Note: Descriptions are shown in the official language in which they were submitted.
10~;~4~0
The present invention xelates to ozonation of
waste water to remove oxidizable contaminants therefrom.
This application is a division of copending
Canadian application Serial No. 218,165 filed January 16,
1975. The parent application claims a multistage waste
water treatment system which includes the ozonation tr~at-
ment of this invention. This application claims only the
ozonation treatment.
In accordance with the present invention, there
is provided a process for the ozonation of waste water con-
taining bacterial and odor-imparting contaminants and other
contaminants including suspended solids, dissolved organic
material, nitrogenous material, phosphate material,
turbidity-providing materials in a single upright reaction
tank, which comprises: separating the reaction tank into a
first vertically-extending zone extending upwardly from
the bottom of the tank through the height of the tank and -
a second vertically-extending zone extending the height of
the tank in fluid flow communication with the first zone at
the lower end thereof only; establishing a liquid level in
each of the zones and a flow path of liquid through the
tank downwardly through the first zone and upwardly through
the second zone; feeding the waste water to the first zone
at the liquid level therein; feeding a gaseous mixture of
ozone and oxygen into the first zone at the lower end
thereof; allowing the gaseous mixture to rise in the first -
zone countercurrently to the waste water flowing in the flow ~
path; absorbing ozone and oxygen from the gaseous mixture - ~-
in the waste water in the first zone; passing the waste
water having gases absorbed therein from the first zone to
the second zone; oxidizing contaminants in the waste water
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with the adsorbed oxygen and ozone in the second zone;
filterin~ from the treated liquid in the second zone adja-
cent the downstream end of the flow path solids formed in
the second zone; and withdrawing treated liquid having a
decreased contaminants content from the downstream end of
the flow path.
The invention is described further by way of
illustration with reference to the accompanying drawings,
in which:
Figure 1 is a schematic representation of a waste
water treatment system embodying this invention;
Figure 2 is a sectional schematic representation
of a primary treatment unit for use in the system of Figure ;
l; '
Figure 3 is a sectional schematic representation
of a phosphate removal unit for use in the system of Figure l;
Figure 4 is a sectional scbematic representation
of an ozonation unit which utilizes the process of this
invention and for use in the system of Figure l; and
Figure 5 is a sectional schematic representation of
a fixed bed adsorption-biooxidation unit for use in the
system of Figure 1.
Referring to the drawings, a four-stage sewage
treatment system 10 provided in accordance with the invention
claimed in the aforementioned parent application includes
a primary treatment 12, an adsorption-biooxidation treatment ~ :
14, a chemical treatment 16 and a fixed bed adsorption~
biooxidation treatment 18. Part of the chemical treatment
16 constitutes the subject of this invention. -
Raw comminuted sewage is fed by line 20 to the ;~
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primary treatment 12. As may be seen in more detail ~n Figure
2, the primary treatment 12 occurs in a circularly cross-
sectioned reactor 22. An inverted funnel-like member 26 is
located within the container 22 and defines therewith a first
chamber 28 between the funnel-like member 26 and the container
22, a sludge settling chamber 30 and a sludge separation
chamber 32 inside the funnel-like member 26.
The funnel-like member 26 includes a skirt portion
34 concentric with and spaced inwardly from the inner wall of
the container 22, a truncated cone portion 36 and a throat
portion 38 also concentric with the container 22 and extending
upwardly above the intended liquid level in the container 22.
The sludge settling chamber 30 also is defined by
a tru`ncated conical wall 40 of the container 22 whereby the
sludge settling chamber 30 has a decreasing diameter towards
the base of the container 22.
A hollow riser tube 42 is positioned axially of
the container 22 and extends through the sludge separation -
chamber 32 into the sludge settling chamber 30 to a location
spaced immediately upwardly of the base of the container 22, the
riser tube 42 flaring outwardly towards the lower end thereof. ~
A gas feed tube 44 is situated within the riser : -
tube 42 to feed air, oxygen or other gas into the riser tube :~
42 adjacent the lower end of the riser tube 42 to draw sludge
out of the settling chamber 30 into and up the riser tube 42
under the influence of the gas rising in the tube 42.
The riser tube 42 adjacent its upper extremity but
within the reactor 22 communicates with cross-arm members . -
46 extending radially of the container 22 which in turn com- -.
. ~; . .
municate with tubular discharge members 48 which include a
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downwardly-extending portion and a horizo~tally-extending
portion.
The sewage is fed to the container 22 through
pipe 24 and is mixed with recycling mixed liquor suspended
solids fed from the discharge members 48. The tangential dis-
charge of the recycling MLSS causes rotation of the reacting
liquor in the first chamber 2~ about the axis of the container 22.
The rotation of the material in the chamber 28
applies centri~ugal forces to the suspended solids, causing
the solids having a specific gravity greater than the liquid
medium to concentrate adjacent the inner wall of the container 22,
while the solids having a specific gravity less than the
liquid tend to move towards the axis of the reactor 22.
Gravitational forces acting on the heavy solids
causes them to settle towards the sludge settling chamber 40.
Anaerobic decomposition of the settled solids in the chamber
40 occurs, decreasing their volume and mass. The rotation
of the solids in the chamber 28 provides the mixing required
to speed up the anaerobic reactions.
The lighter suspended solids move upward with the
waste water through the sludge separation chamber 32, wherein
further gravitational separation of suspended solids occurs.
The microorganisms in the liquid consist of
facultative and ~naerobic bacteria responsible for hydrolysis
and fermentation of complex organic compounds to simple
organic acids. The microorganisms tend to be retained and
are recycled with the recirculating sludge in riser tube 42
and hence assist in hydrolyzing and decomposing the suspended
solids.
In this way, suspended solids present in the sewage
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feed in line 24 and separated in the chambers 28, 30 and 32
are continuously hydrolyzed and fermented, thereby continuous-
ly decreasing their volume and mass. Thus,
withdrawal of solids from the reactor 22 rarely is required,
such withdrawal being made typically by pipe 50. The reac-
tor 22 also tends to decrease the concentration of soluble
organic matter and to equalize wide variations in soluble
organic matter concentration in the feed sewage.
The processed waste water is removed from the
upper portion of the chamber 32 through a pipe 52 for passage
to the adsorption-biooxidation treatment 14.
The adsorption-biooxidation treatment consists of
contact with activated carbon and a mixed microbial popula-
tion in a reactor 54. This contact serves to remove organic
matter, organic nitrogen, ammonia and nitrite and nitrate
nitrogen from the processed waste water.
The waste water, if required, may ~e flash aerated
from the reactor 54 by external flash aerator 56 and passed
by line 58 to a clarifier 60. In the clarifier 60, the bio-
logical reactions are extended, functioning thereby, ineffect, as a second stage reactor. The suspended solids are
separated from the liquid phase in the clarifier 60 by settling. ~
The settled sludge mainly is withdrawn from the clarifier 60 ~ -
by a flash aerator for recycle, after saturation with oxygen,
to the reactor 54 by line 62. The clarified effluent is
removed from the clarifier 60 by external riser 64 for dis~
charge from the adsorption-biooxidation treatment 14 by line -
66 to the chemical treatment 16. Excess sludge may be with- ~
- drawn from the adsorption-biooxidation treatment 14 by pipes ~ ~;
65 ànd 67 respectively associated with the reactor 54 and the ~ ;
clarifier 60.
The adsorption-biooxidation treatment 14 is described
in more detail and forms the subject of U.S. Patent No.3,s8Q,556.
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Reference may be had to the latter patent for
additional process and constructional details of the reactor
54 and the clarifier 60. -
The processed waste water in line 66 is passed to
the chemical treatment 16, which consists of a phosphate re- -
moval unit 68 and an ozonation unit 70. The operations which
are effected in the ozonation unit 70 constitute the present
invention and are defined in the claims.
Prior to feed of the processed waste water to the
phosphate removal unit 68, a chemical coagulant, typically
alum, is added to the processed waste water by line 72. If
desired, additional chemicals such as hypochlorite may be
added, as may an anionic polymer by line 74.
As may be seen more particularly from Figure 3,
the phosphate removal unit 68 consists of a cylindrical con-
tainer 76 in which a conical body member 78 is positioned,
defining a first chamber 80 between the conical body member :
78 and the interior wall of the container 76, a second chamber '
82 within the conical body member 78 and a third chamber 84
located above the conical body member 78.
The processed waste water in line 66 with added
chemicals is fed tangentially into the first chamber 80 through :.
outlet pipe 86 of a hydrostatic head box 88 located in the
upper portion of container 72. The processed waste water in ~ -
line 66 also may include occasional loss of biological sludge
from the clarifier 60. This loss provides automatic and self-
regulating control of the concentration of the microbial popu-
lation in the adsorption-biooxidation treatment 14.
The first chamber 80, which acts as a reaction
chamber for phosphates, contains coagulated suspended solids,
i.e. chemical sludge, which are maintained in a rotating
-
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fluidized bed. The rotation of the sludge in the first chamber
80 is maintained by the tangential inlet flow throughout
outlet pipes 86 at the lower ends thereof and further by action
of external riser tube 64 communicating with the first chamber
80 through opening 90.
The upflow velocity of the liquid in the first
chamber 80 is responsible for fluidization of the coagulated
particles in at least the upper portion of the chamber 80.
~he upflow velocity is proportional to the flow rate of the
waste water through outlet pipes 86 and to the cross-
sectional area of the first chamber 80.
The chemical reactions between the added chemicals
and the impurities occur in the lower portion of the f irst
chamber 80 and the coagulation of the formed flocs occurs
in the upper portion of the first chamber 80. The coagulated
flocs tend to form a layer of chemical sludge in the upper
portion of the first chamber 80 which adsorbs impurities and -
hence tends to increase the overall removal efficiency of
.. .. -
the unit.
The coagulated sludge overflows from the first
chamber into the second chamber 82, which acts as a settling -~
chamber for the coagulated sludge. The conical shape of the
second chamber 82 causes thickening of the sludge therein. A
riser tube 92 èxtends axially through the unit and ;~ -
terminates immediately above the base of the second chamber 82. - - A gas flow tube 94 is positioned internally o~
the riser tube 92 for feed of air, or other gas, into the
riser tube 92 adjacent the lower end thereof, the consequent ~ -
upward flow of gas in the riser tube 92 causing material to be ~ -
drawn from the second chamber 82 into and upwardly in the
'' .'..~
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~ - .. . .
- . -:
,, . . ,, , ~
. , , , . . ' . . ' ' .
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riser tube 92 for discharge of the chemical sludge from the
unit 68 through pipe 96,either continuously or intermittently,
as desired.
The chemically-treated and clarified ~aste w~ter
flows upwardly from the first chamber 80 to the third chamber
84 for removal ~rom the unit 68 through pipe 98,
Gases formed in the phosphate removal unit 68 may
be vented therefrom by vent 99. Sludge accumulations in the
first chamber 80 may be removed through pipe 101 as required.
The chemically-treated effluent from the phosphate
removal unit 68 in line 98 is fed by an external riser tube 100 inbo
the ozonation unit 70 through pipe 102. The oæonation unit
70 incl~des an outer cylindrical container 104 and an inner
cylindrical tube 106 perforated at its lower end by perfora-
tions 108.
An ozone feed tube 110 is located axially of the
inner cylindrical tube 106 and terminates at its lower end in -,
a diffuser ring 112 located above the perforations 108.
The inner cylindrical tube 106 and the outer
cylindrical container 104 define inner and outer chambers 114 ;
and 116 respectively within the ozonation unit 70. An upper
portion of the inner chamber 114 is packed with polyethylene
pall rings 118 or similar floating packing material. Simi-
larly, an upper portion of the outer chamber 116 is packed
with polyethylene pall rings 120 or similar floating packing -
material.
The liquid to be treated is fed by line 102 to
the top of the inner chamber 114. As the waste water moves
downwardly through the inner chamber 114 towards the perfora~
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tions 108, it iscountercurrent~y contacted with ozone
and oxygen fed to the inner chamber 114 through the
diffuser 112. The waste water absorbs ozone and oxygen
from the rising gas bubbles.
The downward velocity of the waste water through
the inner chamber 114, which determines the contact
time of the gas bubbles in the inner chamber 114 and
hence the proportion of oxygen and ozone absorbed by
the liquied, is less than the velocity of upward flow
~f the gas bubbles but greater than one-third of vel-
ocity of a single rising in stationary liquid.
As the concentration of the ozone in the bubble
volume decreases due to the diffusion of ozone into
the liquid as the gas rises in the i-nner chamber 114,
a concentration gradient develops in the gas bubbles
and the rate of mass transfer decreases. ~ ~ -
When the gas bubbles encounter the packing 118, ;
they break down and reform. There results mixing of
the gas in the volume of the bubble, disrupting the con-
centration gradient established in the radial direction ~the ~-~
bubble and increasing the concentration of ozone and
oxygen at the bubble surface, and hence increasing
the mass transfer rate of the diffusing absorbing
gases in the packing 118. ;
The presence of the floating packing 118 in the ;~
first chamber 114 prevents axial mixing of the liquid -~-
thereby creating conditions for continuous multistage ~
. ..-.. :..
absorption.
The ozone saturated waste water exits from the
first chamber 114 through perforations 108 into the
lower portion of the second chamber 116. Suspended
solids present in the waste water settle out in the
- ~ . .
1~4~4~g)
the second chamber 116 and
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. . ... .
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may be periodically removed from the ozonation unit 70 by
line 122.
Oxidation of the contaminants present in the waste
water occurs as the water rises in the chamber 116 first
through the lower portion and then through the packing 120.
A fine precipitate is formed in the oxidation and is trapped
in the packing bed 120. The volume of precipitate is very
small and hence long continuous operation of the ozonation unit '
70 is achieved before backwash of the packing bed 120 is
required.
Oxidized waste water is removed from the ozonation
unit 70 through pipe 124 located at the top of the second
chamber 116. The oxidation of the waste water in the ozona-
tion unit 70 results in an effluent of decreased colour, odor
and turbidity, containing chemically oxidized organic and
inorganic compounds and is disinfected.
lf ~urther treabment is required, the effluent from the chemical ;- -
treabment may pass by line 124 to the fixed bed adsorption-bicoxidation
treatment 18. The adsorption-biooxidation treatment 18 is
.... :. .
conducted in a cylindrical vessel 126, shown in detail in
Figure 5, and having a multiple number of beds of different --
materials therein for percolation of the waste water feed in
line 124 therethrough. ~ ~
The waste water in line 124 is fed into the ~ ^ -
vessel 126 through a distributor 128 on the upper surface of
a bed 130 of granular activated carbon. Suspended solids - -
are removed from the waste water by the granular activated
carbon bed 130 by filtration and the dissolved organic matter
is removed by adsorption on the activated carbon. The concen-
tration of organic matter on the surfaces of the activated
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carbon increases to the point where microorganisms can survive
and biooxidation can occur.
The concentration of residual organic material in
the waste water in line 124 is very low and hence the dissolved
oxygen present in the waste water is sufficient for the bio-
oxidation and additional aeration is not required.
Backwashing of the fixed carbon bed 130 is required
only very infrequently and hence the microbial population in
the media is acclimatised to the type of food present in the
waste water. Therefore,the adsorptive capacity of the activated
carbon is continuously restored by the microorganisms and
thus consistent removal of organic carbon from the waste water
on the fixed carbon bed 130 is achieved.
Successive beds of anthracite 132, sand 134
and gravel 136 are provided for consecutive filtration of
residual suspended solids from the waste water, the processed
water being recovered from the vessel 126 through collector
1~8 an~ line 140.
Valved backwash water and air feed lines 142 and
144 respectively may be provided along with a backwash overflow
line 146.
Ozone for the ozonation unit 70 is provided by
line i48 from any convenient source thereof. The air required --
for the flash aerators in the primary treatment vessel 22,
the adsorption-biooxidation reactor 54 and clarifier 60 and
the riser tubes 56, 64, 82 and 100 may be provided by a common
air line 150 with suitable valving, as required.
The hydraulically-integrated waste water treatment
system 10 therefore provides a four-stage treatment of waste
water to remove substantially completely contaminants from
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the waste water, including suspended solids, organic material,
nitrogenous material, phosphates, coliform, turbidity and odor,
in which movement of liquids is achieved by utilizing gravity
or air riser tubes.
The filtered effluent in line 140 may be treated
further, if desired or required, to provide water of potable
quality. Such procedures may include one or a combination of
e~aporation, reverse osmosis, ion-exchange and disinfection.
Solid wastès removed from the system in lines 50, 65, 67, 96,
101 and 122 may be disposed of in any desired manner. The
quantity of wastes requiring dispo$al is, however, quite
small.
The ozonation treatment to remove bacterial and
odor-imparting contaminants is illustrated by the following
Example of the overall multistage waste water treatment
system defined in the aforementioned parent application.
-. ..... - .. .
' . ' ' '
,- ., . ; ., : ,. ., . ., . : .. . . .
Example ~ 34
An approximately 4000 gallon perday sewage treat-
ment pilot platn operation was set up utilizing the
equipment illustrated in Figure l and was operated con-
tinuously for a period of 38 days. The contaminants
of the sewage in the feed line 20 varied widely over
the test period. The operation was unattended except
for the taking of samples for analysis .
The hydraulic characteristics of the pilot plant
operation over the test period are reproduced in the
following Table I:
TABLE I
Characteristic Ran~e Avera~e
Feed flow rate GPD 1872 to 4896 3168
Hydraulic detention time
(Hrs. -based on Q)
Primary clarifier 2.9 to 7.7 4.5
A-B process - reactor 4.3 to 11.0 6.7
- clarifier 1.7 to 4.6 2.7
Chemical Treatment
P04 reactor 4.8 to 12.8 7/~l4
Ozonation 2.4 to 6.3 3.7
Recycle percent (based on Q)
for A-B process 370 to 490 420
Surface overflow rates GPM/
sq. ft. (baeed on Q)
-primary clarifier 0.19 to 0.50 0.32
-A-B clarifier 0.17 to 0.34 0.23
-P04 reactor-clarifier 0.11 to 0.31 0.20
The water quality at various locations in the
pilot plant was detemined, namely, the effluent from
the primary clarifier, the effluent from the adsorp-
tion-biooxidations process, the effluenb from the
Pp4 reactor-clarifier, the effluent from the ozona-
tion unit and the effluentfrom the multimedia fil- - -
tration. These water quàlity results are reproduced -
in the following Table II:
- 14 - -~
16)43480
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1t;J43480
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From the results reproduced in the above T~ble II,
it is possible to calculate the contribution of the individual
steps to the overall removal efficiency of the system. The
results of this calculation are reproduced in the following Table
III:
TABLE III
TreatmentContaminant
BOD5 TOC SOC TKN NH3 NO PO4 S~S. Turb. Coli. `
% % % ~ % mq~l % % ~ %
.
Primary 12 24 113 0 +0.8 5 50 35
Adsorption-
biooxidation 80 67 72 90 ~8 +3.0 20 42 62
Chemical 6 5 85 0 -0.4 70 3 1 >99.99
Media Filtration 1 3 71 0 - -4 4
Total 99 99 9899 98 - 91 99 99 ~99.99
The above tabulated results demonstrate the effectiveness i -
of the system of Figure 1 in removing substantially completely organic,
nitrogenous, phosphorus, suspended solid and coliform contaminants
from waste water.
The sewage treatment system 10 may be designed to handle
a wide range of liquid feed rates while remaining unattended,
typically from 5000 to 100,000 gallons per day, and hence provide -
an effective waste water renovation system for use in apartment ~
blocks, and the like. ~ - -
The present invention, therefore, provides an operation
treatment for removal of certain contaminants from waste water.
Modifications are possible within the scope of this invention.
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,,, ,.,. . ., ~.. ,,,, .,. - 7-- ' ' ' ' ' ' ' '
