Remediation of Waste Sealing Mud from Moutai: Enhancing Organics and Nitrogen Removal Simultaneously via the Cycle of Indigenous Iron

Abstract

After a period of sealing the cellar for Maotai-flavor liquor brewing, the sealing mud can no longer be used due to the accumulation of organics and nitrogen. In this study, a method for restoring waste mud driven by the cycle of indigenous iron was proposed, in which Fe(II) was oxidized to Fe(OH)₃ after short-term aeration, and then dissimilatory Fe(OH)₃ reduction coupled with organics and ammonium oxidation (Feammox) occurred under anoxic conditions. The results showed that the aeration group achieved 60.0% organic matter removal and 53.6% nitrogen removal, which were significantly higher than those of the control group (p < 0.05). Microbial analysis showed that intermittent aeration enriched iron-reducing bacteria, removing ammonium via Feammox as well as microorganisms degrading organics, while ammonium-oxidizing bacteria and anaerobic ammonium oxidation (Anammox) microorganisms were undetected, ruling out the contribution of nitrification and Anammox to nitrogen removal. Metagenomic analysis further demonstrated that the genes related to the iron cycle, organic degradation, and nitrogen removal were significantly increased in the aeration group. After the treatment, the mud had no odor, and the viscosity was recovered, achieving a remediation effect. This method provides an economical and efficient solution for waste containing organics and nitrogen.