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Valorisation of the liquid fraction from hydrothermal carbonisation of sewage sludge by anaerobic digestion
Author(s) -
Villamil John A,
Mohedano Angel F,
Rodriguez Juan J,
de la Rubia M Angeles
Publication year - 2018
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.5375
Subject(s) - anaerobic digestion , chemistry , mesophile , methanogenesis , sewage sludge , methane , valorisation , environmental chemistry , nuclear chemistry , sewage , waste management , biology , organic chemistry , bacteria , engineering , genetics
BACKGROUND The mesophilic anaerobic digestion of the liquid fraction from hydrothermal carbonisation (208°C, 1 h) of dehydrated sewage sludge has been studied. Two initial inoculum concentrations (IC) (10 and 25 g COD L ‐1 ) and four inoculum to substrate ratios (ISR) (2, 1, 0.5 and 0.4 on a COD basis) have been selected to analyse their influence on the evolution of the anaerobic digestion process. RESULTS The substrate is characterised by a high COD (95.5 g L ‐1 ) and TKN (8.7 g N L ‐1 ) values. High inoculum concentration (25 g COD L ‐1 ) and/or low ISR (≤ 0.5) inhibited methanogenesis due to the high ammonia nitrogen (1.4 g TAN L ‐1 ) and VFA (>4 g COD L ‐1 ) released. For the inhibited samples final COD removals lower than 15% and IA/TA ratios higher than 0.3 were found. The greatest methane yield (177±5 mL CH 4 STP g ‐1 COD added ) was achieved at 25 g COD L ‐1 of IC and at an ISR of 2. CONCLUSION During anaerobic digestion of the liquid fraction from the hydrothermal carbonisation of sewage sludge, the IC and ISR must be adequately selected for proper operation of the process and successful valorisation. According to the results, working at an ISR ≥ 1 is recommended. © 2017 Society of Chemical Industry