Capability of different microalgae species for phytoremediation processes: Wastewater tertiary treatment, CO2 bio-fixation and low cost biofuels production.

Scenedesmus obliquus, Chlorella vulgaris, Chlorella kessleri and a natural Bloom were cultivated in batch experiments, under controlled conditions, in urban wastewater (WW) and synthetic wastewater (SW) under 5% CO2 in air, with the object of estimating their capacity for nutrient removal, carbon dioxide biofixation, and generation of valuable biomass. In both culture media, the Bloom (Bl) and Scenedesmus (Sc) showed higher final biomass concentration (dried weight, dw) than the other species; the maximum yield obtained was 1950 ± 243 mg L−1 for Bl and the minimum 821 ± 88 mg L−1 for Cv, both in synthetic wastewater. Maximum specific growth rate values do not show significant differences between any of the 4 strains tested (p ≤ 0.05), nor between the 2 culture media. A new homogeneous method of calculating productivities has been proposed. Nitrogen removal in all the reactors was higher than 90%, except for BlSW (79%), and for phosphorus, the removal was higher than 98% in all trials. Maximum CO2 consumption rates reached were 424.4 and 436.7 mg L−1 d−1 for ScSW and ScWW respectively

Photobiotreatment model (PHBT): a kinetic model for microalgae biomass growth and nutrient removal in wastewater.

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

Photobiotreatment: influence of nitrogen and phosphorus ratio in wastewater on growth kinetics of Scenedesmus obliquus.

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)

Chlorella stigmatophora for urban wastewater nutrient removal and CO2 abatement.

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 ΣN·L−1 (T10( N)) and 1 mg ΣP·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

Lipid Production of Microalga Ankistrodesmus falcatus Increased by Nutrient and Light Starvation in a Two-Stage Cultivation Process.

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

Effect of nitrogen and phosphorus concentration on their removal kinetic in treated urban wastewater by Chlorella vulgaris.

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-PO3− 4), ammonium (5.8–226.8 mg · L−1 N–NH+ 4) and nitrate (1.5– 198.3 mg · L−1 N–NO− 3) 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

Effect of ph control by means of flue gas addition on three different photo-bioreactors treating urban wastewater in long-term operation.

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

Wastewater treatment and biodiesel production by Scenedesmus obliquus in a two-stage cultivation process.

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 ω-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 ω-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 ω-3 fatty acids from S. obliquus oil

Huella ecológica energética corporativa: un indicador de la sostenibilidad empresarial

La Huella Ecológica es un concepto reciente que se viene utilizando como indicador de la sostenibilidad ambiental. Existen diversos ejemplos en su aplicación a empresas como la Huella Ecológica Corporativa. En este artículo, se propone una metodología de cálculo de la Huella Ecológica Energética (HEE) de las empresas. La HEE es calculada en términos de gases de efecto invernadero a partir de análisis de ciclo de vida de las tecnologías de producción de electricidad y análisis de la fuente al depósito (Well-to-Tank) de los combustibles. Se ha analizado la HEE del puerto de Gijón (El Musel), los resultados obtenidos indican que la reducción más significativa de HEE (93,18%) se puede alcanzar mediante la selección de tecnologías basadas en energías renovables dentro de la gestión de los recursos energéticos. Se puede considerar la Huella Ecológica Corporativa como una importante herramienta en la gestión ambiental de las empresas