In this study, I examined the influence of hydrological seasonality on spatiotemporal variation of algal biomass and shrimp abundance on sandbanks of the Cinaruco River in southwestern Venezuela. Seasonal variations of abiotic and biotic variables in the Cinaruco were driven by the hydrological regime. During the highwater periods, river sites in the main channel and lagoon sites were similar in water physicochemical variables and algal biomass. In contrast, physicochemical variables and algal biomass differed between river and lagoon sites during the low-water period. The absence of flow in lagoons and consistently low algal biomass on river sandbanks were the most important features of the spatial variability between main-channel and lagoon sandbanks during low-water phases. Benthic algal biomass was highly uniform at small spatial scales and significantly heterogeneous at large spatial scales. In the second major part of this dissertation, I found a relatively species-rich shrimp assemblage with seven species inhabiting the sandbanks of the Cinaruco. I also observed clear patterns of temporal and spatial variation in shrimp abundance on the Cinaruco sandbanks. Abundance of shrimp on the sandbanks presented remarkable diel variation, showing almost exclusive use of this habitat at nights. Seasonally, shrimp were more abundant during rising- and falling-water periods, when rapid changes of environmental conditions occur. Shrimp abundance was high on those sandbanks with absence of troughs and presence of submerged vegetation. These environmental features presumably promote colonization/establishment and survival/persistence of shrimp in the sandbanks. In a patch-dynamic view of communities, a mobility control model seems to apply to shrimp of the sandbanks in the Cinaruco during the period of rapid changes in hydrology and habitat structure. During low-water periods, when habitat structure of sandbanks is relatively constant, low shrimp abundance appears to be heavily controlled by high fish predation. The annual flood regime of the Cinaruco, which drives the concentrations of dissolved materials, affects material interchanges between aquatic and terrestrial systems, and modifies aquatic habitat structural complexity, is responsible for creating strong patterns of seasonal and spatial variation in benthic algal crops and shrimp abundance on the sandbanks of this large floodplain river.

The West Florida Shelf (WFS), typically characterized as being oligotrophic, is one of the most productive continental shelves in the United States. In addition to supporting a large fishing industry, the WFS also supports high biomass blooms of the toxic dinoflagellate Karenia brevis. Because of the large ecological and economic impacts these blooms have on the area, the ECOHAB: Florida program was developed to gain a better understanding of red tides and their initiation, maintenance, and dispersal. This interdisciplinary program consisted of monthly cruises from June 1998 through December 2001, with a hiatus from January through March of 2001. Hydrography, nutrients, chlorophyll a, phaeopigments, and a wide variety of other factors were measured during the cruises. In this paper chlorophyll a and phaeopigment concentration, nutrients, and hydrographic data were examined to explain the temporal and spatial distribution of chlorophyll on the shelf. Average surface chlorophyll values were 0.55 mg/m 3 with near bottom values averaging 0.85 mg/m 3. Chlorophyll was found to be highest near the estuaries of Tampa Bay and Charlotte Harbor with a decreasing gradient seaward. Near bottom chlorophyll values were generally two to fourfold greater than surface values. Midshelf stations (35- 50 m) were characterized by high near bottom chlorophyll, whereas the offshore stations (86-200 m) were characterized by a subsurface chlorophyll maximum ranging between 40 to 80 m deep. Nutrients were generally low across the shelf except for 1998 when a subsurface intrusion of nutrient rich slope water reached to the 20 m isobath. Temperatures ranged from 14.00 ° C to 31.47° C. Salinity ranged from 30.5 to 37.50 in the study area. Four blooms of Karenia brevis, lasting several months, contributed to the high chlorophyll concentrations along the inner shelf. Maximum chlorophyll concentrations of 27.10 mg/m 3 were a result of the October 1999 to March 2000 red tide. Blooms of Trichodesmium and diatoms also were contributors to patterns seen on the shelf. Maximum chlorophyll values were generally highest in the late summer and fall except for offshore values which showed little to no seasonality. Inshore of the 50 m isobath, average phaeopigments comprised from 43 to 68 percent of the measured Chl a, while offshore values were from 68 to over 100 percent. Inshore chlorophyll distributions were attributed to riverine and estuarine flux of nutrients, localized upwelling, and recycling of nutrients aided by salinity and temperature fronts. Midshelf distributions were attributed to the movement of biologically important material through the bottom Ekman layer from offshore to the inshore regions of the shelf. Offshore distributions were attributed to Loop Current upwelling and synoptic scale processes associated with seasonal meteorological forcing.

This thesis describes a geographically- and temporally-resolved, integrated biological and engineering model that estimates algal biomass and lipid production under resource-limited conditions with hourly and county resolution. Four primary resources are considered in this model: sunlight, carbon dioxide, water, and land. The variation in quantity and distribution of these resources affects algae growth, and is integrated into the analysis using a Monod model of algae growth, solar insolation data, and published values for water, carbon dioxide, and land availability. Finally, lipid production is calculated by assuming oil content based on dry weight of the biomass. The model accommodates a range of growth and production scenarios, including water recycling, co-location with wastewater treatment plants and coal-fired generators, and photobioreactor type (open pond or tubular), among others. Results for every county in Texas indicate that between 86 million and 2.2 billion gallons of lipids per year can be produced statewide for the various growth scenarios. The analysis suggests that algal biomass and lipid production does indeed vary geographically and temporally across Texas. Overall, most counties are water-limited for algae production, not sunlight or carbon dioxide-limited. However, there are many nuances in biomass and lipid production by county. Counties in west Texas are typically not solar- or land-limited, but are constrained by either water or carbon dioxide resources. Consequently, counties in east Texas are limited by either water, or land (depending on the fraction of water recycling). Varying carbon dioxide concentration results in higher growth rates, but not always increased biomass and lipid production because of limitations of other resources in each county. / text

Resource-efficient technologies are essential for economically viable biodiesel production. This work focuses on conversion of microalgal lipids and vegetable oils into fatty acid alkyl esters or biodiesel. Transesterification of waste cooking oil (WCO) and extractive-transesterification of wet microalgal biomass were investigated using microwave and ultrasound irradiations through several process parametric evaluation studies to elucidate the effects of different alcohols and catalyst types (homogeneous and heterogeneous), reaction time, and reaction temperatures. First, a brief overview of process steps involved in microalgal biodiesel production and associated energy consumption and research needs were discussed. Next, energy analysis of microalgal biocrude production via extractive-transesterification under microwave and ultrasound irradiations (individually) was performed. Then, the synergistic effect of microwave and ultrasound irradiations on extractive-transesterification of microalgal lipids was evaluated through a process optimization study using response surface methodology to determine the best process conditions. For this study, a maximum biocrude conversion of 51.2% was obtained when 20 g of algal paste was treated with 30 mL methanol, 1 wt.% catalyst, 7 min reaction time, and 140 W for MW and US (280 W total). Further, biocrude yield kinetics study revealed that the activation energy for this reaction was around 17, 298 J mol-1 K-1. A series of experimental studies were conducted to understand the roles and effects of various process related conditions including the power output and power density of microwave and ultrasound irradiations in biodiesel production. The two non-conventional heating techniques were compared for their process intensification effects. Ultrasound was applied either in continuous or pulse mode. Pulse sonication was found to be more suitable for simple transesterification reaction of WCO with a 98% biodiesel yield in 2.5 min (9:1 methanol to oil ratio, 1.25% catalyst, and 150 W power output) over 82% yield for continuous sonication under the same conditions. Followed by this, a detailed study was conducted to determine optimum pulse (ON and OFF time) sonication conditions. A 99% conversion yield was obtained for a pulse ON-OFF combination of 7s-2s. Additionally, the effect of different alcohols (ethanol, methanol, and ethanol-methanol mixtures) using pulse sonication was evaluated.

Made available in DSpace on 2016-08-10T10:44:52Z (GMT). No. of bitstreams: 1 LUCAS CASSIANO GONCALVES PRUDENTE SILVA.pdf: 751405 bytes, checksum: 3c986fe2096faa277b68c1b41c862aff (MD5) Previous issue date: 2015-02-25 / Changes in the aquatic environment with respect to water quality tends to generate an environmental imbalance that influences us dependent beings that environment. This study aims to evaluate and compare 31 streams belonging to the sub-basins of the Meia Ponte, Piracanjuba and Santa Maria the physicochemical characteristics (nitrate, phosphate, conductivity, pH, turbidity, temperature, dissolved oxygen), hydrological (water speed ) and biological components of water (algal biomass) by sub-basin evaluate the relationship between algal biomass, with the concentration of nitrate and phosphate, and finally to evaluate the relationship between the abundance of fish with nitrate, phosphate , conductivity, pH, turbidity, algal biomass, temperature, dissolved oxygen and water velocity, considering all the sampled sub-basins. In each stream was given a 100m stretch where were the measurements of water features using handheld devices, except for nitrate, phosphate and algal biomass (chlorophyll α) whose concentrations were determined in the laboratory from samples water through the spectrophotometry method. The results showed that there are significant differences in the pH (between the sub-basin of the river Santa Maria and this Piracanjuba and the Half Bridge) and turbidity (between sub-basins Santa Maria and Meia Ponte), but was not found no relationship between algal biomass with the physical, chemical and hydrological aspects, however, was shown a relative abundance of fish with pH and conductivity. / Alterações no ambiente aquático no que tange à qualidade da água tende a gerar um desequilíbrio ambiental que influencia nos seres dependentes desse ambiente. Este trabalho objetiva avaliar e comparar em 31 riachos pertencentes às sub-bacias dos rios Meia Ponte, Piracanjuba e Santa Maria as características físicoquímicas (nitrato, fosfato, condutividade, pH, turbidez, temperatura, oxigênio dissolvido), hidrológicas (velocidade da água) e os componentes biológicos da água (biomassa de algas) por sub-bacia, avaliar a relação entre a biomassa das algas, com a concentração de nitrato e fosfato, e por fim avaliar a relação entre a abundância de peixes com o nitrato, fosfato, condutividade, pH, turbidez, biomassa de algas, temperatura, oxigênio dissolvido e velocidade da água, considerando todas as sub-bacias amostradas. Em cada riacho foi determinado um trecho de 100m, onde foram realizadas as medições das características da água utilizando-se equipamentos portáteis, exceto para o nitrato, fosfato e biomassa de algas (clorofila α) cujas concentrações foram determinadas em laboratório a partir de amostras de água através do método de espectrofotometria. Os resultados obtidos mostraram que existem diferenças significativa para o pH (entre a sub-bacia do rio Santa Maria e esta do Piracanjuba e Meia Ponte) e para a turbidez (entre as sub-bacias Santa Maria e Meia Ponte), porém não foi encontrada nenhuma relação entre a biomassa de algas com os aspectos físico-químicos e hidrológico, contudo, foi evidenciado uma relação da abundância de peixes com pH e a condutividade.

Ettlia oleoabundans, a freshwater green microalga, was grown under different environmental conditions to study its growth, lipid yield and quality for a better understanding of the fundamental physiology of this oleaginous species. E. oleoabundans showed steady increase in biomass under low temperature and low light intensity, and at high temperature lipid cell content significantly increased independent of nitrate depletion. Studies on light quality showed that red light treatment did not change the biomass concentration, but stimulated lipid yield especially oleic acid, the most desirable biodiesel precursor. Moreover, no photoreversibility in lipid production was observed when applying alternating short-term red and far-red lights, which left the phytochrome effect still an open question. In addition, carbon dioxide enrichment via an air sparging system significantly boosted exponential growth and increased carbon conversion efficiency. Finally, a practical study demonstrated the feasibility of growing E. oleoabundans for high lipid production using a diluted agricultural anaerobic waste effluent as the medium. Together, these studies showed the potential of E. oleoabundans as a promising high yield feedstock for the production of high quality biodiesel.

With the continuous improvement in knowledge and health risks associated with heavy metal expulsion, government environmental agencies are continuously reducing the legal disposal limits. However, the demand for items like IPods or energy-efficient appliances containing heavy metal like copper is on the rise. Whether from commercial or residential areas, heavy metals are known to have toxic effects on humans, animals, and/or ecosystems; hence, their removal is necessary part of preserving our environment. With the rising cost of natural resources, biological species have proven to be viable alternatives in the jet fuel and biodiesel industries. Algal biomass is widely considered economical because of its renewable, biodegradable, noncompetitive, and nontoxic properties. Currently, algae are being grown on waste water for the lipid; this research involves taking the left over or lipid-extracted algae (LEA) for utilization as a biosorbant to remove heavy metals from wastewater. Down selection via batch processes showed that Chlorella sorokianna and its associated lipid-extracted algae (LEA) demonstrated similar adsorption capacities of copper (II) as three current-in-use ion exchange resins. A feasibility study proved that the LEA was an economically realistic means to remove copper (II) from effluent. The LEA biomass is capable of a maximum adsorption of 14.36 ± 0.27 mg of copper (II) per gram of dry biomass for six regeneration, sorption-desorption, cycles with nitric acid. Using SEM and FTIR, the LEA is capable of ion exchange electrostatic interaction with various surface sites of carboxyl, hydroxyl, and metal groups. Next, the batch process was used to fabricate a lab-scale continuous column process much like ion exchange or activated carbon columns in a waste water treatment plant. Using the continuous systems' kinetics and cycle life, a cost analysis was performed on a plant scale column to reduce copper (II) in wastewater for recovery at a later date, which would yield cost saving over the life of columns. To install three LEA columns prior to ion exchange in a waste water treatment plant, the total capital expense is $1.03 million for a one year time line. The bidirectional flow columns are meant as pretreatment prior to ion exchange columns. The LEA columns provide a waste water treatment plant a sustainable, greener and cheaper alternative to offset costs associated with purifying waste water.

Orientadora: Profa. Dra. Ana Maria Pereira Neto / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Energia, 2014. / Este trabalho avaliou o potencial energético da biomassa de Chlorella minutissima cultivada em condição autotrófica em meio Guillard f/2 e mixotrófica com o mesmo meio e adição de glicose em diferentes condições: I) adição fracionada de 0,2 g/L de glicose com um intervalo de 48h para atingir a adição total de 0,4 g/L; II) adição de 0,2 g/L de glicose em única dose no início do cultivo; III) adição de 0,2 g/L de glicose em única dose após 72h do início do cultivo e IV) adição fracionada de 0,05 g/L de glicose, após 72h de cultivo, seguida de três adições em intervalos de 48h, até atingir a adição total de 0,2 g/L. As curvas de crescimento dos cultivos foram determinadas a partir do monitoramento diário da densidade celular. A produtividade e os teores de carboidratos, clorofila-a, carotenoides, poder calorífico superior e análises elementar e imediata da biomassa foram determinados. E os teores de proteínas, lipídios e poder calorífico inferior foram estimados para o último dia dos cultivos. Observou-se que a adição de glicose após 72h do início do cultivo, em dose única ou fracionada, melhorou o aproveitamento desta fonte de carbono pelas microalgas, minimizando o consumo pelas bactérias uma vez que os cultivos foram xênicos. Nos cultivos mixotróficos, o teor de carboidratos foi igual ao do grupo controle (cultivos autotróficos), aproximadamente 37%, ao passo que houve aumento do teor lipídico (1,41 vezes para adição única e 1,67 vezes para a adição fracionada), indicando o potencial de aplicação de Chlorella minutissima tanto para a produção de etanol como de biodiesel. Considerando o etanol de primeira geração cuja produtividade de etanol de biomassa algácea poderia alcançar uma produtividade de dez vezes maior que a da cana-de-açúcar, e para o de segunda geração poderia chegar a quarenta vezes superior ao do bagaço de cana com base em projeções de produção anual biomassa algácea seca em torno de 90 t/ha, e considerando o mesmo teor fermentescível para as biomassa. A biomassa algácea também apresentou elevado teor de carbono (~40%) e de compostos voláteis (acima de 76% nos cultivos mixotróficos). O poder calorífico superior em condições mixotróficas chegou a 22,27 MJ/kg (maior que o da madeira, que é de cerca de 18 MJ/kg), além de um menor teor de cinzas (2,78 vezes). Estas características são positivas para aplicação da biomassa em processos de conversão termoquímica, como combustão direta e gaseificação. Além disso, os cultivos mixotróficos apresentaram uma diminuição de 0,76 vezes do teor de proteínas, o que favorece uma menor emissão de NOx nos processos termoquímicos. Os teores de clorofila e carotenoides do cultivo mixotrófico com adição única apresentaram um aumento em relação ao controle de, respectivamente, 1,79 e 1,69 mostrando um potencial para a produção de suplementos destinados à alimentação humana, viabilizando, em termos de custos, a produção de biocombustíveis a partir do uso dos carboidratos e lipídios da biomassa residual após a extração destes compostos de maior valor agregado. / This study evaluated the energetic potential of Chlorella minutissima cultivated in autotrophic (Guillard f/2 media) and mixotrophic conditions using the same medium plus glucose additions in different strategies: I) Two additions of 0.2 g/L glucose in a 48h interval up to 0.4 g/L glucose supply; II) Single addition of 0.2 g/L glucose at the beginning of the cultivation; III) Single addition of 0.2 g/L glucose after 72h from the cultivation beginning; IV) addition of 0.05 g/L glucose, 72h after the cultivation start, followed by three additions in 48h intervals up to the total supply of 0.2 g/L. Growth curves were determined by daily cell density monitoring in each cultivation flask. Productivity and carbohydrate, chlorophyll-a, carotenoids, yields and higher and ultimate and proximate analyses were done in the biomass. Were estimated lipids, protein and low heating value obtained at the end of cultivation. Glucose addition after 72h cultivation, whether in single or fractionated doses, improved the utilization of this carbon source by the microalgae, minimizing the bacterial competition once the cultures were xenic. In these treatments, the carbohydrate yield was the same as the control group (autotrophic), around 37%, whereas the lipid yields were higher (1.41 times to single addition and 1.67 times for fractionated addition) representing 31% of the bulk biomass, indicating the potential use of this Chlorella minutissima both for ethanol and biodiesel production. Considering the first generation ethanol whose productivity microalgae ethanol could achieve productivity ten times that of sugarcane, and the second generation is approximately forty times sugarcane bagasse based on projections of annual production of dry algal biomass around 90 t/ha and considering same fermentable yield of the biomass. The algal biomass presented high carbon content (~ 40%), high volatile content (above the 76% in the mixotrophic treatments), and the higher heating value reached 22.27 MJ/kg in mixotrophic conditons, value bigger than the observed for the wood (18.25 MJ/ kg), with low ash content (2.78 times). Such characteristics are positive and indicate a good potential of this biomass be applied in thermochemical processes, such as combustion and gasification. Also the decrease of 0.76 times of protein content in the mixotrophic cultures allows lower NOx emission in thermochemical processes. Chlorophyll and carotenoids yields in the cultures with single glucose addition were respectively 1.78 e 1.69 higher than the in autrotrophic ones, also indicating the potential use of these coproducts for food supply for human consumption allowing, in terms of costs, the production of biofuels from the use of carbohydrates and lipids from the residual biomass after the removal of these high value-added compounds.

Ce travail décrit la synthèse d'une série de matériaux à base de biomasse d'alginate et d'algues; ces matériaux ont été conçus sous différentes formes: billes et mousses. Des procédés spécifiques ont été mis au point pour l’utilisation directe de la biomasse algale (AB, sans ajout d’autres polymères) avec le souci de développer un processus de synthèse simple et respectueux de l’environnement (production réduite de sous-produits et sans additif supplémentaire). Ces matériaux ont été testés pour la décontamination d’effluents contenant des métaux lourds (Pb(II) et Cu(II)), mais également pour la valorisation des métaux (métaux du groupe platine, PGM: Pd(II) et Pt(IV)). Différents paramètres opératoires ont été testés afin d'évaluer les capacités de sorption et les étapes limitantes, mais également d'identifier des stratégies d’amélioration des performances d’adsorption. L’incorporation de poly(éthylèneimine) (PEI) est une méthode prometteuse pour augmenter la densité de groupes réactifs (fonctions amines). Différents procédés ont été testés: (a) l'incorporation de particules de PEI réticulées avec du glutaraldéhyde (billes hétérogènes: ABA/PEI), et (b) le greffage homogène de PEI sur de l'alginate (suivi de la réticulation par le glutaraldéhyde) (billes homogènes HABA/PEI). La spectroscopie FTIR et l'analyse MEB& MEB-EDX ont été utilisées pour interpréter les mécanismes de fixation ainsi que pour caractériser la structure des matériaux. Dans une deuxième étape, les matériaux sélectionnés ont été testés pour la catalyse supportée en utilisant la réaction d'hydrogénation du 3–nitrophénol (3-NP). Les résultats sont structurés en 3 parties développées successivement: (a) synthèse des billes d’alginate, AB et AB/PEI et étude de l’adsorption de métaux lourds et de PGMs, (b) comparaison des propriétés d’adsorption du Pd(II) par les billes composites AB/PEI préparées par les voies homogène et hétérogène (et leur application aux tests en catalyse supportée), et (c) la synthèse de mousses poreuses (préparées par réaction entre l’alginate et la PEI) appliquées à l’adsorption du Pd(II) et à la catalyse supportée en réacteur à lit fixe.Si la PEI a un effet limité sur la fixation des métaux lourds (interaction avec les groupes carboxyliques de la biomasse d'alginate ou d'algues), sa présence améliore l’adsorption des métaux dans le cas des PGMs (les groupes amine protonés ont une forte affinité pour les espèces chloro-anioniques du Pd(II)) en particulier pour les billes d'alginate et AB. Tous les adsorbants ont une préférence pour le Pb(II) par rapport au Cu(II) et pour le Pd(II) par rapport au Pt(IV); la présence de PEI limite la sélectivité du matériau pour le Pb(II) et le Pd(II). La capacité de fixation et la stabilité des billes composites d'alginate/PEI ont été améliorées en utilisant le mode de synthèse homogène (la PEI étant dispersée de manière homogène dans la bille avant la réticulation par le glutaraldéhyde). Les deux supports (billes hétérogènes ou homogènes) chargés en Pd(II) (ensuite réduit) ont permis des performances catalytiques comparables bien qu’inférieures à celles des catalyseurs classiques, mais le mode homogène améliore la stabilité à long terme du matériau. Le conditionnement du support catalytique sous forme de mousse a permis de tester la réaction catalytique dans un système à lit fixe : le conditionnement sous forme de mousse améliore les propriétés de transfert de masse par rapport aux billes et la constante de vitesse apparente n'est que légèrement réduite après 30 cycles de fonctionnement. / This work describes the synthesis of a series of materials based on alginate and algal biomass (AB); these materials have been designed under different shapes: beads and foams. Special processes have been developed for directly using the algal biomass (without adding other polymers) with the double objective of simple processing and environmentally-friendly manufacturing (reduced production of sub-products and without additional resources). These materials have been tested first for metal recovery for heavy metal decontamination (Pb(II) and Cu(II)) but also for the valorization of metals (platinum groups metals, PGMs: Pd(II) and Pt(IV)). These studies were performed investigating various operating conditions in order to evaluate sorption capacities and limiting steps but also to identify the processes to be used for improving sorption performance. The incorporation of poly(ethyleneimine), PEI, is a promising method for increasing the density of highly reactive groups (amine functions). Different processes have been tested: (a) the incorporation of particles of PEI crosslinked with glutaraldehyde (heterogeneous beads: ABA/PEI), and (b) the homogeneous grafting of PEI on alginate (followed by glutaraldehyde crosslinking) (HABA/PEI beads). Several techniques have been used for characterizing the sorption process and the structure of developed sorbents, including FTIR spectroscopy, SEM & SEM-EDX analysis. In a second step selected materials have been tested for supported catalysis using the simple reaction of hydrogenation of 3–nitrophenol (3-NP) as a test reaction. The results are structured in 3 parts successively developed: (a) synthesis of alginate, AB and AB/PEI beads and testing for sorption heavy metals and PGMs, (b) comparison of Pd(II) sorption properties of AB/PEI composite beads prepared by the homogeneous and the heterogeneous routes (and their application to supported catalytic tests), and (c) synthesis of highly porous foams (prepared by reaction of alginate with PEI) and the testing of Pd(II) sorption and Pd-supported catalysis (in fixed-bed reactor). While PEI hardly affects the sorption of heavy metals (due to direct interaction with carboxylic groups of alginate or algal biomass), the presence of PEI strongly improves metal binding in the case of PGMs (the protonated amine groups strongly bind chloro-anionic PGM species). All the sorbents have a preference for Pb(II) over Cu(II) and for Pd(II) over Pt(IV), especially for alginate and AB beads because the presence of PEI limits the selectivity of the material for Pb(II) and Pd(II). Both the sorption capacity and the stability of composite alginate/PEI beads were improved while using the homogeneous synthesis mode (the PEI polymer being homogeneously dispersed in the bead before glutaraldehyde crosslinking). The two supports (heterogeneous vs. homogeneous beads) loaded with Pd(II) and subsequently reduced gave comparable catalytic performance (lower than conventional catalysts) but the homogeneous mode improves the long-term stability. The conditioning of the catalytic support as a foam allows testing the catalytic reaction in fixed-bed system: the conditioning improves mass transfer properties compared to beads and the apparent rate constant is only slightly reduced after operating 30 cycles.

För att hålla vattendragen och miljön rena, renas avloppsvattnet för att nå ett visst mått innan det släpps ut. Vi gjorde en fallstudie för att utvärdera metoderna som används för att behandla avloppsvatten i tre steg: primär, sekundär och tertiär i delstaten Texas, USA. Vi fann att olika fysikaliska, kemiska och biologiska bearbetningsmetoder används i stor utsträckning i dessa tre stadier. Även om en del av det slam som produceras i en avloppsvattenreningsanläggning utsätts för anaerob rötning (AD) process för att producera biogas, skickas majoriteten av dem till deponier som är ohållbart eftersom det skapar miljöföroreningar som läckage av näringsämnen, påverkar markens biologiska mångfald och släpper ut giftiga gaser och växthusgaser (GHG) som CH4, CO2, N2O. Den mest hållbara och prisvärda metoden för att behandla avloppsvatten är att använda mikroalger och några av fördelarna inkluderar: (i) använda CO2 som en kolkälla och generera syre, (ii) synergistiskt arbeta med aeroba bakterier som bryter ner organiska föroreningar i vatten på kort tid tid, (iii) högeffektiv bindning av överskott av kväve, fosfor och tungmetaller i avloppsvatten. Flera algbaserade reningsmetoder för avloppsvatten har utvecklats. Bland dem är reaktorn Rotating Algal Biofilm (RAB) en av de ledande behandlingsmetoderna som använder ett roterande band som består av syntetiska material som rör sig på en cylinder som är delvis nedsänkt i avloppsvatten. Algbiomassan kunde skördas från bältet genom att helt enkelt skrapa materialets yta. Vi uppskattade att ~1793,7 miljoner liter avloppsvatten behandlas dagligen i delstaten Texas och hypotetiskt om allt avloppsvatten behandlas med RAB skulle ~174,2 ton algbiomassa kunna produceras. Denna algbiomassa kan användas för AD-processen eller vidarebearbetas och fraktioneras till lipider, kolhydrater och proteiner med hjälp av etablerade hydrotermiska bearbetningsmetoder och användas som byggstenar för att producera bränslen, kemikalier och biomaterial. Tre scenarier har undersökts som belyser potentialen och fördelarna med att använda alger för att behandla avloppsvatten jämfört med konventionella metoder för avloppsvattenrening och hur denna övergång kommer att gynna ekonomin och miljön. / To keep the waterways and environment clean, wastewater is treated to reach a certain metric before they are discharged.  We did a case study to evaluate the methods used to treat wastewater in three stages: primary, secondary, and tertiary in the state of Texas, United States. We found different physical, chemical, and biological processing methods are widely used in these three stages. Though some of the sludge produced in a wastewater treatment facility are subjected to anaerobic digestion (AD) process to produce biogas, the majority of them are sent to landfills which is unsustainable as it creates environmental pollution such as nutrient leaching, impacts soil biodiversity, and releases toxic gases and greenhouse gases (GHGs) such as CH4, CO2, N2O. The most sustainable and affordable method of treating wastewater is using microalgae and some of the advantages include: (i) use CO2 as a carbon source and generate oxygen, (ii) synergistically working with aerobic bacteria breaking down organic contaminants in water in a short period of time, (iii) highly efficient sequester of excess nitrogen, phosphorus, and heavy metals in wastewater. Several algal based wastewater treatment methods have been developed. Among them, the Rotating Algal Biofilm (RAB) reactor is one of the leading treatment methods that uses a rotating belt made up of synthetic materials moving on a cylinder partially submerged in wastewater. The algal biomass could be harvested from the belt by simply scrapping the material's surface. We estimated that ~1793.7 million gallons of wastewater are treated daily in the state of Texas and hypothetically if all the wastewater is treated using RAB ~174.2 tons of algal biomass could be produced. This algal biomass can be used for the AD process or further processed and fractionated to lipids, carbohydrates, and proteins using established hydrothermal processing methods and used as building blocks for producing fuels, chemicals, and biomaterials. Three scenarios have been investigated, highlighting the potential and benefits of using algae to treat wastewater compared to conventional wastewater treatment methods and how this transition will benefit the economy and environment.