Rapid oxidative removal of Fe2+ and Mn2+ from acidic mining wastewater by a new-type biofilter system: application and mechanism

Aimed at the problem of excessive concentration of Fe2+ and Mn2+ in acidic mining wastewater during mining and utilization, a new rapid oxidative removal technology of Fe2+ and Mn2+ by a new-type biofilter system was designed and tested. The new-type biofilter system was constructed using a bioreactor filled with special mature bioceramic pellets after continuous biofilm cultivation as the filter layers. The results indicated that the biofilter system could efficiently treat five times its volume of wastewater per hour. The Fe2+ concentration of the influent wastewater was about 500 mg/L, and its Mn2+ concentration was about 20 mg/L. The average Fe2+ and Mn2+ removal rates could reach 99.7% and 90.8%, respectively. In addition, scanning electron microscopy and energy dispersive spectroscopy-energy dispersive spectroscopy and X-ray photoelectron spectroscopy were applied to analyze the migration distribution and valence change of Fe and Mn ions to clarify the removal mechanism of Fe2+ and Mn2+ using the biofilter system. The results showed that iron oxidation products were mainly coated at the surface of the mature bioceramic pellets and could be easily washed out from the filter layer with flowing water, while manganese oxidation products tended to accumulate between the pores of the mature bioceramic pellets. Furthermore, the final filtration products were multivalent complex oxides, indicating that the high-valent oxidation products could adsorb Fe and Mn ions, which were mainly removed by the oxidation effect.

Removal of iron and manganese in groundwater through magnetotactic bacteria

It is presented an alternative biological method based on biomineralization mechanisms of Magnetotactic Bacteria (MTB) for the removal in groundwater, of soluble elements such as Fe⁺²and Mn⁺². In first place, it was compared the effectiveness of MTB retention methods for obtention of concentrated volumes in microorganisms, then, it was carried out an inoculation process in groundwater samples and evaluate the removal rate of Fe⁺² and Mn⁺² in constant conditions of pH and temperature. It was identified electromagnetic method is more efficient in MTB retention, and that the inoculation processes of an enriched solution with MTB in groundwater samples allow to get average removal rates of 47.86% for Fe⁺² and 15.26% for Mn⁺². In addition, it was evaluated the removal rate of other metals due to magnetic properties of biominerals inside of MTB magnetosome. The highest removal in all cases occurred between the interval of 3 and 5 min of interaction and tended to stabilize in time.