IMPACT OF HIGH SHEAR SOLIDS PROCESSING ON PRODUCTION OF VOLATILE SULFUR COMPOUNDS FROM ANAEROBICALLY DIGESTED BIOSOLIDS

The emission of volatile sulfur compounds (VSCs) was evaluated for stored anaerobically digested biosolids cakes. This evaluation was conducted on the headspace of anaerobically stored cakes obtained from two municipal wastewater treatment plants. The objective of this investigation was to determine the impact of high-shear solids processing on VSC production from digested biosolids. Experiments were conducted on biosolids obtained from full-scale lowand high-solids centrifuges, and from screw conveyors. The results of this study indicate that storage of biosolids obtained from high-solids centrifuges (high shear equipment) can produce 3 orders of magnitude more VSCs than biosolids obtained from low-solids centrifuge (low-shear equipment). Similarly, biosolids subject to a combination of centrifugation and screw conveyance (high-shear conveyance) produced as much as 3 orders of magnitude more VSCs than biosolids that were subject to centrifugation alone. These results verify the impact of biosolids shear on VSC production. Preliminary laboratory-scale experiments were also conducted to study the impact of biosolids shear and protein amendment on VSC production. These experiments demonstrated that storage of laboratory-sheared or protein amended biosolids resulted in greater VSC (specifically methyl mercaptan) production than the unaltered control. A model was developed that relates increase in biosolids shear during solids processing to increase labile protein. The subsequent hydrolysis of labile protein results in the formation of VSCs.