[learn_more caption=”12. Álvarez-Díaz, P., Ruiz, J., Arbib, Z., Barragan, J., Garrido-Pérez, M.C., Perales, J.A. (2015). Wastewater treatment and biodiesel production by Scenedesmus obliquus in a two-stage cultivation process. Bioresource Technology, 181, pp 90-96″]
Abstract
The microalga Scenedesmus obliquus was cultured in two cultivation stages: (1) in batch with real wastewater; (2) maintaining the stationary phase with different conditions of CO2, light and salinity according to a factorial design in order to improve the lipid content. The presence of the three factors increased lipid content from 35.8% to 49% at the end of the second stage; CO2 presence presented the highest direct effect increasing lipid content followed by light presence and salt presence. The x-3 fatty acids content increased with CO2 and light presence acting in isolation, nevertheless, when both factors acted together the interaction effect was negative. The x-3 eicosapentaenoic acid content of the oil from S. obliquus slightly exceeded the 1% maximum to be used as biodiesel source (EU normative). Therefore, it is suggested the blend with other oils or the selective extraction of the x-3 fatty acids from S. obliquus oil. [/learn_more]
[learn_more caption=”11. Álvarez-Díaz, P., Ruiz, J., Arbib, Z., Garrido-Pérez, M.C., Barragan, J., Perales, J.A. (2014). Lipid Production of Microalga Ankistrodesmus falcatus Increased by Nutrient and Light Starvation in a Two-Stage Cultivation Process. Applied Biochemistry and Biotechnology, 174(4), pp 1471-1483″]
Abstract
The aim of this work was to study the stimulation of lipid production on the microalga Ankistrodesmus falcatus by varying cultivation conditions during the stationary phase. The effect of three factors (presence and absence of nitrogen, phosphorus, and light) has been tested once the cultures reached the stationary phase with the aim to increase the value of the biomass for further applications. Lipid content, elemental composition, Nile red fluorescence evolution, and calorific value of microalgal biomass were studied as well as biomass growth. Biomass presented a lipid content of 36.54 % at the end of the first stage, while at the end of the second stage, the experiments with the absence of phosphorus increased their lipid content until 45.94 and 44.55 %, the first with nitrogen and light presence and the second with absence of all factors. The combination of phosphorus absence and nitrogen and light presence achieved the highest lipid productivity (20.27 mg/L/day). The two-stage strategy to culture microalgae is a feasible option to increase the economic or energetic value of biomass. [/learn_more]
[learn_more caption=”10. Ruiz, J., Arbib, Z., Álvarez-Díaz, P., Garrido-Pérez, M.C., Barragan, J., Perales, J.A. (2013). Photobiotreatment model (PhBT): a kinetic model for microalgae biomass growth and nutrient removal in wastewater. Environmental Technology, 34(8), pp 979-91″]
Abstract
This article proposes a kinetic model for wastewater photobiotreatment with microalgae (the PhBT model). The PhBT model for nutrient uptake, coupled with the Verhulst growth model, is a simple and useful tool to describe batch experiments of nutrient removal by microalgae. The model has been validated with experiments of Chlorella vulgaris (C. vulgaris) grown in wastewater and different synthetic media. The model provided information about nitrogen and phosphorus limitation and their luxury uptake during the test. Productivity observed in synthetic medium (0.17 g SS L−1 d−1) was similar to that obtained in nutrient enriched wastewater (0.15 g SS L−1 d−1). Biomass productivity of this alga in wastewater and the efficient nutrient removal suggested that C. vulgaris could be cultured in wastewater for biomass production while nutrients are reduced from this stream. [/learn_more]
[learn_more caption=”9. Ruiz, J., Arbib, Z., Álvarez-Díaz, P., Garrido-Pérez, M.C., Barragan, J., Perales, J.A. (2013). Performance of a flat panel reactor in the continuous culture of microalgae in urban wastewater: Prediction from a batch experiment. Bioresource Technology, 127, pp 456-463″]
Abstract
A laboratory-scale flat panel photobioreactor was operated for the continuous growth of Scenedesmus obliquus and consequent removal of nutrients in wastewater. This study develops a simple model by which biomass values in continuous operation can be predicted from kinetic growth parameters obtained from a shorter batch experiment. Based on this study, biomass concentrations and productivities in continuous operation can be successfully predicted as a function of the specific hydraulic retention time (HRT) assumed. Considerable biomass production and nutrient uptake from wastewater were achieved in the experiment. Optimum operating conditions for the reactor depend on the particular objective: the maximization of biomass production and carbon dioxide biofixation involves a HRT of 2 µ-1 (specific growth rate), whereas efficient nutrient removal involves a HRT as close as possible to µ-1 (as long as discharges comply fully with the parameters set); alternatively biomass intended for biodiesel or biogas production would involve a HRT > 2 µ-1. [/learn_more]
[learn_more caption=”8. Arbib, Z., Ruiz, J., Álvarez-Díaz, P., Garrido-Pérez, M.C., Barragan, J., Perales, J.A. (2013). Long term outdoor operation of a tubular airlift pilot photobioreactor and a high rate algal pond as tertiary treatment of urban wastewater. Ecological Engineering, 52, pp 143– 153″]
Abstract
530 L high rate alga pond (HRAP) and 380 L airlift tubular photobioreactor (TPBR) were operated and compared in a urban wastewater treatment plant (WWTP), with the main purpose of removing nitrogen and phosphorous from the effluent of the WWTP while generating a valuable biomass. The photosynthetic activity in TPBR was during entire experiment higher than HRAP. The maximum areal productivity reached was 8.26 ± 1.43 and 21.76 ± 0.3 g SS m−2 d−1 for HRAP and TPBR respectively. Total nitrogen (TN) removal averaged 89.68 ± 3.12 and 65.12 ± 2.87% for TPBR and HRAP respectively, while for total phosphorus (TP) TPBR and HRAP averaged 86.71 ± 0.61 and 58.78 ± 1.17% respectively. The lipid content showed no significant differences (p < 0.05) between HRAP and TPBR averaging 20.80 ± 0.22 wt%. The main operating disadvantage of TPBR versus HRAP was the sever biofouling which forced to stop the experiment. Under the same conditions of operation TPBR was more limited at low temperatures than HRAP, and HRAP was more light limited than TPBR.[/learn_more]
[learn_more caption=”7. Arbib, Z., Ruiz, J., Álvarez-Díaz, P., Garrido-Pérez, M.C., Barragan, J., Perales, J.A. (2013). Photobiotreatment: influence of nitrogen and phosphorus ratio in wastewater on Growth kinetics of Scenedesmus Obliquus . International Journal of Phytoremediation, 15, pp 774–788.”] Abstract
Nitrogen and phosphorus concentration in the effluent of a wastewater treatment plant can vary significantly, which could affect the growth kinetic and chemical composition of microalgae when cultivated in this medium. The aim of this work was to study the rate of growth, nutrient removal and carbon dioxide biofixation as well as biomass composition of Scenedesmus obliquus (S. obliquus) when it is cultivated in wastewater at different nitrogen and phosphorus ratio, from 1:1 to 35:1. A more homogeneous method for calculating productivities in batch reactors was proposed. The proper N:P ratio for achieving optimum batch biomass productivity ranged between 9 and 13 (263 and 322 mg L−1 d−1 respectively). This was also the ratio range for achieving a total N and P removal. Above and below this range (9–13) the maximum biomass concentration changed, instead of the specific growth rate. The maximum carbon dioxide biofixation rate was achieved at N:P ratio between 13 and 22 (553 and 557 mg CO2 L−1 d−1 respectively). Lipid and crude protein content, both depend on the aging culture, reaching the maximum lipid content (34%) at the lowest N:P (1:1) and the maximum crude protein content (34.2%) at the highest N:P (35:1). [/learn_more]
[learn_more caption=”6. Arbib, Z., Ruiz, J., Álvarez-Díaz, P., Garrido-Pérez, M.C., Barragan, J., Perales, J.A. (2013). Effect of pH control by means of flue gas addition on three different photo-bioreactors treating urban wastewater in long-term operation. Ecological Engineering, 57, pp 226– 235″] Abstract
Effect of pH control with flue gas has been studied in two high rate algal ponds (HRAPs), one with a carbonation sump station (HRAP + S), and a tubular airlift photobioreactor (TPBR) treating urban wastewater. Flue gas, from 1600 MW combined cycle plant, addition (4–5% volume CO2) not only increased biomass productivity but also improved efficiency of total nitrogen removal (TNRE) and total phosphorus removal (TPRE). The differences between the HRAP and HRAP + S were significant at all the flue gas injection flow rates tested. HRAP + S reached maximum TNRE, TPRE and biomass productivity (92.15 ± 1.45%, 95.10 ± 0.84% and 19.77 ± 0.38 g m−2 d−1, respectively) at a flow rate of 15 L min−1, while the HRAP reached similar productivity levels at 20 L min−1. TPBR showed an initial lower carbon limitation than HRAP and HRAP + S, but nevertheless a strong inhibition was observed in TPBR at the end of the test. Flue gas addition promotes the production of biomass with less nitrogen reserves and consequently with higher lipid content because of the nutrient limitation stress. [/learn_more]
[learn_more caption=”5. Álvarez-Díaz, P., Ruiz, J., Arbib, Z., Garrido-Pérez, M.C., Barragan, J., Perales, J.A. (2013). Factorial analysis of the biokinetic growth parameters and CO2 fixation rate of Chlorella vulgaris and Botryococcus braunii in wastewater and synthetic médium. Desalination and Water Treatment. doi: 10.1080/19443994.2013.808590.”]
Abstract
Microalgae strains, Botryococcus braunii and Chlorella vulgaris were cultured in urban wastewater as monoalgal cultures and together in co-cultures; the same experiments were performed in synthetic growth medium to establish comparisons between both media. A fully crossed factorial design was used to design and carry out the experiment, resulting in 18 tests, and this procedure allowed the development of regression models that defined experimental factors and their interactions. Results indicated that both strains were able to grow in wastewater, but productivities in this medium were halved respective to those obtained in the synthetic medium. Specific growth rates presented higher values in wastewater than in synthetic medium. B. braunii was the most productive strain, but when both strains were grown together in co-cultures C. vulgaris dominated the reactor. The use of microalgae in wastewater treatment systems demonstrates to minimize anthropogenic environmental pollution load and to generate valuable biomass.
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[learn_more caption=”4. Cabanelas, I.T.D., Ruiz, J., Arbib, Z., Chinaila, F.A., Garrido-Pérez, M.C., Rogalla, F., Nascimento, I.A., Perales, J.A. (2013). Comparing the use of different domestic wastewaters for coupling microalgal production and nutrient removal. Bioresource Technology, 131, pp 429–436.”] Abstract
The streams from municipal wastewater treatment plants (WWTP) have been considered a valuable medium for mass cultivation of algal biomass. The aim of this work is to test and compare the performance of Chlorella vulgaris on several streams from five stages, from two different WWTP. The results showed biomass yields ranging from 39 to 195 mg dry-weight l_1 days_1. The best performance as biomass production was obtained with the centrate (effluent from drying the anaerobic sludge). After testing a wide range of N/P ratios with centrate, the highest productivity and growth rates were obtained with the original N/P ratio (2.0) of this stream. The highest removal rates were of 9.8 (N) and 3.0 (P) mg l_1 – days_1, in the centrate. Finally, this research also suggests that microalgal production seems to be a promising process when coupled to wastewater treatment. [/learn_more]
[learn_more caption=”3. Cabanelas, I.T.D., Arbib, Z., Chinalia, F.A., Oliveira, C., Perales, J.A., Almeida, P.F., Druzian, J.I., Nascimento, I.A. (2013). From waste to energy: Microalgae production in wastewater and glycerol. Applied Energy, 109, pp 283–290″] Abstract
The present work aimed to evaluate the auto/mixotrophic growth of microalgae using domestic wastewater (WW) amended with glycerol aiming biofuels production. The best results were obtained with the highest glycerol supplementation (50 mM). In such condition, Chlorella vulgaris and Botryococcus terribilis showed a biomass productivity of 118 and 282 mg L-1 d-1, which produced about 18 and 35 mg L-1d-1 of lipids, respectively. Thus, if scaled-up (200 m3 d-1of WW, 240 working days y-1) biomass and lipid yields may be about 5.6 tons y-1 and 894.2 kg y-1 or 13.5 tons y-1 and 1.6 tons y-1 for C. vulgaris and B. terribilis, respectively. The mixotrophic production of lipids can generate high quality biodiesel according to estimations using their fatty acids profiles. The whole process can be advantageously combined with the production of other biofuels (e.g. methane and bio-ethanol) in a biorefinery scenario. This combination of algal biomass production with waste treatment (WW amended with glycerol) can have a significant impact in the water treatment sector and local markets. [/learn_more]
[learn_more caption=”2. Arbib, Z., Ruiz, J., Álvarez-Díaz, P., Garrido-Pérez, M.C., Barragan, J., Perales, J.A. (2012). Chlorella Stigmatophora for urban wastewater nutrient removal and CO2 abatement. International Journal of Phytoremediation, 14, pp 714–725.”] Abstract
Batch experiments were performed to study biomass growth rate, nutrient removal and carbon dioxide bio-fixation of the marine microalgae Chlorella stigmatophora. Four different cultures at different salinities were tested: wastewater (WW), synthetic wastewater (SWW), seawater (SW) and diluted seawater (DSW). Experimental results showed that Chlorella stigmatophora grew satisfactorily in all culture media, except in SWW where inhibition occurred. In all cases, biomass experimental data were fitted to the Verlhust Logistic model (R2 > 0.982, p ≤ 0.05). Maximum biomass productivity (Pbmax) and CO2 biofixation (PvCO2) were reached in the WW medium, 1.146 g SS・L−1・day−1 and 2.324 g CO2・L−1・day−1 respectively. The order of maximum specific growth rates (μmax) was WW>DSW>SW. In order to compare nitrogen and phosphorous removal kinetics, an estimation of the time required to reach the most restrictive concentration of total N and P in effluents as defined in the Directive 98/1565/CE (10 mg N・L−1 (T10(N)) and 1 mg _P・L−1 (T1(P)) was performed. In the WW test T10(N) and T1(P) needed were of 45.15 and 32.27 hours respectively and at the end of the experimental the removal was in both 100%. [/learn_more]
[learn_more caption=”1. Ruiz, J., Arbib, Z., Álvarez-Díaz, P., Garrido-Pérez, M.C., Barragan, J., Perales, J.A. (2011). Effect of nitrogen and phosphorus concentration on their removal kinetic In treated urban wastewater by Chlorella Vulgaris. International Journal of Phytoremediation, 13, pp 884–896.”] Abstract
This study evaluates the feasibility of removing nutrients by the microalgae Chlorella vulgaris, using urban wastewater as culture medium, namely the effluent subjected to secondary biological treatment in a wastewater treatment plant (WWTP). For this, laboratory experiments were performed in batch cultures to study the effect of initial nitrogen and phosphorus concentrations on growth and reduction of nutrient performance of C. vulgaris. The microalga was cultivated in enriched wastewater containing different phosphorus (1.3– 143.5 mg · L−1 P-PO4− 3 ), ammonium (5.8–226.8 mg · L−1 N–NH4+) and nitrate (1.5– 198.3 mg · L−1 N–NO3- ) concentrations. The nutrient removal and growth kinetics have been studied: maximum productivity of 0.95 g SS · L−1 · day−1, minimum yield factor for cells on substrate (Y) of 11.51 g cells · g nitrogen−1 and 0.04 g cells · g phosphorus−1 were observed. The results suggested that C. vulgaris has a high potential to reduce nutrients in secondary WWTP effluents.[/learn_more]