Note: Descriptions are shown in the official language in which they were submitted.
1
METHODS FOR INCREASING NITRIFYING BACTERIA BIOMASS IN A WASTE
TREATMENT REACTOR SYSTEM
BACKGROUND
Compounds such as organic matter and nitrogen contained in wastewater are
capable of being oxidized and transformed by bacteria which use these
compounds
as a food source. Typically, heterotrophic bacteria digest the organic matter
while
nitrifying bacteria use the non-organic compounds as a food source, for
example,
oxidizing ammonia to nitrate (a process known as nitrification to those
skilled in the
art).
In existing systems, for example as described by the US Environmental
Protection Agency Manual on Nitrogen Control (USEPA, 1993); Wastewater
Engineering, Treatment and Reuse, 4th Edition (Metcalf and Eddy, 2003); Small
and
Decentralized Wastewater Management Systems (Crites and Tchobanoglous, 1998);
and Design and Retrofit of Wastewater Treatment Plants for Biological Nutrient
Removal (Randall et al., 1992), nitrifying bacteria are much more cold
sensitive and
as a consequence the nitrification process virtually ceases when the water
temperature approaches (e.g., decreases towards) 4 degrees Celsius.
A common form of biological wastewater treatment is the sewage treatment
lagoon and these lagoons typically discharge elevated levels of ammonia during
winter months in regions in which the water temperatures approach 4 degrees
Celsius
or lower. In view of changing environmental regulations, it would be highly
advantageous to develop biological treatment processes that could remove
ammonia
at water temperatures of less than 4 degrees Celsius.
In existing systems for removing pollution from water, a subsurface
constructed
wetland system may use forced bed aeration and variable water levels to
establish
staged anaerobic and aerobic zones within the system. While such systems may
deliver oxygen to the wastewater via aeration in a system utilizing attached-
growth
bacteria for treatment, they cannot provide improved removal of ammonia at
water
temperatures approaching 4 degrees Celsius.
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SUMMARY
As discussed herein and as will be apparent to one knowledgeable in the filed
of wastewater treatment, sewage treatment systems are designed to treat a
specific
volume of wastewater over a given period of time. As discussed herein, that
volume
may be estimated or predicted based on knowledge of the area that the sewage
treatment system is servicing as well as other factors such as the population
size of
the area, what percentage of the area is residential and the types of
businesses within
the service area. While the specific volume and/or ammonia content applied to
the
system overall and to parts thereof may vary considerably over a short period
of time,
over time, the average volume applied to the system by the users at a given
time can
be predicted based on for example previous usage patterns and in this context
can be
referred relatively consistent or constant.
Reference is made herein to "normal operations" or "standard operations" of
the sewage treatment system. As will be apparent to one of skill in the art,
this refers
to raw wastewater entering the waste treatment system at the entry point of
the
sewage treatment system and passing through the sewage treatment system under
normal or standard design conditions, that is, without transient or temporary
supplementation and/or volume increases or decreases, as discussed herein.
As is known by those of skill in the art, within a growth reactor, nitrifying
bacteria use organic and inorganic compounds as a food source, for example,
oxidizing ammonia to nitrate (nitrification). This process takes place only
where there
is sufficient ammonia and oxygen. In a growth reactor of a waste treatment
system
operating under standard conditions, nitrifying bacteria tend to grow where
the food
source is.
Described herein are a number of methods for increasing the biomass of
nitrifying bacteria within a waste treatment system. As discussed below, in
these
methods, conditions within a given reactor are modified such that growth
conditions
for the nitrifying bacteria are improved and/or such that the biomass of the
nitrifying
bacteria within the given reactor increases compared to what it would have
been
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under standard operations, that is, absent the intervention or modification
for
promoting nitrifying bacteria biomass growth and/or increase.
As discussed herein, the nitrifying bacteria biomass in a given growth reactor
may be measured or it may be estimated. For example, the nitrifying bacteria
biomass
may be measured or estimated by determining the nitrification capacity within
the
specific reactor by measuring and/or monitoring the amount of ammonia entering
and
exiting the specific growth reactor, or by monitoring the nitrites and
nitrates produced
in the reactor. Alternatively, the nitrifying bacteria biomass may be
estimated based
on knowledge of the sewage treatment system and of the interventions carried
out to
increase the nitrifying bacteria biomass.
As discussed herein, an estimated or predicted nitrifying bacteria biomass may
be used to estimate or predict the nitrification capacity of a given growth
reactor under
different conditions, for example, under different water temperatures. As
discussed
herein, this estimated or predicted nitrifying bacteria biomass may be used to
determine what quantity of wastewater a specific growth reactor is capable of
treating.
According to a first aspect, there is provided a method of improving ammonia
removal from waste water during cold weather including:
in a sewage treatment system including at least two attached growth reactors,
each respective attached growth reactor having an inlet distribution point in
the
attached growth reactor for receiving an influent of wastewater,
during a warm weather period, transferring an approximately constant volume
of the wastewater to the at least two attached growth reactors, wherein the
volume is
transferred such that a first attached growth reactor receives a larger
portion of the
volume than a second attached growth reactor for a first period of the warm
weather
period and the second attached growth reactor receives a larger portion of the
volume
than the first attached growth reactor for a second period of the warm weather
period;
and
transferring the volume of wastewater to the first attached growth reactor and
the second attached growth reactor approximately equally during a cold weather
period.
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Alternatively, as discussed herein, at the end of the warm weather period, the
nitrifying bacteria biomass within one of the growth reactors is estimated and
wastewater is transferred to the specific one of the growth reactors according
to the
estimated nitrifying bacteria biomass within the specific one of the growth
reactors for
.. the duration of the cold weather period.
That is, as discussed in greater detail below, during the intervention or
modification within the sewage treatment system of transiently or temporarily
increasing the volume of the wastewater entering a respective one of the
growth
reactors during the warm weather period, nitrifying bacteria within the
respective one
of the growth reactors are subjected to a higher quantity of ammonia than
under
standard or normal operations. This results in increased or improved growth
conditions for the nitrifying bacteria which increases the nitrifying bacteria
biomass
compared to normal operations.
According to another aspect of the present disclosure, a system includes a
first
reactor, a second reactor, at least one inlet configured to transfer
wastewater to the
first reactor and the second reactor, and a flow control device. The flow
control
device is coupled to the at least one inlet. The flow control device is
configured to
operate in a first mode of operation during a first period of time and a
second mode of
operation during a second period of time. In the first mode of operation, the
flow
control device is configured to transfer more than half of the wastewater to
the first
reactor for a first duration via the at least one inlet, and subsequently
transfer more
than half of the wastewater to the second reactor for a second duration via
the at least
one inlet. In the second mode of operation, the flow control device is
configured to
transfer approximately half of the wastewater to the first reactor via the at
least one
inlet and simultaneously transfer approximately half of the wastewater to the
second
reactor via the at least one inlet.
According to another aspect of the present disclosure, a system includes a
first
reactor, a second reactor, at least one inlet configured to transfer
wastewater to the
first reactor and the second reactor, each reactor having an outlet for
releasing
treated wastewater or effluent and a flow control device. The flow control
device is
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coupled to the outlet of the first reactor and to the outlet of the second
reactor. The
flow control device is configured to operate in a first mode of operation
during a first
period of time, a second mode of operation during a second period of time and
a third
mode of operation during a third period of time. In the first mode of
operation, the flow
.. control device is configured to prevent effluent or treated wastewater from
exiting the
system via the outlet of the first reactor while permitting exit of treated
wastewater
from the outlet of the second reactor. In the second mode of operation, the
flow
control device is configured to prevent effluent or treated wastewater from
exiting the
outlet of the second reactor while permitting exit of effluent from the outlet
of the first
reactor. In the third mode of operation, the flow control device is configured
to permit
exit of effluent from the outlet of the first reactor and the outlet of the
second reactor.
According to another aspect of the present disclosure, there is provided a
method for improving ammonia removal from wastewater during a cold weather
period including: in a sewage treatment system including at least a first
attached
growth reactor and a second attached growth reactor, during a warm weather
period,
transferring a significant portion of wastewater to the first attached growth
reactor for
a first period of the warm weather period, then transferring a significant
portion of the
wastewater to the second attached growth reactor for a second period of the
warm
weather period; and during the cold weather period, transferring approximately
half of
the wastewater to the first attached growth reactor and approximately half of
the
wastewater to the second attached growth reactor.
As will be appreciated by one of skill in the art and as discussed herein,
"transferring approximately half of the wastewater to the first attached
growth reactor
and approximately half of the wastewater to the second attached growth
reactor" may
refer to a specific moment in time (that is, that each reactor receives
approximately
half of the wastewater consistently during the cold weather period) or over
the
duration of the cold weather period (that is, at the end of the cold weather
period,
each reactor has received approximately half of the total volume of wastewater
for the
entire cold weather period).
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Alternatively, as discussed herein, at the end of the warm weather period, the
nitrifying bacteria biomass within one of the growth reactors is estimated and
wastewater is transferred to the specific one of the growth reactors according
to the
estimated nitrifying bacteria biomass within the specific one of the growth
reactors
during or during at least a portion of the cold weather period.
According to a further aspect of the present disclosure, there is provided a
method of improving ammonia removal from waste water during a cold weather
period
including: in a sewage treatment system including at least two attached growth
reactors, each respective attached growth reactor receiving an influent of
wastewater,
transferring a volume of the wastewater to the two attached growth reactors,
wherein
the volume is transferred such that a first attached growth reactor receives a
larger
portion of the volume than a second attached growth reactor for a first period
of a
warm weather period and the second attached growth reactor receives a larger
portion of the volume than the first attached growth reactor for a second
period of the
warm weather period on an alternating basis; and transferring the volume of
wastewater to the first attached growth reactor and the second attached growth
reactor approximately equally between the two attached growth reactors during
the
cold weather period.
As will be appreciated by one of skill in the art, providing each reactor with
a
larger portion of the wastewater for a period of time on an alternating basis
increases
the nitrifying bacteria biomass compared to what it would be with both
reactors each
receiving a constant volume during the warm weather period. During the cold
weather
period, each reactor has greater capacity to nitrify wastewater by virtue of
the
increased nitrifying bacteria biomass. While distributing approximately half
of the
waste to each reactor will result in most effective nitrification of the
wastewater, this
may not be necessary. For example, it may be that each reactor or at least one
of the
reactors has sufficient nitrifying bacteria biomass to nitrify greater than
half of the
wastewater, as discussed herein. Furthermore, over the course or duration of
the cold
weather period, each reactor may receive approximately half of the total
volume of the
wastewater. This may be done by continuously transferring approximately half
of the
CA 3034498 2019-02-21
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volume to each reactor which it is believed will result in better performance
or by
transferring substantially all of the volume to one reactor and taking the
effluent from
the first reactor and transferring substantially all of the volume to the
influent of the
second reactor.
According to a further aspect of the present disclosure, there is provided a
method of improving ammonia removal from waste water during a cold weather
period
including: in a sewage treatment system including at least two attached growth
reactors, each respective attached growth reactor receiving an influent of
wastewater,
= transferring a volume of the Wastewater to the two attached growth
reactors, wherein
the volume is transferred such that a first attached growth reactor receives a
larger
portion of the volume than a second attached growth reactor for a first period
of a
warm weather period and the second attached growth reactor receives a larger
portion of the volume than the first attached growth reactor for a second
period of the
warm weather period on an alternating basis; and, during a cold weather
period,
transferring the volume of wastewater to the first attached growth reactor,
recovering
effluent from the first attached growth reactor and transferring the effluent
from the
first attached growth reactor to the second attached growth reactor.
According to yet another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass in an attached growth reactor
during
a warm weather period including: in a sewage treatment system including at
least two
attached growth reactors, each respective attached growth reactor receiving an
influent of wastewater, transferring a volume of the wastewater to the two
attached
growth reactors, wherein the volume is transferred such that a first attached
growth
reactor receives a larger portion of the volume than a second attached growth
reactor
for a first period of the warm weather period and the second attached growth
reactor
receives a larger portion of the volume than the first attached growth reactor
for a
second period of the warm weather period on an alternating basis.
According to a still further aspect of the present disclosure, there is
provided a
method for improving ammonia removal from wastewater during a cold weather
period including: in a sewage treatment system including an attached growth
reactor
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separated into at least a first attached growth reactor chamber and a second
attached
growth reactor chamber, during a warm weather period, transferring a
significant
portion of wastewater to the first attached growth reactor chamber for a first
period of
the warm weather period, then transferring a significant portion of the
wastewater to
the second attached growth reactor chamber for a second period of the warm
weather
period; and during the cold weather period, transferring approximately half of
the
wastewater to the first attached growth reactor chamber and approximately half
of the
wastewater to the second attached growth reactor chamber.
Alternatively, as discussed herein, at the end of the warm weather period, the
nitrifying bacteria biomass within one of the growth reactors is estimated and
wastewater is transferred to the specific one of the growth reactors according
to the
estimated nitrifying bacteria biomass, that is, according to the ability of
the nitrifying
bacteria biomass to treat the incoming wastewater under expected conditions,
for
example, projected weather conditions and/or projected water temperatures,
within
the specific one of the growth reactors during or during at least a portion of
the cold
weather period.
According to another aspect of the present disclosure, there is provided a
method of aeration or oxygenation for increasing nitrifying bacteria biomass
within a
wastewater treatment system including: in an attached growth reactor including
a
.. plurality of stationary fixed media for supporting biomass growth, at least
two of said
plurality of stationary fixed media including at least one oxygen intake port
for
receiving air or oxygen and at least one aeration or oxygen dispersion port
connected
to the respective oxygen intake port for dispersing oxygen into the reactor,
connecting
the at least two of said plurality of stationary fixed media to an aeration
source via the
respective at least one oxygen intake port; and supplying air or oxygen to a
first one
of the at least two of the plurality of stationary fixed media for a first
period of time,
and then supplying air or oxygen to a second one of the at least two of the
plurality of
stationary fixed media for a second period of time.
According to another aspect of the present disclosure, there is provided a
method of aeration or oxygenation for increasing nitrifying bacteria biomass
within a
CA 3034498 2019-02-21
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wastewater treatment system: including at least a first attached growth
reactor and a
second attached growth reactor, said first attached growth reactor being
connected to
the second attached growth reactor such that treated effluent from the first
attached
growth reactor is transferred to the second attached growth reactor, each
growth
reactor including a plurality of media for supporting bacterial biomass growth
and
each attached growth reactor including at least one oxygen or air intake port
for
supplying air or oxygen to the respective growth reactor, during a first
period of time,
supplying oxygen to the first reactor at a first level and during a second
period of time,
reducing air or oxygen supplied to the first reactor to a second level while
supplying
oxygen or air to the second reactor.
As will be appreciated by one of skill in the art, the second level of
aeration
and/or oxygenation is such that treatment of the wastewater within the first
reactor is
reduced to an extent such that ammonia passes from the first reactor to the
second
reactor for nitrification in the second reactor which in turn promotes an
increase in
nitrifying bacteria biomass within the second reactor. It is of note that the
second level
can be determined through routine experimentation or may be estimated based on
knowledge of the operating conditions of the sewage treatment systems.
In some embodiments, the first period of time and the second period of time
are during a warm weather period as described herein.
In some embodiments, the media for supporting bacterial biomass growth is
stationary media.
According to another aspect of the present disclosure, there is provided a
method for aeration or oxygenation or for increasing nitrifying bacteria
biomass within
a wastewater treatment system including: in an attached growth reactor
including a
plurality of stationary fixed media for supporting biomass growth, at least
two of said
plurality of stationary fixed media including at least one oxygen port
dedicated to
providing oxygen to said stationary media and supplying air or oxygen to at
least the
first one of the at least two units or groups of units of stationary media for
a first period
of time, and then supplying air or oxygen to a second one of the at least two
of the
plurality of stationary fixed media for a second period of time.
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As discussed herein, by turning on the oxygen to a respective one stationary
fixed media, growth of nitrifying bacteria on that specific stationary fixed
media is
promoted during this oxygenation period. As will be appreciated by one of
skill in the
art, aeration at all of the stationary fixed media simultaneously would lead
to growth of
nitrifying bacteria at only those respective stationary fixed media close
enough to the
inlet of the growth reactor, that is, to the food source for the bacteria, to
receive
ammonia. However, by alternating the location of the aeration or oxygenation,
nitrifying bacteria growth is promoted at all aerated stationary fixed media.
According to another aspect of the present disclosure, there is provided a
method for increasing nitrifying bacteria biomass in an attached growth
reactor
including: providing an attached growth reactor system having a first end
region and a
second end region wherein the first end region and the second end region are
both
capable of acting as an inlet or an outlet; during a warm weather period,
transferring a
volume of wastewater into the attached growth reactor at the first end region
and
removing treated wastewater from the reactor at the second end region for a
first
period of the warm weather period, then transferring the volume of wastewater
into
the attached growth reactor via the second end region and removing treated
from the
reactor at the first end region for a second period of the warm weather period
on an
alternating basis.
According to still another aspect of the present disclosure, there is provided
a
method for increasing nitrifying bacteria biomass including: in an attached
growth
reactor including a plurality of stationary fixed media for supporting biomass
growth,
said attached growth reactor having an inlet region for accepting wastewater
and an
outlet region, said wastewater having a direction of flow through the reactor
from the
inlet region to the outlet region, each respective one of the plurality of
stationary fixed
media being positioned within the reactor sequentially from the inlet region
to the
outlet region, periodically removing a respective one stationary fixed medium
proximal
to the inlet region and placing said respective one stationary fixed medium
more distal
to the inlet region.
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According to another aspect of the present disclosure, there is provided a
method for increasing nitrifying bacteria biomass including: in an attached
growth
reactor system including at least a first attached growth reactor and a second
attached growth reactor, each attached growth reactor including a plurality of
moving
media for supporting biomass growth thereon, the first attached growth reactor
having
an inlet region for accepting wastewater and the second attached growth
reactor
having an outlet region, said wastewater having a direction of flow through
the
attached growth reactor system from the inlet region to the outlet region,
periodically
removing moving media from the first attached growth reactor and transferring
said
moving media to the second attached growth reactor.
In some embodiments, during the warm weather period, substantially all of the
wastewater is transferred to the first attached growth reactor for a first
period of time
and subsequently all of the wastewater is transferred to the second attached
growth
reactor for a second period of time.
According to another aspect, there is provided a method of improving ammonia
removal from waste water during cold weather including:
in a sewage treatment system including at least two attached growth reactors,
each respective attached growth reactor having an inlet distribution point in
the
attached growth reactor for receiving an influent of wastewater,
during a warm weather period, transferring an approximately constant volume
of the wastewater to the at least two attached growth reactors, wherein the
volume is
transferred such that a first attached growth reactor receives a larger
portion of the
volume than a second attached growth reactor for a first period of the warm
weather
period and the second attached growth reactor receives a larger portion of the
volume
than the first attached growth reactor for a second period of the warm weather
period;
and
transferring substantially more than half, for example 60-100% the volume of
wastewater to the first attached growth reactor and the remaining volume of
wastewater to second attached growth reactor during a cold weather period.
Alternatively, as discussed herein, at the end of the warm weather period, the
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nitrifying bacteria biomass within one of the growth reactors is estimated and
wastewater is transferred to the specific one of the growth reactors according
to the
estimated nitrifying bacteria biomass within the specific one of the growth
reactors
during at least a portion of or during the cold weather period. As will be
apparent, in
these embodiments, one reactor may receive substantially more than half of the
wastewater during the cold weather period, provided that the nitrifying
bacteria
biomass is sufficient to treat the wastewater, as discussed herein.
According to another aspect of the present disclosure, a system includes a
first
reactor, a second reactor, at least one inlet configured to transfer
wastewater to the
first reactor and the second reactor, and a flow control device. The flow
control
device is coupled to the at least one inlet. The flow control device is
configured to
operate in a first mode of operation during a first period of time and a
second mode of
operation during a second period of time. In the first mode of operation, the
flow
control device is configured to transfer more than half of the wastewater to
the first
reactor for a first duration via the at least one inlet, and subsequently
transfer more
than half of the wastewater to the second reactor for a second duration via
the at least
one inlet. In the second mode of operation, the flow control device is
configured to
transfer substantially more than half, for example 60-100% of the wastewater
to the
first reactor via the at least one inlet and simultaneously transfer the
remaining
wastewater to the second reactor via the at least one inlet.
Alternatively, as discussed herein, at the end of the warm weather period, the
nitrifying bacteria biomass within one of the growth reactors is estimated and
wastewater is transferred to the specific one of the growth reactors according
to the
estimated nitrifying bacteria biomass within the specific one of the growth
reactors
during at least a portion of or during the cold weather period.
According to another aspect of the present disclosure, there is provided a
method for improving ammonia removal from wastewater during a cold weather
period including: in a sewage treatment system including at least a first
attached
growth reactor and a second attached growth reactor, during a warm weather
period,
transferring a significant portion of wastewater to the first attached growth
reactor for
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a first period of the warm weather period, then transferring a significant
portion of the
wastewater to the second attached growth reactor for a second period of the
warm
weather period; and during the cold weather period, transferring 0-100% of the
wastewater to the first attached growth reactor and the remaining wastewater
to the
second attached growth reactor.
Alternatively, as discussed herein, at the end of the warm weather period, the
nitrifying bacteria biomass within one of the growth reactors is estimated and
wastewater is transferred to the specific one of the growth reactors according
to the
estimated nitrifying bacteria biomass within the specific one of the growth
reactors
during or during at least a portion of the cold weather period.
According to a further aspect of the present disclosure, there is provided a
method of improving ammonia removal from waste water during a cold weather
period
including: in a sewage treatment system including at least two attached growth
reactors, each respective attached growth reactor receiving an influent of
wastewater,
transferring a volume of the wastewater to the two attached growth reactors,
wherein
the volume is transferred such that a first attached growth reactor receives a
larger
portion of the volume than a second attached growth reactor for a first period
of a
warm weather period and the second attached growth reactor receives a larger
portion of the volume than the first attached growth reactor for a second
period of the
warm weather period on an alternating basis; and transferring 0-100% the
volume of
wastewater to the first attached growth reactor and transferring the remaining
volume
of wastewater to the second attached growth reactor during the cold weather
period.
According to yet another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass in an attached growth reactor
during
a warm weather period including: in a sewage treatment system including at
least two
attached growth reactors, each respective attached growth reactor receiving an
influent of wastewater, transferring a volume of the wastewater to the two
attached
growth reactors, wherein the volume is transferred such that a first attached
growth
reactor receives a larger portion of the volume than a second attached growth
reactor
for a first period of the warm weather period and the second attached growth
reactor
CA 3034498 2019-02-21
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receives a larger portion of the volume than the first attached growth reactor
for a
second period of the warm weather period on an alternating basis.
Alternatively, as discussed herein, at the end of the warm weather period, the
nitrifying bacteria biomass within one of the growth reactors is estimated and
wastewater is transferred to the specific one of the growth reactors according
to the
estimated nitrifying bacteria biomass within the specific one of the growth
reactors
during or during at least a portion of the cold weather period.
According to a still further aspect of the present disclosure, there is
provided a
method for improving ammonia removal from wastewater during a cold weather
period including: in a sewage treatment system including an attached growth
reactor
separated into at least a first attached growth reactor chamber and a second
attached
growth reactor chamber, during a warm weather period, transferring a
significant
portion of wastewater to the first attached growth reactor chamber for a first
period of
the warm weather period, then transferring a significant portion of the
wastewater to
the second attached growth reactor chamber for a second period of the warm
weather
period; and during the cold weather period, transferring 0-100% of the
wastewater to
the first attached growth reactor chamber and transferring the remaining
wastewater
to the second attached growth reactor chamber.
According to another aspect of the present disclosure, there is provided a
method of aeration or oxygenation for increasing nitrifying bacteria biomass
including:
in an attached growth reactor including a plurality of media for supporting
biomass
growth, said reactor comprising at least two zones and each respective zone
including at least one oxygen port for receiving air or oxygen and a plurality
of
aeration or oxygen dispersion ports connected to a respective oxygen port for
dispersing air or oxygen into the respective zone, and supplying air or oxygen
to a first
respective zone or portion of reactor for a first period of time, and then
supplying air or
oxygen to a second respective zone for a second period of time.
In some embodiments, during the warm weather period, substantially all of the
oxygen is transferred to the first attached growth reactor for a first period
of time and
CA 3034498 2019-02-21
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subsequently all of the oxygen is transferred to the second attached growth
reactor for
a second period of time.
In other embodiments, oxygen is reduced in the first reactor for a period of
time
during the warm water period, causing ammonia to pass through the first
reactor with
a reduced rate of removal, increasing the ammonia entering the second reactor.
Alternatively, as discussed herein, at the end of the warm weather period, the
nitrifying bacteria biomass within one of the growth reactors is estimated and
wastewater is transferred to the specific one of the growth reactors according
to the
estimated nitrifying bacteria biomass within the specific one of the growth
reactors for
the duration of the cold weather period.
According to another aspect, there is provided a method of increasing
nitrifying
bacteria biomass for improving ammonia removal from waste water during cold
weather including:
in a sewage treatment system including at least one attached growth reactor
for treating wastewater, said wastewater being applied to the reactor at an
approximately consistent volume and consistent ammonia content over time,
increasing the wastewater load by increasing the volume of wastewater and/or
the ammonia content applied to the reactor for a period of time, thereby
increasing
nitrifying bacteria biomass within the reactor compared to standard operation
of the
sewage treatment system.
Preferably, the wastewater volume and/or ammonia content applied is
increased during a warm weather period when nitrifying bacteria are capable of
active
growth.
At the end of the warm weather period, the nitrifying bacteria biomass within
one of the growth reactors may be estimated and wastewater is transferred to
the
specific one of the growth reactors according to the estimated nitrifying
bacteria
biomass within the specific one of the growth reactors during or during at
least a
portion of the cold weather period.
According to another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass for improving ammonia removal
from
CA 3034498 2019-02-21
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wastewater during a cold weather period including: in a sewage treatment
system
including at least one attached growth reactor for treating wastewater, said
wastewater being applied to the reactor at an approximately consistent volume
and
consistent ammonia content over time, during a warm weather period, the sewage
treatment system treating influent wastewater in the reactor and producing
effluent
wastewater, recycling a portion of the effluent wastewater to a point of the
sewage
treatment system upstream of the reactor for a second period of time during
the warm
weather period, thereby increasing carbon and/or ammonia load and increasing
nitrifying bacteria biomass in the reactor compared to standard operation of
the
reactor.
During the cold weather period, the attached growth reactor(s) treats influent
wastewater and produces effluent wastewater without recycling effluent
wastewater
upstream or while recycling at a reduced rate.
According to another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria for improving ammonia removal from
wastewater during a cold weather period including: in a sewage treatment
system
including at least one attached growth reactor for treating wastewater, said
wastewater being applied to the reactor at an approximately consistent volume
and
consistent ammonia content over time, during a first period of the warm
weather
period, increasing a rate of wastewater flow through the reactor for example
by
displacing the wastewater containing ammonia using another water source, for
example, water from another part of the sewage treatment system including but
not
limited to effluent from the nitrification reactor or other downstream
treatment process
to increase the loading in the attached growth reactor, and during cold water,
the
= 25 attached growth reactor(s) treats influent wastewater and produces
effluent
wastewater without supplementing the flow using an additional water source.
According to another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass for improving ammonia removal
from
wastewater during a cold weather period including: in a sewage treatment
system
including at least one attached growth reactor, during a first period of the
warm
CA 3034498 2019-02-21
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weather period, treating influent wastewater and producing effluent
wastewater, and
during a second period of the warm weather period, a portion of the wastewater
stored within the system is combined with the influent wastewater to increase
carbon
and/or ammonia load.
During the cold weather period, the attached growth reactor(s) treats influent
wastewater without the additional stored wastewater and produces effluent
wastewater.
According to another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass for improving ammonia removal
from
wastewater during a cold weather period including: in a sewage treatment
system
including at least one attached growth reactor for treating wastewater, said
wastewater being applied to the reactor at an approximately consistent volume
and
consistent ammonia content over time, during a first period of the warm
weather
period, increasing the ammonia content of the waste water for example by
reducing
the treatment capacity of processes up-front of the attached growth
reactor(s),
thereby increasing carbon and/or ammonia load and increasing nitrifying
bacteria
biomass.
During the cold weather period, the attached growth reactor(s) treating
influent
wastewater and producing effluent wastewater without reduced treatment
capacity up-
front.
Herein, "to increase carbon and/or ammonia load" is used to describe the
reason for chemically or physically increasing the wastewater load to the
attached
growth reactor(s) during the warm weather period. However, embodiments wherein
other chemical or physical means are used to increase the carbon or ammonia
load to
the attached growth reactor(s) are to be understood as being possible and
encompassed in all embodiments.
Herein, "a first attached growth reactor" and "a second growth reactor" are
used in the singular. However, embodiments wherein there are multiple attached
growth reactors, for example, two or more attached growth reactors, receiving
an
increased portion of wastewater intake are to be understood as being possible
and
CA 3034498 2019-02-21
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encompassed in embodiments when only a single attached growth reactor is being
referenced. For example, "a first attached growth reactor" may refer to more
than one,
for example, two, three, four or more attached growth reactors which are
grouped
together so as to effectively act as a single attached growth reactor.
Herein, "transferring approximately half of the wastewater to the first
attached
growth reactor chamber and approximately half of the wastewater to the second
attached growth reactor chamber" and "transferring 60-100% of the wastewater
to the
first attached growth reactor chamber and transferring the remaining
wastewater to
the second attached growth reactor chamber" are used to describe the nature of
wastewater supplied to the attached growth reactors. However, embodiments
wherein
multiple attached growth reactors, for example, two or more attached growth
reactors,
operate in parallel, series, and/or any combination are to be understood as
being
possible and encompassed in all embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic drawing of an embodiment of a sewage treatment
system including two submerged attached growth reactors.
Figure 2 is a schematic drawing of an embodiment of a sewage treatment
system including two separate chambers within one reactor.
Figure 3 is a schematic drawing illustrating an embodiment of a sewage
treatment system in which application of wastewater to the reactors is varied
over
time.
DETAILED DESCRIPTION
Unless defined otherwise, all technical and scientific terms used herein have
the same meaning as commonly understood by one of ordinary skill in the art to
which
the invention belongs. Although any methods and materials similar or
equivalent to
those described herein can be used in the practice or testing of the present
invention,
the preferred methods and materials are now described.
As used herein, 'heterotrophic bacteria' refers to bacteria capable of
utilizing
CA 3034498 2019-02-21
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organic material. It is of note that generas of such bacteria are well known
within the
art and one of skill in the art will understand that this refers to specific
bacteria of this
type known to be present in for example treatment lagoons.
As used herein, nitrifying bacteria refers to any bacteria capable of
oxidizing
ammonia to nitrite, nitrite to nitrate, or ammonia to nitrate. It is of note
that such
bacteria are well known within the art and one of skill in the art will
understand that
this refers to specific bacteria of this type known to be present in for
example
treatment lagoons.
As used herein, "winter months" or "cold weather months" or "cold months" or
.. "cold weather" refers to months or other durations of time in which the
water
temperature approaches or is less than 4 degrees Celsius, or is less than a
threshold
temperature corresponding to a threshold rate of bacteria activity (e.g.,
bacteria
growth; nitrification). The water temperature may be the temperature of
effluent water
leaving the reactor or the temperature of wastewater (e.g., partially treated
wastewater) in the reactor.
As used herein, "warm weather months" or "warm months" or "warm weather"
refers to months or other durations of time in which the water temperature is
typically
considerably higher than 4 degrees Celsius (e.g., greater than or equal to 10
degrees
Celsius, greater than or equal to 15 degrees Celsius). The distinction between
warm
weather and cold weather may correspond to a rate of bacteria growth in the
reactor.
For example, the rate of bacteria growth can increase as a function of
temperature.
At a first temperature (e.g., 4 degrees Celsius; between 2 degrees Celsius and
10
degrees Celsius; between 4 degrees Celsius and 7 degrees Celsius), the rate of
bacteria growth may be less than a threshold rate sufficient to sustain the
treatment
processes desired for the reactors. At a second temperature (e.g., greater
than or
equal to 10 degrees Celsius), the rate of bacterial growth may be greater than
or
equal to the threshold rate.
Described herein is an attached growth reactor system which provides
nitrification (ammonia removal) from wastewater in cold to moderate climates,
.. specifically, during cold weather or cold weather months. Specifically,
described
CA 3034498 2019-02-21
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herein are methods for increasing nitrifying bacteria biomass within the
reactor(s) so
that the sewage treatment system or wastewater treatment system has greater
nitrifying bacteria biomass and/or greater nitrifying capacity during cold
weather
periods.
As discussed herein and as will be apparent to one knowledgeable in the field
of wastewater treatment, sewage treatment systems are designed to treat a
specific
volume of wastewater over a given period of time. As discussed herein, that
volume
may be estimated or predicted based on knowledge of the area that the sewage
treatment system is servicing as well as other factors such as the population
size of
the area, what percentage of the area is residential and the types of
businesses within
the service area as well as previous usage patterns. While the specific volume
applied
to the system may vary considerably over a short period of time, over time,
the
volume applied to the system by the users will generally follow predicted
usage
patterns and therefore can be referred to as being relatively consistent or
constant.
Reference is made herein to "normal operations" or "standard operations" of
the sewage treatment system. As will be apparent to one of skill in the art,
this refers
to raw wastewater entering the waste treatment system at the entry point of
the
sewage treatment system and passing through the sewage treatment system under
normal or standard design conditions, that is, without transient or temporary
supplementation and/or volume and/or content, for example, amounts of oxygen
and/or ammonia, increases or decreases, as discussed herein.
As is known by those of skill in the art, within a growth reactor, nitrifying
bacteria use organic and inorganic compounds as a food source, for example,
oxidizing ammonia to nitrate (nitrification). This process takes place only
where there
is sufficient ammonia and oxygen. In a growth reactor of a waste treatment
system
operating under standard conditions, nitrifying bacteria tend to grow where
there is
available food.
As discussed herein, the nitrifying bacteria biomass in a given growth reactor
may be measured or it may be estimated. For example, the nitrifying bacteria
biomass
may be measured or estimated by determining the nitrification capacity within
the
CA 3034498 2019-02-21
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specific reactor by measuring and/or monitoring the amount of ammonia entering
and
exiting the specific growth reactor, or by measuring the nitrites and nitrates
produced
in the reactor. Alternatively, the nitrifying bacteria biomass may be
estimated based
on knowledge of the sewage treatment system and of the interventions carried
out to
increase the nitrifying bacteria biomass.
As discussed herein, an estimated or predicted nitrifying bacteria biomass may
be used to estimate or predict the nitrification capacity of a given growth
reactor under
different conditions, for example, under different water temperatures. As
discussed
herein, this estimated or predicted nitrifying bacteria biomass may be used to
determine what quantity of wastewater a specific growth reactor is capable of
treating
under specific conditions, for example, under given water temperatures.
In some embodiments, the attached growth reactor is a submerged attached
growth reactor (SAGR), a moving media attached growth reactor (MMAGR) or a
stationary media attached growth reactor (SMAGR). One example of an MMAGR is a
Moving Bed Biofilm Reactor (MBBR), as discussed below. One example of a SMAGR
is a stationary fixed film media attached growth reactor, as discussed below.
However, as will be appreciated by one of skill in the art, any suitable
growth reactor
which receives an influent that undergoes bacterial nitrification during cold
weather
months can be used in combination with the present disclosure.
It is of note that there are many possible arrangements that will result in a
reactor having a functionality similar to a SAGR, SMAGR or MBBR which will be
readily apparent to one of skill in the art.
In some embodiments, the SAGR includes a media bed for example, a gravel
or rock (or other similar material) bed with one or more horizontal chambers
.. throughout. The chamber system is used to distribute the wastewater flow
across the
width of the cell, and a horizontal collection chamber at the outlet of the
system is
used to collect treated water. This distribution is desired to ensure
horizontal flow
throughout the gravel media and optimize hydraulic efficiency, although
alternate
(vertical) flow paths could achieve similar treatment results, and are
contemplated by
this invention. Linear aeration proximate to the bottom of the SAGR provides
aerobic
CA 3034498 2019-02-21
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conditions that are required for nitrification. In some embodiments, the
gravel bed
may be covered with a layer of an insulating material, for example, peat or
wood
chips.
Two examples of submerged attached growth reactor systems are shown in
Figures 1 and 2.
It is important to note that while these figures illustrate two embodiments of
SAGR treatment systems, various features of these embodiments, including but
not
limited to distributing wastewater flow unequally between two or more reactors
over
time or otherwise increasing the biomass of nitrifying bacteria within one or
more
reactors and/or within one or more chambers of one reactor, may be applied to
other
attached growth reactor systems.
As compared to existing systems, systems and methods in accordance with
embodiments of the present disclosure can increase nitrifying bacteria biomass
within
the attached growth reactor system so that there is increased nitrifying
bacteria
biomass to nitrify wastewater during a cold weather period of time (e.g., a
cold
weather period of time following a warm weather period of time in which
wastewater is
transferred unequally to reactors or reactor cells of the attached growth
reactor
system).
Referring now to Figure 1, a sewage treatment system including a first reactor
1 (e.g., attached growth reactor) and a second reactor 2 (e.g., attached
growth
reactor) is shown according to an embodiment of the present disclosure. Each
reactor
1,2 is defined by a base 30 and a plurality of walls 32, for example, three or
four or
more vertical or sloped walls. The walls 32 and the base 30 of each reactor 1,
2 are
lined with a semi-impermeable or impermeable liner 34. The top of each reactor
1, 2
is defined by the level of wastewater (e.g., partially treated wastewater)
with the
respective reactor 1, 2. The top is covered with an insulation layer 20 that
is on the
upper surface of the wastewater in the reactor 1, 2. The insulation layer 20
may be of
any suitable material as discussed herein and as known in the art, for
example, wood
chips, mulch, peat, shredded tires or the like. Any suitable material can act
as
insulation.
CA 3034498 2019-02-21
23
In some embodiments, the base 30 of each reactor 1, 2 includes an aeration
system 40, media bed 50 and effluent collector 60. In some embodiments, the
aeration system 40 includes a plurality of aeration diffusers 42 connected to
an air or
oxygen supply and spaced along the base 30 of the reactors 1, 2. In some
embodiments, the aeration system is arranged such that the main aeration
headers
are accessible at the upper surface of the wastewater. In some embodiments,
the
aeration lines run perpendicular to the direction of wastewater flow through
the reactor
1, 2 although in other embodiments the aeration lines run parallel to the
direction of
wastewater flow. In some embodiments, the aeration system 40 includes acid
cleaning means for cleaning of the diffusers in situ.
As shown in Figure 1, the media bed 50 can be placed over the aeration
system 40 and may be any suitable material that will have pore spaces for air
or
oxygen generated by the aeration diffusers 42 at the base 30 of the of the
reactor 1, 2
to pass through the material bed 50 so as to aerate the wastewater within the
reactor
1, 2. As discussed herein, the media bed 50 may be composed of any suitable
material, for example, any material that passes through a 1.5 inch screen such
as
suitably sized rocks or gravel, although other suitable materials will be
readily
apparent to one of skill in the art.
The effluent collector 60 is proximal to the base 30 in each reactor 1, 2.
Treated wastewater is removed from the reactors 1, 2 via the effluent
collector 60.
The reactors 1, 2 also include one or more inlets 70 for transferring of
wastewater into the reactor system for treatment. In some embodiments, as
shown in
Figure 1, the inlets 70 comprise stacked chambers for wastewater (e.g.,
influent
wastewater) flow distribution. The inlets 70 may include flow distribution
piping using
orifices for flow control.
In some embodiments, the reactors 1, 2 are configured to receive wastewater
based on operation of a flow control device 10 (e.g., a flow splitter device,
a manifold,
valve(s)). The flow control device 10 can be configured to receive wastewater
and
transfer the wastewater to one or both of the reactors 1, 2. The flow control
device 10
can be configured to control a flow rate of wastewater being transferred to
one or both
CA 3034498 2019-02-21
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of the reactors 1, 2. The flow control device 10 can be configured to receive
the
wastewater from a wastewater reservoir. In some embodiments, the flow control
device 10 includes a flow splitter weir configured to split the wastewater to
one or both
of the reactors 1, 2. In some embodiments, the flow control device 10 includes
one or
more standpipes configured to split the wastewater to one or both of the
reactors 1, 2.
In some embodiments, the flow control device 10 is configured to split the
wastewater
to one or both of the reactors 1, 2 based on at least one of back-pressure or
gravity.
In some the flow control device includes one or more actively controlled
valves
configured to split the wastewater to one or both of the reactors 1, 2. In
some
embodiments, the flow control device 10 includes or is coupled to one or more
effluent
collectors 60, such as to control the rate of wastewater flow through one or
both
reactors 1, 2 by opening or closing valves of effluent collector(s) 60.
In some embodiments, such as can be seen from Figure 1, each reactor 1, 2 is
physically separate from the other and the flow control device 10 controls
distribution
to each reactor 1, 2. That is, flow control device 10 can control what
percentage of the
volume of incoming wastewater each reactor 1, 2 receives for treatment.
In some embodiments, the flow control device 10 is configured to operate in a
plurality of modes. The flow control device 10 can operate in modes
corresponding to
a temperature of the wastewater to be transferred to the reactors 1, 2. For
example,
in a first mode of operation, the flow control device 10 can be configured to
transfer
more than half of the wastewater to the first reactor 1 for a first period of
time (e.g., via
inlet 70 coupled to the first reactor 1), and subsequently transfer more than
half of the
wastewater to the second reactor 2 for a second period of time (e.g., via
inlet 70
coupled to the second reactor 2). The flow control device 10 can be configured
to
operate in the first mode of operation during a warm weather period of time.
For
example, the flow control device 10 can be configured to operate in the first
mode of
operation while a temperature of the wastewater is greater than a threshold
temperature. The threshold temperature may be greater than 0.5 degrees Celsius
and less than 10 Celsius. The threshold temperature may be greater than 2
degrees
Celsius and less than 7 degrees Celsius. The threshold temperature may be 4
CA 3034498 2019-02-21
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degrees Celsius. In a second mode of operation, the flow control device 10 can
be
configured to transfer approximately half (e.g., greater than or equal to 45
percent and
less than or equal to 55 percent; greater than or equal to 48 percent and less
than or
equal to 52 percent, or greater than or equal to 40% and less than or equal to
60%, or
greater than or equal to 35% and less than or equal to 65%)) of the wastewater
to the
first reactor 1 and simultaneously transfer approximately half of the
wastewater (e.g.,
transfer the remainder of the wastewater) to the second reactor 2. The flow
control
device 10 can be configured to operate in the second mode of operation while
the
temperature of the wastewater is less than or equal to the threshold
temperature.
As will be appreciated by one of skill in the art, the above-described
distribution
method will provide very effective nitrification of the wastewater. However,
it is to be
understood that the wastewater for nitrification may be allocated to the
reactors based
on estimated nitrifying bacteria biomass and/or nitrification capacity of the
respective
reactor, under expected, predicted or projected weather conditions and/or
water
temperatures, as discussed herein. Accordingly, in some embodiments, one
reactor
may have sufficient nitrifying capacity to treat greater than half for example
much
greater than half of incoming wastewater during cold weather periods. However,
it is
to be understood that in some embodiments the wastewater is distributed to the
reactors such that each reactor receives approximately half of the wastewater
as
defined above over the duration of the cold weather period.
Referring now Figure 2, a system including a single reactor 101 is shown
according to an embodiment of the present disclosure. The reactor 101 can
incorporate features of the reactors 1, 2 described with reference to Figure
1. In
some embodiments, the reactor 101 includes a base 130 and three or more
vertical
walls 132 lined with a semi-permeable or impermeable liner 134. The top of the
reactor 101 is defined by the level of wastewater in the reactor 101 and is
covered by
an insulating layer 120 as discussed above.
Furthermore, the reactor 101 is separated into two separate chambers, a first
chamber 101A and a second chamber 101B. The first chamber 101A and the second
CA 3034498 2019-02-21
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chamber 1016 are separated for example by an internal divider or by a
hydraulic
gradient.
The reactor 101 can include inlets 160 configured to transfer wastewater flow
to the first chamber 101A and/or the second chamber 1016. As shown in Figure
2,
inlets 160 are arranged approximately in the midpoint along the length of the
reactor
101 and are arranged such that incoming wastewater flow can be directed to
either
the first chamber 101A or the second chamber 101B or both the first chamber
101A
and the second chamber 101B simultaneously, as discussed herein.
In some embodiments, the base 130 of the reactor 101 includes an aeration
system 140, media bed 150 and effluent collectors 170A and 170B, as discussed
below. In this embodiment, the aeration system 140 comprises a plurality of
aeration
diffusers 142 connected to an air or oxygen supply and spaced along the base
130 of
the reactor 101. In some embodiments, the aeration system is arranged such
that the
main aeration headers are accessible at the upper surface of the wastewater.
In some
embodiments, the aeration lines run perpendicular to the direction of
wastewater flow
through the reactor 101 although in other embodiments the aeration lines run
parallel
to the direction of wastewater flow. In some embodiments, the aeration system
140
includes acid cleaning means for cleaning of the diffusers in situ.
In some embodiments, such as shown in Figure 2, the media bed 150 is placed
over the aeration system 140 and may be any suitable material that will have
pore
spaces for air or oxygen generated by the diffusers 142 at the base 130 of the
of the
reactor 101 to pass through the material bed 150 so as to aerate the
wastewater
within the reactor 101. As discussed herein, the media bed 150 may be composed
of
any suitable material, for example, any material that passes through a 1.5
inch screen
such as suitably sized rocks or gravel, although other suitable materials will
be readily
apparent to one of skill in the art.
As can be seen in Figure 2, the first chamber 101A has an effluent collector
160A and the second chamber 101B has an effluent collector 160B respectively
for
the removal of treated wastewater as discussed herein.
CA 3034498 2019-02-21
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As can be seen in Figures 1 and 2, the overall direction of wastewater flow is
shown with a large arrow. Specifically, in both drawings, wastewater flows
away from
or downstream from the inlet 70 or 170 to the effluent collector 60 or 160A or
160B.
Smaller arrows show specific paths that may be taken by portions of the
wastewater
while curly arrows show the movement of air or oxygen through the media bed.
As will be appreciated by one of skill in the art, the term "aeration" is used
by
those of skill in the art and is understood to encompass supplying oxygen to a
system
in any suitable quantity, for example, as air or as pure oxygen as well as in
other
suitable forms.
In a SAGR, the media is typically rock although other suitable types of media
may be used. The media is stationary and flow is typically passed through the
media
in a plug flow configuration. While typically the influent point and the
effluent point are
at opposite ends of the system, in actuality, the influent point and the
effluent point
must only be a minimum suitable distance between each other.
As will be apparent to one of skill in the art, biomass quantity and type
(nitrifying bacteria vs heterotrophic bacteria) may not be uniformly
distributed across
the media. The SAGR is typically divided into two or more zones, which can be
defined by either a physical "wall' or barrier or by use of one or more
hydraulic
gradients to promote flow into a certain zone or by limiting dissolved oxygen
in a
certain zone to promote nitrification in a different part of the system that
has dissolved
oxygen.
As noted above, one example of an MMAGR is an MBBR. In an MBBR, the
media is generally of similar density to water, typically plastic or other
synthetic
materials that are suitable for attached bacterial growth, and is in
suspension. Mixing
using aeration or mechanical mixers keeps the media circulating throughout the
reactor and the entire reactor functions as a completely mixed reactor.
Because the
water volume/media/biomass volume is homogenous in the reactor, location of
the
influent and effluent points is not critical. That is, the influent and
effluent points can
either be separated by distance or can be close together. Typically, biomass
will be
CA 3034498 2019-02-21
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dispersed across all media in the reactor. Generally, rock is not used in an
MBBR
because it is too heavy and cannot be kept in suspension by mixing.
As discussed herein, in some embodiments, the MMAGR may be divided into
arbitrary zones. For example, according to another aspect of the present
disclosure,
there is provided a method for aeration or oxygenation or increasing
nitrifying bacteria
biomass including: in an attached growth reactor including a plurality of
media for
supporting biomass growth, said reactor comprising at least two zones and each
respective zone including at least one oxygen port for receiving air or oxygen
and a
plurality of aeration or oxygen dispersion ports connected to a respective
oxygen port
for dispersing air or oxygen into the respective zone, in a warm weather
period,
supplying air or oxygen to a first respective zone for a first period of time,
and then
supplying air or oxygen to a second respective zone for a second period of
time. As
will be appreciated by one of skill in the art, this will promote
nitrification within
different zones of the reactor which will in turn increase nitrifying bacteria
biomass
within that zone.
As discussed above, one example of an SMAGR is a stationary fixed film
media attached growth reactor. This stationary film does not require energy
for
suspension. Some examples of stationary fixed film media include but are by no
means limited to GE Membrane Aerated Bioreactor (MABR), Entex Webitat fixed
film
media, and Lemna Polishing Reactor (LPR). While it is not necessary for the
media to
remain in suspension, full mixing within the reactor is possible. In this
case, because
of the mixing, influent and effluent locations can vary considerably and,
similar to an
MBBR, there is no minimum distance requirement. As is the case with the MBBR,
physical barriers may be required to have distinct hydraulic zones within the
system,
as discussed above, although a hydraulic gradient could be used instead,
provided
the mixing of the suspension is at a suitable level for the hydraulic gradient
to
function.
As discussed herein, these stationary films that act as bacterial growth
supports may be arranged to be connected to an aeration or oxygenation source
so
that air and/or oxygen can be supplied to the biomass.
CA 3034498 2019-02-21
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As will be appreciated by one of skill in the art, in these embodiments, two
or
more respective stationary films may include one or more oxygen intake ports
for
receiving oxygen, either as air or as pure oxygen or some mixture thereof.
Furthermore, each respective one of the stationary films may include a
plurality of
outlet ports for dispersing oxygen through the stationary films and into the
interior of
the attached growth reactor.
As will be appreciated by one of skill in the art, each stationary fixed media
supports bacterial biomass growth thereon and as such each stationary fixed
medium
can be considered to represent a different zone within a given reactor.
Furthermore,
by aerating at a respective one or respective group of the fixed stationary
media for a
first period of time and then aerating at a different respective one or
respective group
of the fixed stationary media for a second period of time on an alternating
basis
increases the biomass of nitrifying bacteria within the reactor system, as
discussed
herein.
As such, the zone(s) that are being aerated changes over time. The end result
is that each of the aerated zones grows more nitrifying bacteria biomass
during the
period of time exposure to oxygen and/or air. However, if aeration at all
stationary
fixed media was constant or continuous, only the zones closest to the inlet
would
encounter sufficient nitrogen to support growth of nitrifying bacteria
biomass.
According to another aspect of the present disclosure, there is provided a
method of
aeration or oxygenation for increasing nitrifying bacteria biomass within a
wastewater
treatment system including: in an attached growth reactor including a
plurality of
stationary fixed media for supporting biomass growth, at least two of said
plurality of
stationary fixed media including at least one oxygen intake port for receiving
air or
oxygen and at least one aeration or oxygen dispersion port connected to the
respective oxygen intake port for dispersing oxygen into the reactor,
connecting the at
least two of said plurality of stationary fixed media to an aeration source
via the
respective at least one oxygen intake port; and supplying air or oxygen to a
first one
of the at least two of the plurality of stationary fixed media for a first
period of time,
CA 3034498 2019-02-21
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and then supplying air or oxygen to a second one of the at least two of the
plurality of
stationary fixed media for a second period of time.
As will be appreciated by one of skill in the art, the supply of air or oxygen
to
the first respective one of the stationary fixed media ceases or is reduced
when air or
oxygen is being supplied to the second respective one of the stationary fixed
media.
However, it is important to note that as used herein "a first respective one
of the
stationary fixed media for a first period of time, and then supplying air or
oxygen to a
second respective one of the stationary fixed media for a second period of
time" does
not exclude both or neither of the first respective one and the second
respective one
receiving air or oxygen at the same time. As will be apparent, the shorter the
overlap
time is, the more efficient production of nitrifying bacteria biomass will be
because
growth of nitrifying bacteria biomass will be promoted in a different zone,
that is, in the
zone being supplied air or oxygen.
Furthermore, "a first respective one" may refer to a single stationary fixed
medium or may refer to a group of stationary fixed media.
Furthermore, it is noted that in embodiments wherein there are more than two
stationary fixed medium, one respective stationary fixed media may be
receiving
oxygen or air at any given time while two or more respective stationary fixed
media
are not receiving air or oxygen.
The first period of time and the second period of time may be selected from
the
group consisting of: a few hours; a day; a few days; a week; a few weeks; a
month;
and a few months.
In some embodiments, each respective zone or each respective one of the
stationary fixed media may be connected to the aeration or oxygenation source
such
that aeration to specific zone or stationary fixed medium can be controlled
either
individually or in groups. As will be apparent to one of skill in the art, as
a result of this
arrangement, the aeration at individual zones or stationary fixed medium
members
can be controlled and regulated. This in turn means that specific
nitrification zones or
stationary fixed media zones can be created by controlling oxygenation to
these sites.
CA 3034498 2019-02-21
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As discussed herein, this represents one method for increasing nitrifying
bacteria biomass to a greater extent than would be present under normal
circumstances.
In some embodiments, the air applied to the zones may be heated, particularly
in cold weather months. As will be appreciated by one of skill in the art,
injection of
heated air proximal to the nitrifying bacteria biomass will create one or more
zones of
localized heat within the reactor which will in turn increase the efficiency
of the
nitrifying bacteria as discussed herein while also increasing oxygenation.
As will be appreciated by one of skill in the art, the temperature to which
the air
or oxygen is heated will depend on several factors for example but by no means
limited to the temperature of the wastewater in the reactor and the amount of
air or
oxygen being injected. For example, the air or oxygen may be heated to a
greater
extent if the wastewater temperature is close to 4 degrees Celsius and/or is a
relatively small amount of air or oxygen is being injected. However, it is
held that
optimization of these parameters represents routine experimentation for one of
skill in
the art.
According to another aspect, there is provided a method of improving ammonia
removal from waste water during cold weather including:
in a sewage treatment system including at least one attached growth reactor
for treating wastewater, said wastewater being generated for the sewage
treatment
system and applied to the reactor at an approximately consistent volume and
consistent ammonia content previously,
increasing the wastewater load by increasing the volume of wastewater and/or
the ammonia content applied to the reactor for a period of time, thereby
increasing
nitrifying bacteria biomass within the reactor.
Preferably, the wastewater volume and/or ammonia content applied is
increased during a warm weather period when nitrifying bacteria are capable of
active
growth.
The wastewater load may be increased by one or more of:
CA 3034498 2019-02-21
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recycling a portion of the effluent wastewater to a location within the
sewage treatment system upstream of the reactor;
increasing wastewater flow rate through the reactor compared to
standard operations;
reducing treatment efficiency of a portion of the sewage treatment
system upstream of the reactor compared to standard operations; or
increasing incoming wastewater volume entering the reactor compared
to standard operations.
According to another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass for improving ammonia removal
from
wastewater during a cold weather period including: in a sewage treatment
system
including at least one attached growth reactor for treating wastewater, said
wastewater being applied to the reactor at an approximately consistent volume
and
consistent ammonia content over time, during a warm weather period, the sewage
treatment system treating influent wastewater in the reactor and producing
effluent
wastewater, recycling a portion of the effluent wastewater to a point of the
sewage
treatment system upstream of the reactor for a second period of time during
the warm
weather period, thereby increasing carbon and/or ammonia load and increasing
nitrifying bacteria biomass in the reactor compared to standard operation of
the
reactor.
As discussed herein, at the end of the warm weather period, the nitrifying
bacteria biomass within one of the growth reactors is estimated and wastewater
is
transferred to the specific one of the growth reactors according to the
estimated
nitrifying bacteria biomass within the specific one of the growth reactors for
the
duration of the cold weather period.
During the cold weather period, the attached growth reactor(s) treating
influent
wastewater and producing effluent wastewater without recycling effluent
wastewater
or reducing wastewater recycling upstream. As will be appreciated by one of
skill in
the art and as discussed herein, the key consideration is if the nitrifying
bacteria
biomass within a given reactor is capable of treating the influent wastewater
during
CA 3034498 2019-02-21
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cold weather periods. As such, for example the amount of wastewater being
recycled
can be reduced but still be increased compared to standard operations,
providing that
the load of the influent wastewater to a given reactor is still such that the
respective
reactor can effectively treat the influent wastewater. In some cases, this may
be
referred to as "without recycling" or "without reduced treatment capacity" but
it is to be
understood that this does not preclude for example some recycling provided
that the
degree of recycling is such that the nitrifying bacteria biomass in the
specific reactor is
capable of nitrifying the influent wastewater.
According to another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass for improving ammonia removal
from
wastewater during a cold weather period including: in a sewage treatment
system
including at least one attached growth reactor for treating wastewater, said
wastewater being applied to the reactor at an approximately consistent volume
and
consistent ammonia content over time, during a first period of the warm
weather
period, increasing a rate of wastewater flow through the reactor for example
by
displacing the wastewater containing ammonia using another water source, for
example, water from another part of the sewage treatment system including but
not
limited to effluent from the nitrification reactor or other downstream
treatment process
to increase the loading in the attached growth reactor.
During cold water, the attached growth reactor(s) treats influent wastewater
and produces effluent wastewater without supplementing the flow using an
additional
water source.
At the end of the warm weather period, the nitrifying bacteria biomass within
one of the growth reactors is estimated and wastewater is transferred to the
specific
one of the growth reactors according to the estimated nitrifying bacteria
biomass
within the specific one of the growth reactors for during or during at least
part of the
cold weather period.
According to another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass for improving ammonia removal
from
wastewater during a cold weather period including: in a sewage treatment
system
CA 3034498 2019-02-21
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including at least one attached growth reactor, during a first period of the
warm
weather period, treating influent wastewater and producing effluent
wastewater,
during a second period of the warm weather period, wastewater stored within
the
system is combined with the influent wastewater to increase carbon and/or
ammonia
load compared to standard operations, thereby increasing nitrifying bacteria
biomass.
During the cold weather period, the attached growth reactor(s) treats influent
wastewater without the additional stored wastewater or reduced additional
wastewater
as discussed above and produces effluent treated wastewater.
At the end of the warm weather period, the nitrifying bacteria biomass within
one of the growth reactors is estimated and wastewater is transferred to the
specific
one of the growth reactors according to the estimated nitrifying bacteria
biomass
within the specific one of the growth reactors during or during a part of the
cold
weather period.
According to another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass for improving ammonia removal
from
wastewater during a cold weather period including: in a sewage treatment
system
including at least one attached growth reactor for treating wastewater, said
wastewater being applied to the reactor at an approximately consistent volume
and
consistent ammonia content over time, during a first period of the warm
weather
period, increasing the ammonia content of the waste water for example by
reducing
the treatment capacity of processes up-front of the attached growth
reactor(s),
thereby increasing carbon and/or ammonia load and increasing nitrifying
bacteria
biomass; and during the cold weather period, the attached growth reactor(s)
treating
influent wastewater and producing effluent wastewater without reduced
treatment
capacity or with less reduced treatment capacity up-front, as discussed above.
Herein, "to increase carbon and/or ammonia load" is used to describe the
reason for chemically or physically increasing the wastewater load to the
attached
growth reactor(s) during the warm weather period. However, embodiments wherein
other chemical or physical means are used to increase the carbon or ammonia
load to
CA 3034498 2019-02-21
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the attached growth reactor(s) are to be understood as being possible and
encompassed in all embodiments.
As will be appreciated by one of skill in the art, these methods increase the
amount of carbon and/or ammonia being applied to the reactor. The additional
ammonia will promote growth of additional nitrifying bacteria, for example, by
creating
a larger colony of nitrifying bacteria within the reactor or reactor chamber
and/or by
promoting the establishment of new colonies of nitrifying bacteria.
In another aspect of the present disclosure, there is provided a method for
increasing nitrifying bacteria biomass including:
in an attached growth reactor system including a plurality of stationary fixed
media for supporting biomass growth, said attached growth reactor system
having an
inlet region for accepting wastewater and an outlet region, said wastewater
having a
direction of flow through the reactor from the inlet region to the outlet
region, each
respective one of the plurality of stationary fixed media being positioned
within the
reactor sequentially from the inlet region to the outlet region,
periodically removing a respective one stationary fixed medium from a position
in sequence that is more proximal to the inlet region and placing said
respective one
stationary fixed medium in a position in sequence that is more distal to the
inlet
region.
The attached growth reactor system may be a single attached growth reactor
or may be two or more attached growth reactors.
In another aspect of the present disclosure, there is provided a method for
increasing nitrifying bacteria biomass including:
in an attached growth reactor system including at least a first attached
growth
reactor and a second attached growth reactor, each attached growth reactor
including
a plurality of moving media for supporting biomass growth thereon, the first
attached
growth reactor having an inlet region for accepting wastewater and the second
attached growth reactor having an outlet region, said wastewater having a
direction of
flow through the attached growth reactor system from the first reactor to the
second
reactor,
CA 3034498 2019-02-21
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periodically removing moving media from the first attached growth reactor and
transferring said moving media to the second attached growth reactor.
As will be appreciated by one of skill in the art, moving media from the
second
reactor may be transferred to the first reactor or moving media may be added
to the
first attached growth reactor.
As will be appreciated by one of skill in the art, during processing of the
wastewater in an attached growth reactor including stationary fixed media, the
biomass that feeds on the wastewater grows on the attached media. In the warm
weather months, when nitrifying bacteria are most active, the fixed media
closest to
the inlet will have the greatest biomass. Periodically removing one of the
fixed media
closest to the inlet region of the attached growth reactor and moving it to a
position
more distal to the inlet region accomplishes two things: the now more distal
fixed
medium already has nitrifying bacteria biomass growing thereon which will now
become established further downstream of the inlet region and the fixed media
that
are now more proximal to the inlet region will grow nitrifying bacteria
thereon as a
result of exposure to more nitrogen as a result of being closer to the inlet.
It is to be
understood that "more distal" may also refer to movement to a chamber within
the
reactor or another reactor entirely that is downstream of the initial position
of the
media within the sewage treatment system.
Similarly, the moving media in the first reactor will comprise nitrifying
bacteria
biomass. Transferring this moving media to the second reactor transfers the
nitrifying
bacteria biomass to the second reactor. Replacing the moving media in the
first
reactor or first chamber of the reactor provides new surface area on which
nitrifying
bacteria biomass can be established. Thus, by removing the moving media from
the
first reactor at least once, the nitrifying bacteria biomass in the entire
reactor system
can be increased.
As will be apparent to one of skill in the art, moving one of the fixed media
downstream within the flow of the wastewater increases the nitrifying bacteria
biomass. As such, the process can be repeated multiple times during the warm
weather months, thereby significantly increasing the nitrifying bacteria
biomass within
CA 3034498 2019-02-21
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the attached growth reactor compared to an attached growth reactor in which
the
media are not moved.
The media may be moved after any suitable time period that is sufficient for
the
nitrifying bacteria biomass to grow to a sufficient extent, for example, after
a few days;
after a week; after a few weeks; after a month; and after a few months.
As will be apparent to one of skill in the art, other reactor systems having a
similar functionality to the SAGR or MBBR system can be considered to be the
same
as and/or functionally equivalent to the SAGR or MBBR system as used herein.
In some existing systems, a population of nitrifying bacteria is
created/maintained downstream of the inlet point in warm weather months so
that
there are at least two populations of nitrifying bacteria within the reactor
during cold
weather months.
In some such systems, while the volume of wastewater entering the reactor
remains constant, the location at which the wastewater is added to the reactor
changes.
As used herein, "constant volume" or "consistent volume" does not necessarily
mean "identical". The variation in levels of wastewater entering treatment
systems
over time are well understood by those knowledgeable in the art in general as
well as
specifically for individual treatment systems. As discussed herein, for
example,
predicted volumes and/or load can be determined based on for example predicted
usage patterns, as discussed herein. Rather, as used herein, "constant volume"
or
"consistent volume" in regards incoming wastewater to be treated in the
attached
growth reactor system takes into account these expected variations and refers
to "all"
of the wastewater being applied to the attached growth reactor system at a
given
time. That is, as discussed herein, a predicted or projected volume or load,
also
referred to as an approximately constant or consistent volume of wastewater or
wastewater load is expected or projected to be administered to the sewage
treatment
system. Similarly, the wastewater is expected to have similar or consistent or
constant
carbon and/or ammonia content or concentration over time. For example, it may
be
predicted to be approximately equivalent to what was generated previously or
may be
CA 3034498 2019-02-21
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based on projections of expected usage based on the size and nature of the
group or
population using the sewage treatment system.
In various embodiments of the present disclosure, the influent may be
transferred disproportionally to the members of the attached growth reactor
system.
.. That is, at any given point in time, one attached growth reactor or chamber
within an
attached growth reactor may receive a significant amount of the incoming
volume of
the influent. In embodiments wherein there are two attached growth reactors
within
the attached growth reactor system, the first reactor may receive greater than
50%,
greater than 60%, greater than 70%, greater than 80%, greater than 85%,
greater
.. than 90%, greater than 95%, substantially all or all of the influent while
the second
attached growth reactor receives less than 50%, less than 40%, less than 30%,
less
than 20%, less than 15%, less than 10%, less than 5%, substantially none or
none of
the influent for a first period of time. Subsequently, this is reversed, so
that the second
attached growth reactor receives a greater portion of the incoming wastewater
volume
.. for a second period of time. This process of alternating which attached
growth
reactor(s) receives more of the incoming wastewater volume is repeated
throughout
the warm weather months, as discussed herein.
Referring now to Figure 3, a reactor 200 is shown according to an embodiment
of the present disclosure. The reactor 200 can incorporate features of the
reactors 1,
2, and/or 100, and can implement the disproportionate wastewater flow
functions
described herein. In some embodiments, the reactor 200 includes a first
reactor 200A
and a second reactor 200B. In a first mode of operation, such as shown in
panel A of
Figure 3, for a first period of time, 100% of the constant volume of the
wastewater is
delivered or applied or transferred to the first reactor 200A and 0% of the
constant
volume is transferred to the second reactor 200B. After the first period of
time has
expired, 0% of the wastewater is transferred to reactor 200A while 100% is
transferred to reactor 200B for a second period of time, as shown in panel B
of Figure
3. In some embodiments, following expiration of the second period of time, the
process is repeated, that is, 100% of the wastewater is transferred to reactor
200A for
a first period of time and then 100% of the wastewater is transferred to the
second
CA 3034498 2019-02-21
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reactor 200B for a second period of time. This process may be repeated, that
is,
alternated, during warm weather. During cold weather, the wastewater is
distributed
approximately equally between the first reactor 200A and the second reactor
200B, as
shown in panel C of Figure 3. It is important to note that not only do the
respective
first period(s) of time and the second period(s) of time not have to be
identical, the
"first" first period of time and the "second" first period of time do not have
to be
identical either.
As such, these embodiments of the present disclosure enable the volume of
wastewater entering the reactor system to remain constant or consistent over
time,
while the volume of wastewater transferred to each reactor within the reactor
system
varies over time.
For attached growth reactor systems including more than 2 attached growth
reactors, for example, "n" attached growth reactors wherein "n" is an integer
of greater
than 2, for example, 3, 4, 5, 6, 7, 8, 9, 10 or more, a greater portion of the
incoming
wastewater volume is transferred to a respective one or more of the n attached
growth reactors for a period of time while the volume transferred to the
remaining
attached growth reactors is reduced accordingly. The respective one of the
attached
growth reactors receiving the additional volume of wastewater, for example,
120% of
"normal" volume, wherein the normal volume is the amount that that specific
attached
growth reactor would receive is the incoming volume was divided equally
amongst all
of the attached growth reactors.
As will be appreciated by one of skill in the art, the unequal distribution of
the
incoming wastewater volume increases the biomass in a given attached growth
reactor. While not wishing to be bound to a specific theory or hypothesis,
additional
biomass growth in each reactor is expected to be approximately proportional to
the
additional flow that each reactor receives.
For example:
If B is the quantity of biomass, expressed as a A of the biomass normally
occurring in the reactor;
N is the total number of reactors; and
CA 3034498 2019-02-21
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R is the number of reactors receiving loading during the bypass of the
remaining reactors, the total biomass is expected to be estimated by the
following
relationship:
B = 100% x N/R.
For example, 10 total reactors, with 4 reactors being bypassed and 6 receiving
wastewater would result in 100% x 10/6 = 166% of the biomass in each cell or
chamber compared to a situation in which all reactors remaining in service.
For a two reactor system, bypassing one cell would result in 100% x 2/1 =
200% of the biomass compared to both reactors remaining in service
continuously,
that is, both reactors receiving the same amount of wastewater.
Once the period of time that this "respective one" attached growth reactor
receives the increased volume has expired, a "respective second one" attached
growth reactor in the attached growth reactor system receives the increased
volume
and the previous "respective first one" attached growth reactor receives a
lower
.. volume as do the remaining attached growth reactor members of the attached
growth
reactor system for a second period of time. This process of alternating which
reactor
receives more influent or volume or intakes more wastewater may be repeated
over
time, as discussed herein.
As a result, the biomass in the respective second one attached growth reactor
begins to increase due to the increase in applied wastewater at the start of
the second
period of time. However, the nitrifying bacteria biomass in the respective
first one
attached growth reactor does not change significantly during the second period
of
time despite the reduction in applied wastewater, although it is hypothesized
that the
amount of heterotrophic bacteria in the respective first one attached growth
reactor
decreases as a result of the decreased volume of wastewater being transferred
during
the second period of time.
As such, by changing or alternating which attached growth reactor receives the
intervention, for example, the increased volume of incoming wastewater during
the
warm weather months, the biomass of nitrifying bacteria in each respective
attached
growth reactor is increased, as discussed herein. Other methods of increasing
CA 3034498 2019-02-21
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nitrifying bacteria biomass are disclosed herein and are within the scope of
the
present disclosure.
Thus, as discussed herein, during the warm weather periods of time (e.g.,
warm weather months), wastewater is distributed unequally between the two or
more
attached growth reactors or chambers within a single attached growth reactor
on an
alternating basis for the establishment of nitrifying bacteria biomass within
the
attached growth reactors. However, by temporarily distributing more wastewater
to
one reactor for a period of time and then alternating which reactor receives
more
wastewater, for example, substantially all or all of the incoming volume, the
nitrifying
bacteria biomass in each reactor is increased compared to applying a constant
volume of wastewater to each reactor, as discussed herein.
For example, in an attached growth reactor system including two attached
growth reactors wherein during warm weather months, all (or substantially all)
of the
incoming wastewater volume is transferred to one attached growth reactor for a
period of time, then all is transferred to the other attached growth reactor
for a period
of time. This alternating between which attached growth reactor receives a
significant
portion for example all of the wastewater may be repeated as often as
necessary
during the warm weather months based on the length of the period of time
selected.
As a result of this arrangement, the amount of nitrifying bacteria biomass
present in
each attached growth reactor will be approximately 200% of what it would have
been
had each attached growth reactor been transferred a "normal" volume of
incoming
wastewater, that is, approximately half of the incoming wastewater volume
continuously or constantly during the warm weather periods of time. The
nitrifying
bacteria are able to treat the incoming wastewater during the cold weather
months
despite the fact that cold weather reduces the efficiency of the nitrifying
bacteria
because of the increased biomass. Furthermore, for example, the first period
of time
and the second period of time may be identical but do not necessarily need to
be
identical or even similar. Furthermore, when alternating between reactors, the
"first"
first period of time and the "second" first period of time do not necessarily
need to be
CA 3034498 2019-02-21
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the same every time. That is, initially the first period of time may be for
example 1
month, then 2 weeks, then 6 weeks.
As will be appreciated by one of skill in the art, an attached growth reactor
system including two attached growth reactors, each one getting all or nothing
of the
.. incoming wastewater volume on an alternating basis during the warm weather
months
and half of the incoming wastewater volume during the cold weather months
represents the simplest situation and is accordingly used herein for
illustrative
purposes.
In other embodiments, encompassed within the scope of the present
.. disclosure, it may be that incoming volume is split 80/20 on an alternating
basis
between two attached growth reactors. This would result in an increase in
biomass of
180% in each reactor.
In some embodiments, the volume transferred to each attached growth reactor
during the cold weather months may be approximately proportional to the
percentage
of the total nitrifying bacteria biomass present in each attached growth
reactor or
proportional to or suitable for the nitrifying bacteria biomass in a given
reactor, as
discussed herein. That is, if the increased volume that is applied to each
individual
attached growth reactor is different, the amount of biomass in each reactor
will also
be different. In other words, the nitrifying bacteria biomass within a given
reactor or
reactor chamber may be estimated based either on the transfer of wastewater or
on
the capacity of a given reactor or reactor chamber to nitrify wastewater. This
capacity
may be measured using means known in the art, for example, by characterizing
the
ammonia content of wastewater influent entering the reactor and effluent
exiting the
reactor, or by the nitrite and nitrate produced within the reactor. As such,
the volume
.. transferred during the cold weather months may be adjusted accordingly for
optimum
functioning of the reactor system, although it is important to note that the
reactor
system will still be effective even if this is not done.
As will be apparent to one of skill in the art, the wastewater may be
distributed
to the attached growth reactors by a variety of means, as discussed herein. In
some
embodiments, wherein the attached growth reactor system comprises one attached
CA 3034498 2019-02-21
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growth reactor divided into two chambers, the chambers may be fed from the
center
out to the edges so that the inlets for each chamber are on either side of the
central or
common or shared distribution point. However, for simplicity, these two
chambers will
be referred to as a first attached growth reactor and a second attached growth
reactor
herein.
As will be apparent, there are those in the art who would consider multiple
attached growth reactors to be functionally equivalent to one attached growth
reactor
having a volume equal to the combined volumes of the multiple attached growth
reactors. These individuals would also conclude that one chamber of an
attached
growth reactor including multiple chambers or an attached growth reactor
system
including two or more attached growth reactors could be arbitrarily designated
as
being "upstream" within the attached growth reactor system while the other(s)
are
"downstream" within the attached growth reactor system.
For example, when the attached growth reactor is a SAGR, the SAGR system
is arranged such that either all of the wastewater can be distributed to
either SAGR or
portions of the influent can be distributed to each SAGR simultaneously. As
will be
apparent by one of skill in the art, this can be accomplished by a number of
means,
either by having two separate influent wastewater distribution systems for
each SAGR
or wherein the two SAGRs are effectively separate chambers of one SAGR with a
central influent distribution point, distribution could be controlled by
effluent valves in
either SAGR so that influent enters the SAGR chamber with the lowest hydraulic
gradient.
Alternatively, in embodiments wherein the attached growth reactor is an
MMAGR or a SMAGR arranged in an attached growth reactor system wherein there
are two or more physically separate attached growth reactors, for example, two
or
more MBBRs or fixed film reactors or a single MBBR or fixed film attached
growth
reactor separated into two or more chambers operated in parallel, split feed
can be
used to create larger nitrifying colonies in different reactors. Specifically,
the biomass
of nitrifying bacteria in the second reactor can be increased by fully or
partially
bypassing the first reactor for a period of time, as discussed herein. In some
CA 3034498 2019-02-21
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embodiments, as discussed herein, which reactor is bypassed is alternated
after a
period of time.
Other methods such as reducing aeration in the first reactor to generate
nitrifying bacteria in the second reactor, which would be fully aerated, would
have the
same effect as bypassing the first reactor entirely as all ammonia will pass
through
the unaerated zone with minimal reduction.
Thus, two or more MMAGR or SMAGR reactors can be operated in parallel.
By alternately feeding the parallel reactors for a period of time, additional
biomass is
grown in each, allowing the system to nitrify wastewater in the cold weather
periods of
time by again splitting the flow approximately equally between the parallel
cells. That
is, as discussed above, with N attached growth reactors, whether SAGR or MBBR
or
SMAGR reactors, in an attached growth reactor system connected in parallel,
any
intervention increasing nitrifying bacteria biomass, for example, transferring
n X y% of
the "normal" incoming wastewater volume to each one of the attached growth
reactors
for a period of time where "normal" would be the amount of volume transferred
if all
members of the system received a proportionate amount and y is greater than
100,
the biomass in each respective attached growth reactor will be increased by
y%. As
will be appreciated by one of skill in the art, this represents one method for
estimating
nitrifying bacteria biomass volume or quantity.
In an alternative embodiment, there is provided an attached growth reactor
system that has a first end region and a second end region, each end region
having
an access port. As will be appreciated by one of skill in the art, as a result
of this
arrangement, the flow can effectively be reversed in the attached growth
reactor
periodically. As a result of this arrangement, two populations of nitrifying
bacteria can
be formed, each proximal to one end region of the attached growth reactor
system.
According to an aspect of the present disclosure, there is provided a method
for increasing nitrifying bacteria biomass in an attached growth reactor
including:
providing an attached growth reactor system having a first end region and a
second end region wherein the first end region and the second end region are
both
capable of acting as an inlet or an outlet;
CA 3034498 2019-02-21
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during a warm weather period of time, transferring a volume of wastewater into
the attached growth reactor system at the first end region and removing
treated
wastewater from the attached growth reactor system at the second end region
for a
first period of the warm weather period,
then transferring the volume of wastewater into the attached growth reactor
system via the second end region and removing treated wastewater from the
attached
growth reactor system at the first end region for a second period of the warm
weather
period on an alternating basis.
As will be apparent to one of skill in the art, the nitrifying bacteria
biomass
present in the attached growth reactor has been effectively doubled as a
result of
alternating the direction of flow through the reactor.
The direction of flow can be changed after any suitable period, for example,
after a period of time selected from the group consisting of: a few hours; a
day; a few
days; a week; a few weeks; a month; and a few months.
The attached growth reactor system may be a single attached growth reactor
wherein either end of the single reactor can act as inlet or outlet, or the
attached
growth reactor system may be at least two attached growth reactors, wherein a
first
attached growth reactor is the first end of the system and the second attached
growth
reactor is the second end of the system.
In the embodiments discussed herein, in warm weather periods of time, a
significant portion or substantially all of the influent is transferred to the
first attached
growth reactor, for example, a SAGR, an MMAGR or a SMAGR, for a period of time
to increase the biomass, for example, the nitrifying bacteria biomass, in the
specific
attached growth reactor. Following this period of time, which must be long
enough for
the nitrifying bacteria biomass to increase and may be for example half an
hour, an
hour, a few hours, half a day, a day, a few days, a week, a few weeks, a month
or
even a few months, a significant portion or substantially all of the
wastewater is
transferred to the second attached growth reactor so as to support bacterial
growth
and maintain the bacteria population within the second attached growth
reactor.
CA 3034498 2019-02-21
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As will be appreciated by one of skill in the art, wastewater volumes applied
to
the attached growth reactor system stay approximately constant throughout the
year.
However, the ability of the bacteria population to break down the influent as
discussed
herein is reduced during the cold weather months.
Consequently, in the cold weather periods of time, when water temperature
may decrease towards or be lower than 4 degrees Celsius, the incoming
wastewater
is divided such that a portion thereof, for example, approximately half, is
transferred to
the first attached growth reactor and the remainder is transferred to the
second
attached growth reactor.
That is, during the warm weather periods of time, which reactor receives an
increased proportion or substantially all of the incoming volume is alternated
so that
the nitrifying bacteria biomass in each reactor is proportionally increased;
however,
during the cold weather months, each reactor receives an approximately
constant
proportion of the incoming volume which is effectively nitrified by the
increased
nitrifying bacteria biomass in each reactor.
Alternatively, as discussed herein, the division of the incoming volume or
incoming flow or flow may be based on the relative amount of biomass in each
attached growth reactor in the attached growth reactor system, calculated or
estimated or approximated as discussed herein.
Specifically, by distributing the wastewater unequally to two (or more)
attached
growth reactors throughout the warm weather months, and alternating which
attached
growth reactor received more (or all) of the incoming volume over time, the
biomass
for example the biomass of nitrifying bacteria in each reactor is increased
proportionally to the increase in flow. Consequently, in the cold weather
months, when
the efficiency of bacterial degradation of the influent is decreased, there is
increased
biomass of nitrifying bacteria to treat the influent.
According to another aspect of the present disclosure, there is provided a
method of improving ammonia removal from waste water during cold weather
months
including:
in a sewage treatment system including at least two attached growth reactors,
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each respective attached growth reactor having an inlet distribution point in
the
attached growth reactor for receiving an influent of wastewater,
transferring an approximately constant volume of the wastewater to the two
attached growth reactors, wherein the volume is transferred such that a first
attached
growth reactor receives a larger portion of the volume than a second attached
growth
reactor for a first period of time and the second attached growth reactor
receives a
larger portion of the volume than the first attached growth reactor for a
second period
of time during a warm weather period; and
transferring the volume of wastewater to the first attached growth reactor and
the second attached growth reactor approximately equally during a cold weather
period.
According to another aspect of the present disclosure, there is provided a
method of increasing nitrifying bacteria biomass in an attached growth reactor
system
during a warm weather period including:
in a sewage treatment system including at least two attached growth reactors,
each respective attached growth reactor receiving an influent of wastewater,
transferring a volume of the wastewater to the two attached growth reactors,
wherein the volume is transferred such that a first attached growth reactor
receives a
larger portion of the volume than a second attached growth reactor for a first
period of
time of the warm weather period and the second attached growth reactor
receives a
larger portion of the volume than the first attached growth reactor for a
second period
of time of the warm weather period on an alternating basis.
As discussed herein, "alternating basis" refers to the fact that once the
second
period of time has expired, the first attached growth reactor receives the
larger portion
of the volume for a "new" first period of time.
It is further noted as used herein that the biomass of the nitrifying bacteria
in
the attached growth reactor system is increased compared to the nitrifying
biomass
present in a control attached growth reactor system, that is, a growth reactor
system
of similar size, fed a similar type of wastewater. That is, the control for
comparison
purposes would lack the modification(s) or alteration(s) made to the attached
growth
CA 3034498 2019-02-21
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reactor system to increase the biomass as described herein, for example,
alternating
flow volumes between reactors, applying nitrogen, applying heat as well as
other
methods discussed herein.
According to another aspect of the present disclosure, there is provided a
method for improving ammonia removal from wastewater during a cold weather
period including:
in a sewage treatment system including an attached growth reactor separated
into at least a first attached growth reactor chamber and a second attached
growth
reactor chamber,
during a warm weather period, transferring a significant portion of wastewater
to the first attached growth reactor chamber for a first period of time, then
transferring
a significant portion of the wastewater to the second attached growth reactor
chamber
for a second period of time; and
during a cold weather period, transferring approximately half of the
wastewater
to the first attached growth reactor chamber and approximately half of the
wastewater
to the second attached growth reactor chamber.
In some embodiments, during the warm weather period, substantially all of the
wastewater is transferred to the first attached growth reactor for a first
period of time
and subsequently all of the wastewater is transferred to the second attached
growth
reactor for a second period of time.
It is known in the art that the discharge of elevated levels of ammonia during
winter months from a sewage treatment lagoon is due to the temperature
effects.
The inventors realized that increasing the biomass of nitrifying bacteria
within
the attached growth reactor system during the warm weather periods by
alternating
which attached growth reactor receives an increased volume of incoming
wastewater
and/or increased carbon and/or ammonia content, regardless of whether the
attached
growth reactor is a SAGR, an MMAGR, a SMAGR or other similar reactor, provides
higher levels of nitrifying bacteria biomass within the attached growth
reactor system
than maintaining a constant distribution to each respective attached growth
reactor.
The end result is that the nitrifying bacteria biomass is then better able to
nitrify the
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incoming influent volume in the winter months because the greater biomass
compensates for the reduction in activity and/or efficiency caused by the cold
weather.
The attached growth reactors are supplied wastewater from a treatment lagoon
or other similar secondary treatment system. In general, such a lagoon is
considered
likely to produce wastewater that has low amounts of CBOD in the summer months
and high levels of CBOD in the winter months and high levels of ammonia in the
winter, low levels of ammonia in the summer. However, as will be known to
those of
skill in the art, this can vary considerably depending on the nature of the
wastewater
entering the lagoon as well as other environmental factors such as weather
conditions
and environmental conditions.
In winter or cold weather, when the cold water temperatures cause the
nitrifying microbes to slow-down, the increased biomass allows for the removal
of the
full amount of ammonia. This is important, because the populations do not
respond
quickly at very low temperatures, taking a long time to grow a larger
bacterial
population if there are not enough bacteria for current conditions, which may
not be a
sufficient response time depending on regulatory permit requirements.
Systems and methods in accordance with present disclosure can facilitate the
unequal distribution of the incoming wastewater volume to each attached growth
reactor (e.g., staggered supply), which increases the nitrifying bacteria
biomass in
each reactor compared to a constant distribution of proportional amounts of
incoming
wastewater volume to each attached growth reactor in the attached growth
reactor
system. As a result of this arrangement, the reactors contain many more
nitrifying
microbes than could be grown in a single-feed system. As a consequence, the
associated microbial community is capable of doing full treatment even as
biological
kinetics slow down due to temperature effects.
It is of note that there are other methods for creating one or more additional
zones and/or increasing the biomass of nitrifying bacteria within a reactor or
reactor
system so that there is sufficient nitrifying bacteria population for waste
water
CA 3034498 2019-02-21
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nitrification during winter months, many of which are discussed herein and
which are
within the scope of the present disclosure.
In other embodiments, nitrifying bacteria biomass may be increased by altering
the environment in a specific zone of an attached growth reactor within an
attached
.. growth reactor system. For example, the relative heat, oxygen level and/or
ammonia
level in a specific zone may be increased as a means for increasing either the
activity
or the biomass of the nitrifying bacteria, as discussed in greater detail
above.
For example, heating means may be employed to elevate the temperature of at
least a portion of the waste in the reactor during winter months. For example,
the
heating means may be arranged such that a region of the reactor expected to
contain
the nitrification zone is heated, then alternating which zone is heated so
that a
different region of the reactor is heated, thereby growing nitrifying bacteria
biomass in
a different region of the reactor.
As will be appreciated by one of skill in the art, there are many means for
locally increasing the temperature of a liquid.
Alternatively, oxygen may be supplied to one or more discrete zones of the
reactor so as to promote nitrification within those zones. In this case oxygen
may be
limited in portions of the reactor to grow a larger population of nitrifying
bacteria only
in the oxygenated portion. For example, supplying heated air or oxygen during
cold
weather months will increase the local water temperature surrounding the
nitrifying
bacteria, thereby increasing their activity.
In other embodiments, the waste in the reactor may be supplemented with an
alternate source of ammonia at discrete locations within the reactor to
support
nitrifying bacteria growth, thereby increasing the biomass of nitrifying
bacteria. In both
instances, the location of heating or ammonia supplementation may be varied
over
time, thereby establishing multiple colonies or "locations" of nitrifying
bacteria.
As can be seen, the processes described herein either increase the activity of
the nitrifying bacteria in cold weather months or increase the biomass of the
nitrifying
bacteria within the attached growth reactor system so that more nitrifying
bacteria are
available for nitrification. The biomass can be increased by supplying
wastewater
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containing nitrogen or simply nitrogen to a different location within the
attached growth
reactor system than the original wastewater inlet or by temporarily increasing
the
amount of nitrogen applied to an inlet, either by temporarily increasing the
incoming
flow of wastewater to a specific attached growth reactor or by increasing the
amount
of nitrogen present in the wastewater temporarily by supplementing the
wastewater
with nitrogen.
As will be appreciated by one of skill in the art, methods such as those
described above may be used within a single reactor or reactor system or
multiple
reactor system, such as those discussed herein.
Influent into the SAGR is typically an effluent from a standard municipal
treatment lagoon, having estimated concentrations of CBOD5 20-40 mg/I; total
suspended solids (TSS) 20-40 mg/I; and ammonia of approximately 25-45 mg/I.
However the SAGR is not limited to treating effluent from a lagoon process.
The
process is applicable to any other nitrification applications where low water
temperature conditions are present.
The length of the SAGR is typically 40-75 ft long with a depth of between 4-12
ft. The width of the SAGR will vary as a function of flow. For example, more
flow
from a larger population base will result in a wider system. Retention time of
the
wastewater in the SAGR is a function of wastewater concentration, but is
typically in
the range of 4-6 days, but will vary according to the mass load applied to the
SAGR).
Influent into the lagoon will typically be raw municipal wastewater, CBOD 150-
250 mg/I; TSS 20-40 mg/I; total Kjeldahl Nitrogen (TKN) 25-45 mg/I; ammonia 20-
40
mg/I; and total phosphorus 6-8mg/I.
A treatment lagoon will typically have a depth between 5 and 20 ft and will
typically have somewhere between 20 and 45 days of retention time for the
wastewater. The volume of the lagoons depends on the population base feeding
the
lagoon.
It is important to note that the above stated dimensions for the lagoon and
the
reactor and the characteristics of the influents are intended for illustrative
purpose
only.
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CBOD removal is typically measured at 20 degrees Celsius, and factored down
using a first order equation, resulting in a removal rate at 0.5 degrees
Celsius that is
approximately half of the rate at 20 degrees Celsius. However, a lagoon may
still
remove a significant amount of CBOD at these low temperatures, because it may
have had more retention time available than was required at the warm
temperatures.
(All water temperatures). It is of note that 0.5 degrees Celsius is generally
accepted
as the minimum temperature for a treatment system because at lower
temperatures,
ice will form.
The scope of the claims should not be limited by the preferred embodiments
set forth in the examples but should be given the broadest interpretation
consistent
with the description as a whole.
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