Screening and combination of aerobic denitrifying phosphorus-accumulating bacteria for waste removal

Abstract:

[Background] In recent years, the expansion of mariculture has caused the massive accumulation of excrement and residual feed, which has increased nitrogen and phosphorus content in aquaculture waters, aggravating eutrophication and causing harm to the environment. [Objective] To screen out the aerobic denitrifying phosphorus-accumulating strains from mangrove constructed wetlands, determine the optimal nitrogen and phosphorus removal efficiency of each strain, and then optimize the strain combination by response surface methodology to further improve pollutant removal. [Methods] From the 5 strains of salt-tolerant heterotrophic nitrifying-aerobic denitrifying bacteria isolated in our previous study, the aerobic denitrifying phosphorus-accumulating bacteria were screened by metachromatic granules staining and poly-β-hydroxybutyric acid (PHB) staining. The optimal nitrogen and phosphorus removal conditions of each strain were determined by single factor test. Box-Benhnken design was performed in Design-Expert to optimize the strain combination. [Results] Three strains of salt-tolerant aerobic denitrifying phosphorus-accumulating bacteria were screened out, which were Achromobacter pulmonis strain E43, Achromobacter xylosoxidans strain J1, and Pseudomonas oleovorans strain F2, respectively. E43 was found for the first time to have the function of phosphorus accumulation. The optimal strain combination was determined as E43:J1:F2=1:1:4. The average removal rates of ammonia nitrogen (NH₄⁺-N) and phosphate (PO₄^3--P) by this combination were 91.28% and 93.03%, respectively. [Conclusion] The bacterial strain combination improved the average removal rate of PO₄^3--P, which provided a preliminary basis for the subsequent application in the actual treatment of saline wastewater. This study is an effective attempt for the assembly of aerobic denitrifying phosphorus-accumulating bacteria and provides a feasible method for the assembly of efficient functional bacteria.