Simultaneous remediation of ciprofloxacin and nitrate threats in groundwater through manganese redox cycling: Performance optimization, mechanisms, and potential for community assembly

• Published in: Journal of water process engineering 2024-07, Vol.64, p.105629, Article 105629
• Main Authors: Liu, Yu, Ren, Yi, Su, Junfeng, Liu, Shuyu, Xu, Liang, Wang, Yue
• Format: Article
• Language: English
• Subjects: Ciprofloxacin; Denitrification; Low C/N ratio; Manganese oxides; Manganese redox cycle
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2024.105629

The misuse of fertilizers and antibiotics by the agriculture and livestock industries in recent years has led to groundwater bodies facing the problem of co-contamination by ciprofloxacin (CIP) and nitrate (NO3−-N). In this study, a manganese recycling system using manganese (Mn) redox-synchronized denitrification microorganisms loaded with manganese oxides was implemented to achieve simultaneous CIP and NO3−-N elimination. The reactor was operated for 195 days, during which the optimal operating conditions were determined by adjusting various parameters. The study also investigated the removal of CIP and its impact on the microbial community under these conditions. The experimental results showed that 77.4 and 92.5 % removal efficiency of ambient NO3−-N (16.5 mgL−1) and CIP (1 mg L−1) was achieved at pH 6.5, hydraulic retention time (HRT) of 8 h and carbon/nitrogen (C/N) = 2, respectively. However, it was observed that increasing the ambient CIP concentration above 1 mg L−1 significantly inhibited the manganese cycling and denitrification processes. The role of biomanganese oxides (BMO) in the redox removal of CIP was confirmed by product characterization. In addition, high-throughput sequencing confirmed the symbiotic relationship between manganese-cycling flora in the reactor, as well as verified the expression of genes related to core functions such as nitrogen metabolism and manganese cycling. [Display omitted] •Manganese redox cycle nitrogen removal system using microorganisms•Efficient removal of NO3−-N and CIP was achieved by immobilized Mn cycling flora.•The removal efficiency of NO3−-N and CIP was 77.4 and 92.5 %.•Expression of key genes for Mn cycling and nitrogen metabolism was confirmed.