title: High-rate volatile fatty acid (VFA) production by a granular sludge process at low pH.
abstract: Volatile fatty acids (VFA) are proposed platform molecules for the production of basic chemicals and polymers from organic waste streams. In this study we developed a granular sludge process to produce VFA at high rate, yield and purity while minimizing potential operational costs. A lab-scale anaerobic sequencing batch reactor (ASBR) was fed with 10 g l(-1) glucose as model substrate. Inclusion of a short (2 min) settling phase before effluent discharge enabled effective granulation and very high volumetric conversion rates of 150-300 gCOD l(-1)  d(-1) were observed during glucose conversion. The product spectrum remained similar at the tested pH range with acetate and butyrate as the main products, and a total VFA yield of 60-70% on chemical oxygen demand (COD) basis. The requirement for base addition for pH regulation could be reduced from 1.1 to 0.6 mol OH(-) (mol glucose)(-1) by lowering the pH from 5.5 to 4.5. Solids concentrations in the effluent were 0.6 ± 0.3 g l(-1) but could be reduced to 0.02 ± 0.01 g l(-1) by introduction of an additional settling period of 5 min. The efficient production of VFA at low pH with a virtually solid-free effluent increases the economic feasibility of waste-based chemicals and polymer production. Biotechnol.
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, Delft, the Netherlands. j.tamis@tudelft.nl.
authors.forename: J
authors.initials: J
authors.lastname: Tamis
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, Delft, the Netherlands.
authors.forename: B M
authors.initials: BM
authors.lastname: Joosse
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, Delft, the Netherlands.
authors.forename: M C M van
authors.initials: MC
authors.lastname: Loosdrecht
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, Delft, the Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Kleerebezem
mesh_terms: D000693:Anaerobiosis; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D059013:Microbial Consortia; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology*
chemical_list: D005232:Fatty Acids, Volatile; D012722:Sewage; D005947:Glucose
keywords: carboxylate platform; granular sludge; open culture fermentation; resource recovery; volatile fatty acids (VFA)