Hydrogel immobilized microalgae-alginate beads to model the fermentation of phenol-containing wastewater into biohydrogen molecules

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The potential of hydrogel immobilized microalgae-alginate beads to concurrently remove phenol and produce biohydrogen molecules from phenol-containing wastewaters with different phenol concentrations of 0.2 g/L to 1.2 g/L via dark fermentation had been successfully modelled and proven. Highest biohydrogen production and phenol removal were achieved at phenol concentration of 1.2 g/L. The lag phase of biohydrogen production increased with increasing of phenol concentration as the microalgal cells entailed a longer time to acclimatize in inhibitory medium of high phenol strength. The extended period for fermentation could also generate more biohydrogen molecules as compared with batch setup that was easily inhibited due to inadequate acclimatization allocation. Then, a new kinetic model was rederived from the modified Gompertz model and Andrew’s inhibition model to describe the relationship between phenol concentration impacting the microalgal growth and subsequent biohydrogen production. Low concentration of phenol could serve as an alternative source of carbon to promote the microalgal growth and development; but high phenol concentration could hinder the growth of microalgae, afflicting the fermentative biohydrogen production. The rederived kinetic model was able to fit the experimental data for all phenol concentrations with coefficients of determination of greater than 0.95. This study had ultimately evidenced that the immobilized microalgae were able to ferment phenol and produce biohydrogen molecules simultaneously from phenol-containing wastewater.