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Patent 2565052 Summary

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(12) Patent Application: (11) CA 2565052
(54) English Title: SYSTEM FOR IMPROVED DISSOLVED AIR FLOATATION WITH A BIOFILTER
(54) French Title: SYSTEME POUR FLOTTATION A L'AIR DISSOUS AMELIOREE AVEC BIOFILTRE
Status: Dead
Bibliographic Data
(51) International Patent Classification (IPC):
  • C02F 3/02 (2006.01)
  • C02F 9/14 (2006.01)
(72) Inventors :
  • JACKSON, DAVID (Canada)
(73) Owners :
  • JACKSON, DAVID (Canada)
(71) Applicants :
  • FLYNN WATER TECHNOLOGIES INC. (Canada)
(74) Agent: THOMSON, J. GORDON
(74) Associate agent:
(45) Issued:
(22) Filed Date: 2006-10-19
(41) Open to Public Inspection: 2008-04-19
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data: None

Abstracts

English Abstract




The system integrates dissolved air flotation (DAF) with a biologically active
filter (or
biofilter) to produce a treatment system. The DAF provides for effective
removal of most
particulates, whereas the biofilter enhances the removal of very fine
particulate not
efficiently removed by the DAF. The biofilter relies on the growth and
proliferation of
biofilm (attached colonies of micro-organisms) on a support media to effect
particulate
removal.


Claims

Note: Claims are shown in the official language in which they were submitted.




What is claimed is:


[Claim 1] A system for improved dissolved air floatation (DAF) treatment of
wastewater
wherein said system comprises: a controlled source of continuous wastewater
flow
containing unsettled secondary effluent containing a first size and a second
size of
particulate matter wherein said first size is larger than said second size; a
tank having a first

predetermined volume for receiving and containing a second predetermined
volume of said
wastewater for treatment and discharging a post-treatment stream; means for
capturing the
first size of the particulate matter for disposal comprising a DAF nozzle;
means for

capturing the second size of the particulate matter for disposal; and
cleansing means.

[Claim 2] The system of claim 1 wherein said means for capturing the second
size of
particulate matter is a biofilter and wherein said cleansing means is adapted
to periodically
cleanse said biofilter.


[Claim 3] The system of claim 2 wherein the second predetermined volume of the

wastewater in the tank is determined by a weir, wherein said weir receives
said post-
treatment stream and discharges the post-treatment stream into a system
discharge line.

[Claim 4] The system of claim 3 wherein the tank further comprises a
horizontal first
zone comprising said means for aerating the wastewater, a horizontal second
zone
comprising the biofilter disposed below said horizontal first zone, and a
horizontal third
zone disposed below said horizontal second zone wherein said first, second and
third zones
are in hydraulic communication.


[Claim 5] The system of claim 4 wherein the horizontal first zone and the
horizontal
second zone are separated by a first screen and wherein the horizontal second
zone and the
horizontal third zone are separated by a second screen.


Page 22



Claim 6] The system of claim 5 wherein the horizontal second and third zones
are
divided into at least first and second vertical and adjacent compartments so
that said at
least first and second vertical and adjacent compartments are non-
communicative and
operate independently.


[Claim 7] The system of claim 6 wherein the second horizontal zone of the at
least
first and second vertical compartments is divided into a primary upper layer
and a
secondary lower layer, said primary upper and secondary lower layers separated
by a
wastewater recycle withdrawal manifold disposed within the second horizontal
zone and
wherein the third zone of the at least first and second compartments comprises
a post-
treatment stream discharge manifold disposed above a secondary recycle flow
manifold.

[Claim 8] The system of claim 7 wherein said DAF nozzle comprises an aerating
nozzle assembly disposed centrally within the first horizontal zone and above
the second
horizontal zone.


[Claim 9] The system of claim 8 wherein said aerating nozzle assembly
communicates with a first conduit containing a supply of pressurized recycled
flow drawn
from said wastewater recycle withdrawal manifold and wherein said supply of
pressurized
recycle flow is in communication with a cavitating air injector for entraining
dissolved air
into said supply of pressurized recycle flow.


[Claim 10] The system of claim 9 wherein said first conduit is sized to
promote air
dissolution within the supply of pressurized recycled flow and to achieve a
"froth flow" mass
transfer regime and wherein the first conduit terminates at the bottom end of
a third
vertical conduit and further wherein said third vertical conduit top end
comprises a
discharge nozzle having a discharge aperture.


[Claim 11] The system of claim 10 wherein the aerating nozzle assembly
communicates with a second conduit in communication with a supply of
pressurized feed

Page 23



flow containing particulate matter of a first size and wherein said second
conduit comprises
a horizontal section terminating in a vertical section, wherein said vertical
section has an
inside wall, a closed first end and an open second end.


[Claim 12] The system of claim 11 wherein the third vertical conduit is
disposed within
the vertical section of the second conduit thereby forming an annulus.


[Claim 13] The system of claim 12 further comprising an impingement plate
disposed
an adjustable distance above said discharge aperture thereby forming an
adjustable gap
between the discharge aperture and said impingement plate so that the
pressurized
recycled flow discharged from the discharge aperture impinges upon the centre
of the
impingement plate with pressurized feed flow discharged from said open end of
the second
conduit.


[Claim 14] The system of claim 13 wherein the pressurized recycled flow
discharged
from the discharge aperture experiences a pressure drop within said adjustable
gap so that
air bubbles are formed therein.


[Claim 15] The system of claim 14 wherein the flow of pressurized feed
containing
first sized particular matter that is discharged out of the open end of the
second conduit is
in sufficiently close dynamic proximity to said air bubbles in the pressurized
recycled flow
discharged from the discharge aperture so that the first size of the
particulate matter
attaches to the air bubbles and floats to the top of said horizontal first
zone the result
being the formation of a float layer for later harvesting.


[Claim 16] The system of claim 15 wherein said biofilter comprises a plurality
of
dynamic biomass carriers disposed and circulating within the horizontal second
zone and
adapted to promote the growth of micro-organisms there upon.


[Claim 17] The system of claim 16 wherein each biomass carrier of said
plurality of
dynamic biomass carriers are separated by an intra-carrier flow channel having
a first size.

Page 24



[Claim 18] The system of claim 17 wherein each biomass carrier of the
plurality of
biomass carriers has a specific gravity greater than one and comprises a
plurality of
surfaces disposed a predetermined distance apart for optimized growth of
biomass and
wherein said plurality of surfaces are arranged to create a plurality of inter-
carrier flow
channels.


[Claim 19] The system of claim 18 wherein cleansing means comprises means for
isolating the biofilter, means for introducing air into the biofilter to
agitate the biomass
carriers so that excessive biomass is shed; and, means for transporting said
shed biomass
to the first horizontal zone.


[Claim 20] The system of claim 19 further comprising a final filter located on
the
system discharge line.


Page 25

Description

Note: Descriptions are shown in the official language in which they were submitted.



CA 02565052 2006-10-19

System for Improved Dissolved Air Flotation with a Biofilter
DESCRIPTION
[Para 1] Field of the Invention

[Para 2] This invention relates to the treatment of wastewater using a
biological process
and more particularly to a system for improved dissolved air flotation with a
biofilter.

[Para 3] Background of the Invention

[Para 4] Dissolved Air Flotation (DAF) systems are commonly employed for the
removal
of suspended solids from water. However, the efficiency of removal generally
declines with
decreasing particle size. Ten (10) um is commonly regarded as a lower limit
for efficient
removal with this process. Water and wastewater can commonly contain many
particles
smaller than this threshold, for example, colloid particles. There is often a
need to remove
these fine particles. Chemicals called coagulants and flocculants are often
used in
conjunction with a solids removal process such as sedimentation or DAF for
increased
removal efficiency of these particles. These chemicals are costly and their
use can be
operationally complex. Fine filtration may also be used (with or without
coagulants and
flocculants) to remove the fine particles not removable by settling or
flotation alone.

[Para 5] The two most common types of filters employed for fine filtration of
wastewater
are granular media filtration and membrane filtration. Both of these processes
are primarily
physical filters where the pore size of the filter determines the minimum size
of particulate
removed. Both types can have relatively high operating cost because the
granular media

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CA 02565052 2006-10-19

filters need vigorous backwashing for cleaning; the membrane filters need
liquid turbulence
and/or "scour" air to retard membrane fouling; they also require periodic
chemical cleaning
procedures.

[Para 6] Biofilms are known to be effective for the removal of fine
particulate in water.
Mechanisms include passive interception of particles, adsorption of particles
to biofilm and
ingestion (grazing) activities of certain microorganisms such as sessile
ciliates that utilize
the particulate as a food source. The sessile ciliates are particularly
important because of
their ability to sweep particles from their vicinity and ingest them. It is
known that the water
vortices generated by ciliate feeding activity can extend up to 400 um from
the organism
itself. This has the effect of disturbing the liquid boundary layer around the
organism and
making particles outside the boundary layer available for capture. Ciliates
often occupy
biofilm protrusions that can extend 1 mm above the surface of the basal
biofilm. Given that
biofilms can often be 500 nm or more in thickness, it can be readily seen that
a ciliate-rich
biofilm can exert a cleaning effect 2mm or more from the biofilm substrate.

[Para 7] To date some commercial use of biofilm filtration exists using
granulated
activated carbon media. However these filters act principally as physical
filters and require
conventional backwashing. They typically receive a wide range of particles,
rather than
micron and sub-micron particles. No attempt is made to optimize conditions for
the
performance of sessile ciliates for removal of fine particles. Therefore there
is a continued
need to improve water and wastewater treatment processes and apparatus by a
more
effective means of using sessile ciliates in biofilm filtration.

[Para 8] Summary of the Invention

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CA 02565052 2006-10-19

[Para 9] The invention provides advanced treatment of unsettled secondary
effluent in a
single unit operation. This includes gross solids removal, biological
oxidation of residual
organic matter and removal of fine (including submicron) particulates. The
invention
comprises a novel combination of dissolved air flotation (DAF) to remove fine
particulates
from wastewater and a biofilter specifically designed to maximize the
particulate removal
performance of naturally occurring microbiological flora particularly sessile
ciliates. The
result is a novel and inventive wastewater treatment system having cost and
performance
advantages over existing systems commonly used for such purposes. The DAF
provides for
effective removal of most particulates. The biofilter enhances the removal of
very fine
particulate not efficiently removed by the DAF. The biofilter relies on the
growth and
proliferation of biofilm comprising colonies of micro-organisms attached to a
support
media or biomass carriers for particulate removal. The present invention
provides optimized
conditions for the proliferation and performance of sessile ciliates and
similar organisms
that have superior capabilities for the capture of fine particulate organic
matter such as
colloids. The invention requires periodic harvesting of biofilm. In the
embodiments
described herein, the invention provides a convenient method for removal of
the biofilm
flocs formed in the cleaning operation.

[Para 10] The invention comprises a vessel or tank capable of containing
water. The tank
receives feed flow in the form of unsettled secondary effluent. The feed flow
enters the top
of the tank by way of a feed conduit and discharges purified water from the
bottom of the
tank by way of a discharge conduit. The discharge conduit is in communication
with a weir
assembly. The tank is maintained full of water to a level determined by the
weir so that it
does not overflow.

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CA 02565052 2006-10-19

[Para 11] The tank is divided into two zones. The upper zone is called the DAF
zone,
wherein recirculated water is aerated and mixed with new feed flow in a DAF
nozzle
assembly. The DAF nozzle assembly generates small air bubbles that contact and
adsorb
particulate matter in the feed flow and DAF zone and float these solids to the
surface where
they collect as a "DAF float". The DAF float contains a significant amount of
particulate
matter by weight and is removed from the top of the tank by a skimming
mechanism.

[Para 12] The bottom of the DAF zone is marked by a first media screen with a
large
percentage of open area (at least 60%) but with apertures small enough to
prevent upward
passage of any biocarriers from an adjacent and lower zone called the
biofilter zone. The
DAF may optionally include a particle interception layer consisting of a
"plate pack" of
inclined plates or other media (common to DAF and clarifier design in the
industry). These
are designed to stabilize and regularize velocities, encourage laminar flow
and increase
particulate removal efficiency.

[Para 13] The biofilter zone is divided by a watertight bulkhead(s) into two
or more side
by side compartments each containing plastic biofilm support media called
"biomass
carriers". Each compartment is further divided into upper (primary) and lower
(secondary)
layers. Under normal operating conditions the water leaving the DAF zone
(including both
feed water and all recycle flow) traverses the primary layers of both
compartments on its
way through the system.

[Para 14] A substantial potion of the water traversing the primary layers of
the
compartments is withdrawn and recycled back to the DAF zone through a process
described
Page 4 of 30


CA 02565052 2006-10-19

herein. The balance of the water traverses the secondary iayers of the
compartments. The
bottom of the compartments is delineated by a second media screen similar to
the first
media screen adapted to prevent the passage of biomass carriers. Water
traversing the
secondary layers of the compartments leaves the tank through a set of
manifolds located
below the second screen. Another set of manifolds is located at the bottom of
the
compartments and is employed in the cleaning cycle.

[Para 15] The biomass carriers are randomly packed discrete plastic elements
having
shapes, internal structures and large surface areas that promote biofilm
growth and ensure
intimate contact between the water and biofilm. These carriers preferably have
a specific
gravity greater than 1.0 so that they settle on the lower screen leaving a
clear space of
several cm between the top of the media layer and the upper screen. All water
entering the
DAF zone from the DAF nozzle assembly, feed flow and recycled water is
compelled to
traverse the biomedia where a variety of processes contribute to the treatment
and
clarification of the water as described herein.

[Para 161 The primary recycle flow is drawn from a set of manifolds into a
continuously
operating pump. The pump is a high-head, low flow type centrifugal pump. A
cavitating air
injector or venturi designed for air suction and liquid motive flow injects
air into the
discharge of the pump. The cavitating nature of the venturi implies that
within the normal
operating range, back pressure on the outlet side of the venturi affects the
degree of air
suction but does not substantially affect the liquid flow rate. Conversely,
imposed changes
in air flow rate do not affect the liquid flow rate. The pump and venturi must
be very
carefully selected for compatible operation and to meet required targets for
water and air

Page 5 of 30


CA 02565052 2006-10-19

flow rate as well as pressures. A valve and flow meter are provided for
monitoring and
control of air flow.

[Para 17] Air is immediately mixed with water in the venturi, however
dissolution of air
within the venturi is incomplete. The venturi discharge mixture immediately
enters a very
precisely sized conduit designed to produce a specific two-phase flow regime
known in the
mass transfer engineering field as "bubble flow" or "froth flow" that most
efficiently
dissolves air in water. This approach requires a conduit having a smaller
diameter than is
typically used for DAF recycle lines. The conduit is typically small diameter
plastic tubing.
Consequently, the length of the line must be minimized while still ensuring
complete
dissolution of air in the liquid flow. If not, the pressure drop in the
conduit will severely
restrict dissolved air capacity and cause a deterioration of the bubble flow
regime within the
conduit.

[Para 18] The bubble flow from the venturi enters the DAF nozzle assembly and
is mixed
with fresh feed flow on an impingement plate suspended above the nozzle
assembly a
predetermined and adjustable distance. Bubble flow is discharged into the
impingement
plate through a calibrated discharge orifice and experiences a rapid drop in
pressure. The
flow is redirected in a uniform radial pattern from the impingement point
along the surface
of the plate to its edge. The consequence is that very small bubbles (with
rise times of 10
cm / min or less) are generated in immediate proximity to the fresh feed flow.
The
hydrodynamics of the DAF nozzle assembly are such that the feed water is
inducted into the
area between the orifice and the impingement plate creating intimate contact
between feed
water containing particulates and recycle flow with dense bubble formation.
This condition

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CA 02565052 2006-10-19

maximizes the potential for particulate attachment to the bubbles and
therefore enhances
DAF particulate removal efficiency.

[Para 19] The bubbles generated in the DAF nozzle assembly pervade the DAF
zone and
adsorb to or are physically entrapped by particles originating in the feed
water (or particles
already ambient in the DAF zone as in the aftermath of a cleaning cycle, as
described

below). This causes the captured solids to rise to the surface of the DAF zone
where they
gradually form a float layer. The float layer can grow to considerable
thickness (up to
several cm) and so must be harvested periodically and prior to every cleaning
event. In
operation with unsettled secondary effluent from a domestic source the float
layer becomes
more and more compact with time and rises above the water level. The result is
that the
upper portions of the float layer will have a solids content exceeding 15% dry
solids by
weight and the layer will have an average solids content exceeding 7%. The
surface of the
float layer gains a rubbery and elastic characteristic such that large
cohesive chunks of the
matter can be easily scooped off the surface of the DAF with minor loss of
matter to the
water phase. This progressive and natural dewatering of the float layer is an
advantageous
characteristic of the process. Removal of the float layer may be accomplished
by a variety
of established methods such as mechanical scraping or skimming. However, the
preferred
mechanism is a moving porous belt device that is immersed in the DAF zone at
one end and
rises above the DAF zone on the other side so that it will lift and pull the
float layer out of
the DAF and dewater it further while conveying it to a vessel located outside
of the DAF for
further dewatering and/or disposal. In the preferred configuration, the float
would drop
into a fabric dewatering bag where further removal of moisture occurs through
gravity
drainage as well as convective evaporation/drying possibly using forced air
from sources of
waste heat such as air blowers used in the secondary treatment process.
Alternatively, the

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CA 02565052 2006-10-19

bags can be removed after partial drying to an indoor or outdoor storage
facility where final
dryness may be achieved. Final disposal of the solid byproduct can be to a
land fill, land
farming site or composting facility depending on local facilities and
regulations.

[Para 20] Water traversing the secondary biofilter zones will equal (on
average) the feed
flow plus any water collected through the bottom manifolds and contributed to
secondary
recycle flow. This secondary recycle flow from the bottom manifolds can be
adjusted in
response to any need to optimize the variable of oxygen content, water
residence time and
channel velocities in the secondary biofilter layers. The secondary recycle
flow traverses a
supplementary aeration device before it is added to the feed flow so as to add
oxygen to the
system when required. In some situations there may be no need for a secondary
recycle
flow. In normal operation, water leaving the biofilter that is not drawn into
the recycle flow
will discharge through manifolds to the effluent weir and become final
effluent discharge
flow. The weir is an external horizontal weir that may be attached to a side
of the tank. It is
designed to minimize changes in the water level in the tank so that water does
not overflow
and the float layer is positioned vertically for efficient removal. Flow
equalization must be
accomplished prior to the DAF-Biofilter operation. An additional end filter
may be added to
further remove residual particulate matter from the effluent flow.

[Para 21 ] Biofilter Function and Cleaning Modes

[Para 22] The biofilters employed in this invention differ from conventional
biofilters in
several respects:

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CA 02565052 2006-10-19

o They are physically integrated with the DAF unit and occupy the same tank
(as described
above). This stacked configuration is particularly advantageous in space-
constrained sites;
o The media employed is random-packed media that is designed to be suitable
both for
"static bed" normal operation as well as intermittent "moving bed" action
wherein the entire
bed of media is circulated during cleaning cycles;

o There is no backwash flow for the biofilters - cleaning is accomplished with
no change in
fluid direction;

o The media is designed to achieve specific typical flow channel dimensions;
and,

o The biofilters are specifically designed to treat water with low organic
content, such as
secondary effluent with soluble BOD values of 50 mg/L or less, preferably
25mg/L or less.
[Para 23] The biofilter relies on the growth and proliferation of biofilm
(attached colonies
of micro-organisms) on a support media to effect removal of particulates and
residual

soluble organic compounds. The present invention provides optimized conditions
for
proliferation and performance of particular micro-organisms known as sessile
ciliates and
similar organisms that have unusual capabilities to capture fine particulate
organic matter
such as colloids.

[Para 24] Key factors determining the micro-organism population include
dissolved
oxygen concentration, media design and the flow-channel geometry resulting
from biofilm
growth and accumulation of fine solids. The biofilm growth and accumulation of
fine solids
in the biofilters is progressive, resulting eventually in constricted flow
channels and
pressure loss through the biofilters. Consequently, periodic cleaning of the
filter is required.
In the operation of the invention on unsettled secondary domestic effluent,
the rate of
accumulation of biomass in the filter is fairly slow so that a cleaning
interval of one day or
more should be sufficient in most applications.

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[Para 25] Unlike conventional filters thorough cleaning is not required. In
fact it is
beneficial to retain significant amounts of biofilm on the carriers to
maintain their
efficiency. The cleaning process needs to dislodge excess biomass and move it
into the bulk
fluid so that it can be transported out of the filter. No backwash is
required. Instead,
cleaning of a biofilter is accomplished by first removing the DAF float to
avoid re-entraining
any of the material in the water. Only one biofilter compartment will be
cleaned at a time.
The system will have at least two and preferably three biofilter compartments.

[Para 26] During the cleaning procedure, 100% of the feed water will need to
be
processed through the other compartments. Consequently, this operation is best
done at
"off-peak" times or by using equalization capacity in the secondary treatment
equipment to
temporarily reduce the feed flow rate. However, we have observed that the
biofilters are
quite capable of tolerating flows up to double the design values for short
periods and no
interruptions in feed flow will be required if three biofilter compartments
are employed.
[Para 27] The design of biomass carriers for the biofilters is critical. Of
most importance
are the effective sizes of flow channels resulting from random-packing of a
particular
media. The filter will be designed specifically for optimal particulate
removal efficiency by
micro-organisms. In this regard, the intent is to provide particular flow
channel dimensions
that maximize the opportunity for mature biofilms to capture fine particles.
Consistent with
the preceding discussion, the ideal spacing between biofilm surfaces is 2 - 5
mm. The
media must predominantly exhibit this spacing. In addition, the random packing
must not
result in inter-carrier flow channels that are too large in relation to the
intra-carrier flow
channels. Practically, inter-carrier channels will be larger and this will be
tolerable as long
as the ratio is not excessive. In this invention, the maximum ratio of inter-
carrier channel

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CA 02565052 2006-10-19

size to intra-carrier channel size should not exceed a value of approximately
3. Another
consideration is that the media must enforce tortuous flow paths and not allow
short-
circuiting

[Para 28] A final consideration for the carriers is that they should have a
specific gravity
greater than 1, ideally in the range 1.1 to 1.3, so that they will not float
against top
retaining screens and will be easily fluidized by air sparging, for efficient
cleaning without
excessive scour and turbulence.

[Para 29] The invention achieves high effluent quality prior to the final
filter (consistently
< i NTU operating on domestic secondary effluent) despite utilizing a filter
pore size that is
much larger than that required to produce similar effluent quality in
conventional filters. In
certain applications where further enhancement of effluent quality and a high
degree of
quality assurance is required, the invention may include a final filter that
acts as a "physical
barrier" against fine particles and makes further use of the microbiological
filtration process
described herein. A suitable and advantageous type of filter for this
application is a filter
constructed as a hollow, porous panel covered with industrial felt fabric of a
specified
micron grade (typically 0.5 to 5 micron). The effluent from the invention
would flow to a
tank containing one or more of these panels through the fabric into the core
of panels and
out of the panel through a bottom outlet nozzle connected by flexible conduit
to the
exterior of the tank. The tank will optionally have a low-capacity fine bubble
aeration
system as well as an air scour system. Because the DAF-filter has removed the
vast majority
of particulate and organic matter, these filters (if provided with sufficient
surface area) will
operate for long periods between cleanings. It has been observed that the
final filter
described herein operates for at least several weeks without requiring
cleaning when

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CA 02565052 2006-10-19

operated after the DAF-filter on typical secondary sewage effluent. Cleaning
would be
accomplished by air scour of the filter for a period of several minutes to one
hour, followed
by pumping the tank contents to the secondary treatment unit or the DAF-
Filter. At
infrequent intervals, panels will need to be removed for more thorough
washing.

[Para 30] The DAF employed in this invention differs from the conventional DAF
design in
the following respects:

o The DAF is physically integrated with a bio-filter, both units occupying the
same tank;

o There is no bubble chamber (shallow or confined space at the vessel inlet
where feed and
aerated effluent is made to interact);

o There is no local confinement of flow, in fact, the invention requires a
general ability to
process particulate-containing water ambient in the DAF section as well as
feed water - this
is crucial to the cleaning process;

o Higher recycle to feed rations are required in order to supply sufficient
oxygen to
support biological oxidation in the biofilters;

o Due to the presence of the biofilters, the single pass removal efficiencies
in the DAF do
not need to be as high as in conventional DAFs since fine particles not
captured in the DAF
will be trapped in the biofilters;

o The higher recycle rates increase the overall probability of capture.
Consequently, the
present invention operates with higher recycle rates (typically 50% to 150%)
and tolerates
higher velocities in the DAF; and,

o The float is removed intermittently (rather than continuously) after the
float has had an
opportunity to consolidate and partially de-water.

[Para 311 Advantages of the present invention.
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CA 02565052 2006-10-19

[Para 32] The present invention has the following advantages:

o Ability to remove fine particulates (including colloids) from the secondary
effluent
without the use of coagulants or flocculants;

o Space saving due to the fact that the DAF and biofilter are stacked;

o Enhanced removal of soluble organic compounds including some xenobiotic
compounds,
due to the microbiological diversity within the biofilter and high sludge age
of the biofilm;

o Provides an already dewatered sludge residual eliminating the need for a
separate
dewatering device;

o Lower energy consumption than other tertiary filtration devices; and,
o No backwash flow to be managed.

[Para 33] Description of the Drawings

[Para 34] Figure 1 is a partial schematic drawing of one embodiment of the
invention.
[Para 35] Figure 2 is a partial schematic drawing of the same embodiment of
the
invention as shown in Figure 1.

[Para 36] Figure 3 is a complete schematic drawing of the same embodiment of
the
invention as shown in Figure 1 and Figure 2.

[Para 37] Figure 4 is a schematic drawing of secondary aeration means in one
embodiment of the invention.

[Para 38] Figure 5 is a schematic drawing of the nozzle assembly of one
embodiment of
the invention.

[Para 39] Figure 6 is a schematic drawing of a biomass carrier unit of one
embodiment
of the invention.

[Para 40] Detailed Description

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CA 02565052 2006-10-19

[Para 41 ] Referring to Figure 1, my invention (10) is a system for improved
treatment of
wastewater using dissolved air floatation treatment and a biofilter. Figure 1
is a partial
schematic and does not show all elements of the invention in order to avoid
crowding in the
diagram. The system comprises a source of continuous wastewater flow shown
generally as
(12), means for receiving and containing a predetermined volume of wastewater
for
treatment shown generally as (14), means for aerating the wastewater shown
generally as
(16) and means for purification of the wastewater shown generally as (18)
located within
containing means (14).

[Para 42] The source of continuous wastewater flow (12) is secondary effluent
(19) as
pressurized feed flow or gravity flow through conduit (20). The flow may be
regulated by
way of valve (22) to temporarily stop feed flow during cleaning cycles. The
valve may be a
remote control valve or a manually operated valve depending on the
installation. The feed
flow is generally unsettled secondary effluent containing particulate matter
the type of
which might be found downstream from a secondary biological waste water
treatment

faci l ity.

[Para 43] The means for containing a predetermined volume of wastewater for
treatment
(14) comprises a tank (24) having a predetermined volume. The tank has an open
top (26) a
closed bottom (28) and sides (30) and (32). The tank can be shaped as depicted
in Figure 1
or it can be cylindrical with a similar frusta-conical bottom. The tank can be
manufactured
from concrete, steel, plastic or some other material suitable for the purpose
of waste water
treatment. The tank is adapted to receive secondary effluent from conduit (20)
through
aeration means (16) which is more fully described below. The secondary
effluent is treated
using a biofilter as more fully described beiow and clarified water is
discharged in a post-
treatment stream through manifolds (35) and (37) connected to conduits (33)
and (34)

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CA 02565052 2006-10-19

respectively. Secondary recycle flow is established through manifolds (39) and
(41).
(Primary recycle flow is described below).

[Para 44] Referring now to Figures 1 and 2, a partial schematic of the
complete invention
is shown in both figures. The flow from the manifolds (35) and (37) is
controlled by valves
(36) and (38) respectively which are both open in normal operation. The post-
treatment
flow can be diverted into a secondary recycle stream to control the dissolved
oxygen
content of the effluent stream. This is accomplished by opening valves (45)
and (47) to the
suction of pump (200). The recycle flow is aerated by aerator (99a) the
operation of which
is explained below. The recycle flow modifies water residence time within the
tank (24) and
channel velocities in the secondary biofilter layers.

[Para 45] The tank volume and level is controlled by weir (50). Weir (50) can
be an
external horizontal weir attached to the side of the tank (24). Weir (50) is
adapted to
minimize fluctuations in the level of water within the tank to prevent
overflow and to
facilitate removal of float as more fully described below. Post-treatment flow
enters weir

(50) by way of conduit (52) and is ultimately discharged from the weir by way
of conduit
(54).

[Para 46] Still referring to Figures 1 and 2, the treatment tank (24) includes
a number of
internal structures that facilitate treatment of the feed flow and subsequent
backwashing of
the system as required. Within the tank is a horizontal first zone (60)
comprising means for
aerating the wastewater (16) and a horizontal second zone (64) comprising a
biofilter (18)
for purification of the wastewater. The horizontal first zone is disposed
above the
horizontal second zone.

[Para 47] The horizontal second zone (64) has an upper boundary (66) and a
lower
boundary (68) delineated by an upper (70) and lower (72) screen respectively.
The screens
determine the area of biological treatment of the effluent. The screens have
apertures that

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CA 02565052 2006-10-19

are sized to permit fluid flow but prevent the movement of biocarriers from
the horizontal
second zone. Below the first horizontal zone (60), the tank is divided into
vertical
compartments, each consisting of the corresponding portion of the horizontal
second zone
(64) and a manifold area below the second screen. Figure 2 illustrates a
vertical first
compartment (74) adjacent to a vertical second compartment (76). These two
compartments are non-communicative and operate independently. Since they are
sealed
from each other one may be cleaned while the other still operates. Two such
vertical
compartments are shown for the purpose of illustration. In the preferred
embodiment three
such vertical compartments are employed.

[Para.48] Referring now to Figures 1, 2, and 3, there is shown in Figure 3 a
complete
schematic of the invention. The vertical first (74) and vertical second (76)
compartments
comprise a primary upper layer (80 and 81), a secondary layer (82 and 83) and
a third
manifold layer 85 and 87. The top two layers are separated by the primary
recycle
withdrawal manifolds X and Y. The second and bottom layers are separated by a
screen
(72). Within a compartment, all three layers are in hydraulic communication.
Water for the
primary wastewater recycling is drawn from the primary recycle manifolds X and
Y through
valves (92) and (94) into recirculation loop conduit (96) through the
supplementary aeration
device (99b) and then into the suction of pump (100). Secondary recycling is
accomplished
by opening valves (45) and (47) and drawing water as required from manifolds
(39) and (41)
into the suction of pump (200) and aeration device (99a) on conduit (202)

[Para 49] Referring to Figure 4 supplemental aeration device (99) is depicted.
Influent
(101) flows by gravity (or pumping as the case may be) from the DAF to the
standpipe (103)
and flows downward in the standpipe (103). Simultaneously, air introduced into
the bottom
of the standpipe from air pump (107). Air flow is measured by flow meter (109)
and

controlled by control valve (111) on conduit (113). The flow is aerated by
fine bubble
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diffuser (115) within the standpipe (103). Air rises as fine bubbles (105) in
the standpipe
creating counter current two-phase flow thereby aerating the influent. Water
exits the
standpipe through conduit (117). Supplemental aeration devices (99) are
employed to add
oxygen to the primary and secondary recycles respectively.

[Para 50] Referring back to Figure 3, pump (100) is a high head low flow type
centrifugal
pump. On the discharge conduit (102) is disposed air entrainment means being a
venturi-
type cavitating air injector (104) adapted to inject air into the
recirculation flow. Air is
forced into the recycling flow and mixed with it. Within the normal operating
range of the
system, the back pressure on the discharge end of the venturi will not
substantially affect
the amount of air entrained into the recycle water stream but it will not
affect the flow of
recycle water itself. Hence a change of air flow will not affect the recycle
water flow rate.
The pump (100) and the air injector (104) must be compatibly chosen. Control
valve (110)
and flow meter monitor (112) exist to control and monitor the air flow into
the recycle
stream.

[Para 51] Discharge conduit (114) from the venturi is precisely sized so that
the
entrained air within the recycle flow produces a two-phase mixture called a
"bubble flow" or
a "froth flow" representing the most efficient dissolution of air into the
water flow. The
diameter of conduit (114) is typically smaller than the diameter of the
recycle flow loop line
(96). Plastic tubing is often used. The length of the tubing needs to be
minimized to while
ensuring complete dissolution of entrained air otherwise the pressure drop
within the
tubing will severely restrict air capacity and cause a deterioration of the
flow regime.

[Para 52] Referring now to Figures 1 to 5, Figure 5 shows a schematic of the
DAF aerating
nozzle assembly (120) of the invention. The nozzle assembly communicates with
discharge
conduit (114) containing a supply of pressurized recycled water flow. Conduit
(114) is
provided access through the wall (32) of tank (24) by way of stand-pipe (124).
The aerating

Page 17 of 30


CA 02565052 2006-10-19

nozzle assembly is also in communication with conduit (20) containing a supply
of
pressurized feed flow.

[Para 53] Conduit (20) penetrates the wall of the tank (24) by way of a stand-
pipe (126)
and is connected to the aerating nozzle assembly at connection (128). The
nozzle assembly
includes a horizontal section (130) and a vertical section (132). The vertical
section has an
inside wall (134), a closed first end (136) and an open second end (138).
There is also a
third conduit (140) having a vertical orientation, an outside wall (142), a
first end (144) in
communication with the source of pressurized recycled flow conduit (114) and a
second
open end (145) having a discharge nozzle (146) so that the pressurized
recycled flow is
discharged there from. Conduit (140) is disposed centrally within the second
conduit
vertical section (132) and penetrates the closed first end (136) in a sealed
relationship

hence forming an annulus (150) between the inside wall of the second conduit
vertical
section and the outside wall of the third conduit. The discharge nozzle (146)
has a pre-
calibrated discharge aperture (152).

[Para 54] Still referring to Figure 5, the aerating nozzle assembly further
comprises an
impingement plate (154) disposed a predetermined and adjustable distance (156)
from the
discharge aperture (152) and forming a gap (158) above the discharge aperture
and below
the impingement plate. The impingement plate is circular in shape and
suspended by

suspension means (159). Pressurized recycled flow discharged from the
discharge aperture
impinges upon the centre of said impingement plate.

[Para 55] When the pressurized recycled flow is discharged from the discharge
aperture
it experiences a pressure drop between the discharge aperture and the
impingement plate
so that dissolved air entrained in the flow forms air bubbles. The pressurized
recycled flow
discharged from the discharge aperture mixes with the pressurized feed flow
discharged
from the annulus (150). The result is that particulate matter contained in the
pressurized

Page 18 of 30


CA 02565052 2006-10-19

feed flow is in close dynamic proximity to said air bubbles thereby causing
the particulate
matter to attach to the air bubbles and float. In this manner a dewatered
float layer (160) is
formed at the top of zone (60) having a high concentration of particulates.
This float layer
is subsequently harvested by harvesting means depicted as (162) and comprises
a moving
belt mechanism that lifts the float layer from the DAF water surface over the
edge of the
tank and into a holding tank for later disposal. The float layer typically
contains between 7%
and 15% dry solid particulates by weight.

[Para 56] Referring back to Figures 1 to 3, the biofilter comprises a
plurality of dynamic
biomass carriers adapted to promote the growth of micro-organisms. The biomass
carriers
are active in the second horizontal zone (64) and between screens (70) and
(72). Since the
biomass carriers are small, the screens have apertures sized to prevent
leakage of the

biomass carriers from zone (64). The biomass carriers are adapted to promote
the growth
of micro-organism on their surfaces. The predominant micro-organisms generally
include
sessile ciliates.

[Para 57] Referring now to Figure 6 there is shown a typical biomass carrier
(160) of the
invention. Each biomass carrier of the plurality of biomass carriers within
zone (64) are
separated by an intra-carrier flow channel (162) having a first size expressed
as a median
value of channel diameter. The biomass carriers comprise a plurality of
surfaces (164)
adapted for optimized growth of biomass. These surfaces are arranged to create
a plurality
of inter-carrier flow channels (166) having a second size expressed as a
median value. The
surfaces (164) are disposed apart a distance of between 2mm and 5mm. The ratio
of the
first size to the second size is less than 3. Each biomass carrier has a
specific gravity
greater than one. In the preferred embodiment of the invention the specific
gravity of each
biomass carrier is between 1.1 and 1.3. Typical dimensions for the biomass
carriers are
shown in Figure 6.

Page 19 of 30


CA 02565052 2006-10-19

[Para 58] Alternative biomass carrier types, including some commercially
available types,
may be employed in the device to varying levels of effectiveness. The design
described
herein is optimized for this application.

[Para 59] Referring to Figure 3, the system may include an optional secondary
filter.
Effluent from the weir (50) is directed by conduit (54) to a secondary filter
tank (170) in
which there is disposed a non-woven industrial felt fabric (172) having a
grade of 0.5 to 5.0

microns. The secondary filter further comprises a low-capacity fine bubble
aeration system
(175) to keep particulates suspended and an air scour system (174) to clean
the filter
periodically. Effluent from the secondary filter is discharged through conduit
(177).

[Para 60] Referring to Figures 2 and 3, to commence cleaning of vertical zone
(74), valve
(36) is closed to isolate the zone from the effluent discharge conduit (52).
If not already
open, valve (45) is opened to pump (200). Valve (53) (air supply valve) is
opened for a pre-
determined period of time and (if not already operating) pump (200) is
activated at the

same time. The air supplied to the zone out of the air pipe (57) is just
sufficient to cause the
bed of biomass carriers to move and circulate, sloughing off and dislodging
biomass. Media
in the areas immediately above the pipe (57) will be lifted upward, dispersed
toward the
opposite side of the zone and then carried downward, creating a rotational
motion. Multiple
revolutions of the media will be produced with the result that all carriers
move relative to
one another and carriers assume different positions in the filter. During this
process,
biomass is liberated and becomes fully entrained in the bulk fluid such that
the fluid in the
biofilter zone (74) becomes highly turbid. Most of this biomass will be
carried into zone
(60) where flotation processes will take it to the float layer (160). Other
solids are carried
out with the flow through pump (200) and conduit (202) through aeration means
(99a) and
into the feed flow conduit (20) for return to zone (60). After an interval of
typically one to

Page 20 of 30


CA 02565052 2006-10-19

several minutes the air supply is shut down, allowing the biomass carrier bed
to re-
consolidate, with each biomass carrier assuming a new location in the bed.
Pump (200)
continues to operate for an extended period of time (typically at least 30
minutes) to ensure
that unattached biomass is removed and effluent quality standards are
regained. At that
point, valve (36) is reopened. Flow will be re-established through the
compartment to the
effluent weir. To clean the opposite zone (76) valve (38) would be closed and
air supply
valve (55) opened to air pipe (59).

[Para 611 During the cieaning procedure, 100% of the feed flow will need to be
processed
through the other zone(s). Consequently, this operation is best done at "off-
peak" times or
by using equalization capacity in the secondary treatment equipment to
temporarily reduce
the flow rate. However, we have observed that the biofilters are quite capable
of tolerating
flows double the design values for short periods and a system with three
vertical zones will
not require a cessation in feed flow for satisfactory cleaning.

[Para 621 Although the description above contains much specificity, these
should not be
construed as limiting the scope of the invention but as merely providing
illustrations of
some of the presently preferred embodiments of this invention. Thus the scope
of the
invention should be determined by the appended claims and their legal
equivalents, rather
than by the examples given.

Page 21 of30


CA 02565052 2006-10-19

What is claimed is:

[Claim 1] A system for improved dissolved air floatation (DAF) treatment of
wastewater
wherein said system comprises: a controlled source of continuous wastewater
flow
containing unsettled secondary effluent containing a first size and a second
size of
particulate matter wherein said first size is larger than said second size; a
tank having a first

predetermined volume for receiving and containing a second predetermined
volume of said
wastewater for treatment and discharging a post-treatment stream; means for
capturing the
first size of the particulate matter for disposal comprising a DAF nozzle;
means for

capturing the second size of the particulate matter for disposal; and
cleansing means.
[Claim 2] The system of claim 1 wherein said means for capturing the second
size of
particulate matter is a biofilter and wherein said cleansing means is adapted
to periodically
cleanse said biofilter.

[Claim 3] The system of claim 2 wherein the second predetermined volume of the
wastewater in the tank is determined by a weir, wherein said weir receives
said post-
treatment stream and discharges the post-treatment stream into a system
discharge line.
[Claim 41 The system of claim 3 wherein the tank further comprises a
horizontal first
zone comprising said means for aerating the wastewater, a horizontal second
zone
comprising the biofilter disposed below said horizontal first zone, and a
horizontal third
zone disposed below said horizontal second zone wherein said first, second and
third zones
are in hydraulic communication.

[Claim 5] The system of claim 4 wherein the horizontal first zone and the
horizontal
second zone are separated by a first screen and wherein the horizontal second
zone and the
horizontal third zone are separated by a second screen.

Page 22 of 30


CA 02565052 2006-10-19

[Claim 6] The system of claim 5 wherein the horizontal second and third zones
are
divided into at least first and second vertical and adjacent compartments so
that said at
least first and second vertical and adjacent compartments are non-
communicative and
operate independently.

[Claim 7] The system of claim 6 wherein the second horizontal zone of the at
least
first and second vertical compartments is divided into a primary upper layer
and a
secondary lower layer, said primary upper and secondary lower layers separated
by a
wastewater recycle withdrawal manifold disposed within the second horizontal
zone and
wherein the third zone of the at least first and second compartments comprises
a post-
treatment stream discharge manifold disposed above a secondary recycle flow
manifold.
[Claim 8] The system of claim 7 wherein said DAF nozzle comprises an aerating
nozzle assembly disposed centrally within the first horizontal zone and above
the second
horizontal zone.

[Claim 91 The system of claim 8 wherein said aerating nozzle assembly
communicates with a first conduit containing a supply of pressurized recycled
flow drawn
from said wastewater recycle withdrawal manifold and wherein said supply of
pressurized
recycle flow is in communication with a cavitating air injector for entraining
dissolved air
into said supply of pressurized recycle flow.

[Claim 10] The system of claim 9 wherein said first conduit is sized to
promote air
dissolution within the supply of pressurized recycled flow and to achieve a
"froth flow" mass
transfer regime and wherein the first conduit terminates at the bottom end of
a third
vertical conduit and further wherein said third vertical conduit top end
comprises a
discharge nozzle having a discharge aperture.

[Claim 111 The system of claim 10 wherein the aerating nozzle assembly
communicates with a second conduit in communication with a supply of
pressurized feed
Page 23 of 30


CA 02565052 2006-10-19

flow containing particulate matter of a first size and wherein said second
conduit comprises
a horizontal section terminating in a vertical section, wherein said vertical
section has an
inside wall, a closed first end and an open second end.

[Claim 1 2] The system of claim 11 wherein the third vertical conduit is
disposed within
the vertical section of the second conduit thereby forming an annulus.

[Claim 1 3] The system of claim 12 further comprising an impingement plate
disposed
an adjustable distance above said discharge aperture thereby forming an
adjustable gap
between the discharge aperture and said impingement plate so that the
pressurized
recycled flow discharged from the discharge aperture impinges upon the centre
of the
impingement plate with pressurized feed flow discharged from said open end of
the second
conduit.

[Claim 14] The system of claim 13 wherein the pressurized recycled flow
discharged
from the discharge aperture experiences a pressure drop within said adjustable
gap so that
air bubbles are formed therein.

[Claim 1 5] The system of claim 14 wherein the flow of pressurized feed
containing
first sized particular matter that is discharged out of the open end of the
second conduit is
in sufficiently close dynamic proximity to said air bubbles in the pressurized
recycled flow
discharged from the discharge aperture so that the first size of the
particulate matter
attaches to the air bubbles and floats to the top of said horizontal first
zone the result
being the formation of a float layer for later harvesting.

[Claim 16] The system of claim 15 wherein said biofilter comprises a plurality
of
dynamic biomass carriers disposed and circulating within the horizontal second
zone and
adapted to promote the growth of micro-organisms there upon.

[Claim 1 7] The system of claim 16 wherein each biomass carrier of said
plurality of
dynamic biomass carriers are separated by an intra-carrier flow channel having
a first size.
Page 24 of 30


CA 02565052 2006-10-19

[Claim 181 The system of claim 17 wherein each biomass carrier of the
plurality of
biomass carriers has a specific gravity greater than one and comprises a
plurality of
surfaces disposed a predetermined distance apart for optimized growth of
biomass and
wherein said plurality of surfaces are arranged to create a plurality of inter-
carrier flow
channels.

[Claim 191 The system of claim 18 wherein cleansing means comprises means for
isolating the biofilter, means for introducing air into the biofilter to
agitate the biomass
carriers so that excessive biomass is shed; and, means for transporting said
shed biomass
to the first horizontal zone.

[Claim 20] The system of claim 19 further comprising a final filter located on
the
system discharge line.

Page 25 of 30

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date Unavailable
(22) Filed 2006-10-19
(41) Open to Public Inspection 2008-04-19
Dead Application 2009-04-17

Abandonment History

Abandonment Date Reason Reinstatement Date
2008-04-17 FAILURE TO RESPOND TO OFFICE LETTER

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $200.00 2006-10-19
Maintenance Fee - Application - New Act 2 2008-10-20 $50.00 2008-07-22
Maintenance Fee - Application - New Act 3 2009-10-19 $50.00 2008-07-22
Maintenance Fee - Application - New Act 4 2010-10-19 $50.00 2008-07-22
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
JACKSON, DAVID
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Representative Drawing 2008-03-25 1 16
Abstract 2006-10-19 1 12
Description 2006-10-19 25 1,040
Claims 2006-10-19 4 147
Drawings 2006-10-19 4 54
Cover Page 2008-04-14 2 46
Correspondence 2006-11-28 1 35
Prosecution-Amendment 2007-01-12 1 36
Correspondence 2006-11-28 1 93
Assignment 2006-10-19 2 84
Correspondence 2008-01-17 2 33
Correspondence 2008-01-17 2 41
Correspondence 2008-03-18 2 49
Correspondence 2008-06-23 1 39
Correspondence 2008-07-10 1 82
Correspondence 2008-07-22 1 15
Fees 2008-07-22 1 34