A side-by-side comparison of two systems of sequencing coupled reactors for anaerobic digestion of the organic fraction of municipal solid waste

Abstract

The objective of this work was to compare the performance of two laboratory-scale, mesophilic systems aiming at the anaerobic digestion of the organic fraction of municipal solid wastes (OFMSW). The first system consisted of two coupled reactors packed with OFMSW (PBR1.1-PBR1.2) and the second system consisted of an upflow anaerobic sludge bed reactor (UASB) coupled to a packed reactor (UASB2.1-PBR2.2). For the start-up phase, both reactors PBR 1.1 and the UASB 2.1 (also called leading reactors) were inoculated with a mixture of non-anaerobic inocula and worked with leachate and effluent full recirculation, respectively. Once a full methanogenic regime was achieved in the leading reactors, their effluents were fed to the fresh-packed reactors PBR1.2 and PBR2.2, respectively. The leading PBR 1.1 reached its full methanogenic regime after 118 days (Tm, time to achieve methanogenesis) whereas the other leading UASB 2.1 reactor reached its full methanogenesis regime after only 34 days. After coupling the leading reactors to the corresponding packed reactors, it was found that both coupled anaerobic systems showed similar performances regarding the degradation of the OFMSW. Removal efficiencies of volatile solids and cellulose and the methane pseudo-yield were 85.95%, 80.88% and 0.109 NL CH4 g(-1) VS(fed) in the PBR-PBR system; and 88.75%, 82.61% and 0.115 NL CH4 g(-1) VS(fed0 in the UASB-PBR system [NL, normalized litre (273 degrees K, 1 ata basis)]. Yet, the second system UASB-PBR system showed a faster overall start-up.

Effect of inhibition treatment, type of inocula, and incubation temperature on batch H2 production from organic solid waste

“…The main characteristics of the feedstock supplied to the mini-reactors are the following: total solids, 24.5 AE 1.25%; volatile solids, 14.9 AE 0.85%; pH 7.34 AE 0.15, and total Kjedahl nitrogen (% total solids) 1.93 AE 0.8. The total solids (TS) and volatile solids (VS) content of the OFMSW shows a large biodegradable solids concentration (60.8% of the TS were VS) (Poggi-Varaldo et al, 2005).…”

Anaerobic digestion of food waste: Comparing leachate exchange rates in sequential batch systems digesting food waste and biosolids

“…Acid production lowers reactor pH inhibiting the methanogenic system and limiting the generation of significant amounts of methane (Vavilin et al, 2006;Bouallagui et al, 2004;Dearman and McClure, 2002;Wang et al, 1997;Barlaz et al, 1989). The use of sequential batch systems has proven to be effective in digesting organic waste, as inhibitory products from start-up reactors can be removed and utilised in mature reactors (Chynoweth et al, 1991;Chugh et al, 1999;Poggi-Varaldo et al, 2005). In this paper, a modified mode of operation based on the Sequencing Batch Anaerobic Composting (SEBAC) method described by Chynoweth et al (1991) was chosen as the best method to digest high calorie food waste in batch reactors based on findings of other designs utilising solid organic waste (Vandevivere et al, 2002).…”

Impact of long-term partial aeration on the removal of 2,4,6-trichlorophenol in an initially methanogenic fluidized bed bioreactor

“…The a parameter is the ratio between the intermediate alkalinity (alkalinity titrated between pH 5.75 and 4.2) and partial alkalinity (titrated between original pH of the sample and 5.75); it approximately represents the ratio of volatile organic acids to bicarbonate alkalinity in anaerobic systems. Values of a lower than 0.5 correlate with robust methanogenic regimes, higher values of a are indicators of acidogenic excursions and instability in methanogenic reactors (Poggi-Varaldo et al, 2005;Ripley et al, 1986).…”

“…The evaluation variables were the removal efficiency of organic matter (h COD ), removal efficiency of TCP (h TCP ), the apparent removal efficiency of Phe (h Phe ), appearance of less substituted chlorophenols, a parameter (Poggi-Varaldo et al, 2005;Ripley et al, 1986) Garibay-Orijel et al, 2006), net increase of chloride, which reflects the Cl À released by the dechlorination of TCP (DCl…”