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An Acinetobacter calcoaceticus strain HM12 capable of heterotrophic nitrification-aerobic denitrification (HN-AD) under nutrient-poor conditions was isolated, with an ammonia nitrogen (NH 4 +-N) removal efficiency of 98.53%. It can also remove heavy metals by microbial induced calcium precipitation (MICP) with a Ca2+ removal efficiency of 75.91%. Optimal conditions for HN-AD and mineralization of the strain were determined by kinetic analysis (pH = 7, C/N = 2.0, Ca2+ = 70.0 mg L−1, NH 4 +-N = 5.0 mg L−1). Growth curves and nitrogen balance elucidated nitrogen degradation pathways capable of converting NH 4 +-N to gaseous nitrogen. The analysis of the bioprecipitation showed that Zn2+ and Cd2+ were removed by the MICP process through co-precipitation and adsorption (maximum removal efficiencies of 93.39% and 80.70%, respectively), mainly ZnCO 3 , CdCO 3 , ZnHPO 4 , Zn 3 (PO 4) 2 and Cd 3 (PO 4) 2. Strain HM12 produces humic and fulvic acids to counteract the toxicity of pollutants, as well as aromatic proteins to increase extracellular polymers (EPS) and promote the biomineralization process. This study provides a experimental evidence for the simultaneous removal of multiple pollutants from nutrient-poor waters. [Display omitted] • Isolation of Acinetobacter calcoaceticus strain HM12 capable of HN-AD co-MICP. • ExpDec1 model was used for kinetic analysis of strain HM12. • NH 4 +-N and Ca2+ removal efficiencies reached 98.53% and 75.91%, respectively. • Zn2+ and Cd2+ removal efficiencies reached 93.39% and 80.70%, respectively. • Strain HM12 has excellent adaptation to nutrient-poor environments. [ABSTRACT FROM AUTHOR]

Fluoride ions (F-) and phenol in groundwater have become a great hurdle to the pursuit of a healthy drinking water source. This study established a microencapsulated immobilization reactor with Aquabacterium sp. CZ3 for the simultaneous removal of nitrate (NO 3 --N), calcium (Ca2+), F-, and phenol from groundwater with 100%, 67.84%, 88.67%, and 100% removal efficiencies, respectively. The three-dimensional mesh structure of microcapsules facilitated the transport and metabolism of substances, while their synergistic effect with bacteria promoted the removal of contaminants. F- was removed by co-precipitation to generate Ca 5 (PO 4) 3 F and CaF 2 and adsorption. On one hand, the phenol toxicity promoted the production of extracellular polymers and improved the tolerance of bacteria; on the other hand, the degradation of phenol provided a carbon source for bacteria and promoted the denitrification. The development of microencapsulated immobilized reactor provided a clear mechanism for phenol and F- removal under the microbially induced calcium precipitation (MICP) technique, while providing a valuable solution for the treatment of complex groundwater resources. [Display omitted] • A microencapsulated immobilization reactor with AlCMC-CM composite was developed. • The immobilized reactor simultaneously removed NO 3 --N, Ca2+, F-, and phenol. • Phenol has both toxic and stimulating effects on the growth of Aquabacterium CZ3. • Moderate amounts of phenol promoted the secretion of tryptophan and EPS. • Three-dimensional microcapsules promoted the transport and metabolism of substances. [ABSTRACT FROM AUTHOR]

In recent years, it is urgent to solve nitrogen and phosphorus pollution in domestic wastewater. The target strain Pseudomonas sp. Y1 was immobilized using polyvinyl alcohol (PVA) matrix coupled with bentonite and lanthanum (La), respectively, to fabricate four hydrogel materials that used to construct bioreactors. The optimal operating parameters and dephosphorization mechanism were discussed, and the effects of hydrogel materials and different loads on the performance of the bioreactor were contrastively analyzed. The results manifested that when the hydraulic retention time (HRT) was 6.0 h, the C/N was 6.0, and the Ca2+ concentration was 100.0 mg L−1, the bioreactors had the best heterotrophic nitrification-aerobic denitrification (HNAD) and biomineralization capacity, and the maximum removal efficiencies of Ca2+, PO 4 3–-P, and NH 4 +-N were 82.57, 99.17, and 89.08%, respectively. The operation data indicated that the addition of bentonite significantly promoted HNAD, and the bioreactor had stronger dephosphorization ability in the presence of La. The main phosphorous removal mechanisms were confirmed to be adsorption and co-precipitation. Finally, high-throughput sequencing results indicated that Pseudomonas accounted for the paramount proportion in the bioreactor, and the prediction of functional genes indicated that the C/N of 6.0 is more favorable for the expression of nitrogen removal-related functional genes in the bioreactor system. This study highlights the superiority of microbial induced calcium precipitation (MICP) combined with PVA hydrogel, and provides a theoretical basis for simultaneous nitrogen and phosphate removal of wastewater. [Display omitted] • Bioimmobilized PVA hydrogels crosslinked with bentonite and La were prepared. • The addition of La effectively promoted the dephosphorization ability of the bioreactor. • The presence of bentonite increases the adsorption sites in the hydrogel. • The alkalinity produced by the HNAD process favors biomineralization. • MICP process is of great significance for phosphorus removal and recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • A HNAD strain Pseudomonas sp. Y1 capable of MICP was isolated. • The culture conditions of strain Y1 were optimized using kinetic analysis. • The removal efficiency of NH 4 +-N, PO 4 3−-P, and Ca2+ reached 92.04, 99.98, and 83.40 %. • MICP process is of great significance for phosphorus removal and recovery. Pseudomonas sp. Y1, a strain with superior synchronous removal ability of ammonia nitrogen (NH 4 +-N), phosphate (PO 4 3−-P), and calcium (Ca2+) was isolated, with the removal efficiencies of 92.04, 99.98, and 83.40 %, respectively. Meanwhile, the chemical oxygen demand (COD) was degraded by 90.33 %. Through kinetic analysis, the optimal cultivated conditions for heterotrophic nitrification-aerobic denitrification (HNAD) and biomineralization were determined. The growth curves experimental results of different nitrogen sources indicated that strain Y1 could remove NH 4 +-N through HNAD. The results of excitation-emission matrix (EEM) proved that the appearance of extracellular polymeric substances (EPS) promoted the precipitation of phosphate minerals. Finally, the characterization results of the bioprecipitates showed that the HNAD process produced the alkalinity required for microbial induced calcium precipitation (MICP), resulting in the removal of PO 4 3− via adsorption and co-precipitation. This study provides a theoretical basis for the application of microorganisms to achieve synchronous nutrient removal and phosphorus recovery in wastewater. [ABSTRACT FROM AUTHOR]

This research aimed to evaluate chitosan (CTS) and carboxymethyl chitosan (CMCS) as polysaccharides that could mimic the role of bacterial extracellular polymeric substance (EPS) in the biomineralization process through bionic experiments. The introduction of COOH resulted in higher calcium precipitation efficiency of CMCS (65.07%) than CTS (55.66%). CaCO 3 nucleation on the surface of CTS and CMCS was triggered through the binding of Ca2+ to NH 2 , OH, COOH and NHCOCH 3 groups. Moreover, the experiment of polysaccharides mediated biomineralization was conducted. The maximum calcium precipitation efficiency reached 96.07% with the addition of 0.15% CMCS. Combining the characterization results, the synergetic mineralization mechanisms between polysaccharides and bacteria were proposed. Among them, bacterial metabolic by-products (alkalinity), active groups and adhesion of polysaccharides played a significant role. This work provides a reference for further understanding of the biomineralization mechanism, and gives a new insight into the intensified strategies of MICP technology. [Display omitted] • Polysaccharides may act as the nucleation sites in the biomineralization process. • The feasibility of polysaccharides and bacteria co-mineralization was assessed. • CMCS had a higher compatibility as compared to CTS with strain WZ39. • The MICP efficiency was improved by 28.28% with the addition of 0.15% CMCS. • This work provides a new insight into the intensified strategies of MICP technology. [ABSTRACT FROM AUTHOR]