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ABSTRACT
Worldwide threats of fuel shortages in the near future and climate change because of greenhouse gas emissions are posing severe challenges and therefore it is vital to search for sustainable ways of preventing the consequences. The dual use of microalgae for phycoremediation and biomass production for sustainable biofuel production is a viable choice. Phycoremediation of As(III) and As(V) ions using microalgae was investigated in a two-staged batch reactor. Accumulation and toxicity of inorganic arsenic forms (As(III) and As(V)) to green microalgae Botryococcus braunii depend on environmental factors. Dissolved oxygen and pH cycles did not significantly differ due to the absence or presence of arsenic (either As(III) or As(V)) ions in the culture. Monod model was utilized for representing the growth kinetics of microalgae in pure media containing various concentrations of nitrate ions. Maximum specific growth rate and saturation constant were found to be 0.14788 d−1 and 0.00105 g/L, respectively. With the increase in concentration of phosphate in growth medium, the growth of microalgae increased. Media with NaCl (1.0 g/L) and NaHCO3 (1 g/L) resulted in higher maximum biomass concentration. Effect of coexisting ions on phycoremediation of As(III) and As(V) ions using microalgae was studied.
Nomenclature
| C | = | total chlorophyll content (g/L) |
| Ca | = | chlorophyll a content (g/L) |
| Cb | = | chlorophyll b content (g/L) |
| CA | = | the limiting substrate concentration at time t (g/L) |
| C0 | = | initial concentration of arsenic in the solution (mg/L) |
| Ce | = | equilibrium concentration of arsenic in the solution (mg/L) |
| D663 | = | specific absorption coefficient at 663 nm |
| D645 | = | specific absorption coefficient at 645 nm |
| Ks | = | the substrate saturation constant (g/L) |
| μ | = | the specific growth rate (d−1) |
| μmax | = | the maximum specific growth rate (d−1) |
Acknowledgments
Our thanks to the Indian Institute of Technology, Roorkee for providing necessary facilities and to the Ministry of Human Resource Development, Government of India, for financial support. The thoughtful comments by Dr Ebbs, the editor-in-chief, and five anonymous reviewers are highly appreciated.