The Use of Aero-Hydraulic Guns in the
Biological Treatment of Organic Wastes
:. S. DUTTON, Associate Parmer
Proctor and Redfern
Civil and Consulting Engineers
Toronto, Canada
C. P. FISHER, Professor
Department of Civil Engineering
University of Waterloo
Waterloo, Ontario, Canada
INTRODUCTION
In part, because lagoon construction is relatively inexpensive, the use of
simple aerated lagoons in the treatment of degradable organic wastes has found increasing popularity over the past ten years. However, the degree of treatment
possible by the simple aerated lagoon has been limited not only by the process itself but by the nature of the available devices for accomplishing oxygenation.
Most of these devices, if not all of them, be they mechanical or diffused air aeration units, were developed primarily for use in the concrete basins of conventional
activated sludge plants; their application to the aerated lagoon was by default.
With such devices it may be possible to maintain sufficient turbulence within the
lagoon to ensure a reasonable distribution of oxygen throughout the lagoon contents but it is usually inadequate to maintain the Diological solids in suspension.
Such settled solids decompose anaerobically and result in an inferior effluent.
Furthermore, the importance of adequate mixing in a biological system is unquestioned; limited turbulence and inadequate mixing are synonymous. Because of the
geometry of aerated lagoons, access to such mixing and aeration devices is often
most difficult thus giving problems in maintenance; such problems would be
greatly reduced if the devices were not married to drive motors as are turbine
aerators, or prone to clogging as are small bubble diffusers. The development of
aerated lagoon systems for the treatment of both industrial and municipal wastes
could well be, to a great extent, the history of the development of the aerating
and mixing devices.
AERO-HYDRAULIC GUN
Some four years ago the writer became aware of a device that, in his opinion,
promises some real advantages for the mixing and aerating of lagoons and one that
could broaden the scope of aerated lagoon treatment. This device is the Aero-
Hydraulic Gun, a device that was conceived in Britain but became a landed immigrant in Canada at an early age. It would be appropriate at this time to describe the principle ofoperation of a single gun but in so doing itshould be realized
that a typical aerated lagoon would be equipped with not one but many such guns.
The gun, as shown in Figure 1, consists of a round polyethylene stack pipe (A)
of a design diameter and length, which has mounted inside its base a bubble generator unit (B). The gun is fixed in position in the lagoon by means of an anchor
bolt (D) placed on the lagoon bottom to which the unit is fixed by a metal bracket
(C).    A polyethylene air hose feeds supply air to the base of the bubble generator.
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