Suchergebnisse

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)

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)