Multifunctional bacterium induced carbonate precipitation with low nitrogen effectively remediates cadmium polluted water

• Published in: Journal of water process engineering 2024-11, Vol.67, p.106204, Article 106204
• Main Authors: Song, He-Wei, Wang, Bao-Yu, Yu, Zhi-Guo, Kumar, Amit, Wei, Shu-He, An, Jing
• Format: Article
• Language: English
• Subjects: Cd immobilization; MICP; Multifunctional bacteria; NH4+-N removal
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2024.106204

Microorganism Induced Carbonate Precipitation (MICP) has emerged as an efficacious approach to address the issue of cadmium (Cd) contamination in water bodies. However, the associated production of ammonium nitrogen (NH4+-N) poses a significant challenge to the MICP. To tackle this, our research has developed a novel bacterium (UN-1), with dual MICP and NH4+-N degradation capabilities. We have elucidated the biogeochemical pathways of Cd2+ precipitation and NH4+-N degradation, characterized the micromorphology, phase composition, and crystallization of the MICP products, and identified the key factors influencing the MICP reaction. Our findings indicate that The UN-1-mediated MICP effectively removes Cd2+ at concentrations below 20 mg/L, reducing NH4+-N levels to 50 mg/L within 120 h. The predominant strains in UN-1 are Sporosarcina (24.35 %), Bacillus (31.36 %), Tumebacillus (6.89 %), Nitrospira (11.09 %), and Alkaliphilus (8.16 %). The bacterium employs urea enzymes UreA, UreB, and UreC for urea hydrolysis, thereby facilitating carbonate production, while the degradation of NH4+-N is mediated by hydroxylamine oxidase (HAO), nitrite reductase (NIR), and nitrate reductase (NAR). The resultant MICP products after Cd2+ removal are irregular spherical minerals, 200–300 nm in diameter, exhibiting well-developed single-crystal structures and high crystallinity. Their X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) patterns align with the characteristics of cadmium carbonate (CdCO3) minerals. Optimal conditions for the UN-1-led MICP reaction are identified as a pH range of 5.0 to 9.0 and a temperature range of 20 to 40 °C, the dissolved oxygen (DO) concentration in the water does not significantly impact the MICP. Furthermore, the study demonstrates that NH4+-N concentrations can be maintained at low levels under most conditions. This research introduces an innovative solution to the NH4+-N by-product challenge during Cd removal via MICP, laying a solid theoretical foundation for the development of a rapid, efficient, and eco-friendly remediation technology for Cd-contaminated waters. [Display omitted] •UN-1 has both MICP function and NH4+-N degradation function.•The main strains of UN-1 were Sporosarcina (24.35 %) and Bacillus (31.36 %).•CdCO3 was generated during the Cd removal process by UN-1-led MICP reaction.•The suitable condition of UN-1-led MICP reaction is pH 5.0–9.0, temperature 20–40 °C.•NH4+-N concentration can maintain low level a