Emissions of reduced gaseous sulfur compounds from wastewater sludge : Redox effects

Oxidation-reduction (redox) condition is an important parameter in the processing of organic carbon sources in wastewater treatment facilities. During the mineralization of organic wastes significant quantities of malodorous gases are produced in each step of wastewater treatment, and can cause potential health hazards and corrosive attack on concrete. Using solid adsorbent preconcentration and gas chromatographic methods, the quantity and composition of reduced malodorous sulfur gases emitted from wastewater sludge as influenced by redox conditions were determined in microcosms representing a redox range from very reducing to slightly aerobic. Hydrogen sulfide was the dominant volatile reduced sulfur compound measured under highly reduced redox conditions. The maximum rate of hydrogen sulfide emission (ng S/g dry sludge/h) was measured in the most reduced treatment (E sub(H) = -220 mV). In contrast, gas samples from sludge suspensions in microcosms maintained at redox potential representing aerobic/anaerobic transition (microaerophilic) zone (E sub(H) = +370 mV) hydrogen sulfide was not detectable. Considerable methanethiol (ng S/g dry sludge/h) and dimethyl sulfide production (ng S/g dry sludge/h) were measured in moderately reduced wastewater sludge. Only low levels (less than 20.0 ng S/g dry sludge/h) of carbonyl sulfide and carbon disulfide emission were evolved at the redox levels studied.