Effective Treatment of Bulking Wastewater Using Floc-Forming Bacteria

Abstract

An experiment was conducted in a laboratory-scale reactor using paper wastewater to control the bulking phenomenon occurring in wastewater treatment sites effectively. The filamentous bacterium Sphaerotilus natans KCTC1629, which was a major cause of bulking, was introduced to induce bulking in the wastewater sludge. The optimal conditions for bulking induction by S. natans KCTC1629 were investigated. The optimal concentration and pH of the S. natans KCTC1629 culture broth were investigated by adding 1.0% glucose and 0.06% sodium sulfide to the culture medium. The highest SV30 and SVI values were achieved at 2.0% of the culture broth and a pH of 5.0, indicating that filamentous bacteria proliferated actively. The floc formation test with activated sludge makes Bacillus sp. DP152 the preferred strain for controlling bulking phenomena. In an investigation of floc size based on the concentration of the floc-forming bacteria, when 2.0% of the culture broth was added, the floc size increased significantly, reaching 13 mm in length. In a bulking induction test using the S. natans KCTC1629, the resulting SV30 value was 82.6% and SVI value was 364 mL/g, indicating well-induced bulking. To control the bulking, the culture broth of Bacillus sp. DP152, a biopolymer-producing strain isolated from nature, was used as a floc-forming agent. Bacillus sp. DP152 showed the highest production (16.7 g/L) after 60 hours of culture, and the viscosity of the culture broth reached 89,500 centipoise. In a bulking inhibition test using Bacillus sp. DP152, the SV30 value was reduced to less than 40% and the SVI value was 132 mL/g, indicating a very high sedimentation rate. As analysis of organic matter removal of floc-formic bacteria culture broth revealed COD reduction rate of 71% and TOC removal rate of 76%.