In situ purification of ammonium nitrogen wastewater in rare earth mine by native bacteria isolating from original mining area

Abstract

Ammonium sulfate ((NH₄)₂SO₄) leaching method to extract rare earth elements (REEs) of mine has produced a large amount of NH₄⁺-N-enriched wastewater derived from ore body, leading to many serious environmental pollution problems. This study was the first time to establish an in-situ treatment for real REEs wastewater outside and inside the ore body by an isolated indigenous microorganism. The results stated that Citrobacter sp. X-9 achieved the highest NH₄⁺-N removal efficiency among the isolated six microbial strains. Moreover, the microbe to treat the REEs wastewater outside ore body gave the greatest NH₄⁺-N removal efficiency under the optimized conditions in the Erlenmeyer flask (250-mL) and bioreactor (10-L). Furthermore, compared to the others’ modes, the in-situ treatment by cyclic mode with Citrobacter sp. X-9 possessed superior performance in NH₄⁺-N removal efficiency for wastewater inside of ore body, showing that the established in-situ treatment was the potential approach for REEs wastewater purification.