Reducing the inhibitive effect of fluorine and heavy metals on nitrate reduction by hydroxyapatite substrate in constructed wetlands

• Published in: Journal of hazardous materials Vol. 446; p. 130692
• Main Authors: Wang, Jun-Feng, Zhou, Huan-Zhan, Tang, Guan-Hui, Huang, Jia-Wei, Liu, Hai, Cai, Ze-Xiang, He, Zhang-Wei, Zhu, Hui, Song, Xin-Shan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.03.2023
• Subjects: Bacteria - metabolism; Constructed wetlands; Environmental Pollutants; Fluorine; Heavy metals; Hydroxyapatites; Metagenomics; Metals, Heavy; Nitrate; Nitrates; Nitrogen - metabolism; Waste Disposal, Fluid - methods; Wetlands; Metagenomics; Nitrate; Fluorine; Constructed wetlands; Heavy metals
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2022.130692

Bio-toxic inorganic pollutants, e.g., fluorine (F) and heavy metals (HMs), in wastewaters are the potential threats to nitrate (NO3--N) reduction by microorganisms in constructed wetlands (CWs). Selection of suitable substrate with high F and HMs adsorption efficiency and capacity is a potential alternative for simultaneous removal of these pollutants in CWs. Herein, this study investigated the feasibility of applying hydroxyapatite (HA)-gravel media for F and HMs adsorption and its effect on NO3--N reduction in CWs (HA CWs) by comparing the CWs filled with gravel substrate (CK CWs). The results indicated that the removal efficiency of F, Cr, As, and NO3--N in HA CWs increased by 113.6-, 3.3-, 2.7-, and 0.6-folds, respectively, compared to CK CWs. The NO3--N reduction rate decreased by 11–46% in CK CWs after the presence of F and HMs in influent, while for HA CWs, it was only 13–22%. Excellent F and HMs adsorption capacity of HA substrate availed for wetland plants resisting F/HMs toxicity and making catalase activity lower. The HA substrate in CWs resulted in the certain succession of nitrogen-transforming bacteria, e.g., nitrifiers (Nitrospira) and denitrifiers (Thiobacillus and Desulfobacterium). More importantly, key functional genes, including nirK/nirS, korA/korB, ChrA/ChrD, arsA/arsB, catalyzing the processes of nitrogen biotransformation, energy metabolism, NO3--N and metal ions reduction were also enriched in HA CWs. This study highlights HA substrate reduce the inhibitive effect of F and HMs on NO3--N reduction, and provides new insights into how microbiota structurally and functionally respond to different substrates in CWs. [Display omitted] •The F removal rate in CWs is significantly increased by coupling with HA substrate.•Wetland substrates prefer to adsorb As(Ⅴ) cation rather than Cr(Ⅵ) in chromate.•The reduction rate of NO3--N is increased by about 60% in HA CWs compared to CK.•HA substrate avails for plants resisting F/HMs toxicity and making CAT lower in CWs.•Genes related to nitrogen transformation and electron production are enriched with HA.