Title: Solids accumulating flotation separator
Abstract: The invention is directed to a method for flotation separation. The method has the steps of feeding an influent stream containing liquids and solids to a vessel, while removing clarified liquid at the same time as the feeding process. The method employs a step for emptying the solids from the vessel based on the solids having formed a float blanket of a predetermined depth. The solids are removed from the vessel through a bottom nozzle as opposed to being skimmed off the top surface with mechanical separators. The depth of the float blanket can be monitored. Once it is determined that the float blanket has reached the predetermined depth, the feed to the vessel is stopped and the vessel is emptied of liquids and solids through a suitable outlet other than the feed inlet, by an arrangement of valves and lines.
Patent Number: 6,893,572 Issued on 05/17/2005 to Burke
| Inventors:
|
Burke; Dennis A. (Olympia, WA)
|
| Assignee:
|
Western Environmental Engineering Company (Olympia, WA)
|
| Appl. No.:
|
194451 |
| Filed:
|
July 11, 2002 |
| Current U.S. Class: |
210/703; 210/221.2; 210/709; 210/744; 210/806 |
| Intern'l Class: |
C02F 001/24; C02F011/12 |
| Field of Search: |
210/703,709,744,806,221.2
|
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| 3870635 | Mar., 1975 | Clarke-Pounder.
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| 3966598 | Jun., 1976 | Ettelt.
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| 4022696 | May., 1977 | Krofta.
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| 4076515 | Feb., 1978 | Rickard.
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| 4079008 | Mar., 1978 | Neumann.
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| 4100066 | Jul., 1978 | Bloomer et al.
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| 4251361 | Feb., 1981 | Grimsley.
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| 4490248 | Dec., 1984 | Filippov et al.
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| 4510057 | Apr., 1985 | Rowe et al.
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| 4534862 | Aug., 1985 | Zlokarnik.
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| 4559146 | Dec., 1985 | Roets.
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| 4563274 | Jan., 1986 | Rothon et al.
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| 4564457 | Jan., 1986 | Cairo et al.
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| 4931175 | Jun., 1990 | Krofta.
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| 5080802 | Jan., 1992 | Cairo et al.
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| 5151177 | Sep., 1992 | Roshanravan et al.
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| 5156745 | Oct., 1992 | Cairo, Jr. et al.
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| 5310485 | May., 1994 | Roshanravan.
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| 5354458 | Oct., 1994 | Wang et al.
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| 5382358 | Jan., 1995 | Yeh.
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| 5437785 | Aug., 1995 | Roshanravan.
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| 5462669 | Oct., 1995 | Yeh.
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| 5538631 | Jul., 1996 | Yeh.
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| 5660718 | Aug., 1997 | Chudacek et al.
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| 5766484 | Jun., 1998 | Petit et al.
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| 5846413 | Dec., 1998 | Krofta.
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| 6126815 | Oct., 2000 | Kelada.
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| 6299774 | Oct., 2001 | Ainsworth et al.
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| 6464875 | Oct., 2002 | Woodruff.
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| 6569332 | May., 2003 | Ainsworth et al.
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| 6616844 | Sep., 2003 | Park et al.
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| 2001/0020603 | Sep., 2001 | Moorehead et al.
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| 2003/0141244 | Jul., 2003 | Hansen et al.
| |
| Foreign Patent Documents |
| 2058735 | Apr., 1981 | GB.
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| 60-064684 | Apr., 1985 | JP.
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| 6-71293 | Mar., 1994 | JP.
| |
Primary Examiner: Lithgow; Thomas M.
Attorney, Agent or Firm: Christensen O'Connor Johnson Kindness PLLC
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit of provisional U.S. Application No. 60/305,222,
filed Jul. 12, 2001, the disclosure of which is fully incorporated herein by reference.
Claims
1. A method of flotation separation, comprising:
feeding solids and liquids to a vessel while removing a clarified liquid stream
from the vessel;
allowing solids to accumulate into a float blanket; and
emptying the accumulated float blanket solids from the vessel lower portion based
on the solids having formed a float blanket of a predetermined depth.
2. The method of claim 1, further comprising:
monitoring the interface of the float blanket during the feeding step.
3. The method of claim 1, further comprising:
monitoring the depth of the float blanket during the feeding step.
4. The method of claim 1, further comprising:
stopping feed after the float blanket reaches the predetermined depth.
5. The method of claim 1, further comprising:
feeding solids to achieve a solids surface loading of greater than 50 lb/ft
2/day.
6. The method of claim 1, further comprising:
feeding solids to achieve a solids surface loading of greater than 100 lb/ft
2/day.
7. The method of claim 1, further comprising:
accumulating a float blanket depth of greater than 1 foot before emptying the
accumulated float blanket solids.
8. The method of claim 1, further comprising:
accumulating a float blanket depth of greater than 2 feet before emptying the
accumulated float blanket solids.
9. The method of claim 1, further comprising:
allowing the float blanket to accumulate based on a predetermined amount of time.
10. A method of flotation separation, comprising:
accumulating solids in a vessel after a float blanket mixture has been charged
to the vessel; and
emptying the accumulated float blanket solids from a vessel lower portion based
on the solids having formed a float blanket of predetermined depth.
11. A method of flotation separation, comprising:
re-flotating the solids collected from a mechanical flotation separator in a
vessel; and
emptying the re-floated solids based on the re-floated solids having formed a
float blanket of pre-determined depth.
12. A method of flotation separation, comprising:
feeding a solids/liquid stream to a vessel that empties at its periphery, while
removing a clarified liquid stream from a central lower portion of the vessel;
accumulating solids into a float blanket; and
emptying the vessel of accumulated float blanket solids from the vessel lower
portion based on the solids having formed a float blanket of a predetermined depth.
13. A method of flotation separation, comprising:
feeding a solids/liquid stream to a vessel that empties at its center, while
removing a clarified liquid stream from the periphery of the vessel;
accumulating solids into a float blanket; and
emptying the vessel of accumulated float blanket solids out of the vessel lower
portion based on the solids having formed a float blanket of a predetermined depth.
14. A method of flotation separation, comprising:
feeding a solids/liquid stream while removing a clarified liquid stream from
a first vessel;
accumulating solids in the first vessel;
emptying a second vessel of an accumulated float blanket from the second vessel
lower portion based on the solids having formed a float blanket of a predetermined
depth; and
filling a third vessel with clarified liquid, wherein the steps of feeding, emptying
and filling may be performed simultaneously.
Description
FIELD OF THE INVENTION
This invention is directed to solids separators, and more particularly, to a
flotation separator which does not include mechanical means for removing the float
blanket from the separator vessel but accumulates solids to form a float blanket
having a predetermined depth.
BACKGROUND OF THE INVENTION
There is a need for a simple, inexpensive high rate liquid/solid separation
apparatus and method to abate pollution from agriculture and urban point and non-point
sources. A large number of liquid/solid separation techniques are used in the wastewater
treatment industry. In the selection of a suitable separation apparatus and method
for a given application, the surface-loading rate of the system is often important
to the design. The surface-loading rate is generally reported in gallons per square
foot per day (gal/ft
2/day) for dilute flows or in pounds of dry solids
per square foot per day (lb/ft
2/day) for concentrated flows (suspended
solids >0.1%). Hydraulic loads are important to the design of the separator
when, for instance, turbulence inhibits the necessary separating action. If solids
removal is important, then solids loading should be the design criteria. Most conventional
flotation separators are desired to have high solids surface loading capacity,
yet are unable to achieve this for reasons which will be explained below. A separation
process is also selected based on its ability to remove a wide variety of pollutants
such as oil and grease, bacteria, colloidal, and suspended solids.
Separation using principles of buoyancy (i.e., flotation separation) is
advantageous because it achieves high capture rates while producing a clean effluent.
Flotation separation can also concentrate the waste (or recycle) solids. Concentrated
waste streams are desirable to minimize the size of downstream processing facilities.
Flotation separation has also been successfully used for the efficient removal
of suspended solids, colloids, oil and grease (O&G), nutrients, bacteria, organic
acids, algae, cryptosporidium, etc.
Conventional flotation separation, however, is considered a complex
process, involving gas saturation and injection accompanied by both surface and
bottom solids removal apparatus. Recently, the development of an efficient, yet
simple, saturator pump has reduced the complexity of the process. However, where
the influent waste stream results in a low solids loading rate (<50 lb/ft
2/day),
the vessel needed to carry out acceptable flotation separation tends to be excessively large.
The maximum hydraulic loading design rate for typical flotation separators is
about 5,760 gal/ft
2/day (4 gpm/ft
2). In actual practice,
the flotation separation process may, however, be limited by its solids surface
loading rate if the solids concentration of the influent stream is high. This is
especially true if the process is used for thickening as opposed to clarification.
Thickening refers to concentrating solids to a smaller volume, where clarification
generally refers to removing solids. The maximum solids loading rate for conventional
flotation separation methods is about 50 lb/ft
2/day. Thus, according
to FIG. 1, at the maximum design hydraulic loading, the allowable concentration
of solids of a typical flotation separator is about 0.1%. However, in actuality,
the solids concentration may be much higher, and consequently the typical flotation
separator is operating below its maximum hydraulic load. Thus, in almost all circumstances,
typical flotation separators are designed and operated to achieve their maximum
solids surface load capacity of about 50 lb/ft
2/day.
Maximizing the float solids concentration is advantageous since the solids
concentration will determine downstream processing resources and cost. If the solids
produced are dilute, the downstream dewatering or disposal costs will increase.
If the separator is used in a biological process incorporating solids recycle,
the processing cost and reactor size will be much greater if dilute solids are
produced. FIG. 2 shows how the processing costs increase as the separator's concentration
efficiency decreases.
It is desirable to improve the existing flotation separators because the advantages
of flotation separation as a method for concentrating waste streams are numerous.
Flotation separation can be used for both clarification and thickening. Flotation
separation can remove suspended solids, colloids, and oil and grease at the same
time. If reagents are added to the flotation stream, nutrients can be removed and
consolidated with the solids. If polymers are used, bacteria and a variety of other
organisms will be removed. If air is used, the effluent liquid will be aerated.
If gas is used, a variety of physical and chemical processes can be implemented.
Flotation takes advantage of the hydrophobic interactions that are lacking in other
separation technologies.
One attempt to improve flotation separation is proposed in U.S. Pat. No. 6,126,815,
to Kelada. Kelada discloses a zero pool velocity flotation separation process and
separator vessel. The vessel according to Kelada has a single nozzle for receiving
the waste fluid and solids, and for discharging the solids float blanket. In other
words, Kelada charges the separator vessel with an amount of liquid waste containing
solids. The initial charge is allowed to consolidate for a set period during which
no other streams are introduced into the vessel or removed from the vessel. During
the consolidation period, the solids rise to the surface and form a blanket of
solids. Depending on the amount of consolidation time, the density of the blanket
of solids can vary. However, since waste liquids are shut off after one tank volume
is charged into the separator vessel, the maximum amount of solids that can be
removed is predetermined and cannot exceed that which was initially charged into
the separator vessel. As such, the surface loading (lb/ft
2/days) capabilities
achieved by this apparatus are low.
It is desirable to produce a flotation separator apparatus and method capable
of increasing the solids surface loading capabilities beyond what is presently
accepted as the maximum. Such an apparatus would have a smaller footprint than
conventional flotation separator vessels, thus making it highly economical. The
apparatus disclosed herein fulfills such needs.
SUMMARY OF THE INVENTION
One embodiment of the invention is directed to a method for flotation separation.
The method has the steps of feeding an influent stream containing liquids and solids
to a vessel, while removing clarified liquid at the same time that the feeding
process is being conducted. The method employs a step for emptying the solids from
the vessel based on the solids having formed a float blanket of a predetermined
depth. The solids are removed from the vessel through a bottom nozzle as opposed
to being skimmed off the top surface with mechanical collectors. Conventional separators
use overflow weirs or scrapers to remove the float blanket. In one embodiment of
the invention, the depth of the float blanket can be monitored. The float blanket
is allowed to accumulate to a predetermined depth. Once it is determined that the
float blanket has reached the predetermined depth, for example, by activating a
high level switch, the feed to the vessel is stopped and the vessel is emptied
of liquids and solids through a suitable bottom outlet other than the feed inlet
by an arrangement of valves and lines. The valves can be automated to simplify
the emptying process based on input from level monitoring devices, turbidity meters,
optical sensors, optical reflectors, density meters and the like.
In another embodiment of the invention, a flotation separator apparatus is disclosed.
The flotation separator apparatus has a vessel used for accumulating a float blanket
without any surface or bottom collectors. The apparatus also has means for monitoring
the depth of the float blanket. The means for monitoring the float blanket can
include an interface transmitter, a level transmitter, a level switch, or like
devices. In one embodiment, the apparatus includes means for monitoring the interface
of a float blanket and means for signaling that the float blanket has reached a
predetermined depth. When the float blanket reaches a predetermined depth by activating
an electrical instrument, certain processes are initiated, including stopping feed
to the vessel.
The apparatus according to the invention accumulates solids to form a float blanket
until a predetermined depth is reached before removing the solids from the vessel.
Previous flotation separation systems failed to recognize the importance of continuous
accumulation of float solids to reach a certain depth. In one embodiment of the
invention, the float blanket depth is a factor in determining when to remove the
solids. Higher depth float blankets mean more concentrated solids because of the
greater weight placed on the float blanket. Conventional flotation separators remove
solids based on mechanical constraints, such as the speed of collectors, weir heights,
scraper height, etc. It has been found that removing these constraints, as is provided
for in the apparatus according to the invention, results in much higher solids
surface loading capabilities. The recognition of problems with conventional apparatus
has led the inventor to develop the newer apparatus and methods described herein.
In another embodiment, any number of flotation separator apparatus according
to
the invention can be combined in a system, so as to provide substantially continuous
influent waste stream processing. For example, one flotation separator in a group
of separators can be accumulating solids while the other separators are in different
modes such as filling or emptying. When the solids have accumulated into a float
blanket having a predetermined depth in one vessel, the waste stream can be directed
to a different separator, and the previous separator can be emptied.
One embodiment of an apparatus of the invention is a continuous flow-through
solids flotation separator. The solids are allowed to accumulate in the separator
while receiving waste in one or more inlet and discharging clarified liquid effluent
via a separate and distinct outlet, thus, accumulating solids and achieving a blanket
depth which has heretofore not been considered to be important. Accordingly, the
separator vessel has an inlet for the solid/liquid waste and an outlet for the
clarified liquid effluent and clarified liquid to the saturator, thus achieving
a flow-through solids flotation separator. The inlet and outlet are apart from
one another. The inlet and outlet are spaced away from each other so as to minimize
the possibility that solids from the inlet will flow to the outlet, thus not providing
the opportunity for solids to be captured in the float blanket. To this end, in
one embodiment, the separator vessel has an inlet in the center lower portion of
the vessel and an outlet at the periphery of the vessel. In another embodiment,
the separator vessel has an inlet at the periphery of the vessel and an outlet
at the central lower portion of the vessel. The accumulated solids float blanket
may be removed from the central portion of the vessel. The surface loading of the
solids flotation separator can be increased as compared with conventional flotation
separators. The area footprint of the solids flotation separator according to the
invention is dramatically reduced over what conventional flotation separators require
to process the same amount of solids surface loading.
The surface loading rates of the separator apparatus can be increased from the
conventional 50 lb/ft
2/day. In some instances, up to 200 lb/ft
2/day
or more. These rates are considerably greater than the rates for other separation
techniques. However, the separator apparatus can operate at any rate.
The separator apparatus according to the invention will have a wide variety of
applications. Their use may range to the removal of solids and phosphorus from
the effluent of small wastewater treatment facilities or lagoons. For example,
in Washington, Oregon, and Idaho, the removal of phosphorous from both municipal
and industrial treatment facilities is expected to soon be mandatory. An economical
method for precipitating and removing phosphorus colloids is required. The separator
will be a highly effective method of removing nutrients. The removal of nutrients,
oil and grease, and particulate matter from storm water is also a priority for
many facilities. In many cases, sufficient land is not available to install storm
treatment facilities.
One advantage of the separator apparatus of the invention is that it can reduce
by a factor of ½ to 5 the land footprint as compared with conventional separators
and thus, reduce the cost of separation. It also reduces the complexity associated
with most flotation separators. The operation and maintenance of the separator
apparatus according to the invention can be easily automated with the use of a
computer or programmable logic controllers. It is expected that the capital expenditures
and operating costs will be substantially reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and many of the attendant advantages of this invention
will become more readily appreciated as the same become better understood by reference
to the following detailed description, when taken in conjunction with the accompanying
drawings, wherein:
FIG. 1 shows a graphical illustration of the expected surface mass loading at
various influent solids concentrations for a hydraulic loading rate of 5760 gal/ft
2/day;
FIG. 2 shows a graphical representation of the benefit of achieving low thickening ratios;
FIG. 3 shows a schematic illustration of the float blanket removal process according
to conventional techniques;
FIG. 4 shows an illustration of an embodiment of a solids accumulating flotation
separator according to the present invention;
FIG. 5 shows an illustration of an embodiment of a solids accumulating flotation
separator according to the present invention;
FIG. 6 shows an illustration of an embodiment of a solids accumulating flotation
separator according to the present invention;
FIG. 7 shows an illustration of an embodiment of a solids re-flotation separator
according to the present invention;
FIG. 8 shows an illustration of an embodiment of a system of solids accumulating
flotation separators according to the present invention; and
FIG. 9 shows an illustration of an embodiment of a solids accumulating flotation
separator according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The flotation separation apparatus of the present invention is a simple and economical
flotation separator that will achieve high solids surface loading rates (small
footprint) and operates, in one embodiment, with a single motor driven saturator
device (exclusive of the influent, and effluent pumps, if required). The flotation
separator is suitable for any one of many applications, such as storm water, combined
sewer overflow, and wastewater treatment processes and the like. The flotation
separator of the present invention has no surface and bottom mechanical collectors,
yet has the following advantages. The flotation separator of the present invention
maximizes the float solids concentration (C
fs=pounds of dry solids per
cubic foot of float). The flotation separator of the present invention maximizes
solids capture in the float and thereby increases effluent clarity. The flotation
separator increases solids surface loading and thereby reduces the size and cost
of the separator. The flotation separator eliminates the complexity associated
with surface and bottom solids mechanical collectors.
Not intending to be bound by theory, the float blanket produced during flotation
separation in conformance with one embodiment of the invention are concentrated
by remaining on the surface of the water for a prolonged period of time. The flotation
process creates a mass of solids having a density less than water. The quantity
of gas entrapped in the mass establishes the float density. The solid mass acts
as an "iceberg" with a portion of the solids remaining out of the water. The lower
density resulting from entrapped gas within the solids blanket, determines the
mass protruding from the water's surface. The mass protruding from the water surface
drains and provides pressure on the float solids, thereby increasing the solids
concentration of the float blanket. A deep float blanket has more mass above the
liquid level, which places greater consolidation pressure on the float blanket.
The flotation separator according to the invention provides more time for the consolidation
and drainage to occur. The present separator apparatus allows accumulation of solids
for a prolonged period of time as compared to conventional flotation separators
that do not take accumulation into consideration.
High solids surface loading rates are contrary to the goal of obtaining high
float solids concentrations and effluent clarity in conventional flotation separators.
However, there is no limitation on the pounds of solids per square foot that can
be applied to a flotation separator of the present invention. Solids loadings of
greater than 50, 100, 150 and even 250 lb/ft
2/day have been applied
to a flotation separator made according to the invention. During trials to test
the concepts embodied herein, it was established that a conventional mechanical
flotation separator is limited by the rate of concentrated solids (float) removal
rather than the rate of solids delivery to the separator. The method and apparatus
according to the invention eliminates the mechanical collectors to thereby increase
the solids loading capacity.
The removal of float solids is directly related to the maximum surface-loading
rate. The solids removed can be expressed mathematically by the following expression:
Where:
P
R=Pounds of Dry Solids Removed (per day or hour)
A
FS=Area of Flotation Surface
D
FB=Depth of Flotation Blanket
Δ
SC=Number of Surface Cleanings (per day or hour)
γ
FB=Dry Solids Concentration of Flotation
Blanket (Pounds per cubic foot)
The surface loading is expressed as follows:
##EQU1##
As indicated, the surface loading is directly related to the depth of the flotation
blanket, the solids concentration of the blanket and the number of surface cleanings
performed per day, or hour. The dry solids concentration of the flotation blanket
is inversely related to the number of surface cleanings. In order to achieve a
dense float blanket, time is required for the float to consolidate. Consolidation
is achieved by allowing the float blanket to remain on the surface for the period
of time until a predetermined float blanket depth has been achieved. Frequent surface
cleanings as is typical of conventional mechanical flotation separators result
in less consolidation which produces lower solids concentrations. There are also
limitations to the maximum float depth that can be achieved utilizing existing
flotation separators with mechanical separators. Therefore, typical mechanical
flotation separators cannot simply be skimmed less often to increase the depth
of the float blanket.
Referring now to FIG. 3, a cross sectional schematic illustration of a
conventional mechanical top collector for a flotation separator is illustrated.
It is understood that only a portion of the mechanical separator is shown. Mechanical
removal of float blanket solids is undesirable because the float blanket depth
is not allowed to accumulate beyond the constraints of the mechanical system used
to remove it. The inventor theorizes that accumulating solids to a much greater
float blanket depth within a flotation separator vessel by continually feeding
the vessel with waste influent and continuous removal of clarified effluent will
produce positive results. As illustrated in FIG. 3, the mechanical collector of
conventional separators includes a series of scrapers
10. The scrapers
10
can be connected on an endless drive which continually moves the scrapers
10
along the upper portion of the vessel. The scrapers
10 move the float blanket
solids
20 along the surface in the direction of the arrows
30. The
scrapers
10 move the solids
20 along the surface and up the discharge
ramp
40 and over the edge. As the float blanket
20 hits the discharge
ramp
40, it must conform to the shape of the ramp
40. A portion of
the blanket
50 is pushed down below the original blanket
20 as a
displaced wedge. As a result of the ramp
40, the blanket
20 has twice
the depth due to the displacement of the portion of the blanket
50. Consequently,
the optimal float blanket depth is only half the height of the scrapers.
The depth of the solids blanket is a variable in conventional mechanical flotation
separators, meaning it is not a controlled variable. The scraper speed can, however,
be adjusted. If the blanket is not as deep as the scraper depth design, the scraper
will remove water with the solids, diluting the removed solids concentration. If
the blanket is deeper than the design of the scrapers
10, solids will be
pushed into the flotation unit as "fall-out" leading to poor solids capture. To
achieve high solids concentrations (no excess water) and high effluent clarity
(solids capture), the collector speed needs to be precisely controlled so that
the float blanket conforms to the scraper and discharge ramp design. Thus, for
any mechanical flotation separator, the float blanket depth is fixed.
It should be noted that the height of the scraper is twice the depth of the float
blanket. If the float blanket is one foot thick the scraper flight must be two
feet deep. Consequently, the maximum economical and feasible scraper height will
determine float blanket depth and as a result, the surface loading to the flotation
separator. For a variety of reasons surface collectors should not exceed two feet
in depth. The resulting blanket depth of conventional flotation separators is 1
foot and the surface loading is consequently less than 35 lb/ft
2/day.
According to one embodiment of the present invention, the float blanket
depth (D
FB) can, however, be increased. In some embodiments, the float
blanket depth is greater than 3 feet. In other embodiments, the float blanket depth
is 3 feet to 12 feet. Increasing the float blanket depth will increase the surface-loading
rate, increase the solids concentration and reduce the size of the flotation separator.
Accumulating solids within the separator apparatus vessel continuously until reaching
a predetermined float blanket depth and/or operating it as a sequencing batch reactor
can substantially increase the solids removal rate. For example, if one operated
a separation vessel with a cycle time equal to the solids clean time (Δ
SC)
and increased the hydraulic load to the unit four-fold, the accumulated blanket
depth would be four times the original depth, assuming the concentration remains
the same. Upon reaching the predetermined float blanket depth, the flow would be
transferred to another unit while the original unit would be emptied. The net effect
would be a surface loading twice the surface loading of conventional separators.
In one embodiment of the solids accumulating separator of the invention, the solids
surface loading is increased to the hydraulic loading limitations.
Referring now to FIG. 4, a solids accumulating flotation separator apparatus
100 according the present invention is illustrated. The flotation separator
uses no float or bottom collectors. Consequently, the separator
100 is simple
in construction and operation. The separator
100 is a vessel having a conical
shaped bottom portion
102 or hopper connected to a cylindrical body used
to accumulate solids into a float blanket. In one embodiment, the vessel
100
can have a dome
104 enclosing the vessel
100 at the upper end thereof.
A nozzle
106 is provided at the center of the conical portion
102.
Nozzle
106 is connected to an effluent line
126 which can be used
for the removal of stored liquid and accumulated solids, such as the float blanket
or settled solids.
The vessel
100 includes a contact chamber
108. In one embodiment,
the contact chamber
108 is provided within the interior of the vessel
100
at a central location thereof. One end of the contact chamber empties into the
interior of the vessel
100. The contact chamber
108 has a connection
for a waste stream line
110. Stream
110 can contain both liquids
and solids. Stream
110 contains the solids desired to be concentrated and/or
removed from the liquid. A second connection to the contact chamber
108
is made to a gas-saturated stream line
112. The stream
112 is clarified
liquid which has undergone a gas saturation process. A suitable pump for this process
is an EDUR DAF pump, model No. LBUX602E162L from the EDUR Company of Germany. The
waste stream and the gas-saturated stream mix in the contact chamber
108,
before being discharged into the separator vessel
100.
The vessel
100 further may include a distribution baffle
114. The
distribution baffle
114 is located opposite of the end of the contact chamber
108 which empties into the vessel
100. In this manner, the stream
leaving the contact chamber
108 impinges on the distribution baffle
114.
The distribution baffle
114 provides for the dissipation of energy and for
the more uniform radial distribution of the combined waste and gas-saturated steams
110 and
112, respectively, into the vessel
100.
The vessel
100 may further include an outlet ring
116. The outlet
ring
116 is defined by a shape which is best described as a hollow tube
which has been bent into a circle so that both ends meet. In one embodiment, the
outlet ring
116 can be interior of the vessel wall. In another embodiment,
the outlet ring
116 can be provided on the exterior of the vessel wall.
The outlet ring
116 includes a plurality of apertures
136 spaced
along the inner circumference of the ring
116. In this manner, the intake
of the clarified liquid is more evenly distributed from around the circumference
of the vessel
100. The outlet ring
116 may be located below the exit
of the contact chamber
108 to avoid the entrainment of solids. The outlet
ring
116 has an exit for the plurality of apertures. The outlet ring
116
is connected to saturator pump suction line
118 at the exit. Line
118
has a connection to the clarified liquid effluent line
122 before the saturator
pump
124. Clarified liquid effluent line
122 has a control valve
120 for controlling the level of the solids blanket interface. Alternatively
and/or additionally vessel
100 may include a clarified liquid effluent line
152 and control valve
154. Further description of the control scheme
of the separator apparatus is described in more detail below. Line
118 also
leads to the gas saturated stream line
112 via the saturator pump
124.
In this manner, clarified liquid is removed from the vessel
100, part is
removed from the system and part is recycled to the contact chamber
108
where it mixes with the incoming waste stream from line
110. The saturator
pump
124 mixes air or any other suitable gas with the recycled liquid for
the saturation of the liquid with the air or gas. Reagents may be added to the
saturator pump suction or discharge for the removal of nutrients or colloidal material.
Reagents may include inorganic salts of iron, aluminum, magnesium, calcium or organic polymer.
Bottom nozzle
106 is connected to a solids effluent line
126.
Solids effluent line
126 is arranged to deliver solids to a suitable location.
Solids effluent line
126 may also deliver liquids to a suitable location
via a "T" in the line to clarified liquid effluent line
122. Solids effluent
line
126 has a control valve
128 for controlling the emptying of
the vessel
100 at specific times. For example, when the float blanket reaches
a predetermined depth value
128 is activated to direct liquid and solids
emptying. The use of solids effluent line control valve
128 will be described
more fully below. Influent stream line
110 may also have a control valve
138 to control the desired amount of flow to the vessel
100 or to
completely shut off the flow to the vessel
100.
In one embodiment, the separator apparatus
100 includes an interface detector
130. The interface detector
130 is used, in one embodiment to monitor
the interface of the float blanket in vessel
100. The interface detector
130 can be any instrument suitable to detect a liquid/solids interface,
including an optical sensor. The vessel
100 may further include a plurality
of level transmitters or high and low level switches, all of conventional construction.
Such instrumentation may be used in the control of various parameters in the vessel,
such as the accumulated solids blanket depth or height above the interface, the
clarified liquid level, the emergency blocking of all valves and the stopping of
all pumps, for example. The separator vessel
100 is provided with instrumentation
for measuring the float blanket parameters and controlling the operation of the
vessel based on the accumulated float blanket depth.
In one embodiment, the separator apparatus
100 includes a three-way valve
134 located on the solids effluent line
126. The three-way valve
134 is configured to have one inlet which can be diverted to two outlets.
In one embodiment, the three-way valve
134 can be lined up to have the inlet
from the solids effluent line
126 lined up to flow into the clarified liquid
effluent line
122 downstream of the clarified liquid effluent control valve
120. In another embodiment, the solids effluent line
126 can be lined
up to a further processing section for the treatment of solids. The three-way valve
134 can be automated to switch from multiple settings by signals generated
from any of the aforementioned instruments.
In one embodiment, the separator apparatus
100 includes a turbidity meter
132 located at the bottom nozzle
106. Turbidity meter
132
is for measuring the turbidity of the material leaving the bottom nozzle
106.
Turbidity meter
132 can be used to indicate clarified liquid or solids-containing
liquids to direct the operation of the control valve
128, or to direct the
operation of the three-way valve
134.
In another embodiment, the separator apparatus
100 includes a flush cleaning
system
150 for cleaning the tank walls mixing chamber
108, effluent
ring
116, and the various control instruments.
In practice, one advantageous control scheme is in batch mode. Solids accumulate
until a float blanket of predetermined depth is achieved. In one embodiment, the
float blanket depth may be 3 feet or greater, or 3 feet to 12 feet. In one embodiment,
influent stream control valve
138, solids effluent line control valve
128,
and clarified liquid effluent control valve
120 are closed after having
filled the separator vessel
100 with clean water to the low level switch
140. Upon initiation of a storm flush, or any other event, a storm water
pump (not shown), begins pumping a waste stream to the separator apparatus
100
via line
110. Waste influent stream control valve
138 may be used
to control the flow of the incoming influent stream
110. However, in other
instances, influent stream control valve
138 may run wide open and is basically
operated as a block valve, either open or closed, but not as a throttle valve.
The influent stream with liquids and solids from line
110 leads to the contact
chamber
108. The saturator pump
124 starts operation and begins recycling
clarified liquid from the intake of the outlet ring
116 at the pump suction
or from another vessel. The pump
124 discharges into the line
112
connected to the contact chamber
108 where it mixes with the waste influent
stream
110 containing liquids and solids. Saturator pump
124 can
be started before, after, or substantially simultaneously with the opening of the
influent stream control valve
138. In one embodiment, the distribution baffle
114 deflects the discharge from the contact chamber
108 radially
in all directions of the separator vessel
100. Solids begin to accumulate
into a float blanket at the liquid surface. The float blanket accumulates above
the interface detector
130. In one embodiment, the interface detector
130
sends signals to control the clarified liquid effluent control valve
120
which maintains the bottom of the float blanket at the desired location by removing
clarified liquid from the separator vessel
100 at a rate sufficient to maintain
the bottom of the float blanket at the desired level. In another embodiment, the
control valve can control the liquid level in the vessel
100.
Solids will begin to accumulate within the separator vessel
100 until
the float blanket reaches the desired depth as illustrated in FIG. 5 by the instrument
142. This depth can be detected by any one of a plurality of instrumentation,
such as level transmitters, level switches, and the like, which indicate the proper
depth of the float blanket has been reached. Alternatively, the level of liquid
is maintained at a constant height, and the lower interface of the solids float
blanket can be monitored for the predetermined float blanket depth.
Once the float blanket has reached a predetermined depth, as measured by an
interface meter, low or high level switch, or a level transmitter or any other
suitable instrument, the control valve
138 can be completely closed. The
saturator
124 can alternately be shut down and the control valve
120
can be closed as well. The solids effluent control valve
128 is opened to
drain the separator
100. The liquid is discharged to either the clarified
liquid effluent line
122 or to the concentrated solids line
126 through
the operation of the three-way valve
134 controlled by the turbidity sensor
132 or timer. Once all liquid is drained from the vessel
100, the
float blanket solids are removed as illustrated in FIG.
6. The system can
then be cleaned by a variety of spray nozzles prior to filling in preparation for
the next cycle.
However, other embodiments can use different control schemes based on the
float blanket having reached a predetermined depth. In one particular embodiment,
once the float blanket reaches the predetermined depth, the influent stream control
valve
134 is closed.
In another embodiment, once the control valve
134 is closed, the clarified
liquid effluent control valve and the separator pump
124 can remain in operation.
Alternatively, the clarified liquid control valve and the separator pump
124
can be shut down.
In another embodiment, the clarified liquid effluent control valve
120
and the saturator pump
124 maintain operation to bring the float blanket
level down to the intakes of the outlet ring
116.
In another embodiment, the clarified liquid effluent control valve
120
and the saturator pump
124 are shut down when the influent stream control
valve
134 is closed.
In another embodiment, with the influent stream control valve
134 closed,
the solids effluent control valve
128 can be opened to remove any solids
which are denser than the liquid which accumulate at the bottom hopper section
122 of the separator vessel
100. The clarified liquid above the bottom
solids can be discharged to the clarified liquid effluent line
122 or to
the solids effluent line
126 by operation of the three-way valve
134.
The bottom solids can be discharged through a separate sewer system, storage tank,
or in the case of a combined sewer overflow, returned to the sewer line under low
flow conditions. The float blanket solids are also removed via the solids effluent
line
126.
Referring now to FIG. 7, a further embodiment of the present invention
is illustrated. The solids removal of conventional flotation separators having
mechanical scrapers of a predetermined height can be improved by re-floating the
solids in an additional vessel. The system
700 according to the present
invention utilizes a conventional flotation separator vessel
702. The conventional
flotation separator vessel
702 includes a mechanical scraper located at
the upper portion of the vessel
702. Mechanical scrapers are well-known
mechanical devices used in flotation separators. The flotation separator vessel
702 includes a discharge ramp
710. The float blanket
704 includes
a mixture of solids and liquid. As the scraper removes float blanket mixture up
the ramp
710, in addition to removing solids, entrained liquid is carried
up the ramp and into the re-flotation vessel
712. Therefore, there is a
need to re-float solids gathered from conventional floatation separators. Toward
that end, in one embodiment, according to the invention, an apparatus and method
for re-floating solids is provided. The system
700 includes a re-flotation
vessel
712 downstream of the solids ramp
710, so as to enable the
collection of solids
704 with any entrained liquid. The re-flotation vessel
712 includes a hopper with a cone or tapered bottom portion
714 connected
to a cylindrical portion
716 or standpipe. The conical portion
714
is connected to an outlet
718 at a low point in the tapered section
714.
The outlet
718 may be connected to the suction side of pump
720 or
simply discharged by gravity. The discharge of pump
720 is connected to
a three-way valve
722 having a single inlet and two outlets or a multiplicity
of valves having the same function. One outlet can be directed to a clarified liquid
line
724, while a second outlet can be directed to a solids line
726.
A turbidity meter located at the outlet line
718 can be used to control
the three-way valve
722 line-up position. An interface detector, or level
indicating instrument can be used to monitor the float blanket depth in the re-flotation
vessel
712.
In operation, the float blanket mixture deposited into re-flotation vessel
712
is allowed to reside within re-flotation vessel
712 for any length of time
in order to cause the separation of clarified liquids and the re-floated solids.
Alternatively, the float blanket accumulated in vessel
712 can be measured
and controlled, so as to empty the vessel
712, when the float blanket reaches
a predetermined depth. In this manner, the removed solids concentration is increased
as compared with the conventional flotation separator standing alone.
Re-flotation vessel
712 can be of any suitable height and diameter.
Re-flotation vessel
712 can be fitted with suitable instrumentation, such
as, but not limited to level meters, high and low level switches, interface detectors,
density meters, and the like to provide for the adequate monitoring of the processes
taking place within the re-flotation vessel
712. Additionally, any number
of pumps or valves and piping configuration can be utilized.
One or more re-flotation vessels
712 can be provided in parallel or in
series as required to provide for the continuous operation of the system.
In another embodiment, the separator can be operated to process a continuous
flow
as a sequencing batch reactor. Each separator can be filled with clean or process
