Civil Engineering Reference
In-Depth Information
Raw
Water
Inlet
Treated
Water
Outlet
Air Discharge
Headers
Air Inlet
From Blowers
Top View (Without Lid)
Air Inlet
from Blowers
Air
Discharge
Air Flow
Air Piping
Air
Discharge
Headers
Raw Water
Inlet
Water
and
Air Bubbles
Treated
Water
Outlet
Water
Cross Section (During Aeration)
Fig. 9-12.
Multistage bubble aeration system (Courtesy of Lowry Systems)
(which means large space requirements), potential freezing problems in cold climates
and an inability to control off-gas with the open basins, and high energy requirements.
However, a study by Roberts and Levy comparing the energy requirements of me-
chanical surface aerators, diffused aeration, and packed tower aeration concluded that
mechanical aeration and packed tower aeration required approximately the same
amount energy to achieve the same efficiency (generally less than 0.0028 kW-h / ft
3
[0.1 kW-h / m
3
]).
20
Figure 9-13 shows schematics of two typical mechanical aeration processes. The
major components of such a system are the aerator and the basin. Surface aerators are
either mounted on fixed platforms or float on the basin surface.
Spray Aeration (Nozzles)
General Description
In spray aeration, water is forced through fixed nozzles to form
fine droplets. The small droplets that are produced expose a large interstitial surface
area through which a compound can migrate from the liquid phase to the gaseous
phase. Applications for spray aeration include oxygenation, as well as removal of
carbon dioxide, hydrogen sulfide, and taste and odor.
