Industrial Wastewater as a Growth Medium for Microalgal Biomass for a Sustainable Circular Bioeconomy

Abstract

Since sources of clean water are limited, industrial wastewaters are available and utilization of biomass as a renewable energy source is increasing; therefore, wastewater could be used as a growth medium for the production of biomass. Such an approach is directly connected to the sustainable circular bioeconomy. The main aim of the present study was to evaluate the potential application of industrial wastewater for cultivation of C. vulgaris and S. armatus. This study was carried out in order to: (i) assess the influence of wastewater on the activity of microalgae; (ii) assess batch and repeated fed-batch culture cultivation techniques; and (iii) assess cultivation of microalgae in suspension and immobilized on alginate beads. It was demonstrated that microalgae can be cultivated in wastewater contaminated with inorganic and organic chemical compounds in autotrophic conditions, batch culture or repeated fed-batch culture, and also in the form of suspension as well as being immobilized on alginate beads. The growth rate of microalgae in samples with initial algal culture concentrations of 100 g/L was as follow: 2.3 ± 0.01 d−1–3.8 ± 0.03 d−1 for C. vulgaris and 2.2 ± 0.02 d−1–4.0 ± 0.06 d−1 for S. armatus. In samples with initial algal culture concentrations of 50 g/L the growth rate of microalgae (μ) was as follow: 1.2 ± 0.01 d−1–2.2 ± 0.02 d−1 for C. vulgaris and 1.3 ± 0.02 d−1–2.4 ± 0.05 d−1 for S. armatus. Cultivation of microalgae in industrial wastewater has more advantages than cultivation carried out in clean water due to lower costs and protection of natural resources.