95/04404 Volatile fatty acids production by mesophilic fermentaiton of mechanically-sorted urban organic wastes in a plug-flow reactor

A mathematical model of a plug-flow reactor with a fluid recycle has been elaborated to simulate the VFA production process treating the organic fraction of the municipal solid waste. An alternative hydrolytic reaction model (homogeneous - heterogeneous) is proposed. The effect of a possible methanization step is also considered. The effect of process parameters (solid retention time (SRT), pH, recycle ratio) on the reactor performance is analyzed for parameters based on fruit and vegetable waste. The sensitivity of the model to proposed parameters (suspended biomass and initial biomass concentration) is also evaluated. It is found that the reactor production is very sensitive to the system pH. At low SRT, the production of volatile fatty acids (VFA) is proportional to this parameter. As the SRT increases methanization can reduce the VFA production. The effect of the recycle is negligible for the system and operating conditions studied. The effect of suspended biomass and initial biomass concentration was found to be also negligible. For the system analyzed, the pH is a critical parameter and a plug-flow arrangement (without recycle) seems to be the more reasonable election.

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Anaerobic Methane Fermentation in a Plug-Flow Reactor Treating Organic Wastes

Computer and Information Science Applications in Bioprocess Engineering ◽

10.1007/978-94-009-0177-3_21 ◽

1996 ◽

pp. 253-263

Author(s):

J. Mata-Alvarez ◽

P. Llabrés-Luengo

Keyword(s):

Flow Reactor ◽

Plug Flow ◽

Organic Wastes ◽

Plug Flow Reactor ◽

Methane Fermentation

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Volatile fatty acids build-up and its effect on E. coli inactivation during excreta stabilisation in single-stage and two-stage systems

Journal of Water Sanitation and Hygiene for Development ◽

10.2166/washdev.2018.160 ◽

2018 ◽

Vol 8 (2) ◽

pp. 257-267 ◽

Cited By ~ 2

Author(s):

Joy Riungu ◽

Mariska Ronteltap ◽

Jules B. van Lier

Keyword(s):

Fatty Acids ◽

Decay Rate ◽

Volatile Fatty Acids ◽

Flow Reactor ◽

Plug Flow ◽

Single Stage ◽

Pathogen Inactivation ◽

Two Stage ◽

E Coli ◽

Reactor Length

Abstract Digestion and co-digestion of faecal matter collected from urine diverting dehydrating toilet faeces (UDDT-F) and mixed organic market waste (OMW) was studied in single stage pilot scale mesophilic plug-flow anaerobic reactors at UDDT-F:OMW ratios 4:1 and 1:0. Escherichia coli inactivation and volatile fatty acids (VFA) build-up was monitored at sampling points located along the reactor profile. When applying UDDT-F:OMW ratio of 4:1 at 12% total solids (TS), E. coli inactivation achieved was 2.3 log times higher than that achieved in UDDT-F:OMW ratio of 1:0. In subsequent trials, a two-stage reactor was researched, applying a UDDT-F:OMW ratio of 4:1 and 10 or 12% TS slurry concentrations. Highest VFA concentrations of 16.3 ± 1.3 g/L were obtained at a pH of 4.9 in the hydrolysis/acidogenesis reactor, applying a UDDT-F:OMW ratio of 4:1 and 12% TS, corresponding to a non-dissociated (ND)-VFA concentration of 6.9 ± 2.0 g/L. The corresponding decay rate reached a value of 1.6 per day. In the subsequent methanogenic plug-flow reactor, a decay rate of 1.1 per day was attained within the first third part of the reactor length, which declined to 0.6 per day within the last third part of the reactor length. Results show that a two-stage system is an efficient way to enhance pathogen inactivation during anaerobic digestion.

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Modelling of a plug-flow pilot reactor producing VFA by anaerobic fermentation of municipal solid wastes

Water Science & Technology ◽

10.2166/wst.1994.0595 ◽

1994 ◽

Vol 30 (12) ◽

pp. 125-132 ◽

Cited By ~ 5

Author(s):

C. Sans ◽

J. Mata-Alvarez ◽

F. Cecchi ◽

P. Pavan

Keyword(s):

Mathematical Model ◽

Volatile Fatty Acids ◽

Flow Reactor ◽

Anaerobic Fermentation ◽

Plug Flow ◽

Solid Wastes ◽

Plug Flow Reactor ◽

Volatile Acid ◽

Municipal Solid Wastes ◽

Inhibition Effect

The production of volatile fatty acids (VFA) by anaerobic fermentation of municipal solid wastes was studied at pilot-plant level. A plug-flow reactor (80 1 total volume) without solid or liquid recirculation was employed to digest a mixture of two types of organic fraction of the municipal solid waste (OFMSW): OFMSW mechanically selected and OFMSW coming from a market of fruit and vegetables. The acidogenic process was studied at different retention times (between 2 and 6 days) in the mesophilic (37° ± 2°C) range of temperature. The VFA concentration obtained in the first valve of the tubular reactor ranged from 9.1 to 13.4 g 1−1 and in the outlet sludge oscillated between 11.8 and 23.1 g 1−1, increasing when increasing retention time from 2 to 6 days. A mathematical model of a continuous steady state plug-flow reactor proposed in a previous paper was used to represent the VFA production obtained experimentally. The results obtained when fitting the mathematical model with the experimental results were not sufficiently good. Some modifications of the initial model were considered. The best fitting of the results was obtained when the inhibition effect of the fermentation product on microorganisms growth was taken into account. The errors of this fitting, calculated by least squares, can be considered optimal for retention times between 4 and 6 days, while at shorter retention times the inhibition effect of pH and product makes the volatile acid production lower than the values obtained experimentally.

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Photocatalytic Degradation of Two Volatile Fatty Acids in an Annular Plug-Flow Reactor; Kinetic Modeling and Contribution of Mass Transfer Rate

Environmental Science & Technology ◽

10.1021/es062368n ◽

2007 ◽

Vol 41 (8) ◽

pp. 2908-2914 ◽

Cited By ~ 26

Author(s):

Pierre-François Biard ◽

Abdelkrim Bouzaza ◽

Dominique Wolbert

Keyword(s):

Fatty Acids ◽

Mass Transfer ◽

Photocatalytic Degradation ◽

Kinetic Modeling ◽

Transfer Rate ◽

Volatile Fatty Acids ◽

Flow Reactor ◽

Mass Transfer Rate ◽

Plug Flow ◽

Reactor Kinetic

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Effect of Biowaste Sludge Maturation on the Diversity of Thermophilic Bacteria and Archaea in an Anaerobic Reactor

Applied and Environmental Microbiology ◽

10.1128/aem.02260-08 ◽

2009 ◽

Vol 75 (8) ◽

pp. 2566-2572 ◽

Cited By ~ 79

Author(s):

M. Goberna ◽

H. Insam ◽

I. H. Franke-Whittle

Keyword(s):

Fatty Acids ◽

Volatile Fatty Acids ◽

Flow Reactor ◽

Thermophilic Bacteria ◽

Plug Flow ◽

Phylogenetic Groups ◽

Anaerobic Reactor ◽

Prokaryotic Diversity ◽

Major Shift ◽

Stable Community

ABSTRACT Prokaryotic diversity was investigated near the inlet and outlet of a plug-flow reactor. After analyzing 800 clones, 50 bacterial and 3 archaeal phylogenetic groups were defined. Clostridia (>92%) dominated among bacteria and Methanoculleus (>90%) among archaea. Significant changes in pH and volatile fatty acids did not invoke a major shift in the phylogenetic groups. We suggest that the environmental filter imposed by the saline conditions (20 g liter−1) selected a stable community of halotolerant and halophilic prokaryotes.

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Performance of an anaerobic plug-flow reactor treating agro-industrial wastes supplemented with lipids at high organic loading rate

Waste Management & Research ◽

10.1177/0734242x21991898 ◽

2021 ◽

pp. 0734242X2199189

Author(s):

Alexandros Eftaxias ◽

Dimitrios Georgiou ◽

Vasileios Diamantis ◽

Alexandros Aivasidis

Keyword(s):

Volatile Fatty Acids ◽

Loading Rate ◽

Flow Reactor ◽

Plug Flow ◽

Plug Flow Reactor ◽

Industrial Wastes ◽

High Rate ◽

Organic Loading Rate ◽

Organic Loading ◽

Used Cooking Oil

This study evaluated the performance of a plug-flow reactor (PFR) for high-rate anaerobic co-digestion of complex agro-industrial wastes and used cooking oil or animal fat. The PFR was successfully operated up to an organic loading rate (OLR) of 21 g L−1 d−1, yielding biogas at 0.35 L g−1 chemical oxygen demand (COD) influent. During the study period, supernatant COD at the PFR effluent remained between 4 and 7 g L−1, with negligible volatile fatty acids’ concentrations (<500 mg L−1) and no presence of foaming incidents. The biomass concentration inside the PFR, expressed as total suspended solids, remained between 30 and 60 g L−1. Moreover, the above-mentioned anaerobic digestion technology has been currently scaled-up at 50 m3 PFR, while a full-scale facility of 240 kW-el is under construction in the region of north-eastern Greece.

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