Effectiveness of Selected Chemicals for Controlling Emission of Malodorous Sulfur Gases in Sewage Sludge

Abstract

The effectiveness of various oxidants or redox buffers (ferric chloride, sodium hypochlorite, potassium permanganate, hydrogen peroxide and potassium nitrate) for controlling or reducing emission of reduced sulfur gases (hydrogen sulfide, carbonyl sulfide, methanethiol, dimethyl sulfide and carbon disulfide) produced from sewage sludge collected from a wastewater treatment plant was studied under laboratory conditions. Sludge was treated with 0, 30, 300 and 1000 ppm of each chemical and changes in emission of the various reduced sulfur gases were monitored over a period of 24 hours. Potassium permanganate and hydrogen peroxide were shown to be the best chemicals for reducing hydrogen sulfide (the dominant reduced sulfur gas measured) emission. Sodium hypochlorite was also effective in reducing hydrogen sulfide emission followed by the ferric chloride addition. Since considerably smaller quantities of other reduced sulfur gases were evolved, the influence of the various chemical additions were not as significant as the reduction observed for hydrogen sulfide emission. Potassium permanganate and hydrogen peroxide were effective in reducing methanethiol and dimethyl sulfide emission. To a lesser degree sodium hypochlorite and ferric chloride also reduced emission of these two reduced sulfur gases. Potassium nitrate had no effect on reducing hydrogen sulfide or any of the reduced sulfur gases over the 24 hour experimental period. Each of the chemicals used in the study had a little or no effect in reducing carbonyl sulfide and carbon disulfide emission from the sludge material.