Localized mixing of anaerobic plug flow reactors

Khalil, Charbel Abou; Eraky, Mohamed; Ghanimeh, Sophia

doi:10.1016/j.watres.2021.117588

Cited by 6 publications

(5 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Plug-flow reactors (PFRs) have been applied as reliable AD reactors for dry AD for some time [5]. Higher stability, high removal rates, and low acid contents make them an attractive alternative to a conventional stirred tank reactor [6]. Lately, their characteristic to form gradients along the reactor due to a laminar flow field has got into focus: It has been shown that phase separation into acidogenesis and methanogenesis inside a PFR allows higher substrate flexibility, higher resistance against a low pH value [7], and higher loading rates compared to traditional stirred tanks [8].…”

Section: Introductionmentioning

confidence: 99%

“…Lately, their characteristic to form gradients along the reactor due to a laminar flow field has got into focus: It has been shown that phase separation into acidogenesis and methanogenesis inside a PFR allows higher substrate flexibility, higher resistance against a low pH value [7], and higher loading rates compared to traditional stirred tanks [8]. The development of certain distinguished process phases inside a PFR has been explored for efficient biogas production of maize silage [8], pineapple peel and pulp [9], food waste with municipal waste water [6], and cattle manure [7], among others. Enrichment of different microbial subpopulations with hydrolytic bacteria in the front and methanogenic bacteria in the late part of a PFR has been shown by Dong et al [7].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of bioaugmentation with Paenibacillus spp. and thin slurry recirculation on microbial hydrolysis of maize silage and bedding straw in a plug-flow reactor

Menzel

Neubauer

Junne

2023

Biomass Conv. Bioref.

View full text Add to dashboard Cite

In this work, the effect of bioaugmentation on the hydrolysis and acidogenesis efficiency of bedding straw mixed with maize silage is examined. A plug-flow bioreactor was operated for 70 weeks with maize silage as a reference feedstock and subsequently with an increasing straw content of 30% and 66% (w/w). Bioaugmentation with two Paenibacillus species was conducted at each process condition to investigate the impact on hydrolysis of the recalcitrant lignocellulosic feedstock. A stable acidogenic digestion of the substrates was achieved, during which acetic and butyric acid were accumulated as main byproducts. Specific hydrolysis rates between 258 and 264 gO2 kg−1VS were determined for pure maize silage and maize silage mixed with 30% of straw, while the specific hydrolysis rate decreased to 195 gO2 kg−1VS when a mixture with 66% of straw was applied. Bioaugmentation with Paenibacillus spp. increased the specific hydrolysis rate by up to 41–63% for pure maize silage and the mixture with 30% of straw, while no increase was observed with a mixture of 66% of straw. Acid production, however, was enhanced by 21 to 42% following bioaugmentation for all substrate mixtures. A positive effect on the physiological state of cultures, as recorded with frequency-dispersed polarizability, was seen after bioaugmentation, which remained for two retention times during the continuous fermentation mode. Recirculation of the thin sludge further prolonged the positive effects of bioaugmentation. The results of this work provide a basis to optimize the amount of the bioaugmented microorganisms and hydrolysis of biogenic material with respect to sustainable effects on process performance and costs.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of bioaugmentation with Paenibacillus spp. and thin slurry recirculation on microbial hydrolysis of maize silage and bedding straw in a plug-flow reactor

Menzel

Neubauer

Junne

2023

Biomass Conv. Bioref.

View full text Add to dashboard Cite

show abstract

“…The formation of distinct process phases, in particular an acidogenic and methanogenic phase in PFRs, has been observed with various feedstock before (Sans et al 1995 ; Namsree et al 2012 ; Dong et al 2019 ; Veluchamy et al 2019 ; Khalil et al 2021 ). However, the application of a PFR as separate hydrolysis stage under the formation of a distinct hydrolytic and acidogenic phase has not been investigated thoroughly yet.…”

Section: Introductionmentioning

confidence: 94%

Spatial monitoring of hydrolysis in a plug-flow bioreactor: a support for flexible operation?

Menzel,

Neubauer,

Junne

2024

Bioresour. Bioprocess.

View full text Add to dashboard Cite

Hydrolysis at changing hydraulic retention time, recirculation, bedding straw content in the feed, bioaugmentation and the impact of those changes on gradient formation in the liquid phase in plug-flow reactors (PFRs) was examined. The pH-value, conductivity and oxidation–reduction potential (ORP) were monitored at three spots along the PFRs to study potential correlations to process performance during a total process time of 123 weeks. The on-line monitoring showed good correlations to acidogenesis: namely, the pH and ORP to the acidification, to butyric (and lactic) acid concentration and to the acid yield. The ORP (measured at the inlet) showed the most stable correlation to acidogenesis under dynamic operation, while the conductivity (at the outlet) correlated to the acid concentration in dependence on the feedstock. Multiple measurement spots as used in this study allow to gain more information about acidogenic fermentation than a single spot, simplifying process control and automation attempts with recalcitrant feedstock. Graphical Abstract

show abstract

“…The operation in a PFR, instead of the frequently applied stirred tank reactors, has several characteristic features: i) gradient formation in the reactor allows the establishment of microenvironments for specialized microbes [19,20], ii) operation at a high total solids content [21], iii) low energy input for stirring [14,22]. We hypothesize that by using a PFR with thin-sludge recirculation, e cient hydrolysis of recalcitrant feedstock is feasible without further pretreatment.…”

Section: Introductionmentioning

confidence: 99%

Plug-flow hydrolysis with lignocellulosic residues: Effect of hydraulic retention time and thin-sludge recirculation

Menzel

Neubauer

Junne

2023

Preprint

View full text Add to dashboard Cite

Two parallel plug-flow reactors were successfully applied as a hydrolysis stage for the anaerobic pre-digestion of maize silage and recalcitrant bedding straw (30 % and 66 % w/w) under variations of the hydraulic retention time (HRT) and thin-sludge recirculation. The study proved that the hydrolysis rate profits from shorter HRTs while the hydrolysis yield remained similar and was limited by a low pH-value and reached values of 264 - 310 and 180 - 200 gO2 kgVS-1 for 30 % and 66 % of bedding straw correspondingly. Longer HRT led to metabolite accumulation, significantly increased gas production, a higher acid production rate and a 10 to 18 % higher acid yield of 78 gSCCA kgVS-1 for 66 % of straw. Thin-sludge recirculation increased the acid yield and stabilized the process, especially at a short HRT. Hydrolysis efficiency can thus be improved by shorter HRT, whereas the acidogenic process performance is increased by longer HRT and thin-sludge recirculation. Two main fermentation patterns of the acidogenic community were found: above a pH-value of 3.8, butyric and acetic acid were the main products, while below a pH-value of 3.5, lactic, acetic and succinic acid were mainly accumulating. During plug-flow digestion with recirculation, at low pH-values, butyric acid remained high compared to all other acids. Both fermentation patterns had virtually equal yields of hydrolysis and acidogenesis and showed good reproducibility among the parallel reactor operation. The suitable combination of HRT and thin-sludge recirculation proved to be useful in a plug-flow hydrolysis as primary stage in biorefinery systems with the benefits of a wider feedstock spectrum including feedstock with cellulolytic components at an increased process robustness against changes in the feedstock composition.

show abstract

Localized mixing of anaerobic plug flow reactors

Cited by 6 publications

References 74 publications

Effect of bioaugmentation with Paenibacillus spp. and thin slurry recirculation on microbial hydrolysis of maize silage and bedding straw in a plug-flow reactor

Effect of bioaugmentation with Paenibacillus spp. and thin slurry recirculation on microbial hydrolysis of maize silage and bedding straw in a plug-flow reactor

Spatial monitoring of hydrolysis in a plug-flow bioreactor: a support for flexible operation?

Plug-flow hydrolysis with lignocellulosic residues: Effect of hydraulic retention time and thin-sludge recirculation

Contact Info

Product

Resources

About