•Feasibility of anaerobic co-digestion of sewage sludge and wine vinasse.•Comparison of single-stage versus two-stage anaerobic co-digestion.•Single-stage mesophilic anaerobic co-digestion process ...generates more CH4.•Energy recovery in single-stage and two-stage processes is similar.•Acidogenic hydrolytic stage in two-stage process doesńt improve energy balance.
The present work consisted of the energetic valorization of sludge from wastewater treatment plants and discharges from the wine sector by means of anaerobic co-digestion. The valorization was approached through the application of two different processes: a) single-stage mesophilic anaerobic digestion process (35 °C) and, b) Temperature - Phased Anaerobic Digestion (TPAD) with separation of microorganisms: thermophilic acidogenic (55 °C) and mesophilic methanogenic (35 °C) phases.
Mesophilic methanogenic biodegradability tests (BMP) were developed to determine the biogas (methane) production yield in single-stage process and sequential thermophilic hydrogen (BHP) and BMP were developed to study the biogas (hydrogen and methane) production yield in anaerobic co-digestion processes in TPAD process.
The results obtained showed that the single-stage mesophilic anaerobic co-digestion process was more effective for methane generation with yields of 55.39 mL CH4/g VSadded for the sludge and vinasse mixture, compared to 45.79 mL CH4/g VSadded for the TPAD process.
Understanding fate of antibiotic resistant bacteria (ARB) vs. their antibiotic resistance genes (ARGs) during wastewater sludge treatment is critical in order to reduce the spread of antibiotic ...resistance through process optimization. Here, we spiked high concentrations of tetracycline-resistant bacteria, isolated from mesophilic (Iso M1-1-a Pseudomonas sp.) and thermophilic (Iso T10-a Bacillus sp.) anaerobic digested sludge, into batch digesters and monitored their fate by plate counts and quantitative polymerase chain reaction (QPCR) of their corresponding tetracycline ARGs. In batch studies, spiked ARB plate counts returned to baseline (thermophilic) or 1-log above baseline (mesophilic) while levels of the ARG present in the spiked isolate tet(G) remained high in mesophilic batch reactors. To compare results under semi-continuous flow conditions with natural influent variation, tet(O), tet(W), and sul1 ARGs, along with the intI1 integrase gene, were monitored over a 9-month period in the raw feed sludge and effluent sludge of lab-scale thermophilic and mesophilic anaerobic digesters. sul1 and intI1 in mesophilic and thermophilic digesters correlated positively (Spearman rho = 0.457-0.829, P < 0.05) with the raw feed sludge. There was no correlation in tet(O) or tet(W) ratios in raw sludge and mesophilic digested sludge or thermophilic digested sludge (Spearman rho = 0.130-0.486, P = 0.075-0.612). However, in the thermophilic digester, the tet(O) and tet(W) ratios remained consistently low over the entire monitoring period. We conclude that the influent sludge microbial composition can influence the ARG content of a digester, apparently as a result of differential survival or death of ARBs or horizontal gene transfer of genes between raw sludge ARBs and the digester microbial community. Notably, mesophilic digestion was more susceptible to ARG intrusion than thermophilic digestion, which may be attributed to a higher rate of ARB survival and/or horizontal gene transfer between raw sludge bacteria and the digester microbial community.
Selection of the most appropriate waste-to-energy technologies for distributed electricity generation is a complex and multi-criteria decision problem as it involves trade-off among conflicting ...criteria which have to be considered simultaneously. In this study, the Technique for Order of Preference by Similarity to an Ideal Solution (TOPSIS) with Entropy Weighted method is applied to select the optimal technology among the waste -to -energy technological options using the waste stream of Lagos, Nigeria. The results presented show that anaerobic digestion has been the best waste to energy technology solution for electricity generation in Lagos, followed by pyrolysis while incineration is seen as the worst preferred option of choice for energy generation applicability in standalone model. In order to maximally extract energy from waste in a sustainable, economical, and environmentally friendly manner, an integrated application of waste-to-energy technologies is also explored. It is found that the hybrid of anaerobic digestion, landfill gas recovery and pyrolysis give the most favourable results in terms of environmental benefits and electricity generation potential. It is also revealed that incineration technology either in the standalone or in the hybrid form is completely discouraged from being implemented in Lagos basically due to its high investment, operation and maintenance costs as well as its discouraging environmental image. Although, the case study in this paper is that of Lagos, Nigeria but the methodology presented could be used for any cosmopolitan city around the world.
•Selection of the most appropriate waste to energy technologies is performed.•TOPSIS technique with Entropy weighted method is applied for the selection.•Anaerobic digestion is the best WtE technology solution for electricity generation.•Incineration is the least preferred option of choice for energy generation applicability.•Hybrid of AD, landfill gas recovery and pyrolysis gave the most favourable results.
Anaerobic digestion (AD) is a matured technology for waste (water) remediation/stabilization and bioenergy generation in the form of biogas. AD technology has several inherent benefits ranging from ...generating renewable energy, remediating waste (water), and reducing greenhouse gas emission to improving health/hygiene and the overall socio-economic status of rural communities in developing nations. In recent years, there has been a paradigm shift in applications of AD technology beyond biogas. This special issue (SI) entitled, “Anaerobic Digestion Beyond Biogas (ADBB-2021),” was conceptualized to incorporate some of the recent advances in AD in which the emphasis is beyond biogas, such as anaerobic biorefinery, chain elongation, treatment of micropollutants, toxicity and system stability, digestate as biofertilizer, bio-electrochemical systems, innovative bioreactors, carbon sequestration, biogas upgrading, microbiomes, waste (water) remediation, residues/waste pre-treatment, promoter addition, and modeling, process control, and automation, among others. This VSI: ADBB-2021 contains 53 manuscripts (14 critical reviews and 39 research). The key findings of each manuscript are briefly summarized here, which can serve as a valuable resource for AD researchers to learn of major advances in AD technology and identify future research directions.
•Side-stream thermophilic anaerobic digestion (STA) improved methane production performance.•STA activated organic matter conversion, key enzymes, and KEGG pathways.•STA concentrated active genera, ...enriched syntropic oxidizing bacteria and Methanosarcina.•STA enhanced acetoclastic methanogenesis and controls adverse effects of thermal stimulation.
Anaerobic digestion (AD) is a favorable way to convert organic pollutants, such as food waste (FW), into clean energy through microbial action. This work adopted a side-stream thermophilic anaerobic digestion (STA) strategy to improve a digestive system's efficiency and stability. Results showed that the STA strategy brought higher methane production as well as higher system stability. It quickly adapted to thermal stimulation and increased the specific methane production from 359 mL CH4/g·VS to 439 mL CH4/g·VS, which was also higher than 317 mL CH4/g·VS from single-stage thermophilic anaerobic digestion. Further exploration of the mechanism of STA using metagenomic and metaproteomic analysis revealed enhanced activity of key enzymes. The main metabolic pathway was up-regulated, while the dominant bacteria were concentrated, and the multifunctional Methanosarcina was enriched. These results indicate that STA optimized organic metabolism patterns, comprehensively promoted methane production pathways, and formed various energy conservation mechanisms. Further, the system's limited heating avoided adverse effects from thermal stimulation, and activated enzyme activity and heat shock proteins through circulating slurries, which improved the metabolic process, showing great application potential.
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•A microbiota-functionality nexus is revealed by 138 samples out of 20 AD reactors.•A core bacterial microbiota prevailed across all the six types of AD reactors.•The core bacterial ...microbiota strongly correlates with the biogas productivity.•The analysis of a decomplexified OTU network shows apparent community divergence.•The AD microbiotas are neither functionally redundant or plastic.
Anaerobic digestion (AD) has been commercially operated worldwide in full scale as a resource recovery technology underpinning a circular economy. However, problems such as a long start-up time, or system instability, have been reported in response to operational shocks. These issues are usually linked to the dynamics of the functional microbiota in AD. Exploring the microbiota-functionality nexus (MFN) could be pivotal to understand the reasons behind these difficulties, and hence improving AD performance. Here we present a systematic MFN study based on 138 samples taken from 20 well-profiled lab-scale AD reactors operated for up to two years. All the reactors were operated in the same lab within the same period of time using the same methodology to harvest physio-chemical and molecular data, including key monitoring parameters, qPCR, and 16S sequencing results. The results showed a core bacterial microbiota prevailing in all reactor types, including Bacillus, Clostridium, Bacteroides, Eubacterium, Cytophaga, Anaerophaga, and Syntrophomonas, while various methanogens dominated different communities due to different inocula origins, reactor temperatures, or salinity levels. This core bacterial microbiota well correlated with biogas production (Pearson correlation coefficient of 0.481, p < 0.0001). Such strong correlation was even comparable to that between the biogas production and the methanogenic 16S rRNA gene content (Pearson correlation coefficient of 0.481, p < 0.0001). The results indicated that AD performance only modestly correlated with microbial diversity, a key governing factor. AD microbiota was neither functionally redundant nor plastic, and a high variety in communities can exhibit a strong difference in reactor performance. Our study demonstrates the importance of a core bacterial microbiota in AD and supports inspiring considerations for design, bioaugmentation, and operational strategies of AD reactors in the future.
•Temperature-phased anaerobic digestion (TPAD) of food waste were evaluated.•The biogas and methane yields of FW in TPAD were lower than those in TAD and MAD.•The TPAD had a lower FAN inhibition ...factor than MAD and TAD.•The energy conversion efficiency in TPAD was higher than that in TAD.
The temperature-phased anaerobic digestion (TPAD) of food waste was studied for the purpose of comparing with single-stage mesophilic and thermophilic anaerobic digestion. The biogas and methane yields in the TPAD during the steady period were 0.759 ± 0.115 L/g added VS and 0.454 ± 0.201 L/g added VS, which were lower than those in the two single-stage anaerobic digestion. The improper sludge retention time may be the reason for the lower biogas and methane production in TPAD. The removal of volatile solids in the TPAD was 78.55 ± 4.59% and the lowest among the three anaerobic digestion processes. The reaction ratios of the four anaerobic digestion steps in the TPAD were all lower than those in the two single-stage anaerobic digestion. The energy conversion efficiency of the degraded substrate in the TPAD was similar with those in single-stage mesophilic and thermophilic anaerobic digestion systems.
•Performances and methanogenic pathway of SADB and wet AD of organic waste were analyzed.•Liquid digestate recirculation improved AD even at TS>30%.•Methane yields were SADB=252 NLCH4/kgVS wet AD=320 ...NLCH4/kgVS.•Large syntrophic metabolism was detected in the liquid phase of SADB.
Solid anaerobic digestion batch (SADB) with liquid digestate recirculation and wet anaerobic digestion of organic waste were experimentally investigated. SADB was operated at an organic loading rate (OLR) of 4.55kgVS/m3day, generating about 252NL CH4/kgVS, whereas the wet digester was operated at an OLR of 0.9kgVS/m3day, generating about 320NL CH4/kgVS. The initial total volatile fatty acids concentrations for SADB and wet digestion were about 12,500mg/L and 4500mg/L, respectively. There were higher concentrations of ammonium and COD for the SADB compared to the wet one. The genomic analysis performed by high throughput sequencing returned a number of sequences for each sample ranging from 110,619 to 373,307. More than 93% were assigned to the Bacteria domain. Seven and nine major phyla were sequenced for the SADB and wet digestion, respectively, with Bacteroidetes, Firmicutes and Proteobacteria being the dominant phyla in both digesters. Taxonomic profiles suggested a methanogenic pathway characterized by a relevant syntrophic acetate-oxidizing metabolism mainly in the liquid digestate of the SADB. This result also confirms the benefits of liquid digestate recirculation for improving the efficiency of AD performed with high solids (>30%w/w) content.
Sustainable provision of chemicals and materials is undoubtedly a defining factor in guaranteeing economic, environmental, and social stability of future societies. Among the most sought-after ...chemical building blocks are volatile fatty acids (VFAs). VFAs such as acetic, propionic, and butyric acids have numerous industrial applications supporting from food and pharmaceuticals industries to wastewater treatment. The fact that VFAs can be produced synthetically from petrochemical derivatives and also through biological routes, for example, anaerobic digestion of organic mixed waste highlights their provision flexibility and sustainability. In this regard, this review presents a detailed overview of the applications associated with petrochemically and biologically generated VFAs, individually or in mixture, in industrial and laboratory scale, conventional and novel applications.
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