Effects of pH on biological treatment of paper mill white water with the addition of dominant bacteria

Abstract

Virgibacillus pantothenticus, Bacillus cereus, and B. subtilis were screened from an activated sludge that had become acclimated to white water in the laboratory. The effects of the pH on the ability of biological treatment to reduce the biological oxygen demand of white water was studied for three dominant bacteria. The pH ranged from 4 to 8, and the optimum treatment efficiencies for white water treatments with the single dominant bacterium V. pantothenticus, B. cereus, and B. subtilis occurred at pH values of 5, 6, and 6, respectively. The results also indicated that the best treatment effect was achieved at a hydraulic retention time of 14 h. When each dominate species was tested under their optimum pH value and hydraulic retention time, the chemical oxygen demand removal rate was 67.7%, 77%, and 75.4%; the electrical conductivity decreased by 0.18 mS/cm, 0.93 mS/cm, and 0.51 mS/cm; and the cationic demand decreased by 69.7%, 70.0%, and 70.9% for V. pantothenticus, B. cereus, and B. subtilis, respectively. These results are helpful for promoting the practical application of dominant bacteria in white water treatment.