Potential Application of a Pseudomonas geniculata ATCC 19374 and Bacillus cereus EC3 Mixture in Livestock Wastewater Treatment

Abstract

In this study, we isolated two bacterial strains, P2 (Pseudomonas geniculata ATCC 19374, P. geniculata ATCC 19374) and B1 (Bacillus cereus EC3, B. cereus EC3) from pig farm soil, which were mixed to construct a novel bacterial mixture (P2:B1 = 1:1). We studied the heterotrophic nitrification capablity and growth characteristics of bacterial mixture in heterotrophic nitrification medium (HNM). And the factors affecting the nitrogen removal of the bacterial mixture such as C/N ratio, NH4+-N load and inoculation size of the bacterial mixture were investigated in this study. Furthermore, we used the bacterial mixture to treat livestock wastewater to remove NH4+-N, TN and COD. The results showed that the optimal C/N ratio and inoculation size for the bacterial mixture were 12 and 5%, respectively. It is worth to mention that the bacterial mixture shows excellent NH4+-N removal ability under low C/N ratio, indicating that the bacterial mixture had the potential to be applied to wastewater with C/N lower than 8. When the initial NH4+-N concentration was 500 mg/L, the NH4+-N removal efficiency exceeded 90% with a 5% inoculation size of the bacterial mixture after 72 h. When the single bacteria and bacterial mixture were employed to treat livestock wastewater, the removal efficiencies of bacterial mixture on NH4+-N, TN and COD within 72 h were 70.06%, 58.12% and 81.48%, respectively, which were higher than that of single bacteria. The bacterial mixture has potential application value in enhancing the ability of reactors and constructed wetlands to remove pollutants from livestock wastewater and developing a novel and efficient biological nitrogen removal technology. Our current research provides a research basis for the application of the bacterial mixture in the future.