Dissertations / Theses on the topic 'Algal Biomass'

Applied research is increasingly defined within a context of sustainability and ecological modernisation. Within this remit, recent developments in algal biotechnology are considered to hold particular promise in integrating aspects of bioremediation and bioproduction. However, there are still a number of engineering and biological bottlenecks related to large scale production of algae; including requirements to reduce both capital expenditure (CAPEX) and operational expenditure (OPEX). One potential avenue to reduce these costs is via feedstock substitution and resource sharing; often described as industrial symbiosis. Such an approach has the benefit of providing both environmental and economic benefits as part of an 'eco-biorefinery'. This thesis set out to investigate and address how best to approach some of the cost related bottlenecks within the algal industry, through a process of industrial integration and novel system design. The doctorate focussed on applications within a Northern European context and was split into four research topics. The first and second parts identified a suitable algal strain and were followed by the characterisation of its growth on wastewater; with the findings showing Chlorella sorokiniana (UTEX1230) capable of robust growth and rapid inorganic nutrient removal. The third part detailed the design, construction and validation of a lower cost and fully scalable modular airlift (ALR) photobioreactor, suitable amongst other applications for use within wastewater treatment. This work concluded with a pilot scale deployment of a 50 L ALR system. The fourth research section detailed the costs of ALR construction and operation at a wastewater treatment works, with a particular focus on the benefits that can be derived by industrial symbiosis. The thesis concludes with an appraisal of the ALR design and considers the potential for the technology, particularly within a wastewater treatment role. A final consideration is given to the practicalities of developing the algal industry within the UK in the short to medium term.

Environmental awareness has increased significantly during the past years and the need to replace fossil fuels with a more sustainable alternative has become a priority in the modern society. Algal biofuels have shown to have a good productivity compared to other biomass feedstock options but the high cost- low-efficiency cultivation process has proven to be a challenge. The purpose of this project is to use membrane technologies to recover algal biomass more efficiently. This technology would significantly reduce the water usage and energy input to the algal biomass production process. In this study, the Derjaguin-Landau-Verwey-Overbeek (DLVO) model derived using the Surface Element Integration (SEI) technique was used to identify the interaction energy between 3 microalgae species and 5 hollow fiber membrane materials. The results suggested that Scendesmus Obliquous would have the lowest energy barrier (-2.7834 kT) with a Poly(vinylbutyral) (PVB) hollow fiber membrane, therefore it would have a greater initial number of algal cells attaching to the membrane, compared to the other microalgae and membrane materials studied. Further work needs to be completed in order to integrate algae growth and biomass harvesting into the actual model.

Research using microalgae Chlorella vulgaris was conducted in order to determine the maximum CO2 concentration under which algae can grow, within the emission range from oil and natural gas burning plants (0-20%). After choosing the optimal CO2 percentage, pH and alkalinity were determined; and finally, an electrochemical (EC) batch reactor connected to DC current was applied to achieve algae cell annihilation, and therefore, facilitate anaerobic digestion, methane production and energy recovery. It was determined that algae can grow under 20% CO2, being 15% CO2 the most effective (pH of 6.64 and alkalinity of 617.5 mg/L CaCO3). Electroporation using an electrochemical batch reactor is effective in breaking cells membranes, which simplifies anaerobic digestion process and methane production. The parameters found effective for completely breaking the algae cell are: detention time of 1 more or less 0.5 minutes, and minimum voltage and current of 65 Volts/285 ml and 3.9 Amps/285 ml, respectively

Nowadays microalgae are studied, and a number of species already mass-cultivated, for their application in many fields: food and feed, chemicals, pharmaceutical, phytoremediation and renewable energy. Phytoremediation, in particular, can become a valid integrated process in many algae biomass production systems. This thesis is focused on the physiological and biochemical effects of different environmental factors, mainly macronutrients, lights and temperature on microalgae. Microalgal species have been selected on the basis of their potential in biotechnologies, and nitrogen occurs in all chapters due to its importance in physiological and applicative fields. There are 5 chapters, ready or in preparation to be submitted, with different specific matters: (i) to measure the kinetic parameters and the nutrient removal efficiencies for a selected and local strain of microalgae; (ii) to study the biochemical pathways of the microalga D. communis in presence of nitrate and ammonium; (iii) to improve the growth and the removal efficiency of a specific green microalga in mixotrophic conditions; (iv) to optimize the productivity of some microalgae with low growth-rate conditions through phytohormones and other biostimulants; and (v) to apply the phyto-removal of ammonium in an effluent from anaerobic digestion. From the results it is possible to understand how a physiological point of view is necessary to provide and optimize already existing biotechnologies and applications with microalgae.

Nowadays microalgae are studied, and a number of species already mass-cultivated, for their application in many fields: food and feed, chemicals, pharmaceutical, phytoremediation and renewable energy. Phytoremediation, in particular, can become a valid integrated process in many algae biomass production systems. This thesis is focused on the physiological and biochemical effects of different environmental factors, mainly macronutrients, lights and temperature on microalgae. Microalgal species have been selected on the basis of their potential in biotechnologies, and nitrogen occurs in all chapters due to its importance in physiological and applicative fields. There are 5 chapters, ready or in preparation to be submitted, with different specific matters: (i) to measure the kinetic parameters and the nutrient removal efficiencies for a selected and local strain of microalgae; (ii) to study the biochemical pathways of the microalga D. communis in presence of nitrate and ammonium; (iii) to improve the growth and the removal efficiency of a specific green microalga in mixotrophic conditions; (iv) to optimize the productivity of some microalgae with low growth-rate conditions through phytohormones and other biostimulants; and (v) to apply the phyto-removal of ammonium in an effluent from anaerobic digestion. From the results it is possible to understand how a physiological point of view is necessary to provide and optimize already existing biotechnologies and applications with microalgae.

This thesis evaluates the performance of marine algal-based biosorbents in treating trace metal bearing aqueous solutions. Native seaweed varieties (Ascophyllum nodosum, Lessonia flavicans, Durvillea potatorum and Laminaria hyperborea) were selected on the basis of their varying algin composition as well as their characteristic mannuronic/guluronic acid content. Dealginated seaweed residues, i.e. waste materials arising during algin extraction from brown marine algae were also evaluated as potential metal biosorbent materials. The biosorbents showed significant metal sorption capacity for copper, cadmium, nickel and zinc from synthetic single metal and multi-metal bearing aqueous solutions. The equilibrium biosorption process may be described using a surface complex formation model. Copper biosorption involved chelation-type surface reactions as well as ion exchange whereas nickel and zinc biosorption may be described by simple ion exchange and electrostatic interactions between metal ions and the negatively charged algal surface. Evidence of stoichiometric release of protons upon metal biosorption has been found. Metal biosorption was found to be dependent upon transport limitations due to intraparticle diffusion. Surface functional groups within algal biosorbents that are responsible for metal-ion binding were identified in an attempt to understand the mechanisms of metal biosorption. Physical and chemical characterization techniques such as potentiometric titrations and esterification were used for surface acidity measurements, nitrogen sorption porosimetry for surface area and pore size distribution analysis and FT-IR spectroscopy to identify carboxyl groups attached to structural polysaccharides in algae. Performance of native and dealginate algal fixed-bed mini-columns provided optimum operating conditions for dynamic exchange between metal ions in solution and the algal biomass. Selected biosorbents were successfully employed to treat real industrial metal-plating rinse waters. The most efficient eluants for regeneration of metal-laden biosorbent columns were also identified.

Algae can be used as a feedstock for agricultural fertilizers, livestock/poultry feeds, anaerobic digestion, and biofuel production. Regardless of the end product, water removal is necessary and difficult to do cost effectively. For each product the requirements for moisture content (or solids content) vary, such that a desirable water removal strategy would need to be adaptable to varying levels of water removal. Flocculation, with sedimentation and drying was evaluated as a possible strategy for algae dewatering. Anionic and nonionic flocculants are known to be ineffective at flocculating algal culture, which was confirmed for this case by electro-osmotic flow testing of the algae and jar tests with three flocculant charge types. Electrophoretic mobility of the algae indicated that it has a negative charge and no flocs were present in the jars. The effectiveness of the cationic flocculant was determined by measuring settling rates, supernatant turbidity, and filtration rates. Sedimentation and filtration rates of Scenedesmus acutus were measured with varying dosages (0-25 ppm) of a synthetic cationic polymeric flocculant. The results of this study should assist in predicting the time it takes to thicken algae at a concentration range of 0.4-1.0 g/L to a product at a concentration range of 15-250 g/L.

The overall aim of the research was to investigate the hydraulic mixing characteristics and energy efficiency of raceway systems for the large-scale cultivation of micro-algae. For this purpose, two pilot-scale raceway reactors (100 m length x 1 m wide channel), each with a paddlewheel for liquid circulation and a sump for gas exchange, were built and tested under different conditions. The optimal depth to run the raceway was 0.20 m. At this depth, a typical velocity for liquid circulation in raceways of 0.20 m s-1 was obtained with a power consumption of 2.10 W m-3, which was reduced to 1.6 W m-3 by using one baffle in the bend. At this velocity, addition of two and three baffles did not influence the power consumption significantly. The study of mixing as indicated by the Bodenstein number showed that mixing took place mainly in the paddlewheel, sump and bends although the overall behaviour of the system was plug flow since most of the liquid was contained in the channels. A study with and without a sump baffle showed that the maximum velocity achieved when it was in place was 37 % lower than without the baffle, while at the same time the power consumption increased by 79 %. In addition, its presence reduced mixing, while the improvement in mass transfer was very low. For all these reasons, a sump baffle with the studied configuration was not recommended unless its hydrodynamic performance can be significantly improved. The selection of a membrane plate diffuser giving a small bubble size and low pressure drop enhanced mass transfer efficiency. Oxygen was desorbed mainly in the sump and paddlewheel due to high turbulence which increased the mass transfer coefficient. Peaks in dissolved oxygen at midday, however, were identified as a major problem causing growth inhibition. Accumulation of oxygen in the culture can be reduced by gas bubbling in the sump, although in cultures with a high concentration of bicarbonates CO2 stripping may occur. CO2 mass transfers above 96 % were achieved in the raceway, highlighting the efficiency of the sump as a device for gas exchange. The use of flue gas was effective to control pH, provide carbon to the culture and reduce dissolved oxygen peaks. A carbon balance showed that outgassing in the raceway was almost negligible and main carbon loss was through the liquid phase in the harvesting process. Use of a hydrostatic pressure wheel for lifting water increased the hydraulic efficiency of the raceway between 15-20 %. The paddlewheel equipped with shoe used around 40-50 % of the energy required by flat configuration. This corresponds to an improvement of 2-5 times existing efficiencies, with higher values occurring at longer simulated channel lengths where the hydrostatic head losses are greater. This efficiency, however, is still well below theoretical values, and there is scope for further optimization the improved paddlewheel design for specific raceways.

AD technology is well developed, cost efficient and can be easily implemented in developing countries. Biogas production has become a very topical subject, with many European nations introducing initiatives to increase biogas production. AD of algal biomass was studied in detail during the 1980’s, however, with the current drive toward cleaner technology processes, there has been a renewed interest in the technology. This study investigated the feasibility of using algal biomass as a feedstock for AD.

Mass outdoor microalgal cultures for the production of low priced bio-based commodities (food, feed, fuels) and high-value bioproducts (polyunsaturated fatty acids, pigments, therapeutic agents) require stable and commercially-viable biomass production technologies. The classical open raceway pond, the traditional commercial-scale technology for mass biomass production has significant limitations; low productivity rates due to a long culture depth, high risk of contamination, and lack control of environmental conditions. To produce high biomass density microalgal cultures, closed photobioreactors are preferred due to a better operational control of culture conditions, environmental variables and contamination. However, the operation of solar closed photobioreactors under outdoor scenarios requires sufficient cooling (in summer) and heating (in winter) technologies for guaranteed production of biomass (products) throughout the year. Heating and cooling operations are not only expensive and energy-intensive but require both grid electricity and precious freshwater (already limited) for their effectiveness, thus imposing a sustainability challenge. Therefore, next-generation algal photobioreactor designs must address these challenges of cost, energy and land-use efficiencies, while offering optimum biomass production. To this end, we have developed for the first time a hybrid thermally-insulated photobioreactor that is based on illumination spectral filtering for passive temperature control and integration with photovoltaic panels for electrical energy generation geared towards grid-independent operation. The novel photobioreactor has the illumination surfaces constructed of spectrally-selective low-emissivity film, which reflects >90% of non-photosynthetic photons (ultraviolet and infrared wavelengths) and transmits >70% of photosynthetically-beneficial visible photons (wavelengths spanning 400 to 700 nm) and its double glass units allow for high thermal insulation. A semi-transparent cadmium telluride photovoltaic cell that transmits 40% of the captured sunlight was glued to the top of the photobioreactor. To assess the viability and effectiveness of the novel photobioreactor design in thermoregulating microalgal cultures, the growth and photophysiological responses of two microalgae species Nannochloropsis sp. MUR 267 and Arthrospira platensis MUR 126 were investigated under laboratory conditions. Experimental results show that the maximum culture temperature in the novel photobioreactors was similar to the conventional water jacket system and 23-33% lower than that in the controls without temperature control system. The biomass productivity of Nannochloropsis culture in the insulated photobioreactors (112.47±3.36 mg L-1 d-1) was only 10% lower than that attained in the water jacket reactor, and no net growth was seen in the control without thermoregulation due to a high temperature. Chlorophyll a fluorescence measurements show that both microalgae cultures in the cultivation systems were not thermally stressed. This proof-of-principle study clearly demonstrated that infrared blocking films can significantly reduce heat gain in flat plate photobioreactors without a dramatic reduction in culture performance. At this point, a pilot-scale spectrally-selective insulated-glazed photovoltaic (IGP) flat panel photobioreactor (1.2 m length x 1.5 m height, 10 cm optical depth, 140 L working culture volume) capable of co-producing microalgal biomass and electricity, while eliminating the need of cooling water was developed. The viability of this novel system for culturing Nannochloropsis sp. was compared to similar flat panel photobioreactors based on freshwater passive evaporative cooling (PEC), infrared reflecting thin-film coating (IRF), and an open raceway pond (ORP). Maximum culture temperature (33.8 ± 2.9 ˚C) was highest in the IRF reactor while no significant difference was seen between IGP and PEC photobioreactors. Specific growth rate and biomass productivity of Nannochloropsis sp. was similar in all closed photobioreactors; however, ORP showed significantly lower productivity. Algal cultures in these cultivation systems were not thermally stressed. Interestingly, electricity generated from IGP photobioreactor during this period was 2.5-fold higher than the mixing energy requirement. Investigating the impact of the temperature control strategies on macromolecular content and fatty acid profile of Nannochloropsis sp., the normalized biochemical composition of the biomass showed a general trend of lipid > protein > carbohydrate, with no large variation of each across treatments. Besides C16:0, which was 24% higher in the photobioreactors than ORP, no other significant shift in major saturated and monounsaturated fatty acid components of this alga were seen among cultivation systems. The highest eicosapentaenoic acid (EPA, C20:5n-3), 16% and ϒ-linolenic acid (C18:3n-6), 8% of total fatty acid were found in ORP with the lowest average culture temperature and diel temperature variation than photobioreactors. Among all photobioreactors, IGP has the least diel temperature changes with an EPA content that was 21% higher than PEC, indicating that constructing photobioreactors with spectrally-selective materials is a viable strategy for managing the internal temperature, with no significant negative impact on biochemical and fatty acid profiles of microalgae. When a cold-intolerant microalga, Arthrospira platensis was cultured in the thermally-insulated IGP (no heat supplementation) during austral winter and compared with PEC under a cycle of heating (13-hour night) and thermostat-regulated cooling, and a continuously heated ORP, the average temperature in the IGP (21.0±0.03˚C) was similar to the heated PEC. Experimental results indicated that biomass productivity of Arthrospira in IGP photobioreactor was 67% higher than ORP and significantly lower than PEC. Phycocyanin productivity (16.3±1.43 mg g-1 d-1) showed no variation between photobioreactors but significantly less in the ORP. During this winter operation, electrical energy output of IGP photobioreactor exceeded mixing energy need by 75%. Finally, from the energy efficiency perspective, the net energy ratio of a 1-ha IGP facility used to cultivate Nannochloropsis sp. without freshwater-based cooling reached 3.0, a value comparable to agricultural bio-oil crops such as Jatropha and soybean. The annual biomass productivity was 66.0-tons dry weight ha-1, equivalent to overall energy output of 1,696 GJ ha-1. The integrated semi-transparent photovoltaic panels generated an additional 1,127 GJ ha-1 yr-1 (313 MWh ha-1 yr-1). Energy demands from plant building materials, machinery, fertilizers, plant operations, and biomass harvesting constituted total energy input with a combined value of 707 GJ ha-1 yr-1. A comparison with a PEC photobioreactor requiring freshwater-based cooling showed that IGP had a 73% greater net energy ratio using the same plant size and system boundary. In conclusion, the above results suggest that developed IGP photobioreactor offers a reliable, energy-efficient platform for large-scale production of biomass and high-value chemicals from microalgae, with no requirements for extraneous cooling and heating systems, generating sustainable baseload electrical energy to energize production operations.

Research was conducted using algal biomass obtained from the surface of a secondary clarifier at Bridge City Wastewater Treatment Plant and subsequently sent through an electrochemical (EC) batch reactor at various concentrations. The first objective was to achieve maximum cell wall destruction electrochemically using the EC batch reactor and determine the optimal detention time and voltage/current relationship at which this occurred. The second objective was to subject two algal mediums to anaerobic digestion: the algal medium without electrochemical disinfection and the algal medium after disinfection. Every three days, for 12 days, total solids were measured from each apparatus to determine if cell destruction increased, decreased or did not change the consumption rate of algae by anaerobic bacteria. The consumption rate of algae is directly proportional to the production of methane, which can be used as a source of biofuel.

This thesis investigates the effects of co-culturing microorganisms including 37 yeast, 38 bacteria, nine diazotrophic cyanobacteria, and three fungi on biomass and lipid production in fresh- and saltwater algae. Algal lipid content was measured using Nile Red method and gravimetric techniques. Among the algal strains tested, freshwater Coelastrum sp. 46-4, and saltwater Cricosphaera sp. 146-2-9, showed enhanced biomass yield and lipid content in response to co-culture with bacteria, cyanobacteria, and fungi. While co-culture with yeast caused inhibition of algal productivity, no difference in algal productivity was observed between nitrogen-free diazotrophic cyanobacterial co-culture and nitrogen-replete monoalgal culture. Results indicated that extracellular compounds from the freshwater bacteria Pseudomonas stutzeri and marine fungus Fusarium sp. significantly account for stimulation of lipid accumulation within algal cells, while co-cultivation with live microorganism cells stimulated biomass production in algae.

In the search for large-scale production of renewable fuels and chemicals, hydrothermal liquefaction (HTL) of biomass has emerged as one of the most promising routes. Whilst this conversion route is suitable for various feedstocks, there has been enormous attention directed towards the utilisation of algae. The aim of this thesis is to gain a better understanding of the process scaling effects and to enhance the quality of the bio-crude oil product. A novel feature of this work is that it has successfully tested the HTL process in a continuous-flow (15–70 L/h) pilot-scale plant – by doing so, it has been able to shed light on the process engineering and scaling aspects. A maximum bio-crude yield of ~42 wt.% was achieved from a commercially-available microalga (Chlorella) while being processed with a 10 wt.% solids loading at 350 °C, 200 bar and 3 min residence time. The results indicate that maximal product yields may be obtained in much shorter times under continuous flow hydrothermal processing than batch studies have previously suggested. Collaboration with algal cultivation specialists also allowed links between biomass production and subsequent conversion to be explored. Promising results for a robust microalgae polyculture grown under waste streams from a coal-fired power station are presented and discussed. The opportunity of tailoring the algal growth process, through nutrient starvation, to improve the bio-crude properties was also investigated. Oils obtained from starved Oedogonium macroalgae were shown to contain considerably lower N levels (<2%), compared to those from normal Oedogonium as well as microalgae (>4%). A two-step batch HTL process, also aimed at producing low-N oil, is additionally put forward. In summary, a number of key contributions are contained in this thesis which included providing insights into scaling the HTL process, as well as employing novel approaches to enhance the quality of the derived products.

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Universidade Federal de Sao Carlos
Algae are organisms with which studies have been made on the uptake of carbon dioxide, as a source of lipids for research on biofuels such as fertilizers and soil. But little is known about the interaction of such organisms with higher plants. Thus, the general objective of this master thesis was to reuse the algal biomass of Selenastrum capricornutum Printz (Chlorophyceae class) e Chlorella sorokiniana Shihira e Krauss (Trebouxiophyceae class) in pelleting seed Bowdichia virgilioides, native to the Brazilian Savanna that are classified as threatened with extinction and whose wood has attributes for the furniture industry, besides the medicinal properties already reported in other studies. First, the seeds were grown in a greenhouse, with the following treatments: a) seeds naked; b) pelleted seeds with white glue based on polyvinyl acetate diluted to 8% at water and gypsum; c) seeds pelleted with glue based white polyvinyl acetate diluted to 8% at wet algal biomass of Selenastrum capricornutum and gypsum; d) pelleted seeds with white glue based polyvinyl acetate diluted to 8% at wet algal biomass of Chlorella sorokiniana and gypsum. Fungicide and insecticide were added to the silicato and gypsum for agricultural according to industry directions. The parameters mean emergence time (days), weight (g) dry and cool, length (cm) of aerial and root portions and number of nitrogen fixing nodules in the roots don t showed statistically significant difference between treatments. The variable "emergency percentage" showed that pelleted seeds with C. sorokiniana biomass as a cement material constituent showed value equivalent to conventional treatment (naked), paving the way for new studies pelleting with agal biomass of that species. As higher be the algae intracellular biochemical values, higher be the chances to achieve satisfactory results, because the seed can be use algae biochemical components at its development. In a second stage, there was pelleted seed sown in an area of brazilian savanna and the treatments were: a) naked seed; b) pelleted seeds with white glue based on polyvinyl acetate diluted to 8% at water and gypsum; c) pelleted seeds with white glue based on polyvinyl acetate diluted to 8% at wet algal biomass of Selenastrum capricornutum and gypsum with fungicide and insecticide; d) pelleted seeds with white glue based on polyvinyl acetate diluted to 8% at water and silicate for agricultural; and e) pelleted seeds with white glue based on polyvinyl acetate diluted to 8% at wet algal biomass of Selenastrum capricornutum and silicate for agricultural. Fungicide and insecticide were added to the silicato and gypsum for agricultural according to industry directions. For this experiment hood, it was observed that treatment with only gypsum had a significantly lower percentage of emergence. The treatment with silicate was considered as an effective material coating to the sucupira seed pelleting process, cultivating in savanna field. Thus, the alga Chlorella sorokiniana showed to be an efficient cementing material for pelleting process and silicate for agricultural a promising coating material, when it comes to planting in the field.
Microalgas tem sido alvo em estudos que visam à captação de dióxido de carbono. Esses microrganismos também vêm sendo utilizados como fonte de lipídios para produção de biocombustíveis e estudos relatam sua biomassa como potenciais fertilizantes de solo. Mas, pouco se sabe sobre a interação de tais organismos com vegetais superiores. O objetivo geral desse trabalho foi reutilizar a biomassa de Selenastrum capricornutum Printz (classe Chlorophyceae) e Chlorella sorokiniana Shihira e Krauss (classe Trebouxiophyceae) na peletização de sementes de Bowdichia virgilioides (sucupira preta, sucupira do cerrado), espécie nativa do cerrado brasileiro que está classificada como ameaçada de extinção e cuja madeira possui atributos para a indústria moveleira, além das propriedades medicinais já relatadas em vários trabalhos. Primeiramente, as sementes foram semeadas em casa de vegetação, com os seguintes tratamentos: a) sementes nuas (sem pélete); b) sementes peletizadas com cola branca à base de acetato de polivinila diluída a 8% em água e gesso agrícola; c) sementes peletizadas com cola branca à base de acetato de polivinila diluída a 8% em biomassa algal úmida de S. capricornutum e gesso agrícola; d) sementes peletizadas com cola branca à base de acetato de polivinila diluída a 8% com biomassa algal úmida de C. sorokiniana e gesso agrícola. Ao gesso agrícola foram acrescentados fungicida e inseticida. Tempo médio de emergência (dias), peso (g) seco e fresco, comprimento (cm) das partes aéreas e radiculares e o número de indivíduos contendo nódulos fixadores de nitrogênio nas raízes não apresentaram diferença estatística significativa entre os tratamentos. Contudo, as plântulas de sementes peletizadas com C. sorokiniana, como constituinte do material cimentante, apresentaram porcentagem de emergência equivalente ao tratamento convencional (nua). Observamos que quanto mais elevados forem os valores bioquímicos intracelulares da alga, há mais chances de obtermos resultados satisfatórios, já que a semente pode utilizar tais compostos em seu desenvolvimento. Em um segundo momento, a semeadura de sementes peletizadas foi realizada em uma área do cerrado situada no campus da Universidade Federal de São Carlos (21°57 S, 47°52 W, a 863 m de altitude), cidade de São Carlos-SP. Os tratamentos foram: a) sementes nuas (sem pélete); b) sementes peletizadas com cola branca à base de acetato de polivinila diluída a 8% em água e gesso agrícola; c) sementes peletizadas com cola branca à base de acetato de polivinila diluída a 8% em biomassa úmida de S. capricornutum e gesso agrícola; d) sementes peletizadas com cola branca à base de acetato de polivinila diluída a 8% em água com silicato para uso agrícola; e) sementes peletizadas com cola branca à base de acetato de polivinila diluída a 8% em biomassa úmida de S. capricornutum e silicato para uso agrícola. Ao silicato e gesso para uso agrícola foram acrescentados fungicida e inseticida segundo as recomendações dos fabricantes. Para este experimento em campo, observou-se que o tratamento somente com gesso agrícola proporcionou uma porcentagem de emergência significativamente menor do que o tratamento sementes nuas , sendo o silicato considerado um material mais eficiente como revestimento no processo de peletização de sementes de sucupira do cerrado cultivadas em campo. Assim, a alga C. sorokiniana mostrou-se um material cimentante eficiente no processo de peletização e o silicato para uso agrícola mostrou-se um material de revestimento promissor, em se tratando de plantio em campo.

The effects of groundwater and environmental variables on river ecology in terms of algal biomass (benthic and suspended) were determined across a watershed dominated by agricultural land-use (Raisin River, eastern Ontario). At the watershed scale, during summer base flows, light and temperature or Strahler stream order predicted suspended algal biomass (estimated by chlorophyll a) whereas turbidity and temperature predicted epilithic periphyton biomass in riffle zones; nutrients did not correlate with either algal community. Benthic algal biomass was negatively correlated with suspended algal biomass. At the reach scale, periphyton biomass and total phosphorus were temporally linked but the relationship became uncoupled by spates. Evidence for shallow hyporheic flow but not deep groundwater discharge was reported for one of two reaches studied. Benthic algal biomass accrual increased linearly with both a positive or negative hydraulic gradient, indicating that surface water/groundwater interactions were important.

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

A photobioreactor has been designed and developed to efficiently utilize solar irradiance through spatial dilution of sunlight. The concept of spatial light dilution is simple: incident sunlight is spread over a large surface area, thus reducing the photon flux density of the light. The implementation of this technique, however, is difficult. The reactor described within uses a new approach to spatial light dilution, utilizing recently-developed optical components to diffuse concentrated sunlight inside an algae culture. Preliminary productivity tests indicate a 2-3 fold increase in productivity per unit aperture (sunlight collection area) over a control reactor with direct-sunlight. Aperture productivity of up to 15 gm m-2 day-1 and total solar efficiency of 2% were achieved. A new parameter and yield coefficient are introduced. The parameter total light delivered is defined as the quantity of photons delivered per unit volume per day. The coefficient for yield of biomass on photons is also introduced. For the organism studied in this research, Neochloris oleoabundans, the yield of biomass on photons is approximately 1.09 gm mass per mol photons. The total light delivered to a culture over 24 hours, multiplied by the yield coefficient, provides an estimate of the volumetric productivity of the reactor in sequential-batch operation. In a series of laboratory studies, the total light delivered ranged from 0.097 to 0.945 mol photons L-1 day-1, and the volumetric productivity ranged from 0.11 to 0.945 gm L-1 day-1. A reactor productivity model, integrating reactor geometry and optics with the biomass yield coefficient and volumetric productivity model, predicts that the model organism in the proposed reactor can produce an annual average of 40 gm biomass per square meter of collector area. The model predicts an annual aperture yield of 14.6 kg m-2, at 3% efficiency. This predictive model can be applied to any location that solar data exists, and the techniques can be applied to other types of organisms and reactors to provide productivity estimates.

Microalgae are sun - light cell factories that convert carbon dioxide to biofuels, foods, feeds, and other bioproducts. The concept of microalgae cultivation as an integrated system in wastewater treatment has optimized the potential of the microalgae - based biofuel production. These microorganisms contains lipids, polysaccharides, proteins, pigments and other cell compounds, and their biomass can provide different kinds of biofuels such as biodiesel, biomethane and ethanol. The algal biomass application strongly depends on the cell composition and the production of biofuels appears to be economically convenient only in conjunction with wastewater treatment. The aim of this research thesis was to investigate a biological wastewater system on a laboratory scale growing a newly isolated freshwater microalgae, Desmodesmus communis, in effluents generated by a local wastewater reclamation facility in Cesena (Emilia Romagna, Italy) in batch and semi - continuous cultures. This work showed the potential utilization of this microorganism in an algae - based wastewater treatment; Desmodesmus communis had a great capacity to grow in the wastewater, competing with other microorganisms naturally present and adapting to various environmental conditions such as different irradiance levels and nutrient concentrations. The nutrient removal efficiency was characterized at different hydraulic retention times as well as the algal growth rate and biomass composition in terms of proteins, polysaccharides, total lipids and total fatty acids (TFAs) which are considered the substrate for biodiesel production. The biochemical analyses were coupled with the biomass elemental analysis which specified the amount of carbon and nitrogen in the algal biomass. Furthermore photosynthetic investigations were carried out to better correlate the environmental conditions with the physiology responses of the cells and consequently get more information to optimize the growth rate and the increase of TFAs and C/N ratio, cellular compounds and biomass parameter which are fundamental in the biomass energy recovery.

Microalgae are sun - light cell factories that convert carbon dioxide to biofuels, foods, feeds, and other bioproducts. The concept of microalgae cultivation as an integrated system in wastewater treatment has optimized the potential of the microalgae - based biofuel production. These microorganisms contains lipids, polysaccharides, proteins, pigments and other cell compounds, and their biomass can provide different kinds of biofuels such as biodiesel, biomethane and ethanol. The algal biomass application strongly depends on the cell composition and the production of biofuels appears to be economically convenient only in conjunction with wastewater treatment. The aim of this research thesis was to investigate a biological wastewater system on a laboratory scale growing a newly isolated freshwater microalgae, Desmodesmus communis, in effluents generated by a local wastewater reclamation facility in Cesena (Emilia Romagna, Italy) in batch and semi - continuous cultures. This work showed the potential utilization of this microorganism in an algae - based wastewater treatment; Desmodesmus communis had a great capacity to grow in the wastewater, competing with other microorganisms naturally present and adapting to various environmental conditions such as different irradiance levels and nutrient concentrations. The nutrient removal efficiency was characterized at different hydraulic retention times as well as the algal growth rate and biomass composition in terms of proteins, polysaccharides, total lipids and total fatty acids (TFAs) which are considered the substrate for biodiesel production. The biochemical analyses were coupled with the biomass elemental analysis which specified the amount of carbon and nitrogen in the algal biomass. Furthermore photosynthetic investigations were carried out to better correlate the environmental conditions with the physiology responses of the cells and consequently get more information to optimize the growth rate and the increase of TFAs and C/N ratio, cellular compounds and biomass parameter which are fundamental in the biomass energy recovery.

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.

Renewable energy sources such as biomass are becoming more and more important as alternative to fossil fuels. One of the most exciting new sources of biomass is microalgae. The Hartbeespoort Dam, located 37 km west of South Africa’s capital Pretoria, has one of the dense populations of microalgae in the world, and is one of the largest reservoirs of micro-algal biomass in South Africa. The dam has great potential for micro-algal biomass production and beneficiation due to its high nutrient loading, stable climatic conditions, size and close proximity to major urban and industrial centres. There are five major steps in the production of biodiesel from micro-algal biomass-derived oil: the first two steps involve the cultivation and harvesting of micro-algal biomass; which is followed by the extraction of oils from the micro-algal biomass; then the conversion of these oils via the chemical reaction transesterification into biodiesel; and the last step is the separation and purification of the produced biodiesel. The first two steps are the most inefficient and costly steps in the whole biomass-to-liquids (BTL) value chain. Cultivation costs may contribute between 20–40% of the total cost of micro-algal BTL production (Comprehensive Oilgae Report, 2010), while harvesting costs may contribute between 20–30% of the total cost of BTL production (Verma et al., 2010). Any process that could optimize these two steps would bring a biomass-to-liquids process closer to successful commercialization. The aim of this work was to study the cultivation and harvesting of micro-algal biomass from the Hartbeespoort Dam for the production of biodiesel. In order to do this a literature study was done and screening experiments were performed to determine the technical and economical feasibility of cultivation and harvesting methods in the context of a new integrated biomass-to-liquids biodiesel process, whose feasibility was also studied. The literature study revealed that the cyanobacterium Microcystis aeruginosa is the dominant micro-organism species in the Hartbeespoort Dam. The study also revealed factors that promote the growth of this species for possible incorporation into existing and new cultivation methods. These factors include stable climatic conditions, with high water temperatures around 25oC for optimal Microcystis growth; high nutrient loadings, with high phosphorus (e.g. PO43-) and nitrogen concentrations (e.g. NO3-); stagnant hydrodynamic conditions, with low wind velocities and enclosed bays, which promote the proliferation of Microcystis populations; and substrates like sediment, rocks and debris which provide safe protective environments for Microcystis inoculums. The seven screening studies consisted of three cultivation experiments, three harvesting experiments and one experiment to determine the combustion properties of micro-algal biomass. The three cultivation experiments were conducted in three consecutively scaled-up laboratory systems, which consisted of one, five and 135-litre bioreactors. The highest productivity achieved was over a period of six weeks in the 5-litre Erlenmeyer bioreactors with 0.0862 g/L/d at an average bioreactor day-time temperature of 26.0oC and an aeration rate of 1.5 L/min. The three cultivation experiments revealed that closed-cultivation systems would not be feasible as the highest biomass concentrations achieved under laboratory conditions were too low. Open-cultivation systems are only feasible if the infrastructure already exists, like in the case of the Hartbeespoort Dam. It is recommended that designers of new micro-algal BTL biodiesel processes first try to capitalize on existing cultivation infrastructure, like dams, by connecting their processes to them. This will reduce the capital and operating costs of a BTL process significantly. Three harvesting experiments studied the technical feasibility and determined design parameters for three promising, unconventional harvesting methods. The first experiment studied the separation of Hartbeespoort Dam micro-algal biomass from its aqueous phase, due to its natural buoyancy. Results obtained suggest that an optimum residence time of 3.5 hours in separation vessels would be sufficient to concentrate micro-algal biomass from 1.5 to 3% TSS. The second experiment studied the aerial harvesting yield of drying micro-algal biomass (3% TSS) on a patch of building sand in the sun for 24 hours. An average aerial harvesting yield of 157.6 g/m2/d of dry weight micro-algal biomass from the Hartbeespoort Dam was achieved. The third experiment studied the gravity settling harvesting yield of cultivated Hartbeespoort Dam-sourced microalgae as it settles to the bottom of the bioreactor after air agitation is suspended. Over 90% of the micro-algal biomass settled to the bottom quarter of the bioreactor after one day. Cultivated micro-algal biomass sourced from the Hartbeespoort Dam, can easily be harvested by allowing it to settle with gravity when aeration is stopped. Results showed that gravity settling equipment, with residence times of 24 hours, should be sufficient to accumulate over 90% of cultivated micro-algal biomass in the bottom quarter of a separation vessel. Using this method for primary separation could reduce the total cost of harvesting equipment dramatically, with minimal energy input. All three harvesting methods, which utilize the natural buoyancy of Hartbeespoort Dam microalgae, gravity settling, and a combination of sand filtration and solar drying, to concentrate, dewater and dry the micro-algal biomass, were found to be feasible and were incorporated into new integrated BTL biodiesel process. The harvesting processes were incorporated and designed to deliver the most micro-algal biomass feedstock, with the least amount of equipment and energy use. All the available renewable power sources from the Hartbeespoort Dam system, which included wind, hydro, solar and biomass power, were utilized and optimized to deliver minimum power loss, and increase power output. Wind power is utilized indirectly, as prevailing south-easterly winds concentrate micro-algal biomass feedstock against the dam wall of the Hartbeespoort Dam. The hydraulic head of 583 kPa of the 59.4 meter high dam wall is utilized to filter and transport biomass to the new integrated BTL facility, which is located down-stream of the dam. Solar power is used to dry the microalgae, which in turn is combusted in a furnace to release its 18,715 kW of biochemical power, which is used for heating in the power-intensive extraction unit of the processing facility. Most of the processes in literature that cover the production of biodiesel from micro-algal biomass are not thermodynamically viable, because they consume more power than what they produce. The new process sets a benchmark for other related ones with regards to its net power efficiency. The new process is thermodynamically efficient, exporting 20 times more power than it imports, with a net power output of 5,483 kilowatts. The design of a new integrated BTL process consisted of screening the most suitable methods for harvesting micro-algal biomass from the Hartbeespoort Dam and combining the obtained design parameters from these harvesting experiments with current knowledge on extraction of oils from microalgae and production of biodiesel from these oils into an overall conceptual process. Three promising, unconventional harvesting methods from Brink and Marx (2011), a micro-algal oil extraction process from Barnard (2009), and a process from Miao and Wu (2005) to produce biodiesel through the acid-catalyzed transesterification of micro-algal oil, were combined into an integrated BTL process. The new integrated biomass-to-liquids (BTL) process was developed to produce 2.6 million litres of biodiesel per year from harvested micro-algal biomass from the Hartbeespoort Dam. This is enough to supply 51,817 medium-sized automobiles per year or 142 automobiles per day of environmentally friendly fuel. The new BTL facility consists of three sections: a cultivation section where microalgae grow in the 20 km2 Hartbeespoort Dam to a concentration of 160 g/m2 during the six warmest months of the year; a harvesting section where excess water is removed from the micro-algal biomass; a reaction section where fatty acid oils are extracted from the microalgae and converted to biodiesel, and dry biomass rests are combusted to supply heat for the extraction and biodiesel units of the reaction section. The cultivation section consist of the existing Hartbeespoort Dam, which make up the cultivation unit; the harvesting section is divided into a collection unit (dam wall part of the Hartbeespoort Dam), a concentration unit, a filtration unit, and a drying unit; the reaction section consists of an oil extraction unit, a combustion unit, and a biodiesel unit. At a capital cost of R71.62 million (R1.11/L) (±30%), the new proposed BTL facility will turn 933,525 tons of raw biomass (1.5% TSS) into 2,590,856 litres of high quality biodiesel per year, at an annual operating cost of R11.09 million (R4.28/L at 0% producer inflation), to generate R25.91 million (R10.00/L) per year of revenue. At the current diesel price of R10.00/L, the new integrated BTL process is economically feasible with net present values (NPV) of R368 million (R5.68/L) and R29.30 million (R0.45/L) at discount rates of 0% and 10%, respectively. The break-even biodiesel prices are R5.34/L and R7.92/L, for a zero NPV at 0% and 10% discount rates, respectively. The cultivation of micro-algal biomass from the Hartbeespoort Dam is only economical if the growth is allowed to occur naturally in the dam without any additional cultivation equipment. The cultivation of micro-algal biomass in either an open or a closed-cultivation system will not be feasible as the high cost of cultivation will negate the value of biodiesel derived from the cultivated biomass. The utilization of the three promising harvesting methods described in this work is one of the main drivers for making this process economically feasible. At a capital cost of R13.49 million (R37.77/ton of dry weight micro-algal biomass) and a operating cost of R2.00 million per year (R210.63/ton of dry weight micro-algal biomass) for harvesting micro-algal biomass from the Hartbeespoort Dam, harvesting costs account for only 19% and 18% of the overall capital and operating costs of the new process, respectively. This is less than harvesting costs for other comparative processes world-wide, which contribute between 20 and 30% of the overall cost of biomass-to-liquids production. At current fuel prices, the cultivation of micro-algal biomass from and next to the Hartbeespoort Dam is not economical, but the unconventional harvesting methods presented in this thesis are feasible, if incorporated into the new integrated biomass-to-liquids biodiesel process set out in this work.
Thesis (Ph.D. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

Algae that are grown in wastewater treatment lagoons could be an important substrate for biofuel production; however, the low C/N ratio of algae is not conducive to anaerobic digestion of algae with economically attractive methane production rates. Increasing the C/N ratio in anaerobic, laboratory scale, batch reactors by blending algal biomass with sodium acetate resulted i increased methane production rates as the C/N ratio increased. The highest amount of methane was produced when the C/N was 21/1. When the C/N was 24/1, the biogas production rate decreased. Batch experiments were done to evaluate the effect of optimizing the C/N ratio on methane production from algae and to identify the most essential information needed to conduct research on co-digestion of algal biomass using the continuous, high-rate, up-flow anaerobic sludge blanket (UASB) reactor system. Based on the results obtained from batch reactor experiments, anaerobic co-digestion of algal biomass, obtained by continuous centrifugation from the Logan City, Utah, 5th stage wastewater treatment lagoon, and sodium acetate was conducted using laboratory scale UASB reactors with the C/N ratio in the feedstock adjusted to 21/1. Duplicate, 34 L UASB reactor systems were built of poly(methyl methacrylate). Both reactors were seeded with 11 L of anaerobic sediment from the 3rd stage lagoon. The pH of the feedstock was adjusted to the neutral range. The feedstock was initially introduced at a low organic loading rate of 0.9 g/L.d with a hydraulic retention time (HRT) of 7.2 days and then increased up to 5.4 g/L.d and a HRT of 5.5 days. These organic loading rates corresponded to an initial influent chemical oxygen demand (COD) of 6.25 g/L and increased to 27.2 g/L. Methane production increased from 270 mL/g to 349 mL/g COD biodegraded. COD removal efficiency was 80% and biogas methane composition was 90% at steady state. Algal biomass contributed 33-50% of the COD in the feed stock depending on the COD of the algae paste from centrifugation. The shortest HRT at which steady state was not affected was 5.5 days. At lower HRT all monitored parameters showed a slight decrease after the 75th day of operation.

This thesis covers work carried out on algae bioreactors as a tertiary treatment process for wastewater treatment. The process was primarily assessed by the removal of Phosphorus and Nitrogen as an alternative to chemical and bacterial removal. Algal bioreactors would have the added advantage of carbon sequestration and a by-product in the energy rich algal biomass that should be exploited in the existing AD capacity. Laboratory scale bioreactors were run (4.5-30L) using the secondary treated final effluent from the local Loughborough sewage works. In a preliminary series of experiments several different bioreactor designs were tested. These included both batch feed and continuous flow feed configurations. The bioreactors were all agitated to keep the algal cells in suspension. The results demonstrated that the most effective and easy to operate was the batch feed process with the algal biomass by-product harvested by simple gravitational settling. Experiments also compared an artificial light source with natural light in outdoor experiments. Outdoor summer light produced greater growth rates but growth could not be sustained in natural UK winter light. Light intensity is proportional to productivity and algae require a minimum of around 97W/m2 to grow, an overcast winter day (the worst case scenario) was typically around 78W/m2, however this was only available for a few hours per day during Nov-Jan. The process would be better suited to areas of the world that receive year round sunlight. It was shown that phosphorus could be totally removed from wastewater by the algae in less than 24 hours depending on other operating variables. With optimisation and addition of more carbon, a HRT of 10-12 hours was predicted to achieve the EU WFD / UWWTD standard. It was further predicted that the process could be economically and sustainably more attractive than the alternatives for small to medium sized works. Biomass 3 concentrations of between 1-2g/L were found to best achieve these removals and produce the fastest average growth rates of between 125-150mg/L/d. The uptake rates of phosphorus and nitrogen were shown to be dependent on the type of algae present in the bioreactor. Nitrogen removal was shown to be less effective when using filamentous bluegreen algae whilst phosphorus removal was almost completely stopped compared to unicellular green algae that achieved a nitrogen uptake of 5.3mg/L/d and phosphorus uptake of 8mg/L/d. Soluble concentrations of Fe, Ni and Zn were also reduced by 60% in the standard 10 hours HRT. The predominant algae were shown to depend largely on these concentrations of phosphorus and nitrogen, and the strain most suited to that specific nutrient or temperature environment dominated. Nutrient uptake rates were linked to algal growth rates which correlated with the availability of Carbon as CO2. CO2 was shown to be the limiting factor for growth; becoming exhausted within 10 hours and causing the pH to rise to above 10.5. The literature showed this was a common result and the use of CO2 sparging would more than double performance making this process a good candidate for waste CO2 sequestration. Heat generated from combustion or generators with exhaust CO2 would also be ideal to maintain a year round constant temperature of between 20-25°C within the bioreactors. A number of possible uses for the algal biomass generated were examined but currently the most feasible option is wet anaerobic co-digestion. Further economic analysis was recommended on the balance between land area and complementary biomass generation for AD. It was also suggested given the interest as algae as a future fuel source, the process could also be adapted for large scale treatment and algal biomass production in areas of the world where land was available.

The Sundays Estuary is permanently open to the sea and has been described as channel-like along its entire length with a narrow intertidal area (mostly less than 5 - 6 m in width). The estuary experiences regular freshwater inflow with large supplies of nutrients, derived from the Orange River transfer scheme and agricultural return flow. In particular, nitrate concentrations are high as a result of fertilisers used in the Sundays River catchment area. The objectives of this study were to measure microalgal biomass and community composition and relate to flow, water quality and other environmental variables. Surveys in August 2006, March 2007, February, June and August 2008 showed that salinity less than 10 percent mostly occurred from 12.5 km from the mouth and this was also where the highest water column chlorophyll a (>20 μg l-1) was found. Different groups of microalgae formed phytoplankton blooms for the different sampling sessions, which were correlated with high chlorophyll a. These included blooms of green algae (August 2006), flagellates (March 2007), dinoflagellates (June 2008) and diatom species (February and August 2008). The dominant diatom (Cyclotella atomus) indicated nutrient-rich conditions. Green algae and diatoms were associated with low salinity water in the upper reaches of the estuary. Flagellates were dominant throughout the estuary particularly when nutrients were low, whereas the dinoflagellate bloom in June 2008 was correlated with high ammonium and pH. Maximum benthic chlorophyll a was found at 12.5 km from the mouth in February, June and August 2008 and was correlated with high sediment organic and moisture content. Benthic diatoms were associated with high temperature whereas some species in June 2008 were associated with high ammonium concentrations. The middle reaches of the estuary characterise a zone of deposition rather than suspension which would favour benthic diatom colonization. Phytoplankton cells settling out on the sediments may account for the high benthic chlorophyll a because maximum water column chlorophyll a was also found in the REI zone (where salinity is less than 10 percent and where high biological activity occurs) in the Sundays Estuary. The estuary was sampled over five consecutive weeks from March to April 2009 to identify environmental factors that support different microalgal bloom species. Phytoplankton blooms, defined as chlorophyll a greater than 20 μg l-1, were found during Weeks 1, 4 and 5 from the middle to the upper reaches of the estuary. Diatom species (Cylindrotheca closterium, Cyclotella atomus and Cyclostephanus dubius) occurred in bloom concentrations during these weeks. These diatom species are cosmopolitan and indicate brackish nutrient-rich water. Flagellates were the dominant group in Weeks 2 to 4, but positive correlations with chlorophyll a were found during Weeks 1 and 2. During the first week of this study the conditions were warm and calm (measured as temperature and wind speed) and there was a well developed bloom (38 μg l-1). There was a strong cold front from 17 to 19 March, which mixed the water column resulting in the decrease of the chlorophyll a levels (<20 μg l-1) and the bloom collapsed during Weeks 2 and 3. However, in Weeks 4 and 5 conditions were again calm and warmer, which appeared to stimulate the phytoplankton bloom. Nanoplankton (2.7 - 20 μm) was dominant during each week sampled and contributed a considerable amount (55 - 79 percent) to the phytoplankton biomass. Once again subtidal benthic chlorophyll a and water column chlorophyll a were highest 12.5 km from the mouth. Deposition of phytoplankton cells from the water column was evident in the benthic samples. The study showed that the Sundays Estuary is eutrophic and characterised by microalgal blooms consisting of different phytoplankton groups.

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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.

Acid rmne drainage (AMD) is a major pollution problem througbout the world, adversely affecting both surface and groundwaters. AMD is principally associated with the mining of sulphide ores. The most commonly associated minerals being sulphur, copper, zinc, silver, gold, lead and uranium. As conventional methods for removing heavy metals from wastewater are often prohibitively expensive, the implementation of biological processes for the removal of heavy metals has become a realistic practice. The objectives of this project was firstly to establish the effect of copper, lead and nickel, heavy metals commonly found in AMD waters, on the enzyme carbonic anhydrase, which is an integral part of the carbon concentrating mechanism (CCM) and secondly, to determine the feasibility of using the alkalinity generated by Spindina for the precipitation of heavy metals from solution. Initially, batch flask experiments were performed and it was found that the algae were able to utilise the bicarbonate supplied in the medium, under CO, limiting conditions, through the induction of their CCM, resulting in the generation of carbonate. The effect of the inhibitors, acetazolamide (AZ) and ethoxyzolamide (EZ), were also investigated in order to determine the importance of carbonic anhydrase (CA) in inorganic carbon accumulation and photosynthesis. Results obtained were consistent with those observed in literature and it was found that at IOOf.LM AZ and EZ, complete inhibition of photosynthesis and carbonic anhydrase occurred, with no oxygen being evolved. The results obtained from the inhibitor experiments substantiate the findings that carbonic anhydrase is an important part of the CCM, and that the dehydration of bicarbonate to carbon dioxide and hydroxide ions, is in fact an enzymatic process regulated by the enzyme carbonic anhydrase and is essential for efficient photosynthesis. The effect of heavy metals on Spirulina was also investigated. Lead, copper and nickel were all found to cause a reduction in the synthesis of chlorophyll a, which resulted in a decrease in photosynthetic efficiency and eventually death of the culture. The morphology of the algae was also severely affected by heavy metals, with degradation and aJmost complete disintegration of the algal filaments occurring. Using the Wilbur-Anderson assay method, carbonic anhydrase activity was found to be lower in the experimental flasks containing heavy metals, than the control flasks, reducing the algae's ability to utilise the bicarbonate in solution for effective photosynthesis. The Wilbur-Anderson assay method did not prove to be a reliable method for measuring changes in enzyme activity as results were found to be erratic. Therefore attempts were made to use an oxygen electrode as an alternative method for determining the effects of various parameters on enzyme activity and photosynthesis, this proved to be more successful. Because of the toxic effects of heavy metals on Spirulina it was decided that the use of the biogenic alkalinity generated by the algae for the precipitation of heavy metals may be successfully employed as an alternative method for bioremediation and metal recovery. Carbonate reacts readily with metals, therefore the carbonate produced by this algal system was used for the precipitation of metals. It was possible to categorise the precipitation reactions observed into three groups, namely those metals which, a) precipitate as hydroxides, b) precipitate as carbonates generated from the dissociation of bicarbonate and c) metals which can only precipitate if there is free carbonate present in solution.

Nutrient limitation in aquatic ecosystems results from a deficiency in nitrogen or phosphorus levels relative to cellular growth needs. Nutrient limitation of freshwater systems is a function of biotic and abiotic factors. Biotic factors include vascular and nonvascular plant community composition. Abiotic factors include underlying bedrock and land-use activities (e.g. agriculture, septic systems). Nutrient availability directly affects growth, productivity, and community structure of primary producers. The purpose of this study was two-fold: (1) to assess the relationship between ambient algal biomass. and in-stream nutrient levels along the longitudinal course of a river through a transition from weak to well-developed underlying karst bedrock, and (2) experimentally assess if periphyton was nitrogen or phosphorous limited between weak and well-developed karst sites. Sestonic and filamentous biomass (= chlorophyll-a) levels increased monthly along the longitudinal gradient. In contrast, periphyton biomass levels increased minimally monthly and displayed no longitudinal pattern. Nitrate and soluble reactive phosphorus levels exhibited distinct longitudinal increases, whereas total phosphorous displayed minimal change and ammonia levels decreased in the downstream direction. Total nitrogen (TN) levels increased upstream but decreased sharply in the well-developed downstream karst sites. The nutrient limitation assays revealed that the highest periphyton levels were with N + P treatments at the most upstream sites. Overall, in Kentucky's Green River algal biomass accrual appears to be mainly P-limited but likely also by TN availability during late summer.

An instrumented ferry made eight transects per day across the Fraser River plume over the years 2003 - 2006 as part of the STRATOGEM program to study biophysical coupling in the Strait of Georgia. Water temperature, salinity, chlorophyll-a fluorescence, nitrate concentration, and dissolved oxygen were measured. This thesis utilizes salinity and chlorophyll-a fluorescence to study mixing in the plume, and the impact of the plume on algal biomass. First, the effects of river discharge and tides on plume salinity and surface area are quantified. Tidal fluctuations are caused by advection of the estuarine salt field, while fortnightly variations are caused by modulation of mixing in the estuary. Tidal and fortnightly variations are strongest at high river discharge and weakest at low discharge. Plume salinity decreases quasi-linearly with river discharge. Plume surface area increases with river discharge, from about 300 km² at low river flow to about 1,200 km² at high river flow, and can be predicted by scaling the river mouth deformation radius. Second, the plume fresh water flushing time is estimated and a salinity budget is constructed. Fresh water flushing time is 2.2 days, independent of river discharge. The quasi-steady budget predicts a vertical entrainment flux which varies with river discharge. The discharge-dependent vertical entrainment velocities in the estuary and plume implied by the entrainment flux are consistent with other methods. Flow speeds at the edge of the plume estimated from this method are too weak to maintain a plume front, suggesting fronts are transient and created on tidal time-scales. Third, a time series of surface and depth-integrated chlorophyll-a biomass is constructed. Chlorophyll-a fluorometer data are corrected for fluorescence quenching with a parameterization specific to the region, and then calibrated with extracted samples. Instantaneous along-track differences in surface chlorophyll-a can be large, however, averaged over the whole time series, the distribution is nearly uniform. In contrast, depth-integrated values are about 35% lower on average in the plume compared to surrounding waters. Interannual variability in biomass is partly due to the magnitude and duration of the spring bloom, which is itself influenced by wind mixing and grazing.

Microalgae are gaining more attention for several reasons such as being potential producers of sustainable fuel, for use as health supplements and in skincare. Simris Alg is a Swedish company that produces Omega 3 supplements from a primary producer of these fatty acids - the algal diatom Phaeodactylum tricornutum, which is a sustainable alternative to Omega 3 derived from fish. Omega 3 fatty acids constitute a small fraction of the total algal biomass, and to increase profitability and utilize all of the biomass, the purpose of this thesis project is to present potential applications for the residual material that is left after oil extraction. A general composition study was made of Simris Alg algal residue material, and results are compared to those found in previous studies of P. tricornutum biomass. An optimization of the fractionation is needed to separate the storage carbohydrate chrysolaminarin and cell wall component glucuronomannan, followed by analysis for confirmation. Also, it would be interesting to separate chitin, if there is any, since despite the presence of chitin synthases, it is unclear whether the diatom actually produces chitin. When gathering information, no actual experimental characterization of carbohydrate active enzymes involved in synthesis of the main carbohydrates investigated were found. Such information would be useful to increase production of the carbohydrate of interest, if valuable applications are found. Potential applications of various cell components, such as carbohydrates, in skincare would be interesting to investigate, as well as optimizing fucoxanthin extraction for use as an additional high value product next to Omega 3.

The production of cyanobacterial biofilm biomass and phycocyanin from Rotating Algal Biofilm Reactors utilizing undiluted produced water from oil and natural gas extraction as a culture medium was investigated in this study. Produced water is the largest waste stream generated by the oil and natural gas industries and represents a large volume of non-potable water that may be available for algae culture with minimal impact on freshwater resources. Combining the use of produced wastewater as culture medium with the production of high value algal pigments, such as phycocyanin, may increase the economic viability of algae culture and wastewater purification. High value phycocyanin pigment production and methods to increase phycocyanin yields with light limitation were examined in this study. A unique cyanobacteria species was isolated from the Logan City Wastewater Treatment Facility in Logan, Utah and used in conjunction with the Rotating Algal Biofilm Reactor platform for the duration of this study. Between the “high” and “low” light treatments used in this study, the high light treatment showed nearly twice the biomass production as the low light culture (4.8±0.7 vs. 2.7±0.4 g/m2-day). The low light biomass contained 87.6% more of the phycocyanin pigment, with a 230% increase in purity, then the biomass from the high light treatment. The areal footprint productivity of phycocyanin per day was the same for both the light treatments. An evaluation of growth attachment materials was conducted with cotton rope and cotton conveyer cloth materials found to be the most durable and having the highest yields of harvestable biomass. The cotton rope and cotton conveyor cloth materials were evaluated on a floating Rotating Algal Biofilm Reactor operating in a 2000 L outdoor produced water pond. The cotton rope yielded a 140% increase in biomass vs. the cotton cloth although the compositions varied greatly. The cotton cloth biomass was composed of mainly healthy algae with higher phycocyanin yields while the cotton rope showed a higher proportion of non-algae organisms and little phycocyanin. These results show promise for the utilization of produced water to grow cyanobacteria biofilms with modifiable biomass characteristics as a source of high value phycocyanin pigments.

In this study, the effects of biological and physical disturbance on algal assemblages on cobbles in rainforest streams were investigated. Study sites in two rainforest streams, Stony Creek and Booloumba Creek, located in south- east Queensland, were used for both a regular sampling program and an extensive experimental schedule. Previous research has shown that physical disturbance due to spates and, in the absence of high discharge events, biological disturbance due to invertebrate grazing exert significant structuring and controlling forces on periphyton assemblages in streams. The principal objectives in this study were to deternine the relative importance of physical disturbance in the form of spates and desiccation, to outline the significance of biological effects, in particular as a result of grazing pressure, and to describe algal succession on substrates cleared after disturbance events. Periphyton chlorophyll a, biomass values and grazer numbers were monitored over a period of two years in relation to rainfall and stream discharge (to pinpoint the incidence of spates). Periphyton assemblages were composed mainly of diatoms (Cocconeis and Navicula being the dominant genera). Physical disturbance by spates was clearly an important factor structuring stream algal assemblages. Periphyton chlorophyll a and biomass values were reduced following a high discharge event, but then recovered relatively fast in the absence of any other disturbance. Furthermore, chlorophyll a values were correlated with grazer numbers. Differences were observed in the epilithon of Stony Creek and Booloumba Creek: while cobbles in the former supported more chlorophyll a containing material of algal origin and less non-algal biomass, the reverse was true for latter stream. This was most probably due to the physical characteristics of the two stream channels, primarily their slope, which was considerably steeper in Stony Creek, thus requiring less depth to facilitate a major disturbance event. This means that the physical characteristics of streams are most important determining factors regarding the effects of high discharge events, with the disturbance regime playing a significant role in the composition of the stream benthos. However, some major changes in chlorophyll a and biomass occurred in the absence of big disturbances. Periphyton on cobbles collected in the streams was subjected to various time periods out of the water to determine the effects of desiccation. Diatom assemblages on cobbles were not resistant to desiccation and did not recover following re-immersion in the streams. Thus, periods of low flow are capable of reducing periphyton assemblages, however, this type of disturbance would take place over a longer period compared to spates. A colonization experiment where polyethylene foils were introduced into the streams was used to monitor algal succession on bare substrates. Diatoms were the only algae which colonized experimental foils, exhibiting distinct successional patterns in both streams. A series of grazer manipulation experiments were employed to test for any effects of grazing; this involved the inclusion / exclusion of caddisfly larvae from cobbles enclosed in screened perspex cylinders. Signficantly, the effects of grazing invertebrates resulted in an increase in chlorophyll a and biomass values, contrary to expectations and the majority of past studies. This could mean that grazers at a certain density may actually stimulate algal growth and there exists a fine balance between when grazer numbers enhance periphyton productivity or periphyton is overgrazed. Overall, results obtained indicated that variations in stream algal assemblages were a consequence of the combined effects of spates, low flows and, to a lesser extent, grazing.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Graduate School of Environmental Science and Engineering
Science, Environment, Engineering and Technology
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Orientador: Lucia Helena Sipauba Tavares
Resumo: A microalga Haematococcus pluvialis apresenta elevado interesse biotecnológico e comercial devido sua capacidade de síntese de compostos de alto valor e composição nutricional rica em proteínas, aminoácidos e outros compostos. Dentre os entraves em sua produção comercial, a obtenção de elevada biomassa tem sido o foco de diversas pesquisa que buscam otimizar o cultivo desta espécie. O cultivo mixotrófico é uma ferramenta que pode auxiliar na obtenção de elevadas produtividades, no entanto a fonte de carbono utilizada nestes cultivos deve ser adequada e disponibilizada de forma correta para completa absorção. O melaço de cana de açúcar é uma fonte de carbono rica em sacarose e nutrientes podendo ser empregado no cultivo de H. pluvialis, no entanto, requer pré-tratamento antes de seu uso. A hidrólise auxilia na redução das moléculas de sacarose em glicose e frutose, aumentando a disponibilidade de carbono e facilitando sua assimilação. Comparado ao melaço in natura, a hidrolise do melaço demonstrou melhores resultados aumentando a produtividade e alta composição bioquímica. Outra ferramenta importante utilizada na otimização dos cultivos algais em condições mixotróficas é o uso de ciclos de luz, uma vez que a luminosidade está relacionada diretamente ao metabolismo algal auxiliando na assimilação dos nutrientes e do carbono. O período de iluminação fornecida varia de espécie para espécie, podendo ou não ser necessário. Neste estudo e para estas condições de cultivo, foram obser... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The Haematococcus pluvialis microalgae displays high biotechnological and commercial interest due to its capacity to synthesize high nutritional value in protein, amino acids and other compounds. Besides the difficulties in commercial production, the obtaining of high biomass amounts has been the objective of several researches which seek to optimize the production of this species. The mixotrophic culture is a tool which may improve the obtention of higher productivity. However, the carbon source for the cultures have to be adequate and has to be in an available form in order to be completely absorbed. The cane molasse is a carbon source rich in saccharose and nutrients and might be employed in H. pluvialis culture. Nevertheless, it requires a pre-treatment for its use. The hydrolysis promotes the reduction of saccharose molecules into glycose and fructose, improving the carbon availability and assimilation. In comparison to in natura molasses, the hydrolysis improved the results by increasing productivity. Light cycle is another important tool for algae culture in mixotrophic conditions, since light is directly related to the algae metabolism, which improves the carbon and nutrients assimilation. The light interval varies according to species and may or may not be necessary to be employed. In this study, an increase in biomass and biochemical composition was observed when H. pluvialis was exposed to light cycles. The best results were obtained with a 20:4 hours cycle (light/... (Complete abstract click electronic access below)
Doutor

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.

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.

Tese(doutorado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2011.
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Microalgas marinhas são organismos ricos em lipídios e ácidos graxos, de grande interesse devido ao seu potencial biotecnológico. O objetivo desta tese foi determinar possíveis efeitos sinergéticos da intensidade luminosa (40 e 400mol fótons m-2s-1), temperatura (15 e 30°C), fonte de nitrogênio (NO3- e NH4+) e fase de crescimento (logarítmica e estacionária), sobre o conteúdo e a produtividade de lipídios e ácidos graxos de duas microalgas marinhas Nannochloropsis oculata e Thalassiosira weissflogii. Além disso, foi avaliado, também, como o uso de floculantes aniônicos e catiônicos podem influenciar a extração de lipídio e o perfil de ácidos graxos produzidos por estas microalgas. Os maiores conteúdos e produtividade dos lipídios para ambas as espécies ocorreram em tratamentos com maior intensidade luminosa (400 mol fótons m-2 s-1) e utilizando nitrato como fonte de Nitrogênio. N. oculata acumulou mais lipídios na fase estacionária, enquanto que em T. weissflogii maiores concentrações de lipídios só ocorreram na fase estacionária de tratamentos com menor temperatura (15º C). As duas espécies apresentaram maior produtividade de lipídios em tratamentos com maior produção de biomassa de microalgas. Entretanto, células de N. oculata que cresceram no tratamento com amônio e elevada luminosidade apresentaram grande produtividade de lipídio devido a elevados níveis de concentração deste elemento nas células e não devido ao maior crescimento celular. Portanto uma maior produtividade pode ser obtida empregando estratégias de cultivo que beneficiam, simultaneamente, o crescimento celular e/ou o acúmulo de lipídios nas células. Os ácidos graxos com maior conteúdo em ambas as espécies foram C14:0, C16:0, C16:1, C18:1 e C20:5. Para as duas espécies, maiores concentrações de ácidos graxos saturados e monoinsaturados foram obtidos em tratamentos com maior temperatura (30º C). Ácidos graxos poli-insaturados (PUFAS), especialmente o ácido eicosapentaenóico (C20:5), foi produzido em maior quantidade por N. oculata em tratamentos com baixa luminosidade e Nitrato. O uso de floculantes não alterou a quantidade de lipídios extraídos de ambas as espécies. Entretanto, o floculante aniônico diminuiu o conteúdo de C20:5 em N.oculata, enquanto que em T. weissflogii, os floculantes aniônico e catiônico reduziram os conteúdos de C18:0 e C18:1n9c
Marine microalgae are rich in lipids and fatty acids. These microorganisms are of great interest, mainly due to their biotechnological potential. The aim of this thesis was to determine possible synergistic effects of light intensity (40 and 400 mol photons m-2s-1), temperature (15 and 30° C), nitrogen source (NO3- and NH4+), and growth phase (logarithmic and stationary) in the productivity, content of lipids and fatty acids in two marine microalgae: Nannochloropsis oculata and Thalassiosira weissflogii. Moreover, it was evaluated if the use of anionic and cationic flocculants can influence the extraction of lipids and fatty acid profiles produced by these species. The higher lipid content and productivity for both microalgae occurred in treatments with higher light intensity (400 mol photons m-2 s-1), and with nitrate as nitrogen source. N. oculata accumulated more lipids in the stationary phase, while higher concentrations of lipid in T. weissflogii occurred only in stationary phase from treatment with a lower temperature (15° C). The two microalgae species showed higher lipid yields in treatments with higher biomass production. However, during N. oculata cells grown, the treatment with ammonium and high light showed large lipid productivity due to high concentrations of this element in the cells, and not due to increased cell growth. Therefore highest lipid productivity can be achieved using cultivation strategies that benefit both cell growth and accumulation of lipids in cells. The fatty acids with greater content of both species were C14:0, C16:0, C16:1, C18:1 and C20:5. Higher concentrations of saturated and monounsaturated fatty acids were obtained in treatments with higher temperature (30° C) in both species. Polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (C20:5), was produced in greater amounts by N. oculata in treatments with low light and nitrate. The use of flocculants did not alter the amount of lipids extracted from both species. However, the anionic flocculant decreased content of C20:5 in N. oculata, while for T. weissflogii, the cationic and anionic flocculants reduced content of C18:0 and C18:1n9c.

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.