The sulfur-containing amino acids cysteine and methionine, and two common osmoregulators, choline and betaine, increased sulfur odor production more vigorously under high salinity conditions. Results suggested that the degradation of the sulfur-containing amino acids and amino acid derivatives represent significant sources of sulfurous odors.; Odor production in an upset digester is most likely a result of severe inhibition of one or more group of microorganisms. Since methanogens are recognized as the most sensitive group of microorganisms in these processes, their role in sulfur-containing odor production/consumption was assessed by monitoring the production of sulfur-containing odorants from digested biosolids when methanogens are selectively inhibited by bromoethanesulfonic acid (BES).; Inhibition of methanogens had a dramatic increasing effect on the production of sulfur-containing odorants. Fatty acid methyl ester (FAME) analysis was used to confirm microbial population profiles and the inhibition of methanogens. FAME results not only demonstrated a clear effect of inhibition of methanogens on microbial population profile, but also pointed out the importance of digestion time.; Results of batch tests showed that transient conditions play an important role in odor production by altering population dynamics. Alternative osmoregulators (trehalose and potassium ion) that do not contain sulfur or nitrogen were tested for odor control purposes. Trehalose mostly served as carbon and energy source rather than osmoregulator. Rather than controlling, trehalose dramatically increased the production of all the sulfur compounds of interest in inhibited and uninhibited biosolids under upset and normal conditions.; Potassium reduced the total production of sulfur-containing odors in digested biosolids under high salinity conditions, especially when methanogens were inhibited. This pointed out that potassium alleviated the inhibitor effect of high salinity on other microorganisms. The use of pota......
【作者单位】: University of Delaware.
【关 键 词】: Sulfur-containing odorants and the effects of high salinity in anaerobically digested biosolids.
【授予学位单位】: University of Delaware.
【学科】: Engineering, Environmental.
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