Influence of digestion temperature and organic loading rate on the continuous anaerobic treatment of process liquor from hydrothermal carbonization of sewage sludge

Benjamin Wirth, Toufiq Reza, Jan Mumme

Research output: Contribution to journalArticlepeer-review

Abstract

This experimental study investigates the use of process liquor from hydrothermal carbonization (HTC) of sewage sludge as sole substrate for anaerobic digestion (AD). The process performance at 37 C (mesophilic) and 55 C (thermophilic) was determined based on two identical continuously-fed anaerobic filters (26 L each) operated for 20 weeks. During operation, the organic loading rate was stepwise increased from 1 to 5 gCOD L-1 d-1. This decreased the hydraulic retention time from 34 to 5 days. Significant differences in methane production were not observed as both reactors yielded up to 0.18 LCH4 gCOD-1. Increased temperature had no effect on the steady-state COD removal efficiency with both reactors stabilized at 68–75%. Macro- and micronutrients were provided by HTC liquor in sufficient concentrations throughout the experiment. Methanogenesis was identified as the speed-limiting step in anaerobic digestion of HTC liquor. Hydrolysis was of an order of magnitude faster than methanogenesis.
Original languageEnglish
Pages (from-to)215-222
JournalBioresource technology
Volume198
DOIs
Publication statusPublished - 12 Sep 2015

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