Chemical oxygen demand reduction in wastewater by locally isolated Priestia sp. BA01 strain

Chemical oxygen demand (COD) refers to the oxidant content consumed by treating water samples with a certain strong oxidant under certain conditions, which is expressed in mg/L. This index is widely used in the world to reflect the degree of organic pollution in water. Using heterotrophic bacteria such as Bacillus sp. to reduce COD value in wastewater has become a common technology. The isolation and study of efficient and stable strains has great significance. In this study, a bacterial strain with COD reduction ability was isolated from the shallow soil of UPM campus. The physiological and biochemical study, and 16srRNA gene identification were carried out. The cultivation and application conditions were optimized. It was confirmed that the isolated BA01 strain belongs to Priestia sp. and the sequence has been submitted to NCBI GenBank. The GenBank number is PQ002608. For the cultivation conditions optimization, OFAT and orthogonal test methods were used. The best conditions are at 8 h, 35 ℃, 250 rpm and pH 7.0, which the biomass reached at 2.32×1010 CFU/ml. The pH value and rotation rate are significant. For application conditions optimization, OFAT and RSM were used. The best application conditions are at 35.22℃, pH 7.09, 215.45 rpm. Under these conditions, the COD reduction rate is 63.32%, 189.96mg/L. In addition, pH value is significant whereas the pairwise relationships are insignificant. Orthogonal experiments and RSM both aid in the systematic analysis of experimental results. Orthogonal experiments significantly reduce workload, but they have certain limitations in terms of interactions between factors. RSM can capture interactions and nonlinear relationships between factors, but it needs a greater number of tests than orthogonal experiments.