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Utilization of Chlorella vulgaris for biomass production and treatment of wastewater from greenhouse farms
In the current research work, green microalgae C. vulgaris was used for treating hydroponic and aquaponic wastewater collected from the Center for Applied Research on the Environment and Sustainability (CARES) at The American University in Cairo (New Cairo, Egypt) and for producing biomass. The pres...
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AUC Knowledge Fountain
2020
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| Summary: | In the current research work, green microalgae C. vulgaris was used for treating hydroponic and aquaponic wastewater collected from the Center for Applied Research on the Environment and Sustainability (CARES) at The American University in Cairo (New Cairo, Egypt) and for producing biomass. The present study was undertaken to evaluate the use of microalgae for bioremediating wastewater from greenhouse farm and for producing biomass under different conditions and to explore the economic implications of microalgal biofuels, focusing on the effect of different cultivation modes. Various experiments were carried out into four phases to assess the effect of different conditions into the nutrient removal and biomass production of C. vulgaris. It was observed that the cultivation of C. vulgaris under mixotrophic mode was found to be more beneficial in the bioremediation of hydroponic and aquaponic wastewater and in the production of biomass than heterotrophic and autotrophic modes of cultivation. The effect of different nitrogen to phosphorous molar ratios into nutrient removal and biomass production has also been assessed. Techno-economic assessment of microalgal biofuels has also been conducted, with a focus on the effect of different cultivation modes. The best results in terms of total nitrogen and total phosphorous treatment efficiency were reported for mixotrophic growth supplied with 2.5 g/l glucose and atmospheric CO2, showing reasonable removals of total nitrogen (TN) (98.5%), total phosphorus (TP) (99.99%) for hydroponic wastewater sample, and TN (98.5%), TP (99.9%) for aquaponic wastewater sample. The maximum biomass production and productivity were reported also for mixotrophic conditions in both hydroponic and aquaponic wastewater, showing a reasonable amount of biomass concentration (1.26 g/l) and biomass productivity (0.1108 g/l/d) for hydroponic wastewater, and biomass concentration and biomass productivity of 0.99 g/l, 0.089 g/l/d for aquaponic wastewater. Furthermore, the best results in terms of lipid content values were obtained under heterotrophic growth: 37 wt% on an Ash-free dry weight (AFDW) basis in aquaponic wastewater sample and a 33 wt% on an AFDW basis in hydroponic wastewater sample. On the other hand, the highest lipid production was obtained under mixotrophic growth (0.374 g/l) growth, followed by heterotrophic mode (0.341 g/l) in hydroponic wastewater sample. The best treatment efficiency were reported for N:P molar ratio of 8:1, displaying removals of TP (88%) and TN (85%) compared with that for N:P ratios of 16:1 and 24:1. Maximum values with respect to biomass production was reported for N:P molar ratio of 8:1 while biomass productivity was almost the same in all N:P molar ratios. Moreover, the best results regarding the net profit were obtained for both mixotrophic and heterotrophic cultivations of 26.4 MMUS$/y (2016 US$) and 26.1 MMUS$/y (2016 US$) respectively, while the net profit for autotrophic cultivation was 4.12 MMUS$/y (2016 US$). Sensitivity analysis shows that biodiesel and nutritious supplements from soluble protein have the greatest impact on the process economics with respect to mixotrophic cultivation while biodiesel and feeds from insoluble protein have the largest effect on the process economics in connection to both heterotrophic and autotrophic cultivations. |
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