Flow augmenting devices for a wastewater treatment plant

A wastewater treatment apparatus is provided which includes at least an aeration chamber and a clarification chamber having a common wall therebetween, a transfer port opening through the common wall between a lower portion of the clarification chamber and the aeration chamber, an aerator mechanism in the aeration chamber for creating wastewater flow currents which flow through an inlet portion of a flow augmenting device located in the common wall above the transfer port. The flow augmenting device is a conduit or pipe having a discharge outlet adjacent the lower portion of the clarification chamber through which exits the flow from the aeration chamber resulting in solid particles being agitated and returned from the clarification chamber lower portion into the aeration chamber through the transfer port.

BACKGROUND OF THE INVENTION 
This invention is an improvement in wastewater treatment plants, 
particularly wastewater treatment plants of the type disclosed in U.S. 
Pat. No. 5,207,896 granted on May 4, 1993 and U.S. Pat. No. 5,264,120 
granted on Nov. 23, 1993, each being in the name of Jan D. Graves, and 
each being assigned to Norwalk Wastewater Equipment Co., of Norwalk, Ohio. 
In wastewater treatment plants of the type disclosed in the aforesaid 
patents, wastewater is introduced into a pretreatment chamber, flows into 
an aeration chamber, proceeds to a clarification chamber, flows through 
the assignee's BIO-KINETIC.RTM. settling system and exits the latter 
through an effluent discharge pipe. A transfer port is provided at the 
bottom of a common wall between the aeration chamber and the clarification 
chamber. Activated sludge settles in a lower portion of the clarification 
chamber adjacent the transfer port and transient hydraulic currents 
created in the aeration chamber by for example, a rotating aerator having 
a plurality of aeration nozzles or aspirator ports, lightly agitate the 
solids settled in the clarification chamber and they are, in part, mixed 
into suspension and carried back to the aeration chamber through the 
transfer ports by these transient hydraulic currents. These transient 
hydraulic currents are somewhat random and are less than 100% effective at 
returning settled sludge from the lower portion of the clarification 
chamber back to the aeration chamber. 
Settled sludge is made up of micro-organisms which accomplish the reduction 
of biological material in the aeration chamber, and it is essential to 
effectively return them to the aeration chamber. Therefore, having a less 
than a 100% effective return of the sludge from the clarification chamber 
to the aeration chamber is not advantageous for many reasons, most notable 
of which is that these activated sludge solids lose the benefit of being 
in suspension in the aeration chamber where they obtain the food and 
oxygen necessary to sustain themselves. Hence, they die or change to a 
less desirable form. Deprived of oxygen and their normal food source these 
micro-organisms are subject to other undesirable biological processes. 
These will naturally occur and can cause a degradation in effluent quality 
and reduce the efficiency of the overall system in removing pollutants. 
As another negative side effect of accumulated sludge in the lower portion 
of the clarification chamber, it is first noted that aeration accomplishes 
oxidation of nitrogen as a concurrent but separate step with carbonaceous 
(organic) oxidation. The oxidized nitrogen (nitrates) remains in the 
sludge and in solution, but when the activated sludge is allowed to 
accumulate in the bottom of a clarification chamber for a sufficient time, 
the dissolved oxygen is consumed and the micro-organisms turn to the 
nitrate-bound oxygen to breathe. This releases the nitrogen from the 
nitrate molecule and allows it to form gas bubbles which disperse 
throughout the "floc" causing it to become buoyant. Once sufficiently 
buoyant a clump or chunk of the floc will break loose from the sludge 
layer and float to the surface. This process of creating a bulking of 
buoyant sludge due to entrapped nitrogen gas bubbles is often referred to 
as denitrification. The sludge may remain at the surface for a time until 
further biological processes break it down or the minimal hydraulic 
currents in the clarification chamber break it up and the gas bubbles are 
released into the free air. However, while floating on the surface this 
sludge does not receive sufficient oxygen or food to stay healthy, and it 
is not returned to the aeration chamber to perform additional biological 
reduction. The sludge may wash out of the wastewater plant or plug 
downstream filters and/or settling plates, such as in the BIO-KINETIC.RTM. 
system heretofore noted. Hence, it is extremely advantageous to preclude 
the formation of sludge "bulk" or "float." 
SUMMARY OF THE INVENTION 
In keeping with the foregoing, a primary object of the present invention is 
to provide a device for augmenting wastewater flow between the 
clarification chamber and the aeration chamber to accomplish at least the 
following major functions substantially simultaneously: 
1. A positive return of settled sludge from a lower portion of the 
clarification chamber into the aeration chamber. 
2. Settled sludge that has accumulated on side walls of the clarification 
chamber is loosened thereby preventing a sludge build-up which would have 
the same negative effects as a lack of return of solids from the 
clarification chamber into the aeration chamber. 
3. Particles driven into suspension and kept sheared by the mechanics of 
the aeration chamber achieve a high degree of flocculation and 
subsequently settle better when passing through the BIO-KINETIC.RTM. 
filtering/settling device. 
4. The gentle mixing of the sludge at a lower portion of the clarification 
chamber strips small gas bubbles from entrapment within the floc particles 
without being intense enough to mechanically shear the floc which allows 
the floc to settle in the lower portion of the clarification chamber and 
be returned to the aeration chamber to thereby essentially preclude sludge 
bulking due to denitrification. 
Primarily, the latter functional advantages are achieved by the novel flow 
augmenting device of the present invention through the utilization of a 
pipe or conduit having an inlet end portion opening into an upper portion 
of the aeration chamber and an outlet end portion adjacent the 
clarification chamber lower portion and the transfer port in the common 
wall between the aeration and clarification chambers. Hydraulic currents 
are created in the aeration chamber by a conventional aerator and as 
surface hydraulic currents radiate from the aerator they are directed into 
the inlet end portion of the flow augmenting device, flow down a medial 
portion thereof and exit the outlet end portion adjacent the transfer port 
at the lower portion of the clarification chamber. These currents then 
create sufficient turbulence to agitate suspend, and/or re-suspend settled 
sludge material in the clarification chamber lower portion and return the 
suspended sludge material from the clarification chamber lower portion 
through the transfer port to the aeration chamber. 
Secondly, the currents created in the clarification chamber by the flow 
exiting the outlet end portion of the flow augmenting device induce 
gentle, vertical circular hydraulic currents in the clarification chamber. 
These vertical circular currents loosen settled sludge from inner surfaces 
of the walls of the clarification chamber and keep sludge from thereupon 
in large quantities. Activated sludge, by its nature, has a tendency to 
cling to the surfaces of a totally quiescent clarification chamber, and 
traditionally larger wastewater treatment plants use mechanical mechanisms 
to "scrape" the walls of the clarification chamber to inhibit this 
accumulation. Such mechanical scraping mechanisms are entirely eliminated 
by the present invention, along with costs incident to the operation and 
maintenance thereof. 
Thirdly, as floc particles are transferred to the clarification chamber 
from the aeration chamber by hydraulic displacement, they tend to be very 
small, almost discrete particles. Even though technically they are "floc," 
they have been agitated and mechanically sheared by the action of the 
aerator of the aeration chamber. Since settling in the clarification 
chamber is by gravity, the smaller the particle the less effective it 
settles and separates from the surrounding liquid. Many larger wastewater 
treatment plants use specifically designed flocculation chambers which 
gently stir the mixture allowing increased particle contact in a low shear 
environment. This allows the contact of the small particles with each 
other. Their natural adhesion causes them to coalesce into larger 
particles which settle better. It also provides contact and therefore 
adhesion of the floc to discrete particles which would not otherwise 
flocculate by themselves. Therefore, removal efficiency and overall 
process efficiency is increased. 
Lastly, the hydro-mechanical action created by the flow augmenting device 
strips small bubbles, specifically entrapped nitrogen gas bubbles 
(denitrification) entrapped within the flocced particles, without being 
intense enough to mechanical shear the floc. When these bubbles are 
released from the floc the floc can then properly settle in the lower 
portion of the clarification chamber and be returned to the aeration 
chamber through the transfer port for subsequent processing. Thus sludge 
bulking is minimized due to nitrification with attendant increase in 
process efficiency while minimizing operational problems. 
With the above and other objects in view that will hereinafter appear, the 
nature of the invention will be more clearly understood by reference to 
the following detailed description, the appended claims and the several 
views illustrated in the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The novel method and apparatus disclosed specifically herein includes 
improvements in the wastewater treatment plant disclosed in the 
aforementioned patents in the name of Jan D. Graves, and the totality of 
the disclosures of these patents are incorporated herein by reference. 
In keeping with the present invention a novel wastewater treatment plant or 
apparatus is generally designated by the reference numeral 10 (FIG. 1) and 
is normally designed for use with individual homes, although the same is 
readily adapted to many other facilities and is designed to utilize the 
well known digestion processes of wastewater or like fluid treatment. 
The wastewater treatment plant 10 includes an upper concrete casting 11 and 
a lower concrete casting 12. A wall 13 is common to and separates a 
pretreatment chamber 14 from an aeration chamber 15. Another wall 16 is 
common to and separates a clarification chamber 17 from the aeration 
chamber 15. 
Wastewater W from a suitable source (not shown) enters the pre-treatment 
chamber 14 through an inlet pipe 20 and flows beyond a depending baffle 
wall 21 through a transfer port 22 and a pipe or conduit 23 into the 
aeration chamber 15 via an outlet 24. 
A pair of stacked concrete cylindrical risers 25,26 are supported by a top 
wall 27 of the upper casting 11, and the cylindrical riser 26 is closed by 
a concrete cover 28 which includes a conventional fresh air vent assembly 
30. An aerator mechanism 31 is conventionally supported from the 
cylindrical riser 25 and includes a motor 32 which rotates an aerator 
shaft 33 having a plurality of aeration nozzles 34 from which air bubbles 
exit to effect extended aeration of the wastewater W within the aeration 
chamber 15. The rotation of the aerator 33 and the air exiting the nozzles 
34 create aeration chamber wastewater currents C which, along an upper 
surface U of the wastewater W in the aeration chamber 15, travel generally 
radially away from the aerator 33. 
Within the clarification chamber 17 there is located a BIO-KINETIC.RTM. 
filtering/settling mechanism, which is generally designated by the 
reference numeral 40, into and through which wastewater or effluent flows, 
particulate material is filtered or settled-out, and eventually the fully 
treated effluent discharges from the wastewater plant 10 through an 
effluent discharge pipe or line 41. The filtering/settling mechanism 40 is 
suspendingly supported from the top wall 27 of the upper casting 11 and 
access thereto is provided by two removable cylindrical concrete castings 
42,43, the latter of which is closed by a removable concrete cover casting 
44. Chlorination and dechlorination tablets are housed in respective 
chlorination and dechlorination tubes 45,46 for treating the effluent 
during its flow through the mechanism 40 and prior to exiting the effluent 
discharge pipe 41. 
The clarification chamber 17 includes a lower chamber portion 50 defined by 
the common wall 16, a tapering end wall 51 and opposite spaced tapering 
side walls of which only one of the tapering side walls 52 is illustrated. 
However, the walls 16, 51 and 52 generally define with a minor portion 
(unnumbered) of a bottom wall 54 the lower clarification chamber portion 
50 in which solids S tend to settle or accumulate adjacent a transfer port 
55 of the common wall 16 which places the aeration and clarification 
chambers in fluid communication with each other. 
Absent a novel wastewater flow augmenting device 60 of the present 
invention, the solids or particles S settle by gravity adjacent the 
transfer port 55 as settled sludge within the lower portion 50 of the 
clarification chamber 17 and tend not to flow through the transfer port 55 
back into the aeration chamber 15 with the resultant disadvantages 
heretofore noted. However, in keeping with the present invention the 
wastewaster flow augmenting device 60 creates hydraulic flow currents C' 
which gently agitate the solids S precluding the accumulation of sludge 
and reintroduce the solids S into the aeration chamber 15 through the 
transfer port 55. 
The wastewater flow augmenting device 60 is essentially a conduit or pipe 
which, as is best illustrated in FIG. 2, includes an inlet end portion 61, 
a medial portion 62 and an outlet end portion 63 having an outlet 64. 
The inlet end portion 61 of the flow augmenting device includes a generally 
polygonal inlet opening 65 defined by an upper wall 66, a lower wall 67 
and opposite side walls 68,69. The walls 66,67 merge with respective walls 
71,72 whereas the walls 68,69 merge with identical opposite walls 73,74 
(See FIGS. 3 and 4). The walls 71-74 converge in the direction of 
wastewater flow which in FIG. 2 is left-to-right. The walls 71-74 of the 
inlet portion 61 merge with respective walls 81-84 (FIGS. 3-5) of the 
medial portion 62 and the outlet end portion 63. Though the entirety of 
the flow augmenting device 60 is of a general polygonal cross sectional 
configuration, the wall 81 is slightly curved opening in a concave outward 
direction (See FIG. 5) to afford clearance during assembly, disassembly, 
servicing, etc. of the filtering/settling mechanism 40 which is of 
cylindrical exterior configuration. In an actual structural embodiment of 
the invention the concave wall 81 is defined by a 7.25" radius, the walls 
83,84 are approximately 31/4" and the wall 82 is 8", the measurements 
given being as the latter walls are viewed in FIG. 5 of the drawing. 
OPERATION 
As is best illustrated in FIG. 1, during the creation of the hydraulic 
currents C by the rotation of the aerator 33 and the air issuing from the 
nozzles 34, the surface currents C adjacent the upper surface U flow 
radially outwardly, as was described earlier and as is indicated by the 
upper series of wastewater flow arrows C of FIG. 1. This flow directs a 
portion of the wastewater W within the aeration chamber 15 into the inlet 
opening 65 and through the inlet end portion 61 of the wastewater flow 
augmenting device 60, as is best illustrated in FIG. 2 by the wastewater 
flow arrows C associated therewith. This flow continues down through the 
medial portion 62 and the outlet end portion 63 eventually exiting the 
outlet 64 of the wastewater flow augmenting device 60 resulting in the 
creation of the currents C in the clarification chamber lower portion 50 
of the clarification chamber 17. The currents C' form the numerous major 
functions described earlier including, of course, the agitation of the 
settled solids or sludge S and/or the mixture/agitation of the latter are 
creating unsettled solids in suspension which are carried back to the 
aeration chamber 15 through the transfer port 55, again as indicated by 
the arrows illustrating the flow direction from right-to-left in FIG. 2, 
for continued circulation by the current C therein. Thus, even though the 
wastewater flow augmenting device or flow augmentation device 60 is 
totally passive in its design and function in that it has no moving parts, 
the hydraulic currents C created in the aeration chamber 15 assure that 
any settled activated sludge in the clarification chamber lower portion 50 
will be returned to the aeration chamber 15 strictly through the 
utilization of the generated aeration chamber hydraulic currents C. In 
other words, the hydraulic currents C created in the aeration chamber 15 
are essentially transferred via the flow augmentation device 60 into the 
clarification chamber 17 to create the currents C' therein with attendant 
transfer of the particles or solids S through the transfer port 55 into 
the aeration chamber 15. 
The currents C' also "scour" the inner surfaces of the walls 16, 51 and 52 
to loosen accumulated settled sludge thereon in order to allow the latter 
to drift to the clarification chamber bottom portion or lower portion 50 
for eventual return to the aeration chamber 15 by the currents C'. The 
latter avoids the attendant necessity and associated cost of mechanical 
scrapers now utilized in the industry, and does so in an essentially 
maintenance free fashion. Since mechanical scrapers and other conventional 
mechanical sludge return devices are not utilized with the clarification 
chamber 15, hydraulic currents associated with the latter which are 
detrimental to clarification functions are totally avoided. 
It is also important to note that due to the relatively larger cross 
sectional configuration of the inlet end portion 61 as compared to the 
medial portion 62 and the outlet end portion 63 of the flow augmenting 
device 60, the velocity and therefore the effectiveness of the hydraulic 
action is increased by virtue of the Venturi effect. Thus the increase in 
velocity of the current flow C exiting the opening 64 assures requisite 
agitation of the sludge S through gentle hydro-mechanical action for 
sludge loosening and/or return which is best for floc preservation and 
minimizing floc shear. In addition, locating the discharge opening 64 of 
the flow augmenting device 60 adjacent the bottom wall 54 of the lower 
portion 50 of the clarification chamber 17 prevents short-circuiting of 
the hydraulic flow path and thus assures that the currents C' essentially 
continuously and uninterruptedly flow from the clarification lower portion 
50 through the transfer port 55 into the aeration chamber 15 and 
eventually co-mingling with the flow currents C. 
Another advantage of the flow augmenting device 60 is that larger floc 
particles formed in the aeration chamber 15 are carried to the bottom 
portion 50 of the clarification chamber 17 as opposed to being directed 
against the filtering/settling mechanism 40 at the upper surface U of the 
wastewater W within the clarification chamber 17, as would occur in the 
absence of the flow augmenting device 60. This effectively reduces 
filter/settlement "loading" of the mechanism 40 and increases the 
efficiency of the filtration/settlement operation thereof. This results in 
less cleaning and downtime of the system and optimum effluent at 
discharge. 
Since the wastewater flow augmenting device 60 functions strictly in 
dependence upon the aeration currents C, the wastewater flow augmenting 
device 60 is automatically demand controlled. If the wastewater or biomass 
in the aeration chamber 15 grows in volume, the operational adjustment 
recommended for proper control would be to increase the run time of the 
aerator mechanism 31, and additional biomass in the aeration chamber 15 
would also result in increased settled sludge in the clarification chamber 
17, both in the lower portion 50 and upon the walls 16, 51 and 52 thereof. 
With the additional increase in running time there is a corresponding 
increase in the total flow through the wastewater flow augmenting device 
60 which results in (a) an increase in the return of settled sludge or 
solids S to the aeration chamber 15 from the clarification chamber 17 via 
the transfer port 55, (b) additional scouring of the walls 16, 51 and 52 
by the hydraulic currents C' and (c) additional flocculation time. 
Apart from an increase in run time, the wastewater treatment plant 10 
normally operates in a cyclical fashion with the aerator mechanism 31 
operating during an "on" cycle and being cut-off during an "off" cycle. 
During such an "off" cycle there are more opportunities for the floc 
particles to contact each other and to contact discrete particles. This 
aids in "polishing" the biomass. Additionally, each time the flocculation 
process is cycled, the floc undergoes alternate flocculation and settling 
and such intermittent settling provides more opportunities for the floc 
particles to contact each other and to contact discrete particles, again 
aiding in the polishing of the liquid. During the "on" cycle the currents 
C' created by the wastewater flow augmenting device 60 inherently augment 
this polishing action through the continuous agitation of the particles S. 
Although a preferred embodiment of the invention has been specifically 
illustrated and described herein, it is to be understood that minor 
variations may be made in the apparatus without departing from the spirit 
and scope of the invention, as defined in the appended claims.