Ring channel aeration apparatus and method

In a ring channel aeration system, circulation is provided by one or more hydraulic jumps while the major portion of the energy consumed in aeration is allocated to the release of oxidative process gas through horizontally non-propulsive bubble release means having an oxygen transfer efficiency of at least about 6. The hydraulic jump(s) may be powered by discharge of gas (e.g. the same gas used for aeration) through gas discharge means, in which case the system of gas discharge means and bubble release means may have an overall oxygen transfer efficiency of at least about 6. The invention has advantages of flexibility and resultant energy savings as compared to single device circulation/aeration systems, in that excessive energy need not be consumed in aeration to obtain the requisite circulation and vice versa.

BACKGROUND OF THE INVENTION 
The present invention relates to ring-channel aeration systems and in 
particular to ring channel aeration systems having separate means for 
applying mixing energy and aeration gas to waste water. 
One widely known form of ring channel aeration system, known as the 
"oxidation ditch", is used to perform an extended aeration process and is 
generally a long narrow continuous typically oval or circular channel 
containing an aerating device. Oxidation ditches with brush- and 
paddle-wheel type aerators have enjoyed considerable commercial use both 
in Europe and the United States. 
Design specifications for oxidation ditches with capacities in the range of 
0.10 to 2.0 million gallons per day have been published by the U.S. 
Environmental Protection Agency. Such ditches are regarded as providing 
stable processing with proper sludge management, production of high 
quality effluent and predictable process behavior. Among the disadvantages 
of oxidation ditches which have been discussed in the literature are icing 
of aerator supports, the need for a crane to remove equipment for major 
maintenance, frequency of maintenance on drive units, the requirements for 
good operator skills and routine monitoring, the possible need for 
provision for nitrification oxygen and pH control, and the applicability 
of only one type of aeration device. 
However, oxidation ditches have long been known in which circulation and 
aeration have been provided by means which bubble air into the waste water 
in the ditch from a source beneath the water surface. For example, see 
U.S. Pat. Nos. 1,643,273, 3,336,016, 3,485,750 and 3,884,812. U.S. Pat. 
Nos. 3,495,712 and 3,947,358 disclose oxidation ditches having both 
stationary and moveable aeration means positioned beneath the surface of 
the waste water, the moveable aeration means serving to keep at least a 
portion of the contents of the ditch in motion. The latter patent teaches 
that it is unfavorable to provide an oxidation ditch with circulation 
means comprising transverse partitions having through-flow openings, in 
that such partitions considerably reduce the through-flow cross-section of 
the ditch and represent throttle zones, which have rendered known 
installations unsuitable for the treatment of large quantities of sewage. 
In contrast with the foregoing it has been suggested in U.S. Pat. No. 
3,846,292 to provide an oxidation ditch whose liquid flow path is free 
from obstructions to flow other than are unavoidably presented by certain 
ejectors submerged in the water, and to employ said ejectors as the sole 
means for aeration and movement of the liquid. Such installations are said 
to be particularly efficient in terms of reduced horsepower requirements. 
However, it has been suggested in the literature that ejectors have a 
poorer oxygen transfer efficiency than other known diffusers, such as for 
example ceramic dome fine bubble diffusers. 
Questions as to the oxygen transfer efficiency and operating costs of 
existing oxidation ditch systems, as well as continuously rising costs for 
energy, have created need for further improvements which offer higher 
efficiency. The present invention is directed to this need. 
SUMMARY OF THE INVENTION 
The foregoing object may be attained by providing a ring channel aerator 
with hydraulic jump means located in said channel. The hydraulic jump 
means extends between inner and outer wall means defining the channel and 
is oriented generally transversely of the flow path along which the 
waste-water circulates in the channel. The jump means is adapted to induce 
an upward and forward motion in the waste water as it passes through and 
out of the jump. Only a minor portion of the length of the flow path, 
measured along the centerline of the channel, is occupied by the jump 
means. Along the remainder of the flow path is positioned horizontally 
non-propulsive bubble release means having an oxygen transfer efficiency 
of at least about 6 for bubbling oxidative process gas into the waste 
water. 
The above apparatus is useful in a variety of processes, including an 
energy-saving method which is also considered to be part of the present 
invention. In this flexible and economic technique, a particularly 
advantageous balance is maintained between the energy consumed in 
circulation and the total energy used in circulation and aeration. 
According to the method of the invention, horizontal circulation is 
induced by imparting energy to the waste water within a minor portion of 
the length of a horizontal circulation path in a ring channel aerator. 
Along the remainder of said path, oxidative process gas is bubbled into 
the waste water through horizontally non-propulsive bubble release means 
having an oxygen transfer efficiency of at least about six. In this method 
the circulation rate preferably is less than about 1 foot per second 
averaged over the transverse cross-section of the channel. Circulation is 
induced by causing upward and forward motion of the waste water as it 
passes through and exits at least one propulsion zone or zones, such as 
for instance the hydraulic jump means mentioned above. The propulsion zone 
or zones are located in and extend transversely of the horizontal flow 
path, around which the waste-water circulates in the channel, but said 
propulsion zone or zones occupy only a minor portion of the length of said 
flow path, measured along the centerline of the channel. A ratio in the 
range of about 0.01 to about 0.35, more preferably about 0.02 to about 
0.25 and most preferably about 0.03 to about 0.2 is maintained between the 
horsepower consumed in inducing said circulation and the total of said 
horsepower plus the adiabatic horsepower consumed in the horizontally 
non-propulsive bubbling of process gas into the waste water. When the 
energy used to induce circulation is transmitted to the waste water by 
discharge of gas into the propulsion zone(s), this energy is also 
expressed in adiabatic horsepower for purposes of the above ratio. 
In the accompanying drawings, referred to below, and in the following 
description of preferred embodiments may be found illustrations of how the 
foregoing apparatus and method may be embodied and used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 disclose a preferred form of ring channel aerator 10 which 
may if desired be combined for purposes of convenience with an optional 
clarifier to be described in greater detail below. The ring channel 
aerator comprises inner and outer walls which may be of any appropriate 
shape so as to define a liquid circulation circuit of circular, oval 
(racetrack), elliptical, serpentine or other shape as viewed in plan view. 
Said walls may also be of vertical, sloping, curved or other suitable 
configuration as viewed in transverse cross-section. However, in the 
preferred embodiment the inner and outer walls 11 and 12 are circular as 
viewed in plan view (FIG. 1) and vertical in transverse cross-section 
(FIG. 2). A bottom wall is optional, such as for instance if the inner and 
outer walls slope to an intersection with one another, but the channel is 
preferably provided with a bottom wall 13, connected to inner and outer 
walls 11 and 12. The bottom wall is substantially horizontal for 
convenient mounting of diffusers, to be described in greater detail below. 
Walls 11, 12 and 13 define an elongated flow path which may in general have 
any appropriate width, length to width ratio, depth and internal 
configuration useful for ring channel aerators. While the width of the 
channel may vary around the circuit, the inner and outer walls in this 
embodiment are equidistant throughout the circuit or channel which they 
define. According to the presently preferred mode of practicing the 
invention, the ratio of the flow path length measured along the center 
line of the channel, relative to the average width of the channel measured 
throughout the height of its transverse cross section at and below the 
normal operating water level, is at least about 5. For example, the ratio 
of flow path length to channel width, measured as indicated above, may be 
in the range of about 5 to about 15 and more preferably about 8 to about 
10. 
The depth of the channel may be varied at different locations around the 
flow path, but the channel is most conveniently arranged to have a uniform 
depth throughout. Ring channel aerators are known which have channel 
depths as shallow as 3 feet and it will be possible to practice the 
invention in these shallow channels. But for the most part the invention 
will be employed in channels whose average depth, measured from the bottom 
of the channel to its normal operating water line, is at least about 5 
feet. For example, depths of about 5 to about 20 feet may be employed. The 
invention can be operated with particular advantage in channels having a 
depth of about 10 to about 20 feet, with about 12 to about 15 feet in 
depth being considered optimum. 
In general it will be seen that the walls 11, 12 and 13 define a continuous 
substantially closed course for liquid circulation such as is common to 
the extended aeration activated sludge type of oxidation ditch. Although 
not essential, it is preferable that the ring channel be substantially 
free of obstructions to flow other than the hydraulic jump means to be 
discussed below. 
The aerator may have one or more inlets and outlets of any appropriate 
configuration and location. In the present embodiment, the aerator is 
provided with waste-water inlet 16 which may be connected to a source of 
waste-water (not shown) which may for instance include a bar screen or 
comminutor followed by an aerated grit chamber with clarifier to dewater 
the grit. In this particular preferred embodiment sewage inlet 16 is 
closely adjacent and upstream of hydraulic jump means to be described 
hereinafter. A return sludge inlet, e.g. measuring weir 18, is closely 
adjacent to and upstream of said jump means and delivers sludge to the 
channel. This inlet is also preferably located just upstream of the 
aforementioned hydraulic jump. In this embodiment the effluent outlet is a 
transfer pipe 17, located more nearly upstream than downstream of 
waste-water inlet 16. Pipe 17 is preferably located a short distance 
upstream of the inlet and weir, and provided to withdraw mixed liquor from 
the channel. 
The optional clarifier may be of any conventional type, but certain 
economies can be attained if the wall of clarifier tank 22 is defined by 
the aerator inner wall 11. In this embodiment, the clarifier has the usual 
stilling well 23, scum trough 24, scum baffle 25, surface skimmer 26, 
effluent launder 27, and sludge collector drive 28. The clarifier includes 
a suitable sludge air lift and sludge divider (not shown) for sending 
recovered sludge back to the aerator 10 via weir 18, and/or to appropriate 
sludge holding or disposal facilities via waste sludge line 29. Clarified 
water from the clarifier may be carried by a conduit (not shown) to a 
receiving body of water or to suitable post treatment facilities. 
A bridge 30 (portions removed in FIG. 1), equipped with handrail 31 (FIG. 
2), extends along a diameter line of the apparatus from one side of outer 
wall 12 to the other, and in so doing bridges across the aerating channel 
10 and the clarifier tank 22. This bridge provides support for the sludge 
collector drive 28 and a means of access by which an operator may 
supervise the operation of the unit. 
According to the method of the invention, circulation is induced by causing 
upward and forward motion of the waste water as it passes through and 
exits at least one propulsion zone or zones. The propulsion zone or zones 
include lifting means, i.e. one or more members and/or media within the 
propulsion zone or zones, which directly apply a substantial net upward 
force vector or vectors to the waste water. Such lifting means may for 
example include impellers and/or gas discharge devices in a variety of 
configurations, with or without adjacent cooperating baffles (including 
shrouds), to apply the desired upward force vectors. For example, if the 
liquid propulsion means is a propeller, it may be mounted with its 
rotating axis horizontal and tangent or parallel to the channel 
longitudinal axis, and positioned to direct liquid downstream against a 
closely adjacent baffle inclined upwardly in the downstream direction. If 
the propeller axis is inclined upwardly in the downstream direction, it 
can produce both forward and upward motion in the liquid. A propeller 
having its rotating axis vertical may also produce the desired upward and 
forward motion in cooperation with suitable baffling by directing the 
propeller discharge against the underside of a baffle inclined upwardly in 
the downstream direction. The propulsion means, whether of the impeller or 
gas discharge kind, can be mounted within one or more shrouds or chimneys 
with which the propulsion means cooperates to directly apply the desired 
substantial net upward force vectors. Thus there is a substantial net 
elevation of the liquid as it proceeds through the propulsion zone(s). 
Such elevation is of assistance in inhibiting the deposition of suspended 
solids on the channel bottom between propulsion zones, even where the gas 
output of the horizontally non-propulsive bubble release means between 
propulsion zones is turned down to save power and is insufficient to keep 
all the solids in suspension. Preferably, the above-described lifting and 
elevating action is applied in such a way that each time liquid makes a 
complete circuit of the channel, substantially all of the liquid making 
such circuit is subjected to the lifting action, elevated, and propelled 
forwardly on the flow path, with or without a forward rolling action 
referred to in greater detail hereinafter. 
The velocity in the tank can be expressed in terms of a certain number of 
feet per second, averaged over the entire length and transverse 
cross-section of the flow path. This average will be the resultant of a 
multitude of additive and substractive vectors (including for example eddy 
currents) throughout the length and cross-section of the liquid circuit in 
the channel. Contributing factors to this average velocity are the 
velocities imparted by the propulsion means, by the introduction of 
waste-water and return sludge (if any) into the channel, and by the 
discharge of treated water from the channel. In most instances, the 
velocity contribution of the introduction and discharge will be very 
small. Thus, the velocity contributed by the propulsion means will be a 
multiple such as 10, 20 or 40 or more times the introduction/discharge 
velocity contribution. While the energy release in the propulsion means 
and the resultant velocity contribution should be sufficient to cause the 
liquid to continue in motion around the entire length of the channel, they 
are not so large as to cause an average velocity in the channel exceeding 
1 foot per second, which has frequently been mentioned in the literature 
as important from the standpoint of sufficiently inhibiting fall out of 
suspended solids in the channel. It has been found that the present 
invention can achieve effective mixing of untreated wastewater with the 
channel contents while adequately retaining solids in suspension even 
though circulating the channel contents at an average velocity less than 1 
foot per second. Thus although it is preferred that the circulation 
velocity be at least about 0.1 or 0.2 feet per second, the process can be 
successfully operated if the velocity is less than about 1 foot/second 
preferably less than about 0.7 foot/second, still more preferably less 
than about 0.5 foot/second and, in one recent installation, typically 
about 0.3-0.4 feet per second. Substantial energy savings can be realized 
through operating at these relatively low velocities. Low velocities 
restrict the amount of headloss sustained when passing the channel 
contents through a propulsion zone or zones having a passageway or 
passageways of substantially reduced cross-sectional area relative to the 
transverse cross-sectional area of the portion of the channel immediately 
upstream thereof. At these velocities, an energy efficient mode of 
operation can be carried out in which the energy released in the 
propulsion zone(s) is insufficient to keep the solids content of the 
wastewater in a substantially suspended condition throughout the channel. 
In such operation, the discharge of oxidative process gas through the 
horizontally non-propulsive bubble release means is distributed 
sufficiently extensively throughout the channel, and is sufficient in 
quantity and rate, so that such discharge is able, in combination with the 
lifting action of propulsion means in the propulsion zone(s), to keep the 
suspended solids contents of the tank substantially suspended outside the 
propulsion zone(s). Thus, the propulsion means is not required to sustain 
the entire burden of preventing dropout of suspended solids, and a portion 
of this burden is borne by the horizontally non-propulsive bubble release 
means which, in many cases, is able to bear this burden more efficiently 
than the propulsion means. However, it should also be understood that the 
lifting action generated in the propulsion zone(s), when combined with the 
lifting action of the horizontally non-propulsive bubble release means, 
may in many cases be sufficient to inhibit solids dropout outside the 
propulsion zone(s) even when the horizontally non-propulsive bubble 
release means is discharging oxidative gas in quantities per unit floor 
area (e.g. less than about 0.12 SCFM per square foot) and per unit of 
waste water volume (less than about 6 SCFM per thousand cubic feet) which, 
in and of themselves, have generally been considered insufficient for 
sustaining solids in suspension. 
The invention preferably utilizes a hydraulic jump means. In general the 
hydraulic jump means is located in the channel 10, extending between inner 
and outer wall means 11 and 12, generally transversely of the flow path, 
and may be any device which is capable of inducing upward and forward 
motion in the waste water as it passes through and out of the jump. Such 
device, or all such devices combined, should occupy only a minor portion 
(e.g. less than half) of the length of the circulation flow path measured 
along the centerline of the channel, and preferably occupy about 20% (or 
10%) or less of said length. Thus the jump means should be capable of 
inducing the requisite motion within the indicated portion of the flow 
path length. 
In general, the preferred mode of operation for the jump means is to 
establish upward flow in the jump while positively urging said flow in a 
forward (i.e. downstream) direction as the flow departs the jump. The 
forward flowing wastewater is discharged from the jump as a stream. It is 
preferred but not essential that this stream include the upper surface of 
the wastewater downstream of the jump. Again, although not absolutely 
essential, it is definitely preferred that the jump means direct the 
outgoing stream into a zone of abruptly increased cross-section 
immediately downstream of said jump. Such abrupt increase is of assistance 
in inducing a forward roll in the wastewater. 
When sufficient energy is imparted to the wastewater in the jump, it can 
form a wave in the wastewater as it exits the jump, and may even form a 
continuation of the rolling motion well downstream of the zone. With 
proper design of channel and jump geometry one may create forward-rolling 
eddy currents that roll forward,downward, rearward and upward, downstream 
of the jump, thereby extending retention of bubbles of oxidative process 
gas. In certain situations the rolling motion generated by the jump may 
also assist in flocculation of suspended solids in the wastewater. 
The structure of a particularly preferred form of hydraulic jump means may 
be described as a substantially upright chimney member extending for 
substantially the entire depth of the channel between its bottom and the 
normal operating water line of the channel. This chimney has an upstream 
inlet in the lower half of the channel depth and a downstream outlet in 
the upper half of the channel depth. The downstream end of the chimney may 
be connected to, or at least partly defined by, a member defining the 
abrupt change in cross-section referred to above. Said member preferably 
defines a sufficiently abrupt change in cross-section from the chimney 
outlet to the full cross-section of the channel downstream thereof for 
causing water which exits the chimney outlet to whirl or roll about a 
generally horizontal axis transverse to the flow path. 
A structure of the above type which is particularly preferred is disclosed 
in FIGS. 1 through 5. In the first two of these figures the hydraulic 
jumps 36 (of which there are two in this embodiment) are shown along with 
the rest of the components of the ring channel aerator, being shown from 
overhead in FIG. 1 and from upstream on the left side of FIG. 2. The jump 
alone is shown in enlarged sections in the next three figures, being shown 
in longitudinal cross-section in FIG. 3, transverse cross-section in FIG. 
4 and horizontal cross-section in FIG. 5. 
In the embodiment of FIGS. 1-5 the substantially upright chimney member 37 
extends through the entire depth of the channel between bottom wall 13 and 
the normal operating water line 38 of the channel 10. The chimney is 
defined in part by an upstream upper water baffle 39 and a downstream 
lower water baffle 40 and by portions of inner and outer channel walls 11 
and 12, as well as by channel bottom wall 13. 
As will be recognized by persons skilled in the art, the upstream water 
baffle 39 may have a variety of shapes, sizes and positions. However, in 
the present embodiment this baffle is combined with or part of a "Y" wall 
41 which, as viewed in the longitudinal cross-section of FIG. 3, includes 
a first limb 42 inclined rearwardly and upwardly, thus providing a 
transition surface for smoothly directly surface water downwardly along 
the upstream face of upstream water baffle 39 towards upstream inlet 43 
whose upper portion is defined by a lower edge 44 of baffle 39. Although 
it is particularly convenient for the upstream baffle to be combined with 
or part of a "Y" wall as shown and to extend well above the water line, 
one may actually employ any desired form of upstream water baffle that 
projects downward from an elevation at or above the water line part way to 
the bottom of the channel, and that is associated with an upstream inlet 
lying generally beneath, below or generally at the foot of said baffle. 
The elevation of the top and bottom of inlet 43 may be varied but it is 
believed that the optimum placement for the bottom of the inlet is at 
substantially the same elevation as the bottom of the channel. 
"Y" wall 41 of this embodiment also includes a second limb 47 inclined 
forwardly and in the downstream direction from the downstream face of 
water baffle 39. Although not essential, the inclined surface provided by 
limb 47 may be of assistance in positively urging the flow of water rising 
in the chimney 37 in a forward direction. Such inclined surface, when 
provided, preferably extends at an angle of at least 45.degree. relative 
the horizontal. Generally upright extensions 48 and 49 on "Y" wall limbs 
42 and 47 respectively may support a grating (not shown) providing a 
continuation of bridge 30 by means of which an operator may walk across 
the jump. Beneath such grating and in the space between limbs 42 and 47 
and extensions 48, 49 may be mounted supply pipes 50 and 51 for feeding 
gas to a gas discharge means (when such is provided to power the hydraulic 
jump) and to horizontally non-propulsive gas release means (to be 
discussed in greater detail below). 
Downstream lower water baffle 40 may be embodied in a wide variety of 
shapes, sizes and positions as will be recognized by those skilled in the 
art. In the present embodiment the downstream lower water baffle projects 
upward partway to the surface from an elevation at (including near) the 
bottom of the channel. 
As shown in this embodiment, baffle 40 includes an upwardly and 
downstream-directed inclined surface 55 which is of assistance in smoothly 
directing water received through inlet 43 in an upward direction into the 
chimney space between baffles 39 and 40. Baffle 40 has an upper edge 56 
which defines the bottom of a downstream outlet 57. The bottom of this 
outlet and its top (if it has one) may be varied in shape and position; 
however it is preferred that the top of the outlet, if such is provided, 
should be at or above the water line so that the forward flowing stream of 
wastewater discharged from the jump may include the upper surface of the 
wastewater which flows in the downstream direction as it departs the jump. 
Thus, outlet 57 should extend from beneath the water to an elevation at or 
above the normal operating water-line of the channel. 
The wide divergence of the downstream face of baffle 40 from the direction 
of flow through outlet 57 (e.g. by an angle of about 45.degree. or more) 
provides the abrupt change in cross-section referred to above. As 
explained above, if the water is caused to depart outlet 57 with 
sufficient energy there can be a whirling or rolling of the water about a 
generally horizontal axis downstream of baffle 40. A forwardly and 
downstream-inclined surface 58 on baffle 40 is of assistance in smoothly 
directing the lower portion of any such whirling or rolling currents 
upwardly along the downstream face of baffle 40, wherein such currents may 
join with additional wastewater departing outlet 57 for entraining bubbles 
and flocculating suspended solids as indicated above. 
Although the chimney as shown is defined by substantially vertical wall 
means it will be apparent that the chimney may be tilted forwardly or 
rearwardly so long as it is substantially upright. Thus, the substantially 
upright chimney member 37 may include baffles 39 and 40, the entireties or 
major portions of which are preferably vertical, as shown, or may be 
inclined from the vertical in the downstream direction by an angle of 
about 45.degree. or less, more preferably about 30.degree. or less and 
still more preferably about 15.degree. or less. 
Depending on the length of the flow path, one may provide one or any number 
of jumps at spaced locations along such path. A spacing of one hundred 
feet or more between jumps appears feasible. In general, it is desirable 
that the jumps be equally spaced along the path, but this is not 
essential. 
Because of its configuration, the hydraulic jump accelerates the flow of 
water which passes through it. This is accomplished in part by propulsion 
means (to be described in greater detail below) and in part by a reduction 
of the cross-section of the chimney as compared to the portions of the 
channel which are upstream and downstream of the jump. In general, the 
respective ratio or ratios of the areas of the inlet, chimney, and outlet, 
measured normal to the direction of flow in each of them, relative to the 
transverse cross-sectional area of the channel, measured at and below its 
normal operating water line and averaged along the entire length of said 
flow path, is in the range of about 0.2 to about 0.7. In respect to the 
inlet, a preferred value of said ratio is about 0.2 to about 0.5, with 
about 0.33 being considered best. Similarly, preferred values for the 
ratio of chimney area to average transverse channel cross-sectional area 
are in the range of about 0.2 to about 0.5, with about 0.33 being 
considered best. Usually the chimney horizontal cross-section will include 
a length-wise spacing between baffles 39 and 40 measured tangent or 
parallel to the channel longitudinal axis of at least about 3 feet to 
provide sufficient room for mounting of the propulsion means. Regarding 
the outlet, the values presently preferred and considered best for the 
above-mentioned ratio are respectively about 0.2 to about 0.5 and 0.33. It 
is considered advantageous if all of the foregoing ratios are relatively 
similar, to minimize head losses, whereby all three of the above-mentioned 
ratios are for example in the range of about 0.2 to about 0.5, more 
preferably about 0.25 to about 0.4 and still more preferably about 0.3 to 
about 0.37, with a ratio of about 0.33 being considered best, and that the 
chimney have substantially the same cross-section throughout. It is also 
beneficial if the inlet, the interior of the chimney and the outlet are 
all of substantially the same width as those portions of the channel which 
are closely adjacent to and both upstream and downstream of the chimney. 
It is preferred that the elevation of the top of the inlet should for the 
most part be at or appreciably below the elevation of the bottom of the 
outlet. 
In certain ring channel configurations, one's ability to attain economic 
operation may depend to some extent on the ratio of chimney width (side to 
side distance) to the depth of the water in the channel at the chimney 
location. In oval or racetrack style channels it is recommended that this 
ratio be at least about 0.7, more preferably at least about 1 and still 
more preferably at least about 2 or higher. However, this design criterion 
is deemed to be of lesser or no importance in plants with circular 
channels. 
In accordance with the invention the hydraulic jump means is provided with 
propulsion means which may be in a wide variety of types, shapes, sizes 
and positions. Preferably the propulsion means is positioned for 
distributing energy into the wastewater across substantially the entire 
width of the chimney. Such energy is utilized for causing the upward and 
forward motion to occur. With sufficient width-wise uniformity of 
distribution, the upward and forward motion of the water, with or without 
the above-described rolling motion, may occur across substantially the 
entire width of the chimney, but it should be noted that perfect 
uniformity is not necessarily essential or desireable. For example, in a 
ring channel aerator in which the wastewater following the outer wall must 
traverse a greater distance per circuit than the water which follows the 
inner wall, it can be beneficial to cause a relatively higher flow rate in 
the wastewater adjacent the outer wall as compared to that adjacent the 
inner wall. This may for instance be accomplished by providing the 
propulsion means with means for imparting energy to the wastewater at a 
higher rate adjacent the outer wall than adjacent to the inner wall. Also, 
it has been found that when the propulsion means is positioned for 
imparting the major portion of the energy to that half of the water in the 
chimney which flows nearest the upstream water baffle 39, undesirable 
short-circuiting of the water can occur within the jump, with resultant 
loss of jump effectiveness. Thus, it is recommended that care be taken to 
distribute the energy release substantially throughout the distance 
between the baffles 39 and 40 to inhibit short-circuiting. 
The propulsion means may be positioned within the chimney 37 and/or in one 
or more locations outside the chimney or in the chimney walls (from which 
locations the propulsion means may direct energy into the chimney). 
However, the preferred location for the upward propulsion means is within 
the longitudinal space between the upstream and downstream water baffles. 
As pointed out in the preceding discussion of the method of the present 
invention, a variety of devices are useable as propulsion means, including 
mechanical impellers and the like. But a considerable advantage in 
convenience and/or efficiency may be attained by employing a gas discharge 
means positioned in the chimney for inducing the motion described, the gas 
discharge means being preferably positioned for distributing bubbles 
across substantially the entire length and width of the chimney for 
causing said upward and forward motion. A suitable example of such gas 
discharge means is shown in FIGS. 1-5. It should be understood however 
that a wide variety of gas discharge means may be employed including, 
without limitation, the horizontally non-propulsive bubble release means 
described hereinafter, whether of the fine bubble type or not. 
The gas discharge means disclosed in FIGS. 1-5 is mounted in such manner 
that the gas discharged thereby is distributed across more than half and 
preferably across substantially the entire horizontal distance between the 
upstream and downstream water baffles. The gas discharge means may be of 
any configuration and may be mounted in any suitable location to 
accomplish the foregoing; however as shown in FIGS. 3-5 there are 
advantages of convenience and conservation of materials involved in 
positioning the gas discharge means on the upper water baffle. 
Referring now to FIGS. 3-5, the gas discharge means includes a conduit 
arrangement having a horizontal leg 64 connected to supply pipe 50 and 
extending through control valve 65 and "Y" wall extension 49 to a single 
vertical downcomer pipe 66 feeding into the center of a horizontal 
manifold pipe 67 extending transversely of the water flow path in chimney 
37, generally parallel to the downstream face of baffle 39. The diffusers 
68 are of the general type disclosed in U.S. Pat. No. 3,424,443 to Paul M. 
Thayer, the entire disclosure of said patent being incorporated herein by 
reference, and are distributed at uniformly spaced intervals across the 
width of the manifold and chimney and protrude horizontally from both 
sides of manifold 67 in the upstream and downstream directions, extending 
equally close to the inner surfaces of both of the baffles 39 and 40. 
In order to maintain manifold 67 in a fixed position against the force of 
the wastewater flowing up the chimney 37, it may be necessary to provide 
suitable structural supports (not shown) which will be readily designed, 
fabricated and installed by persons skilled in the art. But it may in 
certain circumstances be more desirable from the standpoint of reduced 
construction cost (for structural supports) and convenience (by providing 
the flexibility of being able to temporarily remove some but not all of 
the diffusers), if small groups of diffusers are provided with their own 
downcomers. Thus, such arrangement could be preferred over that shown in 
the drawings in certain circumstances. 
The diffusers are arranged in this embodiment so that they cover not more 
than about 25% of the lineal distance from one side of the interior of the 
chimney to the other side thereof. This tends to minimize the amount of 
interference that will occur between diffuser structure and the flow of 
water up the chimney. In this connection the use of concentrated bubble 
diffusers is particularly advantageous. Commercially available forms of 
diffusers shown in the above mentioned Thayer patent can for example be 
operated at an oxidative gas discharge rate in the range of about 0.05 to 
about 0.5 SCFM, and more preferably about 0.1 to about 0.3 SCFM, per 
square inch of chimney cross-sectional area, transverse to flow direction, 
occupied by the diffusers. 
It is believed that, from the standpoint of propulsion efficiency, there is 
an optimum rate of gas release per unit of length or area in a hydraulic 
jump. The optimum may vary to some extent, depending for example on the 
jump dimensions and the type and arrangement of the gas discharge means. 
However, by way of example, in a jump with the preferred coarse bubble 
diffusers and with a width (side to side) of 24 feet and a length 
(horizontal inside distance, baffle to baffle) of 3.5 feet it appears that 
the rate of discharge of gas through the gas discharge means, averaged 
over the width of the jump, should be in the range of about 1 to about 10, 
more preferably about 1.5 to about 4 and optimally about 2 to about 3 
SCFM, per foot of width. Correspondingly, the average oxidative gas 
discharge rate, averaged over the chimney cross-sectional area should be 
about 0.25 to about 3, preferably about 0.4 to about 1.2 and optimally 
about 0.55 to about 0.9 SCFM per square foot of chimney cross-sectional 
area, measured normal to the direction of flow where the gas is 
discharged. A jump designed in accordance with the above criteria appears 
capable of inducing adequate circulation along a channel length of 100 
feet or more, and of producing flow through the jump chimney at economic 
rates, e.g. at a rate of flow, measured in gallons per minute, which is at 
least about 30 or 40 times the product of the operating pressure (psi) and 
delivery rate (cfm) at the outlet of the blower furnishing gas to the gas 
discharge propulsion means in the jump. 
In general, the gas discharge means is advantageously positioned with its 
gas discharge outlets at a level of submergence equal to at least about 
half the depth of the upstream upper water baffle 39, measured downward 
from the normal operating waterline of the channel. It is presently 
considered that the optimum elevation for the gas discharge outlets is at 
about the same elevation as, or slightly below, the lower edge 44 of the 
chimney upstream inlet 43, and about 1 foot or more below the upper edge 
56 of downstream water baffle 40. Establishing the elevation of the bottom 
of the chimney outlet for the most part substantially above the gas 
discharge outlets of the propulsion means is preferred from the standpoint 
of affording sufficient opportunity for acceleration of the liquid in the 
chimney prior to reaching the outlet. Provided the rising gas bubbles and 
resulting liquid currents are not permitted to escape to the upstream side 
of the upstream upper water baffle 39, it will be found that the volume of 
wastewater pumped by the jump will increase with increasing depth of 
submergance of the gas discharge outlets. 
In general the horizontally non-propulsive bubble release means applicable 
to the invention are generally efficient aerators, but are not necessarily 
useful for fostering a net horizontal circulation of wastewater around the 
channel. The invention contemplates the use of bubble release means having 
the characteristic that one or more of them, collectively, are unable to 
produce a net or overall horizontal velocity of 0.3, or more preferably 
0.1, feet per second in wastewater in a ring channel, averaged over a 
longitudinal cross-section of said channel which passes through the bubble 
release means in question. A particularly preferred bubble release means 
produces no substantial net horizontal velocity measured in the above 
manner. On the other hand it should be noted that some of the applicable 
bubble release means may provide good localized mixing of the wastewater 
(e.g. in the vicinity of the bubble release means), but not necessarily 
so. For example, it is contemplated to employ in the invention bubble 
release means capable of emitting oxidative gas in a form and amount 
sufficient for satisfying the aeration requirements for treatment to a 90% 
removal of BOD.sub.5 and suspended solids at a retention time in the range 
of about 18 to 24 hours, and which may or may not be sufficient to mix the 
wastewater adequately to prevent sedimentation. 
Examples of useful bubble release means include fine bubble ceramic porous 
plate type diffusers, such being commercially available from Water 
Pollution Control Corporation of Milwaukee, Wis. and from others, as well 
as flexible plastic tubing type diffusers, which are commercially 
available from several sources (e.g. Lasaire tubing, a product of Lagoon 
Aeration Corporation of Milwaukee, Wis.). At least some of the 
commercially available tubing products release fine bubbles as defined 
herein. 
While the horizontally non-propulsive bubble release means is positioned 
along that portion of the flow path which remains after deduction of the 
portion occupied by the hydraulic jump means, this does not necessarily 
imply that the bubble release means extends along the entire remaining 
flow path, or that it covers the entire remaining floor area of the 
channel. It will not always be necessary to aerate throughout the flow 
path in order to maintain the wastewater in an aerobic condition; and 
there may be certain circumstances, such as for instance when it is 
desired to practice denitrification, when anaerobic conditions may be 
desired. Thus, although a given zone may be rendered anaerobic in a number 
of ways, such as for instance by introducing raw sewage and/or sludge 
having a high oxygen demand at the beginning of such zone, anaerobic 
conditions can also be attained by not aerating certain portions of the 
flow path outside the hydraulic jump means. There can be other reasons for 
providing bubble release means along only a portion of the remainder of 
said path. For example, it may be desired to employ bubble release means 
mounted on swing units, whereby such bubble release means may be swung up 
and out of the channel for servicing. In such circumstances it is 
beneficial to arrange the bubble release means in one or more relatively 
compact arrays. When a sufficient number of bubble release means are 
arranged in such a manner, and the oxygen requirements of the wastewater 
are not too large, oxygen transfer requirements may be satisfied even 
though substantial portions of the flow path between such arrays are 
unoccupied. In such case,the ceramic plate type diffusers may for example 
occupy as little as about 15 to 20% of the length of the flow path outside 
the hydraulic jump means, measured along the center line of the channel. 
Thus, the invention is not restricted to a particular percentage of 
occupancy of the remainder of the flow path by the bubble release means. 
However, it is nevertheless preferred that the bubble release means occupy 
at least about 40%, more preferably at least about 60%, and still more 
preferably at least about 90% of the length of the flow path measured 
along the centerline of said channel. It is considered optimum to have the 
bubble release means occupy substantially the entire flow path outside the 
hydraulic jump means. 
The degree of occupancy of that flow path, just mentioned, may or may not 
be equivalent to the degree of occupancy of the total floor area in the 
channel. For example, if the channel has a flat bottom with outer walls 
having a sloped configuration, and if the horizontally projected area of 
the sloping outer walls is regarded as part of the floor area of the 
channel, the flow path occupancy will not be equivalent to floor area 
occupancy. In such case the above mentioned percentages of occupancy, i.e. 
15-20%, 40%, 60% and 100%, may be based on the horizontal floor area of 
the channel outside the hydraulic jump means. 
Considerable flexibility of construction and operation may be attained when 
employing bubble release means which comprise plural arrays of diffusers 
with each such array comprising a plurality of diffusers having a common 
supply conduit. For example, when the diffusers are apertured tubing type 
diffusers they may be laid in segmented circular patterns which generally 
follow and extend along the flow path as illustrated in FIG. 1. When the 
diffusers are ceramic plate diffusers they may be arranged in arrays which 
include generally radially disposed supply conduits and horizontal headers 
arranged generally perpendicular to said supply conduits with the ceramic 
plate type diffusers being arranged at spaced locations along the headers 
as shown in FIG. 6. Such arrays may be spaced about or closely spaced to 
distribute oxidative process gas over a portion or substantially all of 
the area of the floor of the channel outside the hydraulic jump means. 
For additional details of preferred embodiments of the bubble release 
means, attention is drawn to FIGS. 1-3. These disclose the use of the 
above mentioned Lasaire.TM. tubing. In the figures, as best shown by FIG. 
1, the tubing is arranged in four separate arrays with individual air 
supplies each including tubing laid in the form of segments of a circle 
generally along the flow path around the channel. The four arrays 
indicated by reference numerals 74-77 terminate at the hydraulic jumps and 
at the 6 and 12 o'clock positions on the drawing; note that portions of 
arrays 74-76 are broken out in FIG. 1. The following description of arrays 
76 and 77 is analgous to arrays 74 and 75. 
FIGS. 1-3 show that arrays 76 and 77 have oxidative procoss gas supply 
conduits including horizontal legs 78 extending through individual control 
valves 79 and "Y" wall limb extensions 48 to downcomer pipes 80 and 
horizontal feeds 81, connected to manifolds 82. The horizontal legs 78, 
control valves 79 and downcomer 80 are all visible in FIG. 1, but only one 
of each is visible in FIG. 3, being hidden behind that one member of each 
pair which is visible in the figure. The tubing 83 is attached at equally, 
radially spaced points along manifolds 82 and is arranged in the circular 
pattern referred to above. The foregoing illustrates how at least some of 
the arrays can have separately controllable gas supplies connected to 
their supply conduits. By appropriate setting of valves 79 one may adjust 
certain of the arrays 74-77 to higher or lower gas rates per unit area of 
channel flow. Certain of the control valves 79 may also be closed to 
prevent release of gas from a portion of said arrays while other arrays 
are in operation. 
An alternate form of bubble release means is disclosed in FIG. 6, which is 
generally similar to FIG. 1, but employs ceramic plate type diffusers 
instead of the flexible aeration tubing described above. The embodiment of 
FIG. 6 includes the same channel, hydraulic jump arrangements, clarifier, 
sewage inlet, sludge inlet and mixed liquor outlet shown in FIG. 1. 
Instead of the oxidative process gas supply conduits 51, manifolds 82, 
tubing 83 and other associated conduits disclosed in FIGS. 1-3, the FIG. 6 
embodiment includes a supply manifold (not shown) which is connected to a 
source of oxidative process gas, such as air, and which may run around the 
base of inner wall 11 above or below bottom wall 13. To this manifold are 
connected a plurality of generally radially disposed horizontal supply 
conduits 88. Horizontal headers 89 are connected to said supply conduits 
at equally spaced intervals and arranged generally perpendicular thereto. 
Ceramic plate type diffusers 90 are arranged at spaced locations along 
each of said headers. It should be understood that each of the arrays 
includes the ceramic plate type diffusers 90, even though the diffusers 
are drawn in on only one of the arrays shown in the drawings. While these 
diffusers are spaced apart and therefore do not physically cover all of 
the area of the floor of the channel, they are distributed over 
substantially the entire floor area, so that they can supply gas to 
substantially all of the wastewater in the channel. 
As mentioned previously, when the oxygen transfer requirements of the 
process are not too large, it is possible to meet process oxygen 
requirements by employing a smaller number of diffusers than are shown in 
FIG. 6, such diffusers being arranged in relatively compact arrays whereby 
the diffusers are distributed over less than the entire floor area, and 
whereby substantial portions of the flow path outside the hydraulic jump 
means are not occupied by bubble release means. The foregoing is 
illustrated by the embodiment of FIG. 7. It discloses a ring channel 
aerator which is similar to that of FIG. 6 in certain respects. 
The FIG. 7 embodiment provides a channel 10 formed by inner and outer walls 
11, 12 and bottom wall 13. These three walls define a flow path for 
circulation of wastewater under treatment. Optionally inner wall 11 may 
surround or define a clarifier tank 22 similar to that shown in greater 
detail in FIGS. 1 and 2. Channel 10 has a wastewater inlet 16 in outer 
wall 12, and a transfer pipe 17 in inner wall 11 communicating with 
clarifier tank 22. As in the FIG. 6 embodiment there is a bridge 30 which 
extends across the aerator extending between the right and left sides as 
viewed in FIG. 7, said bridge being provided with handrail 31 (see FIGS. 3 
and 8). When a clarifier 22 is provided, its drive unit 28 may be located 
on bridge 30 centrally of tank 22. FIG. 7 includes a hydraulic jump 36 
like those used in FIG. 6 and disclosed in greater detail in FIGS. 1-5, 
and said hydraulic jump occupies a relatively small portion of the above 
mentioned flow path. 
Among the dissimilarities of the FIG. 6 and 7 embodiments is that the 
latter includes only one jump 36 instead of two. Also, in the FIG. 7 
embodiment bridge 30 has two extensions 32 and 33 extending horizontally 
perpendicular to the bridge, said extensions appearing to extend upward 
and downward respectively as viewed in plan view in FIG. 7. Whereas the 
horizontally non-propulsive bubble release means of FIG. 6 are secured to 
the bottom wall 13 of channel 10, said means are suspended from the bridge 
in three sets of relatively compact arrays 34 in FIG. 7. The three 
respective sets of arrays 34 are suspended, in clockwise order, from 
bridge extension 33, from the left portion of bridge 30 and from bridge 
extension 32. Note that a portion of bridge extension 33 is broken out to 
show that portions of all of said arrays 34 may extend beneath the 
respective portions of the bridge. Note also that the three sets of arrays 
34 are positioned along the remainder of the above mentioned flow path in 
such a way that significant portions 3 of the length of the flow path 
outside the hydraulic jump means are not occupied by the bubble release 
means. 
The respective arrays 34 include ceramic plate type diffusers 54 which 
receive oxidative gas via gas mains (not shown) and tees (not shown) under 
the respective bridge portions, said tees being connected to elbow 
fittings 45 secured to the respective bridge portions and connected to 
vertical downcomer pipes 46. The latter feed oxidative gas through 
half-headers 52 (52A,52B) and cross-headers 53 (53A-53H) to the diffusers 
54. The aforementioned elbow fittings 45, vertical downcomer pipes 46, 
half-headers 52 and cross-headers 53 may be arranged in a fixed manner 
whereby the diffusers 54 in said arrays 34 are fixedly secured in a 
horizontal plane a short distance, e.g. a few inches or feet, above 
channel bottom wall 13. 
However, it is preferred to provide for securing the arrays, with means 
having the capability of swinging said arrays up out of channel 10 to a 
position alongside the respective bridge portions for servicing. A number 
of devices of this type have been described in the prior art, but a 
preferred example is provided by U.S. patent application Ser. No. 115,470, 
filed Jan. 25, 1980, by Paul M. Thayer, for Improved Swing Diffuser, now 
U.S. Pat. No. 4,294,696, the entire disclosure of which is hereby 
incorporated herein by reference. One embodiment of the subject matter of 
said application, as applied to the present invention, is shown in FIGS. 
7-10 of the present disclosure. 
As shown in FIGS. 7-10, and particularly in the larger scale FIGS. 8-10, a 
plurality of hollow stanchion portions 45A of elbow fittings 45 are 
connected to the above mentioned air mains, tees and bridge or bridge 
extensions 30, 32, 33. Said fittings also include hollow swing elbow 
portions 45B which can pivot about stanchion portions 45A in essentially 
vertical planes. Downcomer pipes 46 are divided into rigid tubular upper 
hanger arms 46A and rigid tubular lower hanger arms 46B. Upper hanger arms 
46A are attached to elbows 45 so that arms 46A extend downwardly into the 
channel 10 below water level 38 as illustrated. Conventional hollow knee 
joints 59 pivotably connect upper arms 46A to lower arms 46B, so that a 
major portion or all of each lower arm 46B can be folded toward the 
respective upper arm 46A and the two arms rotated upwardly to a collapsed 
position at and/or above bridge extension 33. Although rigid, hollow arms 
are preferred both to carry the oxidative gas and to support the diffuser 
array, flexible tubing supported by rigid arms may also be used. 
At the lower portion of each arm 46B, in this embodiment at its lower end, 
a hollow swing elbow 60 is provided which is pivotably mounted to a hollow 
header connector 61, so that upper hanger arm 46A and header connector 61 
have their longitudinal axes in a common vertical plane. A pair of hollow 
half-headers 52A, 52B are rigidly connected to header connector 61 and 
extend laterally from the vertical plane of arm 46A and header connector 
61. For balance, half-headers 52A,52B preferably are of equal length. A 
plurality of cross-headers 53A-53H are mounted on top of half-headers 
52A,52B and preferably at right angles thereto. An array of diffusers for 
oxidative gas is defined by a further plurality of individual plate 
diffuser assemblies 54 extending upwardly from half-headers 53A-53H. 
Assemblies 54 preferably comprise diffusers of the type disclosed in U.S. 
Pat. No. 4,261,933 of Lloyd Ewing and David T. Redmon, in U.S. patent 
application Ser. No. 952,891, filed Oct. 19, 1978 by Lloyd Ewing, David T. 
Redmon, Paul M. Thayer, Frank L. Schmit and William E. Roche, for Sewage 
Aeration System (now abandoned) and in its continuation-in-part, Ser. No. 
102,175, filed Dec. 10, 1979, now U.S. Pat. No. 4,288,394, the entire 
disclosures of which are hereby incorporated herein by reference. However, 
those skilled in the art will appreciate that other types of diffusers 
could be used without departing from the scope of the present invention. 
Conventional header stops or rests (not shown), attached to the channel 10 
and/or to supports (not shown) on the outermost cross-headers, can be used 
to position the apparatus in the orientation shown in FIGS. 8 and 9. 
Alternatively, or in addition, the arrays can be used to position the 
apparatus in the orientation shown in FIGS. 8 and 9. Alternatively, or in 
addition, the arrays can be weighted to retain them in their desired, 
substantially horizontal operating position near the bottom wall 13 of the 
channel. 
A swing diffuser having many of its diffuser assemblies 54 located at a 
considerable distance from half-headers 52A, 52B can be readily used in 
the present embodiment, because the array 34 of diffusers can be pivoted 
to a substantially upright position (not shown) convenient for servicing. 
Handrails 31 on bridge 30 and its extensions 32,33 may include movable 
portions or gates (not shown) to accommodate upward pivoting of elbow 45 
and arms 46A,46B. Using conventional hoists (not shown) arms 46A and 46B 
are raised to folded position above bridge 30, while lever arm 62 and 
reach arm 63 cause rotational movement of each diffuser array 34 from its 
operating position to its servicing position. 
Lever arm 62 is rigidly attached to header connecter 61 and extends, in the 
illustrated embodiment, in a plane essentially parallel with the array 34. 
Of course, arm 62 need not be parallel with the array for the swing 
diffuser to function as indicated; however the parallel arrangement is 
preferred due to its compact geometry. Or, arm 62 may comprise one of 
cross-headers 53D,53E, suitably strengthened for the purpose, rather than 
a separate element as illustrated. Reach arm 63 is pivoted at its lower 
portion to the outer portion 70 of lever arm 62. The upper portion 71 of 
reach arm 63 is pivoted at a point fixed relative to but movable with 
upper hanger arm 46A. In the illustrated embodiment, upper end 71 is 
pivoted at the end of an offset flange 72 rigidly attached to the lower 
portion of upper hanger arm 46A. 
As indicated above, the arrays 34 of diffusers 54 occupy only a portion of 
the length of the remainder of the flow path, i.e. that portion which 
remains after deduction of the portion occupied by the jump 36, which 
itself occupies only a minor portion of the length of the flow path. 
Moreover, in the FIG. 7 embodiment the arrays 34 occupy only a relatively 
small portion of the remainder of said flow path. The percentage of said 
remainder which is occupied by said arrays can be determined on a plan 
view of the aerator by determining the fraction of said remainder which is 
covered by the envelope(s) surrounding the area(s) occupied by the 
diffusers. For example the envelope surrounding the area occupied by the 
diffusers 54 under the left end of bridge 30 in FIG. 7 is indicated by 
reference lines 73. 
In accordance with the invention, advantages of flexibility and savings in 
power may be realized through the feature of separate power means for the 
hydraulic jump means and bubble release means. According to a first aspect 
of this feature of the invention, it is preferred that the ring channel 
aerator comprise a first power means connected to the hydraulic jump 
means. This is for supplying energy to the jump and for inducing the 
upward and forward motion referred to above. A separate, second power 
means is connected to the horizontally non-propulsive bubble release mans. 
This is for supplying energy to the bubble release means to bubble 
oxidative process gas into the wastewater. According to a second aspect of 
this feature of the invention, it is preferred that the first and second 
power means be separately controllable. In this fashion the volume of 
oxidative process gas released through the horizontally non-propulsive 
bubble release means may be reduced or increased in response to reductions 
and increases in the oxygen demand of the wastewater. Because of the use 
of separate power means, as above described, such reduction or increase 
does not require corresponding reduction or increase in the energy 
supplied through the hydraulic jump means for circulation. According to 
still another aspect of this feature of the invention, it is preferred 
that the energy supply capacity of the second power means, as installed in 
the system, be larger than that of the first power means. More 
specifically, the capacity of the second power means may be sufficiently 
large in relation to the energy supply capacity of the first power means, 
for causing the second power means to supply the major portion of the 
total energy supplied by the first and second power means, both for 
inducing the upward and forward motion of the wastewater and for 
discharging oxidative process gas through the bubble release means. 
According to still another aspect of this feature of the invention, the 
hydraulic jump means may comprise gas discharge means for inducing the 
wastewater motion described above. In connection with any of the foregoing 
four aspects, either or both of the power means may be a compressor 
(including without limitation centrifugal blowers and positive 
displacement types) and a motor (including without limitation electric 
motors and internal combustion engines of all types), the respective power 
means being appropriately connected to the respective gas discharge means 
and bubble release means. 
A particularly preferred embodiment of the foregoing is disclosed in FIG. 
11. In the figure, the first power means 94 includes motor 95 having a 
controller 96 and connected via shaft 97 with compressor 98 having inlet 
99 and outlet 100. The controller 96 may be set manually or automatically, 
such as by means of a liquid level and/or liquid velocity sensing means or 
the like in the channel. The compressor 98 may be a single compresssor or 
a battery of compressors, may be arranged to draw process gas from 
atmosphere or elsewhere, and may have conventional inlet filters, water 
traps and other associated equipment (not shown). 
The first power means described above is connected via supply pipe 50 with 
hydraulic jumps 36 in two ring channel aerators 10I and 10II via master 
control valve 69 and individual control valves I65A, I65B, II65A andII65B 
for the individual jumps in the two ring channel aerators. With controller 
96, master control valve 69 and the individual control valves one may 
control the pressure in supply pipe 50 and the relative flow to the 
several jumps. This has a number of possible advantages. For example, it 
appears that more power is required to commence circulation in a ring 
channel aerator than to sustain circulation once the desired rate of 
circulation has been attained. Thus, for example, once circulation has 
been commenced, it may be possible to reduce the air flow to all jumps in 
a given aerator, or to shut off the supply of air to one or more of the 
jumps while maintaining the air rate to the other jump or jumps at the 
same level, an increased level or possibly even a reduced level. Moreover, 
the provision of separately controllable air supplies for the jumps within 
a given aerator afford opportunity for controlling the allocation of the 
horsepower consumed in circulation, as compared to the total horsepower 
consumed in circulation and horizontally non-propulsive release of 
oxidative process gas into the wastewater. 
As is also shown by FIG. 11, the embodiment described in the preceding 
paragraph also includes a second, separate power means 104 having motor 
105, controller 106, shaft 107, compressor 108, inlet 109 and outlet 110. 
Here again the controller 106 may be manually or automatically set, such 
as for instance by means for automatically sensing the oxygen demand of 
the wastewater in the ring channel aerator and converting the oxygen 
demand to a control signal to which the controller is responsive. As 
previously noted, the second power means may be, and preferably is, 
sufficiently large in relation to the energy supply capacity of the first 
power means, so that it supplies the major portion of the total energy 
supplied by the two power means. Thus, the major portion of the energy is 
supplied in this instance to eight arrays of horizontally non-propulsive 
bubble release means I74-I77, and II74-II77 via supply pipe 111, master 
air valve 84, branch conduits 112,113 and individual control valves I79A, 
I79B, I79C, I79D, II79A, and II79B, II79C and II79D. In this fashion the 
flow of air or other oxidative process gas to the manifold 82 and tubing 
83 of the several arrays may be separately controlled. This has a number 
of advantages. For example, it is of assistance in the allocation of 
energy consumption between circulation and horizontally non-propulsive 
bubbling of oxidative process gas into the circulating wastewater. 
Moreover it has been suggested in the literature that de-nitrification may 
be attained in a ring channel aerator by providing anaerobic zones. Thus, 
for instance, the ring channel aerators depicted in FIG. 11 could be 
provided with anaerobic zones by reducing or completely shutting off the 
flow of oxidative process gas to one or more arrays of the bubble release 
means which are downstream from the inlet(s) (not shown) for the 
wastewater and, if any, for the return sludge. Alternatively, for example, 
it is possible to direct the greatest part of the air flow to the array or 
arrays immediately downstream of the inlet(s) for the wastewater and 
return sludge (if any) in order to apportion the release of oxidative gas 
through the respective arrays in proportion or relation to the 
progressively reduced oxygen demand of the waste water as it moves further 
and further from the point of introduction in a given circuit around the 
channel. 
It has been found that when the gas discharge means for the jumps includes 
one or more concentrated bubble diffusers and the bubble release means is 
a means for discharging fine bubbles, the second compressor, connected to 
the bubble release means, will usually be operating against a 
substantially higher back pressure than the first compressor. In general, 
the difference in back pressures will be at least about 1.3 psi, more 
commonly about 1.5 psi and preferably at least about 2 psi. As compared 
with a system in which the total air requirements for the gas discharge 
means and bubble release means would be a common compressor or battery of 
compressors, the compression of the air for the gas discharge means 
against a lower back pressure can result in considerable savings of 
energy. 
When the hydraulic jump means comprises gas discharge means for inducing 
upward and forward motion of the wastewater, such gas discharge means can 
contribute to the overall oxygen transfer efficiency of the aerator. 
According to preferred embodiments of the invention the combined system 
oxygen transfer efficiency of the gas discharge means and bubble release 
means can be at least about 6, is more preferably at least about 7 and 
still more preferably is at least about 8. 
In the construction of wastewater treatment plants incorporating the ring 
channel aerators of the present invention, one may provide a plurality of 
co-located aerators having common facilities for treating effluent sludge 
and wastewater. This is illustrated by FIG. 12. As shown in the figure, 
three co-located ring channel aerators 10III, 10IV, and 10V are supplied 
by raw sewage main 118 and branch sewage supply pipes 119, 120 and 121. 
These aerators include clarifiers being similar to those disclosed in 
FIGS. 1-5. The waste sludge lines 29III, 29IV and 29V of these 
aerator/clarifier combinations are connected to and feed into common 
sludge holding tank 122, from which the sludge may be delivered to a 
processing facility, a land fill or trucks for remote disposal. Effluent 
water lines 123III, 123IV and 123V from the respective clarifiers are all 
connected to, and deliver clarified water from the clarifiers to, a common 
treatment vessel 124 which may for instance be a post aeration unit, a 
chlorinator or a combination of post aeration and chlorination facilities 
or other suitable facilities for final treatment of the water. 
FIGS. 13 and 14 disclose an embodiment of the invention having four 
aeration quadrants. It is otherwise similar in many respects to the 
embodiment shown in FIGS. 1-5, but parts have been removed to simplify the 
views, and means for flooding, purging and cleaning the hydraulic 
non-propulsive bubble release means have been added. In common with the 
FIGS. 1-5 embodiment, the ring channel aerator 130 of FIGS. 13 and 14 
includes inner wall 131, outer wall 132, bottom wall 133 to define a 
circulation channel. The resultant channel is provided with all of the 
various accessory items disclosed in and utilized in the operation of the 
FIGS. 1-5 embodiment such as for example a wastewater inlet and a treated 
water outlet. Ring channel aerator 130 surrounds a clarifier tank 135, the 
outer wall of which is defined by inner wall 131 of the ring channel 
aerator. As in FIGS. 1-5, clarifier tank 135 includes the usual stilling 
well, scum trough, scum baffle, surface skimmer, effluent launder, sludge 
collector drive, sludge return, sludge divider, (not shown) from which 
sludge may be delivered to the usual sludge holding or disposal facilities 
(not shown). 
The hydraulic jump means 136 of FIG. 13 is similar to that shown in FIGS. 
1-5, except that the upstream water baffle of this embodiment 
(corresponding to baffle 39 of FIG. 3) does not include a "Y" wall. As in 
the embodiment of FIGS. 3-5, the FIGS. 13 and 14 embodiment includes 
chimney 137 having disposed within it gas discharge means, i.e. diffusers 
138 arranged at spaced points across the width of chimney 137 and secured 
to either or both sides of propulsion air manifold 139 so that they are 
disposed horizontally and extend upstream and/or downstream (in relation 
to the general direction of flow in the ring channel aerator as a whole), 
approaching the walls of chimney 137 sufficiently closely to distribute 
bubbles throughout most of the length (distance between the upstream and 
downstream water baffles) of the chimney. The diffusers are of the general 
type disclosed in U.S. Pat. No. 3,424,343, supra. Suitable supply pipes 
are provided to conduct propulsion air to the propulsion air manifold 139. 
As in FIGS. 1-5 the hydraulic non-propulsion bubble release means comprises 
a plurality of arrays of Lasaire.TM. flexible plastic tubing type 
diffusers. Each of the four quadrants of the channel in ring channel 
aerator 130 includes inner aeration grids 145 comprising lines of the 
above mentioned flexible tubing positioned between reference lines 146 and 
147. Each such quadrant also includes outer aeration grids 150 lying 
between reference lines 151 and 152. Within each of such grids the lines 
of tubing are laid out upon equidistant circular lines generally 
concentric with the center of the circular clarifier and aeration channel, 
and are thus generally concentric with the aerator inner and outer walls 
131 and 132. 
Each of the inner and outer aeration grids is provided with its own 
individual gas manifold and drain manifold. Thus the four inner grids are 
provided with gas manifolds 156, 157, 158 and 159 while the outer grids 
are provided with gas manifolds 160, 161, 162 and 163, the respective gas 
manifolds being oriented radially relative to the center of inner and 
outer walls 131 and 132. At their radially inner ends the gas manifolds 
are connected with suitable headers (not shown) which in turn connect the 
manifolds with suitable pressure regulators, compressors and the like. The 
respective grids are also each supplied with individual drain manifolds 
including drain manifolds 166, 167, 168 and 169 for the inner grids and 
drain manifolds 170, 171, 172 and 173 for the outer grids. 
FIG. 14 is a sectional view taken along section line 14--14 of FIG. 13, 
showing additional details concerning the mounting of the flexible tubing 
diffusers and their respective gas supply flooding, purging and cleaning 
means. In FIG. 14 it may be seen that inner wall 131 and bottom wall 133 
in part define the channel and confine a circulating body of wastewater 
generally indicated by water surface line 175. The flexible tubing 176 of 
outer aeration grid 150 is disposed along its respective generally 
concentric layout line on the upper surface of bottom wall 133, having its 
inlet end connected to gas manifold 161 and an outlet end connected to 
drain manifold 171. Each of the respective drain manifolds in ring channel 
aerator 130 is mounted in a groove in bottom wall 133 such as the groove 
177 which is of sufficient width to receive all four of the parallel and 
closely adjacent drain manifolds 170, 171, 172 and 173, the inner drain 
manifolds 166 and 167 as well as outer drain manifold 170 being omitted 
from FIG. 14 to simplify the view. The inner gas manifolds 157 and 158 as 
well as outer gas manifold 162, all of which extend closely adjacent and 
parallel to gas manifold 161 of FIG. 14, have also been omitted from the 
Figure to simplify it. The purpose of groove 177 and corresponding 
radially oriented grooves for the remaining drain manifolds is to provide 
the opportunity for gravity drainage of liquid from tubing 176 into the 
respective drain manifolds. In common with the other gas manifolds 
throughout FIG. 13 the gas manifold 161 of FIG. 14 is provided with a 
water supply line 178, gas supply line 179 and cleaning gas line 180 
having, respectively, control valves 181, 182 and 183. In common with all 
of the drain manifolds throughout FIG. 13, drain manifold 171 of FIG. 14 
is provided with a drain line 185 having a valve 186 to open or close the 
line. 
In the normal operation of the ring channel aerator 130 of FIGS. 13 and 14 
the control valves 181 and 183 for water supply line 178 and cleaning gas 
line 180 will be closed and valve 182 for the gas supply line 179 will be 
open. Also valve 186 and drain line 185 will be closed. An aeration gas 
such as air is supplied through gas supply line 179 and is bubbled into 
the water in the channel through minute circular or oval holes bored at 
spaced intervals along the crown of the tubing 176. 
Normal operation of the system can result in the accumulation of water in 
the tubing 176, such as for example by condensation of water vapor 
contained in the compressed air supplied to the tubing. As this 
accumulation of water grows it can interfere with the proper distribution 
of air throughout the tubing system in the respective aeration grids. The 
drain manifold 171 provides a means for discharging such water 
accumulations while the plant is in operation. Accumulations of water in 
the drain manifolds may be discharged while the tubing system is under 
pressure by opening valve 186 in drain line 185, provided the pressure in 
the tubing system exceeds the hydrostatic head in drain line 185. 
As is well known, extended operation of diffusers in wastewater frequently 
results in the formation of encrustations of organic and/or inorganic 
foulants at the gas discharge orifices of the diffusers. Such 
encrustations can not only interfere with proper distribution of the 
aeration gas and increase energy costs by increasing the back pressure in 
the system but may also tend to reduce the oxygen transfer efficiency of 
the system. For this reason it has been conventional practice to clean 
flexible tubing type diffusers with a cleaning gas on an intermittent 
basis to remove the said encrustations and restore the plant, insofar as 
possible, to its original back pressure, air distribution uniformity and 
oxygen transfer efficiency. For example HCl and other gases may be 
employed. The cleaning gas may be supplied to the system in admixture with 
the aeration gas, so that it is not necessary to reduce the pressure in 
the tubing below normal operating pressure during cleaning. In the present 
embodiment this may be accomplished by opening valve 183 in cleaning gas 
line 180 while aeration gas is still flowing through gas supply line 179 
controlled by valve 182. If desired, the flow of cleaning gas can be 
completely substituted for the aeration gas by closing valve 182. The 
cleaning gas alone or in admixture with aeration gas enters manifold 161 
passes through tubing 176 and discharges through the gas discharge 
orifices of the tubing thus removing the encrustations. At the completion 
of cleaning, it is desirable to maintain the tubing under gas pressure at 
all times, by appropriate manipulation of valves 182 and 183. Thus, for 
example, if aeration gas supply line 179 has been closed off by valve 182 
during cleaning, the valve 182 should be opened as the cleaning gas line 
180 is closed by valve 183, whereby normal operating pressure may be 
maintained within the tubing as the flow of cleaning gas is terminated. In 
general, it will be found that the cleaning gas will operate with greatest 
effectiveness if cleaning is preceded by the water purging operation 
described in the previous paragraph. 
It has been found that termination of the flow of aeration gas through the 
tubing apertures, such as during a period of plant shut down for 
compressor or piping maintenance, can result in a flow of wastewater from 
the channel through the tubing apertures into the tubing. Such flow can 
deposit material in the apertures which impedes discharge of aeration gas 
when the plant is returned to operation. To prevent such occurrences it is 
recommended that the tubing be flooded with liquid that is substantially 
free of suspended solids at the time of shutdown and while there is still 
sufficient pressure in the tubing to prevent reverse flow of wastewater 
from the channel into the tubing. One may for example use non-potable 
water from a source within the wastewater treatment plant, which can be 
admitted to the tubing 176 by opening valve 181 while closing gas supply 
line 179, to keep the tubing under pressure provided the pressure 
available in water supply line 178 exceeds that in the gas manifold 161 
and tubing 176. Then water will be back up in line 179. Valve 178 may be 
closed after flooding is complete. In order to complete the flooding of 
the tubing it may be necessary to open valve 186 of drain line 185 for a 
time in order to purge the system of air. Provided the valve 186 is not 
opened excessively, sufficient gas pressure may be maintained in the 
portions of the tubing which have not yet been flooded, thus inhibiting 
reverse flow of wastewater through the tubing apertures in those areas. 
After flooding is complete the valves 181, 182 and 186 may be closed. 
During or after flooding, as above described, such as in a period of plant 
shut-down, or at any other time, the tubing may be flushed with 
non-potable water admitted through valve 181. For example, valves 181 and 
186 may be opened sufficiently to cause a flow of non-potable water 
through line 181, gas manifold 161, tubing 176, drain manifold 171 and 
drain line 185 at a moderate pressure, e.g. not exceeding about 30 psi, 
and in a volume sufficient to provide a flow velocity at about 3 feet per 
second in tubing 176. Thus, debris can be flushed out of the tubing and 
discharged through drain manifold 171 and drain line 185. After flushing, 
any remaining flush water may be retained in the tubing for a time to keep 
the tubing flooded, or may be purged immediately. The water used to flood 
and flush the tubing may be purged in a manner described above. 
In certain of the embodiments of the invention, such as for example that 
illustrated in FIG. 6, porous ceramic diffusion elements may be employed 
as the horizontal non-propulsive bubble release means. Such embodiments 
may also be provided with means for flooding, gas cleaning and purging in 
accordance with the general principles applicable to the FIGS. 13 and 14 
embodiment. While gas cleaning of porous ceramic diffusion elements has 
been suggested at least as early as the 1930s in the literature of the 
wastewater treatment art, an especially effective, efficient and useful 
technique for gas cleaning such diffusion elements is disclosed in U.S. 
Pat. application Ser. Nos. 191,974 (now abandoned) and 203,834 now U.S. 
Pat. No. 4,382,867, filed Sept. 29, 1980 and Nov. 4, 1980, by Frank L. 
Schmit, Lloyd Ewing and David T. Redmon, now U.S. Pat. No. 4,382,867, 
issued May 10, 1983, the entire disclosures of which are hereby 
incorporated herein by reference. 
Many variations of the apparatus are possible and, with the benefit of the 
prior description, can be readily formulated by persons skilled in the art 
without departing from the spirit of the invention. The process of the 
present invention can also be embodied in a wide variety of forms without 
departing from the spirit of the invention. Some of the possible 
variations are discussed below, it being understood that other variations 
may be made without departing from the spirit of the invention. 
According to the invention, anaerobic conditions may be maintained in a 
portion of the channel. However, according to a particularly preferred 
embodiment, aerobic conditions are maintained substantially throughout the 
channel. 
The attributes of the process are such that it is particularly attractive 
for ring channel aerators or colocated groups of ring channel aerators 
having a throughput of wastewater in the range of about 0.1 to 2 million 
gallons of throughput per day, and more preferably about 0.25 to about 1.5 
gallons of plant throughput per day, per unit. 
The process may be used in a wide variety of different types of 
applications. For example, the process may be employed in the aeration of 
industrial wastewater, which can vary quite widely in oxygen demand, and 
can also be used in the treatment of domestic sewage. For example, in a 
domestic sewage application, the wastewater may have an oxygen demand 
(including that required for nitrification, if any) of about 150 to about 
250 or more ppm BOD.sub.5, and the wastewater may be treated with about 
1200 to about 4500 or more pounds of oxygen per million gallons of plant 
throughput per day. However, the invention is also readily applicable to 
wastewater having an oxygen demand of about 100 to about 300 or more ppm 
BOD.sub.5 and to oxygen treatment of about 800 to about 5000 or more 
pounds of oxygen per million gallons of plant throughput per day. Much 
broader ranges of oxygen demand and oxygen treatment are possible and 
contemplated for use in the invention. 
In most instances, the method of the invention will be operated as a 
multiple pass operation in which oxidative process gas addition, 
wastewater addition, return sludge addition, if any, and effluent water 
and sludge withdrawal are balanced to provide a desired degree of 
treatment in retention times in the range of about 12 to about 36 hours. 
One example of a level of treatment attainable in accordance with the 
invention is a reduction of pollutants in the wastewater to levels of 
about 30 ppm BOD.sub.5 or less and about 30 ppm suspended solids or less. 
Another example is removal from the wastewater of at least about 90% of 
its initial BOD.sub.5 and of at least about 90% of its initial suspended 
solids, and conversion to nitrate ion of substantially all of any ammonia 
which may have been present in the wastewater. The process may also be 
operated in such a manner as to accomplish the foregoing in a retention 
time in the range of about 15 to about 30 hours and more preferably about 
18 to about 24 hours. 
As noted above, the wastewater may be a mixed liquor of domestic sewage and 
return sludge. Without any intention of limiting the invention, it should 
be noted that the amount of return sludge may for example be in the range 
of about 25% to about 125% by volume of the influent water, and preferably 
about 40% to about 100% by volume of the influent wastewater. 
According to a preferred embodiment of the invention, energy is applied to 
the wastewater in the propulsion zone or zones at the rate of about 0.5 to 
about 5 adiabatic horsepower per million gallons of daily flow of 
wastewater through the plant. Preferred and particularly preferred values 
of the foregoing, in terms of adiabatic horsepower per million gallons of 
daily flow of wastewater through the plant, are about 0.8 to about 3.5 and 
about 1 to about 3. 
The circulation rate induced in the wastewater by causing the upward and 
forward motion, as aforesaid, may vary considerably. While a given 
circulation rate may be selected in relation to the desired retention 
time, it may also be influenced by suspended solids, if such are present. 
Different wastewaters may or may not have significant quantities of 
suspended solids in the wastewaters themselves or in the aerated 
wastewaters. For example, domestic sewage and mixed liquors composed of 
domestic sewage and return sludge have substantial quantities of suspended 
solids. The process is preferably conducted while maintaining the majority 
of the solids in suspension until they are removed from the channel. 
According to one preferred embodiment of the method, sufficient energy is 
imparted to the wastewater in the propulsion zone or zones to form a wave 
in the wastewater as it exits said zone(s). Preferably the energy is 
sufficient to form a continuation of the rolling motion downstream of said 
zone(s) for creating currents in the wastewater that roll forward, 
downward, rearward and upward. Such currents can extend retention of 
oxidative process gas bubbles and assist in flocculation of suspended 
solids in the waste water. 
As indicated above, it is preferred to induce an upward and forward rolling 
motion in the channel by discharge of gas in the propulsion zone or zones. 
Preferably the gas is discharged at the rate of about 2 to about 3 SCFM 
per foot of side to side width inside of the propulsion zone(s). 
In the practice of the method, the rate of flow of gas into the propulsion 
zone(s) may be varied independently of the rate of flow of oxidative 
process gas through the bubble release means, and vice versa. 
According to the method of the present invention, a specified ratio is 
maintained between the adiabatic horsepower consumed in inducing 
circulation and the total of said horsepower plus the adiabatic horsepower 
consumed in nonpropulsive bubbling of process gas into the wastewater. 
Preferred and particularly preferred ranges for said ratio are about 0.02 
to about 0.25 and about 0.03 to 0.2. 
According to a preferred embodiment of the invention, the oxidative process 
gas may be introduced into the channel at a rate of about 10 SCFM or less 
per thousand cubic feet of liquid volume. Preferably said rate may be 
about 8 SCFM or less. The liquid volume referred to herein may be the 
liquid volume of the entire channel; alternatively, the liquid volume may 
be the volume of liquid above that portion of the floor of the channel 
over which the bubble release means is distributed. 
A particularly preferred form of the invention provides flexible allocation 
of horsepower consumption between circulation and aeration circulation at 
a rate of less than about one foot per second as described above. 
According to this embodiment about 0.5 to about 5 adiabatic horsepower are 
applied, per million gallons of daily plant throughput, for inducing 
circulation, while the rate of release of oxidative process gas is varied 
in response to the BOD of the wastewater and independently of the rate of 
discharge of gas through a gas discharge means which is used for inducing 
the circulation in a propulsion zone or zones. Simultaneously with the 
foregoing, the ratio of the foregoing horsepower, relative to the total of 
said horsepower plus the adiabatic horsepower consumed in non-propulsive 
bubbling of process gas into the wastewater, is maintained in the range of 
about 0.01 to about 0.3, more preferably about 0.02 to about 0.25 and most 
preferably about 0.03 to about 0.3. 
ADVANTAGES 
Provision of a ring channel aerator with horizontally non-propulsive bubble 
release means and hydraulic jump means for inducing circulation--and 
possibly also flocculation--enables one to separate the major portion of 
the work involved in the aeration of the wastewater from the work of 
circulating the wastewater; thus unlike aerating systems combining the 
functions of aeration and circulation, one need not employ excessive 
quantities of energy for circulation and/or mixing in order to obtain the 
requisite degree of aeration and vice versa. 
Where the energy released in the propulsion zone or zones is released by 
means of a gas discharge means and the bubble release means is a means for 
releasing fine bubbles, the gas for the gas discharge means may be 
compressed against a lower back pressure than the gas for the bubble 
release means, resulting in substantial savings of energy. 
Where the design of the ring channel aerator is such that it takes less 
energy to keep the channel contents in motion than to commence 
circulation, the amount of energy allocated to circulation may be reduced 
once circulation is established--without affecting or impairing the 
operation of the bubble release means through which the oxidative process 
gas is released. 
Separate controllability of the consumption of energy in the propulsion 
zone or zones as opposed to the remainder of the flow path (in which the 
horizontally non-propulsive bubble release means is operated) makes it 
possible to operate the plant in different modes to accomplish different 
results. Thus, for example, one may change the wastewater (e.g. mixed 
liquor) from aerobic to anaerobic, and then back to aerobic, such as for 
example might be employed in nitrification/denitrification. In systems 
with multiple hydraulic jumps, it may be possible to obtain some 
adjustment in the dwell time in the successive portions of the flow path 
between the jumps, by adjusting the relative rates of energy release in 
the respective jumps. 
The invention makes possible highly efficient aeration, not only in shallow 
channels, but also in deeper channels, such as for instance those about 10 
to 20 feet deep in which it has been found possible to operate with 
reduced energy consumption and/or increased oxygen transfer efficiency as 
compared with ring channel aerators using rotating brushes, rotating 
paddles or ejectors as the sole circulation and aeration means. 
Aeration in an activated sludge sewage treatment plant involves three 
functions: transfer of oxygen into the liquid being treated; mixing of the 
tank contents; and flocculation of the fines to promote better settling in 
a clarifier. Porous plates, domes and other types of aeration devices all 
have their particular strengths and weaknesses, but the present invention 
provides a hydraulic jump which can do the major portion of the mixing and 
flocculation, while a separate bubble release means does the major part of 
the work of aeration. The combined result is a particularly efficient 
attainment of the above mentioned three functions, as compared to many 
other aeration devices. 
Moreover, when circulation is induced by gas discharge means in the 
propulsion zone or zones, such gas may be oxidative gas which adds oxygen 
to the channel contents. This increases the available oxygen transfer 
efficiency, as compared to that available from the bubble release means 
alone. 
Other advantages of the invention will be apparent to those skilled in the 
art from the foregoing disclosure of the invention and from experience 
with its operation. 
DEFINITIONS 
Wastewater--water containing domestic sewage, industrial waste or other 
pollutants which can be ameliorated in or removed from the water by 
treatment which includes aeration. 
Aeration--introducing oxidative gas such as air, oxygen enriched air, 
oxygen, ozone or other gas capable of providing oxygen for reaction with 
pollutants in wastewater. 
Circulation--movement around a circuit in such a way as to repetitively 
return to and pass by a given point on said circuit. 
Ring channel--an open- or closed-top channel, conduit or other liquid 
carrying means having wall means which, as viewed in plan view, are laid 
out in a circular, oval, ellipsoidal, serpentine or other shape for 
guiding wastewater in a circuit during circulation. 
Concentrated bubble diffuser--a bubble release device adapted to release 
oxidative gas into wastewater through apertures arrayed in said bubble 
release device in a group containing a sufficient number of apertures to 
release oxidative gas at the rate of at least about 0.05 SCFM per square 
inch of the horizontal projected area of said group. 
Fine bubble diffuser--a diffuser which produces an array of bubbles in 
which those bubbles representing the major portion of the total volume of 
all bubbles in the array exhibit an average rise rate of about 0.8 foot 
per second or less while rising in said wastewater. 
Adiabatic horsepower (H.P.)--the horsepower consumed in compressing air in 
a pump (e.g. compressor) and discharging same under water through an air 
discharging device such as an aerator, as determined in accordance with 
the formula: 
##EQU1## 
where Q=volume air rate (SCFM), P.sub.2 =pump outlet pressure (psia), and 
P.sub.1 =pump inlet pressure (psia). 
Oxygen transfer efficiency (0.T.E.)--the pounds of oxygen absorbed in clear 
water under standard conditions (20.degree. C., zero dissolved oxygen, sea 
level barometric pressure) per horsepower hour. In determination of the 
0.T.E. of a complete aerating system, all horsepower consumed by the 
system for inducing movement of the wastewater and for discharging air 
into the water is considered, but adiabatic horsepower is used in the 
calculation for all aerating devices whether employed for non-propulsive 
bubble release and/or for inducing circulation of the wastewater. In 
determination of the 0.T.E. of an aerating device or group of such 
devices, only the horsepower (adiabatic) consumption of the device or 
devices is considered. 
Horizontally non-propulsive--as applied to one or more bubble release means 
in a ring channel, signifies that such bubble release means, collectively, 
are unable to produce a net horizontal velocity as great as 0.3 or 0.1 
feet per second in the wastewater, averaged over a longitudinal 
cross-section or sections of the channel passing through the bubble 
release means. 
Substantially upright--as applied to the baffle means of a hydraulic jump 
means, indicates on the average more nearly vertical than horizontal. 
In--as applied to gas discharge means, includes within, extending into or 
on. 
Induced--caused, commenced and maintained, or merely maintained. 
The invention is illustrated by the following nonlimiting example: 
EXAMPLE 
An oval ring channel aerator was constructed with vertical side walls and a 
flat bottom to accommodate a normal water depth of 10.5 feet, which could 
vary from 8 to 12 feet. The channel comprises two parallel straight 
sections 24 feet wide by 78 feet long, positioned side by side, and 
separated by a 1 foot thick common inner wall of the same length. Two 
semi-circular continuations of the outer walls each having 24.5 foot radii 
join both ends of the outer walls of the straight sections to one another 
to form an oval racetrack flow path having a length of about 233 feet, a 
liquid capacity at the 10.5 feet depth of about 440,000 gallons and a 
nominal ultimate capacity of about 500,000 gallons. 
A hydraulic jump extends perpendicularly from each side of the central 
dividing wall at its mid-point, extending across the entire width of the 
two straight sections of the channel so that all of the liquid which makes 
a complete pass around the channel must pass through both jumps. Each jump 
includes upstream and downstream water baffles each extending across the 
entire width of the channel and having no wastewater passageways other 
than the inlets and outlets described below. The two jumps, including 
their respective baffles occupy approximately 4% of the flow path. The 
inlet of each jump is 3.5 feet high throughout its width, and its bottom 
coincides with the channel floor. The sides of the inlets, chimneys and 
outlets of both jumps coincide with the side walls of the straight 
sections of the channel and are thus each 24 feet wide. The bottoms of the 
outlets are 7 feet above floor level and extend above the intended water 
line of the body of wastewater to be treated in the plant. 
For gas discharge means each jump is provided with eight (8) Sanitaire D-24 
stainless steel coarse bubble diffusers mounted at approximately equal 
intervals of distance from one another across the width of each chimney 
with the diffusers in a horizontal plane at approximately the same 
elevation as the top of the chimney inlet and extending generally parallel 
to the direction of the overall flow in the channel. Half of the foregoing 
distance separates the end diffusers from the adjacent chimney side walls. 
The upstream ends of the twenty-four inch long diffusers are connected to 
manifolds running horizontally across the inner surfaces of the upstream 
water baffles so that their upstream ends are 6 inches downstream from 
these inner walls. Thus the diffuser downstream ends are located 14 inches 
from the inner surfaces of the downstream water baffles. The 16 diffusers 
(total) in the two jumps are connected to a blower adapted to produce 160 
SCFM. 
As hydraulic non-propulsive bubble release means approximately 7600 feet of 
the above described Lasaire.sup..TM. flexible tubing is secured to the 
bottom wall of the channel in straight lines parallel to the center 
dividing wall. Air headers are secured perpendicular to the direction of 
liquid flow in the channel and at floor level closely adjacent to the 
upstream and downstream ends of the jumps. The uniformly spaced apart 
lines of tubing extend perpendicularly from these headers throughout all 
four of the racetrack quadrants into which the oval racetrack is divided 
by the two jumps and the central dividing wall. Extending in unbroken 
straight lines from the respective headers, the lengths of tubing 
terminate adjacent the semi-circular end walls to which they are secured 
in groups of five by suitable tensioners. Through respective headers and 
suitable valving arrangements, these tubes, averaging about 49 feet in 
length, are provided with selectable connection to either or both of two 
blowers each capable of producing 275 SCFM. 
The channel was filled to a depth of 10 feet with clear water, air was 
supplied to the diffusers in the jumps at a blower output pressure of 2.3 
psi, delivering about 3.1 SCFM of air to each jump per foot of jump width. 
The flexible tubing type diffusers were supplied with air through one of 
the two 275 SCFM blowers at a blower output pressure of 6.1 psi. 
Satisfactory operation of the jumps ensued, resulting in positive 
displacement circulation of the channel contents at an average velocity of 
about 0.3 to about 0.4 feet per second. 
Into the plant was introduced a 300,000 gallons per day flow of wastewater 
believed to comprise the following proportions of liquid flow: 
______________________________________ 
Percent 
______________________________________ 
Domestic sewage 68 
Effluent from transformer plant 
5 
Effluent from creamery 
4 
Infiltration 23 
100 
______________________________________ 
It is estimated that the organic load (BOD.sub.5) in the above flow was 
divided approximately as follows: 
______________________________________ 
Percent 
______________________________________ 
Domestic 64 
Transformer Company 
3 
Creamery 33 
100 
______________________________________ 
Over a three day period of operation at 50.degree. F. the BOD.sub.5 
(Raw-Composite) of the incoming wastewater varied from 350 to 1550 with an 
average of 934 pounds per day. The plant was operated as described above, 
except that during the eight hours of heaviest load on week days (Monday 
through Friday) both of the 275 SCFM aeration air blowers were operated. 
The average BOD.sub.5 removal was 888 pounds per day, leaving only 46 
pounds per day in the 300,000 gallons per day of effluent, i.e. 18 ppm. 
Dissolved oxygen levels in the channel were in the range of 1 to 4.2 ppm. 
Grab samples of effluent showed suspended solids levels ranging from one 
to 24 mg/l, averaging about 10 mg/liter. Delivery of 160 SCFM of air at 
2.3 psi to the jumps consumed 37.5 adiabatic horsepower hours per day. 
Delivery of 275 SCFM and 550 SCFM for aeration for the indicated periods 
consumed an average of 210 adiabatic horsepower hours per day for a total 
horsepower of 247.5. The propulsion horsepower (i.e. energy utilized in 
the jumps) represented 15% of the total, and 3.59 pounds of BOD were 
removed per adiabatic horsepower hour.