Water Science and Technology (Jun 2022)

Using chlorella vulgaris for nutrient removal from hydroponic wastewater: experimental investigation and economic assessment

  • Y. I. D. Yousif,
  • Essam Sh. Mohamed,
  • A. S. El-Gendy

DOI
https://doi.org/10.2166/wst.2022.157
Journal volume & issue
Vol. 85, no. 11
pp. 3240 – 3258

Abstract

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The study evaluated the use of Chlorella vulgaris for bioremediating hydroponic wastewater and producing biomass under different cultivation modes and to explore the economic implications of microalgal biofuels. Total nitrogen (TN) removal efficiency was 98.5% in mixotrophic conditions and 96% in heterotrophic conditions, and total phosphorus (TP) was completely removed (>99%) in both cultivation conditions. TN removal was higher for that which was cultivated under the mixotrophic mode of cultivation. The maximum biomass production (1.26 g/L) and biomass productivity (0.1108 g/L/day) were also reported for mixotrophic conditions. Lipid content was slightly higher for that which was cultivated under heterotrophic conditions: 33 wt% on an ash-free dry weight (AFDW) basis. The highest lipid production was obtained under mixotrophic growth (0.341 g/L). Higher net profit was obtained for both mixotrophic and heterotrophic cultivations: 30.6 million $/year for a plant capacity of 3.29 × 104 tone/year and 30.12 million $/year for a plant capacity of 3.17 × 104 tone/year respectively. Sensitivity analysis showed that biodiesel and nutritious supplements from soluble protein have the greatest impact on the process economics regarding mixotrophic cultivation, while biodiesel and feeds from insoluble protein have the largest effect on the process economics regarding heterotrophic and autotrophic cultivations. HIGHLIGHTS C. vulgaris was cultivated in hydroponic wastewater to remove nutrients and to produce lipid and biomass.; C. vulgaris showed higher TN removal efficiency under mixotrophic growth (TN: 98.5%).; Maximum lipid content was reported for heterotrophic growth (33 wt% AFDW).; Mixotrophic cultivation showed maximum biomass production (1.26 g/L) and biomass productivity (0.1108 g/L/day).; The best economic benefits were obtained for mixotrophic (net profit: 30.6 million $/year) and heterotrophic (net profit: 30.12 million $/year) cultivations.;

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