Increase In Organic Loading Rate Research Articles

An integrated evaluation strategy for anaerobic digestion monitoring based on acid-base balance and thermodynamics of volatile fatty acid degradation

Process monitoring is a top priority for anaerobic digestion (AD), yet it poses a significant challenge due to its inherent inaccuracies and case-specific nature in diagnosing reactor status. Herein, a long-term instability simulation experiment using lignocellulosic biomass was conducted with varying organic loading rate (OLR) and hydraulic retention time (HRT) levels. The increase in OLR (0.75 to 20 kg VS m−3·d−1) and decrease in HRT (20 to 4 d) led to substantial total volatile fatty acids (TVFA) accumulation (>14 g/L) with a concomitant decrease in methane yield and organics removal. Full processing capacity with considerable conversion efficiency at four steps (hydrolysis: 60.43 ± 2.82 %, acidogenesis: 56.13 ± 3.27 %, acetogenesis: 56.03 ± 3.31 %, methanogenesis: 55.93 ± 3.32 %) and optimal methane yield (3.13 ± 0.17 L/(L·d)) was achieved at an OLR of 18 Kg VS·m−3·d−1 and HRT of 4 days. An integrated evaluation strategy for AD process stability is proposed based on the acid-base balance and thermodynamics of VFA degradation. Propionate, iso-valerate, TVFA/bicarbonate alkalinity (BA), and BA/total alkalinity (TA) were identified as potential auxiliary indicators for diagnosing AD imbalances, while ΔG for propionate and valerate degradation served as the early warning signs. To enhance the efficacy and universality of early warnings, relative variations for acid-base indicators based on steady-state (∼15 %) and the absolute threshold value for ΔGPropionate (-40 KJ/mol) and ΔGValerate (-55 KJ/mol) were adopted. This approach integrates considerations for microbial adaption, thereby enhancing an assessment of whether a given signal reflects irreversible acidification or is merely a temporary fluctuation induced by reversible acidification. The proposed strategy enables a reliable and accurate early warning, holding great promise for practical applications.

Anaerobic digestion of sewage sludge using anaerobic dynamic membrane bioreactor under various sludge composition and organic loading rates

This study investigates the effects of sludge compositions and organic loading rates (OLRs) on stable biogas production during sludge digestion. Batch digestion experiments evaluate the effects of alkaline-thermal pretreatment and waste activated sludge (WAS) fractions on the biochemical methane potential (BMP) of sludge. A lab-scale anaerobic dynamic membrane bioreactor (AnDMBR) is fed with a mixture of primary sludge and pretreated WAS. Monitoring of volatile fatty acid to total alkalinity (FOS/TAC) helps maintain operational stability. The highest average methane production rate of 0.7 L/L·d is achieved when the OLR, hydraulic retention time, WAS volume fraction, and FOS/TAC ratio are 5.0 g COD/L·d, 12 days, 0.75, and 0.32, respectively. This study finds functional redundancy in two pathways: hydrogenotrophic and acetolactic. An increase in OLR promotes bacterial and archaeal abundance and specific methanogenic activity. These results can be applied to the design and operation of sludge digestion for stable, high-rate biogas recovery.

Process stability in expanded granular sludge bed bioreactors enhances resistance to organic load shocks

Environmental perturbations such as changes in organic loading rate (OLR) can have deleterious effects on the anaerobic digestion process, leading to VFA accumulation and process failure. However, the operational history of a reactor, such as prior exposure to VFA build up, can impact a reactor's resistance to shock loads. In the present study, the effects of long term (>100 days) bioreactor (un)stability on OLR shock resistance were assessed. Three 4 L EGSB bioreactors were subjected to varying levels of process stability. Operational conditions such as OLR, temperature and pH were maintained stable in R1; R2 was subjected to a series of minor OLR perturbations and R3 was subjected to a series of non-OLR perturbations, including ammonium, temperature, pH and sulfide. The effect of these different operational histories on each reactor's resistance to a sudden 8-fold increase in OLR were assessed by monitoring COD removal efficiency and biogas production. The microbial communities of each reactor were monitored using 16S rRNA gene sequencing to understand the relationship between microbial diversity and reactor stability. It was determined that the stable (un-perturbed) reactor performed best in terms of its resistance to a large OLR shock, despite its lower microbial community diversity.

Stability improvement of aerobic granular sludge (AGS) based on Gibbs free energy change (∆G) of sludge-water interface

• Δ G sw a can normalize the stability of AGS . • Microbial and chemical properties were more important for Δ G sw a than physical ones. • Reasonable increase in OLR or HSF reduced Δ G sw a and enhanced stability of AGS. The stability of aerobic granular sludge (AGS) has been evaluated by lots of physicochemical and microbial characteristic indicators, but none of them could singly and comprehensively characterize the stability of AGS. Gibbs free energy change (∆G) could reflect the stable state of the whole system by the second law of thermodynamics, so ∆G of the sludge-water interface ( Δ G sw a ) was proposed to characterize the stability of AGS in this study. Organic loading rate (OLR) and hydraulic shear force (HSF) as the primary external energy inputs were selected at different levels in four reactors. Results showed that a reasonable increase in OLR or HSF could reduce Δ G sw a , and its influence on Δ G sw a had two paths: affecting the surface roughness of sludge directly (Path 1); on the other hand, EPS producers like denitrifiers were enriched, promoting the secretion of PN such as tryptophan and protein-like to affect Δ G sw a (Path 2). These indicators were correlated with Δ G sw a significantly, especially genus Paracoccus spp. (class Alphaproteobacteria) (-0.74, p <0.001) and Amide III (-0.81, p <0.001), indicating that Path 2 had a more significant influence on Δ G sw a . In addition, the absolute values of correlation between physical stability indicators and Δ G sw a were around 0.80 ( p <0.001). Therefore, Δ G sw a can be normalized to characterize the stability of AGS. This study establishes Δ G sw a as the normalized indicator for the stability of AGS, which provides specific theoretical guidance for operating parameter regulation in engineering application.

Does carbon cloth really improve thermophilic anaerobic digestion performance on a larger scale? focusing on statistical analysis and microbial community dynamics

Currently, the phenomenon of direct interspecies electron transfer (DIET) is of great interest in the technology of anaerobic digestion (AD) due to potential performance benefits. However, the conditions for the occurrence of DIET and its limits on improving AD under conditions close to real have not been studied enough. This research is concentrated on the effect of conductive carbon cloth (R3), in comparison with a dielectric fiberglass cloth (R2) and control (R1), on the AD performance in large (90 L) thermophilic reactors, fed with a mixture of simulated organic fraction of municipal solid waste and sewage sludge. While organic loading rate (OLR) was gradually increased from 2.4 to 8.66 kg VS/(m3 day), a statistically significant (p < 0.05) difference in biogas production was observed between R1 and both R2 and R3. However, at a maximum OLR of 12.12 kg VS/(m3 day) in R3, an increase in biogas production (p < 0.05) was observed both compared to R1 (by 8.97%) and R2 (by 4.24%). The content of volatile fatty acids in R3 as a whole was the lowest, especially at the maximum OLR. Biofilm on carbon cloth was rich in syntrophic microorganisms of the genera Tepidanaerobacter, as well as Defluviitoga, capable of DIET in mixed cultures with Methanothrix, which was the most abundant methanogen in biofilm. Suspended Bifidobacterium, Fervidobacterium and Anaerobaculum were negatively affected, while Defluviitoga, Methanothermobacter and Methanosarcina, on the contrary, were positively affected by the increase in OLR and showed, respectively, a negative and positive correlation (p < 0.05) with the main AD performance parameters.

Polyhydroxyalkanoates production from ethanol- and lactate-rich fermentate of confectionary industry effluents

Polyhydroxyalkanoate (PHA) production has been the focus of considerable research to increase productivities and reduce production costs. In this study, a fermented confectionary industry wastewater was used as feedstock for mixed microbial culture PHA production. The feedstock was dominated by lactate and ethanol (60–90 % of all soluble fermentation products). The culture selection reactor was inoculated with municipal activated sludge and was operated at an organic loading rate (OLR) of 100 Cmmol·L−1·d−1, achieving a robust PHA-accumulating enrichment, which produced up to 52.6 ± 0.4 wt% of PHA in accumulation assays. An OLR increase in the culture selection stage to 150 Cmmol·L−1·d−1 led to a PHA content of 59.1 ± 0.6, a yield of 0.93 ± 0.01 Cmol-PHA·Cmol-S−1 and a productivity of 0.93 ± 0.01 g-PHA L−1·h−1. A correlation analysis of the impact of ethanol concentrations from 3.19 to 20.3 Cmmol·L−1 in the reactor showed that ethanol inhibited PHA production rate and yield and the consumption of other carbon sources available. Microbial community analysis revealed the increase of Amaricoccus genus during the bioreactor operation time, a known PHA accumulator. The produced polymer was poly(3-hydroxybutyrate) with an average molecular weight of 4.3 × 105 Da and a polydispersity index of 1.88.

Lab- and pilot-scale anaerobic digestion of municipal bio-waste and potential of digestate for biogas upgrading sustained by microbial analysis

The challenge of handling the enormous amount of bio-waste that is globally produced on an annual basis can become an opportunity by exploiting such residues for bioenergy production in the form of biogas or biomethane. The application of anaerobic digestion to bio-waste is still limited due to their specific characteristics (e.g., recalcitrant matter, high solids content, etc.) that might lead to process imbalances and microbial toxicity issues. The present study aimed to elucidate microbial ecology in the lab- and pilot-scale biogas reactors fed with bio-waste. The results showed that the indigenous microbial community in the bio-waste was almost extinct during the digestion process. The AD microbiome was mainly composed of members belonging to the orders Clostridiales and Bacteroidales, whose relative abundance dynamically changed to adapt to operational conditions. The increase in organic loading rate led to the proliferation of members associated with the phylum Synergistetes and the transition to versatile acetoclastic/hydrogenotrophic methanogenic pathways. Furthermore, digestate is a suitable biological inoculum and a nutrient supplement to support further biogas upgrading process. The results identified functional microbes that could benefit bio-waste digestion, unveiled insights into microbiome reorganization, and proposed a potential application of the digestate.

Performance and methane potential of up-flow anaerobic sludge blanket treating thermal hydrolyzed sludge dewatering liquor

Thermal hydrolysis pretreatment could release organic sufficiently from solid into liquid phase to accelerate the high solid sludge anaerobic digestion. Thus, up-flow anaerobic sludge blanket (UASB) could be a promising energy recovery process to treat thermal hydrolyzed sludge dewatering liquor with significantly augmented the organic loading rate (OLR). In this study, its performance was investigated using a lab-scale UASB to treat sludge dewatering liquor after 165 °C, 30 min thermal hydrolysis pretreatment. The results show that 85.57% of the organic in thermal hydrolyzed sludge dewatering liquor could be converted to methane. The UASB adapts to high OLR stably, and the COD removal efficiency was 71.98 ± 1.95% at OLR of 18.35 ± 0.78 kgCOD·(m3·d)-1, and the gap between the maximum potential and experimental methane production yields could be observed during different OLRs. It could be explained as the methanogenesis rate decreased due to the shift of dominant pathway from acetoclastic methanogenesis to syntrophic acetate oxidation following hydrogenotrophic methanogenesis. Methanospirillum became the dominant methanogen with the increase of OLR. In addition, the methane production yield and rate would be hindered till the ammonia nitrogen concentration exceeds 4 g·L-1. Direct interspecies electron transfer could be promising methods to improve UASB performance treating thermal hydrolyzed dewatering liquor.

Bio-Electrochemical Performance of a Ceramic Microbial Fuel Cell Treating Kitchen Waste Leachate: Effect of Organic Loading Rate and Anode Electrode Surface Area

Performance evaluation of a ceramic microbial fuel cell (CMFC) by varying organic strength, hydraulic retention time (HRT) and anode electrode surface area (AESA) to treat leachate generated from acidogenesis of kitchen waste (KW) was studied by the central composite design of experiment. The increase in organic loading rate (OLR) positively affected power density (PD) while negatively influencing organic removal and coulombic efficiency (CE). This behavior is possible due to substrate inhibition and the coercive effect of low HRT, i.e., substrate washout, biofilm abrasion, and reduced contact period, while at high HRT, the volatile fatty acid (VFA) degradation improved. Since acetic acid is the final product of long-chain VFAs degradation, a pseudo consumption order for VFAs was obtained: butyric &gt; propionic &gt; acetic. The AESA aided organics removal and PD but had a negligible effect on CE. According to ANOVA, the COD removal was linearly modeled, while PD and CE were quadratic. The validation runs (VR) proved efficient as the highest COD removal was for VR2 (83.7 ± 3.6%), while maximum PD and CE values obtained were 0.224 ± 0.02 W/m3 and 2.62 ± 0.33%, respectively, for VR3, supported by the lower anode potential.

Bioenergy recovery potential from upflow microaerobic sludge blanket reactor fed with swine wastewater

This paper reports the bioenergy recovery potential inherent to swine wastewater (SWW) when treated in an upflow microaerobic sludge blanket reactor (UMSB) operating with different oxygen loads. The UMSB reactor performance was compared with the one achieved with an upflow anaerobic sludge blanket (UASB) reactor that worked as a control. The biogas production was measured on a lab scale and used to estimate the UMSB reactor self-sufficiency energy. The highest methane yield achieved in the UMSB reactor was 228.6 NL kgCOD−1 d−1 at an organic loading rate (OLR) of 12.2 kgCOD m−3d−1 (HRT of 10 h). Both OLR and air dose increase generated methane dilution in the biogas, which reduced the possibility of electrical energy recovery. Nevertheless, the results showed that the UMSB reactor was self-sufficient and had energy efficiency at the 12 h HRT with doses of 0.17 and 0.25 LO2 Lfeed−1d−1 and at the 10 h HRT with a dose of 0.25 LO2 Lfeed−1d−1. The UMSB reactor achieved an energy return on investment (EROI) of 11.6–18.7, showing a potentially viable alternative for power generation.

Towards engineering application: Integrating current strategies of promoting direct interspecies electron transfer to enhance anaerobic digestion

The study present here was to integrate the current engineering strategies of promoting direct interspecies electron transfer (DIET), ethanol-type fermentation pretreatment, and conductive materials (zero-valent iron [ZVI] and graphite) supplemented, to strengthen the anaerobic digestion of kitchen wastes. Experimental results imply that after ethanol-type fermentation pretreatment, ZVI and graphite supplemented could significantly improve the methane production, transformation efficiency of organic matter, as well as impact resistance ability of systems during anaerobic digestion of kitchen wastes with a gradual increase of organic loading rate. The sludge with ZVI and graphite addition had a relatively higher capacitance and lower resistance than that without ZVI and graphite. With the concentration ratio of ZVI and graphite increasing, the evidently increased abundance of electrotrophic methanogens, Methanosarcina acetivorans, and Methanospirillum hungatei suggested that ZVI stimulated the growth of electrotrophic methanogens. Together with the enrichment of exoelectrogens capable of extracellular electron transfer (e.g., Streptococcus, Petrimonas, and Syntrophomonas species) in the presence of ZVI and graphite, the DIET between these exoelectrogens and electrotrophic methanogens might be responsible for the improved performances and stability.

Valorization of Brewery Waste through Polyhydroxyalkanoates Production Supported by a Metabolic Specialized Microbiome

Simple SummaryRaw brewers’ spent grain, a by-product of beer production, is produced at a large scale and is usually used as animal feed or is landfilled. However, its composition shows that this feedstock has the potential for other applications, such as bioplastics production (e.g., polyhydroxyalkanoates). In this way, the aim of this work was to assess the use of raw brewers’ spent grain for polyhydroxyalkanoates production, adding new value to this feedstock. The results confirm the potential of raw brewers’ spent grain to produce polyhydroxyalkanoates, as the population was enriched in the microorganisms able to accumulate these biopolymers. These results will contribute to society’s knowledge and competence via the development of a treatment process for brewery waste of both environmental (productive waste treatment) and economic interest (production of biopolymers), which will certainly attract its application to the brewery industry worldwide.Raw brewers’ spent grain (BSG), a by-product of beer production and produced at a large scale, presents a composition that has been shown to have potential as feedstock for several biological processes, such as polyhydroxyalkanoates (PHAs) production. Although the high interest in the PHA production from waste, the bioconversion of BSG into PHA using microbial mixed cultures (MMC) has not yet been explored. This study explored the feasibility to produce PHA from BSG through the enrichment of a mixed microbial culture in PHA-storing organisms. The increase in organic loading rate (OLR) was shown to have only a slight influence on the process performance, although a high selectivity in PHA-storing microorganisms accumulation was reached. The culture was enriched on various PHA-storing microorganisms, such as bacteria belonging to the Meganema, Carnobacterium, Leucobacter, and Paracocccus genera. The enrichment process led to specialization of the microbiome, but the high diversity in PHA-storing microorganisms could have contributed to the process stability and efficiency, allowing for achieving a maximum PHA content of 35.2 ± 5.5 wt.% (VSS basis) and a yield of 0.61 ± 0.09 CmmolPHA/CmmolVFA in the accumulation assays. Overall, the production of PHA from fermented BSG is a feasible process confirming the valorization potential of the feedstock through the production of added-value products.

Enhanced sewage sludge treatment via parallel anaerobic digestion at the upper mesophilic level

Sewage mixed sludge (MS) digestion performance was ameliorated implementing the parallel digestion model for primary sludge (PS) and secondary sludge (SS) (waste activated sludge) as domestic sewage sludge fractions rich in oil and grease content at the upper mesophilic level (40 °C). Optimization of the organic loading rate (OLR) was conducted in parallel semi-continuous bench-scale digesters for PS, SS and MS. Comparatively evaluated performance and biosolid quality parameters were methane production rates, volatile solid (VS) reduction, oil and grease and nutrient content, dewaterability and electrical conductivity (EC). OLR optimization indicated different retention time needs for PS and SS stabilization and enabled 18% and 93% higher VS loading and reduction, respectively, compared to MS digestion. Inhibitory effect followed an ascending pattern as a result of OLR increase in each digestion line acting on the hydrolysis of proteinaceous matter and acetogenesis rather than methanogenesis. A high number of long chain fatty acids was detected in the raw sludges. The enhancing effect of the upper mesophilic temperature was significant in SS digestion with increased biodegradability, oil and grease removal and microbial growth compared to digestion at 35 °C. The parallel digestion system and upper mesophilic temperature proved a useful tool to enhance VS loading and reduction without worsening the stabilized biosolids’ dewaterability as a feasible model in the existing and prospective municipal wastewater treatment plants (WWTPs). The weakness of the MS digestion was diagnosed as the lower synthesis degree of biomass induced by the dilution of the substrate in PS by SS mixing which weakened the microbial tolerance to high OLR and inhibition. The output indicated the potential of parallel AD, importance of the optimization for OLR and temperature to advance the performance and flexibility of the sludge line practice in municipal WWTPs.

Recovery of biomethane from a submerged anaerobic membrane bioreactor treating domestic wastewater blended with semi-solid organic wastes discharged from residential establishments

Recent research studies on the innovative concept of submerged anaerobic membrane bioreactor (SAnMBR) technology have demonstrated superior treatment and operational performance for treating a broad range of waste streams discharged from various industries. This study aimed to investigate the treatment and recovery of biomethane (bio-CH4) performance of ceramic ultrafiltration (UF) coupled with ”co-digestion based SAnMBR”, which was not previously studied by others, for treating an organic fraction of food waste (OFFW) blended with domestic wastewater (DWW) at surge organic loading rates (OLRs) disposed at modern high-rise establishments and similar residential clusters. The SAnMBR was operated in five phases (Phase 1–5), with different organic loading rates (OLRs) varying from 0.49 to 22.57 kg-COD/m3/d. All bio-CH4, mixed liquor sludge, and treated permeate samples were analyzed using standard methods. The key parameters representing the cumulative bio-CH4 yield during each phase were estimated using sigmoidal models, and the simulated results were validated using ANOVA. It was found that the SAnMBR produced high-quality, low-turbid reclaimed water showing an increasing trend in yield of bio-CH4 with an increase of OLR. It was also observed that the SAnMBR demonstrated stable and superior treatment performance at shock-loads of organics. The maximum bio-CH4 yield recorded during the study was 73.06 ± 6.48%. The findings of this study confirmed the suitability of applying this novel concept of ”co-digestion-based SAnMBR” towards sustainable and efficient waste management in modern-high rise establishments.

Thermophilic anaerobic co-digestion of glycerol and cheese whey – Effect of increasing organic loading rate

The organic loading rate (OLR) is one of the variables that directly affects anaerobic digestion. An increase in OLR can improve methane production, but it can also lead to process failures. Therefore, determining the proper OLR for the process is of great importance. This study analyzed the effect of increasing the OLR on cheese whey and glycerol co-digestion in a thermophilic anaerobic fluidized bed reactor (AFBR) by varying both the influent concentration and the hydraulic retention time (HRT). The increase in OLR from 5 to 20 gCOD.L−1.d−1 was initially performed by increasing the influent concentration from 5 to 7.5, 10, 15, and 20 gCOD.L−1, at HRT of 24 h. Organic matter removal (87.7%), methane yield (MY) (253.0 mL CH4.gCOD−1rem), and methane production rate (MPR) (3.2 L CH4. L−1.d−1) showed the best performance at 10 gCOD.L−1.d−1. Conversely, raising the OLR to 20 gCOD.L−1 enhanced the buildup of volatile fatty acids, resulting in a 38.5% decrease in MY. Based on these findings, the HRT was reduced from 24 h to 20 h and 16 h at influent concentration of 10 gCOD.L−1 resulting in OLR of 10, 12, and 15 gCOD.L−1.d−1, respectively. The HRT at 20 h (12 gCOD.L−1.d−1) provided the highest MY values (around 292.5 mL CH4.gCOD−1rem), while the maximum MPR was observed at 16 h (5.1 L CH4. L−1.d−1). The main metabolites observed in all conditions were acetic acid (31.1–66.8%) and propionic acid (10.9–61.5%). The OLR also affected the microbial community, with Proteobacteria accounting for 53.1% of the relative abundance at 5 gCOD.L−1.d−1 while Firmicutes accounted for 76.6% at 10 gCOD.L−1.d−1. At 10 gCOD.L−1.d−1, with maximum MY, the bacteria observed with the highest relative abundance were an unidentified genus of Lentimicrobiaceae (8.9%), “Blvii28 wastewater sludge group” (2.9%), and Tolumonas (1.4%). The archaea identified with the highest relative abundance at both OLRs (5 and 10 gCOD.L−1.d−1) was hydrogenotrophic Methanobacterium (27.3% and 2.6%, respectively).

Semi-continuous anaerobic digestion of the organic fraction of municipal solid waste: digester performance and microbial population dynamics

Anaerobic digestion is an attractive approach for the management of organic fraction of municipal solid waste (OFMSW) and for the recovery of energy from this waste. A semi-continuous digestion of OFMSW was conducted on stirred reactor under mesophilic condition. Three organic loading rates (OLRs) were tested throughout the anaerobic process (1.36, 2.5 and 3.5 g VS/L.d). The achieved results showed that biogas yield decreased with the increase of OLR. Thus, the highest average of biogas yield, 0.51 L/g VS, was recorded at low OLR (OLR1:1.36 gVS/L.d). Likewise, optimal VS removal, pH, VFA and alkalinity were obtained at OLR1 compared to the other tested OLR. During the anaerobic digestion, the dynamic of microbial community was also assessed by the high-throughput sequencing technology. Firmicutes, Bacteroidetes and Proteobacteria were the dominant phyla during the digestion process. This could be related to their roles in hydrolysis of different OFMSW compounds, as well as in acidogenesis and acetogenesis steps. Regarding Archaeal population, the relative abundance of the Methanoculleus genus declined, while Methanosarcina increased over time. This indicated that acetotrophic and hydrogenotrophic pathways were used for methane production.

A comparative study on simultaneous recovery of phosphorus and alginate-like exopolymers from bacterial and algal-bacterial aerobic granular sludges: Effects of organic loading rate

The effects of organic loading rate (OLR) on simultaneous phosphorus (P) and alginate-like exopolymers (ALE) recovery from bacterial aerobic granular sludge (AGS) and algal-bacterial AGS were examined and compared during 70 days’ operation. With the increase of OLR (0.6–1.2 g COD/(L·day)), both AGS showed good settleability and granular strength with P bioavailability > 92% (Stage III). The moderate increase in OLR had a positive influence on simultaneous recovery of P and ALE. On day 60, the contents of ALE and guluronic acid/guluronic acid (GG) blocks reached the highest in algal-bacterial AGS, about 13.37 and 2.13 mg/g-volatile suspended solids (VSS), respectively. Meanwhile, about daily 0.55 kg of P is estimated to be recovered from the wastewater treatment plant with a treatment capacity of 10,000 m3/day. P mass balance analysis during ALE extraction from both AGS was conducive to further evaluation of P removal pathway and its application potentials.

Plant-associated microbial communities converge in fermentative hydrogen production and form a core microbiome

This study presents the taxonomic characterization and fermentative activity of bacteria and fungi present in four plant-associated microbial communities: corn stover (CS), wheat straw (WS), sugarcane bagasse (SCB), and agave bagasse (AB). Fiber soaking, fermentation number, and organic loading rate (OLR) were studied in semicontinuous reactors fed with untreated substrates under a consolidated bioprocessing approach. WS, SCB, and AB communities converged to a core microbiome with the predominance of Lactobacillus, Clostridium, Enterobacter, and the fungus Pichia. After the fourth fermentation, hydrogen productivity became stable and similar among microbial communities (1.62 L-H2/kg-day), except for the CS community. The OLR increase promoted the hydrogen production from lactate and acetate. Lactobacillus positively correlated with H2 productivity and polysaccharide degradation, and Clostridium positively correlated only with polysaccharide degradation. Results demonstrated that Lactobacillus played a key role in producing high hydrogen productivities from lignocellulosic substrates. While the OLR increase promoted metabolic pathways that favored fermentative hydrogen production.

Correction: Pereira et al. Effect of the Progressive Increase of Organic Loading Rate in an Anaerobic Sequencing Batch Reactor for Biodiesel Wastewater Treatment. Water 2022, 14, 223

In the original article [1], there were the following mistakes:-In Table 4, where it reads “kap” it should read “kap” [...]

Effect of the Progressive Increase of Organic Loading Rate in an Anaerobic Sequencing Batch Reactor for Biodiesel Wastewater Treatment

The wastewater from the biodiesel industry is an environmental problem, and from a sanitation resources perspective, the anaerobic sequencing batch reactor (ASBR) is an interesting alternative for wastewater treatment. A better understanding of ASBR operation behavior under the progressive increase of the organic loading rate (OLR) is crucial for upscaling. The objective of this study was to monitor an ASBR operating with an OLR ranging from 1.3 to 9.3 kgCOD m−3 d−1. The average chemical oxygen demand (COD) removal efficiencies of the ASBR were 52, 41, 47, and 11% for phases 1, 2, 3, and 4, respectively. The apparent kinetic coefficient, i.e., the rate of degradation of organic matter, was between 0.10 and 1.80 h−1, considering the kinetic model that considers the residual substrate concentration, which was the one that best fit the obtained data. The progressive increase in applied OLR modified the microbial biomass diversity, which in turn influenced the degradation kinetics of the organic matter. In addition, the values of the applied OLR of 5.1 kgCOD m−3 d−1 and a food to microorganism ratio (F/M) of 0.6 kgCOD kgVSS−1 d−1 were shown to be limiting values that promoted the overload of ASBR.