Abstract
The application of algae-based technology for wastewater treatment and metabolites extraction relies on algal biomass yield. This study investigated the effect of steel slag supplement as a Ca2+ source on growth of green algae Chlorella sp. The improvement was dose-dependent. Small dose improved microalgae growth, while high dose exhibited negative effect on growth, chlorophyll a and oxygen evolution. The optimal dose of 0.75 g/L steel slag with leaching Ca2+ of 25 mg/L achieved maximum dry weight of microalgae, which was 1.4 times higher than the control. Dissolved oxygen was proposed to monitor growth, as it changed prior to Chl-a/Chl-b and Caro/Chl. Correlation analysis revealed that growth enhancement was due to combined effect of Ca2+, pH and HCO3-. Furthermore, microalgae accelerated Ca2+ leaching from steel slag. Heavy metals were below the limit of wastewater treatment effluent criteria. Nutrients removal ability of microalgae harvested from steel slag was improved. The investigation verified that CaO in steel slag was feasible to trigger microalgae growth, which attained recycling economy and environmental sustainability.
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