Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02372331 2004-03-12
Amended 2
FIELD OF INVENTION
The present invention relates to a system and method for removing pollution
from water.
S BACKG1ZOUND OF THE INVENTION
1t has long been desirable to remove pollutants from water in a safe, efFcient
and cost-
efFective manner. Agricultural, industrial, and street runoff, among other
polluted water
flows, require treatment before being released into the environment. The high.
concentration ofpollutants in these wastes can overwhelm self-purifying
mecha~oisms in
the receiving environment. When this occurs, the z~esult is contaminated
ground water
and/or surface watex.
Public wastewater treatment systems typically serve high-density population
areas.
I S However, in less darscly populated areas or where public sewage treatment
is not
available, many homes and businesses use a septic system, implemented on-site,
far the
trcaxment and disposal of wastewater or sewage.
A typical on-site waste fluid treatment, or septic, system includes a mound or
drainfield
and a septic tank. Waste fluids such as household sewage may include
wastewater tcom
washers and dryers, showers and bathtubs, toilets, disposals, disposal waste,
sink
wastewater and wastes from various commercial operations. In a typical on-site
septic
CA 02372331 2004-03-12
Amended 3
system, the wastewater generally drains into a septic tank before being routed
to the
mound or drainfield. A septic tank typically separates sewage into solid and
liquid
fractions, then introduces the separated liquid fraction (effluent) back into
the ecosystem
with significant levels of undesirable nutrients and other pallutian.
Undesirable
compounds present in the effluent are then decomposed and utilized by soil
organiszz~s nn
the drainfield or mound as the effluent moves (percoiatcs) through the
underlying soil
profile.
The average life of a conventional on-site wastewater treatment (septic tank
and
drainfleld. or mound) system is typically only seven to ten years. A failing
septic system
can lead to public health concerns and non-point source pollutxoz~. Another
related
concern is the difficulty of quickly and accurately assessing whether the
underground
septic system is functioning properly. If the conventional system is not
functioning
properly, untreated, hence polluting, wastewater is likely being released into
the
ecasystezxx with little or no surface indication.
A primary concern with any on-site septic system or wastewater treatment
system is to
ensure that nutrients and other pollutants are removed from the wastewater
before the
wastewater enters a surface or subterranean body of water.1f the treated
wastewater is
not sufficiently pollutant-free, the effluent will create water quality
problems by
contaminating surface or subsurface bodies of water.
CA 02372331 2004-03-12
Amended 4
The ability of wetland plants to remove pollutants from wastewater is known.
To this
end, natural wetlands have been used as wastewater discharge sites for a long
period of
time. Thus far, however, constructed wetlands have made only limited use of
the
potential of wetland vegetation to purify (detoxify) wastewater.
Existing constructed wetlands, including both surface and subsurface flow
systems,
utilize only wetland plants and atmospheric diffusion to transfer oxygen into
(oxygenate)
the wastewater being treated (the water column). These naturally aerated
(aerobic) zones
support populations of oxygen-requiring bacteria. Other areas within the
constructed
wetland, which are not oxygenated, are anaerobic and support populations of
bacteria
which do t<ot require oxygen. It is known that aerobic metabolic pathways are
much more
efficient than anaerobic pathways in decomposing certain types of pollutants.
w w w ~ ~ Consequently, aerobic bacteria are capable of consuming; and thus
removing, more w
pollutants than anaerobic bactezia for a given treatment cell size.
Tn existing constructed wetlands, aerobic zones are typically found only at
the top of the
water column and in the immediate vicinity of wellax~d plant roots. The top of
the water
column is usually a region where there is sufficient gas exchange, via
atmospheric
diffusion. In the immediate vicinity of wetland plant root hairs, oxygen--
~translocated by
wetland plants into their root systems--diffuses out through the mot
membranes. These
naturally occurring aerobic zones occupy only a small portion of the wetland
liquid
volume. Thus, the ratio of aerobic activity to anaerobic activity is usually
extremely small
CA 02372331 2004-03-12
Amended 5
in natural wetland systems. This lack of aerobic capacity thus limits the
overall treatment
capacity of the wetland, parkicularly in subsurface flow constructed wetlands.
F1G. 1 depicts a conventional on-sitE septic system, and FIG. 2 depicts a
constructed
wetland treatment system. In >~ZG. 1, the conventional, on-site septic system
is depicted
generally at S0. The eanventional system 50 includes a sewer line 52 conveying
sewage
from a house 54 to a septic tank 56. in the septic tank Sd, the solids are
allowed to settle
gut of the sewage. The separaCed liquid wastewater effluent flows from the
septic tank 56
to the drain~~eld (or mound) 58 via a sewer line 59. In the septic tank S6,
the wastewater
is treated to a limited extent when compounds present in the settled solids
and effluent
undergo predominantly anaerobic decomposition. However, levels ofpollutants
present
in the wastewater being conveyed from the septic tank 56 are usually too high
for direct
rclcxsc into the environment ~(e:g., direct release into a body of water such
as a streaxo,; ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ - w
lake, or aquifer}. The anal disposal and treatment of wastewater occurs in the
drainfield
5$, which includes a series ofpcrforated pipes 60. Thus, the wastewater is
conveyed by
the sewer line 59 from the septic tank 56 to perforated pipes 60 within the
drainfield 58.
The partially treated wastewater seeps from the perfprated pipes 60 into the
soil profile
underlying the draintield 58. In the underlying soil profile, the wastewater
effluent
undergoes a Fugal series ofpurification steps as it percolates predominately
dawn as
discharge 62 through the soil profile.
These purif canon steps arc accomplished by soil organis~,ns--mostly soil
nucroflora.
CA 02372331 2004-03-12
,Axz~ended ~
Thus, whether the wastewater effluent will ultimately be purified to an
acceptable level
before entering a body of water depends on the ability of the soil profile to
accommodate
the liquid flow and to harbor soil microtlora. The texture of the soil profile
must permit
the wastewater to enter the soil profile from the perforated pipes 60 and
percolate
generally downwardly, e.g., without pooling the wastewater. Soils with high
levels of
clay or organic matter generally knave low capacities to hydraulically convey
wastewater
in this respect. Coarse textured soils have higher proportions of sand and
silt particles and
possess higher degrees ofhydraulic conductivity. The discharged wastewater
(discharge
52), whether or not adequately treated, percolates down to aquifers or can
also be
conveyed somewhat laterally into exposed bodies of water G4. Thus, one
limitation of the
convezltaonal system depicted in FIG. 1 is that the drainfield 58 cannot be
located within a
specified distance from to a surface body of water or cannot be used at all if
the water
,. . .. . . .. ... able {aquifer)wnderlyiu~g the drainfield or mound is-
sufficiently high. Another . . , ,... . . .. . . . ., ..... ..
disadvantage of the system 50 is that the soil profile underlying the
drainficld 58 will
slowly lose its hydraulic conductivity. The loss of hydraulic conductivity is
due to such
factors as unsettled solids conveyed by the wastewater, soil bacteria,
substances
associated with soi I bacteria (e.g., polysaccharides), and solidified
wastewater
components. These substances slowly fill the spaces (pores) between the soil
particles.
When these pares become filled, the soil becomes incapable of conductizxg the
wastewater through the soil profile and the wastewater cannot be exposed to
the soil
bacteria. In time, the conventional disposal system 50 will fail to purify the
sewage and
will itself become a source of pollution. present remedies for failed disposal
systems of
CA 02372331 2004-03-12
Amended ?
this nature include replacing and/or relocating some or all of the components
(e. g., the
drainfield), "resting" the system by discor~lizruing disposal system use for a
period of
time, and treating the soil with chemical agents. Discontinuing use ofthe
disposal system
is often eat feasible. Treating the soil with chemical agents has not been
effective in most
situations. Thus, the expensive process of replacing and/oz relocating
underground
components is often the only feasible method of restoring a functional septic
system.
fl,G. 2 depicts a sewage disposal system 70. The sewrage disposal system 70 is
similar in
concept to the conventional system 50 of FIG. 1, but includes a wetland cell
72 and a
chemical absorption tank 74. In the system 70, sewage from the house 54 is
conveyed to
the septic tank 56 via the sewer line ~2. Im the septic tank Ss, solids settle
out of the
sewage and the separated wastewater effluent is then cozweyed froze the septic
tank 56 to
w ~ wthe~wetland~ccll~72~by-line 59. While the wastewater is present in
the.wetland~cell-72;- w w ~ a ~-~°-~ ,. ." ,
many of the pollutants therein arc decomposed by mostly anaerobic tnicroflora
and
wetland vegetation 76. The wetland vegetation 76 also removes sonic of the
inorganic
pollutants (e.g., nitrates, phosphates, pota.SSium) as plant nutrients. From
the wetland cell
72, the partially treated wastewater is then conveyed to the chexz~.i.cal
absozption tank 74.
T'he chemical absorption tank 74 usually contains minerals such as limestone
or other
substances (e.g., activated charcoal, kiln-fired clay beads, wollastonite,
taconite tailings)
with high surface areas and absorptive characteristics to further remove
undesirable
compounds from the wastewatez being treated. The fluids are then discharged
from the
chemical absorption tank 74 directly into the environment if pollutant levels
are within
CA 02372331 2004-03-12
Amended 8
acceptable limits. Alternatively, the fluids from the ehc~nieal absorption
tank 74 may be
conveyed to a drainfield 58 as described above for further purification by
soil microflora.
Because of the low amount of aerobic habitat present, the disposal system 70
has a
disadvantage of relying primarily on anaerobic microfloz-a in the septic
tattle 56 and the
wetland cell 72 to decompose undesirable compounds. Another disadvantage oaf
the
disposal system 70 is that the wetland cell 72 is exposed to the atmosphere
and, hence,
subject to being frozen during winter months. When frozen, the entire system
70 becomes
inoperative. Moreover, the roots of the wetland vegetation 75 rnay be injured
or entirely
killed if sufficiently low temperatures occur for significant periods of time.
Accordingly, it would be desirable to more fully utilise the pol lution and
nutrient-
w w- w ~ ~- w w ~ ~ reducing characteristics of wetland plants ~in-a
constructed system to treat pol lasted water, - w w w-~° ~~ w
the system incorporating a better efficiency of increased. aerobic microbial
habitat and
preferably remaining operational during lower winter temperatures.
SUMMARY OF TIaIE 1NVENTrON
The present invention provides a safe, efficient, and cost-efFective manner
ofreducing
2U pollutant levels in water or other fluids.
One preferred embodiment of this invention includes a substantially
impermeable
CA 02372331 2004-03-12
Amended 9
primary trealxnent cell and an optional secondary treatment cell. The primary
treatment
cell includes a forced aeration system. A i3uid level control system, such as
a dosing
siphon, may be in fluid communication with the primary treatment cell and the
secondary
treatment cell (if the secondary treatment cell is present). The substantially
impermeable
primary treatment cell includes a bed medium such as gravel, a mulch layer,
wetland
vegetation rooted in the bed medium and extending through the mulch layer, and
a forced
aeration system. 'The secondary treatment cell may be substantially permeable
to allow
treated wastewater within to egress by infiltration and may further contain a
bed medium
for further removal of pollutants. The dosing siphon lowers the level of the
wastewater
being treated in the primary treatment cell so that lower wastewater levels
are present for
a sufficient amount of tizxxe to stimulate deeper, more pervasive root gowth
within the
bed medium. The lower water levels also provide atmospheric oxygen to, and
thereby
........,........... . . ......>s~ulatc the ~owth
of,~aerabic~bacteria:~The'farced-aeration system ~establushes ... ... . _. . .
......... ...... .. ,..... ...
altema.ting aerobic and anaerobic zones within the substantially hozazontaJ fy-
i~owiz~g
wa.~tewater being treated in the primary treatment cell so that wastewater in
the
substantially Horizontal flow is exposed to aerobic and anaerobic zones for a
significant
period of time. By being exposed to bath aerobic and anaerobic zones for a
significant
period of time, the decomposition of pollutant eompoua~ds occurs snore rapidly
and
completely than ifpredominantly anaerobic zones were present.
It is an object of this invention to provide a constructed subsurface flow,
wetland system
that can be used cflticicntly, effectively and safely to remove pollutants
from wastewater.
CA 02372331 2004-03-12
Amended 10
It is a fiwther object of this invention to provide for a calculated variable
water level
management of wastewater in the constructed wetland subsurface treatment
system to
promote faster establishment ofwetiand vegetation, to promote thicker and
deeper root
grawt6 of the wetland vegetation, and to thereby promote more effective
pollutant
removal processes.
It is yet another object of this invention to provide a substantially
impermeable
constructed wetland cell for treating wastewater which is characterized by a
generally
1 Q vertical and unsaturated wastewater flow in a preferred embodiment. The
wetland cell
may include a bed medium, a wastewater supply system, a wastewater retuz~
system, a
forced aeration system, and a multiplicity ofplants. The wastewater supply
system may
"" ~ ' "' w w w be'confzgmed to~ deliver~the wastewater proxiunate an upper
portion ofthe~b~ed~medium: ~ w ~ . .~
At least a portion of the wastewater return system may be disposed proximate a
lower
portion of the bed medium. The multiplicity of plants may be rooted in the bed
medium.
In this constructed wetland cell, the wastewater flows generally vertically
downward
frarn the wastewater supply system, through at least a portion of the bed
medium, and is
conveyed from the wetland cell via the wastewater return system. The
wastewater supply
system, the wastewater return system, and the bed medium may be further be
configured
and disposed such that an unsaturated flow conveys the wastewater from the
wastewater
supply system, through at least a portion of the bed medium, to the wastewater
return
system. The wetland cell may further include an air source for increasing the
oxygen
CA 02372331 2004-03-12
Amended 11
supply vtrithin the constructed wetland cell. A forced aeration {air supply)
system may be
present and may include a blower and pipes with perforations. The perforated
pipes may
be disposed proximate a bottom portion of the bed medium and the blower may
force
atzx~ospheric air through the pipe perforations such that the wastewater
becomes
oxygenated while flowing through spaces in the bed medium. The wetland call
may
further include a layer of substantially decomposed mulch overlaying the bed
medium.
The substantially decomposed mulch may comprise peat.
Zt is a further abject of this invention to provide a system, for treating
wastewater, the
system including a forced aeration (air supply) system, a constructed wetland
cell, and a
disposal system. The air supply may be configured to increase oxygen
concentration in
the wastewater being treated by aspirating air into the wastewater. The
constructed
...,.. ,...... .._..,. .. ...__._.wctland cell-may include' a
bedwmcdium;~awvastewater supply system; a wastevcraterreturrn .. ._.. ~. ~
........._
system, and a multiplicity of plants. At least a portion of the wastewater
supply system
may be disposed proximate an upper portion of the bed medium. At least a
portion of the
wastewater return system may be disposed proximate a lower portion of the bed
medium.
The plants may be rooted in the bed medium and extend through the mulch layer.
The
disposal system may receive treated wastewater from the constructed wetland
cell. T.he
system rn~ay further include a substantially decomposed xxzulch layer (e.g.,
peat)
overlaying the bed medium. The system may yet further include a structure
vsrith a
chamber for separatiu,g solids from the wastewater, such as a septic tank. A
substantial
portion of the solids are; ideally separated from the wastewater before the
wastewater is
CA 02372331 2004-03-12
Amended 12
conveyed to the constructed wetland cell. The system may still further include
a filter
tank receiving wastewater from the septic tank and treated wastewater from the
constructed wetland cell. The wastewater from the septic tank and the treated
wastewater
from the constructed wetland cell are blended in the f ltcr tank. The system
may still yet
further include a recirculation tank receiving the filtered and blended
wastewater from the
filter tank and conveying the filtered and blended wastewater to the
constructed wetland
cell. The system may still yet further include a dosing tank receiving treated
wastewater
from the recirculation tank. The dosing tank may convey the treated wastewater
to a
disposal system. Alternatively, the treated wastewater may be conveyed from
the
rccirculation tank directly to the disposal system.
Another embodiment of the present invention includes a structure with a cavity
for
.., ... :..,. .........._.._..:~..se~~g.lids.from~sewage~and-awecirculation
chamber~iwfluid-co~nmunicatiawwith.said~... ,.. .. .. ... .. , .. ,.
cavity. A pump and aspirator are present. The pump pumps the wastewater from
the
recirculation chamber through the aspirator, thereby increasing the dissolved
oxygen
concentration in the wastewater. From the aspirator the wastewater is conveyed
to a
substantially impermeable wetland cell, The wetland cell may include a bed
medium, a
wastewater supply system and a wastewater return system. At least a portion of
the
wastewater supply system is disposed proximate an upper portion of the bed
medium and
at least a portion of the wastewater return system is disposed proximate a
lower portion
of the bed xn~edi um. The oxygenated wastewater is pumped from the pump and
aspirator,
through the wastewater supply system, to an upper portion of the bed medium
and
CA 02372331 2004-03-12
Amended X 3
allowad to flow substantially vertically through the bed medium. When the
wastewater
arrives at a lower porn on of the bed medium, it is conveyed away from the
wetland cell
by the wastewater return system to the rccirculation chamber, In the
recirculation
chamber, treated wastewater from the wetland cell is blended with untreated
wastewater
from the scaling cavity. The blended wastewater may be cyclically rooted to
the wetland
cell or conveyed to a disposal system.
Yet another embodiment of the present invention includes a structure with a
wetland unit
and an anaerobic, fluid-impermeable unit, optionally integrally formed in an
easily
installed unit. The wetland unit includes a granular bed medium. A mulch layer
is
optionally present overlaying the medium and vegetation is optionally rooted
in the
medium. The an~aerobxc unit is optionally positioned beneath the wetland unit
and may
__. . .... .... ......._....fo~. flrstand~second'uhambers: The~first-
chamber~accornmodates-an-inlet; a mixing.:......_.._,.......__.. , ... .... .
device and a filter. The mixing device znay possess a large surface area to
provide habitat
for anaerobic rnicroflora. The filter removes particulates from the wastewater
as the
wastewater is conveyed from the first chamber to.#1=a second chamber. A
pump.:xra~~be.-....._._.. . . ......... .._
operationally present in the second chamber to convey wastewater to the
wetland unit.
The pump may be considered as part of a wastewater supply system. An aerator
is
optionally present in the conduit between the pump and the wetland unit. The
pump also
conveys wastewater to an outlet. Operationally, the pump conveys wastewater,
via the
wastewater supply system to an upper portion of the bed medium. Lf the aerator
is present
the wastewater is aerated when being puxnped frozx~, the second chamber to the
wetland
CA 02372331 2004-03-12
Amended 14
unit. After being conveyed from the wastewater supply system, the wastewater,
in a
substantially vertical and unsaturated flow, flows through the bed medium to a
lower
portion thereof, where it is ttae~~ coxxveyed to the mixing device in the
first chamber. The
wastewater is aerated while flowing through the bed medium and is aerobically
treated
during the substantially vertical, unsaturated flow through the bed medium.
The mixing
device is positioned to receive exogenous wastewater from the inlet and
treated
wastewater from the wetland unit and to z~nix the two wastewater flows to
enable
anaerobic or anoxic decomposition of wastewater pollutants in the first and
second
chambers. The wastewater is cyclically conveyed: from the first chamber to the
second
chamber, from the second chamber to the wetland unit, and from the wetland
unit to the
first chamber. In the first chamber, the treated wastewater from the wetland
unit is mixed
with exogenous wastewater. The wastewater is also pumped from the second
chamber to
"w' ~ ~ ~ ww " "~ an-outlet when the' wastewater~has
beews~afficiently~treatcd: Altcrnatively,~thc wastewater -- °-- ~- ~ w
~° w ~~
is pumped from the wetland unit to the outlet without being mixed with
exogenous
wastewater.
These and other objects, features, and advantages of this invention will
become apparent
from the description, which follows and when considered in view ofthe
accompanying
figures.
BRIEF DESCRIPTION OF THE DRAWI1~FGS
CA 02372331 2004-03-12
Amended 15
FIG. 1 illustrates a conventional on-Site septic System;
F'IG. 2 depicts a wastewater disposal system with a constructed wetland and a
chemical
absorption tank;
1~1G. 3 is a side, cross-sectional view ofa subsurface wetland treatment
system of this
invention with primary and secondary treatment cells;
FIG. 4 illustrates a plan view of one embodiment of the primary treatment cell
of FIG. 3;
FIG. 5 is a fragnnentary cross-section of the primary treatment cell of FIG. 3
wittx one
embodiment of a forced-air aerator;
F1G. 6 is a fragmentary crossrsecHoti of the primary treatment cell of FIG. 3
with an
1 S alternate embodiment of the forced-air aerator of FIG. 5;
FIG. 7 is a graphic representation of air temperature vs. system temperature,
illustrating
the insulating effect of the present mulch layer;
j 20 F1G. $ is a fragmentary view of the primary treatment cell of FIG. 3;
s
I
s
F1G. 9a depict cross-sections of the primary treatment cell of FIG. 3, a
dosing chamber,
CA 02372331 2004-03-12
Amended 1 b
and an alternate embodizzaeot of the present secvndazy treatment cell;
FIGS. 9b, 9c, and 9d illustrate principles of operation of one embodiment of a
dosing
siphon used in the present invention;
FIG. 10 depicts another embodiment of the present fluid level control system;
FIG. 1 i is a comparative illustration, of tlxe effect of aez~ation on root
depth;
FIG. 12 is an alternate embodiment of the present invention, illustrating an
extension of
the infiltration area bareath the primary treatment cell;
w °° FIG: 13 illustrates the~dosing-chamber-of the present
invention dirECtly conncctcd~to~aw
draxx~fiel.d;
FIG. 14 is a diagram of an alternate ennbodiment of this invention including a
substantially impermeable constructed wetland cell, the wetland cell providing
for
' vertical, unsaturated wastewater flow therethrough;
2d FIG. 15 is a fragmentary cross-section of the wetland cell of FIG. 14;
1~IGS. lfia, lbb, and 16c are fragmentary cross-sections of the v~retland cell
of FIG. 14
CA 02372331 2004-03-12
Amended I7
depicting the wastewater return system, the air supply system, and the
wastewater. supply
system, respectively;
FIG. 17 is a cross.-section depicting another embodiment of a vertical flow
wetland cell
disposed atop a tank with a settling compartment and a rccirculation
compartment;
FIG. 18 is a cross-section depicting the vertical wetland cell and
recirculating chamber of
FIG. 17;
FTG. 19 i s a plan view of the vertical flow wetland unit of FIG. 17 showing
the
wastewater return system thereof;
w' ' -' - ' ' w -w- FICr. 20 is ~a plan view -of tk~ewertical~ flowwetland
unit of FIG: 17; depicting a portion-of - ~ - ~ -. ...... _. . . ,
the wastewater supply system thez'eof; and
FIG. 21 is a cross-section depicting yet another embodiment of a vertical flow
wetland
cell disposed atop an aerobic unit.
DETATLED DESCRIPTION OF THE INVENTION
2l?
Tn a first erx~bodirnent, this invention provides a subsurface constricted
wetland system
which substantially increases the presence of aerobic zones within the
treatment bed. The
CA 02372331 2004-03-12
Amended 18
enhanced aerobic habitat promotes enhanced and more pervasive mot growth and
stimulates growth and development of aerobic microflora for more effective
wastewater
effluent treatment. 'fhe wastewater flow is preferably saturated and
substantially
horizontal in this first embodiment. In another embodime~~t the provided
wekland is
configured for a substantially vertical and unsaturated wastewater flow
therethrough.
The terms "wastewater" and "efi~luent" are conterr~plated to describe water in
which
environmentally undesirable compounds are presezlt. xhus, the terms wastewater
and
effluent include without limitation, substantially liquid portions of
sol.utians, mixtures,
1.0 and suspensions of water and substances considered as pollutants by
persons of ordinary
skill in the art. Concentrations or titers of these substances must be reduced
during
wastewater treatment before the treated wastewater can be safely released into
the
.. ... . . . .. _._ . ..~~~~r. ~~ns of these-wastewaters or effluents include
industrial; domestic~and~ . ...... ... .. , .... .. ..
municipal sewage, wastes, and the like. The term "sewage" is contemplated to
include the
15 above-described solutions, suspensions, and znixtwes, vuhieh contain solids
which can be
separated to sonic extent by settling. Some compounds are almost always
considered
pallutants. Other compounds are considered pollutants only under certain
circumstances.
One embodiment of the present system for removing pollutants fram wastewater
is
20 depicted in FIG. 3, generally at 140, and includes a primary treatment cell
(reactor) 102, a
secandary treatment cell (reactor) 104, and a fluid level control system, such
as a dosing
siphon 106 preferably disposed within a cement dosing chamber 108.
CA 02372331 2004-03-12
Amended 19
The primary treatment cell 102 includes an excavated basin 112 lined with an
impermeable liner 114. Suitable materials for the impermeable liner 114 will
ensure that
wastewater present in the primary treatment cell 102 will not leak into the
soil
surrounding the basin 112. These materials include synthetic resins such as
polyethylene,
polyvinylchloride, and polypropylene sheeting. Alternatively, a cement basin
coated with
a waterproof (e.g., bitumenous) material may be used.
An inlet 116 arid an outlet 118 extend through the imperxrteable liner 1 l~tr.
A portion of an
aerator system 119 extends generally transversely to a linear dimension 119.1
between
the inlet 116 and the outlet 118 in this embodiment (FICx. 4), so that the
substantially
horizontally flowing wastewater being treated in the primary treatment cell
will flow
._......... . . ..... y .ough zones iz~ which forced aeratiow is occurring:
~.. ... . . .., ._.. . ... .. ......., .. . . .._ . ... ._. _ _ .. .. . . .. _
.. .._.
t 5 Returning to FIG. 3, a bed medium 120 fills the basin 112 generally to a
level above the
inlet 1 i 6 and to a specified interval below the surface 121 of the soil in
which the
primary treatment cell 102 is disposed. A mulch layer 122 overlays the bed
medium i2U.
Wetland vegetation 124 is rooted in the bed medi um 120 and extends (grows)
through the
mulch layer 122 in this embodiment. The depth of the basin 112, while
typically between.
about 12 to 24 inches, may be practical up to a depth of about 24 feet. Other
factors,
discussed below, may make depths greater than about 24 feet impractical. The
volume of
the basin 112 in part detexuzines the capacity of the primary treatment cell
102 to purify
CA 02372331 2004-03-12
Amended 20
wastewater. Thus, the volume of the primary treatment cell i 02 may vary to
accommodate differing amounts of wastewater to be treated and different
concentrations
and types ofpollutants to be removed from the wastewater. For example, up to
about 600
gallons per day of domestic sewage is often generated by a four bedroom,
single family
dwelling. Adequately treating the wastewater from this amount of sewage would
typically require an embodiment of the present primary treatment cell with a
capacity of
about 10,000 cubic feet. However, an equal amount of vcrastewater that is more
diffcult to
treat, such as from a dairy or slaughterhouse, might require a primary
tI'eatment cell
capacity of about 27,500 cubic feet at the same flow rate. An inlet seal 12G
and an outlet
seal 12$ are used to insure that wastewater leakage will z~ot occur from the
primary
treatment cell 102 where the inlet 116 axed outlet 11$ extend through the
liner 114. Thcsc
holes in the liner 114 accommodate the inlet 116 and. outlet 118 and are
typicaEly slightly
w ~ ~ ~ ~ ~ smaller than. the outer diameters of the inlet'116' and ?hc outlet
118: Thc~inleC 1-16 and °w ~ °w ~ ~ ~ °a
outlet 118 are forced through these holes. The seals 125 and 128 are
constructed to
provide an impermeable barrier to fluid escape. Sutabie materials for inlet
and outlet
seals x26 az~,d 128 inchlde adhesive mastic. Tl~e inlet 116 and the outlet I
I8 may be made
from such materials as schedule 40 polyvinylchloride {PAC) or metals such as
cast iron.
While the dimensions of the inlet 116 and the outlet 118 may vary, outer
diameters
between about four inches and six inches have been found to be suitable for
many uses.
f'unetionally, the spaces between the bed medium 120 particulates accommodate
the
mots 130 of the wetland vegetation 124. The bed medium particulates provide an
external
CA 02372331 2004-03-12
Amended 21
surface area, tlxereby .habitat, for growtbt anal developrxlent of the
microffora within the
primary treatment cell 102. The specific materials used to make up the present
bed
medium, therefore the type of microflora found proximate the bed medium, may
be
specific to the types of pollutants to be removed from the wastewater.
However, one
general requirement is that the surface areas of bed medium particles should
be
maximized within limits. Gravel is often a preferred bed medium because of its
inexpensive cast and generally adequate surface area. By way of illustration
and not
limitation, average maximum cross sectional dimensions (e.g., diameter) of
gravel
suitable for the present bed medium may be between about one inch and two
inches,
between about 1/2 inch and one inch, and between about 1/4 inch and 3/4 inch.
Although
gravel is often a preferred medium for treating certain types of wastewater,
the use of
gravel should not be deemed limiting. It is known that certain types of other
materials are
.. ....... , ...........~v~~~us when-dealing with specific water
pollutiowproblenns: For example; using a-....,, , . . _..__ ,.. .,
bed medium containing soluble forms of calcium or magnesium (e.g.,
linriestozze) is
beneficial to neutralize wastewater with an acid pH (acid mine drainage). It
is also
anticipated that certain types and shapes of synthetic media may be desirablE
under
certain circumstances. For example, these synthetic media may include
spherical plastic
beads. It ie also possible to create clay pellets, which are kiln-fired in a
zna~aner to make
them stable in water. These kiln-fired clay pellets may be used as a bed
medium, e.g., as a
gravel substitute. It is further anticipated that the type of clay used could
be specific to
the type of pollutants being removed (i.e., phosphorous removal by taconite or
other iron-
containing materials). It is additionally anticipated that certain materials
could be added
CA 02372331 2004-03-12
Amended 22
to the clay pellets during manufacture to further enhance the pollutant
removal capability
of the present bed medium. h'or example, clay and sawdust mixtures could be
used to
form medium particulatcs. Kiln-firing would eliminate the sawdust to produce
hardened
ci.ay pellets with increased porosity and surface area due to the pores
created when the
sawdust was burned away. Tt is also anticipated that certain types and shapes
of synthetic
media may be desirable under certain circumstances. Exemplary media might
contain
intersecting, often arcuate, polyethylene ribs (fins) for increased surface
area. Suitable
such media include "Tripack.TNl." from Jaeger Products, Inc., Houston, Tex.
and "Nor-
)f'ac.TM." from NSW Corporation, Roanoke, Va.
As stated above, one function of the present bed medium 120 is to provide
surface area,
therefore accommodate or harbor, microflora which break down pollutants in the
..... ... .. .... .... .. . .~,~tewatcr being treated:~These~microfloral
organisms ixtclude bacteria; fungi; and , ~ _.. . ,. ,..... . . . ._
actinomycetes. Without wishing to limit the present invention to any specific
theory, the
bacteria are considered to perform most of the decomposition and purification
functions
within the present system. Suitable bacteria for these functions include those
from the
taxi Bacillus, Pseudomonas, Nitrobacter, Nitzosomonas, Cellalomanas,
Aerobacter,
Rhodopseudomonas, and Anabacna.
These and other bacteria pcrforrning these functions have been further
characterized as
cyanobactenia, anaerobic bacteria, aerobic bacteria, and photosynthetic
bacteria. The roles
played by some of these bacteria in purifying wastewater are more fully
discussed
CA 02372331 2004-03-12
A,z~ezxded 23
hereinbelow.
The forced aeration system of this invention is depicted in FIGS. 3, 5, and 6.
Referring to
FIG. S, the aerator system 119 includes an air pump 140, a system of air pipes
(tubes)
142, and a system of air delivery hoses 144 extending from the air pipes 142.
1n this
ezzr,bodiment, the air pump 140 is electrically operated and may be configured
to either
continuously or intermittently pump air. The pipes 142 are connected to the
hoses x 44 'by
connectors such as T-couplings 14b. In some embodiments, the air hoses 144 are
further
branched by means of connectors such as T-couplings 14$. The pipe 142 may be
suitably
made from schedule 40 PVC or other, more flexible conduits made from synthetic
resin.
In one embodiment, the air hose I44 includes a perforated flexible hose and
multiplicity
of emitters commonly used in drip irrigation. Gcxe exemplary emitter is
disclosed in U.S.
_.. ... __ .: ._... . .. Pat: No. 5,332;160: The present°air
pump~Tnayinclude a-tirner 150 iFintermittenC- .. . ... ...... ,~ . , ~ ..,..
..
pumping is desired. Also contemplated to be within the scope of the present
inventioza is
I S an oxygen sensor 152. The oxygen sensor 152 communicates electrically via
a load 154
with a circuitry 156, which may be present within the pump 14U or located
remotely.
When the oxygen concentration of the wastewater proximate the oxygen sensor
152 is
below a specified first level, the circuitry 156 activates the air pump 140.
When the
oxygen concentration of the wastewater proximate the oxygen sensor 152 is
above
azlotber specified second level, the circuitry 156 deactivates the air pump
140.
Deferring to ~TG. G, an alternate embodiment vfthe forced aeration system is
indicated at
CA 02372331 2004-03-12
Amended 2~L
I58 and is present as a plurality of aeration headers 160. ~acl~ aerati.oz~
k~eader 1 b0
includes an air intake 162 and a bast 164. An air pump {e.g., within the base
164) pulls
atmospheric air through the air intake 1 b2 and expels the air out the base
164 through a
series of orifices {not shown). As the expelled air bubbles upwardly in the
wastewater,
the surrounding water becomes oxygenated in a manner discussed hcrcinbclow. Of
course, timers and oxygen sensors could also be used to control the air pump
in the
aeration header 160.
The mulch layer 122 is depicted, e.g., in FICxS. 3, 5, and 6 as overlaying the
bed medium
14 1.20. The present mulch layer may include a variety of materials. For
example,
substantially decomposed yard waste and peat moss are exemplary natural
substances,
which can be used in the present mulch layer. In one ernbodirncnt, Sphagnum is
a
._,. , . .. _ ,. . ... pleferred~material ~rvrthe mulch layer 122: However;
other types o~ma2erials-may also-be .... . _ . . . , . . . .....
suitable, especially materials which are also substantially decomposed_ It has
been
15 discovered that using natural materials which arc not substantially
decomposed (e.g.,
green wood chips) may actually cause pollutants to be added to, rather than
removed
from, the wastewater being treated by the present system. Because these
undccomposcd
materials are themselves undergoing decomposition within a mulch layer,
decomposition
byproducts can leach into the primary cell and add to the load of compounds
which
20 comprise pollutants. Additionally, the microflora within the present
primary treatment
eel l may be adversely affected by these decomposition byproducts as well. !t
is also
contemplated that the present mulch layer may be a combination of synthetic
and
CA 02372331 2004-03-12
Amended 25
substantially decomposed natural materials. rn one embodiment, the present
mulch layer
includes a mixture of Styrofoam.TM. bits and peat moss.
Among the functions fulfilled by the present mulch layer are enabling gas
exchange and
providing insulation and odor control. For efficient operation of the present
subsurface
flow-constnlcted wetland system, oxygen exchange-via atmospheric diffusion at
the
wastewater surface-should be maximized between the underlying bed medium and
wastewater and the atmosphere. Idenee, it is important that the present mulch
layer not be
so thick as to inhibit this beneficial oxygen transfer. However, the present
mulch layer
must also be suffxcicntly thick to provide insulation so that the underlying
mieroflora and
aquatic plant mot structures arc not injured by cold temperatures and to
provide odor
control as well.
In FIG. 7, a lower line 17p represent air temperature readings taken between
November,
1 S 1997 and March, 1998 at several locations where embodiments of the present
invartion
were installed and used to purify wastewater. The readings were generally
taken in the
morning hours and were representative of tare daily low temperatures during
that period.
The upper graph lines 172, 174, 17G, 17$, and 1$0 represent corresponding
temperatures
of the wastewater present in the primary treatment cells at fve locations at a
depth of
about 1$ inches below the top of the mulch Iayer. These primary treatment
cells were all
located in Minnesota, United States. The mulch layer of each bed was
constructed to be
about l4 uoiches ins depth. After settling, the mulch layer depth was
generally between
CA 02372331 2004-03-12
Amended 26
about 12 and 14 ia~ches. As FIG. 7 demonstrates, the wastewater temperature in
the
primary treatment cells never fell below the freezing point--even when ambient
air
temperatures dropped well below O° F. Advantageously, the present
primary
treatment cell with a mulch layer of about 14 inches provides generally
adequate
insulation, allowing the liquid in the present treatment cell to remain above
freezing in
climates similar to those of Minnesota. Additional studies have demonstrated
that this
mulch layer depth can be reduced to as little as six inches, yet provide
adeauate
insulation. Hence, the znicrodora and wetland vegetative root systems are not
injured by
low winter temperatures and remaixx active, thereby continuing to remove
pollutants fxoan
the wastewater being treated. Of course, greater or lesser mulch layer depths
may provide
sut~icient insulation in other climates.
The present mulch layer must also' have a sufficient depth to provide odor
control.w
Anaerobic decomposition ofpollutant compounds may result in the liberation of
odifczous gases such as hydrogen sulfide (H<sub>2</sub> S) aid ammonia (NH<sub>3</sub>) or
otherwise objectionable gases such as methane (CH<sub>4</sub>). It is known that
bacteria
present in substantially decomposed mulch layers metabolize these
objectionable
compounds into other less objectionable compounds. Thus, depending upon the
requirements of gas exchange, insulation, and odor control, the present mulch
layer znay
be less than or edual to about 24 inches in depth, between about 6 and 24
inches in depth,
between about 6 and 14 inches in depth, between about 14 and 24 inches in
depth,
between about 6 and 12 inches in depth, between about 12 and 24 inches in
depth,
CA 02372331 2004-03-12
Amended 27
between about 6 and 14 inches in depth, between about 12 and 14 inches in
depth, about
14 inches in depth, about 12 inches in depth, or about 6 inches in depth.
The present wastewater treatment system advantageously includes a wetland
vegetative
population 124 rooted in the bed medium 120 and extending (growing) through
the
present mulch layer. The wetland plants used in the present invention may be
varied, the
composition depending upon such variable factors as latitude (or altitude),
the amount
and types of pollutants present, and desired aesthetic appearance. The
latitude andlor
altitude at which the present system is to be installed will in part determine
which
wetland plant species will be adapted the locale, e.g., how much tolerance to
cold/hot
weather is required. ,Another factor for selecting appropriate vegetation is
the specific
root growth habitat desired. The preferred wetland vegetation has .roots 130
wlaiclx will
- ~ w w 'grow underwater in the bed medium to encompass substantially the full
extent of theca - w ~ - ~ w ~ -
primary treatment cell 102, especially when the present primary treatment cell
includes a
i 15 forced aeration system. The depth and invasiveness of the vegetative root
structure 130 is
axx xnaportant factor in promoting efficient and effective pollettion removal.
FIG. 8 depicts a fragmentary cross section of a portion of the primary
treatment cell 102.
As can be Seen, the impermeable liner 114 extends circusnFerentially around
the
subterranean portion of the primary treatment cell I02. The inlet 116 enters
the present
primary cell generally at a generally upper location. The amount of
waa'tewater in the
present primary treatment cell is regulated to ensure that a maximum
wastewater level
CA 02372331 2004-03-12
Amended 28
184 does not rise above the inner diameter of the inlet 116 to prevent
backflow of
untreated water. A vertical treatment zone I86 is considered to extend from
the bottom
187 of the present primary treatment cell to the wastewater level 184.
The wetland plants 124 enhance the treatment of wastewater in several ways. As
wastewater being treated flows substantially horizontally through the present
primary
treatment cell, bacteria proximate the surface of the bed medium 120 remove
pollutants
from the wastewater. Oxygen diffuses from root hairs into a portion of the
wastewater in
the primary treatment cell 102. Compounds present in the wastewater, often
produced by
bacterial action, arc then taken up by the vegetation as nutrients to produce
plant biornass.
Moreover, large quantities of water can be removed from the primary treatment
cell by
evapotranspiration. The wetland vegetation 124 also secretes enzymes and other
exudates
- w~ www ~ w whcwmetabolizing pollutant cvznpounds or obtaining trace
nutrients. These exudatss ---° w
often promote decomposition of these pollutant compounds. Moreover, the
preseztt
wetland plants 124 arc often in a symbiotic relationship with mycorrhizal
fungi to further
facilitate many chemical reactions necessary for the growth and development of
these
wetland plants and decompose pollutant compounds.
By way of illustration and not limitation, suitable wetland vegetation is
contemplated to
include species which are adapted to the present generally saturated primary
cell. Suitable
wetland species may include at least some species within the genera Andropogon
spp.,
Acorus spp., Asclcpias spp., Aster spp., Carex spp., Comus spp., Eleocharis
spp.,
CA 02372331 2004-03-12
Amended 29
Heliopsis spp.,lris spp., luneus spp., Lcmna spp. Phalaris spp., lshragmites
spp., Popuius
spp., Potamogeton spp., Ratiba spp., Rudbeckia spp., Sagittaria spp. Salix
spp.,
Schoenoplechis spp., Scirpus spp., Solidago spp., Spaztina spp., and Typha
spp. Suitable
species include Scirpus atrovirens, Acorns, calamus, Asclepias incarnata,
Aster novae-
anglac, Avicennia nitida" Alnus glutinvsa, Bolboshoenus rnaritimus, Canna
flaccida,
Ceratophyllum submersium, Carex gracilescens, Carex acutiformis, Colocasia
esculenta,
Cozxm..5 stolonifera, Cyperus alternifolius" Eleoeharis dulcis, Eleocba~ris
sphacelata,
Crlyceria znaxizx~a, Heliopsis helianthoidcs, Hydrocharis morsusranae, Iris
pseudacorus,
Iris versicolor, .fuxlcus subnodulus, Myriophyllum spictaturn, Nyssa
sylvatica, Phalaris
arundinacea, Phragmites australis, Phragmites communis, Potamogeton
pcctinatus,
R.atiba pinnata, Redbeclda hirta (serptina), Sagittaria latifolia,
Schoenoplectus lacustris,
Scirpus lacustris, Scirpus cyperinus, Scirpus rubricosus, Scirpus
pedicellatus, Scirpus
._.. , . . longii; Scirpus robustus;-Scirpus~validus; Scirpus pungens,-
Solidago rigida; ~Spargium.........". .......-. ............ ..
erectum. Spartina altenaiflora, Spartina pectinata, Strativtes alflides,
Taxodium distichum,
Tricularia vulgaris, Typha angustfolia, Typha latifolia, Typlaa domingensis,
Typha
orientalis, Typhoides arundiaseae, and Za,ntedeschis aethiopica. However, it
is
understood that the scope of this invexition is contemplated to include any
suitable
species, whether or not the roots require wet or saturated soils.
Returning to FIG. 3, one embodiment of the present fluid level cantral system
is the
dosing siphon 106 and dosing chamber 108. This embodiment of the dosing siphon
106
includes a siphon bell 190, a siphon bell vent 192, a siphon leg (trap) 194,
and a siphon
CA 02372331 2004-03-12
Amended 30
discharge pipe 196. Other dosing siphons may include a vent and over!-low (not
shown)
in fluid communication with the discharge pipe 19b. In the embodiment depicted
in FIG.
3, the dosing siphon 106 begins to discharge wastewater from the dosing
chamber 108
when the wastewater level reaches the top 198 of the siphon bell 190 and
continues to
discharge wastewater until the wastewater level reaches the bottom 199 of the
siphon bell
190. Thus, the minimum and maximum wastewater levels within the present
primary
treatment cell can be determined'by a siphon bell vertical dimension, such as
the distance
from the top to the bottom of the siphon bell 190. Howevex, persons of
vrdiu~ary slall in
the art will recognize that other minimum and maximum wastewater levels are
also
possible with respect to the present dosing siphon.
For example, in FIG. 9a, another embodiment of the present dosing siphon is
depicted at
' ° ~ w ' ~ ~ ' ~ w~ 200 and includes a siphon bell 202, a siphowbell
vent 204, a~siphon-leg (trap) 206; ~and~a ° w
siphon discb~arge pipe 208. The dosing siphon 200 is configured to begin
discharging
wastewater from the dosing chamber x08 when a high wastewater level 210 is
reached
within the dosing chamber 108. The dosing siphon 200 continues discharging
water from
the dosing chamber 108 until the wastewater in the primary treatment cell
reaches a low
fluid level 212. This low fluid level 272 may coincide with the lowest fluid
level at which
the outlet 118 will drain water from the primary treatment cell 102.
FIGS. 9b, 9c, and 9d further illustrate how treated wastewater levels in the
present
primary treatment cell may be controlled by the dosing siphon 200. In FIG. 9b,
the
CA 02372331 2004-03-12
Amended 31
treated wastewater level 212 represents the fluid level in the dosing chamber
10$ and bell
202 at the lowest portion of the outlet 118 opening. The treated wastewater
levels 212.1
and 212.2 in the siphon leg 206 are at lower levels than the level 2l2 because
the
discharge pipe discharges treated wastewater until the levels are as shown.
The level of
treated wastewater in the siphon chamber 108 has a maximum level 210. During
the rise
ire the treated wastewater level, the bell vent 2(?4 is closed off by the
wastewater such that
air cannot enter the bell vent 204. As the wastewater level rises, the water
inside the
siphon bell 202 becomes increasingly pressurized. As the treated wastewater in
the
siphon bell 202 becomes more pressurized, the wastewater therein rises to
level 212.3
and the treated wastewater level in the dosing trap 206 lowers to level 212.4.
Finally,
when. the treated wastewater level rca.chcs the maximum level 210, pressure
forces the
treated wastewai:zr in the siphon bell 202 into the trap 206 and the treated
water is
_ _.. _...... ...., .. . ....... _.syphoned out the discharge pipe 208:
Treatedvvastewater continues to be~ siphoned out ~of ~ ... ... . , ._ .. . . .
_._
the dosing chamber 108 until the wastewater level falls below the vent 204.
When the
treated wastewater level falls below the vent 204, the vent becomes exposed to
air. The
air enters the vent 204 and breaks the siphon, thereby discontinuing
discharge.
Thus, the xxzaximum and minimum wastewater levels 210 and 27 2, respectively,
within
the present primary treatment cell may be regulated by altering the dosing
siphon. Stated
otlZerwise and refernng to FIG. 9a, a primary treatment cell vertical
dimension 214 as
reflected by fluid levels in the present dosing chamber may be used to
describe the
distance between the maximum and minimum wastewater levels 210 and 212
regulated
CA 02372331 2004-03-12
Amezzded 32
by the present dosing siphon. Adjusting minimum and maximum levels of
wastewater in
this manner is disclosed in Mote et al., Design and Performance of PVC Dosing
Siphons,
Transactions of the ASAE {1983).
The dosing siphon is a passive system regulating fluid levels within the
present primary
treatment cell over time and is in fluid co~oo~xnunicatiox~ witkz the primary
treatment cell
such that the spaces between the bed medium particulates (pore volume)
function as an
extension of the dosing siphon. The fluid level of the primary treatment cell
102 can be
regulated based on the rate of inflow from the inlet pipe 116 and outflow
through the
outlet pipe 11$ as well as by the dimension and capacity of the dosing siphon
in use. The
dosiuag siphon requires nn electricity and has no moving parts, thereby
functioning
economically, reliably, and for a lengthy period of time without maintenance.
The dosing
' ~ ~ ° w w "~ siphon may be~used in liewof pumps if the point of
discharge iswat a-lower elevation-thaw ~ '
the outlet of the primary treatment cell, thereby eliminating the need to
transfer liquids by
using mechanical pumps.
Dosing siphons may be made from such materials as cast iron, fiberglass,
polyethylene,
and polyvinylchloride (PVC) (e.g., schedule 40)_ Cast iron dosing siphons arc
subject to
corrosion. Fiberglass siphons do not corrode, but usually must be fastened in
place
because of their Iight weight and buoyancy. The design of the primary
treatment cell may
accommodate one or more dosing siphons to advantageously transfer treated or
partiatly
treated wastewater from the primary treatment cell to, e.g., the secondary
treatment cell
CA 02372331 2004-03-12
Amended 33
in the present system. One suitable dosing siphon is available from Fluid
Dynamics, inc.
of Steamboat Springs, Colo. as model 417.
Referring to F1G. 10, another embodiment of the present fluid level control
systerKx is
depicted as an electric pump 220, which is activated, and deactivated, by a
float 222. The
float 222 may be attached to a wall 22d of the dosing chamber 108 or may be
directly
attached to the pump 220. A person of ordinary skill in the art will readily
comprehend
how to adj ust and locate the float 222 so that fluid levels within the
primary treatment
cell 102 are maintained, e.g., between the upper and lower fluid levels 2x0
and 212,
hence within the primary cell vertical dimension 214.
It is also contemplated that this invention could be constructed with yet
another fluid
w -w-w ° w"~ w w wwlevcl cantrol~ system such as~a standpipe
(not~showrr).'Thc standpipe would then fix~the
water level within the primary treatment cell. Adjusting the water level would
reduire
altering the height of the standpipe or attaching a float valve to the end of
the standpipe.
klowever, unless a float valve or the like were operably present, a calculated
raising and
lowering of the fluid levels within the present primary treatment cell
(described
hereinbelow) would not usually occur if a standpipe were used in lieu of a
dosing siphon
or a mechanical pump.
"The dosing chamber 108 may be impermeable (e.g., include an impermeable liner
228).
Alternatively, if the present primary treatment cell treats wastewater to a
desired extent,
CA 02372331 2004-03-12
Amended 3~
the present dosing chamber may be more or less permeable to allow egress of
treated
wastewater into the soil. The dosing chamber 108 may further include a cover
230 for
access.
The present fluid level control system (c.g., dosing siphon, pump-float
combination)
determines fluid levels within the present primary treatment cell. More
specifically, the
present fluid level control system periodically ideally lowers these fluid
levels to a
desired and predetermined level. This calculated lowez~ing df fluid levels
within the
present primary treatment cell enhances the root growth of tlxe wetland
vegetation withizx
the primary treatment cell. As the fluid level is lowered and slowly xises
over a sufficient
pezaad of time, the root structure of the wetland vegetation grows deeper into
the bed
mediurxA in response to the lower wastewater level. Moreover, the aerobic
bacteria present
' ' -' ' ~ ~ ~ ~ ~ ~ ' ~ at these lower levels~are able to use and store
~atmosphcric oxygen during periods af--w"
lower water levels. These "oxygenated" aerobic bacteria tend to function more
efficiently
once the water levels again cover the bed znediuzzi,. Thus, through controlled
variation of
flW d levels within the present primary treatment cell, propagation of wetland
coat
structure and bacterial decomposition can be optimized, thereby increasing the
effectiveness and efficiency of the present System to remove pollutants from
wastewater.
In a preferred embodiment of this invention, the efficiency of pollutant
removal is also
related to the presence of alternating aerobic zones and anaerobic zones. 'fhe
aerobic
zones are established by any of the embodimentw of the present forced aeration
system.
CA 02372331 2004-03-12
,A.mended 35
Natural, but limited, aerobic zones occur in existing subsurface flow wetlands
by oxygen
transport via passive atmospheric diffusion or o~tygen release from wetland
plant root
tissues. The oxygen released by root tissues is previously traruslocated by
the wetland
plants to the root tissues. However, these naturally occurring aerobic zones
are very
limited in scope and cannot bar themselves support sufficient populations of
aErobic
bacteria for efficient pollutant removal. Thus, it is advantageous, especially
when
nitrogen compounds arc present as pollutants, to construct the present system
with ono or
more alternating aerobic zones 250 and one or more anaerobic zones 252 by
using an
embodiment of the present forced aeration system (FIG. 6). Whereas aerobic
zones have
1 p high oxidation-reduction potentials, anaerobic zones have relatively low
oxidation-
reduction potentials. Thus, alternating anaerobic and aerobic zones can be
extremely
advantageous to pollutant nsmoval.
Treating wastewater with zLitrogenous coznpouzids typically invplves
ammonificativn,
nitrification, and denitrification. Ammonification involves transforming
organic
nitrogenous compounds into inorganic ammonium (NH<sub>4</sub><sup></sup>+) compounds. High
concentrations of ammonium compotuids can be toxic to both plants and
microbes.
However, this transformation is a necessary precursor to subsequent nitrogen
removal
mechanisms. Specitic aerobic bacterial species arc quite efFective in
oxidizing
ammonium compounds into nitrate compounds which can be either taken up by the
wetland plants as nutrients or further used (metabolized or catabolized) by
bacteria. Then,
bacteria in subsequent anaerobic zones denitrify the nitrates. Upon
denitrification, the
CA 02372331 2004-03-12
Amended 36
nitrogen compounds are trazxsformed into nitrogen gas or gaseous nitric oxide
to be
liberated to the atmosphere. Thus, nitrogen is effectively removed from the
wastewater
being purilxed.
Nitrification is considered to be a process of bacterial enzymatic oxidation
and is further
coxxsidered tv be the result of two steps. Each step is hypothesized to be
conducted by a
distinct bacterial group. Without limiting the present invention to any
specific theory, the
first step is thought to be oxidation of ammoniLUn ions to nitrous acid:
2NH<sub>4</sub><sup></sup>++30<sub>2</sub>.fwdarw.2NO<sub>2</sub><sup>--</sup>~2H<sub>2</sub> O+Energy. (1)
In equation (1) nitrous acid is produced by one group ofaerobic bacteria. The
second step
. _ .... .. . is thought to be oxidation of the nitrous 'acid: . . .. . ,. . .
. . . . . . . .
2NO<sub>2</sub><sup>--</sup>~O<sub>2</sub>.fwdarw.2NO<sub>3</sub><sup>-</sup>+Energy. (2)
In equation (2), the nitrous acid is further oxidized into nitrate by another
group of
aerobic bacteria. Collectively, the nitrifying bacteria are called
nitrobacteria. Of these, the
I Nitrosornonas are thought to be izxvolved in tlxe conversion of ammonium
ions into nitrate
2U ions. The bacteria oxidizing nitrites to nitrates are usually designated
Nitrobacter.
However, other organisms, e.g., lzeterotropb.ic bacteria, fungi, and
actinomycetes, are
i probably able to produce nitrate salts by these or other pathways. The
biochemical
r
i
CA 02372331 2004-03-12
Amended 37
reduction of nutrate nitrogen into gaseous compounds is termed
dcnitrifycation. Garerally
denitrification proceeds along the following pathway:
2NH0<sub>3</sub>.fwdarw.2NI~O<sub>2</sub>.fwdarw.N<sub>2</sub> O.fwdarw.N<sub>2</sub>.fwdarw.2N0. (3)
Thus, the transformations of nitrates to nitrites, nitrites to nitrous oxide,
nitrous oxide to
elemental nitrogen, and elemental nitrogen to nitric oxide occur. Organisms,
including
bacteria, which reduce these compounds, are thought to be anaerobic.
Similarly, alternating anaerobic and aerobic zones have been shown to benefit
the growth
of bacteria, which remove phosphorus from the water. See, e.g., i~andall et
al. (Edi.tors),
"Design and Retrofit of Wastewater Treatment Plants for Biological Nutrient
Removal,"
Water QualityManagement Library, Tcchnomic Publishing Co., lna.~ Lancaster;
Pa.
(1992).
FIG. 6 depicts one embodiment ofthe present primary treatment cell with
alternating
aerobic 250 and anaerobic 252 zones. However, other embodiKxzex~ts of the
present forced
aeration system (described above) are also capable of establishing alternating
aerobic and
anaerobic zones as wastewater being treated in the present primary treatment
cell filows
substantially horizontally therethrough. In the embodiment depicted in FIG. 6,
atmospheric air is bubbled from proximate the bottpm of the primary treatment
cell 102,
through the bed medium 120 (hence the root structure), to the top of the
wastewater level
CA 02372331 2004-03-12
Amended 38
(e.g., 210, file. 9a). The oxygen concentration within the wastewater being
treated in the
aerobic zones increases because the wastewater dissolves oxygen from the air
as the air
bubbles rise through the wastewater column. By contrast, the wastewater being
treated in
the anaerobic zones has dissalved oxygen at concentrations too low to sustain
aerobic
bacterial pollutant decomposition and a generally negative oxidation-reduction
potential.
It may often be advantageous to limit the amount of aeration--not only
physically within
aerobic zones throughout the primary treatment cell 102--as well as to vary
the oxygen
gradient within the water. The oxidation gradient thus varied, may promote
microbial
diversity and oxygen transfer e~ciency, thus, bettor stimulate the types of
chemical
transformations described above. The aeration process has many other benefits
to the
invention. One of the primary benefits of aeration is that the aeration
accelerates
w w w ~" - ~ nitrification. In the ease 'of wastewater, such as domestic
sewage, ammonia is ~ w
advantageously nitrified by transforming ammonium ions into nitrite ions, then
further
1 S transforming nitrate ions into nitrate ions using different bacterial
populations within the
aerobic and anaerobic zones.
In the primary treatment cell embodiment with forced bed aeration depicted in
FIGS. S
and 6, the depth of the primary treatn;xent cell can efficiently reach five
feet or more
below around surface. In this particular embodiment, the primary treatment
cell depth is
limited only by the depth at which it is zoo longer cost-effective to force
air to a location
proximate the bottom of the primary treatment cell for aeration. This depth is
generally
CA 02372331 2004-03-12
Amended 39
considered to be between about 20 and 25 feet.
Aeration of t>xe present primary treatment cell (as well as lowering the
wastewater Icvc1)
also promotes a greater rooting depth ixx tk~e wetland flora 124. F1G. 11
depicts root
depths in primary trcaxmcnt cells with 250 and without 262 aeration. Under
forced 'bed
aexation, oxygen is transported into the treatment bed to the vicinity of the
plant roots.
Therefore, the plants have a lower concentration gradient to overcome when
transloeating
oxygen from the leaves, through the stems, and into the mots. With a lower
concentration
gradient to overcome, less metabolic enexgy is needed to support root tissue
growth and
development. Consequently, the plant can support more roots at a greater depth
than
could be supported in wetland systems of the prior art without forced bed
aexatioz~. The
beneficial aspects of aeration and calculated raising and lowering of the
water level for a
' - ' ' ' sufficient period of time (termed drawdown-in this study) are
further disclosed in
hockhart, A. Ivl., "A Comparison of Constructed Wetlands Used to Treat
Domestic
Wastes: Conventional, Drawdown, and Aerated Systems," M. S. Thesis, University
of
Iowa (1999). In this study, wetland plants were grown in cells with gravel as
a medimn
and a continuous flow of wastewater. A control set of cells received no
aeration or
drawdown. A second set of cells was aerated, but not subjected to the drawdown
protocol. A third set of cells was subjected to the drawdown protocol, but not
aerated.
'fhe entirety of the bed medium subjected to aeration was clear and na dark
zones ar
build up was noted. Dark zones are residue from anaerobic bactezaa. 'thus, the
entirety of
cells subjected to aeration were provided with an aerobic environment. Black
zones were
i
CA 02372331 2004-03-12
Amended 40
present throughout thte control cells to indicate that the entirety of the
control cells were
anaerobic. The cells undergoing the drawdown had black zones below the lawest
fluid
levels attained during drawdown, but were clear above the lowest fluid levels
(drawdown
zone}. Therefore, the portion of the cells exposed to ai.r in the drawdown
zone during a
drawdown event was aerobic and the portion of the cells not exposed to air
during a
drawdown event (below Che drawdown zone) was anaerobic in nature. Dark zones
were
present throughout the bed medium, except within the rhizospheres ofcontrol
cells. Thus,
sufl=ZCient oxygezt was not present in the rhizospheres (proximate roots} of
the control
cells to produce aerobic conditions.
In the conventional cells, the tubers and roots (of Typha latifolia} grew both
vertically
and horizontally to a limited extent. By contrast, rooting patterns of aerated
cells were
deep and extensive:-The tubers and roots grew downvertically and wcre-present
deeper
within the medium than was the case in the control cells. In Che drawdown
cells the cattail
tubers and mots were more extensive than those of the cantrnl cells only
within
drawdown zones. The tubers eventually grew below the drawdown zones to a
limited
extent.
Without wishing to be bound by any specific theory, it xs believed that oxygen
supply
determined rooting patterns. The plentiful supply of oxygen in aerated cells
stimulated
extensive and pervasive tubers a~ud root growth. The zr-~oze limited supply of
oxygen in
drawdown ells stimulated root and tuber gowth only in portions where
sufficient
CA 02372331 2004-03-12
Amended 41
oxygen ryas present (drawdown zones). By contrast, the only oxygen supply for
the
control cells was from the very limited amount diffiising from the atmosphere
at the
fluid-air interface. Therefore, tubers and roots grew within this very
.li~onited volume.
Thus, as compared to a nonaerated control riot subjected to a drawdown
protocol,
aeration and a calculated raising and lowering of water levels stimulates more
extensive
and pervasive tuber and root growth.
Continuous aeration ma,y not always be necessary. once the oxygen content in
the
wastewater being treated in the primary treatment cell reaches a generally
saturated
concentration, further aeration is unnecessary and is thus inefficient.
Therefore, aeration
using oxygen sensors, tuners, or other means to regulate aeration (described
hereinabove)
is contemplated in the forced aeration embodiments of the present invention.
As previously described, a dosing siphon transfers water from the present
primary
treatment cell to, e.g., the secondary treatment cell 104. The dosing siphon
used thusly
can control the wastewater level in the present primary treatment cell.
Controlling the
primary treatment cell water level has important implications in the operation
of the
present invention. The calculated lowering of wastewater levels in the present
prizrlary
treatxnez~t cell (e.g., by the dosing siphons described hcreinabove) tends to
increase
natural root gowth and fiuther stimulates aerobic bacterial growth as well.
Stimulating
root growth. further enhances the pervasivencss of root tissue throughout the
bed medium.
Increased root tissue in the bed medium increases the oxygen content of the
wastewater
CA 02372331 2004-03-12
Anaez~ded 42
and also increases the porosity of the bed medium. Moz~eover, the presence of
atmospheric oxygen at low wastewater levels stimulates the growth of aerobic
bacteria
proximate the bed medium in places where the aerobic bacteria would not be as
plentiful
otherwise.
With reference to the embodiment depicted in FTG. 3, wastewater (effluent}
enters the
primary treatment cell 102 via inlet 116 after solids have been allowed to
settle out in the
septic tank 56. As the wastewater flows between spaces in fhe bed medium from
the inlet
116 to the outlet 118, the wastewater flows substantially horizontally as it
passes through
the alternating aerobic and anaerobic zones. Certain compounds (e.g., nitrates
and
phosphates) in the wastewater are taken up by the roots as nutrients.
Nitrogenous
compounds are changed by mostly bacterial enzyrnat~ic actions from organic to
ammonium, from aznmorAium to nitrate, and from nitrate to gaseous nitrogen and
nitric ~-
oxide. Other pollutant compounds are transformed into less objectionable
compounds by
other bacteria or other microflora. Some of the water is also removed froze
the prizxxary
treatment cell when it is taken up by the plants and. released to the
atmosphere as
evapotranspiration.
,lifter the wastewater has been treated by the primary cell 102, the present
invention
contemplates embodiments to further treat the treated wastewater for release
into the
environment. Refernng to FIG. 3, one exemplary secondary treatment cell 104
includes a
elosEd, preferably cement, structure 2$0 with a surface aceess~ible top cover
panel 2$2 to
CA 02372331 2004-03-12
Amended 43
facilitate medium replacement. A bed medium 284 is present within the
embodiment
depicted. Also present in this embodiment are an inlet 290, and any outlet
292. Th.e inlet
290 receives treated wastewater from the siphon discharge pipe 196 and
releases the
treated wastewater pro~zrnate the bottom of the secondary treatment cell 104
through a
series of slits or apertures 293. The treated wastewater then flows througk~
the bed
medi um 284 and out of the secondary treatment cell 104 through the outlet 292
to a
discharge area 294. Alternatively, the secondary treatment cell itself is
porous or
permeable in nature, thereby allowing release of further created wastewater
into a
subterranean discharge area 296. 'fhe bed medium 2$G. of the secondary
treatment cell
I O 104 may include any material disclosed with respect to bed medi~un 12p and
further may
contain substances for removal ofphosphorus, or other compound.. through
chemical
absorption and to neutralize acid pH as disclosed above. Thus, any
coxz~ibinatioz~ of
- primary and secondary cells, including either or both with
chemical=absorbing and/or ~ ~ ~ ~ ~ - w
neutralizing capabilities, can be advantageously configured to adapt to the
types of
pollutants to be treated.
Another embodiment of the present secondary treatmexxt cell is showzl izz
F1GS. 9a and 10
at 298 and includes a permeable liner or structure 300, a bed medium 301, a
mulch layer
122, and a plurality of wetland vegetation 124 rooted in the bed medimn 301
and growing
through the mulch layer 122. The permeable liner 300 enables infiltration of
treated
wastewater to the soil profile 302 below the secondary treatment ee31 298, as
shaven by
arrows 303, into the underlying aquifer 299. The bed medium 301, mulch layer
122, and
CA 02372331 2004-03-12
Amended 44
wetland vegetation 124 may be similar or identical to embodiments described
hereinabove and may perform similar fractions in further purifying wastewater.
An outlet
(not shown) may be present td convey further treated wastewater for disposal,
e.g., in
drain fields. A fluid level control system (e.g., a dosxz~g chamber and
siphon) rnay also be
present to control wastewater levels in this embodiment.
Yct another embodiment of the present invention further extends the
infiltration area
from the present secondary treatment cell to below the primary treatment cell
102.
Referring to FIC. 12, a pipe 304 includes apertures 306 and 30$. Apertures 306
are
located beneath the primary treatment cell 102 and apertures 30$ az~e located
in an upper
portion 31 p of the pipe 304 within the secondary treatment cell itself. So
that at least
some of the wastewater being treated by the secondary treatment cell 104 will
pass
w w '°' w ~ ~ ~ ~ through the pores between the bed medium
particulatcs, fluids entering-the secondary
treatment cell 104 flow from an inlet 311. Treated wastewater levels may
fluctuate
between a lower level such as level 312 and a higher level such as (exit)
Ievel 314. At
level 314, these fluids can enter the pipe 304. )~rom the exit level 314, the
fluids flow
through the pipe 304 and exit via the apertures 306 into another subterranean
infiltration
area 316 located below the present primary treatment cell aad as indicated by
arrows 31$.
Alternatively, (or in addition to the pipe 304) a porous and/or pertzxeable
bottom to ttze
secondary treatment call 104 may allow further treated wastewater to egress
into the
underlying infiltration zone 29fi as indicated by arrows 316. In this way, the
soil beneath
primary treatment cell can be used as a back-up infiltration area if, e.s.,
hydraulic loading
CA 02372331 2004-03-12
Amended 45
into the secondary treatment cell exceeds the infiltration capacity of other
discharge
areas. Moreover, this embodiment, yr variations of this embodiment, can be
advantageous when limited physical space exists at the installation site.
When the primary treatment cell sufficiently purifies wa.Stewatcr, the
secondary treatment
cell may not be necessary. Referring to FIG- I3, the dosing siphon 106
discharges treated
o wastewater directly into a drainage system 320 installed within a drainfield
(or mound)
322. The drainage system 320 includes a system of pipes 324 with perforations
326 and
may be similar to drain systems commonly used in connection with septic tanks.
LO
Referring to FIG_ 14, another embodiment of the present system is indicated
generally at
400 and includes a septic tank 402, a ~..tter tank 404, a recirculation tank
406, a vertical
w-- ~ ~ flow-constructcd wetland cell (reactor) 408, a~ dosing tank 410; and
one nr more w
embodiments of a disposal system indicated generally at 412. The septic tank
442
receives sewage from the sewer line 420. After the sewage flows into the
septic tank 402,
solids are allowed to settle. The separated, liquid wastewater (effluent)
flows through a
line 422 to the filter tank 404. In the filter tank 404, a filter 424 is used
to remove
suspended solids from the wastewater. A return line 426 conducts returned
treated
wastewater to t)~e filter tank 404 from the vertical flow wetland 408. Thus,
in the filter
tank 404, wastewater from the septic tank 402 is mixed or blended with treated
wastewater conveyed from the vertical flow wetland 408. The filter tank 404
therefore
serves two purposes. One purpose is to filter out any biosolids or bacterial
slimes from
CA 02372331 2004-03-12
Amended 4fi
the vertical flow wetland 408 as well as additional solids from the wastewater
flowing
from the septic tank 402. 'xhe other purpose is to allow nitrified effluent
from the
substantially aerobic vertical flow wetland 40$ to mix with the substantially
anaerobic
wastewater from the septic tank 402. The treated wastewater from the vertical
flow
wetland 408 usually has a low biological (biochemical) oxygen demand (BQD) and
most,
if not all, of the nitrogen in the treated wastewater frozx~ the vertical flow
wetland 408 has
been converted to nitrate form. When the nitrified, treated wastewater from
the vertical
flow wetland 408 is blended with the substantially anaerobic wastewater from
the septic
tank 402, the available dissolved oxygen in the treated wastewater is
considerably
lowered. Moreover, the wastewater from the septic tank 402 provides a carbon
source for
anaerobic metabolism. Thus, an ideal environment 3s created for denitrifying
nitrates, i.e.,
converting nitrates to gaseous nitrogen forms under anaerobic conditions. The
gaseous
' - " "" ' nitrogewforms are then vented~to~the-atrr~osphere and eliminated
from the~system. xhus; - w- w ~ ~ ~ w w -w w
this embodiment of the present system is extremely effective iz~ removing
total nitrogen
I S from wastewater. A suitable embodiment of the filter 424 is Model A-300
HIP and is
available from Zabel Environmental Technology, Crcstwood, Ky.
From the filter tank 404, the effluent is conveyed by being pumped or gravity
flowed
through the line 427 to the recirculation tank 406. A .pump 428 in the
recirculation tank
406 pumps the blended wastewater to the vertical flow wetland 408 via line
430. A
wastewater supply system 432 may be considered to include the filter tank 404,
rccirculation tank 406, and/or pipes and tubing conveying wastewater to the
vertical flow
CA 02372331 2004-03-12
Amended 47
wetland 408.
One embodiment of the vertical flow wetland cell 408 is depicted in FIGS. 15,
16a, 16b,
and 16c and includes an outer structure 440, an insulative layer 442 and an
impermeable
liner 444. In this embodiment, the outer structure 440 includes 3/4 inch,
pressure-treated
plywood. The insulative layer 442 may include such materials as Styrofoam.TM.
and
may be about two inches in thiclaiess. Th.e impermeable liner 444 may be made
of
materials such as 30 mil PVC sheeting. The impermeable liner 444 extends
around the
interior of the inner volume (or basin) defined by the outex structure 440
azzd the
x0 insulative layer 442. Atop the impermeable liner 444 is a series of drain
lines 446
embedded within one embodiment of a bed medium such as a drainfield bed medium
448
(e.g., about 30 ~in:ches in depth). Atop the bed medium 448 is a series of
aeration lines
w w 450: Another bedwmediuxn embodiment such as an upper bed medium 452 is-
disposed w w w w ~- w w-
above the aeration lines 450. The drainfield bed medium 448 particulates may
be Larger
(i,e., have a larger average maatimum cross-sectional dimension such as a
diameter) than
a similar dimension of the uppar bed medium 452 particulates to promote
drainage into
the drain lines 446. Exemplary materials suitable for the drainf"ield bed
medium 448 and
the upper bed medium include gravel or plastic packing with respective
dimensions such
as between about one inch and two inches (±0.5 inch) and between about one
inch and
one and one-half inch (±0.5 inch). A series of wastewater distribution
lines 454 is
disposed above the upper bed medium 452. Aa optional mulch layer 456 overlays
the
upper bed medium 452 and the wastewater supply lines 454. Materials suitable
for the
CA 02372331 2004-03-12
Amended 4R
mulch layer 456 may be similar or identical to those disclosed with respect to
mulch layer
12z, hereinabove_ Vegetation 458 is rooted in the upper and drainfield bed
media 452 and
448 and extends through the mulch layer 456. The vegetation 458 tray include
the
wetland species described hercinabove or may include other species which do
not require
continually wet or saturated soils. An air supply (source) such as a blower
460 (FIG. 14)
supplies air to the aeration lines 450 via a series of air supply lines 462.
One suitable
blower is a model DR303 and is available from Axnetelc-Rotron, Inc.,
Saugerties, N.Y.
In one embodiment, two rows of bolts 468 are drilled in the drain lines 446.
These holes
468 may have diameters of about inch and be spaced apart about one foot on
center. The
rows of hotel 46$ may be oriented at about 4 and 8 o'clock (e_g., about
120° apart)
as depicted in the inset of FIG. 16a. The series of aeration pipes 450
lilccwisc define one
........... ,.. . . ..... or more'rows ofholes~4'70: Typica9 hole
470~dimensions in the aaratian lines (pipes?.... .... .. .......~.. . ...... .
would be inch in diameter or less, spaced about every two feat. Alternatively,
drip emitter
tubing may be used. One suitable drip emitter is "Wastetlow Classic" (part
number 'Wf-
16-4-24), available fram Geotlow, inc., Charlotte, N.C. ?his emitter is
disclosed in
above-rcfereziced LJ.S. Pat. No. 5,332,160 arid in U.S. Pat. No.
5,116,414..pimensions
and orientation of holes 470 may be similar to those of holes 468, discussed
above. The
wastewater supply lines 454 similarly define a row of holes 472. The row of
holes 472 is
oriented generally down, the holes being about inch in diameter and spaced
apart about
three feet in this embodiment. Alt~mativcly, the diameters of the holes may
gradually
increase as they become farther from the liuue 430 to ensure that the
wastewater from the
CA 02372331 2004-03-12
Amended 49
xecirculatidn tank 406 is distributed substantially evenly over the present
vertical flow
wetland. A valve 474 xnay be present to control the wastewater flow from other
wastewater supply pipes branching from wastewater supply lines 454 or to other
wastewater distribution lines branching from the wastewater distribution Iinc
454 (FIG.
16c) and to allow the wastewater distribution lines 454 tv be flushed. The
distribution
lines 454 distribute the wastewater across the top of the vertical flow
wetland (basin
After the wastewater has been pressure-distributed across the top of the
basin, the
wastewater trickles down via gravity through the upper bed medium 452 and the
drainfield bed medium 44$. The drain lines 446 return the flow of treated
wastewater
back into the filter tank 404. Suitable materials and dimensions for the drain
lines 446,
and wastewater supply lines 454 include four inch schedule 40 PVC tubing and 1-
2 inch
schedule 40 PVC tubing, respectively. Of course, a person of ordinary skill in
the art will
- - - ~ ~ ' ' " w " w recognize that other materials andlor'dimensions may be
suitable as well: ~k'wastewater ° ~ ~ w ~-- - - - -
retLUn system 475 may arbitrarily be considered to include the return line
426, drain lines
446 and all structures conveying treated wastewater from the wetland cell 408.
One substantial difference between the maxmer the wastewater is treated in the
vertical
flow constructed wetland embodiment {designated as 400) as compared to
previous
embodiments of this invention is that the basin of this vertical flow wetland
embodiment
is not completely filled with water (unsaturated). Thus, the unsaturated,
generally
vertical, flow is charactemi~ed by the wastewater being dripped or streamed
through the
present bed medium in fluid quantities not sufficient to completely fill the
spaces
CA 02372331 2004-03-12
Amended 50
between the bed medium particulates. Thus, atixiospheric gases are present
substantially
thrnughout the unsaturated vertical flow wetland 408, e.g., present in
portions of the
upper bed medium 452 and the drainfield bed medium 448. In addition to the
unsaturated
bed media, there are two additional ways of aerating the present system. The
first way is
via the air supply blower 460, air supply Fines 462, and aeration lines 450.
The aeration
lines 450 are typically perforated to deliver a supply of ambient air
throughout the bed
media in the wetland cell basin. In contrast to previous embodiments,
alternating aerobic
and anaerobic zones need not be present within the present system, However,
wastewater
being treated is conveyed through an aerobic environment provided by the
present
wetland cell and anaerobic environment in the septic tank, filter tank and
recirculating
tank. The blower 460 rnay continuously supply air. However, the blower 460 may
include
a timer switch 461 to periodically actuate the blower as needed. One suitable
blower is
...... ........ . ... .... .. .0083 and may be obtained from Ametek~Ratron,
Inc: - .. . . . . ... .. .. . .. .. . .. .. .. __ . . . .. . . . _ . . .
After being cycled between the filter tank 404, recirculation tank 40G, and
vertical flow
wetland 408, the treated and blended wastewater is conveyed by gravity or
pumped to the
dosing tank 410 via Iine 464. Onc embodiment of the dosing tank 410 conveys
treated
wastewater to the disposal system 412 via such means as a pump 480. One
suitable
embodiment of the pumps 428 and 480 is a SHEF 50, which may be obtained from
ldydromatac, In.c., Ashland, Ohia. A dosing siphon, stand pipe, or the like
rnay also be
used to convey treated wastewater from the dosing tank 410 to the disposal
system 412.
Treated wastewatez~ may also be conveyed directly from the recirculating tank
406 to the
CA 02372331 2004-03-12
Amended 51
disposal system 412 in some embodiments.
The disposal system 412, by way of illustration and not limitation, rnay
include a trench
system 490, a drip irrigation system 492, an infiltration bed (or mound) 494,
or discharge
to a surface body of water 49b. It shouid be noted that the separate septic
tank 402, filter
tank 404, recirculation tank 406, and dosing tank 410 may all be combined into
one or a
few tarjks with a variety of compartmezzts. These tanks may be constructed of
fiberglass
treated to become impermeable, another synthetic resin., concrete, or other
suitable
materials. These tanks may typically be substantially disposed within the
earth.
A system substantially similar to the system 400 was installed near Blame,
Minn. In this
case, the filter tank and recirculation tank were a single structure with two
compartments.
The wastewater entering the filter tank and the treated wastewater
beingconveyed from - w ~ ~ ~ w-- ~ ~ ~ - ~-
the dosing tank were sampled at two day intervals. Results from analysis of
these samples
arc shown in Table 1, below. Carbonaceous biological oxygen demand and fecal
colifonn
counts were determined at cacti sampling. Removal of carbonaceous biological
oxygen
demand by this system varied from 97% to 99%. Fcca1 coliform removal was in
excess of
98%_ Total nitrogen removal was 89% and 86%. The fecal colifarm readings
usually met
standards for water used for swimming (usually 100/100 m). The highest fecal
coliform
reading was close to the standards usually present for disinfected wastewater
(usually
200/100 m). One fecal coliform reading met the standard for drinking water
(usually
4/100 m).
CA 02372331 2004-03-12
Amandad 52
'fAHLE 1
Wastewater Ppllutant Measurements From Ingress3ng Waste-
water and Egressiag (Treated) WE~stewlW er Treated by a
vertical Flew Constructed wetland wasteurater Treatment
System.
sampling HOD-c Feca1 Tonal
colitornn N,
sup.
3
nate sup i. sup.
2
in / but / Ia / Out / Ia / Out /
sup. Sup. Su . Sup. Su . Sup.
4 '~ 4 $ 4 5
Feb 7 139.0 a2.0a 10,000 229 47.7 5.4
2000
Feb 9 -- 3.5 ~ 10,00034 -- --
2000
Feb 11 248.0 3.0 n 10,ODD14 31.2 4.4
2000
Feb i3 -- ~1.0> > I0.0004 --
aooo
........_~ . ..F.eb __ 1:1. . ~ .1D;O~DD~. 6 .....__-_ .,. _ .
... . x4~.~ . . .
.
2000
<sup>1</sup> BOD-C. Carbonaceous biological oxygen demand, measured as
mg/ cznd as
lU determiried by EPA Method 354.x.
<sup>2</sup> fecal Coliform measured as number ger 100 m cad determined
f by method
i
9221E.
.sug.3 Total N, Kjeldahl Nitrogen measured as mg/ by EPA Method
15 ssl.l.
CA 02372331 2004-03-12
Amended 53
<sup>4</sup>,5 Readings of wastewater entering the filter tank arid
exiting the
dosing tank, respectively.
FRGS. 17, 1$, 19, and 20 depict an alternate embodiment of the present
inventian as
disclosed above. This alternate embodiment is generally indicated at 500 and
includes a
tank S02 and a vertical flow wetland unit 504. The tank SOZ includes an inlet
512, a
septic (settling chamber 514, and a recirculating chamber 516. The septic
chamber 514
includes a plurality ofbafflcs such as baffles 520 aztd 522 to facilitate
settling out solids
az~d is in fluid communication with the recirculating chamber 51 G via a
settling chamber
outlet 524. The recirculating chamber 516 includes a manhole unit 530, which
extends
through the vertical flow wetland unit 504 as a manhole riser 532. An access
cover 534
normally covers the zxianhole riser 532. The rccirculating chamber 516 may
include a
rceirculating pump 540. The recirculating pulnp 540 pumps wastewater effluent
being
treated through a filter (or screen) 542 through a pump outlet 544. The outlet
544
terminates in another forced air source such as az~ air injector 546. The air
injector 546
aspirates air into the wastewater as the wastewater is pumped therethrough.
One suitable
air injector is disclosed in LJ.S. Pat. No. 4,123,800. From the air injector
546, the aerated
wastewater enters a tee 547. From tk~e tee 547, the effluent is pumped through
one or both
diapbragm valves 548a, b. From the diaphra;~m valve 54$a, the aerated
wastewater is
pumped through an outlet line 550 to a distribution tube 576. The distribution
tube 576 is
arbitrarily considered to be a component of the vertical flow wetland unit
504, and is
discussed below. A float-operated solenoid valve 560 is present between the
tee S47 and
CA 02372331 2004-03-12
Amended 54
the diaphragm valve 548b. prom the diaphragm valve 54$b, the aerated
el°fluent is
conveyed through an elbow joint 561 into a disposal pipe 562, from which the
aerated
and potentially treated effluent is conveyed to a disposal field. A disposal
return 564
conveys treated wastewater back into the recirculating cb.amber 516. A float-
operated
solenoid to determine when Created wastewater will be conveyed to a disposal
field has
the advarAtages of being relatively simple in design and function and usually
enables the
present system to treat and dispose wastewater_ This float-actuated system may
be termed
"on-demand based." An on-demand based system actuates conveyance to disposal
when
the treated wastewater reaches a predetermined volume---regardless of the
timing and
frequency of conveyances. Thus, a relatively large amouxat of treated
wastewater zxxay be
conveyed to the disposal in a short amount of time, potentially overloading
the disposal.
under certain circumstances aw alternate method of detc;rmining when treated
wastewatc.~r w
will be conveyed to disposal is preferable. One alternate method is a
controller logic unit
1 S L. One such unit would route treated wastewater to the disposal upon a
predetermined
number of pump activation iterations (e.g., every fifth, seventh, or tenth).
In another
embodiment, the number of iterations would be determined by such factors as
wastewater
oxygen concentration. Another embodiment would either be totally time-based or
would
be a combination of time-based and wastewater characteristics (e.g., dissolved
oxygen
concentration). These criteria for determining when to convey treated
wastewater to
disposal would have the advantage of better spacing treated water conveyances
to the
disposal over tizx~e azzd would have a lower likelihood of overloading the
disposal system.
CA 02372331 2004-03-12
Amended SS
The vertical flow wetland unit S04 may include a tank 570. The tank 570 maybe
a self
contained, substantially impermeable structure made of such materials as
fiberglass.
However, several embodiments, such as the structures disclosed above with
respect to the
vertical flow wetland 408 may also be used. A drain return 572 receives
treated
wastewater from upper drains 573 (FIGS. 18 and 3 9). A bed medium 574 is
disposed
about, az~d overlays, the drain return 572 and upper dzains 573. pf course,
the bed
medium may also include two or more types of bed media as discussed above with
respect to the disposal system 400. An interconnected series of distribution
tubes S76
extends from the outlet SSO. One or more of these distribution tubes S76 may
terminate in
a return line 577. The distribution tubes 576 arc generally disposed atop the
bed medium
574. The return lines 577 generally extend through the bed medium 574,
returning
weffluent into' the recircula,ting chamber 516;°e:g., via returns 564.
A~rnulch layer 578 - ~ ~ ~ ~ -
overlays the distribution tubes 576 and bed medium 574 in this embodiment.
Vegetation
580 is rooted iz~ the bed medium 574 and grows through the mulclx layer 578.
'.fhe mulch
layer 578 may be substantially similar to the substantially decomposed mulch
layers
disclosed hereinabovc. The vegetation S80 may include plant species of
previously
discussed embodiments, but may also include species which arc less tolerant of
saturated
bed media.
The air injector 54b is an alternate embodiment of a forced air source and
constitutes yet
another method of oxygenating wastewater being treated by the present System.
The
CA 02372331 2004-03-12
Amended 56
reeireulating pump X40 and/or air injector 54G may be used in lieu of pump
42f3 of system
400 as well. One suitable rccirculating pump is J10BE, available fram
Hydromatic, Inc.
One suitable air injector is disclosed in U.S. Pat. No. 4,123,800, issued Oct.
31, 1978 to
Mazzei. The oxygenated wastewater prox~aotes aerobic bacterial activity to
more
efficiently decompose pollutant compounds.
The solenoid valve 560 is an atternate method of transferring treated
wastewater from the
present recirculation chamber to a disposal systezxz (e.g_, disposal. system
412). The
solenoid valve 550 may be controlled by a float switch (not shown). Eor
example, the
float switch may actuate the solenoid 560 to open a valve allowing treated
wastewater to
be pumped from the rccirculation chamber 516 to a disposal site when a
wastewater level
588 is attained. Once the wastcwatcr level has dropped to a low level 590, the
float
switch ~eloses the valve and wastewater recirculation to the vcrticalWow-
wotlandwnit ~504w ° w ~ --- - w - ° w
recommences. Alternatively, the disposal retlun 564 and/or drain 572 may
convey the
treated wastewater diz~ectly to a disposal field or other site for disposal.
The recirculation pump 540 may be actuated from a timer switch (not shown) to
better
adjust the how of wastewater being treated. Continuous recirculation is also
possible, but
may not always be desirable. Typically, the recirculativn pump timer is used
so that a
flow of approximately 5 to 20 times the throughput flow is recirculated on a
daily basis.
Ono method of regulating recirculation and output flow is described above with
respect to
the logic unit L.
CA 02372331 2004-03-12
AmcndCd 57
The distribution tube 576 may include a row of apertuz~es 594, typically 114
inch in
diameter and spaced apart about three feet. Alternatively, a drip emitter as
disclosed
above zzlay be used. The return lines 577 enable a portion of the oxygenated
flow puxxlped
into the distribution tube 576 to be directed back to the recirculating
chamber 5 i6 rather
than being directed through the vertical flow wetland unit 504 as an alternate
method of
adjusting oxygen concentrations within the wastewater cantained within the
recirculation
chamber S 16. The upper drain pipes 573 collect flow of treated wastewater
from the
bottonrl of the basin foz~med by the tank 570 and return the flow back to the
recirculating
chamber 516. In one embodixxaent, the upper dxains 573 are generally
triangular in cross
section and may be cast unitarily with the tank 570. Flowever, perforated
pipes, 2 to 4
inches in diameter, may be used as upper drains 573 as well. Any or all of the
present
w rccirculating pump, valves, lines, and distribution tubes are arbitrarily
contemplated towbe
included in the wastewater supply system 432. The wastewater return system 475
may
include structures for conveying treated wastewater from the wetland cell
50.4, such as
the drain return 572 and disposal return 564.
Another alternate embodiment of the present intervention is depicted at 600 in
FIG. 21
and is operably ixlstalled in a soil profile. However, free standing
embodiments which are
nol disposed in a soil prurlle may by (14~1It11)h: lIl 'uUIIII:
'~llUilliUIL'i. The system 600 - - w - - - ~- w w w - w --- w
incorporates many of tile features of the exrlbodizzlent discussed above with
respect to
FIGS. 14, 15, and 16a-c into a single, integrated, easily installed emit. The
wastewater
CA 02372331 2004-03-12
AmcndEd 58
treating system 600 includes a tank 602 and a vertical flow wetland unit 604.
An inlet
610 (c.g., 4 inch diameter, schedule 40 pVC) er~opties into the tank 602. The
inlet 610
may be fluidly connected to a settling tank, such as a septic tank, wherein
solids are
settled out of the exogenous wastewater before the wastewater enters the
wastewater
treating system 600. The tank 602 has a partition 612, which separates a first
reservoir,
such as a septic chamber 614, and a second reservoir, such as a pumping
chamber 616.
The septic chamber 674 and the pumping chamber 616 are in fluid communication
via an
opening 618. However, the septic and pmnping chambers 614 and 616 could be
completely separate structures as well. The inlet 610 opens into a canister
622. A filter
container 624 contains a filter 626 and a handle 62$ extends from the filter
626. The
handle 628 allows the filter 626 to be removed for cleaning or replacement. A
first riser
630 allows access to the septic chamber 614 and is disposed above the canister
622. A
' w " -~ - ~ 'second 'riser 632 allows access to 'the soptic chamber 614 and
tlxe pumpiztg chazxzber frl6: w - ° ~ ~ ~ ~ w
The second riser 632 is disposed over the filter holder 624. A third riser 634
allows
access to the pumping chamber 616. Covers 636, 638, and 640 cover respective
risers
630, 632, and 634.
The tank 502 is substantially impermeable to liquids, so that the wastewater
within will
not seep into the soil profile frozxx the tank 602 before being treated. The
tank 602 may be
constructed from impervious materials {e.g., fiber glass} or, alternatively,
may be
constructed from materials whick~ are not imperviomS (e.g., cement), then
coated with a
substance to impart impermeability (c.g., bituminous coating).
CA 02372331 2004-03-12
Amended 59
The canister 622 is open at a top 642 thereof or is otherwise constructed to
readily admit
liquids from the vertical flaw wetland unit 604 as more fully described blow.
One
suitable embodiment of the canister 622 is a wire basket. The canister 622
crnltains a
mixing device 644 (not shovun) which readily allows liquids to pass
therethrough, but
with a large surface area to provide fluid mixing and a habitat on which
anaerobic or
anoxic microorganisms can function to denitrify the wastewater. The canister
622 also
includes a bottom portion 646 with at least one, preferably a plurality of,
openings) 648
(not shown). Suitable devices 644 for these purposes have suzface areas of
greater than
about 15 square feet per cubic foot of volume, between about 15 and 85 square
feet per
cubic foot of volume, between about 38 and 85 square feet per cubic foot of
volume, or
any range subsumed therein. These mixing devices may be made from injection
molded
resins such'as pol.ypropyiene, PVC, KYNAR.RTM:, H alas®; Tcflon:RTM: and
glass-filled polypropylene. Oz~.e suitable embodiment includes vertically
disposed,
bundled PVC tubing. Other suitable embodiments are sold as Tri-Packs® and
are
available from Tri-Mcr® Corporation, Owosso, Mich. The filter 626 may use
a
stacked plate, brush fiber, or pleated (or similar) media capable of filtering
particulate
mataacr from the combined wastewater and recirculation flow. One suitable
embodiment
ofthe filter 626 is designated Model A-300 H1P and is available from Jabel
Lnvironmental 1 ethnology, Crestwood, Ky.
Within the pumping chamber 616 is a circulating pump 650 disposed on a stand
651. The
CA 02372331 2004-03-12
Amended 60
pump 650 is configured to pump fluids through a pipe 552. The pipe 652 is
joined to an
optional air injector 654 at a joint 656. The air injector 654, in turn, is
joined to a three-
way ball valve 658 at a joint 660. The three-way ball valve 658 is operated by
an actuator
662. A series of pipe sections 664, 666, and 668 and joints 670, 672, and 674
connect the
three-way ball valve 658 tv a distribution tube, such as distribution tube 576
(FIG. I7). A
of series pipe sections 676, 678, and 680 and joints 682, 68a, 686, and 688
fluidly
communicate the three-way ball valve 658 to an outlet 690. An optional rope
692 is
attached to a lifting handle 694 on the pump 650. The rope 692 may be used to
remove
the pump 650 for repair or replacement. Optional and respective pressure
gauges 696,
d98, and 700 monitor fluid pressure in the pipe 652 and joints 574 and 682
when the
pump 650 is operating. The pressure gauges 696, 698, and 700, if present, may
also be
use for quantifying the airflow from the air injector 654. Readings (sensings)
from the
pressure gauges may be relayed to the logical unit L' (not shown) to control
under' what
conditions the pump 650 will be actuated. In one embodiment, the pump 650 is a
0.5
horsepower, 230 volt, single face pump with a capacity of 20 (*/-5) gallons
per minute
when pumping fluids to the vertical flow wetland unit 604 and 17 (+/-5)
gallons per
minute when puzxaping .fl.ui,ds to the outlet 690. One suitable embodiment of
the air
injector 654 is disclosed in U.S. Pat. IVo. 4,123, 800.
Pxecpt for the presence of the risers 630, 632, and 634, the vertical flaw
wetland unit 604
may be identical, or substantially similar, to the vertical flow wetland unit
504 described
above. In the embodiment depicted in F1G. 21, the vertical flow wetland unit
604
CA 02372331 2004-03-12
Amended 61
includes a tank 7D4, which contains a bed medium 706. 'Ihe bed medium 706 may
be
substantially sizx~ilar to the bed media discussed above with respect to FIG.
3 or 15. A
mulch layer 708 and vegetation 580 may also be optionallypresent. The mulch
layer 708
is disposed over the bed medium 706. In this embodiment, the mulch layer
includes a
substantially decomposed substance such as peat moss. The vegetation 580 may
be
rooted in the bed medium 706 and grows through the mulch layer 708. A
wastewater
supply system, such as the system described above with respect to FYGS. 1720,
may
present to convey wastewater from the joint 674 to an upper portion of the bed
medium
70G. The wastewater supply system may comprise vessels similar to outlet line
550 and
distribution tubes 57G. After being vertically conveyed through the bed medium
706, the
wastewater is returned to the tank G02 by a wastewater return system, such as
the drain
return 572 and upper drains 573. In an alternative embodiment, a sotenoid
directs the
treated wastewater to an outlet rather than to the septic chamber (not shown).
The drain
return S72 empties into the canister d22. The wastewater return system may
also include
return lines 577, which cycle wastewater directly from the wastewater supply
system
without delivering the wastewater to the upper portion of the bed medium far
aerobic
treatment. Optioxxally a floor 710 of the present vertical flow wetland unit
may be sloped
so that, after the wastewater trickles through the bed medium '706 to the door
710, the
wastewater flows into the septic chamber 614 by force of gravity via an
opening (not
shown) in the riser 630 or another opening at an appropriate location.
In operation, water from the septic tank is delivered into the canister G22
via the inlet
CA 02372331 2004-03-12
Amended 62
610. When the pump 650 is operating, wastewater is delivered into the canister
622 c.g.,
via the return 572, after dripping through the bed medium 746. 'fhe canister
622 admits
the nitrified wastewater from the vertical flow wetland unit 604. When
conveyed to the
canister 622, the two wastewater streams are mixed in the device b44. The
mixing device
644 may be considered to provide a subzone in which the nitrified wastewater
from ttte
vertical flow wetland unit 604 and the incoming wastewater, e.g., from a
septic tank, are
mixed. The carbon source for denitrification within the septic chamber 614 and
the
pumping chamber 616 is provided by the wastewater from the septic tank.
Moreover,
mixing the two wastewater streams lowers the dissolved oxygen concentration
and ttxe
redox potential of the final mixed wastewater to anaerobic or anoxic levels to
thereby
allow far ve~astewater denitrification in the tank 602. The co-mingled
wastewater streams
from the septic teak and vertical flow wetland unit 604 then flow through the
device 644
and exit the device 644 through the opcaings 648. 'The device 644 has a large
surface area
to promote fluid mixing and provide habitat for bacterial (microbial}
denitrification
thcrewithin. Previous experience has indicated that the filter 626 must be
cleaned or
replaced approximately every third month in the absence of the device 644.
Cleaning the
alter 626 was likely necessitated by clogging due to growth of denitrifying
bacteria
within the filter 626. Using the device 644 has reduced the frequency of
cleanings
required to maintain the filter 626, often to intervals of 12 months, or
longer. Within the
tank 602 the mixed wastewater undergoes denitrification. The mixed wastewater
then
enters the pumping chamber 616 through the opening 618, aftor passing through
the filtez~
626. The filter 626 prevents solids from entering the pumping chamber 616. The
solids
CA 02372331 2004-03-12
Amended 63
may have originated from the vertical flow wetland unit 604 or the septic
taxtk. The filter
626 also provides additional surface area (habitat) for denitrifying bacterial
growth and
development.
Clpon entering the pumping chamber 61 G, th.e wastewater is still essentially
anaerobic {or
anoxic) and undergoes farther dcnitrification. 'The purnp 650 pumps the
wastewater from
the pumping chamber 616 tlwough pipe 652 and air injector 654. In the absence
of the air
injector 654, sufficient aeration to aerobically lower BOD may occur when the
wastewater is being dripped tbmugh the bed media layer in a substantially
vertical and
unsaturated flow andlor from an aerator disposed just upstream of where the
wastewater
is being delivered to the upper portion of the present bed medium layer (as
described
above with respect to FIG. 14). The air injector 654 injects air (oxygen) into
the
wastewater being pumped thcrcthrough. The actuator 662 directs the wastewater
stream
iiom the air injector G54 either to the vertical flow wetland unit 604 or the
outlet 690.
While trickling through the bed medium 706 ofthc vertical flow wetland uz~xt
G04 in an
unsaturated flow, the wastewater undergoes aerobic treatment, wherein BOD is
reduced
by aerobic microorganisms. The actuator 662 znay be float-operated. If float-
operated, the
wastewater is conveyed to the vertical flow wetland unit 604 when the
wastewater is
below a specified wastewater level 712. When the wastewater is above the level
712, the
actuator 662 and wastewater arc pumped to the outlet 690, e.g., to a
drainlabsorption field
i.n an adjacent soil profile. A~ltez~.atively, a controller logic unit L
(described above)
andlor a sensor S can be used. The sensor S senses the oxygen concentration of
the
CA 02372331 2004-03-12
Amended 64
wastewater in the pumping chamber 616. if the oxygen cancex~tratiozt is above
a
predetermined level, the valve 662 would direct the wastewater to the outlet
690. If the
oxygen concentration of the wastewater in the puzxxping chamber was below the
predetermined level, the valve 662 would direct the wastewater to the present
vertitcal
S flow wetland unit 604 to be further treated aerobically.
While the invention has been described in conjunction with specific
embodiments
thereof, it is evident that many alternatives, modifications and variatians
will be apparent
to those slailled in the art in light of the foregoing description.
Accordingly, it is intended
to embrace all such alternatives, modifications, and variations as fall within
the spirit and
broad scape of the invention.
lE5 12/03/2004 18:01 ~3 received
