Sequential ultrasound and low-temperature thermal pretreatment: Process optimization and influence on sewage sludge solubilization, enzyme activity and anaerobic digestion.
The influence of sequential ultrasound and low-temperature (55°C) thermal pretreatment on sewage sludge solubilization, enzyme activity and anaerobic digestion was assessed. The pretreatment led to significant increases of 427-1030% and 230-674% in the soluble concentrations of carbohydrates and proteins, respectively, and 1.6-4.3 times higher enzymatic activities in the soluble phase of the sludge. Optimal conditions for chemical oxygen demand solubilization were determined at 59.3kg/L total solids (TS) concentration, 30,500kJ/kg TS specific energy and 13h thermal treatment time using response surface methodology. The methane yield after pretreatment increased up to 50% compared with the raw sewage sludge, whereas the maximum methane production rate was 1.3-1.8 times higher. An energy assessment showed that the increased methane yield compensated for energy consumption only under conditions where 500kJ/kg TS specific energy was used for ultrasound, with up to 24% higher electricity recovery.
Engineering and Environmental Biotechnology Group, Environmental Sciences Faculty and EULA-Chile Center, University of Concepción, P.O. Box 160-C, Concepción, Chile.
Patricio
P
Neumann
ESSBIO S.A., Av. Prat 199, Concepción, Chile.
Zenón
Z
González
Engineering and Environmental Biotechnology Group, Environmental Sciences Faculty and EULA-Chile Center, University of Concepción, P.O. Box 160-C, Concepción, Chile. Electronic address: glvidal@udec.cl.
Gladys
G
Vidal
D000693:Anaerobiosis; D008697:Methane / Q000378:metabolism; D012722:Sewage; D013696:Temperature; D014865:Waste Disposal, Fluid
D012722:Sewage; D008697:Methane
Anaerobic digestion; Hydrolysis; Pretreatment; Sewage sludge; Ultrasound