Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02592998 2007-07-10
DESCRIPTION
WASTEWATER TREATMENT TANK WITH INFLUENT GATES AND PRE-REACT
ZONE WITH AN OUTWARDLY FLARED LOWER PORTION
Technical Field
This invention relates to a wastewater treatment tank
with influent gates (to create turbulent flow and reduce
influent flow velocity) and a pre-react zone director having
an outwardly flared lower portion. The pre-react zone
director causes laminar flow of influent below a settling
blanket of sludge to avoid disturbing the blanket, thus
allowing the blanket to function as a filter and resulting in
a clearer supernatant than in conventional tanks.
Wastewater treatment facilities play an important role in
society. As urban and rural populations continue to grow,
however, these facilities become increasingly overtaxed and
unable to meet the demands placed upon them. These increased
demands cause many current wastewater treatment plants to
operate near or at capacity. In addition, many treatment
facilities were originally constructed decades ago, and
utilize technology that is currently failing. Failing or
inadequate.treatment facilities pose an environmental concern,
especially in light of increasingly stringent municipal,
state, and federal environmental standards.
Due to the odious nature of wastewater treatment
facilities, these facilities have often been constructed far
from the sources of sewage to minimize exposure to populated
areas. As a result, long sewage lines are needed to connect
treatment plants to sewage sources. However, the acidic,
corrosive and septic nature of wastewater, including hydrogen
sulfide gas, which naturally occurs during the wastewater
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treatment process, causes the breakdown and failure of long
sewage pipes
To alleviate these problems, many areas have undertaken
to either construct more treatment facilities, or to increase
the efficiency of existing facilities. The construction of
new facilities, however, may be blocked by those who fear the
negative impact of such a facility in close proximity to urban
or rural areas, such as the emanation of offensive odors, and
the potential risk of untreated wastewater spillage.
Increasing the efficiency of existing plants can come at great
cost, and also poses the risk of interrupting current service.
In order to increase efficiency, and to lower consumer
costs, many areas have privatized wastewater services.
However, like any business, these private wastewater plants
must be economically viable, and are faced with maintenance,
energy, and other costs, which reduce profits and impede
business growth.
Rapid development and population growth of third world
countries also pose a significant sanitation and health risk,
as wastewater needs cannot be met by current services.
Therefore, these areas are especially in need of low cost,
highly efficient wastewater treatment plants.
Back5lround Art
U.S. Patent 5,302,289 to McClung, et al., discloses a
wastewater treatment facility having an inlet in which there
are a plurality of downwardly angled structures in a
downcomer.
U.S. Patent 4,230,570 to Irving discloses an aerator
having an inlet having a downward and outward direction at the
bottom, and adjacent inlet air provided by a manifold.
U.S. Patent 5,051,213 to Weske discloses a method and
apparatus for mixing fluids, which includes tines that are
adjacent to gas inlets.
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U.S. Patent 4,162,971 to Zlokarnik, et al., discloses the
use of deflecting elements to mix liquids and gas.
U.S. Patent 4,081,368 to Block, et al., discloses the use
of staggered partitions in treating wastewater.
U.S. Patent 4,505,820 to Eertink discloses the use of
multiple separate bioreactors in treating wastewater.
U.S. Patent 4,705,634 to Reimann, et al., discloses the
mixing of wastewater and activated sludge in the presence of
carrier particles for microorganisms.
U.S. Patent 4,136,023 to Kirk, et al., discloses an
apparatus for wastewater treatment in which oxygenated
wastewater is directed out through an adjustable flap.
U.S. Patent 5,688,400 to Baxter, Sr. discloses a waste
liquid treatment plant, which includes aeration for downwardly
flowing liquid, air nozzles, and a conical section.
U.S. Patent 3,804,255 to Speece discloses a recycling gas
contact apparatus for waste material, which includes a
downflow conducting cone member and bubble injector.
U.S. Patent 4,421,648 to Besik discloses a single
reaction tank in a single suspended growth sludge system that
includes a conical shaped outlet section.
U.S. Patent 4,452,701 to Garrett, et al., discloses an
open-bottomed stilling chamber above an open-topped chamber
with a conical outlet.
It is therefore an object of this invention to provide
methods and apparatus for a wastewater treatment system,
having influent gates and pre-react zone with outwardly flared
lower portion to achieve tertiary treatment results (at least
in certain fields of use) from a secondary treatment facility
using a single tank. In this connection, primary treatment is
usually understood to include settling and anaerobic
processes, secondary treatment is usually understood to
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include aerobic processes, and tertiary treatment is usually
understood to include filtering.
It is a still further object of this invention to provide
methods and apparatus for low-cost, high-efficiency wastewater
treatment systems.
It is a still further object of this invention to provide
a process and apparatus that substantially reduces production
of sewage sludge.
It is a still further object of this invention to provide
a process and apparatus that reduces energy consumption by
reducing the number of pumps and blowers needed for operation.
It is a still further object of this invention to provide
an apparatus with minimal moving parts.
It is a still further object of this invention to provide
such methods and apparatus that combines processes to
eliminate the need for multiple stage components, thereby
eliminating the odors, maintenance and land requirements, and
other costs associated with multi-stage complex wastewater
systems.
It is a still further object of this invention to provide
methods and apparatus resulting in more nutrient and chemical
removal than previous wastewater systems.
It is a still further object of this invention to provide
methods and apparatus which is simple in construction and
operation so that malfunctions can be easily and quickly
diagnosed to reduce the costs of repair and maintenance.
It is a still further object of this invention to provide
methods and apparatus that are scalable so that multiple
smaller decentralized plants can be used instead of large
centralized plants with long pipelines, which , allows
geographic dispersal of such plants and reduction of peak
flows of effluent in particular areas.
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It is a still further object of this invention to provide
methods and apparatus that allow plants of particular capacity
to be constructed using up to 50% less land.
It is a still further object of this invention to provide
5 methods and apparatus that can be operated with less manpower.
It is a still further object of this invention to provide
methods and apparatus that allow multiple modular plants with
continuous influent flow and intermittent decanting to allow
the environment to recover between decants, and allows
multiple staggered decanting so that common effluent
facilities need only have the capacity to handle one or two
(or more, but less than all) modules at a time.
It is a still further object of this invention to provide
methods and apparatus that can be easily retrofittable to
existing properly sized basins.
It is a still further object of this invention to provide
methods and apparatus that denitrify the system by both
aerobic and anaerobic processes to avoid algae blooms.
Disclosure of Invention
These and other objects are achieved by a device to treat
influent that includes a basin with an influent gate housing
in the basin to receive influent. Influent gates are mounted
inside the influent gate housing so that influent flows over
the influent gates, creating turbulent flow and aeration in
the influent, and reducing flow velocity of the influent. An
influent gate bottom is mounted in the basin under the
influent gate housing so that influent exiting the bottom
portion of the influent gate housing is directed laterally. A
pre-react zone director having an outwardly flared lower
portion is mounted to the basin and at least partially
encloses the influent gate housing. The pre-react zone
director defines a main react zone inside the basin, but
outside the pre-react zone director, and the lower portion of
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the pre-react zone director is spaced apart from the bottom of
the basin and defines a contact zone between the lower portion
and the bottom of the basin. The pre-react zone director
decreases influent flow velocity and directs flow of said
influent in a laminar fashion through the contact zone and
into the main react zone, so that the influent avoids
disturbing any settled sludge in the main react zone and
allows formation of a supernatant. The influent does not
disturb the settled sludge and is filtered through the sludge
(which acts as a biological filter) before forming the
supernatant, so that the supernatant is comparable to filtered
supernatant. Thus, settling (the settling sludge blanket),
aerobic processing (passing the supernatant over the gates),
anaerobic processing (the biological activity in the settling
sludge blanket) and filtering (passing the influent through
the settling sludge blanket to form the supernatant) are all
performed in a single basin.
This invention substantially reduces sewage sludge
production and energy consumption by wastewater treatment
systems, by utilizing a non-mechanical process that uses fewer
pumps and blowers than a conventional wastewater treatment
system, and utilizes a minimum of moving parts. It reduces
plant size, and therefore reduces land requirements, by up to
approximately 50% from that of conventional wastewater
treatment facilities, and requires only approximately 6 months
to 1 year of design and construction time. This invention
also requires less manpower and maintenance due to fewer
components.
Furthermore, as the use of septic tanks is being
restricted by state and municipal regulations, affecting both
residential and commercial properties, this invention allows
for a septic tank replacement, without having to expend time
and money to connect these properties to a large centralized
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system, or to construct an entirely new sewage infrastructure.
This is particularly advantageous for remote small scale
commercial developments.
This invention therefore allows the construction of
smaller plants closer to the sources of sewage, resulting in
shorter sewage pipes, which allow a shorter resident time of
influent within the pipes, and therefore significantly reduces
exposure to sewage and the possibility of failure.
This invention allows a continuous sewage influent flow
into a single basin wastewater treatment system. The modular
nature of the invention allows multiple basins to be used,
thus allowing multiple staggered decanting so that effluent
facilities can be shared and do not have to be as large as
conventional ones. This intermittent decanting allows the
environment to recover between decanting.
The influent flow travels over the influent gates,
creating turbulence in the flow and reducing downward flow
velocity. The resulting turbulent flow allows air, in the
form of minute bubbles, to be mixed into the influent stream,
which starts aerating the influent flow. These minute bubbles
also cause a reversing action of the influent flow upon
contact with the surface of the wastewater in the basin. This
reversing action reduces downward velocities, and thus works
in conjunction with the influent gates. The exit of the
influent gate housing is below the level of wastewater in the
basin.
There are preferably one or more influent gates located
within the influent gate housing. These gates are preferably
located above the lowest normal wastewater level within the
basin. To utilize their turbulent flow/aeration properties,
however, gates may also be placed below the wastewater level
if further flow velocity reduction is required. Although
utilizing no gates falls within the operable range of the
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invention, it is preferable to have at least one gate.
Optimally, there should be more than one gate installed to
achieve the best quality effluent.
The influent gates are strategically spaced with the
first gate preferably placed approximately one diameter down
the vertical influent riser from the influent intake. The
first gate is optimally placed approximately where the
influent would first hit the wall of the influent gate housing
on the side opposite the incoming influent flow. Subsequent
gates would preferably be mounted on alternating sides of the
interior of the influent gate housing. The flow will thus
have a horizontal backward/forward motion as it travels
vertically down the riser portion of the influent gate housing
(the influent riser). Although it is within the operable
range of this invention to have the gates placed in many other
positions within the influent gate housing, the gates should
preferably be placed in a zig-zag manner down the vertical
influent riser, spaced apart from each other by approximately
the diameter (or width) of the riser. Enough gates should be
provided so that the lowest gate is above the lowest
wastewater level (bottom water level) expected during normal
operation.
It falls within the operable range of the invention for
each gate to be aligned at a downward angle between 90 and 180
degrees from the plane of the influent gate housing wall.
However, the greater the angle, the greater the likelihood of
un-screened debris within the influent stream getting caught
on the gate. Therefore, preferably, the gates should be at a
downward angle greater than 90 degrees from the plane of the
influent gate housing wall. Optimally, the gates should be at
a downward angle between 120 and 135 degrees from the plane of
the influent gate housing wall.
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After flow velocities are reduced utilizing the influent
gates, the influent stream then flows through the basin in a
laminar fashion via an outwardly flared portion of the pre-
react zone, as described below. As the stream flows to the
bottom of the vertical riser portion of the influent gate
housing, the stream encounters the floor, or bottom fitting,
which is designed to stop downward flow velocities. This
bottom fitting is preferably placed at a level below the
lowest normal wastewater level in the basin (brought about by
normal hydraulic equalization of the entire basin). When the
influent flow reaches the surface of the wastewater, splashing
further reduces the influent flow velocity.
The bottom fitting is preferably a standard "T" fitting
affixed to the base of the vertical riser portion of the
influent gate housing. This "T" fitting is preferably of a
multi-port design, having two openings to direct the influent
flow in a lateral direction, however, it is within the
operable range of the invention to have more or less openings.
Alternatively, it is within the operable range of the
invention if there were no bottom "T" fitting affixed to the
bottom of the vertical riser portion of the influent gate
housing. In order to achieve downward flow velocity
reduction, a disc or platform may be supported above the floor
of the basin, preferably with a peg or some other support,
directly below the bottom opening of the influent gate
housing. In this alternative design form, flow behavior would
not change significantly. As discussed above, the influent
flow would travel through the vertical riser portion of the
influent gate housing, encountering the influent gates, which
create turbulent flow and reduce downward flow velocity. Upon
contact with the surface of the wastewater, which is above the
bottom exit of the influent gate housing, both splash energy
and the reversing action of the turbulent flow further reduce
CA 02592998 2007-07-10
downward flow velocity. As the flow continues downward after
contact with the surface, it encounters the disc or platform,
which then omni-directionally directs flow laterally, as
opposed to a "T" fitting, which directs flow laterally through
5 ports.
If no bottom fitting is utilized, then the base of the
vertical riser portion of the influent gate housing would
preferably have a 90 degree lip extending 360 degrees around
the bottom exit of the influent gate housing. This lip would
10 act as an upward ceiling to assist in directing the flow
laterally. It is within the operable range of the invention
to have no lip, but such a lip is preferred to enhance lateral
flow out of the influent gate housing. If there are multiple
influent gate housings within the pre-react zone director,
then the surface of the disc or platform preferably extends to
cover the entire opening area of the pre-react zone director.
It is within the operable range of the invention for the disc
or platform to be in any geometric shape, however, if only one
influent gate housing is utilized, it is preferable that the
disc or platform be the same shape as the base of the influent
gate housing. If multiple influent gate housings are utilized
within a single pre-react zone director, then the disc or
platform should preferably be the same shape as the base of
the pre-react zone director.
After the influent flow undergoes turbulent aeration and
velocity reduction in the influent gate housing, influent
velocity is reduced further and then directed via the pre-
react zone director into the main react zone of the basin for
treatment. The pre-react zone director is designed such that
one or more walls create a chamber that separates initial
influent flows from the rest of the influent within the basin.
This prevents the initial influent flow from mixing with and
disturbing the main react zone's settled biomass during the
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settle and decant phases of operation. This allows optimal
operation of the settled sludge blanket (biomass) as a natural
biolbgical filter.
The- pre-react zone director utilizes a flap at its base
to direct the flow in a laminar fashion into the main react
zone. As a result, disturbances of the settled sludge blanket
are minimized, thus creating a dense natural biological filter
(biomass), which absorbs biological nutrients and chemicals
from the influent sewage stream during the settle phases of
operation, and thus creating a superior supernatant for
decant. Furthermore, the downward and outward direction of
the influent allows increased contact between the influent and
resulting biomass, which in turn results in more nutrient and
chemical removal than previous systems.
It is within the operable range of the invention if the
pre-react zone director utilizes any geometric shape, however,
it should preferably be either rectangular, square,
triangular, or circular to facilitate installation of the
flap. The pre-react zone director is preferably affixed to
the- side of the main basin wall opposite the decanter, and
situated in the center of the main basin's width. It is
within the operable range of the invention if the pre-react
zone director is suspended in the basin via flotation devices
and anchored in some manner, however, it is preferable that
the pre-react zone director be affixed and mounted to the
basin wall for structural support and aesthetics. Optimally,
the pre-react zone director should be mounted on posts,
affixed to the basin wall opposite the decanter, in the middle
of the basin width, with the posts being affixed to either the
bottom or top of the basin. Where this optimal configuration
is difficult (such as with fiberglass basins, or basins in
which the wall opposite the decanter is curved or otherwise
irregularly shaped), it is then preferable to have the pre-
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react zone director affixed to the top of the basin, or
mounted on posts, which are affixed to the bottom of the
basin.
The pre-react zone director flap is an angled lip that
extends around the entire perimeter of the base of the pre-
react zone director. It is within the operable range of the
invention that the flap be aligned at an outward angle between
0 and 180 degrees from the plane of the pre-react zone
director wall. The flap should preferably be aligned at an
outward angle of greater than 90 degrees from the plane of the
pre-react zone director wall. Optimally, the flap should be
aligned at a down and outward angle of 120 to 135 degrees from
the plane of the pre-react zone director wall. This optimal
angle alignment allows for optimum laminar flow of the
influent into the main react zone.
It is within the operable range of the invention if the
leading edge of the flap where the flap is connected to the
base of the pre-react zone director is jagged or uneven.
However, the leading edge should preferably be square.
Optimally, the edge should be rounded to allow optimum laminar
flow of the influent, and decrease turbulent flow under the
flap. In addition to reducing turbulence and creating laminar
flows, the flap also adds structural strength to the pre-react
zone director. It has been found that other systems utilizing
a react zone need eventual replacement of the react zone walls
because those walls tend to fail after continuous flexing
caused by turbulent flow during the aeration phases of
operation. By reducing this turbulence, the flap reduces the
stresses on the pre-react zone director walls, and extends the
structural longevity of the pre-react zone director.
The pre-react zone director encloses the influent gate
housing(s) within the basin. Because it rests above the floor
of the basin, there is a submerged gap between the flap and
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the basin floor. This gap comprises the contact zone, where
the initial influent flow exits the pre-react zone director
and comes into contact with the settled sludge blanket within
the main react zone. It is within the operable range of the
invention if the pre-react zone director comprises a single
wall stretching the width of the basin, thereby creating a 180
degree enclosure of the influent gate housing. This thereby
creates a 180 degree contact zone, which is within the
operable range of the invention. The pre-react zone director
should preferably surround the influent gate housing with a
minimum of 270 degrees of enclosure, creating a preferred 270
degree contact zone. It is optimal for the pre-react zone
director to completely surround the influent gate housing with
a 360 degree enclosure, which allows for an optimal 360 degree
contact zone, and which makes optimum usage of the biological
filter in the settled sludge blanket.
This device eliminates the need for a separate clarifier,
aeration basin, and settling basin, as this invention combines
all these elements within one basin. The simplicity of this
invention thus eliminates the odors, maintenance, land
requirements, and other costs associated with other multi-
basin complex wastewater systems. Furthermore, aeration
basins for other technologies typically are larger than the
clarifiers associated with them. This invention allows the
basin to act as a unified clarifier and aeration basin during
the cyclic aeration cycle, thus achieving the clarification in
a basin that is the same size as the aeration basin. This
eliminates the need for separate basins, and substantially
reduces the need for sludge return lines, and their associated
costs.
Brief Description of Drawings
Fig. 1 is a side elevational cutaway view of a presently
preferred embodiment of the present invention.
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Fig. 2 is a schematic diagram of an alternative
embodiment of Fig. 1 and includes an optional platform or disk
at the base of the influent gate housing.
Fig. 3 is top plan view of the embodiment of Fig. 1.
Fig. 4 is a side elevational cutaway view of the influent
gate housing.
Fig. 5 is a partial side elevational view of the pre-
react zone director flap.
Fig. 6 is a top elevational view of the influent gate
housing and basin of the presently preferred embodiment of the
present invention.
Fig_ 7 is a top elevational view of the influent gate
housing and basin of the alternative embodiment of Fig. 2,
whereby the pre-react zone director surrounds 180 degrees
around the influent gate housing.
Fig. 8 is a side elevational cutaway view of a presently
preferred decanter according to the present invention.
Fig. 9 is an end elevational cutaway view of the decanter
of Fig. 8.
Best Modes for Carrying Out Invention
The presently preferred best modes for carrying out the
present invention are illustrated by way of example in Figs. 1
to 7.
Referring to Fig. 1, shown is a presently preferred
embodiment of the present invention. The invention comprises
the influent gate housing 20, influent gates 24, influent gate
bottom 30, and pre-react zone director 34 with flap 38, within
a single basin 42. The air diffusers 46, float tree 48,
decanter 50, and emergency overflow 52 are standard components
of a wastewater treatment basin, and it is well within the
skill of a person of ordinary skill in the art to select and
install these components.
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The influent gate housing 20 comprises a vertical riser
portion 21, an opening 22 at the top of the vertical riser
portion 21, influent gates 24, and an influent gate bottom 30.
Preferably, the components of the influent gate housing 20
5 should be made of any product that is non-corrosive in the
particular wastewater stream that is being treated, such as
PVC, fiberglass, lined (sealed) concrete, and stainless steel,
but is not limited to these materials. Preferably, the
vertical riser portion 21 of the influent gate housing 20 is a
10 cylindrical pipe. Because normal operations of influent
stream usually have an air pocket at the top of the vertical
riser portion 21, it is within the operable range of the
invention to have no opening 22. However, it is preferable to
have, at a minimum, a removable cover, that can be removed for
15 cleaning, maintenance, or inspection purposes. Optimally,
there should merely be an opening 22 for aeration, ease of
cleaning, and maintenance inspections (Fig. 4).
In normal operations, influent stream enters the basin
via the influent gate housing 20. The influent flow travels
vertically downward over the influent gates 24. The influent
gates 24 act as baffles within the vertical riser 21 and
create turbulence within the influent stream that aerates the
influent flow. The influent gates 24 preferably comprise non-
corrosive material that is appropriate for the particular
wastewater being treated, such as PVC, fiberglass, and
stainless steel, but is not limited to these materials.
Each influent gate 24 is preferably set at a downward
angle greater than 90 degrees from the plane of the influent
gate housing 20. Optimally, the influent gates 24 should be
at a downward angle between 120 and 135 degrees from the plane
of the influent gate housing 20 (Fig. 4). Each influent gate
24 is affixed to the vertical riser portion 21 of the influent
gate housing 20 as shown in Fig. 4. Preferably, each influent
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gate 24 is affixed by being placed in a slot within the
vertical riser 21, with each slot being sealed, preferably
with a rubber seal or glue (but not limited to such means) to
keep the influent gate 24 in place, and to prevent influent
from leaking outside the influent gate housing 20. Affixing
the influent gates 24 in such a manner allows the influent
gates 24 to be removed for replacement, or angle adjustment if
deemed necessary.
Preferably, each influent gate 24 will have a bulb or
bump 26 affixed to the end of the influent gate 24 that is on
the exterior side of the influent gate housing 20. This bulb
26 prevents the influent gate 24 from sliding into the
interior of the influent gate housing 20, and in conjunction
with said rubber seal or glue, holds the influent gate 24 in
place.
Alternatively, the influent gate 24 may be installed and
affixed to the influent gate housing 20 with a hinge and a
spring mechanism 28 may be affixed on the underside of the
influent gate 24, connected to the influent gate housing 20,
as shown in Fig. 4. This will allow the influent gate 24 to
open completely in the event that debris or some other
material becomes clogged within the vertical riser portion 21
of the influent gate housing 20.
Although the number of influent gates 24 installed within
the influent gate housing 20 may vary according to the needs
of the particular wastewater system, it is preferable to have
at least one influent gate 24 installed within the influent
gate housing 20. Although it is within the operable range of
the invention to have no influent gates 24, optimally, more
than one influent gate 24 should be installed to achieve the
best quality effluent. Preferably, each influent gate should
be placed in an alternating pattern, equally spaced apart and
extending at least halfway down the side of the vertical riser
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portion 21 of the influent gate housing 20, as shown in Figs.
1, 2 and 4. Optimally, the topmost influent gate 24 should be
positioned on the side of the vertical riser 21 opposite the
initial influent flow, as shown in Figs. 1 and 2. Each
influent gate 24 thereafter would preferably be placed in an
alternating pattern, equally spaced down the vertical riser
21.
In normal operations, after the influent flow travels
over the influent gates 24, the influent flow then exits the
vertical riser portion 21 of the influent gate housing 20.
Preferably, there is a influent gate housing bottom 30 affixed
to the bottom end of the vertical riser portion 21, preferably
comprising a multi-ported "T" pipe fitting, as shown in Fig.
1. Preferably, the "T" fitting should have two openings.
However, it is within the operable range of the invention to
have more or less openings, to accommodate the particular
wastewater system in operation.
Referring to Fig. 2, shown is an alternative embodiment
in which, instead of a "T" fitting, the influent gate housing
bottom has a 90 degree lateral lip extending at least
partially (but preferably completely) around the bottom edge
of the vertical riser portion 21 of the influent gate housing,
and a disc or platform 41 supported above the bottom of the
basin via a peg or some other vertical support affixed to the
bottom of the basin. Preferably, the surface of disc or
platform 41 should be co-extensive with the bottom opening of
the influent gate housing 20. Preferably, the shape of the
disc or platform 41 should be the same as the shape of the
bottom of the influent gate housing.
The pre-react zone director 34 comprises one or more
walls surrounding the influent gate housing 20 to create a
chamber that separates initial influent flows from the rest of
the flow within the basin 42, as shown in Figs. 1, 2, 6, and
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7. Preferably, the pre-react zone director is any geometric
shape that allows an outwardly directed flap 38 to be affixed
to the bottom edge of the pre-react zone director 34. Such
geometric shapes include a rectangular, square, triangular, or
circular shape, but is not limited to these shapes. It is
within the operable range of the invention if the pre-react
zone director 34 comprises a single wall stretching the width
of the basin, thereby creating a 180 degree enclosure of the
influent gate housing 20, as shown in Fig. 6. The pre-react
zone director 34 should preferably surround the influent gate
housing 20 with a minimum of 270 degrees of enclosure, as
shown in Fig. 3. It is optimal for the pre-react zone director
34 to completely surround the influent gate housing 20 with a
360 degree enclosure, as shown in Fig. 7.
The pre-react zone director 34 is preferably affixed to
the side of the main basin wall 43 opposite the decanter 50,
and situated in the center of the main basin wall's width. It
is within the operable range of the invention if the pre-react
zone director 34 is suspended in the basin 42 via flotation
devices and anchored in some manner, however, it is preferable
that the pre-react zone director 34 be affixed and mounted to
the basin wall 43. Optimally, the pre-react zone director 34
should be mounted on posts, affixed to the basin wall 43
opposite the decanter 50, in the middle of the basin wall's
width, with the posts being affixed to either the bottom or
top of the basin 42.
The pre-react zone director 34 preferably comprises a
flap 38, which is an angled lip that extends around the entire
perimeter of the base of the pre-react zone director 34, as
shown in Figs. 1, 2, and 3. It is within the operable range
of the invention that the flap 38 angled outwardly between 0
and 180 degrees from the plane of the pre-react zone director
34 wall. The flap 38 should preferably be angled outwardly
CA 02592998 2007-07-10
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greater than 90 degrees from the plane of the pre-react zone
director 34 wall. Optimally, the flap 38 should be aligned
downwardly and outwardly at 120 to 135 degrees from the plane
of the pre-react zone director 34 wall, as shown in Fig. B. .
It is within the operable range of the invention if the
leading edge 40 of the flap 38 is jagged or uneven. However,
the leading edge 40 should preferably be square. Optimally,
the leading edge 40 should be rounded. The trailing edge of
the flap 38 may comprise a straight edge, or a rounded edge.
The overall operation of the present invention will now
be described. The influent continuously flows into the
influent gate housing 20 and strikes the topmost of the gates
24. The velocity of the influent is reduced as it cascades
through the remaining gates 24 and reaches the bottom of the
influent gate housing 20. The influent meets the surface of
the wastewater before it reaches the bottom of the influent
gate housing, and its velocity is thereby further reduced.
The influent is then directed laterally by the influent gate
bottom 30 (or the platform or disk in an alternative
embodiment). The influent then travels downwardly through the
pre-react zone director 34 until it reaches the pre-react zone
director flap 38. The space between the bottom of the basin
42 and the pre-react zone director flap 38 is the contact
zone, and the influent is constrained by the pre-react zone
director flap (and other structural features of the invention)
to flow through the contact zone in a laminar fashion.
Because the influent flows laminarly, it avoids disturbing the
settling sludge blanket. Yet, because the influent flows
laterally, it is exposed to a large surface area of the
settling sludge blanket, and therefore exposed to a large
surface area of anaerobic activity of the sludge blanket.
Although the influent flows continuously, settling and
decanting proceed in a batch manner. Initially, the influent
CA 02592998 2007-07-10
is allowed to fill the basin 42, and the air diffusers 46 are
activated to aerate the influent. When the level of influent
reaches the normal high water level, as determined by the
float trees 48 (or any other control mechanism, such as a
5 timer), the air diffusers 46 are deactivated and a pump (not
shown) is activated to pump out the supernatant through the
decanter 50. It is preferable that the decanter 50 float on
the surface of the influent and draw supernatant from just
below the surface of the influent. The decanter 50 draws
10 supernatant until the normal low level of water is reached (or
some other event occurs, such as passage of a predetermined
time). The air diffusers 46 are preferably reactivated after
enough time has passed for microbiological processes to be
completed in the settled sludge blanket, and the cycle then
15 starts again. A typical cycle would be 2 hours of air
diffusers and 2 hours of settling and decanting.
Preferably the decanter 50 pumps out supernatant at a
rate just less than the rate at which the sludge and other
solids settle towards the bottom, so that the decanter 50
20 pumps out clear supernatant at the highest possible rate.
Because the pre-react zone director flap and other structures
of the invention cause the influent to flow into the main
react zone in a laminar fashion, there is minimal disturbance
to the settled sludge blanket, allowing it to act as a natural
biological filter.
Referring to Figs. 8 and 9, shown is a preferred
embodiment 50 of the decanter of the present invention. The
body 52 of the decanter houses an airtight bladder 54 that is
filled with air and used for flotation of the entire decanter
50. Both the bladder 54 and the body 52 of the decanter have
end-caps or seals 53. On the bottom of the body 52 are a
number of holes 68 to which check valve risers 56 and a
decanter pump riser 61 are attached and in fluid
CA 02592998 2007-07-10
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communication. Risers 56 and 61 are then secured to body 52
with a watertight seal over the holes 68 and (preferably) tack
glued to the bladder 54. A decanter pump or decanter arm is
attached to the decanter riser 61 at the decanter effluent
exit port 62. At the bottom of each of the check valve risers
56 is a ball check valve which includes a ball 64 set into a
check valve housing 63 above a supernatant intake port 66.
During operation of the decanter 50, the decanter pump will
provide a vacuum at the decanter effluent exit port 62, and
because body 52 is airtight, the supernatant will be drawn
through the intake ports 66, thus raising the balls 64 and
opening the ball check valves. The decanted supernatant will
then travel up the check valve risers 56 and out the riser
holes 60 and flow into the space 70 between the body of the
decanter 52 and the pipe bladder 54. The decanted supernatant
will then be drawn further to flow through holes 60 on the
decanter pump riser 61 and down through the decanter effluent
exit port 62, to be discharged as effluent.
WORKING EXAMPLE
Definitions:
1. AWL Alarm Water Level
2. ALPHA Surface tension factors
3. AOR Actual Oxygen Requirement
4. BWL Bottom Water Level
5. BETA Gas solubility factors
6. BOD-5 Biochemical Oxygen Demand
7. CSM Oxygen Saturation Coefficient
8. DecantTo pour gently so as to not disturb the
sediment.
9. DO Dissolved oxygen
10. Effluent Outgoing wastewater
11. F:M ratio Food to microorganism ratio
12. HWL High Water Level
CA 02592998 2007-07-10
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13. Influent Incoming wastewater
14. MLSS Mixed liquor suspended solids
15. MLVSS Mixed liquor volatile suspended solids
16. NH3-N Ammonia Nitrogen
17. P Phosphorous
18. SOR Standard Oxygen Requirement
19. THETA Water Temperature
20. TKN Total Kjeldahl Nitrogen
21. TSS: Total suspended solids
22. TWL Top Water Level
The following is a general overview of the design process
that has been used for designing plants.
The basic characteristics of the influent for the plant
must be determined. This includes amount of flow, strength,
and type of wastewater to be treated. The effluent
requirements for the plant must also be considered. There is
a balance between what is feasible with regards to basin
sizing, and the strength of wastewater. If it is determined
that the wastewater is of a relatively high strength, or
exceeds the necessary effluent parameter, it may be necessary
to utilize one of various pre-treatment processes. The
options are either to reduce the strength, or (possibly) size
the basin to accommodate the chemical imbalance and strength
of the BOD-5 loading. The primary design parameters are daily
flow, peak flow, BOD-5, TSS, P, NH3-N, and TKN, which are the
most common characteristics for which effluent is tested.
However, the primary design parameters are not limited to
these tests and may require more extensive testing depending
on the specific project.
The number of cycles required to accommodate the various
strengths of wastewater are determined next. Preferably,
between 4 to 6 cycles per day are provided to achieve a sludge
CA 02592998 2009-05-06
23
age of 30 to 70 days. The sludge yield is then adjusted by
applying the correct coefficient, which may be obtained from
almost any wastewater treatment design manual, such as
Wastewater Engineerinq, Treatment/Disposal/Reuse, Second
Edition, Metcalf & Eddy, Inc.; M. J. Hammer, Water and
Wastewater Technology, Second Edition; Wastewater Engineering,
Collection and Pumping of Wastewater, Metcalf & Eddy, Inc.; J.
W. Clark, W. Biessman, Jr., M. J. Hammer, Water Supply and
Pollution Control, Third edition; H. Morris, J. Wiggert,
Applied Hydraulics in Engineering, Second edition; E. F.
Brater & H. W. King, Handbook of Hydraulics, sixth edition; J.
A. Roberson & C. T. Crowe, Engineering Fluid Mechanics, second
edition; M. R. Lindeburg, Civil Engineering Reference Manual,
4th edition; M. Henze, Wastewater Treatment, Biological and
Chemical Processes; and F. S. Merritt, Standard Handbook for
Civil Engineers, third edition. The sludge yield is a function of
the sludge age chosen. Sludge age affects the basin size and the
stability of the system as well as sludge production. The
volume required at BWL is basically a function of waste
removed and sludge age. Following recommended parameters for
sludge age and MLVSS will almost always result in a F:M ratio
between 0.05 and 0.10. Next, the minimum alkalinity required
for proper denitrification must be calculated so that it will
be greater than 158 mg/1 with the minimum P required at almost
always 2.0 mg/l.
Basin geometry is calculated by the given property and
spatial requirements that are offered by the particular
project and site characteristics. Thus if the property is
small, it may require a vertical cylindrical tank versus a
horizontal cylindrical tank. Fiberglass tankage is often used
for pre-packaged plants or systems where aesthetics are
important. Additionally, horizontal cylindrical tankage
CA 02592998 2007-07-10
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provides the best mixing properties when using diffused air.
Various tank compositions such as steel, concrete, fiberglass,
lined earthen basins, or a combination of compositions are
reviewed and analyzed as required and determined by the owner,
and environmental conditions. Another option to assess is
retrofitting any existing tankage as it may offer an
economical solution to the existing wastewater treatment
plant. Other factors determining basin geometry are strength
of the organic loading, and the peak flow (which is preferably
assumed to be approximately twice the average daily flow)
during a 4-hour duration. In addition, another factor in
calculating the basin dimensions is the design MLVSS to which
the wastewater plant is to be designed. Where tank geometry
size or shape is not an issue, the design tankage should be
calculated to accommodate a MLVSS of 3,500 mg/l, which has
been found to be stable. Next, the invert depth of the
influent piping should be calculated, and the sidewall depth
(which is dependent upon the depth of the basin allowable in
such a setting or environment) also should be calculated. The
Bottom Water Level, High Water Level, and Top Water Level are
then calculated based on the amount of volume required to
accommodate the flow and strength of wastewater. This amount
then determines the length and width of the wastewater
treatment plant based on the overall geometry used in the
particular tank design.
Proper mixing is determined by the depth of the
wastewater in relation to the type of aeration utilized. The
detention time at the Bottom Water Level, the amount of sludge
storage, and the sludge production (preferably at 8,500 mg/1)
are then calculated. The top height of the Pre-React Zone
Director is preferably determined by the top height of the
basin. The internal volume of the Pre-React Zone Director is
determined by the overall basin geometry, and preferably is
CA 02592998 2007-07-10
approximately 10% of the daily (or other) incoming influent
volume. The length to width ratio of the Pre-React Zone
Director is preferably approximately four to one for narrow
basin geometry, and three to two for larger basins. The Pre-
5 React Zone Director bottom height is calculated at a level
above the basin floor to accommodate the desired flow ratio
that one would desire. A flare or flap is preferably attached
extending downwardly approximately 120 degrees from the
vertical riser of the Pre-React Zone Director in all
10 directions. The unique feature of a flare or flap allows for
maximum laminar flow during the settle and decant phases of
operation, and maximum flow of influent through the settled
biomass (without stirring the biomass), while adding
structural integrity.
15 The Influent Gate Housing diameter is calculated to
accommodate the expected influent flow velocity (whether
pumped or gravity fed) and volume into the wastewater
treatment plant. The gates within the Influent Gate Housing
are situated and installed in such a fashion to create one or
20 multiple turbulence obstacles which the influent will pass
over. This reduces influent velocity, and creates incidental
aeration, which further reduces velocities by the natural
reversing of flow upon contact with the water level, usually
between the BWL and HWL. The gates are preferably angled
25 approximately 135 degrees downwardly from the vertical riser
of the housing. The number of gates is determined based on
the kind of installation required and the height to which the
influent must vertically drop to the BWL. Preferably, a base
or T fitting is provided under the bottom of the Influent Gate
Housing, which guides the influent to flow laterally.
Preferably, the bottom of the Influent Gate Housing is set at
approximately half of the Top Water Level, as determined
above.
CA 02592998 2009-05-06
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The amount of air that must be supplied to the system
must be calculated next. The goal of the air calculations is
to determine how much air must be delivered to the biomass.
AOR is the actual amount of physical oxygen uptake
biologically required. AOR is dependent on the amount of
waste being removed. SOR is the amount of oxygen that must be
delivered when adjusted for environmental conditions that
affect uptake. These conditions include elevation, THETA, the
wastewater medium (as opposed to pure water), ALPHA, and BETA.
ALPHA, BETA, THETA, and CSM (a function of wastewater
temperature) are obtained from reference tables readily
available in most publications, such as Design of Municipal
Wastewater Treatment Plants, WEF Manual of Practice. The physical
equipment required to deliver the SOR is a function of placement,
size, and efficiency factors.
Other considerations to be taken into account in the air
formulas include the operational DO level, time of aeration
and surface tension correction factor, solubility correction
factor, temperature correction factor, average water depth,
AOR and correction factor SOR, oxygen transfer per meter of
diffuser, oxygen transfer efficiency, air required for
biological removal (which determines brake HP required),
pressure, number of operating blowers, air per meter of
diffuser, and ultimately the number of diffusers. Redundancy
is very important; thus an additional standby blower is very
important in a wastewater treatment plant.
Decanter pump sizing is determined by dividing the
expected daily flow by the number of decant cycles desired per
day to find the volume of flow per decant cycle, and then
choosing the pump size necessary to pump that volume during
the pump portion of a decant cycle, preferably with a
redundancy added for maintenance. The effluent flow,
CA 02592998 2007-07-10
27
velocity, and head loss incurred is another factor in decanter
and pump sizing.
Preferably, a novel floating decanter is used that
requires little to no maintenance because it is made of non
corrosive materials (such as PVC). It decants supernatant
from just below the surface and therefore does not decant
floating solids or scum. It does not have any chain adjusting
mechanisms or mechanical arm, is non-mechanical, contains no
springs, has a PVC flotation bladder that does not require
replacement but is not limited to such. It has recessed check
valves that are not exposed to horizontal hydraulic and
aeration turbulence found with other decanters. An advantage
of having recessed check valves is that a small stationary
bubble forms around the decanter port during the aeration
phase of operation causing other bubbles to deflect away from
the decanter port and avoid hitting the ball in the check
valve, so that the check valve remains undisturbed and does
not allow solids ("mixed liquor") to pass through. This
allows the weight of the ball in the check valve to be
reduced, thus reducing the electrical load on the decanter
pump. This results in a superior supernatant. The check
valves are also preferably made of non-corrosive materials.
All components are readily available and the decanter is
easily manufactured. The decanter is usually designed using a
single row of decanter ports, but is not limited to such in
larger systems. Thus, in larger systems, two or more rows of
decanters can be connected together using simple "T" fittings,
reducers, and cross fittings. In order to calculate the
number of ports required for a decanter: calculate the
buoyancy of the ball-check-valves by utilizing sphere
diameter, sphere weight, and the specific weight of water.
Calculate the minimum pressure to lift the ball, buoyancy and
weight to determine the force required to lift the ball. Use
CA 02592998 2007-07-10
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expected flow, head loss, port sizes, and velocity to
determine the number of ports at a maximum flow velocity of
approximately 1-1/2 meters (5 feet) per second by each port.
This decanter's maintenance free characteristics allow the
owner or buyer to save capital, energy, and maintenance costs.
Preferably, the discharge line for the decanter extends
through the wall of the basin and is located just below the
Bottom Water Level or (BWL).
Emergency gravity overflow is provided, sized, and
calculated per the influent flow. The emergency gravity
overflow is usually situated on the basin opposite the
influent flow at a depth lower than the incoming influent
invert. Preferably, a standard "T" fitting is attached to the
overflow pipe with a downward extension of approximately 1/3
to 2/3 meters (12 to 24 inches) so that floating solids will
not be gravity fed out the emergency gravity overflow. All
fittings for this emergency gravity overflow are preferably
"Y" fittings. It is advisable not to utilize 90-degree
fittings, as the emergency overflow may become restricted.
The type and amount of available electrical power must be
considered in finalizing all control, blower, and pump sizing.
Automation of the process is preferably provided by
various float switches in conjunction with a clock. The
clocks' primary purpose is to control the length and time of
the aeration, and decant cycles. The BWL is kept at a minimum
by the BWL float switch, which opens the decanter circuit
(thus deactivating the decanter pump) during the decant cycle
determined by the clock when the minimum level is met. Should
an abnormal condition exist, the HWL switch would open the
circuitry to the aeration cycle causing the aeration cycle to
cease and go into a settle phase. The TWL switch would then
close the decant circuit which bypasses the clock timer and
starts an early decant until the circuit is opened. Should
CA 02592998 2007-07-10
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the emergency condition continue, the level would then close a
AWL circuit causing selected conditions to occur such as a
horn, light etc. to notify the proper authority. If the
emergency condition should continue, the system would gravity
overflow until the situation is remedied.
While the present invention has been disclosed in
connection with the presently preferred embodiments described
herein, there are other embodiments within the skill of a
person of ordinary skill in the art that fall within the
spirit and scope of the invention as defined by the claims.
Because wastewater treatment plants vary in size and shape,
and because of the highly customizable nature of this
invention to fit the needs of a particular wastewater
treatment system, there exist many variations and
configurations of the presently preferred embodiments
described above.
For example, there may be multiple influent gate
housings 20 encompassed within a single pre-react zone
director 34. Furthermore, multiple pre-react zone directors
34 may be utilized within a single basin 42.
The influent gate housing 20 may be in the shape of a
downward spiral or some other design.
The influent gate housing bottom 30 may utilize a base
that directs flows upward, downward, or other angle other than
horizontal.
The pre-react zone director 34 may utilize a manually or
automatically adjustable flap, or the pre-react zone director
itself may be manually or automatically adjustable to vary the
size of the contact zone by varying the height of the pre-
react zone director from the bottom of the basin 42.
The pre-react zone director 34 may utilize multiple
flaps.
CA 02592998 2007-07-10
This invention can be installed below ground if it is
vented and if freezing can be prevented.
Accordingly, no limitations are to be implied or inferred
in this invention except as specifically and explicitly set
5 forth in the claims.
Industrial Applicability
This invention can be used whenever it is desired to have
a secondary wastewater treatment system that achieves results
comparable to tertiary wastewater treatment systems. This
10 invention can be used whenever it is desired to utilize a
highly efficient, low cost wastewater treatment system that
produces high quality effluent on minimal land. This
invention can be used when currently existing systems are
inadequate or do not meet environmental standards or other
15 requirements. For example, if existing cesspools or septic
tanks are inadequate to accept additional wastewater, or if a
sewage infrastructure has not been connected to a particular
location, then this invention can be used to increase or
provide wastewater and sewage treatment.
