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

Oxidation-reduction (redox) condition is an important parameter in the proc essing 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 pote ntial health hazards and corrosive attack on concrete. Using solid adsorben t preconcentration and gas chromatographic methods, the quantity and compos ition 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 t he 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-H = -220 mV), In c ontrast, gas samples from sludge suspensions in microcosms maintained at re dox potential representing aerobic/anaerobic transition (microaerophilic) z one (E-H = +370 mV) hydrogen sulfide was not detectable, Considerable metha nethiol (ng S/g dry sludge/h) and dimethyl sulfide production (ng S/g dry s ludge/h) were measured in moderately reduced wastewater sludge. Only low le vels (less than 20.0 ng S/g dry sludge/h) of carbonyl sulfide and carbon di sulfide emission were evolved at the redox levels studied.