Leveraging iron-rich recovered waste as a co-electron donor in sulfur autotrophic denitrification for simultaneous nitrate and phosphate removal from low C/N hydroponic wastewater

초록

An iron-rich waste derived from acid mine drainage (AMD) sludge was repurposed as a co-electron donor in elemental sulfur (S-0) autotrophic denitrification, forming a combined sulfur-iron system termed SADNIP (sulfur autotrophic denitrification with iron processes). Three up-flow packed bed columns were operated with varying S-0 to iron-waste ratios (100:0, 75:25, and 50:50) over 60 days to evaluate nitrate (NO3--N) and phosphate (PO43--P) removal from hydroponic wastewater under different empty bed contact times (EBCTs). The mixed S-0-iron waste media dramatically improved denitrification: at an EBCT of 6 h, the 50:50 (S-0:waste) column achieved nearly 97 % NO3--N removal, far outperforming the sulfur-only column (29 % removal). Even at a short 4 h EBCT, the 50:50 column maintained nearly 75 % nitrate removal with minimal nitrite accumulation. Phosphate removal was enhanced by the iron waste addition - the 50:50 column consistently removed 80-90 % PO43--P during early phases, versus <25 % in the sulfur-only system. High-throughput 16S rRNA gene sequencing revealed that the sulfur-iron system enriched sulfur-oxidizing denitrifiers (e.g. Thiobacillus and Acidihalobacter) while sulfur only column contained primarily heterotrophic non denitrifying bacterial population with Neobacillus acting as a major denitrifying bacterium.

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