Microalgae chromatographic profile without
This chapter aims to evaluate the microalgae species’ removal efficiency, using Moringa oleifera powder seeds as a natural coagulant with subsequent lipid profile characterization. For the tests were used deionized water artificially contaminated with cell cultures of Anabaena flos-aquae and Chlorella vulgaris, with a cell density in the order of 104 and 106 cells mL–1, respectively. Coagulation/flocculation/dissolved air flotation (C/F/DAF) tests were conducted using ‘Flotest’ equipment, using M. oleifera powder seeds in the dosage range of 50–1000 mg L−1. For fatty acid profile analyses, a gas chromatograph equipped with a flame ionization detector was used. Variations of the coagulant dosages showed that there was a difference between dosages and that 100 mg L–1 provided the best removal efficiency for A. flos-aquae (96.5, 80.5 and 78.1%) and 140 mg L−1 for C. vulgaris (90.5, 78.34 and 70%) of the tested parameters of chlorophyll, color and turbidity, respectively. In relation to the produced sludge, it was observed that the use of this coagulant in the treatment of water contaminated with microalgae produces a biodegradable sludge, rich in lipids, especially oleic acid (>60%). Thus, these results indicate that the sludge’s reutilization could be a good alternative to biodiesel production, as it represents an environmentally viable method for reusing residual biomass produced in the water treatment process.
- reusing lipids
- water treatment processes
Several natural coagulants have been studied for water purification; recently,
The dissolved air flotation has been considered a viable alternative to the sedimentation step when applied to water treatment in the microalgae’s presence, since this process is capable of removing whole cells, besides decreasing the time contact between the generated sludge with water treatment. The waste generated removal is performed by mechanical equipment, which is installed in water and has an easy maintenance [5, 6].
The proper disposal of the generated sludge by water treatment plants (WTPs) is essential, according to NBR 10004 , is considered a solid residue, which if released without proper treatment in waterways, can cause direct effects in the aquatic environment, damaging receiving fauna and flora. The nonchalance towards the waste generated, causes impacts, such as increase in the amount of solids in water body, water body siltation, increased of color, turbidity and aluminum concentration in the water, decrease of the water’s pH, releasing of odors, decreases the amount of dissolved oxygen in the water body and chronic toxicity on aquatic organisms and their vision.
However, this chapter seeking environmentally viable alternatives to microalgae biomass reuse present in the generated sludge by water treatment plants, for example, to characterize the lipid content produced by these microalgae, to consign them to a further biodiesel production.
Thus, this chapter shows the removal of
Phylogenetically, microalgae are prokaryotes or eukaryotes organisms, according to the period when they appeared on the planet, belonging to a very heterogeneous group of microorganisms. According to Andrade et al.  the microalgae are photosynthetic microorganisms that combining water and atmospheric carbon dioxide with sunlight to produce biomass (polysaccharides, proteins, lipids and hydrocarbons). Which can be used in biofuel production, feeding supplements and also can be used in atmospheric carbon dioxide capture. Microalgae produce more oxygen than all plants in the world, accounting for at least 60% of the Earth’s primary production.
The microalgae biomass presents about 50% carbon in its composition, so the supply of this nutrient to these microorganisms’ cultures represents an important component of the production costs . However, it is necessary to take care of microalgae culture systems, considering the peculiarities of each species, adaptation to the environment, as well as the availability of nutrients associated with economic viability .
The exact number of microalgae species is not yet known, but many species may already grow in cropping systems. The most difficult task, however, is to grow specific species for oil production .
Some microalgae species under adverse environmental conditions, such as nutrient stress (lack of nitrogen or phosphorus), may accumulate lipids. The green algae specie,
2.1. Microalgae lipid content
The microalgae biomass contains three main components: carbohydrates, proteins and lipids . In biological systems, the lipids function as membrane components, reserve products, metabolites and as energy sources, with most of them consists of fatty acids. Thus, the lipids are classified in storage lipids (neutral lipids), triacylglycerols and membrane lipids (polar lipids), phospholipids, glycolipids and sterols .
Fatty acids are fundamental units most of the lipids. They are short-chain and long-chain organic acids having 4–24 carbon atoms, and short-chain fatty acids are ideal for the biodiesel production .
Some fatty acids synthesized by microalgae, such as omega 3 and 6 (ω-3 and ω-6), which are the main precursors of some hormones such as prostaglandins, prostacyclins, leukotrienes and thromboxanes, have a high economic value in the food and pharmaceutical industry and are fundamental for the development and physiological regulators .
Fatty acids in microalgae correspond to the largest lipid fraction, and, in some species, polyunsaturates represent between 25 and 60% of total lipids .
The polyunsaturated fatty acids from microalgae have a very promising market in biotechnology, especially in the functional food industry . Studies presented by Favaro-Trindade et al.(2008)  show that lipids, especially unsaturated fatty acids, have been encapsulated to reduce susceptibility to oxidation.
According to Nelson e Cox , fatty acids have a unique carboxyl group and a non-polar hydrocarbon tail, which give lipids their oily and fatty nature, insoluble in water. They occur in cells or tissues in forms covalently attached to different lipids’ classes. Different fatty acids have been isolated from lipids of various species.
They differ by the chain extension and its presence, number and double bonds position, and some fatty acids also have methyl-branched groups.
The glycolipids that are composed of glycerol have been found in many organisms, being observed as the main lipid component of microalgae photosynthetic membranes, including cyanobacteria (blue microalgae). Its structure is analogous to that of glycerophospholipids with a sugar molecule, glycosidically attached to glycerol three position and fatty acids esterified in the other two positions.
Among the main glycosylacylglycerols of microalgae and plant photosynthetic membranes is monogalactosyl-diacylglycerol (MGDG), which occurs abundantly in plants and algae, especially in chloroplasts. Contains high proportions of polyunsaturated fatty acids. For
The lipid production estimation by microalgae ranges from 15,000 to 30,000 L.km2, and its extraction is simple and can be applied to traditional methods used in the chemical industry, including solvent extraction .
It is known that among the nutrients that can influence the lipids and fatty acids production are the sources of nitrogen and sulfur, which are used by microalgae in the synthesis of amino acids and fatty acids .
The main applications of fatty acids microalgae occur in the enrichment of fish feed, biodiesel production and sources of essential unsaturated fatty acids in the human diet .
Although there are many microorganism types capable to accumulating lipids, not all of them have favorable characteristics for the application in the biodiesel production. The microalgae stand out because they present, in some cases, compatibility in the ratio of their oil produced to the vegetable oil used in the transesterification process [22, 23].
According to Schimitz et al. , the presence of polyunsaturated compounds produced by microalgae causes a decrease in the stability of produced biodiesel. However, due to the presence of these fatty acids, biodiesel from microalgae presents a high yield at low temperatures, a characteristic that is not presented by conventional oilseed biodiesel, which have little yield at relatively low temperatures.
According to Ndabigengesere and Narasiah e Talbot ,
2.3. Removal of microalgae from water using
Moringa oleifera, as natural coagulant
Coagulation/flocculation (C/F) followed by dissolved air flotation (DAF) is suitable for the treatment of naturals and synthetic eutrophic waters [5, 32]. When it comes to the removal of cyanobacterial cells, DAF is an effective alternative, as shown by some studies in the literature [5, 6]. However, to achieve good efficiency, water treatment plants (WTPs) use a series of auxiliary products in the process, especially the use of inorganic coagulants, usually based on metals such as aluminum, as well as pH control. However, these coagulants do not generate biodegradable sludge, causing problems in terms of disposal and treatment; this may be also related to some diseases, such as Alzheimer’s disease, due to residual aluminum in treated water [33, 34]. Thus, the search becomes necessary for alternative natural coagulants that are biodegradable and safe to human health .
The water treatment processes in WTPs produce residues, mostly water used for washing the filters and sludge from sedimentation tanks/floaters . Particularly, in WTPs with cyanobacteria problems, the sludge generated is composed of microalgae biomass. Knowing that such biomass has a relatively high amount of lipids in their composition , which could be used for biodiesel production.
Firstly, by evaluating the results obtained (Figure 1), one can observe the percentages of the removal of the parameters color, turbidity and chlorophyll-a and compounds with absorption in UV254 nm, indicating the optimum dosage of the
The results indicate that the
Regarding the removal of UV254 nm, it was observed that
Thus, it was observed that the C/F/DAF processes used together with
In relation to the microalgae lipid profile analysis, the fatty acids and esters microalgae were first identified without the
It can be verified that the saturated fatty acids corresponded to 40.4% composition of
Among the acids with the highest values in
|% Fatty acids means present in microalgae without treatment|
Embora haja poucos trabalhos relatando o perfil lipídico de
Although there are few studies reporting the
After treatment with the
|% Fatty acids means presented in microalgae with MO treatment|
This increase is probably related to the residual
The acid responsible for this increase was C18:1n9 (oleic acid), presenting 69.5% in the
According to Qu et al. , oils with high oleic acid values (>70%) improve the biodiesel properties, such as cold flow, cloud point and pour point, in this way, the sludge produced after treatment with the