AWWA JAW56674

Spontaneous bubble formation (or air-binding) can reduce a treatment plant's overall efficiency and interfere with water treatment. Yet little research has been conducted to understand or mitigate this phenomenon. This article discusses the sources of bubble formation in treatment plants, their effects on the water treatment process, monitoring techniques for evaluating dissolved gases in water, and a method for determining bubble formation potential. Air entrainment and ozonation are the key causes of dissolved gas supersaturation and bubble formation. The authors conducted coagulation/flocculation jar tests and filtration experiments to evaluate the effects of bubble formation on these processes. These experiments' key findings were then tested in a case study at a water utility. The experiments showed that supersaturation altered or prevented agglomeration and increased final settled turbidity during coagulation/flocculation and increased head loss during filtration. The case study confirmed these findings. The authors concluded that bubble formation during coagulation and flocculation can potentially inhibit particle sedimentation and that gas supersaturation as low as 0.05 atm during filtration can decrease filter run time and be an important contributor to head loss. Includes 28 references, tables, figures.