Assessment of Solute Transfer Between Static and Dynamic Water During Percolation Through a Solid Leach Bed in Dry Batch Anaerobic Digestion Processes

The aim of this work was to characterize solute transfer between static and dynamic water during percolation through a solid leach bed reactor. A new experimental procedure was set up to measure the solute exchange rate between macro-and micro-porosity. Tracer tests were performed in closed-circuit recirculation experiments. The water behavior was modeled by a multiphase flow model in a double porosity medium using a previously published methodology. The solute exchange rate between static and dynamic water was described by first-order kinetics. The methodology was applied to wheat straw and solid cow manure beds. The solute exchange rate (hs was 0.054 and 0.324 h−1) for wheat straw and solid cow manure, respectively. The measured data was used to improve the prediction capacity of a CFD tool. The results of this work could be used to develop appropriate leachate recirculation strategies to optimize full-scale dry batch anaerobic digestion processes

Thermophilic anaerobic digestion of the screened solid fraction of dairy manure in a solid-phase percolating reactor system

An increase in volatile solids (VS) content from solid fraction of dairy manure would reduce the size of biogas on-farm facilities and could be of greater interest to farmers than manure slurry biogas plants. This study examined the technical feasibility of a solid-phase batch thermophilic anaerobic digestion system for the screened solid fraction (SF) of dairy manure using the digested liquid fraction of dairy manure as inoculum. Inoculum to substrate ratio (I/S) and percolate recirculation strategy were the parameters studied. The manure slurry separation process resulted in a solid fraction that represented 16.8% of total manure mass; this aforementioned fraction showed an ultimate methane yield of 61.5 L CH4 kg−1 SF (265 L CH4 kg−1 VS) which represented 48% of methane potential from raw manure slurry. Five comparative experiments with 40 kg SF and different I/S ratios and percolate recirculation rates revealed that higher I/S ratios provide more security against inhibition states due to high VFA levels and low pH in percolate. The results of the present work have shown that increasing the percolate recirculation rate in intermittent and short recirculation operations improves the stability and speed of the process. Under this percolate recirculation strategy dry batch operation was possible with a I/S ratio of 0.6 obtaining methane yields of 145, 175, 204 and 220 L CH4 kg−1 VS after 15, 20, 30 and 60 days of operation

Potenciality of Hybrid SBR process for Mesophilic digestion of biological sludge

This study is focused on evaluating two modes of anaerobic digestion, the Chemostat mode and the SBR mode, on mesophilic conditions, and tests the performance of this discontinuous mode in comparison of the conventional CSTR (Completely Stirred Tank Reactor) digestion. Thus, for this study a list of tools and methodologies were used in order to characterize the model substrate, its stability and this reaction. The first step was to characterize the hydrolysis of proteins, lipids and sugars and their transformation in VFAs (volatile fatty acids). Then, to see these intermediate reactions producing methane (reaction of acetogenesis and methanogenesis).A BMP (Biochemical Methane Potential) assays were done to analyses the biodegradability of the sludge and then compare the efficiency of methane production for both digesters. For HRT of 20 days there was observed an efficiency of 39 and 38 %, for Chemostat and SBR mode, respectively, with methanisable COD biodegradability of 57 %. To analyze the SBR mode, a monitoring of the VFAs and particle size were done. Under the operative conditions of the digester, it is interesting to see the evolution of consumption of the organic acids and define the hydrolysis reaction. Hydrolysis constant was estimated with a first exponential order with a value of 0, 07 days-1 for slow hydrolysis and 3 days-1 for fast hydrolysis. Another interesting point was the particle size distribution of the flocs. For input and output sludge, the distribution was unchanged and the settling test failed, because the substrate not settles and creates dense aggregates. Also a condition of HRT of 10 days was tested. There was no COD fell seen for both digesters, so they were operating with almost the same methane production and digesters efficiency. Kinetics of SBR mode were unchanged, even doubling the input flow rate, there was not observed an accumulation of organic acids.Outgoin

Potenciality of Hybrid SBR process for Mesophilic digestion of biological sludge

This study is focused on evaluating two modes of anaerobic digestion, the Chemostat mode and the SBR mode, on mesophilic conditions, and tests the performance of this discontinuous mode in comparison of the conventional CSTR (Completely Stirred Tank Reactor) digestion. Thus, for this study a list of tools and methodologies were used in order to characterize the model substrate, its stability and this reaction. The first step was to characterize the hydrolysis of proteins, lipids and sugars and their transformation in VFAs (volatile fatty acids). Then, to see these intermediate reactions producing methane (reaction of acetogenesis and methanogenesis).A BMP (Biochemical Methane Potential) assays were done to analyses the biodegradability of the sludge and then compare the efficiency of methane production for both digesters. For HRT of 20 days there was observed an efficiency of 39 and 38 %, for Chemostat and SBR mode, respectively, with methanisable COD biodegradability of 57 %. To analyze the SBR mode, a monitoring of the VFAs and particle size were done. Under the operative conditions of the digester, it is interesting to see the evolution of consumption of the organic acids and define the hydrolysis reaction. Hydrolysis constant was estimated with a first exponential order with a value of 0, 07 days-1 for slow hydrolysis and 3 days-1 for fast hydrolysis. Another interesting point was the particle size distribution of the flocs. For input and output sludge, the distribution was unchanged and the settling test failed, because the substrate not settles and creates dense aggregates. Also a condition of HRT of 10 days was tested. There was no COD fell seen for both digesters, so they were operating with almost the same methane production and digesters efficiency. Kinetics of SBR mode were unchanged, even doubling the input flow rate, there was not observed an accumulation of organic acids.Outgoin

Potenciality of Hybrid SBR process for Mesophilic digestion of biological sludge

This study is focused on evaluating two modes of anaerobic digestion, the Chemostat mode and the SBR mode, on mesophilic conditions, and tests the performance of this discontinuous mode in comparison of the conventional CSTR (Completely Stirred Tank Reactor) digestion. Thus, for this study a list of tools and methodologies were used in order to characterize the model substrate, its stability and this reaction. The first step was to characterize the hydrolysis of proteins, lipids and sugars and their transformation in VFAs (volatile fatty acids). Then, to see these intermediate reactions producing methane (reaction of acetogenesis and methanogenesis).A BMP (Biochemical Methane Potential) assays were done to analyses the biodegradability of the sludge and then compare the efficiency of methane production for both digesters. For HRT of 20 days there was observed an efficiency of 39 and 38 %, for Chemostat and SBR mode, respectively, with methanisable COD biodegradability of 57 %. To analyze the SBR mode, a monitoring of the VFAs and particle size were done. Under the operative conditions of the digester, it is interesting to see the evolution of consumption of the organic acids and define the hydrolysis reaction. Hydrolysis constant was estimated with a first exponential order with a value of 0, 07 days-1 for slow hydrolysis and 3 days-1 for fast hydrolysis. Another interesting point was the particle size distribution of the flocs. For input and output sludge, the distribution was unchanged and the settling test failed, because the substrate not settles and creates dense aggregates. Also a condition of HRT of 10 days was tested. There was no COD fell seen for both digesters, so they were operating with almost the same methane production and digesters efficiency. Kinetics of SBR mode were unchanged, even doubling the input flow rate, there was not observed an accumulation of organic acids.Outgoin

Biased Signaling in Mutated Variants of β₂‑Adrenergic Receptor: Insights from Molecular Dynamics Simulations

The molecular basis of receptor bias in G protein-coupled receptors (GPCRs) caused by mutations that preferentially activate specific intracellular transducers over others remains poorly understood. Two experimentally identified biased variants of β2-adrenergic receptors (β2AR), a prototypical GPCR, are a triple mutant (T68F, Y132A, and Y219A) and a single mutant (Y219A); the former bias the receptor toward the β-arrestin pathway by disfavoring G protein engagement, while the latter induces G protein signaling explicitly due to selection against GPCR kinases (GRKs) that phosphorylate the receptor as a prerequisite of β-arrestin binding. Though rigorous characterizations have revealed functional implications of these mutations, the atomistic origin of the observed transducer selectivity is not clear. In this study, we investigated the allosteric mechanism of receptor bias in β2AR using microseconds of all-atom Gaussian accelerated molecular dynamics (GaMD) simulations. Our observations reveal distinct rearrangements in transmembrane helices, intracellular loop 3, and critical residues R1313.50 and Y3267.53 in the conserved motifs D(E)RY and NPxxY for the mutant receptors, leading to their specific transducer interactions. Moreover, partial dissociation of G protein from the receptor core is observed in the simulations of the triple mutant in contrast to the single mutant and wild-type receptor. The reorganization of allosteric communications from the extracellular agonist BI-167107 to the intracellular receptor–transducer interfaces drives the conformational rearrangements responsible for receptor bias in the single and triple mutants. The molecular insights into receptor bias of β2AR presented here could improve the understanding of biased signaling in GPCRs, potentially opening new avenues for designing novel therapeutics with fewer side-effects and superior efficacy

Assessment of percolation through a solid leach bed in dry batch anaerobic digestion processes

International audienceThis work aimed at assessing water percolation through a solid cow manure leach bed in dry batch AD processes. A laboratory-scale percolation column and an experimental methodology were set up. Water behaviour was modelled by a double porosity medium approach. An experimental procedure was proposed to determine the main hydrodynamic parameters of the multiphase flow model: the porosity, the permeability and the term for water exchange from macro- to micro-porosity. Micro- and macro-porosity values ranged from 0.42 to 0.70 m3⋅m-3 and 0.18 to 0.50 m3⋅m-3. Intrinsic permeability values for solid cow manure ranged from 5.55⋅10-11 to 4.75⋅10-9 m2. The term for water exchange was computed using a 2nd order model. The CFD tool developed was used to simulate successive percolation and drainage operations. These results will be used to design leachate recirculation strategies and predict biogas production in full-scale dry AD batch processes

Quantifying physical structure changes and non-uniform water flow in cattle manure during dry anaerobic digestion process at lab scale: Implication for biogas production

International audienc