Nutrient recovery and improvement of anaerobic digestion process by low grade magnesium oxide application

[spa] Diferentes esfuerzos han sido desarrollados para reducir la inhibición por nitrógeno amoniacal en la DA. Entre ellos, la adición de materiales con capacidad de intercambio catiónico (por ejemplo: bentonita, glauconita, fosforita y zeolitas) o materias con capacidad de adsorción (ej. arena, óxidos de magnesio, sepiolitas y zeolitas) han mostrado buenos resultados. Igualmente, en años recientes la posibilidad de acoplar la DA y la precipitación de estruvita (MgNH4PO4·6H2O) en el mismo reactor han llamado la atención. La precipitación de estruvita ocurre de manera natural cuando la concentración de 2+ + 3- Mg , NH4 y PO4 excede el producto de solubilidad de la estruvita. Con lo cual, la precipitación de estruvita en muchos sistemas de DA requiere la adición de compuestos 2+ 3- + químicos, ya que la concentración de Mg y PO4 es típicamente inferior a la del NH4 . El objetivo de este estudio es comparar el desempeño de cinco diferentes fuentes de magnesio (ej. MgCl2, Mg(OH)2, HG-MgO, LG-MgO y SA) en reactores, simultaneando los procesos de la DA y la precipitación de estruvita dentro del mismo reactor. La adición de agente estabilizante al purín de cerdo presento una máxima eficiencia de remoción de nitrógeno amoniacal total del 80%. La operación de los -1 digestores mostró que la adición de agente estabilizante de 5 y 30 g L al digestor resulta en un incremento del 25 y 40% en la producción de metano, respectivamente, comparado con el reactor de referencia. Este resultado puede estar relacionado con la reducción de la concentración de amonio y el incremento de la concentración de magnesio y concentración de partículas en el medio de digestión. Adicionalmente, los resultados de alcalinidad y ácidos grasos volátiles muestran que la adición de agente estabilizante no presenta un efecto negativo en los microorganismos anaeróbicos.[eng] Anaerobic digestion is a worldwide technology to treat organic waste streams, primarily due to its capacity to produce methane as renewable energy. However, there is an increasing interest on nutrient recovery (N and P), which from both environmental and economic reasons have been identified as key feature in anaerobic digestion plants. Controlled struvite formation has been attracting increasing attention as a near mature technology to recover nutrients from anaerobic digestion. However, struvite feasibility is generally limited by the high cost of chemical reagents. Because the economic feasibility of struvite is heavily influenced by reagent cost, several authors have trialled lower-cost magnesium sources. Studies to date on struvite precipitation with MgO have largely focused on the aqueous phase, with little attention given to the preceeding MgO dissolution. However, the observations noted above suggest that there may be opportunity to better understand, intervene and improve dissolution and access to MgO. The present study uses experiments and chemistry modelling to evaluate and better understand TAN removal from pig manure using MgO. Tests were performed with four industrial magnesium oxide (MgO) from natural magnesite calcination: a commercial high grade MgO (HGMgO) as well as a number of low-grade MgO (LGMgOs) by-products. All these MgO reagents were also pre-treated with phosphoric acid and tested separately after pre-treatment. The study focussed on the underlying chemistry to show how reactivity and dissolution of the various magnesium by-products influenced struvite precipitation and TAN removal performance. Moreover, another option to minimise struvite precipitation cost is to combine struvite precipitation and AD in the same reactor. Several authors have studied the addition of magnesium reagents (MgCl2 and Mg(OH)2) to precipitate struvite during anaerobic digestion, causing in some cases inhibition by pH or cation toxicity. However, to our knowledge, no references bave been found evaluating the utilization of magnesium by- products within the reactor to precipitate struvite during anaerobic digestion. In this study struvite precipitation and pig manure anaerobic digestion were coupled in the same reactor in order to mitigate the inhibitory effect of free ammonia and avoid precipitator costs. The stabilizing agent used to facilitate struvite precipitation was formulated with low-grade magnesium oxide by-product; an approach that would notably reduce struvite processing costs. Therefore, the feasibility of coupling anaerobic digestion and struvite precipitation in the same reactor was evaluated to enhance manure anaerobic digestion methane yields through ammonia inhibition mitigation. Five different magnesium sources were tested as struvite (ammonia sequestration agent) precursor, i.e. MgCl2, Mg(OH)2, two industrial by-products rich in MgO but with different reactivity, and a stabilizing agent. The latter was formulated in advance with the low reactivity industrial by-product and phosphoric acid. The effect of each magnesium source on anaerobic digestion as well as its struvite precipitation capacity was evaluated through a series biomethane potential test. However, a long term anaerobic digester operation was required to assess the feasibility of the process and to ensure that the stabilizing agent does not introduce any harmful compound for the anaerobic biomass. In this vein, the -3 addition of 5 and 30 kg m of the stabilizing agent in a pig manure continuous digester 3 -1 3 -1 resulted in a 25% (0.17 m kg ) and a 40% (0.19 m kg ) increase in methane production per mass of volatile solid, respectively, when compared with the reference digester (0.13 3 -1 m kg ). Moreover, the stability of the process during four hydraulic retention times guarantees that the stabilizing agent did not exert a negative effect on the consortium of microorganisms

Development of a modified plug-flow anaerobic digester for biogas production from animal manures

Traditional plug-flow anaerobic reactors (PFRs) are characterized by lacking a mixing system and operating at high total solid concentrations, which limits their applicability for several kinds of manures. This paper studies the performance of a novel modified PFR for the treatment of pig manure, characterized by having an internal sludge mixing system by biogas recirculation in the range of 0.270–0.336 m3 m−3 h−1. The influence on the methane yield of four operating parameters (recirculation rate, hydraulic retention time, organic loading rate, and total solids) was evaluated by running four modified PFRs at the pilot scale in mesophilic conditions. While the previous biodegradability of organic matter by biochemical methane potential tests were between 31% and 47% with a methane yield between 125 and 184 LCH4 kgVS−1, the PFRs showed a suitable performance with organic matter degradation between 25% and 51% and a methane yield of up to 374 LCH4 kgVS−1. Operational problems such as solid stratification, foaming, or scum generation were avoided.info:eu-repo/semantics/publishedVersio

Tecnologias de recuperação de nutrientes para os sistemas de digestão anaeróbia: revisão

Anaerobic digestion is a worldwide technology to treat organic waste streams, primarily due to its capacity to produce methane as renewable energy. However, there is an increasing interest on nutrient recovery (N and P), which from both environmental and economic reasons have been identified as key feature in anaerobic digestion plants. The manuscript presents a comprehensive overview on recent advances in nutrient recovery technologies applicable for anaerobic digestion systems. The review focus on N and P recovery through the use of digestates as fertilizers, struvite precipitation and biological systems such as phycoremediation (i.e. algae cultivation) and polyphosphates accumulating organisms.A digestão anaeróbia é uma tecnologia mundialmente conhecida para o tratamento de resíduos orgânicos, principalmente devido a sua capacidade de produzir metano como energia renovável. No entanto, há um interesse crescente sobre a recuperação de nutrientes (N e P), que a partir de razões ambientais e econômicas têm sido identificados como elemento-chave em plantas de digestão anaeróbia. O presente manuscrito apresenta uma visão abrangente sobre os recentes avanços em tecnologias de recuperação de nutrientes aplicáveis para sistemas de digestão anaeróbia. O foco da revisão é a recuperação do N e P através do uso de fertilizantes, como digestates precipitação estruvite e sistemas biológicos, tais como phycoremediation (por ex, cultivo de algas) e organismos acumuladores de polifosfatos.La digestión anaeróbica es una tecnología mundialmente aplicada para el tratamiento de residuos orgánicos, principalmente debido a su capacidad de producir metano como fuente de energía renovable. Sin embargo, existe un creciente interés en la recuperación de nutrientes (N y P), el cual desde el punto de vista ambiental y económico ha sido identificado como un factor clave en las plantas de tratamiento vía digestión anaeróbica. El presente manuscrito presenta una visión global de los recientes avances en las tecnologías de recuperación de nutrientes aplicables a sistemas de digestión anaeróbica. La revisión está enfocada en la recuperación de N y P mediante el uso del digestado como fertilizante, la precipitación de estruvita y sistemas biológicos como la ficoremediación (ej. cultivos de algas) y organismos acumuladores de polifosfatos

Tecnologias de recuperação de nutrientes para os sistemas de digestão anaeróbia: revisão

Anaerobic digestion is a worldwide technology to treat organic waste streams, primarily due to its capacity to produce methane as renewable energy. However, there is an increasing interest on nutrient recovery (N and P), which from both environmental and economic reasons have been identified as key feature in anaerobic digestion plants. The manuscript presents a comprehensive overview on recent advances in nutrient recovery technologies applicable for anaerobic digestion systems. The review focus on N and P recovery through the use of digestates as fertilizers, struvite precipitation and biological systems such as phycoremediation (i.e. algae cultivation) and polyphosphates accumulating organisms.A digestão anaeróbia é uma tecnologia mundialmente conhecida para o tratamento de resíduos orgânicos, principalmente devido a sua capacidade de produzir metano como energia renovável. No entanto, há um interesse crescente sobre a recuperação de nutrientes (N e P), que a partir de razões ambientais e econômicas têm sido identificados como elemento-chave em plantas de digestão anaeróbia. O presente manuscrito apresenta uma visão abrangente sobre os recentes avanços em tecnologias de recuperação de nutrientes aplicáveis para sistemas de digestão anaeróbia. O foco da revisão é a recuperação do N e P através do uso de fertilizantes, como digestates precipitação estruvite e sistemas biológicos, tais como phycoremediation (por ex, cultivo de algas) e organismos acumuladores de polifosfatos.La digestión anaeróbica es una tecnología mundialmente aplicada para el tratamiento de residuos orgánicos, principalmente debido a su capacidad de producir metano como fuente de energía renovable. Sin embargo, existe un creciente interés en la recuperación de nutrientes (N y P), el cual desde el punto de vista ambiental y económico ha sido identificado como un factor clave en las plantas de tratamiento vía digestión anaeróbica. El presente manuscrito presenta una visión global de los recientes avances en las tecnologías de recuperación de nutrientes aplicables a sistemas de digestión anaeróbica. La revisión está enfocada en la recuperación de N y P mediante el uso del digestado como fertilizante, la precipitación de estruvita y sistemas biológicos como la ficoremediación (ej. cultivos de algas) y organismos acumuladores de polifosfatos

Induced air flotation for fat, oil, and grease recovery in urban wastewater: A proposed methodology for system optimization and case study

Supplementary data to this article can be found online at https://doi. org/10.1016/j.jwpe.2022.103201.Induced air flotation (IAF) is a well-known technology that is widely applied in urban wastewater treatment plants (WWTP) for fat, oil, and grease (FOG) removal. However, most IAF systems are not optimized and typically operate with fixed parameters, regardless of inflow variations. Furthermore, the optimization of IAF systems is limited by the lack of equipment in WWTP laboratories to determine FOG concentrations in wastewater. In this study, an adapted sulfo-phospho-vanillin method for FOG quantification in wastewater is proposed for optimization and automation of the IAF system. The proposed methodology requires simple equipment that is widely available in WWTP laboratories, paving the way for in situ FOG determination. The method was successfully employed to determine the optimal operating conditions of the IAF system in terms of hydraulic retention time and organic loading rate. Furthermore, a full-scale IAF system was optimized using this methodology and its energy demand was reduced by 40 %.The authors acknowledge Gloria Prunera for the analytical support and Lleida WWTP staff the process operation support. The authors also acknowledge Ajuntament de Lleida and Agencia Catalana de l'Aigua (ACA, Generalitat de Catalunya) their support with research activities at Lleida WWTP. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.info:eu-repo/semantics/publishedVersio

Co-digestion strategies to enhance microalgae anaerobic digestion: a review

Microalgae biorefineries for the production of biofuels and high-value products have captured the attention of academia and industry. Implementing an anaerobic digestion step can enhance resource recovery from microalgae and microalgae residues. Anaerobic co-digestion, the simultaneous digestion of two or more substrates, is an opportunity to overcome the low biodegradability and the risk of ammonia inhibition associated with microalgae and microalgae residues mono-digestion. Besides, microalgae can also be used as co-substrate in biogas plants, with the aim of increasing the organic loading rate while providing alkalinity, macro- and micronutrients. Sewage sludge is the most researched co-substrate for microalgae since microalgae photobioreactors can be used for secondary, tertiary and anaerobic digestion supernatant treatment in wastewater treatment plants. However, microalgae and microalgae residues have been successfully co-digested with a wide variety of wastes, including crops, energy crops, paper waste, animal manure, vinasse, olive mill waste, and fat, oil and grease. Lipid-spent microalgae and glycerol co-digestion has also been largely researched due to the growing interest on microalgal-derived biodiesel. Most studies have assessed the impact of co-digestion on the methane yield and process kinetics through biochemical methane potential (BMP) tests. However, BMP test is not the most suitable method to assess the impact of co-digestion on other important factors such as supernatant nutrient content, digestate dewaterability, biosolids quality, and HS concentration in the biogas. Overall, more lab-scale and pilot-scale continuous experiments are needed to get a holistic understanding of microalgal anaerobic co-digestion

Co-digestion strategies to enhance microalgae anaerobic digestion: a review

Microalgae biorefineries for the production of biofuels and high-value products have captured the attention of academia and industry. Implementing an anaerobic digestion step can enhance resource recovery from microalgae and microalgae residues. Anaerobic co-digestion, the simultaneous digestion of two or more substrates, is an opportunity to overcome the low biodegradability and the risk of ammonia inhibition associated with microalgae and microalgae residues mono-digestion. Besides, microalgae can also be used as co-substrate in biogas plants, with the aim of increasing the organic loading rate while providing alkalinity, macro- and micronutrients. Sewage sludge is the most researched co-substrate for microalgae since microalgae photobioreactors can be used for secondary, tertiary and anaerobic digestion supernatant treatment in wastewater treatment plants. However, microalgae and microalgae residues have been successfully co-digested with a wide variety of wastes, including crops, energy crops, paper waste, animal manure, vinasse, olive mill waste, and fat, oil and grease. Lipid-spent microalgae and glycerol co-digestion has also been largely researched due to the growing interest on microalgal-derived biodiesel. Most studies have assessed the impact of co-digestion on the methane yield and process kinetics through biochemical methane potential (BMP) tests. However, BMP test is not the most suitable method to assess the impact of co-digestion on other important factors such as supernatant nutrient content, digestate dewaterability, biosolids quality, and H2S concentration in the biogas. Overall, more lab-scale and pilot-scale continuous experiments are needed to get a holistic understanding of microalgal anaerobic co-digestion.Peer Reviewe