title: Lab-scale demonstration of recuperative thickening technology for enhanced biogas production and dewaterability in anaerobic digestion processes.
abstract: There is growing interest in the use of high performance anaerobic digestion (AD) processes for the production of biogas at wastewater treatment facilities to offset the energy demands associated with wastewater treatment. Recuperative thickening (RT) is a promising technique which involves recycling a portion of the digested solids back to the incoming feed. In general there exists a significant number of knowledge gaps in the field of RT because the studies that have been conducted to date have almost exclusively occurred in pilot plant or full scale trials; this approach greatly limits the amount of process optimization that can be done in a given trial. In this work, a detailed and comprehensive study of RT was conducted at the lab scale; two custom designed digesters (capacity = 1.5 L) were operated in parallel with one acting as a 'control' digester and the other operating under a semi-batch RT mode. There was no significant change in biogas methane composition for the two digesters, however the RT digester had an average biogas productivity over two times higher than the control one. It was found that the recycling of the polymer flocculant back into the RT digester resulted in a significant improvement in dewatering performance. At the highest polymer concentration tested, the capillary suction time (CST) values for flocculated samples for the RT digester were over 6 times lower than the corresponding values for the control digester. Thus, there exists an opportunity to decrease the overall consumption of polymer flocculants through judicious selection of the dose of polymer flocculant that is used both for the thickening and end-stage dewatering steps in RT processes.
authors.affiliation: Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7, Canada. Electronic address: cobblejp@mcmaster.ca.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Cobbledick
authors.affiliation: Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7, Canada. Electronic address: aubryn@mcmaster.ca.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Aubry
authors.affiliation: Anaergia Inc., 4210 South Service Road, Burlington, Ontario, L7L 4X5, Canada. Electronic address: victor.zhang@anaergia.com.
authors.forename: Victor
authors.initials: V
authors.lastname: Zhang
authors.affiliation: Anaergia Inc., 4210 South Service Road, Burlington, Ontario, L7L 4X5, Canada. Electronic address: sasha.rollings-scattergood@anaergia.com.
authors.forename: Sasha
authors.initials: S
authors.lastname: Rollings-Scattergood
authors.affiliation: Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7, Canada. Electronic address: latulippe@mcmaster.ca.
authors.forename: David R
authors.initials: DR
authors.lastname: Latulippe
mesh_terms: D000693:Anaerobiosis; D056804:Biofuels; D019149:Bioreactors; D008697:Methane; D012722:Sewage; D014865:Waste Disposal, Fluid
chemical_list: D056804:Biofuels; D012722:Sewage; D008697:Methane
keywords: Anaerobic digestion (AD); Biogas production; Dewatering performance; Polymer flocculants; Recuperative thickening (RT)