title: High pressure homogenization and two-phased anaerobic digestion for enhanced biogas conversion from municipal waste sludge.
abstract: This study compared advanced anaerobic digestion combining two-phased anaerobic digestion (2PAD) with high pressure homogenization (HPH) pretreatment to conventional anaerobic digestion of municipal sludge at laboratory scale. The study began with examination of thickened waste activated sludge (TWAS) solubilization due to HPH pretreatment at different pressure (0-12,000 psi) and chemical dose (0.009-0.036 g NaOH/g total solids). Homogenizing pressure was found as the most significant factor (p-value < 0.05) for increasing solubilization of particulate chemical oxygen demand (COD) and biopolymers in TWAS. Based on the preliminary results, a pretreatment with chemical dose of 0.009 g NaOH/g total solids and pressure of 12,000 psi was selected for digester studies. Upon acclimation of anaerobic inocula to pretreatments, a total number of twelve lab-scale digesters were operated under scenarios including single-stage (control), 2PAD, and HPH coupled with 2PAD (HPH + 2PAD) at sludge retention times (SRTs) of 20, 14 and 7 days. Between mesophilic and thermophilic temperatures, mesophilic digestion was found to benefit more from pretreatments. Relative (to control) improvements in methane yield and volatile solids (VS) removals increased noticeably as SRT was shortened from 20 to 14 and 7 days. HPH + 2PAD system was found to achieve the maximum methane production (0.61-1.32 L CH4/Ldigester-d) and VS removals (43-64%). Thermophilic control, 2PAD and HPH + 2PAD systems resulted in significant pathogen removals meeting Class A biosolids requirements according to Organic Matter Recycling Regulations (OMRR) of British Columbia (BC) at 20 d SRT. Energy analysis indicated that all the digestion scenarios attained positive energy balance with 2PAD system operated at 20 d SRT producing the maximum net energy of 4.76 GJ/tonne CODadded.
authors.affiliation: UBC Bioreactor Technology Group, School of Engineering, University of British Columbia, Okanagan Campus, 3333 University Way, Kelowna, BC V1V 1V7, Canada.
authors.forename: Abdullahil K
authors.initials: AK
authors.lastname: Wahidunnabi
authors.affiliation: UBC Bioreactor Technology Group, School of Engineering, University of British Columbia, Okanagan Campus, 3333 University Way, Kelowna, BC V1V 1V7, Canada. Electronic address: cigdem.eskicioglu@ubc.ca.
authors.forename: Cigdem
authors.initials: C
authors.lastname: Eskicioglu
mesh_terms: D000693:Anaerobiosis; D056804:Biofuels; D057919:Biological Oxygen Demand Analysis; D001704:Biopolymers; D019149:Bioreactors; D002849:Chromatography, Gas; D002947:Cities; D004926:Escherichia coli / Q000737:chemistry; D008697:Methane / Q000032:analysis / Q000737:chemistry; D010316:Particle Size; D011108:Polymers / Q000737:chemistry; D011312:Pressure; D012722:Sewage / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D056804:Biofuels; D001704:Biopolymers; D011108:Polymers; D012722:Sewage; D014874:Water Pollutants, Chemical; D013455:Sulfur; D008697:Methane
keywords: Biogas; High pressure homogenization; Sludge pretreatment; Sludge solubilization; Total coliform; Two-phased anaerobic digestion