A novel and efficient strategy mediated with calcium carbonate-rich sources to remove ammonium sulfate from rare earth wastewater by heterotrophic Chlorella species

Abstract

This work was the first time to establish the desired approach with two heterotrophic Chlorella species for ammonium sulfate (AS)-rich rare earth elements (REEs) wastewater treatment by heterotrophic cultivation. The results showed that these two Chlorella species treated by 6 g/L CaCO3 performed the best ability to remove NH4+-N and SO42- of REEs wastewater. Moreover, the established process performed similar features in REEs wastewater treatment by replacing CaCO3 with eggshell powder (ESP) and oyster shell powder (OSP) enriched in CaCO3. Furthermore, microalgae treated by ESP/OSP in a 10-L fermenter showed 837.39 mg/(L·d) NH4+-N and 1,820 mg/(L·d) SO42- removal rates. The developed kinetic models could be well fitted to the experimental data obtained by the 10-L fermenter. Taken together, the established process mediated with two Chlorella species and ESP/OSP by heterotrophic cultivation was the great potential for AS-rich REEs wastewater treatment in a cost-effective manner.