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Exploring the impact of bulk and substrate physics on hydrolysis rates and biogas yields of anaerobic digesters pretreated with thermal hydrolysis
Author(s) -
Manning Elizabeth,
Romero Adrian,
Li Baoqiang,
AlOmari Ahmed,
Higgins Matthew J.,
Riffat Rumana,
Murthy Sudhir,
De Clippeleir Haydee
Publication year - 2020
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.1002/wer.1184
Subject(s) - biogas , hydrolysis , anaerobic digestion , chemistry , thermal hydrolysis , chemical engineering , biodegradation , substrate (aquarium) , mixing (physics) , pulp and paper industry , yield (engineering) , waste management , materials science , sewage treatment , organic chemistry , composite material , sewage sludge treatment , methane , oceanography , physics , quantum mechanics , engineering , geology
This study evaluated the role of bulk and substrate physics on hydrolysis rates and biogas yields in anaerobic digestion (AD) pretreated by thermal hydrolysis (THP). Although THP decreases sludge viscosity, no evidence was found that bulk viscosity impacted the biogas yield or hydrolysis kinetics. In addition, no significant difference between the biogas yields for different total solids concentrations nor floc sizes was detected. However, increased mixing speeds did increase biogas yields. As a result of thermal treatment, the model protein, bovine serum albumin, was harder to degrade in terms of both overall biodegradability and hydrolysis rates when their macrostructures were changed from liquid to gel and to solid structures; the opposite was true for the model polysaccharide, amylopectin. These results demonstrated that hydrolysis in THP‐AD systems was impacted mostly by the physical properties of the substrate (gelation) rather than the bulk physical properties within the digester. Practitioner points Bulk viscosity does not significantly impact hydrolysis efficiency (biogas yield). However, mixing speed impacts hydrolysis beyond biogas holdup effect. Increasing the amount of substrate–microbe collisions through increasing biomass concentration does not have an impact on hydrolysis efficiency or biogas yield. Proteins are harder to degrade when macrostructure changes from liquid to gel/solid as a result of heat treatment. Polysaccharides are easier to degrade when macrostructure changes from liquid to gel/solid as a result of heat treatment. The time required for digesters to reach peak biogas production rates increased with decreasing specific surface available on gel and solid structures.