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Hydrogen is a renewable fuel that can be biologically produced by green algae in closed anaerobic photobioreactors with light and organic carbon as energy sources. This research aimed to investigate the influence of sulfur concentration and light intensity on hydrogen and ethanol production, as well as on nutrient removal by Chlamydomonas reinhardtii (CC425) in batch cultures. The strain was cultivated in two phases: in the first step, the cultures were maintained under aerobic conditions to obtain biomass; in the second step, the biomass was transferred to closed anaerobic photobioreactors for gas generation under continuous illumination. A factorial design was accomplished to improve the biomass production in the first step, with light variation, pH, and glucose addition. Afterward, light intensity and sulfur concentration were varied to test hydrogen production in the second step. The best hydrogen production occurred in photobioreactors without sulfur addition (average increase of 7 times in the production) and under higher light intensity the productivity was 37% higher than lower light intensity (39.64 ± 2.44 µmol H2 L−1 h−1). There was an effect of sulfur concentration in the ethanol production and under higher light intensity the production was higher (203.20 ± 31.49 mg L−1). Furthermore, under conditions with the presence of sulfur, there was greater removal of ammoniacal nitrogen (5.3%), phosphate (85.0%), COD (9.1%) and acetic acid (97.2%). This research demonstrates the efficient production of hydrogen by C. reinhardtii and it shows that the process can be associated with ethanol production and nutrient removal. [ABSTRACT FROM AUTHOR]

• The increase of CO 2 flowrate enhanced the CO 2 dissolution. • The highest CO 2 dissolved was reached through the gas diffusion electrode. • High CO 2 dissolved improved acetate synthesis in microbial electrosynthesis system. • The lowest CO 2 flowrate allowed better retention cell at gas diffusion electrode. Carbon dioxide (one of the main greenhouse gases) can be used as a raw material in microbial electrosynthesis system (MES) for the production of valuable organic compounds. However, one of the major drawbacks associated with the MES is the mass transfer limitation of CO 2 in the aqueous phase. In order to overcome this limitation, several operational strategies such as the increase of CO 2 flow rate have been proposed. Therefore, the present paper assessed an H-type MES (H-Cell) carried out under CO 2 pure gas supplied at 5, 10 and 20 mL min−1, and a gas diffusion electrode (GDE) MES (VITO-Cell) under 5 and 20 mL min−1. In both the MESs, the increase of the CO 2 flow rate led to the improvement of inorganic carbon concentration, reaching until 1068 ± 115 mg L−1 in VITO-Cell. Consequently, in H-Cell the maximum acetate production rate increased from 45 to 270 mg L−1 d−1 when the CO 2 flow varied from 5 to 20 mL min−1. In VITO-Cell the maximum acetate production rate reached 85 mg L−1 d−1 at 5 mL min−1 CO 2 flow rate due to a better gas-liquid mass transfer coefficient of CO 2 provided by the GDE. [ABSTRACT FROM AUTHOR]

[Display omitted] • Removing sulfate during fermentation maximizes methane evolution from vinasse. • Improved methanogenesis enhances the energy yield of biodigestion by >30%. • Exploiting biohydrogen increases the energy yield of biodigestion by only 2–6%. • Dosing fewer chemicals is economically healthier than increasing the energy yield. • Biomethane production towards diesel replacement provides the highest profitability. Anaerobic digestion is recognizably the most efficient approach (on both energetic and environmental bases) to manage sugarcane vinasse in ethanol-producing plants. In particular, separating the fermentation from methanogenesis (two-stage schemes) step improves the process by providing higher stability to methanogens. Based on experimental data, this study compared the techno-economics of different operating strategies for the two-stage biodigestion of sugarcane vinasse: biohydrogen exploitation, non-recovery of biohydrogen and removal of sulfate (fermentation) coupled to two alkalinization approaches in methanogenesis (NaHCO 3 dosing or NaOH dosing + liquid phase recirculation). Potential biogas uses included the production of electricity, purified biohydrogen or biomethane. Removing sulfate during the fermentation increased the energy yield of biodigestion by over 30% (peaking at 914 TJ when producing biomethane), a 5-fold higher level than exploiting biohydrogen (contribution of 25.3 TJ). However, the non-optimized dosing of chemicals still represents the main economic bottleneck of the process, nullifying the aforementioned energy gains. Replacing NaHCO 3 dosing in the sulfidogenic-fermentative reactors by recycling the bicarbonate produced during methanogenesis coupled to minimizing the inputs of NaOH in the methanogenic units provided the best economic performance: internal rates of return of 21.6% (electricity production) and 28.9% (biomethane production towards diesel replacement). The highly efficient production of electricity using the combined cycle represents an attractive alternative for exploiting the vinasse-derived biogas in a short-term time horizon, whilst maximizing the economic exploitation of biomethane was found to directly depend on the replacement of diesel. Overall, exploiting the biogas produced from vinasse is profitable; however, the maximization of gains depends more on a rational use of chemicals than on more efficient methane evolution rates. [ABSTRACT FROM AUTHOR]

Hydrogen can be generated from cyanobacteria cultivation with light and organic carbon as an energy source. The aim of this study was to investigate the influence of ammonium and glucose concentration, and the culture age on the production of hydrogen and other products, and phosphate and organic carbon removal by Anabaena sp. (UTEX 1448) in batch anaerobic photobioreactors. Our results demonstrated an effect of culture age and ammonium concentration in hydrogen production, an average increase of 4.1 times (90.4 μmol H 2 mg Chl a −1 h−1 and 13.2 mmol mg Chl a −1) in the conditions with younger biomass and without ammonium. Culture age also had an effect in phosphate removal, with 92% of removal efficiency, and ethanol production (an average increase of 2.9 times–97 mg L−1), however the optimum conditions were obtained with older biomass. This study demonstrates efficient hydrogen production by this strain of Anabaena sp. fewer researched. [ABSTRACT FROM AUTHOR]

Biodegradation of organic micropollutants is likely to occur due to cometabolism by particular microbial groups. In an effort to identify the stages of anaerobic digestion potentially involved in the biodegradation of the veterinary antimicrobial sulfamethazine (SMZ), the influence of selected carbon sources (sucrose, glucose, fructose, ethanol, meat extract, cellulose, soluble starch, soy oil, acetic acid, propionic acid and butyric acid) on SMZ removal by anaerobic sludge was evaluated in short-term batch experiments. Adsorption to the granular sludge constituted a significant removal mechanism, accounting for 39% of SMZ removal in control experiments. The presence of glucose, fructose, sucrose and meat extract exerted an inducing effect on SMZ degradation, resulting in removal efficiencies of 54, 53, 58 and 61%, respectively, indicating the occurrence of cometabolism. Time courses of sucrose and meat extract degradation revealed markedly distinct organic acid profiles but resulted in similar SMZ removals. Temporal profiles of acetic and propionic acid degradation were not associated with SMZ removal, as changes in SMZ concentration were observed even after the organic acids had been completely removed. The experimental results suggest that SMZ cometabolism is not associated to sucrose hydrolysis, acetoclastic methanogenesis and acetogenesis from propionic acid. [ABSTRACT FROM AUTHOR]

Microbial electrosynthesis (MES) technology relies on the direct use of electrons to convert CO 2 into long chain organic chemicals. Therefore, MES has been proposed to be coupled to the renewable electricity supply, mainly from solar and wind sources. However, those energies suffer fluctuations and interruptions of variable duration, which can have an adverse effect on MES performance. Such effects on MES has been evaluated for the first time under different interruptions time. H-cell-MES reactors were disconnected from power supply during 4, 6, 8, 16, 32 and 64 h. Interruptions affected the acetate production rate, causing a decrease of until 77% after 64 h off. However, after all the interruptions, the acetate production was restored, taking between 7 and 16 h for the reduction current to turn steady. Therefore, microbial community on MES proved to be resilient and able to recover the electro-autotrophic activity despite the duration of current supply interruptions. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) is the most suitable approach for managing vinasse, the main wastewater from ethanol production, based on potential biogas applications. However, despite significant improvements in both scientific and technological aspects of the AD of vinasse, specific aspects of the global process require a better understanding to facilitate the scale-up of treatment systems. In this context, this study aimed to identify the main factors that affect the economic performance of the AD of vinasse in sugarcane biorefineries using a techno-economic approach. The energy recovery potential, as well as economic parameters were obtained for different biogas applications. Sensitivity analysis was also used to assess the impacts of different factors on the profitability of the process. Overall, biomethane production economically outperformed electricity generation, regardless of the biorefinery type (autonomous or annexed) and AD layout (single- or two-phase). In turn, investment costs on AD-power plants and product (electricity or biomethane) prices characterized the primary factors governing the economic performance of biogas reuse, regardless of the proposed application. These results confirm the key role of external agents in encouraging the implementation of AD plants in ethanol biorefineries by establishing specific funding for biogas projects, imposing environmental restrictions and/or developing competitive AD-related technological packages. [ABSTRACT FROM AUTHOR]

• Full-scale anaerobic biodigestion plants applied to sugarcane vinasse were assessed. • Techno-economic aspects were investigated for different biogas applications. • Sensitivity analysis indicated the main factors governing process profitability. • Biomethane production economically outperformed the generation of electricity. • Investment costs and product prices primarily affected process economics. Anaerobic digestion (AD) is the most suitable approach for managing vinasse, the main wastewater from ethanol production, based on potential biogas applications. However, despite significant improvements in both scientific and technological aspects of the AD of vinasse, specific aspects of the global process require a better understanding to facilitate the scale-up of treatment systems. In this context, this study aimed to identify the main factors that affect the economic performance of the AD of vinasse in sugarcane biorefineries using a techno-economic approach. The energy recovery potential, as well as economic parameters were obtained for different biogas applications. Sensitivity analysis was also used to assess the impacts of different factors on the profitability of the process. Overall, biomethane production economically outperformed electricity generation, regardless of the biorefinery type (autonomous or annexed) and AD layout (single- or two-phase). In turn, investment costs on AD-power plants and product (electricity or biomethane) prices characterized the primary factors governing the economic performance of biogas reuse, regardless of the proposed application. These results confirm the key role of external agents in encouraging the implementation of AD plants in ethanol biorefineries by establishing specific funding for biogas projects, imposing environmental restrictions and/or developing competitive AD-related technological packages. [ABSTRACT FROM AUTHOR]

Although a novel anaerobic down-flow structured bed reactor has shown feasibility and stable performance for a long-term compared to other anaerobic fixed bed systems for continuous hydrogen production, the volumetric rates and yields have so far been too low. In order to improve the performance, an operation strategy was applied by organic loading rate (OLR) variation (12–96 g COD L −1 d −1 ). Different volumetric hydrogen rates, and yields at the same OLR indicated that the system was mainly driven by the specific organic load (SOL). When SOL was kept between 3.8 and 6.2 g sucrose g −1 VSS d −1 , the volumetric rates raised from 0.1 to 8.9 L H 2 L −1 d −1 , and the yields were stable around 2.0 mol H 2 mol −1 converted sucrose. Furthermore, hydrogen was produced mainly via ethanol-type fermentation, reaching a total energy conversion rate of 23.40 kJ h −1 L −1 based on both hydrogen and ethanol production. [ABSTRACT FROM AUTHOR]

The replacement of fossil fuels by biofuels has been extremely important worldwide to stimulate the growth of economies based on the sustainability through the use of renewable resources. Anaerobic digestion for biogas production is recognized as a clean technology that allies the suitability of wastes with energy generation, fulfilling the requirements for a sustainable alternative to provide the optimization of the biofuels production. This alternative is especially interesting for the sugarcane ethanol production in Brazil, in which the generation of vinasse, the main liquid waste, is very expressive. Nevertheless, the use of vinasse for anaerobic digestion has been finding some challenges to its establishment in the Brazilian sugarcane biorefineries. This paper reviews the actual context of anaerobic digestion within the sugarcane ethanol production in Brazil, presenting the main obstacles for its full application and the directions to promote it as well. Alternatives for biogas use are also presented and compared, highlighting the environmental and energy advantages of applying anaerobic digestion in the sugarcane biorefineries. This scenario is envisaged as a suitable way to achieve the future biorefineries model, based on the use and recovery of renewable resources with economic, social, and environmental benefits. [ABSTRACT FROM AUTHOR]

Highlights: [•] Biohydrogen from glucose in an up-flow anaerobic packed bed reactor was studied. [•] Design modification were made in the settling zone to capture the detached biomass. [•] Impact of organic loading rate on hydrogen yield were assessed. [•] Maximum hydrogen yield of 2.1mol-H2 mol−1-glucose was achieved. [•] The biomass yield in the modified system was lower than the conventional system. [Copyright &y& Elsevier]

Abstract: This paper reports on results obtained from experiments carried out in an acidogenic anaerobic reactor aiming at the optimization of hydrogen production by altering the degree of back-mixing. It was hypothesized that there is an optimum operating point that maximizes the hydrogen yield. Experiments were performed in a packed-bed bioreactor by covering a broad range of recycle ratios (R) and the optimum point was obtained for an R value of 0.6. In this operating condition the reactor behaved as 8 continuous stirred-tank reactors in series and the maximum yield was 4.22 mol H2 mol sucrose−1. Such optimum point was estimated by deriving a polynomial function fitted to experimental data and it was obtained as the conjugation of three factors related to the various degrees of back-mixing applied to the reactor: mass transfer from the bulk liquid to the biocatalyst, liquid-to-gas mass transfer and the kinetic behavior of irreversible reactions in series. [Copyright &y& Elsevier]

Biological sulfate reduction was studied in a laboratory-scale anaerobic sequential batch reactor (14 L) containing mineral coal for biomass attachment. The reactor was fed industrial wastewater with increasingly high sulfate concentrations to establish its application limits. Special attention was paid to the use of butanol in the sulfate reduction that originated from melamine resin production. This product was used as the main organic amendment to support the biological process. The reactor was operated for 65 cycles (48 h each) at sulfate loading rates ranging from 2.2 to 23.8 g SO4 2−/cycle, which corresponds to sulfate concentrations of 0.25, 0.5, 1.0, 2.0 and 3.0 g SO4 2− L−1. The sulfate removal efficiency reached 99% at concentrations of 0.25, 0.5 and 1.0 g SO4 2− L−1. At higher sulfate concentrations (2.0 and 3.0 g SO4 2− L−1), the sulfate conversion remained in the range of 71–95%. The results demonstrate the potential applicability of butanol as the carbon source for the biological treatment of sulfate in an anaerobic batch reactor. [Copyright &y& Elsevier]

Abstract: This paper analyzes the influence of carbon source and inoculum origin on the dynamics of biomass adhesion to an inert support in anaerobic reactors fed with acid mine drainage. Formic acid, lactic acid and ethanol were used as carbon sources. Two different inocula were evaluated: one taken from an UASB reactor and other from the sediment of a uranium mine. The values of average colonization rates and the maximum biomass concentration (C max) were inversely proportional to the number of carbon atoms in each substrate. The highest C max value (0.35g TVSg−1 foam) was observed with formic acid and anaerobic sludge as inoculum. Maximum colonization rates (v max) were strongly influenced by the type of inoculum when ethanol and lactic acid were used. For both carbon sources, the use of mine sediment as inoculum resulted in a v max of 0.013g TVSg−1 foam day−1, whereas 0.024g TVSg−1 foam day−1 was achieved with anaerobic sludge. [Copyright &y& Elsevier]

This paper reports on the design of a new reactor configuration - an upflow fixed-bed combined anaerobic-aerobic reactor - can operate as a single treatment unit for the removal of nitrogen (≍150 mg N/L) and organic matter (≍1300 mg COD/L) from Lysine plant wastewater. L-Lysine, an essential amino acid for animal nutrition, is produced by fermentation from natural raw materials of agricultural origin, thus generating wastewater with high contents of organic matter and nitrogen. The best operational condition of the reactor was obtained with a hydraulic retention time of 35 h (21 h in the anaerobic zone and 14 h in the aerobic zone) and a recycling ratio (R) of 3.5. In this condition, the COD, total Kjeldahl nitrogen (TKN), and total nitrogen (TN) removal efficiencies were 97%, 96%, and 77%, respectively, with average effluent concentrations of 10 ± 36 mg COD/L, 2 ± 1 mg NH4+-N/L, 8 ± 3 mg Org-N/L, 1 ± 1 mg NH2--N/L, and 26 ± 23 mg NH3--N/L. [ABSTRACT FROM AUTHOR]

Abstract: Data on the performance of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor subjected to step increases of organic loading rates (OLR) and to organic shock loads (OSL) are presented and discussed. The tubular reactor (100cm long and 5cm diameter) with a useful volume of 1995mL was filled with polyurethane foam cubic matrices holding immobilized biomass and fed with synthetic wastewater. The reactor was operated at the controlled temperature of 30±1°C and hydraulic retention time of 7h. After about 15 days, the HAIB reactor attained operating stability. Thereafter, it was subjected to step increases of the applied OLR that ranged from 6.8 to 18.8kgCOD/m3 d. After steady state had been achieved at each step, OSL corresponding to approximately three times the operating OLR were applied for 7h. No disturbance was observed due to the step increase in OLR. An increase in effluent chemical oxygen demand (COD) and volatile fatty acids (VFA) concentrations and a decrease in the percentage of methane in the biogas were observed due to OSL applications. However, stability of the monitoring parameters was always restored approximately 17h after the application of OSL for all conditions tested. [Copyright &y& Elsevier]

[Display omitted] • Organic matter conversion was unsatisfactory (<80%) when dosing only NaOH. • NaHCO 3 dosing and effluent recirculation performed equally up to 7.5 kg-COD m−3 d−1. • 2-fold higher (15 vs. 7.5 kg-COD m−3 d−1) organic load was reached by dosing NaHCO 3. • F/M ratio > 3.0 g-COD g−1VSS d−1 was associated with high and stable CH 4 production. • Excess VFA levels in the feeding chambers triggered organic overloading conditions. Energetic exploitation of sugarcane-derived byproducts via anaerobic digestion (AD) has recently been highlighted as an alternative to the conventional ethanol-producing approach. In this context, the thermophilic (55 °C) methane production from fermented molasses was assessed in the long-term (>200 d) continuous operation of two anaerobic structured-bed reactors. Two types of alkalinization strategies, namely, NaHCO 3 dosing (RM1) and NaOH dosing coupled to effluent recirculation (RM2) were compared, as well as different levels of organic loading rate (OLR) and hydraulic retention time (HRT) were applied to reach limiting operating conditions. Both alkalinization strategies provided an equivalent buffer control up to an OLR of 7.5 kg-CODt m−3 d−1, from which unwanted accumulation of organic acids was observed in RM2. NaHCO 3 dosing enabled doubling the OLR (15.0 kg-CODt m−3 d−1) without performance deterioration, i.e., organic matter removal > 80.0% and maximum methane yield values. A detailed assessment of the food-to-microorganism ratio demonstrated the maintenance of stable operating conditions at excess substrate availability (>3.0 g-CODt g−1VSS d−1) in the feeding chamber (FDC) of the reactors, in which substrate conversion exceeded 70.0%. Organic overloads occurred only when biomass retention reached a saturation level in the FDC, hampering the uptake of volatile organic acids, regardless of the operating condition. In any case, the wide range of operating conditions (OLR = 2.5–15.0 kg-CODt m−3 d−1 and HRT = 24.0–36.0 h) associated with maximized methane production characterized a highly flexible process, which enables varied design arrangements in full-scale AD plants. [ABSTRACT FROM AUTHOR]

The anaerobic processing of sugarcane vinasse has been recently highlighted as an effective approach to both mitigate negative impacts of its inadequate management and recover renewable energy through biogas production. However, basic aspects of the process still require further investigations, such as understanding the impacts of the compositional variability of vinasse on the overall performance of anaerobic systems. In this context, the impacts of different types of sugarcane vinasse, i.e., from annexed (VinAn) and autonomous (VinAu) ethanol plants and spirit production (VinAl), on methane production and organic matter removal were assessed under mesophilic conditions (37 °C) from a kinetic perspective. The energetic potential of the biogas was also investigated regarding micro (methane yield) and macro (contributions to the Brazilian energy matrix) scales. The availability of biodegradable organic matter and sulfate had a direct impact on the kinetics of methane production, associating a 2-fold higher initial methane production rate with VinAl (10.12 NmL h−1) compared to VinAn (5.95 NmL h−1) and VinAu (4.25 NmL h−1). However, the methane yield was not affected by the compositional variations (328–339 NmL-CH 4 g−1COD), which indicates that vinasse may be efficiently used as substrate for bioenergy generation, regardless of its origin. The global energy production estimated for VinAn (24,816 GWh) was over 6- and 7-fold higher compared to VinAu (3984 GWh) and VinAl (3035 GWh) due to discrepancies in vinasse generation flow rates, potentially increasing the available renewable power supply in Brazil by 2.2% or over 1400% of the current bioenergy produced from biogas. Overall the electric energetic potential of sugarcane vinasses (14,486 GWh) could replace over 20% of natural gas or 90% of coal use in Brazil, satisfactorily decreasing the dependence on non-renewable energy sources. Image 1 • Bioenergy recovery from different types of sugarcane vinasse was investigated. • The availability of organic matter and sulfate directly impacts process kinetics. • Compositional variations do not impact the methane yield. • Vinasse from annexed ethanol plants presented the highest global energy potential. • Energy from biogas could replace 90% of the coal-derived energy in Brazil. [ABSTRACT FROM AUTHOR]

• Sugarcane vinasse thermophilic dark fermentation was assessed. • Proper operating strategies offset seasonal compositional variations in vinasse. • Biohydrogen production was maximized at pH values between 5.0 and 5.5. • A sulfidogenic-acidogenic system was established at pH values above 6.0. • Lactate was confirmed as the main substrate for biohydrogen production from vinasse. An innovative application of the anaerobic structured-bed reactor (AnSTBR) in thermophilic dark fermentation of sugarcane vinasse targeting biohydrogen (bioH 2) production was assessed. A detailed metabolite monitoring program identified the major substrates and primary metabolic pathways within the system. Increasing the applied organic loading rate positively affected bioH 2 production, reaching 2074 N mL-H 2 L−1 d−1 and indicating an optimal load of approximately 70 kg-COD m−3 d−1. Controlling the fermentation pH (5.0–5.5) was the primary strategy to maintain bioH 2 -producing conditions, offsetting negative impacts associated with the compositional variability of vinasse. Metabolic correlations pointed out lactate as the primary substrate for bioH 2 production, indicating its accumulation as evidence of impaired reactors. The versatility of the acidogenic system was confirmed by identifying three major metabolic pathways according to the pH, i.e., lactate-producing (pH <5.0), bioH 2 -/butyrate-producing (pH = 5.0–5.5) and bioH 2 -producing/sulfate-reducing (pH >6.0) systems, which enables managing the operation of the reactors for diversified purposes in practical aspects. [ABSTRACT FROM AUTHOR]

Antibiotics from sulfonamide, fluoroquinolone, and diaminopyrimidine classes are widely used in human and veterinary medicine, and their combined occurrence in the aquatic environment is increasing around the world. In parallel, the understanding of how mixtures of these compounds affect non‐target species from tropical freshwaters is scarce. Thus, this work aimed to study the long‐term reproductive, recovery, and swimming effects of mixtures of 12 antibiotics from three different classes (up to 10 μg L−1) added to freshwater (FWM) and synthetic wastewater (SWM) matrices on freshwater worm Allonais inaequalis. Results revealed that at the reproduction level, the exposure to antibiotics in the SWM matrix does not cause a significant toxic effect on species after 10 days. On the other hand, exposures to initial dose mixtures (10 μg L−1 each) in FWM caused a significant reduction of offspring by 19.2%. In addition, recovery bioassays (10 days in an antibiotic‐free environment) suggested that A. inaequalis has reduced offspring production due to previous exposure to antibiotic mixtures in both matrices. Furthermore, despite slight variation in swimming speed over treatments, no significant differences were pointed out. Regarding antibiotics in the water matrices after 10‐day exposures, the highest concentrations were up to 2.7, 7.8, and 4.2 μg L−1 for antibiotics from sulfonamide, fluoroquinolone, and diaminopyrimidine classes, respectively. These findings suggest that a species positioned between primary producers and secondary consumers may experience late reproductive damage even in an antibiotic‐free zone, after previous 10‐day exposure to antibiotic mixtures. Practitioner Points: A mixture of sulfonamide, fluoroquinolone, and diaminopyrimidine antibiotics in freshwater affects the offspring production of A. inaequalis after 10 days.After the 10‐day antibiotic exposure, the reproduction of A. inaequalis remains affected in an antibiotic‐free environment over the recovery period.The swimming speed of the worms does not change after 10 days of exposure to the antibiotic mixture.The concentration of dissolved solids can limit the natural degradation of sulfonamide, fluoroquinolone, and diaminopyrimidine antibiotics in the aquatic environment. [ABSTRACT FROM AUTHOR]

Microalgae and cyanobacteria interactions with autochthonous bacteria have been demonstrated as a feasible alternative for biohydrogen production and wastewater treatment. In the present study, hydrogen production and nutrient removal from different organic carbon sources (glycerin, sucrose, glucose and organic acids, and pentose-rich liquor) by microbial consortia through biophotolysis and photofermentation in batch anaerobic bioreactors have been evaluated. Chlamydomonas sp. strains (CC425, CC4169, and CHL02) demonstrated higher hydrogen production from sucrose-enriched wastewater, 4.33 ± 0.25 mmol H 2 L−1 (CC425) and 1.02 ± 0.25 mmol H 2 L−1 (CHL02), and better organic carbon removal, 66.0 % (CC4169). Anabaena sp. (UTEX1448) yielded better nitrogen removal (average of 31.6 %) and promising results of hydrogen production from pentose-rich liquor. The results showed that the organic carbon source influenced hydrogen production due to the occurrence of different metabolic pathways by microbial consortia and that this production can be associated with the biological wastewater treatment. [Display omitted] • The organic carbon source influenced the production of hydrogen and by-products. • Different amounts of hydrogen were obtained by strains of microbial consortium. • The higher H 2 production was from sucrose-rich wastewater by Chlamydomonas reinhardtii (CC425). • The best removal of organic carbon was by Chlamydomonas reinhardtii and nitrogen by Anabaena sp. • It is possible to associate the hydrogen production with the wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fermented SO 4 2−-free vinasse and molasses methanized at 30 and 55 °C. • Substrate exchange did not impact high rate COD removal and methane production. • No organic overloads at OLR as high as 20.0 kg COD m−3 d−1 in both reactors. • CH 4 in biogas ≥ 80 % and CH 4 yield ≥ 330 NmL g−1COD in both reactors. • 50%-rise in energy recovery when adopting year-round operation of the biogas plant. Anaerobic digestion (AD) has been recently highlighted as the most efficient approach to manage vinasse in sugarcane biorefineries, providing both a renewable energy source (biogas) and a mineralized and nutrient-rich effluent suitable for agricultural use. However, the high sulfate concentrations (ca. 2 g L−1) present in vinasse and its seasonal availability (7–8 months) hinder the maximization of methane production in AD plants. This study investigated the use of sulfate-free vinasse (season) and molasses (off season), both pre-fermented in fermentative-sulfidogenic systems, as substrates to obtain enhanced year-round methane production in sugarcane biorefineries. Two second stage methanogenic structured-bed reactors operated at different temperatures (30 °C and 55 °C) were subjected to increasing organic loading rate (OLR) levels (1.0–20.0 kg COD m−3 d−1) in an experimental simulation of sequential periods of season, off season and season. An efficient start-up strategy enabled achieving operating stability in the full load project (10.0 kg COD m−3 d−1) in 37 d, which means anticipating the maximization of bioenergy production. Pre-fermenting vinasse and molasses was imperative for maintaining efficient organic matter conversion (80–90 %) into methane, regardless of the significant differences in lactate and phenols availability. A methane content in biogas ≥ 80 % and methane yield ≥ 330 NmL CH 4 g−1COD were observed in both reactors, with no apparent observation of organic overloads. The results point towards a highly efficient strategy to maintain year-round high-rate biogas production from sugarcane vinasse, although the relatively high molasses demands can trigger an internal competition (with ethanol production) for substrate. [ABSTRACT FROM AUTHOR]

This study simulated the application of the continuous multiple tube reactor (CMTR), a promising technology capable to replace fixed-film reactors in biohydrogen (bioH 2) production via dark fermentation, in the processing of sucrose-rich wastewater (COD of up to 16 g L−1). The long-term impacts on both the bioH 2 evolution and the dynamics of biomass growth and retention were assessed, aiming to identify the operating limits of the reactor. The bioH 2 production was maximized (1445 NmL H 2 L−1 d−1) when using moderately concentrated wastewaters (COD = 8 g L−1) at an OLR of 48.0 g COD L−1 d−1, with much lower hydrogenogenic activity (< 200 NmL H 2 L−1 d−1) observed at OLR levels of 72.0 and 96.0 g COD L−1 d−1. Inhibition of the fermentative activity by excess substrate and limitations in the retention capacity of suspended biomass in the reactor still limit the application of higher OLR at the current stage of the technology. Strategies stimulating the cell growth (nitrogen dosing) and biofilm formation (calcium dosing) have potential to expand the operating limit of the CMTR without requiring constructive modifications. [Display omitted] • High COD (up to 16 g L−1) was applied in the continuous multiple tube reactor (CMTR). • BioH 2 production is maximized at COD = 8.0 g L−1, regardless of the OLR. • Inhibition by substrate and poor suspended biomass retention limit using higher COD. • The CMTR seems suitable for processing nitrogen- and calcium-rich wastewaters. • The biomass retention rate peaked (196.6 mg VSS L−1 d−1) when OLR = 48 kg COD m−3 d−1. [ABSTRACT FROM AUTHOR]

Recent studies have revealed gaps related to the bed purpose in fixed-film reactors and its influence on biohydrogen (bioH 2) evolution via dark fermentation, given the pivotal role of the basal portion (i.e., feeding chamber) in converting fresh substrate and establishing bioH 2 precursor metabolic pathways, which is opposed to that observed in the bed zone. This study aimed to assess the influence of different cell immobilization arrangements (as well as its absence) on biomass retention and washout and their effects on bioH 2 evolution and metabolic profiles of an anaerobic tubular reactor (AnTR, which does not include support material), an anaerobic structured-bed reactor (AnSTBR, which includes support material laid out in an orderly pattern) and an anaerobic packed-bed reactor (AnPBR, which considers support material laid out in a disorderly pattern) operated under equivalent operating conditions in the feeding chamber. Higher bioH 2 evolution was achieved in the AnSTBR (743.25 mL-H 2 L−1 d−1) compared to the AnPBR (662.04 mL-H 2 L−1 d−1) and AnTR (586.22 mL-H 2 L−1 d−1). For the former, a massive carbohydrate-uptake occurred in the feeding chamber and at the beginning of the bed zone, both comprising an intense metabolic activity versus the upper regions. Conversely, this pattern was restricted to the AnPBR feeding chamber, while an alternative source of lactic activity occurred in the bed zone. Overall, the presence of media in the bed zone proved to be imperative to ensure suitable biomass retention in quanti-qualitative terms in opposition to no-bed, influencing biomass distribution, specific substrate conversion, bioH 2 evolution and metabolic pathways. [Display omitted] • Novel insights into biomass retention driven by media arrangement were revealed. • Lack of bed adversely affects the biohydrogen evolution and substrate conversion. • The structured bed reactor achieved the highest biohydrogen evolution. • Capnophilic lactic fermentation was identified in the packed bed reactor. • Different patterns of biomass distribution were observed along the reactors. [ABSTRACT FROM AUTHOR]

Sugarcane vinasse has been widely used as a soil fertilizer in the Brazilian sucro-alcohol industry for recycling potassium and water. However, the potential negative effects from long-term soil fertirrigation represent a major drawback regarding this practice, whereas the application of biodigestion represents an efficient method for reducing the polluting organic load and recovering bioenergy from vinasse. Regardless of the predicted use for vinasse, an understanding of the potential of each option is imperative, as the seasonal alterations in the inorganic/organic fractions of vinasse directly affect its management. In this context, this study presents a detailed compositional characterization of sugarcane vinasse from a large-scale Brazilian biorefinery throughout the 2014/2015 harvest to assess the environmental effects (due to fertirrigation) and to estimate the biogas energetic potential. Calculated inputs of organic matter into soils due to vinasse land application were equivalent to the polluting load of populations (117–257 inhab ha −1 ) at least 2-fold greater than the largest Brazilian capital cities (78–70 inhab ha −1 ). Two-phase biodigestion could efficiently reduce the polluting load of vinasse (23–52 inhab ha −1 ) and eliminate the negative effects from direct sulfide emissions in the environment. However, a high risk of soil sodification could result from using high doses of Na-based alkalizing compounds in biodigestion plants. Finally, the optimized recovery of bioenergy through biogas (13.3–26.7 MW as electricity) could supply populations as large as 305 thousand inhabitants, so that over 30% of the surplus electricity produced by the studied biorefinery could be obtained from biogas. Overall, applying biodigestion in the treatment of vinasse provides important environmental and energetic gains. However, the benefits of reducing the polluting organic load of vinasse through bioenergy recovery may lose their effect depending on the alkalizing strategy, indicating that the proper use of chemicals in full-scale biodigestion plants is imperative to attain process sustainability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acid treatment increased the zeolite hydrophobicity and specific surface area. • Size-exclusion effect prevented simvastatin degradation. • After using the catalyst 5 times (batches), 1.8% of the initial Fe content leached. • 82% (diclofenac) and 98% (ranitidine) degradation after 12 min (continuous regime) This work assesses the feasibility of coupling the heterogeneous Fenton process to biologically treated domestic sewage to remove diclofenac, ranitidine, and simvastatin (50 µg L−1 each). The catalyst was a purified natural zeolite, which was impregnated with iron (2Fe4A). First, batch tests (10 g L−1 catalyst, 2 g L−1 H 2 O 2 , and pH 7) were performed to gather information about the performance of the process. Simvastatin could not be significantly removed as its molecular dimensions were larger than the zeolite pores. Drugs removal by adsorption and mineralization were not observed. After five cycles of 30 h each, leached iron was approximately 2%, with no significant change in the drugs removal performance. Second, a fixed-bed reactor packed with 2Fe4A was placed after the exit of the biological reactor, with hydraulic retention time of 12 min. 98 and 82% of diclofenac and ranitidine, respectively, were removed, as well as 93% of the added hydrogen peroxide. The coupled system was stable for, at least, 10 days. The operating cost of the heterogeneous Fenton process combined to the biological one was estimated and, although diclofenac and ranitidine could be significantly removed in a short period of time, it was concluded that it is a relatively expensive process that has the disadvantages of high hydrogen peroxide consumption and size exclusion effects. [ABSTRACT FROM AUTHOR]

Various pharmaceutical drugs are being detected in different environmental compartments such as surface waters, groundwater, and sediment; a major concern since they are biologically active substances which can interfere with biological systems affecting the native biota. Among these drugs, antimicrobials are especially worrisome mainly due to the development of bacterial resistance. The aims of this study were to investigate if enrofloxacin, an emergent antibiotic pollutant, could be biodegraded in lake sediment, identify its break down products and to determine if these products have antimicrobial properties or are toxic. Three biodegradation products were identified and the antibiotic susceptibility assay proved that the products formed did not display antibiotic effects. Ecotoxicity testing with green algae suggested that the degradation products do not cause adverse effects statistically. However, it is suggested that further investigations are needed to identify the mechanism of degradation and the microbes involved. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A mathematical model was developed to describe sulfamethazine degradation. • The model was divided into two major stages: acids formation and consumption. • Three hypotheses for sulfamethazine degradation were considered. • A long-term quantification of the influent variations effects was developed. • 8 μg of SMZ had a similar impact on the process as 1000 mg of filtered COD. Abstract Anaerobic digestion has been investigated as a potential method for treating antibiotic-contaminated livestock wastewaters. Antibiotic removal is mainly associated with biodegradation and sludge adsorption. In environmental concentrations, i.e., from ng L−1 to a few hundred μg L−1, cometabolism is the most likely biodegradation pathway. The overall performance of anaerobic processes may be affected by the hydraulic retention time, and these processes are strongly related to the physical characteristics of the reactor and variations in influent chemical composition. The effects of these factors can be better understood using a mathematical model. Therefore, this paper aimed to develop a model to describe an anaerobic process to treat sulfamethazine (SMZ), which was divided into two stages of microorganism growth and substrate consumption. In addition, three hypotheses regarding sulfamethazine degradation, including substrate cometabolism related to both stages and an apparent enzymatic reaction, were evaluated. A long-term kinetics structure was added to the model to simulate the process of adaptation to each new operational condition. The results showed that sudden increases in chemical oxygen demand (COD) and hydraulic retention time (HRT) had the most significant negative impact on process performance. In addition, a sudden variation of 8 μg of SMZ had a similar impact on the process as did 1000 mg of filtered COD. Of the degradation hypotheses, the hypothesis related to organic acid consumption was more accurate than that related to hydrolysis; however, neither could account for the response to variations in HRT. The enzymatic approach resulted in a considerably more accurate representation of the influent flow rate variations than did the cometabolic hypotheses. [ABSTRACT FROM AUTHOR]

Hydrogen is a non-polluting source of energy, which is renewable and very abundant in the universe. Microalgae and cyanobacteria produce hydrogen by breaking down water and organic compounds. The aim of this research was to develop hydrogen production using cyanobacterium Anabaena sp. by nitrogen deprivation in two experimental phases of cultivation, optimizing its biomass from physicochemical variables. The experiment was carried out with axenic culture, in BG-11 medium, in triplicate, in two steps and under continuous illumination: in the first step, cultures were maintained in an aerobic condition until the first half of growth phase under nitrogen limitation; in the second step, the biomass was transferred, by centrifugation and cell wash, to anaerobic photobioreactors under nitrogen deprivation and the atmosphere was changed by argon for hydrogen production. Hydrogen was detected by gas chromatography and the hydrogen production parameters were tested using the Gompertz model and the volume by the general ideal gas equation. The optimization of biomass in the first step of cultivation increased its yield by 18.3% and heterocysts formation was 3.4 times higher in nitrogen privation conditions. Therefore, hydrogen production by cell increased 55.2% and the productivity 57.6% when compared to the culture of Anabaena sp. in control condition. The method and the strain were effective for hydrogen production and the pH, temperature and light intensity affected the improvement of this production and increased the biomass yield. [ABSTRACT FROM AUTHOR]

Throughout the sugarcane harvest, it is common for sulfate to accumulate in the vinasse of sugar and ethanol plants. However, little is known regarding the influence of sulfate on the anaerobic digestion (AD) of vinasse, which may lead to severe performance losses. This study assessed the influence of various COD/sulfate ratios (12.0, 10.0 and 7.5) on both COD removal and methane (CH 4 ) production from sugarcane vinasse AD. Batch assays were conducted in thermophilic conditions. At a COD/sulfate ratio of 7.5, CH 4 production was 35% lower compared with a ratio of 12.0, considering a diversion of approximately 13.6% of the electron flow to sulfidogenesis. The diversion of electrons to sulfidogenesis was negligible at COD/sulfate ratios higher than 25, considering the exponential increase in CH 4 production. Organic matter degradation was not greatly affected by sulfidogenesis, with COD removal levels higher than 80%, regardless of the initial COD/sulfate ratio. [ABSTRACT FROM AUTHOR]

Biohydrogen (bioH 2 ) production via dark fermentation is an attractive approach to overcome the drawbacks of conventional hydrogen production methods and represents a preliminary alternative for the management of organic wastes. Fundamental studies are still required to enhance the performance of bioH 2 production systems, with emphasis on the development of novel reactor configurations. The anaerobic structured-bed reactor (ASTBR) is a recently developed configuration with great potential for bioH 2 production, although operating strategies are still required to minimize biomass washout in such systems. In this context, calcium dosing has been investigated as a strategy to enhance both biomass retention and bioH 2 production rates in the ASTBR. The present study employed varying COD/calcium ratios (4423, 2079, 1357, 1012, 884, and 632) in continuous experiments under mesophilic conditions (25 °C). Calcium dosing effectively enhanced biomass retention within the ASTBR, directly increasing the availability of metabolic energy for different metabolic pathways rather than cell synthesis. An optimal COD/calcium ratio of 1360 was mathematically estimated for bioH 2 production, which is consistent with the results obtained experimentally. The specific organic loading rate (SOLR) was better controlled at this ratio, indicating the establishment of balanced conditions in terms of substrate availability and biomass concentration. Conversely, bioH 2 production was severely impaired at COD/calcium values below and above the optimal range, most likely due to enhancement of the homoacetogenic pathway as a result of unbalanced conditions in the SOLR. Furthermore, biomass accumulation did not strongly affect the mean residence time of the ASTBR, facilitating its robust and enhanced solid retention. [ABSTRACT FROM AUTHOR]

Vinasse is a residue from bioethanol production that is produced in large quantities in Brazil and Europe and is applied to fields as a source of plant nutrients (fertirrigation). A side effect of this use is greenhouse gas (GHG) emissions during storage and transport in open channels to fields, and from fertirrigated soils. This study assessed GHG emissions in experiments simulating this vinasse management system, and the potential for reducing emissions of methane (CH 4 ) and nitrous oxide (N 2 O) from vinasse via anaerobic digestion (AD) in biogas plants. During 21 days’ storage of untreated vinasse, 29% of dry matter (DM) and 40% of volatile solids (VS) were lost, which resulted in cumulative CH 4 emissions of up to 43.8 kg CO 2eq kg −1 C-vinasse. In contrast, there were no CH 4 emissions from AD-treated vinasse (digestate) during storage. GHG emission was related to the biochemical characteristics of the untreated and digested vinasse. The accumulation of oxidised nitrogen (N) compounds was up to four-fold higher in soil amended with untreated vinasse than from digestate-amended soil. The N 2 O emissions from soil amended with untreated vinasse were also higher than from soil amended with digestate, ranging from 0.173 to 0.193 kg CO 2eq m −2 in the former and from 0.045 to 0.100 kg CO 2eq m −2 in the latter. Extrapolation of the results to a Brazilian case indicated that AD treatment prior to storage/transport and field application could reduce GHG emissions from the vinasse management chain by at least 48%, with further reductions from the use of biogas in power production. [ABSTRACT FROM AUTHOR]

The kinetics of the acidogenic phase during anaerobic digestion of sugarcane vinasse in differential reactors containing immobilized cells was investigated. The maximum substrate conversion rate (r max ), substrate saturation constant (K s ) and constant of inhibition by excess substrate (K is ) were determined using vinasse with and without pH adjustment. Simulation and scaling-up of a thermophilic-hydrogen production system were performed. The r max values obtained at different pH were similar and near 0.9 mg-Total carbohydrates g-VS −1 h −1 . The K s obtained from the system without pH adjustment was 10,762.3 mg-Total carbohydrates L −1 (i.e., 2.5 times higher than the system with pH adjustment). No inhibition by excess substrate was achieved in the system without pH adjustment, indicating that sugarcane vinasse can be used to produce hydrogen without input costs. The simulation revealed that hydrogen production is a sensitive process that requires careful balancing of various operational parameters. The payback for the investment in system implementation is 4.4 years. [ABSTRACT FROM AUTHOR]

Vinasse management in biorefineries bears a burden for sugarcane industries. Despite its high potassium-related fertilizer potential, a series of negative environmental impacts is expected to occur in long-term soil applications of vinasse through fertirrigation. Conversely, a high biodegradable organic content characterizes vinasse as a potential substrate for bioresource and bioenergy recovery from numerous (bio)technological perspectives. This review presents the alternative approaches proposed for sugarcane vinasse management in Brazil, with special attention dedicated to the role of anaerobic digestion as the core conversion step. The suitability of applying phase separation, i.e., the separation of fermentation from methanogenesis in sequential reactors, is discussed in detail. Laboratory and full-scale experiences were considered to discuss the energetic potential of sugarcane vinasse through biogas generation. With a national installed capacity of up to 1603 MW, energy from vinasse could replace half of the coal-derived electricity in Brazil. Meanwhile, investing in vinasse fermentation to obtain soluble organic metabolites could provide more than 10 g L−1 of (iso)butyrate. This is the first review addressing the potential use of sugarcane vinasse in anaerobic biorefineries that discusses applications far beyond conventional biogas production, and encourages the rational use of vinasse as a raw material for bioprocesses, either in short- or long-term scenarios. [ABSTRACT FROM AUTHOR]

The organic matter bioconversion into methane during anaerobic digestion (AD) comprises different steps, the acidogenic and methanogenic phases being clearly distinct in terms of metabolic activities. In this work, new configurations of anaerobic fixed bed biofilm reactors (AFBBR) were operated under conventional methanogenic conditions (single phase – SP-AFBBR, M 1 R), and in a sequential two-phase system, acidogenic reactor followed by methanogenic reactor (TP-AFBBR, AcR + M 2 R), in order to verify the impact of the AD phase separation on the overall system performance in operational, kinetics and microbiological aspects. The results indicated that feeding the methanogenic reactor with the acidogenic effluent stream provided a shorter operating start-up period (11 and 32 days for SP and TP-AFBBR, respectively), a greater alkalinity generation (0.14 and 0.41 g-CaCO 3 ·g-COD removed −1 for M 1 R and M 2 R, respectively), and the optimization of biomethane production (methane yield of 95 and 154 N-mLCH 4 ·g-COD removed −1 for M 1 R and M 2 R, respectively). The COD removal kinetics was also favored in the TP-AFBBR (k 1-COD = 1.4 and 2.9 h−1 for M 1 R and M 2 R, respectively), since the soluble fermentation products were readily bioavailable to the biomass in the reactor. Hydrogenotrophic methanogenesis was the predominant pathway in the M 2 R, while the Methanosaeta -driven acetoclastic pathway predominated in the M 1 R. The greater diversity of Bacteria and Archaea in M 2 R denotes a better balance between the species that degrade volatile organic acids from AcR (i.e. Syntrophorhabdus , Syntrophus and Syntrophobacter) and the hydrogenotrophic methanogens (Methanoregula , Methanolinea and Methanospirillum) that consume the biodegradation products. The estimated bioenergy generation potential (range of 0.39–0.64 kWh·m−3-sewage considering the COD removed) for full-scale TP-sewage treatment plants evidences the feasibility of energetic recovery in the domestic sewage anaerobic treatment. [Display omitted] • Two-phase reactor enhances the biomethanation during sewage anaerobic digestion. • Organic matter removal kinetics was favored in the two-phase anaerobic reactor. • Acidogenic reactor shifts the methanogenic phase to the hydrogenotrophic pathway. • Lactococcus and Clostridium are the key-players in the organic acids production. • Phases separation makes it feasible the bioenergy recovery in the sewage treatment. [ABSTRACT FROM AUTHOR]

Dark fermentation of sugarcane vinasse can be used as a "cleaning" step to remove sulfate prior to methanogenesis because sulfidogenic conditions can be successfully established in parallel with biohydrogen production. Using a 22 central composite rotational design (CCRD) and response surface methodology (RSM), this study assessed the impacts of bicarbonate and sulfate availability on the establishment of sulfidogenesis in the thermophilic (55 °C) fermentation of vinasse in batch reactors, equally assessing the impacts on biohydrogen evolution. CCRD-RSM results indicated the favoring of biohydrogen production at the lowest sulfate and bicarbonate concentrations, whilst the opposite was observed for sulfidogenesis. Glycerol, lactate, and hydrogen were the preferential electron donors utilized by sulfate-reducing bacteria (SRB), whilst ethanol was markedly consumed only at high sulfate concentrations. SRB were inhibited by sodium when dosing excess NaHCO 3 and Na 2 SO 4. Complementary tests revealed maximum biohydrogen production (2.40 mmol) out of the CCRD, at pH exceeding 7.5 with no interference of sulfidogenesis. Non-efficient biohydrogen production was observed at low pH (<5.0; ∼1.90 mmol) because the uptake of lactate was inhibited. Meanwhile, homoacetogenesis was established under intermediate pH range (5.5–6.5), as revealed by the accumulation of acetate (up to 2.5 g L−1). 16S rRNA gene amplicon sequencing further revealed the genera Thermoanaerobacterium/Pseudoclostridium , Desulfotomaculum/Desulfohalotomaculum and Sporomusaceae/Moorella as the main biohydrogen-producing, sulfate-removing and biohydrogen-consuming (homoacetogens) microbial groups, respectively. Hence, using a single inoculum source, vinasse may provide a butyrate-rich (along with biohydrogen-rich biogas) or a sulfate-free and acetate-rich fermented effluent, depending mainly on proper pH control. • BioH 2 evolution (∼1.9 mmol) was limited at pH < 5.0 due to inhibited lactate uptake. • Maximum bioH 2 evolution (∼2.4 mmol) prevailed at pH > 7.5 in the absence of SO 4 2−. • Sulfidogenesis was triggered at pH > 6.0, regardless of the SO 4 2− concentration. • Only sporulating sulfate-reducing bacteria (e.g. Desulfotomaculum) were identified. • Intermediate pH (5.5–6.5) triggered bioH 2 uptake by homoacetogens (e.g. Moorella). [ABSTRACT FROM AUTHOR]

The objective of this paper was to determine the influence of sludge age on microbial fuel cell (MFC) performance for generating electricity and removing organic matter from winery wastewater. Six Solid Retention Times (SRT) were used: 1.2, 1.4, 1.8, 2.3, 3.5 and 7.0 d. Results demonstrate that the electricity generation increases by decreasing the SRT, selecting electrogenic microorganisms, once the specific organic loading rate (SOLR) increased and the competition for substrate was reduced. Decreasing the SRT, coulombic efficiency can be increased from 3.4% to almost 42.2% and maximum power density from 58 to 890 mW m −2 . However the SRT did not influence on organic matter removal in biological treatment, because only a small part of COD was removed oscillating around 600 mg L −1 d −1 and it was very similar at all SRT studied. [ABSTRACT FROM AUTHOR]

In this work, a mathematical model based on an extended Brinkman equation was used to evaluate the porosity and velocity distribution along the radial direction of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor; the model considers the fluid flow within the bed. The study was performed using two different particle geometries and three tube-to-particle diameter ratios ( D / d p ) to understand the effects of the shape and particle size on the flow velocity distribution. The results show that the oscillation in the velocity profile is dependent on the D / d p ratio, particle shape and bed porosity. Better results were obtained with irregular shapes, such as hollow cylindrical rings, and a D / d p ratio of 10. The model adapted for this study may be a suitable tool for the design and optimization of horizontal-flow anaerobic immobilized biomass reactors used in wastewater treatment processes. [ABSTRACT FROM AUTHOR]

Bio-hydrogen production from sugarcane vinasse in anaerobic up-flow packed-bed reactors (APBR) was evaluated. Four types of support materials, expanded clay (EC), charcoal (Ch), porous ceramic (PC), and low-density polyethylene (LDP) were tested as support for biomass attachment. APBR (working volume – 2.3 L) were operated in parallel at a hydraulic retention time of 24 h, an organic loading rate of 36.2 kg-COD m −3 d −1 , at 25 °C. Maximum volumetric hydrogen production values of 509.5, 404, 81.4 and 10.3 mL-H 2 d −1 L −1 reactor and maximum yields of 3.2, 2.6, 0.4 and 0.05 mol-H 2 mol −1 carbohydrates total, were observed during the monitoring of the reactors filled with LDP, EC, Ch and PC, respectively. Thus, indicating the strong influence of the support material on H 2 production. LDP was the most appropriate material for hydrogen production among the materials evaluated. 16S rRNA gene by Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis and scanning electron microscopy confirmed the selection of different microbial populations. 454-pyrosequencing performed on samples from APBR filled with LDP revealed the presence of hydrogen-producing organisms ( Clostridium and Pectinatus ), lactic acid bacteria and non-fermentative organisms. [ABSTRACT FROM AUTHOR]

Anaerobic digestion in two sequential phases, acidogenesis and methanogenesis, has been shown to be beneficial for enhancing the biomethane generation from wastewater. In this work, the application of glycerol (GOH) as a fermentation co-substrate during the wastewater treatment was evaluated on the biodegradation of different pharmaceuticals and personal care products (PPCPs). GOH co-digestion during acidogenesis led to a significant increase in the biodegradation of acetaminophen (from 78 to 89%), ciprofloxacin (from 25 to 46%), naproxen (from 73 to 86%), diclofenac (from 36 to 48%), ibuprofen (from 65 to 88%), metoprolol (from 45 to 59%), methylparaben (from 64 to 78%) and propylparaben (from 68 to 74%). The heterotrophic co-metabolism of PPCPs driven by glycerol was confirmed by the biodegradation kinetics, in which k bio (biodegradation kinetics constant) values increased from 0.18 to 2.11 to 0.27–3.60 L g−1-VSS d−1, for the operational phases without and with GOH, respectively. The assessment of metabolic pathways in each phase revealed that the prevalence of aromatic compounds degradation, metabolism of xenobiotics by cytochrome P 450 , and benzoate degradation routes during acidogenesis are key factors for the enzymatic mechanisms linked to the PPCPs co-metabolism. The phase separation of anaerobic digestion was effective in the PPCPs biodegradation, and the co-fermentation of glycerol provided an increase in the generation potential of biomethane in the system (energetic potential of 5.0 and 6.3 kJ g−1-COD removed , without and with GOH, respectively). This study showed evidence that glycerol co-fermentation can exert a synergistic effect on the PPCPs removal during anaerobic digestion mediated by heterotrophic co-metabolism. [Display omitted] • GOH co-digestion promoted a significant increase in the PPCPs biodegradation. • Aromatic compounds and benzoate degradation identified as PPCPs co-metabolic routes. • PPCPs enzymatic bioconversion driven by cytochrome P 450. • GOH fermentation boosted the biomethane production in anaerobic digestion. • PPCPs biodegradation kinetics was enhanced with the GOH addition. [ABSTRACT FROM AUTHOR]

This study evaluated the influence of a high organic loading rate (OLR) on thermophilic hydrogen production at an up-flow anaerobic packed-bed reactor (APBR) treating a residual liquid stream of a Brazilian biorefinery. The APBR, filled with low-density polyethylene, was operated at an OLR of 84.2 kg-COD m −3 d −1 . This value was determined in a previous study. The maximum values of hydrogen production and yield were 5,252.6 mL-H 2 d −1 and 3.7 mol-H 2 mol −1 total carbohydrates , respectively. However, whereas the OLR remained constant, the specific organic load rate (sOLR) decreased throughout operation from 1.38 to 0.72 g-Total carbohydrates g-VS −1 h −1 , this decrease negatively affected hydrogen production. A sOLR of 0.98 g-Total carbohydrates g-VS −1 h −1 was optimal for hydrogen production. The microbial community was studied using 454-pyrosequencing analysis. Organisms belonging to the genera Caloramator , Clostridium, Megasphaera , Oxobacter , Thermoanaerobacterium , and Thermohydrogenium were detected in samples taken from the reactor at operation days 30 and 60, suggesting that these organisms contribute to hydrogen production. [ABSTRACT FROM AUTHOR]

Abstract: This study evaluated the use of two types of substrates, glucose and sucrose, feeding an anaerobic fixed-bed bioreactor. The biogas produced was composed of H2 and CO2, without methane. Maximum hydrogen yields were 3.22 mol H2 mol−1 sucroseconverted and 1.51 mol H2 mol−1 glucoseconverted. The main intermediates were acetic acid, butyric acid, and ethanol. The greatest difference, however, was in the stability of the process. The operation of the reactor with sucrose exhibited a drop in biogas production, whereas operation with glucose was stable after a slight decrease in biogas production. This decrease may have been caused by the differential growth of microbial populations in each reactor, namely, the growth of organisms that use the Wood–Ljungdahl metabolic pathway. [Copyright &y& Elsevier]

Abstract: Degradation of formaldehyde by Ralstonia eutropha was studied in a batch bioreactor operated in recycling mode (30 °C, initial pH of 6.5, aeration rate 0.5 vvm, and a recycling flow rate of 6 mL min−1). Growth kinetics equations were described using four substrate inhibition models, and the initial formaldehyde concentration ranged from 54.5 to 993.0 mg L−1. In each case, model parameters were estimated interactively using nonlinear regression analysis and on the basis of the goodness of fit, the fitness of the model to the experimental data was obtained (i.e., the coefficient of determination and the percent of standard deviation). The estimated parameters according to the Luong equation were μ max = 0.101 h−1, K S = 54.1 mg L−1, S m = 1329 mg L−1, and n = 2.07. According to the maintenance energies explained by Pirt, cell maintenance was quantified with q = Aμ + B; where A and B are the associated and non-associated growth parts of substrate consumption, respectively. The importance of these terms was verified using the developed models, which would efficiently describe the dynamic nature of growth and formaldehyde biodegradation. [Copyright &y& Elsevier]

This is the first study to bring evidence on the anaerobic biodegradation of TBBPA occurring during acidogenesis in domestic sewage at environmentally relevant concentrations by complex microbial communities. This was accomplished by continuously operating two anaerobic structured bed reactors (ASTBR) for over 100 days under acidogenic (Acidogenic Reactor, AR) and multistep methanogenic (Methanogenic Reactor, MR) conditions. In the AR, the temporal carbohydrates consumption and the acetic acid production were strongly correlated with TBBPA removal by the Pearson's test. The spatial concentration of TBBPA and carbohydrates along the MR and the kinetic degradation profiles corroborate the AR results. It is hypothesized that TBBPA biodegradation in the studied conditions occurs during acidogenesis via the cometabolism supported by non-specific enzymes and the metabolism (dehalorespiration) established by electrons donors such as H 2 , which are both produced during the macrocomponents breakdown in the early stages of the anaerobic digestion. The TBBPA mass balance showed that approximately 86.8 ± 0.05% and 97 ± 0.01% of the removed TBBPA was biodegraded in the AR and MR, respectively. Furthermore, TBBPA biodegradation went further than reductive debromination as total phenols were detected in the reactors' effluent. • ASTBR reactors were effective in removing TBPPA from domestic sewage. • TBBPA biodegradation in environmentally relevant concentrations is linked to acidogenesis. • TBBPA removal depends on the metabolism of the macrocomponents of the sewage. • TBBPA adsorption to anaerobic sludge was negligible compared to its degradation. [ABSTRACT FROM AUTHOR]

Improving anaerobic digestion of sugarcane vinasse – a high-strength wastewater from ethanol distillation – is a subject of great interest, in view of the reduction of the pollutants and recovery of methane and valuable metabolites as byproducts. Through metatranscriptomic analysis, this study evaluated the active microbiome and metabolic pathways in a continuous acidogenic reactor: Stage 1S (control): 100% sucrose-based substrate (SBS); Stage 2SV (acclimation): 50% SBS and 50% vinasse; Stage 3V: 100% vinasse. Metatranscriptome obtained from each Stage was subjected to taxonomic and functional annotations. Under SBS feeding, pH dropped to pH 2.7 and biohydrogen production was observed. As vinasse was added, pH increased to 4.1–4.5, resulting in community structure and metabolite changes. In Stage 3V, biohydrogen production ceased, and propionate and acetate prevailed among the volatile fatty acids. Release of homoacetogenesis enzymes by Clostridium ljungdahlii and of uptake hydrogenase (EC 1.12.99.6) by Pectinatus frisingensis were linked to hydrogen consumption in Stages 2SV and 3V. Metabolic pathways of vinasse compounds, such as carbohydrates, malate, oxalate, glycerol, sulfate and phenol, were investigated in detail. In pyruvate metabolism, gene transcripts of oad A (oxaloacetate decarboxylase) and mdh (malate dehydrogenase), were upregulated in Stage 3V, being mostly attributed to P. frisingensis. Acetate formation from vinasse degradation was mainly attributed to Megasphaera and Clostridium , and propionate formation to P. frisingensis. Glycerol removal from vinasse exceeded 99%, and gene transcripts encoding for glp F (glycerol uptake facilitator protein), glp K (glycerol kinase) and glp ABC (glycerol-3-phosphate dehydrogenase) were expressed mostly by Pectinatus and Prevotella. mRNA profiling showed that active bacteria and gene expression greatly changed when vinasse replaced sucrose, and Pectinatus was the main active bacterium degrading the searched compounds from vinasse. The identification of the main metabolic routes and the associated microorganisms achieved in this work contributes with valuable information to support further optimization of fermentation towards the desired metabolites. [Display omitted] • A continuous acidogenic bioreactor was fed with sucrose followed by vinasse. • mRNA profiling revealed microbial functions and metabolic pathways in each stage. • Bacteria involved in biohydrogen production and consumption were unveiled. • Pectinatus frisingiensis was the most active microorganism under vinasse feeding. • Specific metabolic routes of vinasse compounds degradation were reconstructed. [ABSTRACT FROM AUTHOR]

A modeling study was completed to develop a methodology that combines the sequencing and finite difference methods for the simulation of a heterogeneous model of a tubular reactor applied in the treatment of wastewater. The system included a liquid phase (convection-diffusion-transport) and a solid phase (diffusion reaction) that was obtained by completing a mass balance in the reactor and in the particle, respectively. The model was solved using a pilot-scale horizontal-flow anaerobic immobilized biomass (HAIB) reactor to treat domestic sewage, with the concentration results compared with the experimental data. A comparison of the behavior of the liquid phase concentration profile and the experimental results indicated that both the numerical methods offer a good description of the behavior of the concentration along the reactor. The advantage of the sequencing method over the finite difference method is that it is easier to apply and requires less computational time to model the dynamic simulation of outlet response of HAIB. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results from 92cycles of an anaerobic sequencing batch biofilm reactor containing biomass immobilized on inert support (mineral coal) applied for the treatment of an industrial wastewater containing high sulfate concentration. The pilot-scale reactor, with a total volume of 1.2m3, was operated at sulfate loading rates ranging from 0.15 to 1.90kgSO4 2−/cycle (48h — cycle) corresponding to sulfate concentrations of 0.25 to 3.0gSO4 2− l−1. Domestic sewage and ethanol were utilized as electron donors for sulfate reduction. Influent sulfate concentrations were increased in order to evaluate the minimum COD/sulfate ratio at which high reactor performance could be maintained. The mean sulfate removal efficiency remained between the range of 88 to 92% at several sulfate concentrations. Temporal profiles along the 48h cycles were carried out under stable operation at sulfate concentrations of 1.0, 2.0 and 3.0gSO4 2− l−1. Sulfate removal reached 99% for cycle times of 15, 25, and 30h, and the effluents sulfate concentrations were lower than 8mgSO4 2− l−1. The results demonstrate the potential applicability of the anaerobic configuration for the biological treatment of sulfate-rich wastewaters. [Copyright &y& Elsevier]

The objective of this study was to estimate the first-order intrinsic kinetic constant (k1) and the liquid-phase mass transfer coefficient (kc) in a bench-scale anaerobic sequencing batch biofilm reactor (ASBBR) fed with glucose. A dynamic heterogeneous mathematical model, considering two phases (liquid and solid), was developed through mass balances in the liquid and solid phases. The model was adjusted to experimental data obtained from the ASBBR applied for the treatment of glucose-based synthetic wastewater with approximately 500 mg L-1 of glucose, operating in 8 h batch cycles, at 30 °C and 300 rpm. The values of the parameters obtained were 0.8911 min-1 for k1 and 0.7644 cm min-1 for kc. The model was validated utilizing the estimated parameters with data obtained from the ASBBR operating in 3 h batch cycles, with a good representation of the experimental behavior. The solid-phase mass transfer flux was found to be the limiting step of the overall glucose conversion rate. [ABSTRACT FROM AUTHOR]

Abstract: The comparative performance of three pilot-scale anaerobic sequencing batch reactors treating domestic sewage from the University of Sao Paulo (Sao Carlos City, Brazil) was evaluated. Physical, chemical and physicochemical variables were accessed in the influent and in the effluent for performance evaluation. The three ASBR reactor with 1.2 m3 (total volume) each had different geometric characteristics (ratio L-length/D-diameter) and mixing type (mechanical mixer or liquor recirculation) and were designed for the treatment of 1.95 m3.d−1 of domestic sewage. The reactors were operated at 8-h sequential batch cycles during 70 days (loading rate: 0.6–1.2 kgCOD.m−3.d−1) and inoculated with anaerobic granular sludge. The two ASBR (ASBR1 and ASBR3) reactors operated under mixed liquor recirculation showed non-satisfactory results, attaining mean values of COD and TSS removals efficiencies of 40% and 65%, respectively. The mean effluent values were of 320 mgCOD l −1 and 85 mgTSS l −1. The ASBR2 operated under mechanical mixing showed better results with average removal efficiencies of 60% and 80% for COD and TSS, respectively. The mean values of effluent COD and TSS were 215 mg l −1 and 50 mg l −1, respectively. [Copyright &y& Elsevier]