Optimization of multi-stage thickening of biomass in a demonstrative full–scale microalgae-based wastewater treatment system

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 ReviewedPostprint (published version

Influence of liquid-to-biogas ratio and alkalinity on the biogas upgrading performance in a demo scale algal-bacterial photobioreactor

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.Peer ReviewedPostprint (published version

Advanced biokinetic and hydrodynamic modelling to support and optimize the design of full-scale high rate algal ponds

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 wastewaterAuthors 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 ReviewedPostprint (published version

Factores Críticos que dificultan la Aplicación de Revenue Management en Hoteles Urbanos

Con este trabajo se pretenden determinar los factores que influyen de forma significativa como barreras para la aplicación de Revenue Management –RM- (también denominado Yield Management). Con este objetivo, se analiza la influencia de su conocimiento, implantación y de la dimensión del hotel, sobre las dificultades experimentadas por los hoteles en dos momentos, al inicio del proceso de la implantación de RM y en el momento actual. El estudio se realiza sobre el censo de hoteles de cuatro y cinco estrellas de la provincia de Sevilla. Se ha constatado, de un lado, la influencia significativa que ejerce la disponibilidad de un software de RM sobre las dificultades al inicio del proceso de implantación y, de otro, la influencia también significativa de la implantación de RM, dimensión del hotel, pertenencia a una cadena y dimensión de la cadena, sobre las dificultades a las que actualmente deben enfrentarse los hoteles para la aplicación de RM. Adicionalmente se han identificado aquellos obstáculos que resultan críticos a la hora de aplicar RM en el sector hotelero dependiendo del perfil del hotel. Con ellos el establecimiento podrá hacer una evaluación previa de sus fortalezas, debilidades y áreas de actuación prioritarias para la implantación de RM.With this work we aim to identify factors that significantly influence as barriers to the implementation of Revenue Management -RM- (also called yield management). In this way, the influence of its knowledge, its implementation and the size of the hotel is analyzed, on the difficulties experienced by hotels at two specific monents, at the beginning of the process of the implementation of RM and at present. The study was performed on the census of hotels of four and five star hotels in the province of Seville. It was found, on the one hand, the significant influence of the availability of a RM software on the difficulties at the beginning of the implementation process and, secondly, also significantly influence the implementation of RM, size of hotel, membership brand and size of the chain, on the difficulties they face currently hotel RM application. Additionally, those obstacles have been identified that are critical to the RM implementation in the hotel sector depending on the profile of the hotel. With them, the hotel may make a preliminary assessment of their strengths, weaknesses and areas for priority action for implementation of RM

Sludge treatment wetland for treating microalgae digestate grown in agricultural runoff: a technical, economic, and environmental assessment

The management and disposal of wastewater treatment sludge can be a costly and resource-intensive process. To provide a cost-effective and sustainable alternative, Sludge Treatment Wetlands (STW) have emerged as a viable solution for enhancing sludge quality through dewatering and biodegradation. In this study, the effectiveness of a full-scale STW for stabilizing and dewatering digested microalgal biomass from a domestic and agricultural wastewater treatment system was evaluated. The properties of the treated digestate in the STW were assessed after 35 weeks of operation and a resting period of 4 weeks. The dry matter content was found to be 12.8%, and the average macronutrient content was K: 3.8 mg/g DW, P: 4.9 mg/g DW, and Ca: 95 mg/g DW. The highest contents of micronutrients were for Fe: 7.8 mg/g DW and Mg: 7.6 mg/g DW, while heavy metals and pathogen contents were below the EC limits for sewage sludge reuse in agriculture. The STW was found to be a cost-effective and environmentally friendly option for treating mixed wastewater-based sludge for land application. The STW outperformed reference systems using centrifuge dewatering techniques, particularly in terms of eutrophication potential and acidification potential. However, the STW’s economic performance was slightly worse than that of the dewatering system in terms of unit production cost. This study is the first in the literature to investigate the use of STW for treating digested microalgae and its possible reuse in arable land, suggesting that STW infrastructures have great potential for the development of sustainable and eco-friendly sludge treatment technologies.This research was funded by the European Commission (H2020 project INCOVER, GA 689242). E. Gonzalez-Flo would like to thank the European Union-Next Generation EU, Ministry of Universities and Recovery, Transformation and Resilience Plan for her research grant [2021UPF-MS12]. A. Ortiz would like to thank the European Union Next-Generation EU, Ministry of Universities and Recovery, Transformation and Resilience Plan for his research grant [2022UPC-MSC-94120].Peer ReviewedBy Eva Gonzalez-Flo 1 , Antonio Ortiz 2, Carlos A. Arias 3, Rubén Díez-Montero 2,4, Norbert Kohlheb 5, Ulf-Henning Schauser 6, Joan García 2 and Peder K. S. Gregersen 7. 1 GEMMA-Group of Environmental Engineering and Microbiology, Department of Civil and Environmental Engineering, Escola d’Enginyeria de Barcelona Est (EEBE), Universitat Politècnica de Catalunya-BarcelonaTech, Av. Eduard Maristany 16, Building C5.1, E-08019 Barcelona, Spain 2 GEMMA-Group of Environmental Engineering and Microbiology, Department of Civil and Environmental Engineering, Universitat Politècnica de Catalunya-BarcelonaTech, c/Jordi Girona 1-3, Building D1, E-08034 Barcelona, Spain 3 Department of Biology, Aarhus University, 8000 Aarhus, Denmark 4 GIA-Group of Environmental Engineering, Department of Water and Environmental Sciences and Technologies, Universidad de Cantabria, Avda. Los Castros s/n, 39005 Santander, Spain 5 Helmholtz-Zentrum Fuer Umveltforschung GMBH–UFZ (“UFZ”), 04318 Leipzig, Germany 6 N.A.T., Ingenieurökologisches Planungsbüro, 24340 Eckernförde, Germany 7 Center for Recirkulering v/Peder S, 6870 Gregersen Ölgod, DenmarkPostprint (published version

Mechatronic Model of a Compliant 3PRS Parallel Manipulator

Compliant mechanisms are widely used for instrumentation and measuring devices for their precision and high bandwidth. In this paper, the mechatronic model of a compliant 3PRS parallel manipulator is developed, integrating the inverse and direct kinematics, the inverse dynamic problem of the manipulator and the dynamics of the actuators and the control. The kinematic problem is solved, assuming a pseudo-rigid model for the deflection in the compliant revolute and spherical joints. The inverse dynamic problem is solved, using the Principle of Energy Equivalence. The mechatronic model allows the prediction of the bandwidth of the manipulator motion in the 3 degrees of freedom for a given control and set of actuators, helping in the design of the optimum solution. A prototype is built and validated, comparing experimental signals with the ones from the model.Authors would like to thank the Ministerio de Ciencia e Innovación of the Spanish government for funding the project PID2019-105262RB-I00

Circuito integrado para comunicaciones en sistemas de ascensores

El circuito ASIC descrlto es una unidad de comunicaciones destinada a sistemas de ascensores. Este diseño reduce en gran medida de las necesidades de cableado que encarece la instalación de los sistemas de ascensores. Por un único canal de fibra óptica pueden comunicarse hasta un máximo de 31 chips, cada uno de los cuales controla los distintos contactos, pulsadores e identificadores de piso y cabina. El circuito se encuentra actualmente en producción con resultados satisfactorios. Esta realización se enmarca dentro de la acción GAME (acción especial del programa ESPRIT) y ha sido desarrollado en colaboración con la empresa de Mecanismos y Accesorios MAC S.A

Nutrient removal from agricultural run-off in demonstrative full scale tubular photobioreactors for microalgae growth

The objective of this paper is to present the design, construction and operation (during one year) of 3 full scale semi-closed, horizontal tubular photobioreactors (PBR, 11.7 m3 of volume each) used to remove nutrients of a mixture of agricultural run-off (90%) and treated domestic wastewater (10%). PBRs were located outdoor and have 2 paddlewheels (engines of 0.25 kW) to ensure the movement of the mixed liquor. The microalgal biomass produced in the PBRs was harvested in a static lamella settling tank in which a polyaluminium chloride coagulant is applied. Each PBR treated in average 2.3 m3/d, being the actual mean hydraulic retention time 5 d. PBRs were submitted to strong seasonal changes regarding solar radiation and temperature, which had a direct impact in the activity of microalgae and the efficiency of the system. Higher mixed liquor pH values were registered in summer (daily average > 10). These high values were not observed in the effluents because the system was designed to discharge the mixed liquor (effluent) only at the end of night, when pH reached the lowest daily values (around 8.5). Most of the influent and effluent nitrogen content was inorganic (average of 9.0¿mg¿N/L and 3.17 mg N/L, respectively), and in the form of nitrate (62% and 50%, respectively). Average nitrogen removal efficiency was 65%, with values of around 90% in summer, 80% in autumn, 50% in winter and 60% in spring. Most of the influent and effluent phosphorus content was in the form of orthophosphate. Influent average was 0.62 mg P/L, but with great variations and in a considerable number of samples not detected. Removal efficiency (when influent values were detected) was very high during all the study, usually greater than 95%, and there were not clear seasonal trends for efficiency as observed for TIN. Volumetric biomass production greatly changed between seasons with much lower values in winter (7 g VSS (volatile suspended solids)/m3·d) than in summer (43 g VSS/m3·d). Biomass separation efficiency of the settler was very good in either terms of turbidity and total suspended solids, being most of the time lower than 5 UNT and 25 mg/L, respectively. Overall this study demonstrated the reliable and good effectiveness of microalgae based technologies such as the PBR to remove nutrients at a full scale size.Peer ReviewedPostprint (author's final draft

ASITRON: ASIC for indirect vector control of induction motors with fuzzy logic based speed regulation

This paper presents ASITRON, an integrated solution for the vector control of induction motors. This ASIC is a micro-system that integrates, in a chip, all the logic required by the indirect vector control method. ASITRON implements a PWM based current control loop, the measure of speed based on a biphase pulse signal encoder, a fuzzy logic based speed and position outer control loop and a microprocessor external parallel interface. A built-in 64-rules fuzzy logic controller can be programmed to deal with the speed or position outer control loop. This integrated solution is the essential part of a compact, high performance, industrial control system for elevators