Impact of High Shear Solids Processing on Production of Volatile Sulfur Compounds From Anaerobically Digested Biosolids

Abstract

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.

Quantification of viable but nonculturable Salmonella spp. and Shigella spp. during sludge anaerobic digestion and their reactivation during cake storage

“…The reactivation of pathogenic indicators in the digested sludge resulted from the change in physicochemical property of effluent sludge, such as the removal of VFAs, and NH 4 + ‐N, release of extra nutrients and shearing force change during the dewatering process (Murthy et al . ; Qi et al . ; Chen et al .…”

Evaluation of Odor Characteristics of Heat‐Dried Biosolids Product

“…The alldigested pellets were less persistent with added moisture, but more persistent with soil amendment. Recently, Murthy et al (2002) showed that odor compound production from digested biosolids peak after several days (approximately 1 week) of storage. The storage time used in these experiments was limited to 24 hours.…”

Effect of Dewatering on Fecal Coliforms and Methanogens in Anaerobically Digested Biosolids

“…Some researchers have shown that the centrifugal dewatering process increases odor emissions from biosolids (Murthy et al, 2002;Murthy et al, 2003;Higgins et al, 2003). These studies have implicated shearing forces during centrifugation.…”