Lecture 6

Armenante njit dispersed air flotation air bubbles

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Unformatted text preview: the pressure PIERO M. ARMENANTE NJIT Dispersed Air Flotation • Air bubbles are formed by mechanically dispersing air injected under rotating impellers or sparged by diffusers • The bubbles formed under these conditions are typically too coarse for fine solid removal. Hence this method is not commonly encountered • Some scum forming waste can be removed by air dispersion flotation PIERO M. ARMENANTE NJIT Vacuum Flotation • Air is first dispersed into the wastewater to achieve saturation conditions • Partial vacuum is then applied to the wastewater. This results in the generation of small air bubbles that attach themselves to the solid particles and make them rise • Typically, a cylindrical tank maintained under vacuum and continuously fed with wastewater is used for this purpose PIERO M. ARMENANTE NJIT Dissolved Air Flotation (DAF) • Air is dissolved in pressurized wastewater (40 - 95 psia, i.e., 275 - 650 kPa) by adding air to the pump suction point • The air-wastewater mixture is admitted to a retention tank having a residence time or a few minutes to allow the air to dissolve • The wastewater passes through a pressure reducing valve and then enters a flotation unit where small bubbles (30 - 120 µm) are generat...
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This document was uploaded on 03/30/2014 for the course CHEM 685 at NJIT.

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