Suchergebnisse

In this study, a mixed nitrogen-fixing soil cyanobacterial culture was tested to treat municipal wastewater and produce total carbohydrates in a one-stage operation. Four photobioreactors were operated in semi-continuous mode for 30 days, evaluating the effect of different hydraulic retention times and nutrients and carbon loads on nutrients and organic matter removal, biomass composition, and carbohydrate production. One photobioreactor operated at a hydraulic retention time of 10 d with diluted 2:1 wastewater with distilled water, and other photobioreactors worked at 10 d, 8 d, and 6 d of hydraulic retention times with undiluted sewage. The results evidenced that high hydraulic retention time and low nutrients load achieved the highest removal efficiencies in total nitrogen >95%, total phosphorus 35–78%, total organic carbon >93%, and total inorganic carbon >82%. These high removals led to nitrogen limitation that stimulated a continuous carbohydrate accumulation of up to 48%. Also, a biomass production of 0.05–0.07 mg L−1 d−1 dominated by easy-settling flocs of filamentous nitrogen-fixing cyanobacteria was achieved. Otherwise, lower hydraulic retention time and thus high nutrients load promoted carbon depletion, which led to lower nitrogen and phosphorus removals, low biomass production and contamination of green algae species. The results of this study highlight the nutritional and operational mechanisms of soil microorganisms and strategies to simultaneously clean waste streams and produce valuable by-products. ; Authors are grateful to the Spanish Ministry of Science, Innovation and Universities (MCIU), Research National Agency (AEI), European Regional Development Fund (FEDER) for the AL4BIO project (RTI2018-099495-B-C21) and to the Government of Catalonia (Consolidated Research Group 2017 SGR 1029). E. Uggetti would like to thank the Spanish Ministry of Industry and Economy for the research grants (RYC2018-025514-I). Authors kindly thank Nicoló Brena, Joan Nicolás, Ariadna Muñoz, María Valldosera for the experiment deployment and Patrick U. Okoye for improving the English of the manuscript. ; Peer Reviewed ; Postprint (author's final draft)

This study gathers the results of the operation and optimization of the thickening of microalgal biomass produced at demonstrative scale in photobioreactors fed with agricultural runoff and domestic wastewater. The optimization was conducted during two months. The system consisted in two gravity thickeners connected in series in a multi-stage approach. The objective of thickening was to concentrate the microalgae grown in photobioreactors (total solids (TS) concentration of 0.1–1 g/L) into a biomass with 20 g/L of TS, which was considered optimal for the subsequent anaerobic digestion process. First, the utilization of one single thickener alone allowed to achieve a concentration factor (CF) of 1.9 and recovery efficiency (RE) of 28%. However, the final concentration of TS in the thickened biomass (6.4 g/L) was still much lower than the target concentration. The installation of the second thickener connected in series with the first one significantly improved the overall performance. Indeed, a TS concentration of 26.5 g/L was finally achieved, with an overall CF of 3.6. The results of the study suggest that the multi-stage thickening process is a suitable strategy and it is highly advisable to achieve a successful microalgal biomass thickening at full-scale. In addition, other three points have been identified as key factors to be taken into account for biomass tickening: proper adjustment of the purge flowrate, coordination between purges times and volumes in the different stages, and proper adjustment of the operation of the scrapers. ; The authors would like to thank the European Commission (INCOVER, GA 689242) and the Government of Catalonia (Consolidated Research Group 2017 SGR 1029) for their financial support. E. Uggetti and R. Díez-Montero would also like to thank the Spanish Ministry of Industry and Economy for their research grants (RYC2018-025514-I and IJC2019-042069-I, respectively). ; Peer Reviewed ; Postprint (published version)

High rate algal ponds (HRAP) are known for their suitability to treat wastewater and to produce microalgal biomass, which can be converted into bioproducts. However, full-scale application of HRAP is still limited to few cases, and design procedures are not consolidated or standardized. In this study, a demonstrative-scale HRAP system for secondary wastewater treatment to be implemented in India (treatment capacity of 50 m3·d-1) has been designed combining conventional dimensioning techniques and advanced modelling tools. The objective of the study was to assist, verify and optimize the conventional dimensioning of the secondary HRAP by means of simulations predicting the behaviour of the system in the specific local conditions under different configurations and operational strategies. Biokinetic modelling and hydrodynamic analysis using Computational Fluid Dynamics (CFD) were carried out. The simulations performed with the biokinetic model showed that the optimal hydraulic retention time to enhance nutrient removal and biomass production is 4 days. For the hydrodynamic modelling, a 3D model of the HRAP was built to simulate the hydrodynamic behaviour of 36 different designs. Simulations allowed quantifying the presence of low velocity zones as well as the land use efficiency of the different designs in terms of the useful area vs. the total occupied area. Two baffles and tear-shapes with a diameter equal to ¼ of the channel width was the most efficient configuration. Moreover, a technical–economic assessment of the system was carried out, resulting in an investment cost of 483 € per population equivalent and an operational cost of 0.19 € per m3 of treated wastewater ; Authors would like to thank the European Commission for the financial support (PAVITR project, GA 821410) and the Department of Sciences and Technology from Government of India for the financial support (GA DST/IMRCD/India-EU/Water Call2/PAVITR/2018). Authors are also grateful to the Government of Catalonia (Consolidated Research Group 2017 SGR 1029). E. Uggetti and R. Díez-Montero would also like to thank the Spanish Ministry of Industry and Economy for their research grants (RYC2018-025514-I and IJC2019-042069-I, respectively). ; Peer Reviewed ; Postprint (published version)

Appropriate hydrodynamic conditions are crucial in photobioreactors (PBR) in order to prevent sedimentation of microalgal biomass and to ensure the uniform exposure of microalgae cells to light and nutrients. Hydrodynamic conditions are also important to guarantee efficient mass transfer and proper shear stress on the transparent walls of the PBR, which can avoid the formation of undesired biofilm. Numerical simulations based on Computational Fluid Dynamics (CFD) can assist to improve the hydrodynamic design and optimization of PBRs. In this study, CFD was used as a tool to investigate the hydrodynamics of a hybrid horizontal tubular PBR designed for microalgae cultivation and wastewater treatment. The flow regime, average circulation time and shear stress distribution in the tubes were evaluated. To establish the reliability of the simulation study, the CFD model was validated using tracer experimental tests and ultrasonic flow meter measurements. Results showed that the hydrodynamic conditions in the tubes resembled plug flow with small axial dispersion. The simulated velocity profile in the tube corresponded to the analytical velocity profile based on experimental data. Simulations also showed that, even increasing flow velocities, low velocity zones were present in some zones of the PBR. The shear stress distribution in the tubes showed values higher enough to reduce or avoid the formation of biofilm, nevertheless the shear stress value is not sufficient to remove the already formed biofilm. Based on the numerical investigation and practical evaluation, this study demonstrated that CFD is a useful tool to optimize PBR design and operation in order to enhance microalgae production and boost the scale-up of this technology. ; This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic under OP RDE grant number CZ.02.1.01/0.0/0.0/16_019/0000753 "Research centre for low-carbon energy technologies". This research was supported by Student Grant Competition of CTU as part of grant no. SGS20/118/OHK2/2T/12. Authors would like to thank the European Commission [project INCOVER, GA 689242] and the Government of Catalonia [Consolidated Research Group 2017 SGR 1029] for their financial support. E. Uggetti and R. Díez Montero would like to thank the Spanish Ministry of Industry and Economy for their research grants [RYC2018-025514-I and IJC2019-042069-I, respectively]. ; Peer Reviewed ; Postprint (published version)

The present work evaluated polyhydroxybutyrate (PHB) and carbohydrates production by wastewater borne cyanobacteria at demonstrative-scale (three photobioreactors (PBR) of 11.7 m3 each), using agricultural runoff as feedstock. Agricultural runoff was fed to PBR1, which was devoted to cyanobacteria selection and biomass growth. In PBR2, inorganic carbon was added in a feast and famine regime to favour PHB-accumulating microorganisms. Finally, inorganic carbon was continuously added in PBR3 to boost PHB accumulation. A high removal efficiency of 95% and 99% for total nitrogen and phosphorus was obtained, respectively. Cyanobacteria were successfully selected and outcompeted green microalgae. Results suggested that a minimum inorganic carbon concentration was needed to accumulate PHB while carbohydrates were accumulated only with CO2 additions. Maximum concentrations of 4.5%VSS and 69%VSS for PHB and carbohydrates were obtained. Overall, this study shows at demonstrative-scale the potential of cyanobacteria to produce PHB within a wastewater biorefinery concept. And it gives insight on the strategies needed to produce PHB with cyanobacteria at massive scale. ; This research was funded by the European Union H2020 Research and Innovation program [INCOVER, GA 689242] and by the Spanish Ministry of Science, Innovation and Universities (MCIU), the Research National Agency (AEI), and the European Regional Development Fund (FEDER) [AL4BIO, RTI2018-099495-B-C21]. M.J. García and R. Díez-Montero would like to thank the Spanish Ministry of Economy and Competitiveness for their research grants (IJCI-2017-34601 and FJCI-2016-30997, respectively). Estel Rueda would like to thank the Spanish Ministry of Education, Culture and Sport (FPU18/04941) for her grant. Authors would like to thank Simone Rossi for his support during the experiment deployment. ; Peer Reviewed ; Postprint (author's final draft)

Producción Científica ; The influence of the liquid-to-biogas ratio (L/G) and alkalinity on methane quality was evaluated in a 11.7 m3 outdoors horizontal semi-closed tubular photobioreactor interconnected to a 45-L absorption column (AC). CO2 concentrations in the upgraded methane ranged from <0.1 to 9.6% at L/G of 2.0 and 0.5, respectively, with maximum CH4 concentrations of 89.7% at a L/G of 1.0. Moreover, an enhanced CO2 removal (mediating a decrease in CO2 concentration from 9.6 to 1.2%) and therefore higher CH4 contents (increasing from 88.0 to 93.2%) were observed when increasing the alkalinity of the AC cultivation broth from 42 ± 1 mg L−1 to 996 ± 42 mg L−1. H2S was completely removed regardless of the L/G or the alkalinity in AC. The continuous operation of the photobioreactor with optimized operating parameters resulted in contents of CO2 (<0.1%–1.4%), H2S (<0.7 mg m−3) and CH4 (94.1%–98.8%) complying with international regulations for methane injection into natural gas grids. ; Junta de Castilla y León y EU- FEDER (UIC 71 y CLU-2017-09) ; Ministerio de Ciencia, Innovación y Universidades ( research Grants IJCI-2014-21594 y FJCI-2016-30997) ; European Union's Horizon 2020 research and innovation program. grant agreement no. 689242.

The present study evaluated the capacity of a semi-closed, tubular horizontal photobioreactor (PBR) to remove pesticides from agricultural run-off. The study was carried out in summer (July) to study its efficiency under the best conditions (highest solar irradiation). A total of 51 pesticides, including 10 transformation products, were selected and investigated based on their consumption rate and environmental relevance. Sixteen of them were detected in the agricultural run-off, and the estimated removal efficiencies ranged from negative values, obtained for 3 compounds, namely terbutryn, diuron and imidacloprid, to 100%, achieved for 10 compounds. The acidic herbicide MCPA was removed by 88% in average, and the insecticides 2,4-D and diazinon showed variable removals, between 100% and negative values. The environmental risk associated to the compounds still present in the effluent of the PBR was evaluated using hazard quotients (HQs), calculated using the average and highest measured concentrations of the compounds. HQ values > 10 (meaning high risk) were obtained for imidacloprid (21), between 1 and 10 (meaning moderate risk) for 2,4-D (2.8), diazinon (4.6) and terbutryn (1.5), and <1 (meaning low risk) for the remaining compounds diuron, linuron and MCPA. The PBR treatment yielded variable removals depending on the compound, similarly to conventional wastewater treatment plants. This study provides new data on the capacity of microalgae-based treatment systems to eliminate a wide range of priority pesticides under real/environmental conditions. ; This research was funded by European Union's Horizon 2020 research and innovation program within the framework of the INCOVER project (GA 689242) and WATERPROTECT project (727450); by the Spanish Ministry of Science, Innovation and Universities, the Research National Agency (AEI), and the European Regional Development Fund (FEDER) within the project AL4BIO (RTI2018-099495-B-C21), and by the Government of Catalonia (Consolidated Research Group 2017 SGR 01404-Water and Soil Quality Unit). M.J. García-Galán, E. Uggetti and R. Díez-Montero would like to thank the Spanish Ministry of Economy and Competitiveness for their research grants (IJCI-2017-34601, RYC2018-025514-I and FJCI-2016-30997, respectively). ; Peer Reviewed ; Postprint (author's final draft)