The main objective of this study was to select and grow wastewater-borne cyanobacteria in a closed photobioreactor (PBR) inoculated with a mixed consortium of microalgae. The 30 L PBR was fed with a mixture of urban secondary effluent and digestate, and operated in semi-continuous mode. Based on the nutrients variation of the influent, three different periods were distinguished during one year of operation. Results showed that total inorganic nitrogen (TIN), inorganic phosphorus concentration (PO43 -), phosphorus volumetric load (LV-P) and carbon limited/non-limited conditions leaded to different species composition, nutrients removal and biomass production in the culture. High TIN/PO43 - concentrations in the influent (36 mg N L- 1/3 mg P L- 1), carbon limitation and an average LV-P of 0.35 mg P L- 1d- 1 were negatively related to cyanobacteria dominance and nutrients removal. On the contrary, cyanobacteria predominance over green algae and the highest microbial biomass production (averaging 0.084 g Volatile Suspended Solids (VSS) L- 1d- 1) were reached under TIN/PO43 - concentrations of 21 mg N L- 1/2 mg P L- 1, no carbon limitation and an average LV-P of 0.23 mg P-PO43 - L- 1d- 1. However, although cyanobacteria predominance was also favored with a LV-P 0.15 mg L- 1d- 1, biomass production was negatively affected due to a P limitation in the culture, resulting in a biomass production of 0.0.39 g VSS L- 1d- 1. This study shows that the dominance of cyanobacteria in a microalgal cyanobacterial community in an agitated PBR using wastewater as nutrient source can be obtained and maintained for 234 days. These data can also be applied in future biotechnology applications to optimize and enhance the production of added value products by cyanobacteria in wastewater treatment systems.
“The final publication is available at Springer via http://dx.doi.org/10.1016/j.scitotenv.2017.02.097"
Microalgae are nowadays regarded as a potential biomass feedstock to help reducing our dependence on fossil fuels for transportation, electricity and heat generation. Besides, microalgae have been widely investigated as a source of chemicals, cosmetics and health products, as well as animal and human feed. Among the cutting-edge applications of microalgae biomass, anaerobic digestion has shown promising results in terms of (bio)methane production. The interest of this process lies on its potential integration within the microalgae biorefinery concept, providing on the one hand a source of bioenergy, and on the other hand nutrients (nitrogen, phosphorus and CO2) and water for microalgae cultivation. This article reports the main findings in the field, highlighting the options to increase the (bio)methane production of microalgae (i.e. pretreatment and co-digestion) and bottlenecks of the technology. Finally, energy, economic and environmental aspects are considered.
The final publication is available at Springer via http://dx.doi.org/10.1007/s12649-016-9604-3
Gutierrez, R.; Ferrer, I.; González-Molina, A.; Salvado, H.; Garcia, J.; Uggetti, E. Water research (Oxford) Vol. 106, p. 539-549 DOI: 10.1016/j.watres.2016.10.039 Data de publicació: 2016-12 Article en revista
Microalgal biomass harvesting by inducing spontaneous flocculation (bioflocculation) sets an attractive approach, since neither chemicals nor energy are needed. Indeed, bioflocculation may be promoted by recycling part of the harvested microalgal biomass to the photobioreactor in order to increase the predominance of rapidly settling microalgae species. The aim of the present study was to improve the recovery of microalgal biomass produced in wastewater treatment high rate algal ponds (HRAPs) by recycling part of the harvested microalgal biomass. The recirculation of 2% and 10% (dry weight) of the HRAPs microalgal biomass was tested over one year in an experimental HRAP treating real urban wastewater. Results indicated that biomass recycling had a positive effect on the harvesting efficiency, obtaining higher biomass recovery in the HRAP with recycling (R-HRAP) (92–94%) than in the control HRAP without recycling (C-HRAP) (75–89%). Microalgal biomass production was similar in both systems, ranging between 3.3 and 25.8 g TSS/m2d, depending on the weather conditions. Concerning the microalgae species, Chlorella sp. was dominant overall the experimental period in both HRAPs (abundance >60%). However, when the recycling rate was increased to 10%, Chlorella sp. dominance decreased from 97.6 to 88.1%; while increasing the abundance of rapidly settling species such as Stigeoclonium sp. (16.8%, only present in the HRAP with biomass recycling) and diatoms (from 0.7 to 7.3%). Concerning the secondary treatment of the HRAPs, high removals of COD (80%) and N-NH4+ (97%) were found in both HRAPs. Moreover, by increasing the biomass recovery in the R-HRAP the effluent total suspended solids (TSS) concentration was decreased to less than 35 mg/L, meeting effluent quality requirements for discharge. This study shows that microalgal biomass recycling (10% dry weight) increases biomass recovery up to 94% by selecting the most rapidly settling microalgae species without compromising the biomass production and improving the wastewater treatment in terms of TSS removal.
The aim of this study was to quantitatively assess the net increase in microalgal biomass concentration induced by photosynthetic microbial fuel cells (PMFC). The experiment was conducted on six lab-scale PMFC constituted by an anodic chamber simulating an anaerobic digester connected to a cathodic chamber consisting of a mixed algae consortia culture. Three PMFC were operated at closed circuit (PMFC+) whereas three PMFC were left unconnected as control (PMFC-). PMFC+ produced a higher amount of carbon dioxide as a product of the organic matter oxidation that resulted in 1.5–3 times higher biomass concentration at the cathode compartment when compared to PMFC-
Uggetti, E.; Hughes, T.; Morris, R.; Newton, M.; Trabi, C.; Hawes, P.; Puigagut, J.; Garcia, J. Science of the total environment Vol. 559, p. 212-217 DOI: 10.1016/j.scitotenv.2016.03.195 Data de publicació: 2016-07-15 Article en revista
Forced aeration of horizontal subsurface flow constructed wetlands (HSSF CWs) is nowadays a recognized method to improve treatment efficiency, mainly in terms of ammonium removal. While numerous investigations have been reported testing constant aeration, scarce information can be found about the efficiency of intermittent aeration. This study aims at comparing continuous and intermittent aeration, establishing if there is an optimal regime that will increase treatment efficiency of HSSFCWs whilst minimizing the energy requirement. Full and intermittent aeration were tested in a pilot plant of three HSSF CWs (2.64 m(2) each) fed with primary treated wastewater. One unit was fully aerated; one intermittently aerated (i.e. by setting a limit of 0.5 mg/L dissolved oxygen within the bed) with the remaining unit not aerated as a control. Results indicated that intermittent aeration was the most successful operating method. Indeed, the coexistence of aerobic and anoxic conditions promoted by the intermittent aeration resulted in the highest COD (66%), ammonium (99%) and total nitrogen (79%) removals. On the other hand, continuous aeration promotes ammonium removal (99%), but resulted in nitrate concentrations in the effluent of up to 27 mg/L. This study demonstrates the high potential of the intermittent aeration to increase wastewater treatment efficiency of CWs providing an extreme benefit in terms of the energy consumption.
Taking into account the current global water scarcity and the expensive operation and maintenance cost of wastewater treatment, INCOVER concept has been designed to move wastewater treatment from being primarily a sanitation technology towards a bio-product recovery industry and a recycled water supplier. A wastewater specific Decision Support System methodology will be tailored to the INCOVER technologies and provide data and selection criteria for a holistic wastewater management approach.
Three added-value plants treating wastewater from three case-studies (municipalities, farms and food and beverage industries) will be implemented, assessed and optimised concurrently. INCOVER plants will be implemented at demonstration scale in order to achieve Technology Readiness Level(TRL) of 7-8 to ensure straightforward up scaling to 100,000 population equivalents (PE). INCOVER added-value plants will generate benefits from wastewater offering three recovery solutions: 1) Chemical recovery (bio-plastic and organic acids) via algae/bacteria and yeast biotechnology; 2) Near-zero-energy plant providing upgraded bio-methane via pre-treatment and anaerobic co-digestion systems; 3) Bio-production and reclaimed water via adsorption, biotechnology based on wetlands systems and hydrothermal carbonisation. To improve added-value production efficiency, INCOVER solutions will include monitoring and control via optical sensing and soft-sensors.
INCOVER solutions will reduce at least a 50% overall operation and maintenance cost of wastewater treatment through the use of wastewater as a source for energy demand and added-value production to follow UE circular economy strategy. In addition, strategies to facilitate the market uptake of INCOVER innovations will be carried out in order to close the gap between demonstration and end-users.
An estimated turnover of 188 million€ for INCOVER lead-users is expected after the initial exploitation strategy of 5 years implementing 27 INCOVER solutions.
Gutierrez, R.; Ferrer, I.; Uggetti, E.; Arnabat, C.; Salvado, H.; Garcia, J. Algal research: biomass, biofuels and bioproducts Vol. 16, p. 409-417 DOI: 10.1016/j.algal.2016.03.037 Data de publicació: 2016-06 Article en revista
The aim of this study was to evaluate the settling velocity distribution of microalgal biomass with and without flocculant (Tanfloc SG). Microalgal biomass was obtained from two experimental wastewater treatment high rate algal ponds (HRAPs) operated with 4 and 8 days of hydraulic retention time. Two sets of dynamic sedimentation tests were carried out using a water elutriation apparatus. In the first set, most of the biomass of the 8 days-HRAP (63%) had settling velocities between 16.5 and 4 m/h, while most of the biomass of the 4 days-HRAP (65%) had settling velocities between 16.5 and 1 m/h. In the second set, most of the biomass from both HRAPs (60% from the 8 days-HRAP and 80% from the 4 days-HRAP) had settling velocities between 6.5 and 0.4 m/h. In this second set, settling velocities of <0.4 m/h were reached by 20% and 40% of the biomass from 4 days-HRAP and 8 days-HRAP, respectively. The addition of flocculant at optimal doses ranging from 20 to 40 mg/L had impressive effects on the settling velocity distribution in this second set. 70% and 84% of biomass reached velocities of >6.5 m/h, compared to 10% and 14% of microalgal biomass without flocculant for the 8 days-and 4 days-HRAPs, respectively. With flocculant, a very small amount of biomass (3% for the 4 days-HRAP and 8% for the 8 days-HRAP) had settling velocities of <0.4 m/h. Microscopic examination of samples from sedimentation tests showed how an important amount of microalgae settled in the system. Indeed, <1500 microalgae individuals/mL were found in all outlet samples from the elutriation apparatus (inlet samples of >10(5) microalgae individuals/mL). According to our results, a settler designed with a critical settling velocity of 1m/h would reach biomass recoveries as high as 90-94% with flocculant compared to 77-88% without flocculant.
Actualmente, la investigación de nuevas fuentes de energía ha centrado la atención hacia las microalgas. El principal desafio para la producción de microalgas a gran escala es realizar una recuperación de la biomasa algal eficente y rentable para su posterior valorización. En el contexto del tratamiento de aguas residuales, el proceso de coagulación-floculación seguido de la sedimentación representa la técnica de recuperación de microalgas más adecuada debido al bajo consumo energético y a los bajos costes asociados.El objetivo principal de la tesis doctoral fue evaluar y mejorar la eficiencia de separación de la biomasa algal cultivada en lagunas de alta carga (LAC) para el tratamiento de agua residual urbana. Esto se consiguió aplicando técnicas de pre-concentración basadas en procesos de floculación. A posteriori, se evaluó el balance energético de un sistema de tratamiento de aguas residuales a gran escala situado en la región Mediterránea, formado por un sistema de LAC seguido de un proceso de digestión anaeróbica de la biomasa.En primer lugar, la coagulación-floculación y sedimentación con dos floculantes naturales poliméricos (Ecotan y Tanfloc) se evaluó por medio de ensayos de sedimentación estáticos en columnas de sedimentación convencionales. Ambos floculantes obtubieron dosis ótimas bajas (10-50 mg / L) que permitieron la recuperación del 90% de la biomasa. Además, estos aumentaron la velocidad de sedimentación de la biomasa algal, implicando una recuperación de la biomasa rápida y eficiente (> 90% de recuperación en 10 a 20 min). Posteriormente, los tests de sedimentación dinámica se realizaron en un dispositivo dotado de tres columnas de sedimentación con el fin de evaluar la distribución de velocidades de sedimentación de la biomasa con y sin el efecto de floculantes. Esta vez, se evaluaró un floculante polimérico (Tanfloc) y un almidón catiónico. En estos ensayos, se auménto del 10-14% (son floculante) al 70-84% (con coagulante) la fracción de biomasa con unas velocidades de sedimentación mayores a 6,5 m/h tras la adición de 20-40 mg/L de Tanfloc. Por otra parte, entre10 y 25 mg / L de almidón fueron necesarios para recuperar más del 95% de la biomasa,incrementando del 46% a 78% la fracción de partículas con velocidades de sedimentación mayores a 6,5 m / h. Según los resultados, un decantador diseñado con una velocidad de sedimentación de 1 m / h (valor típico en decantadores secundarios) permitiría la recuperación del 90% de la biomasa, reduciendo el tiempo de retención hidráulico y la superficie de los decantadores, tras la adición de los floculantes naturales estudiados. La separación de la biomasa también se evaluó mediante la recirculación de una fracción de la biomasa cosechada (2% y 10% del peso en seco) en un sistema de LAC para el tratamiento de aguas residuales con el fin de aumentar el predominio de aquellas especies con altas tasas de sedimentación. Los resultados indicaron que la recirculación aumento la eficiencia de recuperación, obteniendo mayores recuperaciones en la LAC con recirculación (91-93%) que en LAC sin recirculación (75-88%), y aumentando el porcentaje de la biomasa con velocidad de sedimentación elevadas. Esto fue debido a la aparación de especies con altas tasas de sedimentación tales como Stigeoclonium sp. y diatomeas presentes cuando se recirculó el 10% de biomasa cosechada. Por último, el balance energético de una planta de tratamiento de aguas residuales a base de microalgas situada en la región Mediterránea se evaluó a partir de resultados experimentales de la biomasa algal crecida en LAC y sometida a la digestión anaerobia (con o sin tratamiento térmico previo) para producir biogás y generar electricidad y / o calor. El estudio concluyó que se debe lograr una mínima producción de biomasa algal de 15 g SST / m2d y / o unas producciones de metano de 0,5 m3CH4 / kgVS para obtener un sistema energéticamente autosuficiente durante todo el año
Research of new sources of bioenergy is nowadays driving attention to microalgae. Cost-effective biomass harvesting poses a challenge for full-scale microalgae production for biofuels. In the context of wastewater treatment with microalgae cultures, coagulation-flocculation followed by sedimentation seems to be the most suitable option for microalgae harvesting as low energy and no extra materials are required.
The main objective if this PhD thesis was to evaluate and improve the harvesting efficiency of microalgal biomass grown in wastewater treatment high rate algal ponds (HRAPs) by means of flocculation-based pre-concentration techniques (i.e. coagulation-flocculation with organic flocculants and biomass recycling). Moreover, the energy assessment of a full-scale wastewater treatment system based on HRAPs followed by anaerobic digestion of harvested microalgal biomass located in a Mediterranean Region was assessed.
Firstly, coagulation-flocculation and sedimentation with two tannin-based polymeric flocculants (Ecotan and Tanfloc) was evaluated by means of static sedimentation tests in conventional settling columns. Low flocculants doses (10-50 mg/L) enabled over 90% biomass recovery. Furthermore, both flocculants increased microalgae settling velocity, leading to fast and efficient biomass recovery (> 90% recovery in 10-20 min).
Subsequently, dynamic sedimentation tests were performed in a water elutriation apparatus in order to evaluate the settling velocities distribution of microalgal biomass with and without flocculants. This time, a tannin-based flocculant (Tanfloc) and a cationic starch were evaluated. The amount of biomass reaching settling velocities higher than 6.5 m/h increased from 10-14% (without flocculant) to 70-84% when 20-40 mg/L of Tanfloc were added. On the other hand, 10-25 mg/L of starch enabled more than 95% biomass recovery, increasing from 46% to 78% the amount of particles with settling velocities higher than 6.5 m/h. According to the results, a settler designed with a critical settling velocity of 1 m/h (which is a typical value in secondary settlers) would enable over 90% biomass recovery while reducing the hydraulic retention time and the settler surface as compared to biomass harvesting without flocculants.
Microalgal biomass harvesting was also tested by recycling some of the harvested microalgal biomass (2% and 10% dry weight) to the pilot wastewater treatment HRAP in order to increase the predominance of rapidly-settling microalgae species. Results indicated that biomass recycling had a positive effect on the harvesting efficiency, obtaining higher recoveries in the pilot HRAP with recycling (91-93%) than in the pilot HRAP without recycling (75 ¿ 88%), and increasing the percentage of biomass with high settling velocity. This was due to the fact that the abundance of rapidly-settling strains such as Stigeoclonium sp. and diatoms increased when 10% (dry weight) of harvested biomass was recycled.
Experimental results from this PhD thesis suggested that either flocculation with natural organic flocculants or biomass recycling improves harvesting efficiency of microalgal biomass with high biomass recoveries (>90%), increasing by 2-8-folds the amount of biomass with high settling velocities (6.5 m/h) and obtaining the best results in those experiments in which rapidly settling species (e.g. Stigeoclonium sp. and diatoms) were dominant. Finally, the energy balance of a microalgae-based wastewater treatment plant located in the Mediterranean Region was assessed based on experimental results. The harvested microalgal biomass grown in wastewater HRAPs would undergo anaerobic digestion (with or without thermal pretreatment) to produce biogas and generate electricity and/or heat. The energy assessment concluded that the system should achieve microalgal biomass production of at least 15 g TSS/m2d and/or a methane yield of 0.5 m3CH4/KgVS all over the year to be energy self-sufficient.
Actualmente, la investigación de nuevas fuentes de energía ha centrado la atención hacia las microalgas. El principal desafio para la producción de microalgas a gran escala es realizar una recuperación de la biomasa algal eficente y rentable para su posterior valorización. En el contexto del tratamiento de aguas residuales, el proceso de coagulación-floculación seguido de la sedimentación representa la técnica de recuperación de microalgas más adecuada debido al bajo consumo energético y a los bajos costes asociados. El objetivo principal de la tesis doctoral fue evaluar y mejorar la eficiencia de separación de la biomasa algal cultivada en lagunas de alta carga (LAC) para el tratamiento de agua residual urbana. Esto se consiguió aplicando técnicas de pre-concentración basadas en procesos de floculación. A posteriori, se evaluó el balance energético de un sistema de tratamiento de aguas residuales a gran escala situado en la región Mediterránea, formado por un sistema de LAC seguido de un proceso de digestión anaeróbica de la biomasa. En primer lugar, la coagulación-floculación y sedimentación con dos floculantes naturales poliméricos (Ecotan y Tanfloc) se evaluó por medio de ensayos de sedimentación estáticos en columnas de sedimentación convencionales. Ambos floculantes obtubieron dosis ótimas bajas (10-50 mg / L) que permitieron la recuperación del 90% de la biomasa. Además, estos aumentaron la velocidad de sedimentación de la biomasa algal, implicando una recuperación de la biomasa rápida y eficiente (> 90% de recuperación en 10 a 20 min). Posteriormente, los tests de sedimentación dinámica se realizaron en un dispositivo dotado de tres columnas de sedimentación con el fin de evaluar la distribución de velocidades de sedimentación de la biomasa con y sin el efecto de floculantes. Esta vez, se evaluaró un floculante polimérico (Tanfloc) y un almidón catiónico. En estos ensayos, se auménto del 10-14% (son floculante) al 70-84% (con coagulante) la fracción de biomasa con unas velocidades de sedimentación mayores a 6,5 m/h tras la adición de 20-40 mg/L de Tanfloc. Por otra parte, entre10 y 25 mg / L de almidón fueron necesarios para recuperar más del 95% de la biomasa,incrementando del 46% a 78% la fracción de partículas con velocidades de sedimentación mayores a 6,5 m / h. Según los resultados, un decantador diseñado con una velocidad de sedimentación de 1 m / h (valor típico en decantadores secundarios) permitiría la recuperación del 90% de la biomasa, reduciendo el tiempo de retención hidráulico y la superficie de los decantadores, tras la adición de los floculantes naturales estudiados. La separación de la biomasa también se evaluó mediante la recirculación de una fracción de la biomasa cosechada (2% y 10% del peso en seco) en un sistema de LAC para el tratamiento de aguas residuales con el fin de aumentar el predominio de aquellas especies con altas tasas de sedimentación. Los resultados indicaron que la recirculación aumento la eficiencia de recuperación, obteniendo mayores recuperaciones en la LAC con recirculación (91-93%) que en LAC sin recirculación (75-88%), y aumentando el porcentaje de la biomasa con velocidad de sedimentación elevadas. Esto fue debido a la aparación de especies con altas tasas de sedimentación tales como Stigeoclonium sp. y diatomeas presentes cuando se recirculó el 10% de biomasa cosechada. Por último, el balance energético de una planta de tratamiento de aguas residuales a base de microalgas situada en la región Mediterránea se evaluó a partir de resultados experimentales de la biomasa algal crecida en LAC y sometida a la digestión anaerobia (con o sin tratamiento térmico previo) para producir biogás y generar electricidad y / o calor. El estudio concluyó que se debe lograr una mínima producción de biomasa algal de 15 g SST / m2d y / o unas producciones de metano de 0,5 m3CH4 / kgVS para obtener un sistema energéticamente autosuficiente durante todo el año
Aerated batch reactors (2.5 L) fed either with urban or synthetic wastewater were inoculated with microalgae (dominated by Chlorella sp. and Scenedesmus sp.) to remove caffeine, ibuprofen, galaxolide, tributyl phosphate, 4-octylphenol, tris(2-chloroethyl) phosphate and carbamazepine for 10 incubation days. Non-aerated and darkness reactors were used as controls. Microalgae grew at a rate of 0.25 d-1 with the complete removal of N-NH4 during the course of the experiment. After 10 incubation days, up to 99% of the microcontaminants with a Henry’s law constant higher than 3 10-1 Pa m3 mol-1 (i.e., 4-octylphenol, galaxolide, and tributyl phosphate) were removed by volatilization due to the effect of air stripping. Whereas biodegradation was effective for removing ibuprofen and caffeine, carbamazepine and tris(2-chloroethyl) phosphate behaved as recalcitrant compounds. The use of microalgae was proved to be relevant for increasing the biodegradation removal efficiency of ibuprofen by 40% and reducing the lag phase of caffeine by 3 days. Moreover, the enantioselective biodegradation of S-ibuprofen suggested a biotic prevalent removal process, which was supported by the identification of carboxy-ibuprofen and hydroxy-ibuprofen. The results from microalgae reactors fed with synthetic wastewater showed no clear evidences of microalgae uptake of any of the studied microcontaminants.
Solimeno, A.; Samsó, R.; Uggetti, E.; Sialve, B.; Steyer, J.; Gabarró, A.; Garcia, J. Algal research: biomass, biofuels and bioproducts Vol. 12, p. 350-358 DOI: 10.1016/j.algal.2015.09.008 Data de publicació: 2015-11-01 Article en revista
The prospect of treating wastewater and at the same time producing microalgae biomass is receiving increasing attention. Mechanistic models for microalgae growth in wastewater are currently being developed for new systems design as well as to improve the understanding of the involved biokinetic processes. However, mathematical models able to describe the complexity of microalgal cultures are still not a common practice. The aim of the present study is to present and calibrate a new mechanistic model built in COMSOL Multiphysics™ platform for the description of microalgae growth. Carbon-limited algal growth, transfer of gases to the atmosphere; and photorespiration, photosynthesis kinetics and photoinhibition are included. The model considers the growth of microalgae as a function of light intensity and temperature, as well as availability of nitrogen and other nutrients. The model was calibrated using experimental data from a case study based on the cultivation of microalgae species in synthetic culture medium. The model was able to reproduce experimental data. Simulation results show the potential of the model to predict microalgae growth and production, nutrient uptake, and the influence of temperature, light intensity and pH on biokinetic processes of microalgae.
Labella, A.; Caniani, D.; Hughes, T.; Morrison, R.; Newton, M.; Hawes, P.; Puigagut, J.; Garcia, J.; Uggetti, E. Ecological engineering Vol. 83, p. 184-190 DOI: 10.1016/j.ecoleng.2015.06.028 Data de publicació: 2015-10 Article en revista
Constructed wetlands including aeration and heating were studied to improve treatment efficiency and prevent clogging. The experiments were carried out in a pilot plant (0.4 m(2)) treating urban wastewater with an organic loading rate of 40-60 g COD/m(2) d. Continuous and intermittent aeration was performed from the bottom on 8% of the wetland surface, leading to different dissolved oxygen concentrations within the wetlands (from 0.2 to 5 mg O-2/L). Continuous aeration increased organic matter (COD) and ammonium nitrogen removal by 56% and 69%, respectively. Improvements in wastewater treatment caused by aeration can result in reduction of the surface area requirement of future systems. This work demonstrated that for the studied configuration the cost of the power consumption of the continuous aeration was largely covered by the reduction of the wetlands surface. Even if the heating of 8% of the wetland surface at 21 degrees C had no effects on treatment performance, positive results showed that solids accumulation rate within the granular medium, which is closely related to the development of clogging. It has been demonstrated that heating for 10 days per year during 20 year period would delay the equivalent of 1 year of solids accumulation.
In the context of wastewater treatment with microalgae cultures, coagulation-flocculation followed by sedimentation is one of the suitable options for microalgae harvesting. This process is enabled by the addition of chemicals (e.g. iron). However, in a biorefinery perspective, it is important to avoid possible contamination of downstream products caused by chemicals addition. The aim of this study was to evaluate the effect of potato starch as flocculant for microalgal biomass coagulation-flocculation and sedimentation. The optimal flocculant dose (25 mg/L) was determined with jar tests. Such a concentration led to more than 95% biomass recovery (turbidity < 9NTU). The settleability of flocs was studied using an elutriation apparatus measuring the settling velocities distribution. This test underlined the positive effect of starch on the biomass settling velocity, increasing to >70% the percentage of particles with settling velocities >6.5 m/h. Finally, biochemical methane potential tests showed that starch biodegradation increased the biogas production from harvested biomass. (C) 2015 Elsevier Ltd. All rights reserved.
Gutierrez, R.; Passos , F.; Ferrer, I.; Uggetti, E.; Garcia, J. Algal research: biomass, biofuels and bioproducts Vol. 9, p. 204-211 DOI: 10.1016/j.algal.2015.03.010 Data de publicació: 2015-05-01 Article en revista
Research on new sources of bioenergy is nowadays driving attention to microalgae. Cost-effective biomass harvesting and thickening pose a challenge for massive microalgae production for biofuels. In this study, coagulation-flocculation and sedimentation with natural flocculants (Ecotan and Tanfloc) was evaluated on microalgae grown in an experimental high rate algal pond treating urban wastewater. Jar tests showed how flocculant doses of 10 and 50mg/L of Ecotan and Tanfloc enabled over 90% biomass recovery. Furthermore, settling column tests showed that both flocculants increased microalgae settling velocity, performing fast and efficient biomass recovery (>90% recovery in 10-20min). Thus, the use of either flocculant would enhance microalgal biomass reducing the HRT and settler volume. Finally, the potential toxicity of flocculants upon biomass production was assessed in biochemical methane potential tests. Results indicated that doses of 10-50mg/L of Ecotan and Tanfloc did not affect anaerobic digestion, leading to the same methane yield (162-166mL CH4/g VS) with the same methane content (70%) as the control without flocculants. This study demonstrates that Ecotan and Tanfloc flocculants would be appropriate for microalgae biomass harvesting and subsequent biogas generation.
Microalgae have been intensively studied as a source of biomass for replacing conventional fossil fuels in the last decade. The optimization of biomass production, harvesting and downstream processing is necessary for enabling its full-scale application. Regarding biofuels, biogas production is limited by the characteristics of microalgae, in particular the complex cell wall structure of most algae species. Therefore, pretreatment methods have been investigated for microalgae cell wall disruption and biomass solubilization before undergoing anaerobic digestion. This paper summarises the state of the art of different pretreatment techniques used for improving microalgae anaerobic biodegradability. Pretreatments were divided into 4 categories: (i) thermal; (ii) mechanical; (iii) chemical and (iv) biological methods. According to experimental results, all of them are effective at increasing biomass solubilization and methane yield, pretreatment effect being species dependent. Pilot-scale research is still missing and would help evaluating the feasibility of full-scale implementation. (C) 2014 Elsevier Ltd. All rights reserved.
'Subsurface-flow constructed wetlands have become a very popular cost effective and green technology for treatment of waste water throughout Europe and the rest of the world. Original predictions over the longevity of constructed wetlands were approximately 50 -100 years (Conley et al 1991). However, it has become disappointingly apparent that these systems are clogging and have on average a lifetime of less than 10 years (Griffin et al 2008). Currently when a wetland becomes clogged, the whole site has to be refurbished and the reeds regrown, which takes several years and has significant economic consequences for the operators.
Our project ARBI aims to develop and trial an Autonomous Reed Bed Installation containing a magnetic resonance probe, can be deployed in several locations within a wetland to give measurements at different depths. By measuring the relaxation times of MR, sufficient information can be obtained to determine the clog state of the gravel bed of a wetland. This would enable the operators to isolate those areas of the bed where the problem resides and make a partial intervention, without the need to remove and re-plant the whole reed bed. When the system is developed, we will have potential for application in other water treatment systems based on subsurface flows like: slow rate sand filters, and river bank filtration.
The project will have major benefits for those organisations who would like to install reedbeds but have resisted doing because of concerns over performance and maintenance costs. These will increase the potential size of the market for reedbed installers and benefit the SMEs in the consortium who currently are operating in a constrained market which has not achieved its true potential.'
'At a time with an urgent need to conserve water resources, efficient sanitation systems play a key role in sustainability. They can ensure that the vital resource Water is recovered from waste and can be re-used at the same time as protecting human health and the environment. The SWINGS project consortium will establish an optimal methodology for nutrient and energy recovery from wastewater (WW) at the same time as making the water safe for reuse, all in a manner conducible to rural communities in developing countries, with India as the concrete example. In particular, the SWINGS project will enlist already optimized municipal WW treatment concepts and combine 'green' and sustainable technologies. The result will be enhances water recycling and re-use, decreased energy consumption, and production of useful by-products from the process as secondary resources. Thus, treated WW will be transformed to soil enrichment resource, to irrigation water, to aquaculture farm feed, via sustainable sanitation that safeguards the local drinking water supply in India.
The starting point of the SWINGS project will be anaerobic digestion (AD) and constructed wetlands (CW) that will be configured with environmentally sustainable disinfection technologies, like water solar disinfection. Pilot plants will be designed and constructed in India that combine the treatment methods mentioned above, after which the new systems will be established in steady-state operation, and then, the AD-CW configurations optimized. Systems for disinfection of the effluent will be implemented and on-line monitoring of pathogen load attempted. Finally, life cycle assessment of several treatment configurations will be used to develop a decision support system for future selection of sustainable and efficient treatment technologies in developing countries like India. The project will publish articles and hold workshops in order to disseminate its results, especially to SMEs and to public authorities.'
'The here proposed NAwATech Europe proposal is closely interconnected with the partner project NaWaTech India. In order to reach the maximal impact the two projects have formed one common work plan for both projects, targeting the same objectives, will present their results at the same web-site and formed a joint management team. Providing adequate water supply and sanitation, particularly in urban areas, is a challenging task for governments throughout the world. This task is made even more difficult due to predicted dramatic global changes. In order to cope with water shortages in urban areas, there is a need for a paradigm shift from conventional end-of-pipe water management to an integrated approach. This integrated approach should include several actions such as: (i) interventions over the entire urban water cycle; (ii) optimisation of water use by reusing wastewater and preventing pollution of freshwater source; (iii) prioritisation of small-scale natural and technical systems, which are flexible, cost-effective and require low operation and maintenance. Natural water systems, such as manmade wetlands and sub-soil filtration and storage via soil aquifer treatment and bank filtration, are such systems. NaWaTech stands for natural water systems and treatment technologies to cope with water shortages in urbanised areas in India. The concept is based on optimised use of different urban water flows by treating each of these flows via a modular natural system taking into account the different nature and degree of pollution of the different water sources. Thus, it will cost-effectively improve the water quality of urban surface water and restore depleting groundwater sources. Due to the multi-barrier approach, these systems will also be able to treat heavily polluted water (i.e. wastewater) in order to reuse them and to supplement traditional sources to cope with water shortages today and in the future.'
Ferrer, I.; Marianna Garfi'; Uggetti, E.; Ferrer-Martí, L.; Calderón, A.; Velo, E. Biomass and bioenergy Vol. 35, num. 5, p. 1668-1674 DOI: 10.1016/j.biombioe.2010.12.036 Data de publicació: 2011-05 Article en revista
Low-cost tubular digesters originally developed in tropical regions have been adapted to the extreme weather conditions of the Andean Plateau (3000e4000 m.a.s.l.). The aim of this study was to characterise biogas production in household digesters located at high altitude, operating under psychrophilic conditions. To this end, two pilot digesters were monitored and field campaigns were carried out in two representative digesters of rural communities. Digesters’ useful volume ranged between 2.4 and 7.5m3, and hydraulic residence time (HRT) between 60 and 90 days. The temperature inside the digester’s greenhouse ranged between 20 and 25 ºC. Treating cow manure, a specific biogas production around 0.35 m3 kgVS1 was
obtained, with some 65% CH4 in biogas. In order to fulfil daily requirements for cooking and lighting, biogas production should be enhanced without increasing implementation costs as not to impede the expansion of this technology at household scale. In this sense, HRT below 60 days and OLR above 1 kgVSm-3 day-1 should be investigated to decrease digesters’ volume
(i.e. costs) and increase biogas production rate. The adaptation of conventional gas burners to biogas characteristics can also contribute in improving the efficiency of the system.
Sludge treatment wetlands (STW) emerge as a promising sustainable technology with low
energy requirements and operational costs. In this study, technical, economic and environmental aspects of STW are investigated and compared with other alternatives for sludge management in small communities (<2000 population equivalent). The performance of fullscale STW was characterised during 2 years. Sludge dewatering increased total solids (TS)
concentration by 25%, while sludge biodegradation lead to volatile solids around 45% TS and DRI24h between 1.1 and 1.4 gO2/kgTS h, suggesting a partial stabilisation of biosolids. In the economic and environmental assessment, four scenarios were considered for comparison: 1) STW with direct land application of biosolids, 2) STW with compost post-treatment, 3) centrifuge with compost post-treatment and 4) sludge transport to an intensive wastewater
treatment plant. According to the results, STW with direct land application is the most
cost-effective scenario, which is also characterised by the lowest environmental impact. The life cycle assessment highlights that global warming is a significant impact category in all scenarios, which is attributed to fossil fuel and electricity consumption; while greenhouse gas emissions from STW are insignificant. As a conclusion, STW are the most appropriate alternative for decentralised sludge management in small communities.
Sludge treatment wetlands consist of constructed wetlands which have been upgraded for sludge treatment over the last decades. Sludge dewatering and stabilisation are the main features of this technology, leading to a final product which may be recycled as an organic fertiliser or soil conditioner. In this study, biosolids from full-scale treatment wetlands were characterised in order to evaluate the quality of the final product for land application, even without further post-treatment such as composting. Samples of influent and treated sludge were analysed for pH, Electrical Conductivity, Total Solids (TS), Volatile Solids (VS), Chemical Oxygen Demand (COD), Dynamic Respiration Index (DRI), nutrients (Total Kjeldahl Nitrogen (TKN), Total Phosphorus (TP) and Potasium (K)), heavy metals and faecal bacteria indicators (E. coli and Salmonella spp.). According to the results, sludge water content and therefore sludge volume are reduced by 25 %. Organic matter biodegradation leads to VS around 43-44 %TS and COD around 500 g•kgTS-1. The values of DRI24h (1000-1500 mgO2∙kgTS-1∙h-1) indicate that treated sludge is almost stabilised final product. Besides, the concentration of nutrients is quite low (TKN~4 %TS, TP~0.3 %TS and K~0.2-0.6 %TS). Both heavy metals and faecal bacteria indicators meet current legal limits for land application of the sludge. Our results suggest that biosolids from the studied treatment wetlands could be valorised in agriculture, especially as soil conditioners.
Hoy en día la gestión del lodo de depuradora es un tema clave dentro del tratamiento del agua residual, representando hasta el 60% de los costes de operación de una depuradora urbana. El elevado contenido de agua del lodo encarece su gestión, justificando la necesidad de desarrollar métodos simples y económicos para reducir su volumen. Durante las últimas décadas, se ha adaptado la
tecnología de los humedales construidos o lechos de macrófitos a la deshidratación del lodo. Como principales ventajas destacan una demanda energética, costes de operación y mantenimiento reducidos, y una buena integración en el paisaje. Sin embargo, el número de plantas en operación actualmente es muy reducido en comparación con los tratamientos mecánicos convencionales. En este artículo se describen las principales características y aspectos operacionales de los humedales construidos para el tratamiento del lodo, resumiendo los resultados más relevantes de la literatura.
Sludge management has become a key issue in wastewater treatment, representing some 20–60% of the operational costs of conventional wastewater treatment plants. The high water content of the sludge
results in large daily flow rates to be handled and treated. Thus, the search for methods to improve sludge volume reduction continues to be of major interest. The technology known as sludge treatment wetlands
has been used for sludge dewatering since the late 1980s. Major advantages include its low energy requirements, reduced operating and maintenance costs, and a reasonable integration in the environment. However, the number of plants in operation is still low in comparison with conventional technologies.
This study represents a review of the state of the art of sludge treatment wetlands. The main characteristics and operational aspects of the technology are described, including a summary of the main results reported in the literature. Finally, the efficiency of sludge treatment wetlands versus conventional
treatments is compared.
Uggetti, E.; Llorens, E.; Pedescoll, A.; Ferrer, I.; Castellnou, R.; Garcia, J. Bioresource technology Vol. 100, num. 17, p. 3882-3890 DOI: 10.1016/j.biortech.2009.03.047 Data de publicació: 2009-09 Article en revista
Optimization of sludge management can help reducing sludge handling costs in wastewater treatment plants. Sludge drying reed beds appear as a new and alternative technology which has low energy requirements, reduced operating and maintenance costs, and causes little environmental impact. The objective of this work was to evaluate the efficiency of three full-scale drying reed beds in terms of sludge dewatering, stabilization and hygienisation. Samples of influent sludge and sludge accumulated in the reed beds were analysed for pH, Electrical Conductivity, Total Solids (TS), Volatile Solids (VS), Chemical Oxygen Demand, Biochemical Oxygen Demand, nutrients (Total Kjeldahl Nitrogen (TKN) and Total Phosphorus (TP)), heavy metals and faecal bacteria indicators (Escherichia coli and Salmonella spp.). Lixiviate samples were also collected. There was a systematic increase in the TS concentration from 1–3% in the influent to 20–30% in the beds, which fits in the range obtained with conventional dewatering technologies. Progressive organic matter removal and sludge stabilization in the beds was also observed (VS concentration decreased from 52–67% TS in the influent to 31–49% TS in the beds). Concentration of nutrients of the sludge accumulated in the beds was quite low (TKN 2–7% TS and TP 0.04–0.7% TS), and heavy metals remained below law threshold concentrations. Salmonella spp. was not detected in any of the samples, while E. coli concentration was generally lower than 460 MPN/g in the sludge accumulated in the beds. The studied systems demonstrated a good efficiency for sludge dewatering and stabilization in the context of small remote wastewater treatment plants.
Sludge drying reed beds stand as a suitable technology for sludge management in certain situations. This work examines two full-scale sludge drying reed beds systems located in a Mediterranean region. Samples of influent sludge and sludge accumulated in the reed beds were analysed for total solids (TS), volatile solids (VS), chemical oxygen demand, nutrients, heavy metals and faecal bacteria indicators. The results show a high dewatering degree (from 1–3 to 20–22%TS), progressive organic matter removal (10–30% VS/TS) and sludge mineralization during sludge storage. The concentration of nutrients, heavy metals and faecal bacteria indicators suggest a good quality of the sludge for land application.
PRODUCCIÓN DE BIOGÁS A PARTIR DE RESIDUOS ORGANICOS EN BIODIGESTORES DE BAJO COSTE Ivet Ferrer*, Enrica Uggetti**, Davide Poggio***, Enric Velo**** Grup de Recerca en Cooperació i Desenvolupament Humà C. Jordi Girona, 31 08034 - Barcelona, Spain Phone: +34 93 401 64 63 Pàgina web: http://www.upc.edu/grecdh email@example.com *, firstname.lastname@example.org**, email@example.com***, firstname.lastname@example.org**** Palabras clave: Digestión anaerobia; Biodigestor; Biogás; Energía; Fertilizante. RESUMEN La digestión anaerobia, o biodigestión, es una tecnología ampliamente difundida a escala familiar en países como China, India o Nepal. En estos sistemas los residuos orgánicos son convertidos en productos aprovechables como el biogás y el biol. En los proyectos piloto que se presentan, ubicados en Perú, hasta la fecha se han implementado alrededor de 20 biodigestores familiares, en comunidades rurales de la zona de Cusco y de Cajamarca. La mayoría se encuentran a 3000-4000 m.s.n.m, y la temperatura dentro del biodigestor oscila entre 10-23 ºC gracias a la implementación de invernaderos que permiten amortiguar las oscilaciones térmicas día-noche. Los biodigestores producen aproximadamente 0.2 m 3 biogas m -3 biodigestor día -1 , dentro del rango psicrofílico, que con biodigestores de 5 m 3 es suficiente para cocinar 3-4 h diarias, sustituyendo los combustibles tradicionales. El coste de construcción de los biodigestores (40 €/ m 3 ) seria asumible, al menos parcialmente, por familias campesinas. A nivel financiero, la instalación es más viable cuando el biogás sustituye un combustible con valor de mercado como el gas propano, resultando en un payback de 2 años y 8 meses; o bien cuando permite elaborar productos con valor añadido (quesos, yogures, mermeladas, etc.). Por otro lado, la eficacia del sistema también podría aumentar mediante la integración del biodigestor en la granja, conectándolo con la letrina y usando el biol como fertilizante para los cultivos. Estas aproximaciones son objeto de trabajos futuros. INTRODUCCIÓN Biodigestores familiares de bajo coste La digestión anaerobia, o biodigestión, es una tecnología que permite mejorar el aprovechamiento energético tradicional de la biomasa, tanto desde el punto de vista medioambiental, como social y económico . Al mismo tiempo, permite una gestión
Uggetti, E.; Pedescoll, A.; Llorens, E.; Ferrer, I.; Castellnou, R.; Molist, J.; Garcia, J. 7th International Workshop on Nutrient Cycling and Retention in Natural and Constructed Wetlands Presentació treball a congrés
Uggetti, E.; Pedescoll, A.; Llorens, E.; Ferrer, I.; Castellnou, R.; Molist, J.; Garcia, J. 7th International Workshop on Nutrient Cycling and Retention in Natural
and Constructed Wetlands p. 1-2 Presentació treball a congrés
En el contexto del tratamiento de lodos de depuradora, los sistemas con lechos de macrófitos resultan particularmente adecuados, sobretodo en depuradoras pequeñas (<2000 hab.-eq.) que no disponen de tratamientos convencionales, debido a su bajo coste y a su baja demanda de energía y mantenimiento. Estos sistemas, gracias a la acción de las plantas, deshidratan el lodo permitiendo la reducción su volumen. Además de la deshidratación, se da un cierto grado de estabilización de la materia orgánica, que podría permitir la reutilización del producto final en actividades agrícolas.