ABSTRACT This study examined the ability of two biochars converted from anaerobically digested bi... more ABSTRACT This study examined the ability of two biochars converted from anaerobically digested biomass to sorb heavy metals using a range of laboratory sorption and characterization experiments. Initial evaluation of DAWC (digested dairy waste biochar) and DWSBC (digested whole sugar beet biochar) showed that both biochars were effective in removing a mixture of four heavy metals (Pb(2 +), Cu(2+), Ni(2+), and Cd(2+)) from aqueous solutions. Compared to DAWC, DWSBC demonstrated a better ability to remove Ni and Cd. Further investigations of lead sorption by the two biochars indicated that the removal was mainly through a surface precipitation mechanism, which was confirmed by batch sorption experiments, mathematical modeling, and examinations of lead-laden biochars samples using SEM-EDS, XRD, and FTIR. The lead sorption capacity of the two biochars was close to or higher than 200mmol/kg, which is comparable to that of commercial activated carbons.
The aim of this study is to evaluate the integration of microbial electrochemical technologies (M... more The aim of this study is to evaluate the integration of microbial electrochemical technologies (MET) with anaerobic digestion (AD) to overcome AD limitations caused by propionate accumulation. The study focuses on understanding to what extent the inoculum impacts on the behaviour of the integrated systems (AD-MET) from the perspective of propionate degradation, methane production and microbial population dynamics. Three different inocula were used: two from environmental sources (anaerobic sludge and river sediment) and another one from a pre-enriched electroactive consortium adapted to propionate degradation. Contrary to expectations, the reactor inoculated with the pre-enriched consortium was not able to maintain its initial good performance in the long run, and the bioelectrochemical activity collapsed after three months of operation. In contrast, the reactor inoculated with anaerobic sludge, although it required a relatively longer time to produce any observable current, was able to maintain the electrogenic activity operation (0.8 A.m-2) as well as the positive contribution of AD-MET integration to tackle propionate accumulation and to enhance methane yield (338 mL.gCOD-1). However, it must also be highlighted that from a purely energetic point of view the AD-MET was not favorable.
The concentration of solids in secondary sludge before anaerobic digestion in a wastewater treatm... more The concentration of solids in secondary sludge before anaerobic digestion in a wastewater treatment plant, bring about the production of a return flow, which contains high concentrations of all the common pollutant parameters. This return flow could unfavourably affect the performance of the processes and effluent quality of the waterline. Here, we report the utilisation of three similar microbial electrolysis cells reactors that performs simultaneous carbon and nitrogen removal to reduce the impact of the return flow in the plant. The result of the batch-fed (72 h) experiment showed COD and total nitrogen removal efficiencies that reached 90% and 80%, respectively, supporting the premise that return flows are suitable substrates for a bioelectrochemical treatment. The three reactors followed similar trends, showing good replicability and confirming the potential of MECs as a feasible technology for return flow treatment. Furthermore, when cathodic conversion efficiency was higher than 80%, the pure hydrogen production allows to recover the electric energy consumption, indicating that the system could be theoretically energy neutral.
Journal of Bioscience and Bioengineering, Dec 1, 2018
This study aims to characterize the performance of a 150 L bioelectrochemical system-based plant,... more This study aims to characterize the performance of a 150 L bioelectrochemical system-based plant, during the simultaneous carbon and nitrogen removal from several waste streams of wastewater treatment plants. The bioelectrochemical system (BES) contained five electrode pairs (operated hydraulically and electrically in parallel) and was fed with either wastewater, centrate (nutrient-rich liquid stream produced during the dewatering of digested biomass), or a mixture of both over 63 days, with a hydraulic retention time of one day. Total organic carbon and total nitrogen removal rates averaged 80% and 70%, respectively, with a specific energy consumption of 0.18 kWh$m L3 (BES D ancillary equipment). This work also underlines the challenges of using BES for nitrogen removal, highlighting the limitations of the current design, and suggesting some strategies for improvement.
International Journal of Hydrogen Energy, Jun 1, 2019
First large-scale experiences of bioelectrochemical systems (BES) are underway. However, there is... more First large-scale experiences of bioelectrochemical systems (BES) are underway. However, there is still little knowledge on how the different elements that integrate a BES behave in near real-life conditions. This paper aims at assessing the impact of long-term operation on the cation exchange membrane and on the anodic biofilm of two 16 L Microbial Electrolysis Cells (MEC) designed for hydrogen production and ammonia recovery from pig slurry. Membrane deterioration was examined by physical, chemical and microscopy techniques at different locations, revealing a strong attachment of microorganisms and a significant decay in membrane properties such as ion exchange capacity and thermal stability. Anode microbial communities did not show a dramatic shift in the eubacteria composition at different sampling areas, although the relative abundance of some bacterial groups showed a clear vertical stratification. After 100 days of continuous operation, MEC performance did not declined significantly maintaining ammonium transport rates and H 2 production rates of 15.3 gN d À1 m À2 and 0.2 LH 2 $L À1 reactor $d À1 respectively.
Microbial electrolysis cells (MECs) have great potential as a technology for wastewater treatment... more Microbial electrolysis cells (MECs) have great potential as a technology for wastewater treatment in parallel to energy production. In this study we explore the feasibility of using a low-cost, membraneless MEC for domestic wastewater treatment and methane production in both batch and continuous modes. Low-strength wastewater can be successfully treated by means of an MEC, obtaining significant amounts of methane. The results also suggest that hydrogenotrophic methanogenesis reduce the incidence of homoacetogenic activity, thus improving the overall MEC performance. However, gas production rates are low and important aspects such as methane solubility in water still remain a challenge. Overall, MECs can offer competitive advantages not only for low-strength wastewater treatment but also as an aid to anaerobic methane production by improving the chemical oxygen demand (COD) removal and methane production rates.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The amounts of slurry and manure produced each year are steadily rising as a result of an increas... more The amounts of slurry and manure produced each year are steadily rising as a result of an increasing demand for livestock products, which are expected to almost double by 2050 [1]. This two byproducts of farm-activity are commonly used as a fertilizer for crops production. However, their direct disposal may also overcome soils capacity to absorb nutrients in some areas [2], thus giving to rise to health and environmental issues. This demands the use of feasible and efficient waste management technologies that help to limit the impact of these wastes.
El desarrollo de celdas microbianas para la recuperación de nutrientes es un paso crucial para la... more El desarrollo de celdas microbianas para la recuperación de nutrientes es un paso crucial para la implementación de esta tecnología en el tratamiento de residuos orgánicos líquidos. En el presente trabajo se describen los resultados preliminares obtenidos durante la caracterización de un electrolizador biocatalíticos de 16 L, diseñado para el tratamiento de purines y recuperación de nitrógeno. El reactor fue alimentado con residuos de una granja de ganado porcino diluidos a diferentes concentraciones. Los resultados muestran que tras un periodo de aclimatación de 15-20 días es posible obtener recuperaciones máximas del 57 % del nitrógeno total presente en el residuo inicial.
Abstract Carbon dioxide (CO2) valorization for the production of different commodity chemicals is... more Abstract Carbon dioxide (CO2) valorization for the production of different commodity chemicals is a highly desired approach to moderate CO2 emissions into the atmosphere. The versatility of microbial electrochemical technologies makes it possible to use them for carbon capture and utilization. This is mainly achieved through two novel processes, namely: microbial electrosynthesis and electro-fermentation. These processes allow CO2 conversion (and some of its organic derivatives) into a wide variety of valuable products such as carboxylic acids and alcohols by means of an external electrical input. This chapter focuses on different aspects of these bioelectrochemical CO2 valorization approaches and reviews their key challenges and future perspectives from a technological and economical point of view.
Most biogas plants in the world run under psychrophilic conditions and are operated by small and ... more Most biogas plants in the world run under psychrophilic conditions and are operated by small and medium farmers. There is a gap of knowledge on the performance of these systems after several years of operation. The aim of this research is to provide a complete evaluation of a psychrophilic, low-cost, tubular digester operated for eight years. The thermal performance was monitored for 50 days, and parameters such as pH, total volatile fatty acid (tVFA), chemical oxygen demand (COD) and volatile solids (VS) were measured every week for the influent and effluent. The digester operated at a stabilized slurry temperature of around 17.7 °C, with a mean organic load rate (OLR) equal to 0.52 kg VS/m3digester *d and an estimated hydraulic retention time (HRT) of 25 days. The VS reduction in the digester was around 77.58% and the COD reduction was 67 ± 3%, with a mean value for the effluent of 3.31 ± 1.20 g COD/Lt, while the tVFA decreased by 83.6 ± 15.5% and the presence of coliforms decreas...
Two microbial electrolysis cells (MEC-1 and 2) under 30 °C and 17±3 °C temperatures, respectively... more Two microbial electrolysis cells (MEC-1 and 2) under 30 °C and 17±3 °C temperatures, respectively were operated using simulated landfill leachate as substrate. The system achieved a projected current density of 10001200 mA m-2 (MEC-1) and 530755 mA m-2 (MEC-2) coupled with low cost hydrogen production rate of 0.148 L La-1 d-1 (MEC-1) and 0.04 L La-1 d-1 (MEC-2) at an applied voltage of 1.0 V. Current generation led to a maximum COD oxidation of 73±8% (MEC-1) and 65±7% (MEC-2) with ≥100% energy recovery. The system also exhibited a high hydrogen recovery (66-95%), pure hydrogen yield (98%) and tremendous working stability during two months of operation. Electroactive microbes such as Pseudomonadaceae, Geobacteraceae and Comamonadaceae were found in anodophilic biofim, along with Rhodospirillaceae and Rhodocyclaceae, which could be involved in hydrogen production. These results demonstrated an energy-efficient approach for hydrogen production coupled with pollutants removal.
ABSTRACT This study examined the ability of two biochars converted from anaerobically digested bi... more ABSTRACT This study examined the ability of two biochars converted from anaerobically digested biomass to sorb heavy metals using a range of laboratory sorption and characterization experiments. Initial evaluation of DAWC (digested dairy waste biochar) and DWSBC (digested whole sugar beet biochar) showed that both biochars were effective in removing a mixture of four heavy metals (Pb(2 +), Cu(2+), Ni(2+), and Cd(2+)) from aqueous solutions. Compared to DAWC, DWSBC demonstrated a better ability to remove Ni and Cd. Further investigations of lead sorption by the two biochars indicated that the removal was mainly through a surface precipitation mechanism, which was confirmed by batch sorption experiments, mathematical modeling, and examinations of lead-laden biochars samples using SEM-EDS, XRD, and FTIR. The lead sorption capacity of the two biochars was close to or higher than 200mmol/kg, which is comparable to that of commercial activated carbons.
The aim of this study is to evaluate the integration of microbial electrochemical technologies (M... more The aim of this study is to evaluate the integration of microbial electrochemical technologies (MET) with anaerobic digestion (AD) to overcome AD limitations caused by propionate accumulation. The study focuses on understanding to what extent the inoculum impacts on the behaviour of the integrated systems (AD-MET) from the perspective of propionate degradation, methane production and microbial population dynamics. Three different inocula were used: two from environmental sources (anaerobic sludge and river sediment) and another one from a pre-enriched electroactive consortium adapted to propionate degradation. Contrary to expectations, the reactor inoculated with the pre-enriched consortium was not able to maintain its initial good performance in the long run, and the bioelectrochemical activity collapsed after three months of operation. In contrast, the reactor inoculated with anaerobic sludge, although it required a relatively longer time to produce any observable current, was able to maintain the electrogenic activity operation (0.8 A.m-2) as well as the positive contribution of AD-MET integration to tackle propionate accumulation and to enhance methane yield (338 mL.gCOD-1). However, it must also be highlighted that from a purely energetic point of view the AD-MET was not favorable.
The concentration of solids in secondary sludge before anaerobic digestion in a wastewater treatm... more The concentration of solids in secondary sludge before anaerobic digestion in a wastewater treatment plant, bring about the production of a return flow, which contains high concentrations of all the common pollutant parameters. This return flow could unfavourably affect the performance of the processes and effluent quality of the waterline. Here, we report the utilisation of three similar microbial electrolysis cells reactors that performs simultaneous carbon and nitrogen removal to reduce the impact of the return flow in the plant. The result of the batch-fed (72 h) experiment showed COD and total nitrogen removal efficiencies that reached 90% and 80%, respectively, supporting the premise that return flows are suitable substrates for a bioelectrochemical treatment. The three reactors followed similar trends, showing good replicability and confirming the potential of MECs as a feasible technology for return flow treatment. Furthermore, when cathodic conversion efficiency was higher than 80%, the pure hydrogen production allows to recover the electric energy consumption, indicating that the system could be theoretically energy neutral.
Journal of Bioscience and Bioengineering, Dec 1, 2018
This study aims to characterize the performance of a 150 L bioelectrochemical system-based plant,... more This study aims to characterize the performance of a 150 L bioelectrochemical system-based plant, during the simultaneous carbon and nitrogen removal from several waste streams of wastewater treatment plants. The bioelectrochemical system (BES) contained five electrode pairs (operated hydraulically and electrically in parallel) and was fed with either wastewater, centrate (nutrient-rich liquid stream produced during the dewatering of digested biomass), or a mixture of both over 63 days, with a hydraulic retention time of one day. Total organic carbon and total nitrogen removal rates averaged 80% and 70%, respectively, with a specific energy consumption of 0.18 kWh$m L3 (BES D ancillary equipment). This work also underlines the challenges of using BES for nitrogen removal, highlighting the limitations of the current design, and suggesting some strategies for improvement.
International Journal of Hydrogen Energy, Jun 1, 2019
First large-scale experiences of bioelectrochemical systems (BES) are underway. However, there is... more First large-scale experiences of bioelectrochemical systems (BES) are underway. However, there is still little knowledge on how the different elements that integrate a BES behave in near real-life conditions. This paper aims at assessing the impact of long-term operation on the cation exchange membrane and on the anodic biofilm of two 16 L Microbial Electrolysis Cells (MEC) designed for hydrogen production and ammonia recovery from pig slurry. Membrane deterioration was examined by physical, chemical and microscopy techniques at different locations, revealing a strong attachment of microorganisms and a significant decay in membrane properties such as ion exchange capacity and thermal stability. Anode microbial communities did not show a dramatic shift in the eubacteria composition at different sampling areas, although the relative abundance of some bacterial groups showed a clear vertical stratification. After 100 days of continuous operation, MEC performance did not declined significantly maintaining ammonium transport rates and H 2 production rates of 15.3 gN d À1 m À2 and 0.2 LH 2 $L À1 reactor $d À1 respectively.
Microbial electrolysis cells (MECs) have great potential as a technology for wastewater treatment... more Microbial electrolysis cells (MECs) have great potential as a technology for wastewater treatment in parallel to energy production. In this study we explore the feasibility of using a low-cost, membraneless MEC for domestic wastewater treatment and methane production in both batch and continuous modes. Low-strength wastewater can be successfully treated by means of an MEC, obtaining significant amounts of methane. The results also suggest that hydrogenotrophic methanogenesis reduce the incidence of homoacetogenic activity, thus improving the overall MEC performance. However, gas production rates are low and important aspects such as methane solubility in water still remain a challenge. Overall, MECs can offer competitive advantages not only for low-strength wastewater treatment but also as an aid to anaerobic methane production by improving the chemical oxygen demand (COD) removal and methane production rates.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The amounts of slurry and manure produced each year are steadily rising as a result of an increas... more The amounts of slurry and manure produced each year are steadily rising as a result of an increasing demand for livestock products, which are expected to almost double by 2050 [1]. This two byproducts of farm-activity are commonly used as a fertilizer for crops production. However, their direct disposal may also overcome soils capacity to absorb nutrients in some areas [2], thus giving to rise to health and environmental issues. This demands the use of feasible and efficient waste management technologies that help to limit the impact of these wastes.
El desarrollo de celdas microbianas para la recuperación de nutrientes es un paso crucial para la... more El desarrollo de celdas microbianas para la recuperación de nutrientes es un paso crucial para la implementación de esta tecnología en el tratamiento de residuos orgánicos líquidos. En el presente trabajo se describen los resultados preliminares obtenidos durante la caracterización de un electrolizador biocatalíticos de 16 L, diseñado para el tratamiento de purines y recuperación de nitrógeno. El reactor fue alimentado con residuos de una granja de ganado porcino diluidos a diferentes concentraciones. Los resultados muestran que tras un periodo de aclimatación de 15-20 días es posible obtener recuperaciones máximas del 57 % del nitrógeno total presente en el residuo inicial.
Abstract Carbon dioxide (CO2) valorization for the production of different commodity chemicals is... more Abstract Carbon dioxide (CO2) valorization for the production of different commodity chemicals is a highly desired approach to moderate CO2 emissions into the atmosphere. The versatility of microbial electrochemical technologies makes it possible to use them for carbon capture and utilization. This is mainly achieved through two novel processes, namely: microbial electrosynthesis and electro-fermentation. These processes allow CO2 conversion (and some of its organic derivatives) into a wide variety of valuable products such as carboxylic acids and alcohols by means of an external electrical input. This chapter focuses on different aspects of these bioelectrochemical CO2 valorization approaches and reviews their key challenges and future perspectives from a technological and economical point of view.
Most biogas plants in the world run under psychrophilic conditions and are operated by small and ... more Most biogas plants in the world run under psychrophilic conditions and are operated by small and medium farmers. There is a gap of knowledge on the performance of these systems after several years of operation. The aim of this research is to provide a complete evaluation of a psychrophilic, low-cost, tubular digester operated for eight years. The thermal performance was monitored for 50 days, and parameters such as pH, total volatile fatty acid (tVFA), chemical oxygen demand (COD) and volatile solids (VS) were measured every week for the influent and effluent. The digester operated at a stabilized slurry temperature of around 17.7 °C, with a mean organic load rate (OLR) equal to 0.52 kg VS/m3digester *d and an estimated hydraulic retention time (HRT) of 25 days. The VS reduction in the digester was around 77.58% and the COD reduction was 67 ± 3%, with a mean value for the effluent of 3.31 ± 1.20 g COD/Lt, while the tVFA decreased by 83.6 ± 15.5% and the presence of coliforms decreas...
Two microbial electrolysis cells (MEC-1 and 2) under 30 °C and 17±3 °C temperatures, respectively... more Two microbial electrolysis cells (MEC-1 and 2) under 30 °C and 17±3 °C temperatures, respectively were operated using simulated landfill leachate as substrate. The system achieved a projected current density of 10001200 mA m-2 (MEC-1) and 530755 mA m-2 (MEC-2) coupled with low cost hydrogen production rate of 0.148 L La-1 d-1 (MEC-1) and 0.04 L La-1 d-1 (MEC-2) at an applied voltage of 1.0 V. Current generation led to a maximum COD oxidation of 73±8% (MEC-1) and 65±7% (MEC-2) with ≥100% energy recovery. The system also exhibited a high hydrogen recovery (66-95%), pure hydrogen yield (98%) and tremendous working stability during two months of operation. Electroactive microbes such as Pseudomonadaceae, Geobacteraceae and Comamonadaceae were found in anodophilic biofim, along with Rhodospirillaceae and Rhodocyclaceae, which could be involved in hydrogen production. These results demonstrated an energy-efficient approach for hydrogen production coupled with pollutants removal.
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