Water Pollution Control with Two-Phase Dense-Bubble Plumes

Abstract

Miscible dense liquids discharged in a water environment form dense plumes. These plumes do not mix well with ambient water, and spread along the bottom. It is possible, however, to transform a dense plume into a quasi-buoyant plume by introducing a gas (e.g. air or oxygen) into the flow. This two-phase plume is named dense-bubble plume. An integral model is formulated to study dense-bubble plumes and assist in designing dense-bubble outfalls. The study shows that air flow has a significant effect on the development of a dense plume when it approaches a critical value. The plume reaches the free surface, and dilution is maximized, when air flow is greater than the critical value. When air flow is less than the critical value, only a fraction of the plume fluid is carried to the free surface. In this case, part of the plume separates, falls back, and spreads on the bottom. The critical supply of air is found to vary with water depth and discharge densimetric Froude number.