ORCID Profile
0000-0002-9819-1516
Current Organisation
University of Queensland
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Environmental Technologies | Environmental Engineering | Environmental Engineering not elsewhere classified | Rheology | Wastewater Treatment Processes | Microbiology | Chemical Engineering | Microbial Ecology | Polymers and Plastics | Materials Engineering | Crop and Pasture Biomass and Bioproducts | Forestry Biomass and Bioproducts | Bioprocessing, Bioproduction and Bioproducts | Bioremediation | Industrial Microbiology (incl. Biofeedstocks) | Geochemistry not elsewhere classified
ANZSRC Socio-Economic Objective (SEO)
Urban and Industrial Water Management | Expanding Knowledge in Engineering | Management of Solid Waste from Mineral Resource Activities | Organic Industrial Chemicals (excl. Resins, Rubber and Plastics) | Environmentally Sustainable Manufacturing not elsewhere classified | Waste Management Services | Water Services and Utilities | Biofuel (Biomass) Energy | Urban and Industrial Soils | Rehabilitation of Degraded Mining Environments | Plastic Products (incl. Construction Materials) |
Related Links
Publications
Increased temperature in the thermophilic stage in temperature phased anaerobic digestion (TPAD) improves degradability of waste activated sludge
Publisher: Elsevier BV
Date: 03-2011
DOI: 10.1016/J.JHAZMAT.2011.01.032
Abstract: Two-stage temperature phased anaerobic digestion (TPAD) is an increasingly popular method to improve stabilisation of sewage waste activated sludge, which normally has inherently poor and slow degradation. However, there has been limited systematic analysis of the impact of the initial thermophilic stage (temperature, pH and retention time) on performance in the main mesophilic stage. In this study, we demonstrate a novel two-stage batch test method for TPAD processes, and use it to optimize operating conditions of the thermophilic stage in terms of degradation extent and methane production. The method determines overall degradability and apparent hydrolysis coefficient in both stages. The overall process was more effective with short pre-treatment retention times (1-2 days) and neutral pH compared to longer retention time (4 days) and low pH (4-5). Degradabilities and apparent hydrolysis coefficients were 0.3-0.5 (fraction degradable) and 0.1-0.4d(-1), respectively, with a margin of error in each measurement of approximately 20% relative (95% confidence). Pre-treatment temperature had a strong impact on the whole process, increasing overall degradability from 0.3 to 0.5 as temperature increased from 50 to 65 °C, with apparent hydrolysis coefficient increasing from 0.1 to 0.4d(-1).
Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries
Publisher: Elsevier BV
Date: 2021
Genome-centric resolution of microbial diversity, metabolism and interactions in anaerobic digestion
Publisher: Wiley
Date: 22-07-2016
Abstract: Our understanding of the complex interconnected processes performed by microbial communities is hindered by our inability to culture the vast majority of microorganisms. Metagenomics provides a way to bypass this cultivation bottleneck and recent advances in this field now allow us to recover a growing number of genomes representing previously uncultured populations from increasingly complex environments. In this study, a temporal genome-centric metagenomic analysis was performed of lab-scale anaerobic digesters that host complex microbial communities fulfilling a series of interlinked metabolic processes to enable the conversion of cellulose to methane. In total, 101 population genomes that were moderate to near-complete were recovered based primarily on differential coverage binning. These populations span 19 phyla, represent mostly novel species and expand the genomic coverage of several rare phyla. Classification into functional guilds based on their metabolic potential revealed metabolic networks with a high level of functional redundancy as well as niche specialization, and allowed us to identify potential roles such as hydrolytic specialists for several rare, uncultured populations. Genome-centric analyses of complex microbial communities across erse environments provide the key to understanding the phylogenetic and metabolic ersity of these interactive communities.
Spatial uniformity of microbial diversity in a continuous bioelectrochemical system
Publisher: Elsevier BV
Date: 02-2013
DOI: 10.1016/J.BIORTECH.2012.11.098
Abstract: Bioelectrochemical systems (BESs) are emerging as a technology with erse future applications. Anode-associated microbial ersity and activity are known to change over time, but the consequences of these dynamics on BES functioning are poorly understood. A novel BES with exchangeable anodic electrodes that facilitates characterisation of microbial communities over time was constructed. The BES, received a mixture of volatile fatty acids and produced 0.13 mA cm(-2) of anodic electrode surface, leading to the removal of 14 g chemical oxygen demand per m2 electrode per day at a coulombic efficiency of 76%. Pyrosequencing of 16S rRNA genes revealed no differences in the ersity of microbial communities associated with different electrodes within a single time point. This finding validates the design for temporal studies as changes in microbial ersity observed over time can be related to community development rather than spatial variation within the reactor.
Digestion of waste bananas to generate energy in Australia
Publisher: Elsevier BV
Date: 2008
DOI: 10.1016/J.WASMAN.2007.01.012
Abstract: This paper presents results from laboratory studies to measure the methane yield and rate of digestion of reject bananas. These parameters were determined in experiments that took into account the likely configuration of a full-scale plant in the banana growing region of north Queensland. The digestion was conducted in a 200-l reactor using fed-batch operation, relying entirely on the natural microbial consortia on the reject bananas to avoid reliance on external inocula such as sludge, an undesirable material around food packaging facilities. An enrichment culture was first established in a highly buffered 200-l batch digestion unit. The fed-batch digester was then started by exchanging leachate with the mature batch reactor. Under loading conditions of 0.6 kg VS m(-3)d(-1) over 70 days where the average working volume was 160 l, the digester produced 398+/-20 l CH4 kg VS(-1). Increasing the loading rate to 1.6 kg VS m(-3)d(-1) resulted in a reduced methane yield of 210 l CH4 kg VS(-1) over 23 days of operation, with a concomitant accumulation of banana waste in the digester. The leachate at the end of digestion contained over 4000 mg l(-1)K, 200 mg l(-1) N and 75 mg l(-1), levels that exceed acceptable limits for general agricultural irrigation.
Assessing the role of biochemical methane potential tests in determining anaerobic degradability rate and extent
Publisher: IWA Publishing
Date: 08-2011
DOI: 10.2166/WST.2011.662
Abstract: The biodegradability and bioavailability of hydrolysis-limited substrates under anaerobic (and aerobic) conditions can be represented by two key parameters – degradability (fd), or the percentage that can be effectively be destroyed during digestion, and first order hydrolysis coefficient (khyd), or the speed at which material breaks down. Biochemical methane potential (BMP) testing uses a batch test (in triplicate), and by fitting against a first order model, can fit both parameters in the same test. BMP testing is now being widely used for anaerobic process feasibility and design purposes, and standardisation efforts are ongoing. In this paper, we address a number of key issues relating to the test method and its analysis. This includes proposal of a new fitting and parameter estimation method, evaluation of the impact of inoculum to substrate ratio on fitted parameters, and comparison to performance in continuous systems. The new parameter estimation technique provides an estimate of parameter uncertainty and correlation, and is clearly more suitable than model transformation and linear regression. An inoculum volume ratio of at least 50% (2:1 on VS basis) was required on a cellulose substrate to use methane production as primary indicator, as found by comparing methane production and solubilisation of cellulose. Finally, on a typical material, waste activated sludge, the batch test was slightly conservative in terms of degradability and rate, indicating a bias in the BMP test. The test is a cost-effective and capable method to evaluate potential substrates, but it should be noted that it is generally conservative, especially if sub-optimal inoculum is used.
Anaerobic codigestion of sewage sludge and glycerol, focusing on process kinetics, microbial dynamics and sludge dewaterability
Publisher: Elsevier BV
Date: 12-2014
DOI: 10.1016/J.WATRES.2014.09.024
Abstract: Anaerobic codigestion (AcoD) is a proven option to significantly boost biogas production while utilizing existing digesters and infrastructure. The aim of the present research was to conduct an exhaustive study regarding anaerobic codigestion of mixed sewage sludge and crude glycerol considering impacts on organic load, hydraulic load, process performance and microbial community. The methane potential of crude glycerol varied from 370 mL CH4·g(-1) VS to 483 mL CH4·g(-1) VS for different s les tested. The half maximal inhibitory concentration of crude glycerol was 1.01 g VS L(-1), and the primary mechanism of inhibition was through overload from rapid fermentation rather than the presence of toxic compounds in the crude glycerol. In continuous operation over 200 days, feeding glycerol at up to 2% v/v, increased organic load by up to 70% and resulted in a 50% increase in methane production. Glycerol dosing resulted in no change in apparent dewaterability, with both codigestion and control reactors returning values of 22%-24%. Members of the phylum Thermotogae emerged as a niche population during AcoD of sewage sludge and glycerol however there was no gross change in microbial community structure and only minimal changes in ersity. AcoD did not result in synergisms between sewage sludge and crude glycerol. Actually, at dose rate up to 2% v/v glycerol dosing is still an effective strategy to increase the organic loading rate of continuous anaerobic digesters with minimal impact of the hydraulic retention time. Nonetheless, the dose rate must be managed to: (i) prevent process inhibition and (ii) ensure sufficient degradation time to produce a stable biosolids product.
Enhanced methane production from algal digestion using free nitrous acid pre-treatment
Publisher: Elsevier BV
Date: 04-2016
Comment on “Parameter Identification and Modeling of the Biochemical Methane Potential of Waste Activated Sludge”
Publisher: American Chemical Society (ACS)
Date: 02-08-2011
DOI: 10.1021/ES201803J
Temperature phased anaerobic digestion increases apparent hydrolysis rate for waste activated sludge
Publisher: Elsevier BV
Date: 02-2011
DOI: 10.1016/J.WATRES.2010.11.042
Abstract: It is well established that waste activated sludge with an extended sludge age is inherently slow to degrade with a low extent of degradation. Pre-treatment methods can be used prior to anaerobic digestion to improve the efficiency of activated sludge digestion. Among these pre-treatment methods, temperature phased anaerobic digestion (TPAD) is one promising method with a relatively low energy input and capital cost. In this study, an experimental thermophilic (50-70 °C)-mesophilic system was compared against a control mesophilic-mesophilic system. The thermophilic-mesophilic system achieved 41% and 48% volatile solids (VS) destruction during pre-treatment of 60 °C and 65 °C (or 70 °C) respectively, compared to 37% in the mesophilic-mesophilic TPAD system. Solubilisation in the first stage was enhanced during thermophilic pre-treatment (15% at 50 °C and 27% at 60 °C, 65 °C and 70 °C) over mesophilic pre-treatment (7%) according to a COD balance. This was supported by ammonia-nitrogen measurements. Model based analysis indicated that the mechanism for increased performance was due to an increase in hydrolysis coefficient under thermophilic pre-treatment of 60 °C (0.5 ± 0.1 d(-1)), 65 °C (0.7 ± 0.2 d(-1)) and 70 °C (0.8 ± 0.2 d(-1)) over mesophilic pre-treatment (0.2 ± 0.1 d(-1)), and thermophilic pre-treatment at 50 °C (0.12 ± 0.06 d(-1)).
Relationship between microbial community, operational factors and ammonia inhibition resilience in anaerobic digesters at low and moderate ammonia background concentrations
Publisher: Elsevier BV
Date: 09-2018
DOI: 10.1016/J.NBT.2018.02.013
Abstract: The relationship between anaerobic digestion operational conditions and (i) microbial community, (ii) acetoclastic methanogenic activity and (iii) free ammonia (NH
Does manure management affect the latent greenhouse gas emitting potential of livestock manures?
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.WASMAN.2015.08.019
Abstract: With livestock manures being increasingly sought as alternatives to costly synthetic fertilisers, it is imperative that we understand and manage their associated greenhouse gas (GHG) emissions. Here we provide the first dedicated assessment into how the GHG emitting potential of various manures responds to the different stages of the manure management continuum (e.g., from feed pen surface vs stockpiled). The research is important from the perspective of manure application to agricultural soils. Manures studied included: manure from beef feedpen surfaces and stockpiles poultry broiler litter (8-week batch) fresh and composted egg layer litter and fresh and composted piggery litter. Gases assessed were methane (CH4) and nitrous oxide (N2O), the two principal agricultural GHGs. We employed proven protocols to determine the manures' ultimate CH4 producing potential. We also devised a novel incubation experiment to elucidate their N2O emitting potential a measure for which no established methods exist. We found lower CH4 potentials in manures from later stages in their management sequence compared with earlier stages, but only by a factor of 0.65×. Moreover, for the beef manures this decrease was not significant (P<0.05). Nitrous oxide emission potential was significantly positively (P<0.05) correlated with C/N ratios yet showed no obvious relationship with manure management stage. Indeed, N2O emissions from the composted egg manure were considerably (13×) and significantly (P<0.05) higher than that of the fresh egg manure. Our study demonstrates that manures from all stages of the manure management continuum potentially entail significant GHG risk when applied to arable landscapes. Efforts to harness manure resources need to account for this.
Characterising and modelling free ammonia and ammonium inhibition in anaerobic systems
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.WATRES.2018.06.021
Abstract: Inhibition by ammoniacal nitrogen, consisting of free ammonia (NH
High-rate, High Temperature Acetotrophic Methanogenesis Governed by a Three Population Consortium in Anaerobic Bioreactors
Publisher: Public Library of Science (PLoS)
Date: 04-08-2016
Anaerobic Processes
Publisher: Elsevier
Date: 2011
Semi-aerobic fermentation as a novel pre-treatment to obtain VFA and increase methane yield from primary sludge
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.BIORTECH.2015.10.085
Abstract: There is a growing trend to consider organic wastes as potential sources of renewable energy and value-add products. Fermentation products have emerged as attractive value-add option due to relative easy production and broad application range. However, pre-fermentation and extraction of soluble products may impact down-stream treatment processes, particularly energy recovery by anaerobic digestion. This paper investigates primary sludge pre-fermentation at different temperatures (20, 37, 55, and 70°C), treatment times (12, 24, 48, and 72h), and oxygen availability (semi-aerobic, anaerobic) and its impact on anaerobic digestion. Pre-fermentation at 20 and 37°C succeeded for VFA production with acetate and propionate being major products. Pre-fermentation at 37, 55, and 70°C resulted in higher solubilisation yield but it reduced sludge methane potential by 20%. Under semi-aerobic conditions, pre-fermentation allowed both VFA recovery (43gCODVFAkg(-1)VS) and improved methane potential. The latter phenomenon was linked to fungi that colonised the sludge top layer during pre-fermentation.
Biogas production coupled to repeat microalgae cultivation using a closed nutrient loop
Publisher: Elsevier BV
Date: 09-2018
DOI: 10.1016/J.BIORTECH.2018.05.039
Abstract: Anaerobic digestion is an established technology to produce renewable energy as methane-rich biogas for which microalgae are a suitable substrate. Besides biogas production, anaerobic digestion of microalgae generates an effluent rich in nutrients, so-called digestate, that can be used as a growth medium for microalgal cultures, with the potential for a closed nutrient loop and sustainable bioenergy facility. In this study, the methane potential and nutrient mobilization of the microalga Scenedemus dimorphus was evaluated under continuous conditions. The suitability of using the digestate as culture medium was also evaluated. The results show that S. dimorphus is a suitable substrate for anaerobic digestion with an average methane yield of 199 mL g
Effects of Temperature and Hydraulic Retention Time on Acetotrophic Pathways and Performance in High-Rate Sludge Digestion
Publisher: American Chemical Society (ACS)
Date: 22-05-2014
DOI: 10.1021/ES500074J
Abstract: High-rate anaerobic digestion of organic solids requires rapid hydrolysis and enhanced methanogenic growth rates, which can be achieved through elevated temperature (>55 °C) at short hydraulic retention times (HRT). This study assesses the effect of temperatures between 55 °C and 65 °C and HRTs between 2 and 4 days on process performance, microbial community structure, microbial capability, and acetotrophic pathways in thermophilic anaerobic reactors. Increasing the temperature did not enhance volatile solids (VS) destruction above the base value of 37% achieved at 55 °C and 4 days HRT. Stable isotopic signatures (δ13C) revealed that elevated temperature promoted syntrophic acetate oxidation, which accounted for 60% of the methane formation at 55 °C, and increasing substantially to 100% at 65 °C. The acetate consumption capacity dropped with increasing temperature (from 0.69-0.81 gCOD gVS(-1) d(-1) at 55 °C to 0.21-0.35 gCOD gVS(-1) d(-1) at 65 °C), based on specific activity testing of reactor contents. Community analysis using 16S rRNA pyrosequencing revealed the dominance of Methanosarcina at 55-60 °C. However, a further increase to 65 °C resulted in loss of Methanosarcina, with an accumulation of organic acids and reduced methane production. Similar issues were observed when reducing the HRT to 2 days, indicating that temperature 3 days are critical to operate these systems stably.
Relative kinetics of anaerobic digestion under thermophilic and mesophilic conditions
Publisher: IWA Publishing
Date: 08-2011
DOI: 10.2166/WST.2011.571
Abstract: With several advantages over the conventional mesophilic anaerobic digestion, such as better sludge quality and higher biogas production, thermophilic anaerobic digestion is regarded as a promising alternative for sludge digestion. Primary and activated sludges are complex materials, and historically, analysis of kinetics has been largely on whole sludge, without analysis of in idual components. This paper analyses relative digestion kinetics of pure substrates designed to target main stages of sludge digestion under thermophilic and mesophilic conditions. Hydrolysis rate of cellulose was significantly influenced by temperature with hydrolysis coefficients of – at 55 °C (0.7 ± 0.1 day−1), 60 °C (0.8 ± 0.2 day−1), 65 °C (1.1 ± 0.2 day−1) and 70 °C (1.2 ± 0.2 day−1) over 38 °C (0.4 ± 0.1 day−1). This strongly follows the Arrhenius relationship, with an activation energy (EA) of 31 ± 4 kJ mol−1, corresponding to an increase of 1.5x for each 10 °C of temperature increase. Glucose uptake was rapid with a wide variety of fermentation products detected under mesophilic conditions, while uptake was slower under thermophilic conditions with acetate and propionate being dominant products. Propionate acetogenesis and acetate-utilizing methanogenesis kinetics were not influenced by temperatures. Hydrolysis is widely regarded as a rate-limiting step in sludge digestion, thus improvements in hydrolysis rates as measured during this study have the potential for significant improvements in overall apparent sludge digestion rates.
Indigenous microbial capability in solid manure residues to start-up solid-phase anaerobic digesters
Publisher: Elsevier BV
Date: 06-2017
DOI: 10.1016/J.WASMAN.2017.02.031
Abstract: Batch solid-phase anaerobic digestion is a technology for sustainable on-farm treatment of solid residues, but is an emerging technology that is yet to be optimised with respect to start-up and inoculation. In the present study, spent bedding from two piggeries (site A and B) were batch digested at total solids (TS) concentration of 5, 10 and 20% at mesophilic (37°C) and thermophilic (55°C) temperatures, without adding an external inoculum. The results showed that the indigenous microbial community present in spent bedding was able to recover the full methane potential of the bedding (140±5 and 227±6L CH
Modelling anaerobic co-digestion in Benchmark Simulation Model No. 2: Parameter estimation, substrate characterisation and plant-wide integration
Publisher: Elsevier BV
Date: 07-2016
Development and validation of a rapid test for anaerobic inhibition and toxicity
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.WATRES.2015.05.063
Abstract: Despite the importance of quantifying inhibitory capacity of compounds in anaerobic digestion, there is currently no well-defined method to assess it. Experimental methods in literature are frequently time-consuming and resource intensive. As a result, detailed inhibition testing rarely forms part of anaerobic digestion studies, despite the importance and utility of this information. This study develops and validates a simple and rapid inhibition test protocol, based on relative inhibition of acetoclastic methanogens. The inhibition potential of a compound is determined from the reduction in specific methanogenic activity as inhibitor concentration is increased. The method was successfully performed on two inoculums from different source environments and with both biostatic and biocidal inhibitors. Optimisation work indicated that: (i) sodium acetate is a preferred carbon source compared to acetic acid (ii) an inoculum to acetate ratio of 5 g VS g(-1) acetate is preferred, and (iii) that the inoculum concentration should be normalised to 10 g L(-1) VS to reduce mass transfer problems and promote consistency. A key advantage over existing methods is that the s ling strategy has been optimised to three events over 1.5 days while effectively controlling the relative analytical error.
Deterministic mechanisms define the long-term anaerobic digestion microbiome and its functionality regardless of the initial microbial community
Publisher: Elsevier BV
Date: 09-2018
DOI: 10.1016/J.WATRES.2018.05.028
Abstract: The impact of the starting inoculum on long-term anaerobic digestion performance, process functionality and microbial community composition remains unclear. To understand the impact of starting inoculum, active microbial communities from four different full-scale anaerobic digesters were each used to inoculate four continuous lab-scale anaerobic digesters, which were operated identically for 295 days. Digesters were operated at 15 days solid retention time, an organic loading rate of 1 g COD L
Effect of biomass concentration and inoculum source on the rate of anaerobic cellulose solubilization
Publisher: Elsevier BV
Date: 11-2009
DOI: 10.1016/J.BIORTECH.2009.05.018
Abstract: This study determines cellulose solubilization kinetics from controlled batch digestions and shows the effect of inoculum biomass concentrations. Separate measurements and analyzes were performed for sessile biomass (biofilms) and planktonic biomass (free suspensions). Experiments were conducted using either leachate enriched on cellulose or rumen fluid as inoculum to assess if the effect of biomass concentration was consistent for microbial populations from different source environments. All batch digestions were fitted to a first-order kinetic model (R(2) ranging from 0.94 to 0.99). Regression analysis used to compare the first-order hydrolysis rate showed that the first-order hydrolysis rate was most strongly correlated with the concentration of sessile biomass rather than with the concentration of total or planktonic biomass. The correlation between solubilization rate and sessile biomass was statistically the same for the rumen and leachate inoculated reactors indicating that at low concentration ratios of inoculum to cellulose, the rate of cellulose solubilization is dependant primarily on sessile biomass concentration rather than the species profile of the cellulolytic community.
Effect of initial biomass on cellulose hydrolysis by leachate communities
Publisher: Inderscience Publishers
Date: 2009
Methanosarcinaceae and Acetate-Oxidizing Pathways Dominate in High-Rate Thermophilic Anaerobic Digestion of Waste-Activated Sludge
Publisher: American Society for Microbiology
Date: 15-10-2013
DOI: 10.1128/AEM.01730-13
Abstract: This study investigated the process of high-rate, high-temperature methanogenesis to enable very-high-volume loading during anaerobic digestion of waste-activated sludge. Reducing the hydraulic retention time (HRT) from 15 to 20 days in mesophilic digestion down to 3 days was achievable at a thermophilic temperature (55°C) with stable digester performance and methanogenic activity. A volatile solids (VS) destruction efficiency of 33 to 35% was achieved on waste-activated sludge, comparable to that obtained via mesophilic processes with low organic acid levels ( mg/liter chemical oxygen demand [COD]). Methane yield (VS basis) was 150 to 180 liters of CH 4 /kg of VS added . According to 16S rRNA pyrotag sequencing and fluorescence in situ hybridization (FISH), the methanogenic community was dominated by members of the Methanosarcinaceae , which have a high level of metabolic capability, including acetoclastic and hydrogenotrophic methanogenesis. Loss of function at an HRT of 2 days was accompanied by a loss of the methanogens, according to pyrotag sequencing. The two acetate conversion pathways, namely, acetoclastic methanogenesis and syntrophic acetate oxidation, were quantified by stable carbon isotope ratio mass spectrometry. The results showed that the majority of methane was generated by nonacetoclastic pathways, both in the reactors and in off-line batch tests, confirming that syntrophic acetate oxidation is a key pathway at elevated temperatures. The proportion of methane due to acetate cleavage increased later in the batch, and it is likely that stable oxidation in the continuous reactor was maintained by application of the consistently low retention time.
Free Nitrous Acid (FNA)-Based Pretreatment Enhances Methane Production from Waste Activated Sludge
Publisher: American Chemical Society (ACS)
Date: 27-09-2013
DOI: 10.1021/ES402933B
Abstract: Anaerobic digestion of waste activated sludge (WAS) is currently enjoying renewed interest due to the potential for methane production. However, methane production is often limited by the slow hydrolysis rate and/or poor methane potential of WAS. This study presents a novel pretreatment strategy based on free nitrous acid (FNA or HNO2) to enhance methane production from WAS. Pretreatment of WAS for 24 h at FNA concentrations up to 2.13 mg N/L substantially enhanced WAS solubilization, with the highest solubilization (0.16 mg chemical oxygen demand (COD)/mg volatile solids (VS), at 2.13 mg HNO2-N/L) being six times that without FNA pretreatment (0.025 mg COD/mg VS, at 0 mg HNO2-N/L). Biochemical methane potential tests demonstrated methane production increased with increased FNA concentration used in the pretreatment step. Model-based analysis indicated FNA pretreatment improved both hydrolysis rate and methane potential, with the highest improvement being approximately 50% (from 0.16 to 0.25 d(-1)) and 27% (from 201 to 255 L CH4/kg VS added), respectively, achieved at 1.78-2.13 mg HNO2-N/L. Further analysis indicated that increased hydrolysis rate and methane potential were related to an increase in rapidly biodegradable substrates, which increased with increased FNA dose, while the slowly biodegradable substrates remained relatively static.
Humic acid inhibition of hydrolysis and methanogenesis with different anaerobic inocula
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.WASMAN.2018.09.001
Abstract: There is increasing evidence that humic acid (HA) is h ering the performance of anaerobic digesters treating animal manures and thermally-hydrolysed waste activated sludge. In the present study, HA inhibition and inhibition resilience was examined for hydrolysis (carbohydrate and protein) and acetotrophic methanogenesis with four distinct full-scale anaerobic inocula. The aim was to further understand HA inhibition and to explore potential relationships between microbial factors and inhibition resilience. For two of the four tested inocula, cellulose degradation showed a start-up delay that lengthened as HA concentration increased from 0 to 2 g L
Anaerobic membrane bioreactors enable high rate treatment of slaughterhouse wastewater
Publisher: Elsevier BV
Date: 05-2015
Temperature and solids retention time control microbial population dynamics and volatile fatty acid production in replicated anaerobic digesters
Publisher: Springer Science and Business Media LLC
Date: 16-02-2015
DOI: 10.1038/SREP08496
Abstract: Anaerobic digestion is a widely used technology for waste stabilization and generation of biogas and has recently emerged as a potentially important process for the production of high value volatile fatty acids (VFAs) and alcohols. Here, three reactors were seeded with inoculum from a stably performing methanogenic digester and selective operating conditions (37°C and 55°C 12 day and 4 day solids retention time) were applied to restrict methanogenesis while maintaining hydrolysis and fermentation. Replicated experiments performed at each set of operating conditions led to reproducible VFA production profiles which could be correlated with specific changes in microbial community composition. The mesophilic reactor at short solids retention time showed accumulation of propionate and acetate (42 ± 2% and 15 ± 6% of COD hydrolyzed , respectively) and dominance of Fibrobacter and Bacteroidales . Acetate accumulation ( % of COD hydrolyzed ) was also observed in the thermophilic reactors, which were dominated by Clostridium . Under all tested conditions, there was a shift from acetoclastic to hydrogenotrophic methanogenesis and a reduction in methane production by % of COD hydrolyzed . Our results demonstrate that shortening the SRT and increasing the temperature are effective strategies for driving microbial communities towards controlled production of high levels of specific volatile fatty acids.
Pre-treatment mechanisms during thermophilic–mesophilic temperature phased anaerobic digestion of primary sludge
Publisher: Elsevier BV
Date: 2010
DOI: 10.1016/J.WATRES.2009.09.005
Abstract: Pre-treatment is used extensively to improve degradability and hydrolysis rate of material being fed into digesters. One emerging process is temperature phased anaerobic digestion (TPAD), which applies a short (2 day) 50-70 degrees C pre-treatment step prior to 35 degrees C digestion in the main stage (10-20 days). In this study, we evaluated a thermophilic-mesophilic TPAD against a mesophilic-mesophilic TPAD treating primary sludge. Thermophilic-mesophilic TPAD achieved 54% VS destruction compared to 44% in mesophilic-mesophilic TPAD, with a 25% parallel increase in methane production. Measurements of soluble COD and NH(4)(+)-N showed increased hydrolysis extent during thermophilic pre-treatment. Model based analysis indicated the improved performance was due to an increased hydrolysis coefficient rather than an increased inherent degradability, suggesting while TPAD is suitable as an intensification process, a larger main digester could achieve similar impact.
Pilot-scale testing of a leachbed for anaerobic digestion of livestock residues on-farm
Publisher: Elsevier BV
Date: 04-2016
DOI: 10.1016/J.WASMAN.2016.02.031
Abstract: A leachbed is a relatively simple anaerobic digester suitable for high-solids residues and on-farm applications. However, performance characteristics and optimal configuration of leachbeds are not well-understood. In this study, two 200 L pilot-scale leachbeds fed with spent straw bedding from pigs/swine (methane potential, B0 = 195-218 L CH4 kg(-1) VS fed) were used to assess the effects of leachate recirculation mode (trickling vs. flood-and-drain) on the digestion performance. Results showed comparable substrate solubilisation extents (30-45% of total chemical oxygen demand fed) and methane conversion (50% of the B0) for the trickling and flood-and-drain modes, indicating that digestion performance was insensitive to the mode of leachate flow. However, the flood-and-drain leachbed mobilised more particulates into the leachate than the trickling leachbed, an undesirable outcome, because these particulates were mostly non-biodegradable. Inoculation with solid residues from a previous leachbed (inoculum-to-substrate ratio of 0.22 on a VS basis) hastened the leachbed start-up, but methane recovery remained at 50% of the B0 regardless of the leachate recirculation mode. Post-digestion testing indicated that the leachbeds may have been limited by microbial activity/inhibition. The high residual methane potential of leachate from the trickling (residual Bo = 732 ± 7 L CH4 kg(-1) VS fed) and flood-and-drain leachbeds (582 ± 8 L CH4 kg(-1) VS fed) indicated an opportunity for further processing of leachate via a separate methanogenic step. Overall, a trickling leachbed appeared to be more favourable than the flood-and-drain leachbed for treating spent bedding at farm-scale due to easier operation.
Linking microbial community structure, interactions and function in anaerobic digesters using new molecular techniques
Publisher: Elsevier BV
Date: 06-2014
DOI: 10.1016/J.COPBIO.2013.11.004
Abstract: Over the last decade there has been a rapid development in culture-independent techniques for exploring microbial communities, which have led to new insights into their structure and function in both natural environments and engineered systems. This review focuses on some of the most important recent advances and their applications to the erse microbial communities associated with anaerobic digestion. The use of these approaches in combination with complementary imaging techniques, chemical isotope analyses and detailed reactor performance measurements provides a new opportunity to develop a fundamental understanding of how microbial community dynamics, interactions and functionality influence digester efficiency and stability.
Integrated biodiesel and biogas production from microalgae: Towards a sustainable closed loop through nutrient recycling
Publisher: Elsevier BV
Date: 02-2018
Measurement and quantification of sessile and planktonic microbial populations during the anaerobic digestion of cellulose
Publisher: IWA Publishing
Date: 03-2008
DOI: 10.2166/WST.2008.106
Abstract: Crystalline cellulose was anaerobically degraded using a leachate inoculum derived from simulated municipal solid waste. Bicinchoninic Acid (BCA) protein assays were used to measure the distribution of biomass during cellulose degradation, including the planktonic and sessile biomass fractions. A comparison of sessile and planktonic microbial growth indicated that the microbial growth was dominated by the planktonic fraction with the biofilms accounting for approximately 25% of the population. Additional biomass measurements were conducted to test the reliability of the BCA protein assays. Total microbial growth was inferred from the accumulation and depletion of ammonia nitrogen measured using flow injection analysis. The planktonic biomass was estimated from direct cell counts using light microscopy and the sessile biomass was estimated by analysing the nitrogen content of the separated and washed cellulose pellet. Regression analysis showed good correlations between the measurement pairs representing the total biomass (R2=0.90), planktonic biomass (R2=0.97) and sessile biomass (R2=0.85), supporting the use of protein assays as an indicator of microbial growth in mixed culture environments.
Dynamic multidimensional modelling of submerged membrane bioreactor fouling
Publisher: Elsevier BV
Date: 10-2014
Deterministic processes guide long-term synchronised population dynamics in replicate anaerobic digesters
Publisher: Springer Science and Business Media LLC
Date: 17-04-2014
Analysis of the potential to recover energy and nutrient resources from cattle slaughterhouses in Australia by employing anaerobic digestion
Publisher: Elsevier BV
Date: 12-2014
Impact of dewatering technologies on specific methanogenic activity
Publisher: Elsevier BV
Date: 10-2015
DOI: 10.1016/J.WATRES.2015.04.005
Abstract: Dewatering methods for recuperative thickening and final dewatering can potentially impact methanogenic activity and microbial community. This influences both the feasibility of recuperative thickening to increase solids residence time within a digester, and the utilisation of dewatered digestate as inoculum for new digesters. Thickening technology can reduce methanogenic activity through either air contact (rotary drum, DAF, or belt filter press), or by lysing cells through shear (centrifuge). To assess this, two plants with recuperative thickening (rotary drum) in their anaerobic digester, and five without recuperative thickening, had specific methanogenic activity tested in all related streams, including dewatering feed, thickened return, final cake, and centrate. All plants had high speed centrifuges for final dewatering. The digester microbial community was also assessed through 16s pyrotag sequencing and subsequent principal component analysis (PCA). The specific methanogenic activity of all s les was in the expected range of 0.2-0.4 gCOD gVS(-1)d(-1). Plants with recuperative thickening did not have lower digester activity. Centrifuge based dewatering had a significant and variable impact on methanogenic activity in all s les, ranging between 20% and 90% decrease but averaging 54%. Rotary drum based recuperative thickening had a far smaller impact on activity, with a 0% per-pass drop in activity in one plant, and a 20% drop in another. However, the presence of recuperative thickening was a major predictor of overall microbial community (PC1, p = 0.0024). Microbial community PC3 (mainly driven by a shift in methanogens) was a strong predictor for sensitivity in activity to shear (p = 0.0005, p = 0.00001 without outlier). The one outlier was related to a plant producing the wettest cake (17% solids). This indicates that high solids is a potential driver of sensitivity to shear, but that a resilient microbial community can also bestow resilience. Sensitivity of methanogens to centrifuging does not rule out centrifuges for recuperative thickening (particularly where hydrolysis is rate-limiting), but may impose a maximum return rate to avoid digester failure.
Methylotrophic methanogenesis discovered in the archaeal phylum Verstraetearchaeota
Publisher: Springer Science and Business Media LLC
Date: 18-06-2018
DOI: 10.1038/NMICROBIOL.2016.170
Abstract: Methanogenesis is the primary biogenic source of methane in the atmosphere and a key contributor to climate change. The long-standing dogma that methanogenesis originated within the Euryarchaeota was recently challenged by the discovery of putative methane-metabolizing genes in members of the Bathyarchaeota, suggesting that methanogenesis may be more phylogenetically widespread than currently appreciated. Here, we present the discovery of ergent methyl-coenzyme M reductase genes in population genomes recovered from anoxic environments with high methane flux that belong to a new archaeal phylum, the Verstraetearchaeota. These archaea encode the genes required for methylotrophic methanogenesis, and may conserve energy using a mechanism similar to that proposed for the obligate H 2 -dependent methylotrophic Methanomassiliicoccales and recently described Candidatus ‘Methanofastidiosa’. Our findings indicate that we are only beginning to understand methanogen ersity and support an ancient origin for methane metabolism in the Archaea, which is changing our understanding of the global carbon cycle.
Anaerobic digestion of swine effluent: Impact of production stages
Publisher: Elsevier BV
Date: 2013
Recovery of energy and nutrient resources from cattle paunch waste using temperature phased anaerobic digestion
Publisher: Elsevier BV
Date: 05-2016
DOI: 10.1016/J.WASMAN.2016.02.039
Abstract: Cattle paunch is comprised of partially digested cattle feed, containing mainly grass and grain and is a major waste produced at cattle slaughterhouses contributing 20-30% of organic matter and 40-50% of P waste produced on-site. In this work, Temperature Phased Anaerobic Digestion (TPAD) and struvite crystallization processes were developed at pilot-scale to recover methane energy and nutrients from paunch solid waste. The TPAD plant achieved a maximum sustainable organic loading rate of 1-1.5kgCODm(-3)day(-1) using a feed solids concentration of approximately 3% this loading rate was limited by plant engineering and not the biology of the process. Organic solids destruction (60%) and methane production (230LCH4kg(-1) VSfed) achieved in the plant were similar to levels predicted from laboratory biochemical methane potential (BMP) testing. Model based analysis identified no significant difference in batch laboratory parameters vs pilot-scale continuous parameters, and no change in speed or extent of degradation. However the TPAD process did result in a degree of process intensification with a high level of solids destruction at an average treatment time of 21days. Results from the pilot plant show that an integrated process enabled resource recovery at 7.8GJ/dry tonne paunch, 1.8kgP/dry tonne paunch and 1.0kgN/dry tonne paunch.
Biochemical Methane Potential of Beef Feedlot Manure: Impact of Manure Age and Storage
Publisher: Wiley
Date: 07-2013
DOI: 10.2134/JEQ2012.0457
Abstract: Methane capture and use from intensive livestock industries is relatively new, and there is limited chemical and kinetic degradation information available for beef feedlot manure in Australia or internationally. This paper evaluates the biochemical methane (CH) potential, apparent first-order hydrolysis rate coefficient, and losses in organic content of manure as it ages on feedlot pads and in stockpiles. Chemical characterization of fresh, pad, and stockpiled manure is assessed. Biochemical CH potential on volatile solids (VS) almost always decreased significantly from fresh to pad and from pad to stockpile, ranging (in mL CH g VS) from 230 to 360 in fresh manure, from 70 to 280 in pads, and from 60 to 200 in stockpiles. Kinetics of degradation also varied with manure age (fresh: 0.12 ± 0.01 d pad: 0.06 ± 0.02 d and stockpiled: 0.05 ± 0.04 d). At least 50%, and up to 80%, of the original biochemical CH potential of the manure (i.e., degradable material) was lost on drying in pads, and the loss after stockpiling was much greater (>85%). The loss of N was 15 to 60% as manure dried on pads and was much greater after stockpiling (40-90%). Phosphorus loss, though lower than nitrogenous losses, was still significant (25-65% on pads and 35-85% in stockpiles). Although digestion of stockpiled manure is still feasible to generate energy, collection of fresh manure is important to maximize outcomes, with a possible order of magnitude increase in CH production achievable.
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