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.

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.

The consequences of introducing riparian shade on in-stream community structure has not been well explored in south-eastern Australia. With catchment managers focusing on revegetation of riparian zones, there is a need to understand, monitor, and predict changes in ecological patters and processes that may take place as a system shifts from an open to a shaded stream community. Presented in this thesis is a conceptual model portraying possible responses of a macrophyte community to light reduction as a result of the introduction of riparian vegetation. This model was tested in the field by artificially shading sites (three shade treatments) to observe the direct effects of light reduction on Phragmites australis growth and structure and flow-on effects to associated in-stream biota." / Doctor of Philosphy

A prevailing view exists in the literature which suggests that macroalgae growing in slow-flow environments (<4 cm s⁻�) are less productive because of "mass-transfer" limitation compared to fast-flow environments. Macroalgae in slow-flow environments are thought to have thicker diffusion boundary-layers which limit the flux of essential molecules to and from the algal thallus. However nutrient demand of a macroalga can also influence nutrient flux. The main objective of this research was to determine the relative importance of physical (mainstream velocity) and physiological (nutrient demand) factors influencing the growth rate of Adamsiella chauvinii, a small (<20 cm) red algal species, that grows within the benthic boundary-layer in a soft sediment habitat. To establish the influence of water velocity, the growth rate of A. chauvinii was measured in situ each month (March 2003 to March 2004) at three sites with varying degrees of water velocity (slow, intermediate and fast) at which all other environmental parameters (photon flux density, seawater temperature and nutrients) were similar. To determine the metabolic demand and nutrient uptake rate of A. chauvinii, the internal nutrient status (C:N, soluble tissue nitrate, ammonium and phosphate), uptake kinetics (V[max] and K[s]) and nutrient uptake rate at a range of mainstream velocities were also determined on a seasonal basis. The hydrodynamic environment around A. chauvinii canopies was characterised in situ and compared with controlled laboratory experiments. Growth rates of Adamsiella chauvinii thalli at the slow-flow site were significantly lower in winter (June) to summer (February) than the intermediate- and fast-flow sites, while in autumn growth rates were similar between sites. However, A. chauvinii at the slow-flow site had similar or higher tissue N content compared to thalli at the other two sites during winter, spring and summer suggesting that growth rates of A. chauvinii were not mass-transfer limited. Nitrogen uptake rates of A. chauvinii were similar between sites in summer and winter, however uptake rates were lower in summer compared to winter even though thalli were nitrogen limited in summer. Water velocity had no effect on nitrate uptake in either summer or winter and uptake of ammonium increased with increasing water velocity during summer only. Two hydrodynamically different environments were distinguished over a canopy of A. chauvinii, with both the laboratory and field velocity profiles in good agreement with each other. In the top half of the canopy, the Turbulent Kinetic Energy (TKE) and Reynolds stresses were greatest while in the bottom half of the canopy flow rates were less than 90 % of mainstream velocity (< 1 cm s⁻�). When considered together, the influence of water velocity on the growth rates of A. chauvinii was not completely clear. Results suggest that mainstream velocity had little influence on nutrient availability to A. chauvinii because of the unique hydrodynamic environment created by the canopy. Nutrients, especially ammonium and phosphate, derived from the sediment and invertebrates, may provide enough nitrogen and phosphate to saturate the metabolic demand of Adamsiella chauvinii, consequently, A. chauvinii is well adapted to this soft-sediment environment.

The consequences of introducing riparian shade on in-stream community structure has not been well explored in south-eastern Australia. With catchment managers focusing on revegetation of riparian zones, there is a need to understand, monitor, and predict changes in ecological patters and processes that may take place as a system shifts from an open to a shaded stream community. Presented in this thesis is a conceptual model portraying possible responses of a macrophyte community to light reduction as a result of the introduction of riparian vegetation. This model was tested in the field by artificially shading sites (three shade treatments) to observe the direct effects of light reduction on Phragmites australis growth and structure and flow-on effects to associated in-stream biota." / Doctor of Philosphy

Metal pollution has been a great challenge in most industrialized countries as a result of waste generated from industrial activities being introduced into the environment. Unicellular green algae have been considered a potential biological tool for bioremediation of metal pollutants due to its metal sequestration properties. However, methods for further improving unicellular green algae metal sequestration by manipulating metal uptake and tolerance in unicellular green algae have not been studied in detail. In this study, a family metal transport protein named MTP1 - MTP4 from C. reinhardtii were screened by yeast heterologous expression for metal transport activity. MTP1 was able to strongly rescue the Zn and Co sensitivity of the zrc1cot1 strain, MTP3 could weakly mediate Zn and Co growth, but MTP2 and MTP4 appeared to have no Zn or Co tolerance activity. MTP2, MTP3 and MTP4 but not MTP1 could strongly rescue the Mn sensitivity of the pmr1 strain. When MTP4 was over-expressed in C. reinhardtii the strain showed a significant increase in Cd tolerance compared to the wild type, but no significant difference in Mn tolerance and uptake. AtHMA4 a Zn2+ and Cd2+ transporter from the plant Arabidopsis thaliana, which is a member of the Heavy Metal ATPase family, was also expressed in C. reinhardtii. HMA4 full length and C-terminal tail expression strains were screened for Zn and Cd tolerance and uptake. Both sets of strains showed a significant increase in Cd and Zn tolerance and uptake compared to the wild type. Metal tolerance and uptake was compared between the genetically engineered C. reinhardtii strains and unicellular green algal strains that are naturally adapted to metal tolerance which were P. hussi, P. kessleri, and C. luteoviridis. Results showed significant increase in Zn and Cd tolerance and uptake in the natural strains compared to the engineered strains. Therefore in addition to genetically engineered strains, naturally adapted strains could also be used as tools for effective metal bioremediation and pollutant treatment.

The aim of the work was to examine microalgae growth and nutrient elimination in various diluted digestates in the first trial, then to study CO2 removal from a simulated biogas mixture by the same strain in the second trial. Scenedesmus SCCP K-1826 was cultivated in the digestate from Sundet biogas plant diluted 10, 20 and 30 times. The cultures were open-air with occasional CO2 injections to control pH. On day 15, the best growth was obtained in the 10 times diluted sample. COD, TN and TP removal efficiencies were similar in each bottle as the strain didn’t perform better in any specific dilution. The control proved that additional mechanisms other than photosynthesis contributed to digestate cleaning. Using the 10 times diluted sludge, Scenedesmus was grown in sealed flasks filled with simulated biogas (35.3 % CO2 + 32.3 % CH4 + 32.3 % N2). More algal biomass was produced in this batch culture. Nutrient removal efficiencies were close to the ones reached in the open-air flasks. After 10 days, 96 % of carbon dioxide was reduced. Methane content was depleted as well, possibly due to undesirable methane oxidizing bacteria which infiltrated the medium.

This Ph.D. thesis deals with principles of microalgae cultivation in laboratory as well as outdoor aquacultures (Chapter 1) using various cultivation systems and photobioreactors (Chapter 2). Case studies illustrate the main research topic as to correlate changes in growth rate with variation of photosynthetic activity, physiological features and biomass composition (Chapter 3). Special attention was paid to elaboration of protocols of chlorophyll a fluorescence techniques for monitoring the physiology and photosynthetic performance of microalgae mass cultures maintained under various growth conditions (Chapter 4).

Os efluentes líquidos de curtumes apresentam altas cargas orgânicas e de poluentes que devem ser tratados corretamente para atingir os padrões legais para seu descarte, evitando a eutrofização de corpos hídricos e poluição das águas. O acabamento do couro é o estágio final da produção, onde o couro recebe as características desejadas de acordo com os produtos e artigos que serão produzidos. Os efluentes das etapas de processamento para acabamento do couro são responsáveis por conterem poluentes químicos devido ao uso de corantes, surfactantes, metais tóxicos, agentes emulsificantes, recurtentes, óleos, pigmentos, resinas, entre outros produtos químicos adicionados. As microalgas têm sido alvo de vários estudos no âmbito de tratamento de efluentes, devido à sua capacidade de remover diversos nutrientes, matéria orgânica do meio e por serem formas mais limpas e econômicas de tratar os poluentes. Diante disto, o objetivo deste trabalho foi avaliar o emprego de um consórcio de microalgas para tratamento de efluentes de um curtume e analisar a capacidade de remoção de poluentes que são nutrientes para estes microrganismos. Os efluentes foram caracterizados ao longo dos ensaios com o consórcio de microalgas por meio de Nitrogênio Total (NT), Amônia (NH3), Fósforo (P-PO4), Carbono total (CT), Carbono Orgânico Total (COT), Carbono inorgânico (CI), DQO e Demanda Biológica de Oxigênio (DBO) e foi acompanhado o crescimento das microalgas. Para os experimentos foram coletados efluentes em três estágios distintos em uma estação de tratamento: efluente bruto (B), efluente após tratamento primário de coagulação/floculação (P) e efluente após ao tratamento biológico secundário (S). Os resultados com concentração de efluente de 50%, diluídos em água destilada (A), após 16 dias de cultivo, mostraram que houve crescimento do consórcio nos três efluentes com um crescimento máximo de 1,77 g L-1 no efluente Bruto (50B50A). Na sequência, foi testado o cultivo em efluente bruto (100B) e em efluentes compostos nas seguintes proporções: 50% efluente bruto + 50% efluente após tratamento biológico (50B50S) e 25% efluente bruto + 75% efluente após tratamento biológico (25B75S). Foi possível cultivar o consórcio no efluente bruto sem diluição, entretanto os resultados foram ruins, pois o mesmo apresentou baixo crescimento e, consequentemente, baixos níveis de remoção de nutrientes. Com o efluente composto 25B75S percebeu-se morte rápida das microalgas, uma vez que o efluente apresentava baixas concentrações de nutrientes. Em contrapartida, no efluente 50B50S foram atingidos valores efetivos de crescimento e remoção de nutrientes. Em cultivos fotoautotrófico, mixotrófico e heterotrófico de efluente composto 50B50S e de 75% efluente bruto + 25% efluente após tratamento biológico (75B25S), os melhores resultados foram atingidos no efluente 75B25S no cultivo fotoautotrófico, crescendo até 1,42 g L-1 e atingindo valores de remoção de NNH3, Nitrogênio Total (NT), DQO, carbono orgânico total (TOC) e demanda biológica de oxigênio (DBO5), de 99,90%, 74,89%, 56,70%, 58,18% e 20,68%, respectivamente. Ao obter a microalga isolada Tetraselmis sp. predominante no consórcio foi analisado os parâmetros anteriores em cultivo fotoautotrófico, além disso foi verificada a quantidade de lipídio presente na biomassa. A microalga Tetraselmis sp. apresentou um crescimento notório no cultivo fotoautotrófico com remoções eficientes dos parâmetros e 5,0% de lipídio no peso seco. / Liquid effluents from tanneries present high organic and pollutant loads and must be treated correctly to meet the legal standards for effluent disposal and to avoid eutrophication of water bodies and water pollution. The leather finish is the final stage of production, where the leather receives the desired characteristics according to leather goods and articles. The effluents from the processing steps for leather finishing are responsible for containing chemical pollutants due to the use of dyes, surfactants, toxic metals, emulsifying agents, retanning agents, oils, pigments, resins, among other chemicals added. Microalgae have been the subject of several studies in the field of effluent treatment due to their ability to remove various nutrients, organic matter from the environment and to be cleaner and more economical ways to treat pollutants. In this work, the growth of a microalgae consortium for the treatment of effluents from a tannery was analyzed and the capacity of removal of Total Nitrogen (NT), Ammonia (NH3), Phosphorus (P-PO4), Total Carbon ), Total Organic Carbon (COD), COD and Biological Oxygen Demand (DBO), as well as the growth of microalgae biomass in these effluents. The effluents were characterized before and after the trials with the microalgae consortium. Effluents were collected in three distinct stages at a treatment plant: crude effluent (B), effluent after primary coagulation / flocculation (P) treatment and effluent after secondary biological treatment (S). The results with 50% effluent concentration, diluted in distilled water (A) after 16 days of cultivation, showed that there was a consortium growth in the three effluents with a maximum growth of 1.77 g L-1 in the crude effluent (50P50A). (50B50S) and 25% crude effluent + 75% effluent after biological treatment (25B75S) were tested in the following proportions: 50% crude effluent + 50% effluent after biological treatment (50B50S). It was not possible to cultivate the consortium in pure crude effluent, since it presented low growth and, consequently, low levels of nutrient removal. With the compound effluent 25B75S it was observed rapid death of the microalgae, since the effluent presented low concentrations of nutrients. On the other hand, in the effluent 50B50S, effective values of growth and nutrient removal were achieved. In photoautotrophic, mixotrophic and heterotrophic cultures of 50B50S effluent and 75% crude effluent + 25% effluent after biological treatment (75B25S), the best results were reached in the effluent 75B25S in photoautotrophic cultivation, growing up to 1.42 g L-1 and reaching values of removal of N-NH3, total nitrogen (NT), (DQO), total organic carbon (COT) and biological oxygen demand (DBO), of 99.90%, 74.89%, 56.70%, 58.18% and 20.68%, respectively. By obtaining the isolated microalgae Tetraselmis sp., predominant in the consortium and analyzed and the previous parameters in photoautotrophic cultivation, in addition to being verified the amount of lipid present in the biomass. The microalgae Tetraselmis sp. showed a notable growth in photoautotrophic cultivation with efficient removal of the parameters and 5.0% of lipid in dry weight.

A vinhaça é o resíduo mais abundante gerado no processo de produção de etanol, sendo que a cada litro de etanol são gerados de 10 a 18 litros de vinhaça. Sua disposição é tema de grande preocupação, por sua elevada carga de matéria orgânica e o pH ácido. Embora seja um resíduo poluente, contém macronutrientes que podem ser usados para o cultivo de micro-organismos úteis aos seres humanos como é o caso apresentado neste trabalho, onde a vinhaça foi utilizada para cultivo da microalga Scenedesmus sp. As microalgas são apontadas como uma alternativa promissora para substituição dos combustíveis fósseis. Entretanto, seu custo ainda é elevado devido a vários fatores, dentre os quais os nutrientes que devem ser fornecidos para crescimento. Assim, o uso de rejeitos como fonte de nutrientes pode auxiliar a reduzir este balanço desfavorável. Este trabalho teve como objetivo avaliar a viabilidade técnica de produção da Scenedesmus sp. para tratar vinhaça de etanol de cana de açúcar. Inicialmente, testou-se a viabilidade de crescimento da microalga nesses meios. Uma vez corroborado que é possível seu crescimento, foram realizados planejamentos experimentais que avaliaram os fatores que influenciam no crescimento. O planejamento fatorial demonstrou que é possível cultivar microalgas em concentrações de até 40% de vinhaça. O planejamento composto central rotacional demonstrou o seguinte: a intensidade luminosa e a porcentagem de vinhaça influenciam na quantidade de biomassa a ser produzida, e a temperatura, entre 20 e 35°C, não tem um efeito significativo quando se trabalha com porcentagens menores que 40% de vinhaça. Foram analisados parâmetros como o DBO, conteúdo de nitrogênio e fósforo, que demonstraram que fotobiorreatores com até 32% geram vinhaça tratada com valores de DBO menores que 106 mg/L, conseguindo remover até 96% de nitrogênio e 99,9% de fósforo. Como dado adicional se avaliou os métodos de espectrofotometria e espectroscopia de fluorescência, que se mostraram métodos adequados para acompanhar o crescimento microalgal em fotobiorreatores. / Vinasse is one of the most polluting wastes generated in the process of ethanol production,with each liter of ethanol are generated between 10 to 18 liters os vinasse. Its suitable disposal is an issue of great concern due to its high load of organic matter and acidity. Although this is a polluting waste, contains nutrients which can be used for cultivation of micro-organisms that may be useful to humans as is the case presented in this work, where vinasse was used for cultivation of the microalgae Scenedesmus sp. Microalgae are currently reported in the literature as a promising alternative to replace fossil fuels. However, its cost is still high due to several factors, such as the nutrients that must be supplied for growth. Thus, the use of waste as a source of nutrients may assist in reducing this unfavorable balance. This study aimed to evaluate the technical feasibility of production of microalgae Scenedesmus sp. to treat ethanol stillage. First, cultivations with different percentages of vinasse were done aiming to verify wether they are able to grow in medium supplemented with vinasse. The factorial design has shown that it is possible to cultivate microalgae at concentrations up to 40% of vinasse in the culture medium. The central composite design showed that light intensity and percentage of vinasse influence the amount of biomass to be produced. Additionally, the temperature between 20 and 35°C has not a significant effect when working with percentages smaller than 40% of vinasse. The analyzed parameters were BOD, nitrogen and phosphorus content demonstrated that photobioreactors with up to 32% vinasse generate vinasse treated with BOD values lower than 106 mg/L achieving a remotion of 96% nitrogen and 99.9% phosphorus. Finally, it was also shown that spectrophotometry and 2D fluorescence spectroscopy are suitable methods for monitoring the microalgae growth.