Note: Descriptions are shown in the official language in which they were submitted.
RUSS 1O-ICA
Fail Safe Flushing BioReactor for Selenium Water Treatment
Technical Field
[0001] This document is related to the treatment of water.
Background
[0002] Bioreactors are used to process water and other liquids. In many
cases,
bioreactors may be used to remove unwanted or harmful compounds from water.
One such
system may remove selenium from water, such as effluent from mining or other
operations.
[0003] Many industrial activities involve processes that produce an
effluent containing
contaminants, which at elevated levels are toxic or otherwise detrimental to
human health,
fish and wildlife. Some anthropogenic sources of contaminated effluent include
mining, coal
fired power plants, agricultural drainage, oil refining, and natural gas
extraction. Effluent
contaminants may include soluble metalloids, soluble metals, soluble metal
complexes,
perchlorate, methyl mercury, arsenic, nitrates, and nitrites.
[0004] For example, selenium is a naturally occurring metalloid, which can
be released
through anthropogenic activities such as mining and the combustion of coal.
Dissolved
forms of selenium, selenate and selenite, have been known to bio-accumulate in
birds and
fish, causing mutations and death. Selenium in small amounts is an essential
nutrient for fish
and other wildlife, but at high levels, may be toxic.
[0005] Excessive levels of nitrate in drinking water may have a negative
impact on the
health of human infants and animals. Nitrate poisoning may affect infants by
reducing the
oxygen carrying capacity of the blood. The resulting oxygen starvation can be
fatal. Once a
water source is contaminated, the costs of protecting consumers from nitrate
exposure can be
significant.
[0006] Perchlorate, in large amounts, may interfere with iodine uptake into
the
thyroid gland. In adults, the thyroid gland helps regulate the metabolism by
releasing
hormones, while in children the thyroid helps in proper development.
CA 2969589 2017-06-05
RUSSIO-ICA
2
[0007] Mercury may negatively affect the immune system, alter genetic and
enzyme
systems, damage the nervous system, and impair coordination and the senses of
touch, taste,
and sight. Indeed, fish consumption advisories for methylmercury now account
for more
than three quarters of all fish consumption advisories in the United States.
[0008] Arsenic may also be toxic to animals, including humans, and is a
known carcinogen
associated with both skin and lung cancers. Contamination of potable water
supplies with arsenic
is of particular concern.
[0009] The United States Environmental Protection Agency (EPA) commonly
regulates and
provides guidelines regarding contaminant levels that may or may not be
acceptable for
discharging effluent and water for release into potable water supplies.
Complying with EPA
requirements and guidelines can be difficult and expensive. Moreover, in the
future the EPA may
tighten or increase regulations governing contaminants in water for discharge
or release into
potable water supplies.
100101 In the past, various methods have been employed for removing certain
contaminants
from industrial effluent. Three conventional methods that have been used
include iron co-
precipitation, activated alumina treatment, and biological treatment.
Biological treatment of
industrial effluent has emerged as one of the more popular means of removing
these
contaminants,
[0011] Biological treatment of contaminated water is commonly conducted
using a
bioreactor system. Bioreactors used in industrial effluent treatment may
include suspended growth
bioreactors, fixed bed reactors, and fluidized bed reactors. A fixed bed
reactor may also be
referred to as a packed bed bioreactor. A fluidized bed reactor may also be
referred to as an FBR.
[0012] A bioreactor may be used to reduce a soluble contaminant to an
elemental precipitate
or to a gas form that is more easily removed from the water. Reduction of
soluble contaminants
may be accomplished by bacterial reduction.
[0013] For example, bacteria colonies cultured in bioreactors may be used
to convert
contaminants such as nitrates into gas, which may be more easily removed from
the system than
CA 2969589 2017-06-05
RUSS 10- I CA
3
the oxidized form. Heterotrophic bacteria may utilize the nitrate as an oxygen
source under anoxic
conditions to break down organic substances resulting in nitrogen gas as one
of the end products.
Perchlorate may also be converted to the chloride ion (Cl-) and arsenic
converted to As(III) using
bacterial reduction by way of a bioreactor.
[0014] Thus, bioreactors may provide an environment in which to grow and
maintain
bacterial cultures cultivated for reduction of a contaminant. The bioreactors
may include an
insoluble support or growth media to provide a surface area on which bacteria
may colonize and
form biofilm. The insoluble support or growth media may comprise granular
activated carbon
(GAC), sand, or similar insoluble media conducive to growth, development, and
adherence of a
bacteria colony and biofilm. Both fixed bed reactors and fluidized bed
reactors may use granular
activated carbon (GAC), sand, or similar insoluble media for maintenance of
biofilms.
[0015] A biofilm (sometimes referred to as a bacteria biofilm or active
biofilm) is a complex
biological structure comprised of colonies of bacteria and other
microorganisms, such as yeast
and fungi. Water and other liquids passing through a bioreactor may be
maintained in regular
contact with the biofilm when the bacteria colony and biofilm are disposed on
an insoluble
support or growth media.
[0016] Thus, soluble contaminants may be precipitated or converted to a gas
form using a
bacterial reduction process by passing water through a bioreactor where
contaminants in the water
come into contact with a biofilm specifically cultivated for reduction of a
contaminant.
Conventional bioreactor systems have typically been configured to permit flow
of contaminated
water through the system so that contaminants come into contact with the
biofilm.
[0017] For example, bioreactors for removing soluble selenium from effluent
may comprise
specially cultivated bacteria colonies disposed within GAC, sand, or a
combination thereof, where
the bacterial colonies form a biofilm. Bacteria are fed carbohydrate rich
nutrients, which are
directly supplied to the bioreactor to stimulate bacterial respiration and
biofilm growth.
[0018] Soluble selenium, typically an oxidized form of selenium such as
Se042-
(selenate) and Se032- (selenite) may be transformed to particulate elemental
selenium using
reduction by selenate or selenite bacterial respiration. Particulate elemental
selenium may
CA 2969589 2017-06-05
RUSS I 0-1CA
4
also be referred to as filterable selenium, colloidal selenium, fine elemental
selenium
particles, reduced elemental selenium particles, elemental selenium
precipitate, or precipitate
where the precipitate is a substance in solid form that separates from
solution.
[0019] Reduction of selenate or selenite to elemental selenium particles
occurs as water
contaminated with selenate or selenite passes across the biofilm and the
selenate or selenite is
used in bacterial respiration. Selenate and selenite are very small particles
typically less than 1 uM
in size. When precipitated into elemental selenium particles, larger
precipitated particles may be
retained within the bioreactor while the water continues to pass through and
out of the bioreactor
system.
[0020] Similarly, bioreactors may be used to cultivate bacteria colonies
disposed in GAC,
sand, or some other insoluble growth media and convert contaminants, such as
nitrates, to gas. As
nitrate contaminated water passes through the bioreactor and comes into
contact with the biofilm,
the bacteria colony may use the nitrate as an oxygen source under anoxic
conditions to break
down organic substances and convert the nitrate into nitrogen gas in the
process. Thus, nitrate
may be converted to nitrogen gas by bacterial reduction. Perchlorate may also
be converted to the
chloride ion (Cl-) and arsenic converted to As(III) in a bioreactor using
bacterial reduction.
[0021] However, there are some disadvantages to bioreactor systems
currently available for
remediating industrial effluent. For example, bioreactor systems are directly
fed a carbohydrate
nutrient to stimulate bacteria growth and respiration; and, the large amounts
of carbohydrate
nutrient may not be completely consumed. Unconsumed carbohydrate nutrient may
reduce
effluent quality. Consumption of carbohydrate nutrient may also result in
increased carbonaceous
(organic) compounds or particulate matter in the effluent, reducing water
quality. The
measurement of water quality based on carbonaceous compounds/organic matter in
the water may
be measured by determining the Chemical Oxygen Demand (COD) or the Biological
Oxygen
Demand (BOD). (ROD and COD are also sometimes used to refer to the
carbonaceous
compounds/organic matter in the water.)
[0022] Furthermore, conventional bioreactor systems do not effectively
retain precipitates
such as fine selenium particulates, thus reducing quality of effluent exiting
the system.
CA 2969589 2017-06-05
RUSSIO-ICA
[0023] Also, specific combinations of contaminants are of interest to
certain industries. For
example, recently proposed effluent guidelines for the steam electric power
industry limit
discharge of nitrate, selenium, mercury and arsenic. However, conventional
bioreactors may not
contemporaneously remove multiple species of contaminants effectively,
particularly where
bacterial reduction of different contaminant species may produce different end
product forms
(e.g., precipitate versus a gas).
[0024] There are also other disadvantages to conventional bioreactor
systems. Fixed bed
reactors tend to be large in size due to low hydraulic loading requirements
necessary for solids
retention. Biological reactions within the bed produce gases such as nitrogen,
carbon dioxide, and
hydrogen sulfide through cellular respiration and fermentation reactions. Gas
can build up in the
bed, decreasing bed permeability and creating head-loss, impeding water flow
through the bed.
[0025] Some fixed bed reactors currently being used in the industry attempt
to address
decreased bed permeability by increasing the liquid level above the bioreactor
bed, thus
increasing the driving hydraulic head needed to push liquid through the
bioreactor bed. The
driving hydraulic head (sometimes referred to as static head) may be increased
by increasing the
column of water above the bioreactor bed. The maximum amount of static head
available may be
limited by the tanks height and available freeboard above the bioreactor bed.
[0026] Freeboard is the extra space needed above the reactor bed to meet
the hydraulic head
requirement for effectively pushing water through the bed. The bioreactor
tanks must be tall
enough so the driving head is sufficient to overcome gas entrained in the bed,
which may prohibit
permeation. Freeboard may account for as much thirty percent (30%) or more of
additional tank
height above what is required for the bioreactor bed.
[0027] The increased height and large volume of fixed bed reactors
generally makes them
more expensive, harder to transport, and if housed in a building, may require
more building
height. Moreover, because of their large size, fixed bed reactors typically
have to be constructed
onsite, which increases construction costs.
[0028] Attempts have also been made to reduce problems associated with gas
impediment
using fluidized bed reactors. In a fluidized bed reactor, water is passed
through a granular solid
CA 2969589 2017-06-05
RUSSIO-ICA
6
material at high enough velocities to suspend the granular material so it
behaves as though it were
a fluid. This process, known as fluidization, assists in the release of gas.
[0029] However, a fluidized bed has some disadvantages because of the
fluidization and
extreme agitation in the system. For example, a fluidized bed reactor does not
effectively remove
particulate matter such as colloidal selenium and mercury species. Moreover,
there is a resulting
increase in organic materials in the effluent. Consequently, fluidized bed
reactors require
recycling the effluent through the bioreactor using multiple passes in order
to remove contaminant
particulates.
[0030] Thus, it is desirable to have an improved biological system and
method for the
treatment of water that improves the quality of the effluent exiting the
system, more effectively
retains particulate elemental contaminants, improves permeability of a
bioreactor bed and
associated water flow, reduces problems associated with entrained gases,
effectively reduces
COD/BOD in the effluent, provides for concurrent removal of various
contaminant species,
reduces freeboard above a bioreactor bed, and allows for a smaller overall
system footprint.
CA 2969589 2017-06-05
7
Summary
[0031] A biological reactor system treats concentrated contaminated water
with a combination
of upflow and downflow bioreactors that are downstream from a reverse osmosis
or other concentrator.
The system may have a fail-safe configuration where flush water may be
introduced to the reactors in
the event of a power failure or when taking the reactors offline. Many reverse
osmosis systems
introduce antiscalant treatments upstream so that the reverse osmosis filters
do not scale. However,
such treatments result in superconcentrated conditions of the antiscalants in
the contaminated water
processed by the bioreactors. A flushing system may deconcentrate the
bioreactors to prevent the
antiscalants from precipitating and fouling the bioreactors.
[0031a] In a further aspect it is provided a system for treating reverse
osmosis effluents, said
system comprising: a first bioreactor having a first bioreactor inlet and a
first bioreactor outlet, said
first bioreactor being an upflow bioreactor and containing a first media bed;
a second bioreactor having
a second bioreactor inlet and a second bioreactor outlet, said second
bioreactor inlet connected to said
first bioreactor outlet by an overflow weir, said second bioreactor being a
downflow bioreactor and
containing a second media bed; a flush water tank connected to said second
bioreactor outlet, at least
a portion of said flush water tank being located above said second bioreactor;
a first valve system
connected to said first bioreactor inlet, said first val ve system configured
to drain said first bioreactor
during a deconcentrator sequence; and a second valve system connected between
said second
bioreactor outlet and said flush water tank, said second valve system being
configured to drain at least
a portion of said flush water tank into said second bioreactor such that said
second bioreactor overflows
into said first bioreactor during said deconcentrator sequence, said overflow
weir being configured to
permit overflow from said first bioreactor to said second bioreactor when said
first bioreactor operates
in an upflow mode, said overflow weir being further configured to permit
overflow from said second
bioreactor to said first bioreactor when said second bioreactor operates in
said deconcentrator
sequence; and wherein the first valve system and the second valve system are
configured in a normally-
open position to automatically initiate the deconcentrator sequence when power
is lost.
[0032] This Summary is provided to introduce a selection of concepts in a
simplified form that
are further described below in the Detailed Description. This Summary is not
intended to identify key
features or essential features of the claimed subject matter, nor is it
intended to be used to limit the
scope of the claimed subject matter.
Date Recue/Date Received 2022-02-24
RUSS 1 0- ICA
8
Brief Description of the Drawings
[0033] In the drawings,
[0034] FIGURE 1 is a diagram illustration of an embodiment showing a
multistage water
treatment system.
[0035] FIGURE 2 is a diagram illustration of an embodiment showing a
anaerobic
bioreactor.
[0036] FIGURE 3 is a flowchart diagram of an embodiment showing a method
for treating
water with dissolve selenium.
[0037] FIGURE 4 is a diagram illustration of an embodiment showing a
multistage water
treatment system with filtration.
[0038] FIGURE 5 is a diagram illustration of an embodiment showing an
upflow bioreactor.
[0039] FIGURE 6 is a diagram illustration of an embodiment showing a two-
stage water
treatment system.
[0040] FIGURE 7 is a diagram illustration of an embodiment showing a
multistage water
treatment system.
[0041] FIGURE 8 is a diagram illustration of an embodiment showing a
downflow
bioreactor.
[0042] FIGURE 9 is a diagram illustration of an embodiment showing a graph
of vacuum
pressure verses time for the output pump of a downflow bioreactor.
[0043] FIGURE 10 is a diagram illustration of an embodiment showing a
downflow
bioreactor.
[0044] FIGURE 11 is a diagram illustration of an embodiment showing a
multistage water
treatment system with a reverse osmosis concentrator.
[0045] FIGURE I2A is a diagram illustration of an embodiment showing a set
of upflow and
downflow bioreactors during normal operation.
CA 2969589 2017-06-05
RUSSIO-ICA
9
[0046] FIGURE 12B is a diagram illustration of an embodiment showing a set
of upflow and
downflow bioreactors during a flush operation.
[0047] FIGURE 12C is a diagram illustration of an embodiment showing a set
of upflow and
downflow bioreactors during a deconcentrator operation.
[0048] FIGURE 13 is a flowchart illustration of an embodiment showing a
method for
operating bioreactors.
[0049] FIGURE 14 is a flowchart illustration of an embodiment showing a
method for a
backwash sequence in bioreactors.
CA 2969589 2017-06-05
RUSSIO-ICA
Detailed Description
[0050] Fail Safe Flushing BioReactor
[0051] A biological reactor system with a combination of upflow and
downflow reactors has
a fail-safe configuration where flush water may be introduced to the reactors
in the event of a
power failure or otherwise when taking the bioreactors offline. The flush
water may be gravity fed
into the reactors and may dilute the reactors to the point where media and
biological agents to not
solidify and make restarting the bioreactor difficult. During normal
operation, the reactors may
process incoming water, which may keep the systems in balance, as the
biological agents may
consume material in the incoming stream and may release gasses as well as
solids that may be
suspended or dissolved in the effluent.
[0052] When the incoming water stream may be halted, such as in a power
failure or when
taking the bioreactor offline, antiscalants added to protect a reverse osmosis
filter may be present
in superconcentrated conditions. A flushing reservoir may be configured to
open and backflush
the reactors to deconcentrate the bioreactors to prevent unwanted
precipitation of the antiscalants.
[0053] A biological reactor system for treating water may contain media on
which biological
agents may attach. The biological agents may be bacterium, algae, fungus, or
other agents, and the
media may be any mechanical media such as carbon.
[0054] During normal operation, the biological reactor system may use
upflow or downflow
reactors to treat water. Some systems may use a combination of reactors in
series, such as an
upflow reactor followed by a downflow reactor, or vice versa. In an upflow
reactor, water may be
introduced into the bottom of the reactor and may flow upward to a weir or
other mechanism to
receive the reactor effluent. In a downflow reactor, water may be introduced
to the top of the
reactor and may flow downward to an exit port.
[0055] Biological reactors may often operate with a periodic cleaning
cycle, where water
may be introduced into the reactor in a way that may clean the reactor by
removing excess
biological material, entrained gasses, dissolved or precipitated solids, or
other matter from the
CA 2969589 2017-06-05
RUSSIO-1CA
11
reactor. Such a cleaning cycle may produce waste water that may be collected
separately and
further processed.
[0056] Several different types of cleaning cycles may be used. One type of
cleaning cycle
may be to flush a reactor with a large volume of water. Such a reactor may
operate with a
relatively low water flow rate, and in many cases the flow rate may be set to
be a plug flow or
laminar flow. Such a flow rate may allow the biological agents and their media
to react with the
water for a desired period of time. During a flush cycle, a much higher flow
rate may be
introduced. The high flow rate of the flush cycle may cause turbulent flow
within the reactor, and
may cause the media and biological agents to rub on each other, thereby
mechanically separating
or cleaning the media from excess biological material. The high flow rate may
cause entrained
gasses to be expelled, and in some cases, the high flow rate may capture and
remove precipitates
or other solid material from the reactor.
[0057] Some flushing cycles may be reverse flow flushing cycles. For
example, a downflow
reactor may have flushing water introduced into the bottom of the reactor,
such as through what
would be the normal output of the reactor. Such a reverse flow may loosen any
media,
precipitated solids, or other material in the reactor.
[0058] In the case of a downflow reactor, a flush cycle may be a reverse
flow flushing cycle.
In the case of an upflow reactor, a flush cycle may be a forward flow flushing
cycle.
[0059] The net effect of a flushing or cleaning cycle may be to remove
excess biological
agents, as well as precipitates, entrained gasses, and other dissolved
materials. During normal
operation, a cleaning cycle may be performed as the reactor's effectiveness or
efficiency changes.
A reactor's efficiency or effectiveness may change as precipitates build up,
as the biological
agents grow, age, or die, or as media breaks down, nutrients are consumed and
replenished, or
other factors occur.
[0060] In some cases, a flushing cycle may introduce nutrients, new
biological agents, or
other items, such as conditioning agents such as anti-foaming agents, foam-
enhancement agents,
surfactants, solvents, or other agents that may clean, fortify, or otherwise
prepare the reactor for
further use.
CA 2969589 2017-06-05
RUSSIO-1CA
12
[0061] A flushing cycle may be automatically performed when power may be
cut to the
system. The flushing cycle may dilute or otherwise perform some amount of
cleaning of a reactor.
The flushing cycle may reduce biological activity to the point where
components in the reactor do
not congeal, solidify, or otherwise make the reactor hard to restart.
[0062] The emergency flushing cycle may leave much of the biological
agents, their
nutrients, media, and other components in the reactor, but may lower the
activity within the
reactor. The reduction of activity may allow for service technicians to get
the system back on line
before the reactor may become unusable due to the solidification of the
material in the reactor.
[0063] One use of a flushing cycle may be in the processing of reverse
osmosis waste
stream. The waste stream may be a concentrate, which may be further processed
in a bioreactor or
series of bioreactors. Such concentrate may have a high amount of salts and
other contaminants,
and in many cases, such contaminates may be supersaturated in the presence of
anti-scaling
agents. A flushing cycle may deconcentrate the material in the bioreactors,
thereby eliminating the
possibility of scaling within the bioreactors.
[0064] Two-Stage Water Treatment Systems
[0065] Figure 1 is a diagram illustration of an embodiment 100 of a
biologically active,
multi-stage water treatment system. The system may be used to remove soluble
selenium from
contaminated water using reduction occurring during a first bioreactor where
anoxic bacterial
respiration reduces selenium and other water contaminants from a soluble form
to a precipitate
form. As a precipitate, the contaminants may be more easily removed from the
water. A
subsequent bioreactor stage operating under anaerobic, aerobic, or partially
aerobic conditions
may remove residual nutrients, which may permit subsequent membrane filtration
and membrane
concentration stages without membrane fouling.
[0066] The water treatment system 100 may receive contaminated water from a
contaminated effluent from a feed water source 110. The feed water may be
contaminated with
soluble (oxidized) forms of selenium such as selenate or selenite, which may
be toxic to fish and
other wildlife. The feed water source 110 may be a river, pond, lake, or other
contaminated water
source. The feed water source 110 may include a contaminated water output of
an industrial plant
CA 2969589 2017-06-05
RUSSIO-1CA
13
or process. The feed water source may also be a conduit, a holding tank, or a
reservoir receiving
contaminated water from industrial processes, such as mine runoff, coal-fired
power plant
effluents, a groundwater seep, well, agricultural drainage or other
anthropogenic sources.
[0067] The water treatment system 100 may comprise an anaerobic bioreactor
120 at a first
stage, an aerator 130 at a second stage, and one or more aerobic bioreactors
140 at a third stage
for polishing. Bioreactors 120 and 140 may be configured to be biologically
active. The anaerobic
bioreactor 120 shown in Figure 1 may be a fluidized bed reactor ("FBR").
[0068] The multi-stage water treatment system 100 may also include a
membrane filtration
system 150 at a fourth stage for removal of residual precipitated selenium.
The membrane
filtration system 150 may remove, concentrate, and recover any remaining
particulates that may
be measured as Total Suspended Solids. The membrane filtration system 150 may
comprise an
ultrafiltration system or a microfiltration system.
[0069] The multi-stage water treatment system 100 may also include a
membrane
concentration system 160 at a fifth stage for removal of any residual
dissolved selenium. The
membrane concentration system may comprise a reverse-osmosis system or a nano-
filtration
system. Dissolved selenium removed by the membrane concentration system may be
delivered to
the feed water pathway between the feed water source 110 and the anaerobic
bioreactor 120 for
introduction back into the water treatment system 100 for further processing.
[0070] A solids handling system 190 may handle precipitate, biomass, and
other solids
removed during water treatment at the anaerobic bioreactor 120 stage and the
aerobic bioreactor
140 stage. The solids handling system may separate solids from water, and may
have a settling
tank, clarifier, settling pond, or other solids removal mechanism.
[0071] The anaerobic fluidized bed reactor 120 may have a recycle system
121 to continually
fluidize the media at a desired flow rate. The recycle system 121 may allow
for additional
reduction of dissolved selenium and reduce the amount of dissolved selenium
escaping to the next
stage of the water treatment system. The anaerobic fluidized bed reactor 120
may include one
FBR or two smaller FBRs to conserve height when freeboard is limited. The
anaerobic reactor
CA 2969539 2017-06-05
RUSSIO-1CA
14
flow rate may be about 12 to 15gpm/ft2 with a recycle design. A recycle
reactor may provide very
long contact times for water being processed.
[0072] Dissolved selenium may be changed to particulate elemental selenium
on the
anaerobic bioreactor 120. The particulate elemental selenium may be filterable
at this stage, and
may integrate with biomass inside the anaerobic bioreactor 120 to form a
solid. The solid may be
transferred to a solids handling system 190. The solids may be extracted as a
sludge-like biomass
material.
[0073] The elemental selenium/biomass combination may be filtered, removed,
and
transferred through a waste stream 120B to the solids handling system 190 as a
biomass waste
product and later may be removed from the site for further processing or
disposal.
[0074] After solids are removed from feed water treated in the anaerobic
bioreactor 120, the
treated water may be directed through a feed-water pathway 120A to an aerator
130 disposed
between the aerobic bioreactor 120 and one or more aerobic or partially
aerobic bioreactors 140 at
a dynamic polishing stage. The water treated in the anaerobic bioreactor 120
may contain residual
selenium and organic compounds (measured as COD/BOD). Residual organic
compounds may
foul membrane modules making membrane filtration unfeasible. Dynamic polishing
140 may
assist removal of residual COD/BOD to prevent or minimize membrane fouling. By
managing
dissolved oxygen levels in water prior to delivery of water to the one or more
aerobic or partially
aerobic bioreactors 140, the dynamic polishing stage 140 may be optimized to
improve removal
of carbonaceous matter while minimizing oxidizing and re-dissolving of
residual selenium
precipitate.
[0075] The aerator 130 may be a packed column, diffuse bubble aeration, or
other aeration
device. The aerator 130 may be used to introduce dissolved oxygen into the
feed water stream
from the upstream anaerobic bioreactor 120. The level of oxygen introduced to
the stream can be
varied from 0 to 14 mg/L to a desired set point. A typical oxygen set point
may be between 2 and
8 mg/I of oxygen. Dissolved oxygen levels may be optimized to balance a
desired increase in
consumption of residual carbon nutrient and increased production of biomass to
be filtered at the
CA 2969589 2017-06-05
RUSSIO-1CA
dynamic polishing stage 140 with a desired low level of selenium precipitate
oxidizing and re-
dissolving into the water.
100761 After aeration of treated water at the aeration stage 130, water may
be directed
through a feed water pathway 130A into one or more aerobic or partially
aerobic bioreactors 140
for dynamic polishing to prepare the water for downstream membrane filtration.
The aerobic
bioreactor 140 may include a recycle system to fluidize growth media inside
the bioreactor at a
desired flow rate and or help control dissolved oxygen levels.
100771 The aerobic bioreactor 140 comprising the dynamic polishing system
may include
one or more fluidized bed or one or more fixed bed bioreactors, which may be
known as a packed
bed bioreactor. A fixed bed bioreactor may be comprised of a bioreactor
housing and a packed
bed comprising a growth media suitable for development of a bacteria colony
thereon. In many
cases, the growth media in the aerobic bioreactor 140 may be similar to or the
same as growth
media used in the anaerobic bioreactor 120, such as granular activated carbon
("GAC"), 30-90
mesh silica, sand, a combination thereof, or other soluble or insoluble growth
media.
100781 Unlike the fluidized bed of the anaerobic bioreactor 120, the packed
bed of a fixed
bed aerobic bioreactor 140 may not be fluidized and may act as a media filter
for removal of
biomass and residual selenium precipitate.
100791 Some embodiments may use a dynamic polishing system in place of the
aerobic
bioreactor 140, where the dynamic polishing system may operate in complete
anaerobic mode
with no aeration, partial aerobic mode having partial aeration, or full
aerobic mode with
maximum aeration depending on the level of dissolved oxygen introduced in the
water at the
upstream aeration system 130.
100801 Aeration may be controlled by monitoring levels of dissolved oxygen
using a
dissolved oxygen sensor. Oxygen levels may be measured within bioreactors 140
of the dynamic
polishing system, or at the effluent stream 140A of the dynamic polishing
system. Air flow may
be adjusted upstream at the aeration stage 130. Air flow adjustment may be
controlled by a
programmable logic controller providing control signals to the aeration system
in response to data
received by the programmable logic controller from the dissolved oxygen
sensor. The amount of
CA 2969589 2017-06-05
RUSS 10-1CA
16
dissolved oxygen in the dynamic polishing step can be adjusted in the range of
0 to 14 mg/L
dissolved oxygen.
[0081] Biomass and precipitated selenium/biomass solids produced or
retained in the
dynamic polishing system 140 may be transferred to a solids handling system
190 through a waste
stream channel 140B and later may be removed from the site for further
processing or disposal.
[0082] After water has been treated by the dynamic polishing system 140,
water may be
directed to a membrane filtration system 150 for removal of residual selenium
precipitate. The
membrane filtration system may be a membrane bioreactor, a microfiltration
filter, or an
ultrafiltration filter. The membrane filter 150 may be an ultrafiltration
membrane filter having a
pore size of between about 0.1 to about 0.001 microns. In another embodiment,
the membrane
filter 150 may be a microfiltration membrane filter having a pore size of
between about 0.1 to
about 3 microns. Water filtered by the membrane filtration system 150 may
produce a clean
permeate stream 150A and or a concentrate stream 150B. The clean permeate
stream may be
discharged from the water treatment system 100 as clean effluent 170.
[0083] The concentrate stream may be recycled to the aerator 130 or may be
channeled to a
membrane concentration system 160 for further filtering of water treated by
the water treatment
system. The membrane concentration system may comprise a reverse osmosis
filter system or
nanofiltration filter system.
[0084] Water filtered by the membrane concentration system 160 may also
produce a clean
permeate stream 165 and a concentrate stream 160B. The clean permeate may be
discharged as
clean effluent 180. The concentrate stream 160B containing residual dissolved
selenium may be
fed back to the feed water pathway 110 at the beginning of the water treatment
system 100 for
additional treatment.
[0085] The membrane concentration system 160 may include a bypass line 170,
which
allows for 0 to 100% of the flow from the downstream membrane filtration
system 150 to be
directed to the membrane concentration system 160. The fraction of water 150A
from the
membrane filtration step 150 that is not sent to the membrane concentration
step 160 may be
discharged as clean effluent 180 via the bypass line 170. Clean effluent
discharged from the water
CA 2969589 2017-06-05
RUSS10-1CA
17
treatment system after treatment of the feed water for selenium removal may be
suitable for
surface discharge, as opposed to human drinking water.
[0086] Figure 2 illustrates a conceptual diagram of an embodiment 200
showing an
anaerobic bioreactor, such as the anaerobic bioreactor 120. The bioreactor may
be comprised of a
bioreactor housing 202 containing a bioreactor bed 204. The bioreactor housing
202 may be made
of concrete, fiberglass, HDPE, steel, or other suitable material.
[0087] The bioreactor bed 204 may be comprised of growth media 206 suitable
for
development of a bacteria colony thereon. Bacteria may colonize on the surface
of the growth
media 206, which may provide a high surface area for biofilm formation. The
growth media 206
may include granular activated carbon ("GAC"), 30-90 mesh silica, sand, a
combination thereof,
or any other growth media. In many cases, the growth media may be insoluble
growth media. It is
understood that the term insoluble growth media may include growth media that
is substantially
insoluble.
[0088] The bioreactor bed 204 may be fluidized by passing water through the
granular
growth media 206 at high enough velocities to suspend the granular material so
it behaves as
though it were a fluid. Fluidization of the bioreactor bed 204 may require
recycling of effluent at a
hydraulic loading rate of 2 to 5 gpm/112.
[0089] The bioreactor of embodiment 200 may be operated under anaerobic
conditions so
that bacteria forming the biofilm may engage in anoxic or anaerobic
respiration. The fluidized bed
biorcactor may have a nutrient source 208, which may inject a nutrient to
stimulate bacterial
growth and respiration. The nutrient may be comprised of acetate, glucose,
molasses, methanol, or
other nutrient sources. In many cases, the nutrient may be a carbon based
nutrient. In some cases,
the nutrient source 208 may be a liquid injection system that may periodically
inject nutrient to
the incoming water stream.
[0090] Feed water entering the bioreactor and passing through the fluidized
bed may come
into contact with a biofilm of bacteria colonies engaged in anaerobic
respiration. Dissolved
selenium, such as selenate or selenite, coming into contact with such a
biofilm may be
CA 2969589 2017-12-04
RUSS10-1CA
18
transformed to a selenium precipitate through bacterial reduction. Selenium
precipitate may then
be suitable for filtration.
[0091] Figure 3 is a flowchart illustration of an embodiment 300 showing a
series of steps
for removing soluble selenium using a water treatment system.
100921 In block 302, dissolved selenium is precipitated and concentrated as
solid waste. This
step may be performed using an upflow bioreactor, such as the anaerobic
bioreactor 120, where
dissolved selenium may be converted into elemental selenium as a precipitate.
The precipitate
may become entrained with and become concentrated in the biomass within the
bioreactor 120. A
recycle system 121 may periodically capture and remove excess biomass from the
bioreactor 120
in block 304.
100931 In block 306, the water may be aerated and polished to remove
carbonaceous
compounds. Such a step may be performed by an aerator 130 and aerobic
bioreactor 140.
[0094] The residual selenium may be filtered in block 308. Some of the
filtration may occur
in the aerobic bioreactor 140, while other filtration may occur in the
membrane filtration 150.
Some systems may have a membrane concentrator 160, which may concentrate the
residual
selenium in block 310 and return the concentrate to the system for further
processing.
100951 The cleaned water may be discharged in block 312.
[00961 Figure 4 is a diagram illustration of an embodiment 400 showing a
biologically active
water treatment system. A multi-stage water treatment system may have an
upflow bioreactor 404
at a first stage, a downflow bioreactor 406 at a second stage, and a
filtration system 408 at a third
stage. The upflow bioreactor 404 may include an expanded bed. The downflow
bioreactor 406
may include a packed bed. The downflow bioreactor 406 having a packed bed may
be referred to
as a downflow biofilter.
[0097] Many systems may be designed with multiple trains. In such systems,
a single train
may have a set of upflow and downflow bioreactors that may be operated
together. Several trains
may be used in parallel to treat large volumes of water. In many such systems,
trains may be taken
offline for servicing or for periods of reduced water flow.
CA 2969589 2017-12-04
RUSSIO-1CA
19
[0098] The multi-stage water treatment system may include a solids handling
system 412 for
treating solids removed from water treatment system at one or more stages. The
solids handling
system 412 may receive solid waste from the upflow bioreactor 404, from the
downflow
bioreactor 406, or from the filtration system 408. The solids handling system
412 may have a
settling tank, clarifier, settling pond, or other solids handling mechanisms.
[0099] Various features and operations of the water treatment system may be
controlled or
managed by a programmable logic controller (sometimes referred to as a PLC).
The
programmable logic controller may interface with a touch screen computer
having a graphical
display showing water treatment system modes, parameters, and systems.
[0100] The programmable logic controller may control or monitor a number of
mechanical
components of the water treatment system. For example, flow meters associated
with water flow
in water channels or conduits throughout the water system may send flow rate
data to the
programmable logic controller, including flow data associated with water flow
at influent and
effluent ports for each of the first and second stage bioreactors and for the
filters and solids
handling systems.
[0101] Automated valves may be provided which may be air actuated or
electronically
actuate may open and close to direct water for various modes of operation of
the water treatment
system, including service mode ( e.g., treating the water), backwash mode,
offline mode, startup,
and taking bioreactor trains offline. Each operation may comprise a different
valve configuration
to direct water flow as needed for the mode operation. The programmable logic
controller may
send signal to open or close the automated valves and direct water flow for
each mode of
operation.
[0102] Flow control valves may be provided for adjusting water flow rate by
partially
opening or closing water channels, including for example influent and effluent
ports. The flow
control valves may open and close at variable parameters to meet a water flow
set point. The flow
control valves may open and close in response to communications received from
the
programmable logic controller. The programmable logic controller may control
the opening and
CA 2969589 2017-06-05
RUSSIO-ICA
closing of the flow control valves in response to flow data received from flow
meters. Thus the
flow control valves may track to a set point.
[0103] Water pumps may also be provided, such as water pumps for driving
feed water into
the water treatment system, an effluent pump for pumping water out of a
downflow bioreactor,
and a backwash pump for pumping clean water back upward into a bottom of the
downflow
bioreactor and up through the packed bed for dislodging gas or for backwashing
solids. The
pumps may be fixed speed pumps with only on/off modes or may be variable drive
pumps that
operate at variable speeds between 0% and 100% to meet a water flow set point
as measured by a
flow meter. The water pumps may be operated or controlled by the programmable
logic controller
in response to communications or data received from various sensors, such flow
meters and
pressure gauges.
[0104] Pressure gauges may also be provided for measuring pressure and
sending pressure
data to the programmable logic controller. Pressure gauges, such as an
effluent pressure gauge,
may be disposed downstream of bioreactors to measure effluent pressure to
track gas formation as
a measurement of biological activity rate in a bioreactor bed. Effluent
pressure may also be used
to measure bed permeability.
[0105] The water treatment system may also include other instruments for
measuring
turbidity, pH, and oxidations reduction potential such as turbidity meters,
probes that measure
scattered light, electrode probes for measuring pH and oxidation reduction
potential. Bed level
may be measured using a sonar or ultrasonic sludge blanket detector and or
using turbidity.
[0106] Turbidity data may also be used to measure filtration efficiency.
Data from these
instruments may be communicated to the programmable logic controller which may
monitor or
adjust water treatment system modes or operations in response to the data
received.
[0107] A chemical metering pump may also be provided for injecting
chemicals into
channels where desired. The rate of chemical injection by the chemical
metering pump may be
regulated by the programmable logic controller in response to date received by
the PLC from
sensors such as flow meters.
CA 2969589 2017-06-05
RUSS10-1CA
21
[0108] Thus, many of the water treatment operations may be automated or
controlled using a
PLC. It should be understood that the programmable logic controller and other
referenced valves,
pumps, motors, gauges and other measuring devices may be used as desired in
other embodiments
as well.
[0109] Industrial effluent containing soluble selenium or other
contaminants may be fed into
the water treatment system from a feed water source and directed into the
biologically active
upflow bioreactor 404 for single pass treatment of the feed water. A carbon
based nutrient may be
introduced into the feed water before it is fed into the upflow bioreactor 404
to stimulate bacterial
growth and respiration as it comes into contact with the biological colony
growing in the upflow
bioreactor bed. The teed water may mixed with a biological growth substrate,
including macro
nutrients such as carbon, nitrogen, and phosphorous and micro nutrients such
as molybdenum,
cobalt, zinc, and nickel which may be fed through the bottom of the reactor.
It should be
understood that other micro nutrients available to one skilled in thc art may
also be used.
[0110] The environment in the upflow bioreactor may be maintained in a
substantially
anaerobic condition to foster bacterial reduction. The water treatment system
may be configured
for about 80c% reduction of soluble contaminants at the upflow biorcactor 404
stage. The
expanded bed of the upflow bioreactor 404 may allow for concomitant release of
gas and
retention of particulate selenium.
[0111] After single pass treatment of feed water in thc upflow bioreactor
404, the effluent
may be directed through a water conduit to the downflow bioreactor 406 for
further treatment. A
chemical injection system 414 may be associated with the feed water pathway
between the upflow
bioreactor 404 and the downtlow bioreactor 406. A chemical such as ferric
chloride or an
organosulfide may be introduced into effluent from the upflow bioreactor 404
to improve or
increase reduction of soluble metals prior to biofiltration. Injection of
ferric chloride or
organosulfide into effluent from the upflow bioreactor 404 may promote
coagulation of biological
material in the downflow bioreactor 406. The rate of chemical injection may be
regulated by
communications to the chemical injection system from the programmable logic
controller. The
=
CA 2969589 2017-12-04
RUSSIO-ICA
22
rate of chemical injection may be regulated in response to data received by
the programmable
logic controller from sensors such as flow sensors.
[0112] The downflow bioreactor 406 may include a biologically active packed
bed for
further reduction of any residual dissolved selenium or other reducible
contaminants and may act
as a biofilter for media filtering of any particulate selenium or other
contaminant precipitate
remaining in effluent from the upflow bioreactor 404. The downflow bioreactor
406 may also
consume residual nutrient that may carry over from the upflow bioreactor 404
and convert it into
biomass.
[0113] In some cases, no or little additional nutrient may be introduced
into effluent after
leaving the upflow bioreactor 404 so that carbon consumption in the downflow
bioreactor 404
may be substantially complete. In some cases, the water treatment system may
be configured for
about 20% reduction of soluble contaminants at the downflow bioreactor 404
stage. An advantage
of using a downflow bioreactor 406 to direct water down through a packed bed
is improved
retention of solids by the filtering action of the packed bed.
[0114] The configuration of a first upflow bioreactor 404 stage followed by
a secondary
downflow bioreactor 406 stage for biofiltration provides for a high quality
water stream suitable
for discharge or release into the environment. Such a system may produce a
high quality effluent
by decoupling the selenium reduction and solids removal, while polishing the
water for residual
COD/BOD removal.
[0115] An upflow bioreactor 404 with an expanded bed followed by a downflow
bioreactor
406 having a packed bed allows for a smaller overall system footprint that
other designs. The
removal of gas by the upflow bioreactor 404 while retaining selenium or other
contaminant
precipitate allows for improved permeability of the downflow bioreactor 406
packed bed and thus
reduces the hydraulic head needed to push water through the packed bed. Thus,
the downflow
bioreactor 406 at the second stage may be smaller compared to conventional
fixed bed bioreactors
which require a deep bed and long contact time to achieve both selenium
precipitation and solids
retention.
CA 2969589 2017-06-05
RUSS10-1CA
23
[0116] The downflow bioreactor 406 may have a downstream effluent pump 416
to pull
water from the downflow bioreactor 406 down through the packed bed. Vacuum
assisted transfer
of water through the packed bed further reduces the hydraulic head need for
pushing water
through the packed bed, thus further allowing for a small downflow bioreactor
406 footprint and
for an overall smaller water treatment system footprint.
[0117] An upflow bioreactor 404 with an expanded bed followed by a downflow
bioreactor
406 having a packed bed may produce reduced COD/HOD in the effluent 410. The
reduced
COD/BOD allows for subsequent membrane filtration without substantial membrane
fouling. The
effluent water may also be suitable for direct discharge into ive streams and
into fish and other
wildlife habitats.
[0118] Effluent from the downflow bioreactor 406 may be directed through an
effluent
conduit to a filtration system 408 for further polishing of the effluent. The
filtration system 408
may be a media, multimedia, membrane filtration, or other types of filtration
systems. When
treating power plant effluent, a typical system may use an ultrafiltration
system or a
microfiltration system. Such an ultrafiltration membrane filter may have a
pore size of between
about 0.1 to about 0.001 microns. Such a microfiltration membrane filter may
have a porc sizc of
between about 0.1 to about 3 microns.
[0119] Removal of contaminants such as dissolved selenium may be improved
at the
filtration stage 408 by use of a chemical injection system 420 associated with
the feed water
pathway between the downflow bioreactor 406 and the filtration system 408. A
chemical such as
ferric chloride or an organosulfide may be introduced into effluent from the
downflow bioreactor
406 for increased reduction of soluble metals prior to filtration. The rate of
chemical injection
may be regulated by communications to the chemical injection system from the
programmable
logic controller. The rate of chemical injection may be regulated in response
to data received by
the programmable logic controller from sensors such as flow sensors.
[0120] Ultra-low levels of selenium precipitate (< 5 ug/L total selenium)
may be
accomplished by membrane filtration of fine particulate selenium. In
conventional selenium
treatment bioreactors, the particulate selenium can escape the bed and
contribute to selenium in
CA 2969589 2017-12-04
RUSSIO-1CA
24
the effluent. The reduction of effluent COD/BUD to facilitate membrane
filtration without
membrane fouling allows removal of escaped selenium precipitate from the
effluent. The
membrane filtration system may remove, concentrate, and recover any remaining
particulates that
may be measured as Total Suspended Solids.
[0121] Figure 5 illustrates an embodiment 500 showing an upflow bioreactor
502, which
may be similar to the anaerobic bioreactor 120 or other upflow bioreactors
illustrated herein.
[0122] The bioreactor 502 may have a housing 504 that contains a bioreactor
bed 506. The
bioreactor bed 506 may operate in an expanded bed formation, where the growth
media 510 may
be fluidized by the upward flow of water.
[0123] The bioreactor housing 504 may be made of carbon steel, coated
carbon steel,
stainless steel, fiberglass, or plastic. It should be understood that the
bioreactor housings of the
present invention may be made of any suitable material available to one
skilled in the art, in
addition to carbon steel, coated carbon steel, stainless steel, fiberglass, or
plastic. The bioreactor
housing may be made using molding, machine casting, or any other method
available to one
skilled in the art, which may depend on the material used to make the
bioreactor housing 504.
[0124] The upflow bioreactor 502 may be configured for receiving feed water
508 from a
lower region of the bioreactor bed 506 so that water may flow substantially
upward through the
bioreactor bed 506. The bioreactor bed 506 may be an expanded bed comprised of
an insoluble
growth media 510 suitable for development of a bacteria colony thereon.
Bacteria may colonize
on the surface of the insoluble growth media 510. The use of selected
insoluble growth media 510
in the biologically active bioreactor may provide high surface area for
bacterial biofilm formation.
The insoluble growth media 510 may include granular activated carbon ("GAC"),
30-90 mesh
silica, sand, or a combination thereof. In a preferred embodiment the
insoluble growth media 125
may be GAC.
[0125] The expanded bed 506 of the upflow bioreactor 502 may be formed by
channeling
feed water 508 through the bottom of the upflow bioreactor 502 so that water
is pushed or pulled
evenly up through the insoluble growth media 510. 4 he water may be evenly
dispersed up
through the bioreactor bed 506 using a water distribution system. In a
preferred embodiment, the
CA 2969589 2017-06-05
RUSSIO-1CA
bioreactor bed 506 may be extended by pushing or pulling water up through the
bioreactor bed
506 at a flow ranging from between about 2 to about 7 US gallons per minute
per square foot
(gpm/ft2) of tank area, or an upflow velocity of 25 to 60 feet per hour
(ft/hr).
[0126] The upward flow may be adjusted to provide plug flow or laminar flow
within the
bioreactor bed 506, while being low enough that the growth media 510 does not
flow out of the
bioreactor 502. Operating with an upflow hydraulic loading rate of between
about 2 and about 7
gpm/ft2 allows for gas resulting from biological activity to escape past the
insoluble growth
media 510 with the momentum of the water without disrupting the bed in a
manner that may
release substantial amounts of reduced selenium precipitate. The empty bed
contact time (EBCT)
of the upflow bioreactor 210 may vary from 5 minutes to 40 minutes depending
on feed water
temperature and the level of contaminant removal needed.
[0127] Bed expansion may vary between about 10% and about 40% of a static
level and may
be completed using a single pass flow with no recycle of the effluent to the
upflow bioreactor 502
feed. Bed expansion may be measured using impedance spectroscopy or turbidity
to evaluate the
height of the bed. Impedance spectroscopy or turbidity may also be used to
evaluate growth of the
bioreactor bed 506 from biofilm growth and incomplete expulsion of gas. When
the expanded bed
reaches a specified height, impedance spectroscopy or turbidity sensors may
trigger either a
mechanical backwashing event that is used to remove a portion of the biofilm
or a short pulse to
release any entrained gas.
[0128] An upflow bioreactor 502 having an expanded bioreactor bed 506 may
allow for
concomitant release of gas and retention of precipitate. Furthermore, use of
an upflow bioreactor
502 having an expanded bed 506 may allow improved reduction of contaminants
while reducing
expanded bed contact time and overall pre-discharge water treatment time
without recycling
effluent at the primary bioreactor.
[0129] Hydraulic loading rates greater or lower than the preferred range
may not
concomitantly accomplish of the benefits allowed by an expanded bed 506
configuration. Water
flowing up through the bottom of a bioreactor bed at hydraulic loading rates
equivalent to greater
than 10 gpm/ft2 may fluidize the insoluble growth media 510 which allows for
release of
CA 2969589 2017-06-05
RUSSIO-1CA
26
precipitated selenium from the bioreactor bed 506. A fluidized bed may require
recycling the
treated water to obtain optimal water treatment.
[0130] Alternatively, water flowing up through the bottom of a bioreactor
bed at hydraulic
loading rate velocities of less than 2 gpm/ft2 often results in a packed or
fixed bed which tends to
retain gas resulting from biological activity. A biologically active packed
bed tends to lose
permeability over time because of entrained gas.
[0131] In one or more aspects of the present invention, the influent water
feed rate is
controlled to a low enough level to optimize the benefits of plug flow,
eliminating the recycle and
concentration of waste products from the effluent of the upflow bioreactor
502, reducing impact
energy between the particles, allowing for greater biomass retention, and
allowing more effective
removal of biomass/reduction precipitate matter from water before delivering
effluent to
subsequent stages of a water treatment system. The feed rate may be maintained
at a high enough
rate sufficient to expand the bed and allow release of gas 514 during
treatment, which is not
possible using the low non-fluidizing upflow velocities previously used in the
industry. The gas
512 generated within the bed due to microbial respiration and fermentation may
be released from
the expanded bed 506 and carried to the top of the bed 506 and expelled as gas
released to the
atmosphere 514.
[0132] Over time, the expanded bed 506 level may increase because of bed
growth caused by
biology growth on the insoluble growth media 510. Growth of the bioreactor bed
506 may extend
upward and begin to decrease the efficiency of the bioreactor 502 or interfere
with effluent flow.
[0133] Bed growth may be automatically managed by periodic air scouring to
remove
biomass from the insoluble growth media. Air scouring may include blowing air
into the
expanded bed 506 through a diffuser to break up biomass accumulated on the
insoluble growth
media. A bypass valve may be provided in an effluent pathway at a downstream
position from the
upflow bioreactor for diverting biomass and carbonaceous matter to a waste or
solids handling
system during or shortly after air scouring.
[0134] The expanded bed 506 level may be measured by measuring turbidity
using turbidity
meter or probes that measure scattered light. The bed level of the expanded
bed 506 may also be
CA 2969589 2017-06-05
RUSSIO-ICA
27
measured using a sonar or ultrasonic sludge blanket detector and or using
turbidity. A
programmable logic controller may control an air scour system and may turn the
air scour system
on or off in response to data received from turbidity sensors or from a sonar
or ultrasonic sludge
blanket detector. The air scour system may be disposed adjacent to the
bioreactor bed and may be
configured so that air may be flown into the insoluble growth media to remove
accumulated
biological matter or growth.
[0135] Thus, a significant advantage of configuring the bioreactor 502 with
an expanded bed
506 is the ability to optimize hydraulic loading for retention of reduction
precipitate and solids
and the concomitant removal of gas from the bed. For example, the biological
reduction of
oxyanions such as selenate and selenite will produce nanoparticles. These
submicron particles can
more easily be retained within the bed by controlling the water flow rate to
avoid bed fluidization
while still operating the upflow bioreactor 502 just above the minimum upflow
velocity for
expulsion of gas.
[0136] Another advantage to the upflow bioreactor 502 being configured with
an expanded
bed is the ability to concurrently reduce multiple contaminant species from
which reduction
produces end products having different states of matter. For example,
reduction of selenate and
selenite results in a selenium precipitate (e.g., a solid); reduction of
nitrate and nitrite results in
nitrogen (e.g., a gas); and the reduction of perchlorate results in a soluble
chloride ion. The use of
an upflow bioreactor 502 configured with an expanded bed 506 may allow for the
concurrent
treatment of these and other contaminant species. The ability of the expanded
bed 506
configuration to concurrently reduce various contaminant species having
different end product
forms may be facilitated by its ability to concomitantly retain reduction
precipitate and biomass
while releasing gas from the bed.
[0137] An upflow bioreactor 502 having an expanded bed 506 also provides
for versatile
water treatment system configurations that may utilize the benefits of the
expanded bed
configuration, including the ability to concurrently remove a combination of
industrial effluent
contaminants such as concurrent treatment of a combination of nitrate,
perchlorate, selenium, or
the concurrent pretreatment of nitrate, perchlorate, selenium, arsenic, or
mercury.
CA 2969589 2017-06-05
RUSS10-1CA
28
[0138] Figure 6 is a diagram illustration of an embodiment 600 showing a
water treatment
system 602. The water treatment system 602 may have an upflow bioreactor 604
as a first stage
and a downflow biorcactor 606 as a second stage.
101391 The water level 608 in the second stage bioreactor 606 may be
maintained at a
consistent level by drawing effluent out of the bioreactor 606 with a effluent
pump, or may be
allowed to vary with the static pressure used to drive the water through a
growth medium 610,
such as GAC. The contact time of the second stage bioreactor 606 may be
maintained in the range
of 10 to 40 minutes wherein the second stage biofilter may receive effluent
from the expanded
bed bioreactor 604 without the addition of carbon nutrient to the water
channeled to the second
stage bioreactor 606. Channeling effluent to the second stage bioreactor 606
without adding
additional carbon nutrient may culture a 'stressed' biofilm suitable for
capturing and adsorbing any
residual carbon material released from the first bioreactor 604.
[01401 Gas produced by biological activity in the second stage bioreactor
606 may remain
trapped within the insoluble growth media 610 and biofilm matrix structure and
may be
periodically released. Degassing may be accomplished through a combination of
hydraulic and or
mechanical means. Gas may be released from the second stage bioreactor 606 by
feeding a burst
of clean water 612 into the bottom of the bioreactor 604 from a stored treated
effluent 614.
[0141] Biofilm growth and bed permeability may be measured by monitoring
the driving
pressure across the bed in either static head or the vacuum level of the
effluent. A pressure gauge
may be used to measure the static head. In some case, an effluent pressure
gauge may be used to
measure the vacuum level of the effluent. The effluent pressure gauge may be a
compound gauge
that may measure both positive and negative pressure. When the pressure
reaches a level that may
limit the bioreactor 606 from operating at a desired flow rate, a backwash may
be performed by
feeding clean water 612 into the bottom of the bioreactor 606 from stored
treated effluent 614.
Solids removed from the growth medium 610 during the backwash event may be
collected at the
top of the bioreactor 606 and transferred to a solids handling system 616.
101421 Solids may be &watered by conventional means creating a solid waste
product and a
liquid stream return feed 618 that may be returned to the preliminary feed of
the water treatment
system 602.
CA 2969589 2017-12-04
RUSSIO-1CA
29
[0143] Figure 7 is a diagram illustration of an embodiment 700 showing an
example water
treatment system 702 that may be suitable for the concomitant removal of
nitrate, mercury,
arsenic, and selenium to trace levels. In this embodiment, the primary
bioreactor 704 and the
secondary bioreactor 706 may be coupled to a tertiary filter 708. The tertiary
filter 708 may be
comprised of a dual media filtration system, microfiltration system, an
ultrafiltration system, or
other filter mechanism. A chemical injection 710 may introduce ferric chloride
or organosulfide
upstream of the filter 708. The chemical injection 710 may help with pH
adjustment to optimize
filter performance and metal precipitation. The addition of ferric chloride or
organosulfide may
promote precipitation of arsenic and mercury compounds previously reduced in
the bioreactors
704 and 706.
[0144] Effluent from the filter 708 may be stored in a finished water
storage tank 712 and
used for periodic backwashing and degassing of both the secondary bioreactor
706 and the tertiary
filter 708 In this embodiment, waste residuals 735 may be thickened and
dewatered in a solids
handling system 714 in order to bind and collect any colloidal metal material.
Solid or thickened
cake 716 may be removed as a waste product and liquid waste 718 may be
returned to the
preliminary feed of the water treatment system 702, discharged directly into
the environment, or a
combination thereof.
[0145] Figure 8 is a diagram illustration of an embodiment 800 showing a
downflow
bioreactor 802. The bioreactor 802 may have a housing 804 and a bioreactor bed
806, which may
comprise growth media 808.
[0146] The bioreactor housing 804 may be comprised of carbon steel, coated
carbon steel,
stainless steel, fiberglass, or plastic. It should be understood that the
biorcactor housings of the
present invention may be comprised of any suitable material available to one
skilled in the art, in
addition to carbon steel, coated carbon steel, stainless steel, fiberglass, or
plastic. The bioreactor
housing may be made using molding, machine casting, or any other method
available to one
skilled in the art, which may depend on the material used to make the
bioreactor housing.
[0147] The bioreactor bed 804 may be configured as a packed bed and may be
between
about two feet and twenty feet in depth. Bacteria may colonize on the surface
of the insoluble
CA 2969589 2017-12-04
RUSSIO-1CA
growth media 806 to form a biofilm. The use of selected insoluble growth media
806 in the
biologically active bioreactor may provide high surface area for bacterial
biofilm formation. The
insoluble growth media 806 may include GAC, 30-90 mesh silica, sand, green
sand, any other
growth media, or a combination thereof.
[0148] The downflow bioreactor 802 may be configured to receive feed water
808 through
an influent portal near an upper area of the bioreactor 802. The feed water
may be pushed or
pulled down through the downflow bioreactor 802 and through the packed bed 804
so that
contaminants, such as selenate and selenite, and carbonaceous matter may come
into contact with
the biofilm in the biologically active biorcactor bed 804. Soluble
contaminants may be
transformed to precipitates via bacterial reduction. For example, soluble
forms of selenium may
be precipitated through biological reduction to a selenium precipitate. Carbon
nutrient ma)' be
converted to biomass as it is consumed by the bacteria colony within the
bioreactor bed 804. The
bioreactor bed 804 may act as a biofilter to retain selenium precipitate or
other contaminant
precipitate as well as biomass. After treated feed water passes through the
downflow bioreactor
802, it may be delivered out of the bioreactor 802 at an effluent port near
the bottom of the
bioreactor housing.
[0149] Other contaminants may also be converted by bacterial reduction in
the downflow
bioreactor 802 for removal, such as the reduction of nitrate and nitrite
results in nitrogen (e.g., a
gas) and the reduction of perchlorate results in a soluble chloride ion.
[0150] Water may be treated through the downflow bioreactor 802 when the
bioreactor bed
804 is in a production mode. In a production mode, water may be pumped or
pulled through the
packed bed 804 so that contaminants in the water may come into contact with
the biologically
active biofilm. The environment within the downflow bioreactor 802 may be
maintained in anoxic
(e.g., anaerobic) condition to stimulate anoxic respiration and biological
reduction. The flow rate
of the water may be set so feed water remains in the bioreactor 802 with
sufficient reaction time,
or hydraulic retention time (HRT) to reduce the contaminants to a desired
level. The hydraulic
retention time may be between about 15 minutes to about 4 hours.
CA 2969589 2017-06-05
RUSS I 0-1CA
31
[0151] An effluent pump 810 may be used to draw or pull water out of the
bottom of the
bioreactor 802. Such a pump may provide negative pressure or vacuum, and may
provide driving
head to pull the water through the bioreactor bed 804 where dissolved
contaminants may be
reduced by biological activity and, in the case of precipitate end products,
retained by the bed 804.
[0152] When driving head may be created below the bioreactor bed by drawing
a vacuum,
minimal liquid level may be used above the bioreactor bed 804 to push the feed
water through the
packed bed 804. As a result, downflow bioreactor tanks of this configuration
may be considerably
smaller compared to conventional fixed bed bioreactor tanks, which may use a
large column of
water over the bioreactor bed to provide driving head. Furthermore, in
conventional fixed bed
bioreactors, the available maximum head pressure may be limited by the height
of the tank and
the depth of the water column over the bioreactor bed. Maximum head pressure
or head drive may
not be limited by the height of the tank or the depth of the water column over
the bioreactor bed
804, but by the pump 810.
[0153] When the fixed bed bioreactor 802 is operating, bacterial and other
biological
fermentation and respiration activity within the packed bed 804 may produce
gas which can
become trapped in the insoluble growth media and biofilm matrix, reducing the
bed permeability
over time. Similarly, biomass and contaminant precipitate build up in the
packed bed 804 may
also reduce the bed permeability over time. Loss of bed permeability may
reduce bioreactor
efficiency and may impede bioreactor operability. The fixed bed bioreactor 802
may operate
within a broad range of pressure, such as between about negative (-) 5 psi and
about 10 psi (0-
23.1 ft H20), associated with bed permeability.
[0154] Figure 9 is a diagram illustration of an embodiment showing a graph
of time 902
verses vacuum pressure 904. The vacuum pressure 904 may be measured by vacuum
asserted by
an effluent pump at the bottom of a downflow bioreactor, such as the
biorcactor 802. The graph
may show production modes 906, 908, and 910, as well as degassing events 912
and 914.
[0155] Effluent pressure data may be received from an effluent pressure
gauge that may be
mounted upstream from an effluent pump. This metric may allow for monitoring
of biological
activity and biological reaction kinetics inside a biologically active bed.
Gas production may also
CA 2969589 2017-12-04
RUSSIO-ICA
32
be an indicator of biological activity. Thus, the rate of effluent vacuum
pressure increase may
indicate the biological reaction kinetics within a bioreactor bed. The
kinetics related to gas
production may be an indicator of the health of the living bacterial biofilm,
which may then be
optimized to further increase kinetics of the bioreactor system. Furthermore,
effluent pressure data
may provide the baseline effluent vacuum level that is achievable, which may
be an indication of
the bed porosity. Bed porosity may be used as an optimization point to control
solids retention
within the bed.
101561 An automated degassing system may be provided to release gas from a
bioreactor bed
and restore or maintain a desired level of bed permeability.
101571 Effluent pressure data may be obtained using a compound pressure
gauge connected
to an effluent pathway at a position downstream from a packed bed. As
entrained gas accumulates
in the packed bed and reduces bed permeability, a pressure change occurs as
the effluent pump
attempts to suck water through the bioreactor bed. When effluent pressure
reaches a
predetermined level or falls within a predetermined range, the effluent
pressure gauge may signal
a backwash pump motor to turn on to initiate pumping clean water from the
filtration system into
a backwash water conduit. The backwash pump may include a fixed speed motor or
a variable
frequency drive.
[0158] In a typical use case, an effluent pressure gauge may signal a
backwash pump to turn
on when pressure associated with suction of effluent from a downflow
bioreactor is between
about 2 psi and about negative (-) 2 psi. Operation of the backwash pump may
be controlled by a
programmable logic controller in response to data received by the programmable
logic controller
from the effluent pressure gauge.
[0159] Clean water from the filter system may be pumped by a backwash pump
may be
directed by a backwash water conduit into a downflow bioreactor through a port
in the bottom of
the downflow bioreactor below or adjacent to a bottom portion of the packed
bed. The upward
force of the clean water being pumped into the bottom of the downflow
bioreactor may help
dislodge and blow out gas entrained in the packed bed. The dislodged gas may
rise up through the
water and be released from the downflow bioreactor through an exit port near a
top area of the
CA 2969589 2017-06-05
RUSSIO-1CA
33
bioreactor. The degassing system may pump water into the bioreactor up through
the packed bed
for only a short duration to facilitate dislodging of gas without dislodging
substantial amounts of
solids or waste from the system.
[0160] During the degas event, water may flow through the bioreactor system
in a reverse
direction at a hydraulic loading rate of about 5 to 15 gallons/minute per
square foot of bioreactor
surface area. The reverse flow of the water during the degas event may
continue for between
about 5 seconds and about 2 minutes, and sometime for about 60 seconds.
[0161] After a degassing event to remove entrained gas from the packed bed,
if effluent
pressure data indicates that the packed bed has failed to recover permeability
after the gas flush,
then failure to recover permeability may be caused by biomass, precipitate, or
other solid waste
accumulating in the packed bed. When effluent pressure data received shortly
after gas flush
indicates continued reduced permeability, the effluent pressure control gauge
may signal the
backwash pump to initiate a biomass backwash event. The biomass backwash
event, also known
as a biomass flush, may continue until accumulated solids are transferred to a
solids handling
system. The biomass backwash event may continue for a substantially longer
period of time than
a gas backwash event. The backwash event may be manually operated or may be
automated using
a programmable logic controller. Parameters of the backwash pump may be set in
and controlled
by the programmable logic controller, wherein the programmable logic
controller may operate the
backwash pump in response to data received by the programmable logic
controller from the
effluent pressure gauge. The reverse flow of water during the backwash event
may continue for
between about one and twenty minutes.
[0162] Figure 10 is a diagram illustration of an embodiment 1000 showing a
downflow
bioreactor 1002, such as the bioreactor 140, which may have a degassing device
1004. The
bioreactor 1002 may have a packed bed 1006, which may be agitated by the
degassing device
1004 to assist release of gas, precipitate, and or carbonaceous matter
resulting from biological
activity. The degassing device 1004 may comprise a drive shaft 1008 extending
into the
bioreactor bed 1006, wherein the drive shaft 1008 includes one or more tines
1010 extending
laterally through the bed and may be rotated at various depths. The degassing
device 1004 may
CA 2969589 2017-06-05
RUSS1O-ICA
34
include a motor for actuating rotation of the drive shaft 1008 for agitating
the bed during a degas
event to assist with dislodging the entrained gas, precipitate, and or
carbonaceous matter from the
bioreactor bed 1006. During a degassing sequence, water may be pumped up
through the bottom
of the bioreactor bed 1006 at a flow rate of between about 1 to about 15
gpm/ft2 during rotation of
the degassing device 1004 to further expel entrained gases from the bioreactor
bed 1006.
[0163] The automated degassing feature and automated backwash feature may
reduce the
driving head needed to push water through the bioreactor bed by restoring and
maintaining
optimal bed permeability. Thus, the automated degassing feature and automated
backwash feature
may allow for reduced bioreactor tank height and volume. This is an important
cost consideration,
as the bioreactor height impacts tank volume and height, building height,
shipping costs, tank wall
thickness, and several other cost components.
[0164] Figure 11 is a diagram illustration of an embodiment 1100 showing a
water treatment
system. The water treatment system 1100 treats a concentrated water stream
that is an effluent of
a reverse osmosis system.
[0165] A supply of feed water 1102 is fed into a reverse osmosis filtration
system 1104,
which produces a clean water stream 1108 and a concentrated contaminated water
stream 1110.
The clean water stream 1108 is fed to a mixing tank, while the concentrated
contaminated water
stream 1110 is fed through a multi-stage water treatment process that removes
contaminants and
produces filtered water 1132. The filtered water 1132 is mixed with the clean
water stream 1108
to produce system effluent 1120.
[0166] A typical system may receive feed water 1102 with 40-800 PPB of
selenium, for
example, and may remove up to 98% of the contaminants, yielding a system
effluent 1120 of less
than 1.25 PPB to less than 64 PPB, depending on processing conditions.
[0167] The reverse osmosis filtration system 1104 may produce a
concentrated contaminant
water stream that may have between 50 and 600% higher concentration of
contaminants,
including selenium, mercury, arsenic, or other toxic materials. The higher
concentration of
contaminants may be more easily processed using biological and subsequent
mechanical filtration
mechanisms than water with lower concentrations.
CA 2969589 2017-06-05
RUSS1O-ICA
[0168] The reverse osmosis filtration system 1104 may produce permeate
clean water 1108
and a concentrate 1110 stream. The concentrate may have 140 to 3200 PPB of
contaminants, and
after processing, the filtered water 1132 may have less than 3 PPB to less
than 64 PPB. This
filtered water 1132 may be diluted down with the clean water 1108, yielding
finished water at less
than 1.25 PPB to less than 64 PPB contaminants.
[0169] The reverse osmosis filtration system 1104 may use a pretreatment
system 1106.
Pretreatment may be used to optimize filtration performance to minimize
reverse osmosis scaling,
fouling, and degradation of the filtration membranes. Scaling may occur when
the concentration
of various scale forming species exceeds saturation, which may produce
additional solids in the
membranes. Sealants may include such chemical species as calcium carbonate,
calcium sulfate,
barium sulfate, strontium sulfate, and reactive silica. Since these species
have very low
solubilities, they may be difficult to remove from RO membranes. Scaling
decreases the
effectiveness of the membranes in reducing the solids and causes more frequent
cleanings. A scale
on a membrane provides nucleation sites that increase the rate of formation of
additional scale.
[0170] In order to minimize scaling in the reverse osmosis filtration
system 1104, a
pretreatment system 1106 may use various anti-sealant methodologies to
minimize scaling. While
such methodologies may ensure that the reverse osmosis filtration system 1104
may operate well,
the sealants and anti-scalants are then transferred to the bioreactors in very
high concentrations in
the contaminant concentrate water stream 1110.
[0171] One particularly difficult problem that may occur in such a system
is that the sealants
may be present in supersaturated quantities, which normally may be processed
using an upflow
and downflow bioreactor. However, when the bioreactors are shut down, the
sealants may come
out of solution and cause very real damage to the bioreactors. In many cases,
a power outage or
other shut down of the bioreactors may cause the medium in the bioreactors to
become solidified
with sealants and the anti-scalants. If such a situation were to occur on
industrial sized
bioreactors, the cleaning mechanism may require jackhammers and difficult
manual cleaning of
the bioreactors.
CA 2969589 2017-06-05
RUSS 10-1CA
36
[0172] A typical pretreatment system 1106 may use chemical techniques to
change the
characteristics of feed water 1102 to so that crystal formation is not
favored. An example of a
chemical technique to prevent fouling is lime softening, which involves
chemical processes that
reduce the hardness of the wastewater, essentially preventing material from
precipitating out.
Lime, soda, ash, and NaOH may be used to convert soluble calcium and magnesium
to insoluble
calcium carbonate and magnesium hydroxide. Magnesium hydroxide tends to absorb
silica,
another sealant. These solids may then be collected as sludge through a solids
removal system
1146 of the water treatment system.
[0173] Another softening procedure may involve zeolite in an ion exchange
process. A
strong acid cation resin in the sodium is used to remove scale-forming
cations, such as calcium,
magnesium, barium, and iron. These cations may be exchanged with the sodium to
yield "soft
water," that is, water of low hardness.
[0174] Another pretreatment technique to prevent scaling may be
acidification, which
specifically reduces the crystallization of calcium carbonate. Sulfuric acid
may be used in this
process, but can often increase the formation of sulfate scales. Therefore,
where sulfuric acid
cannot be used, hydrochloric acid may be substituted. Often used with
acidification, or by itself,
are antiscalants. Antiscalants may be chemicals that may be added to
wastewater to minimize
scale carbonate or sulfate based scale. They consist of acrylates and
phosphonates which inhibit
the precipitation of carbonate or sulfanates.
[0175] All of the anti-scalant techniques for the reverse osmosis
filtration system 1104 can
cause highly concentrated levels of both the sealant and anti-sealant to be
present in the
contaminated concentrate water stream 1110. The high concentration of these
species can cause
the bioreactors to solidify when shut down.
[0176] To address the problems with shutting down the bioreactors, the
water treatment
system 1100 may have a deconcentrator operation that may flush the bioreactors
with treated
water to reduce the concentration levels of sealants below a level where they
may cause harm to
the bioreactor. The deconcentrator operation may be performed in an emergency,
such as when
CA 2969589 2017-06-05
RUSS10-1CA
37
power may be lost, or during normal operation when a bioreactor may be taken
offline for
servicing or in response to demand.
[0177] The contaminant concentrate water stream 1110 may have high levels
of selenium
and other toxic metals, often in the range of 100 PPB to 800 PPB ore more.
[0178] A nutrient system 1124 may inject nutrients that may be consumed by
biological
agents in the bioreactors. The nutrients may include various sugars and other
carbon based
nutrients that maintain biological activity.
[0179] A pump 1128 may supply incoming water into an upflow bioreactor
1112, where a
majority of biological activity may occur. The upflow bioreactor 1112 may
maintain an upward
water flow of about 2 to 5 gpm/ft2 in a plug flow regime.
[0180] The upward flow of water may cascade over a weir or barrier directly
into a
downflow bioreactor 1114.
[0181] The upward flow of water in the upflow bioreactor 1112 may be
maintained such that
the weight of the media 1122 with its biofilm may keep the media 1122 inside
the bioreactor 1112
and not be carried over the barrier. Higher levels of flow may cause the media
to be carried by the
water flow into the second bioreactor 1114. Lower levels of flow may cause the
media to settle at
the bottom and the bioreactor bed may not be fully expanded.
[0182] The upward flow of water in the uptlow bioreactor 1112 may help
express any gasses
that may be generated during the biological activity. In many cases, the
bioreactor 1112 may
produce hydrogen sulfide (H2S) or other gasses. As the water reaches the top
of the bioreactor
1112, the gasses may be expressed into the atmosphere. In some cases, the
gasses may be
collected.
[0183] The upflow bioreactor 1112 may have colonies of bacteria, fungi,
yeast, or other
biological agents that may consume the nutrients, but also may convert
dissolved materials, such
as the various forms of selenium including selenite and selenate, into
elemental selenium, which
may be a solid form. The solids may then be captured in the biomass of the
upflow reactor 1112,
the packed bed of the downflow reactor 1114. The upflow bioreactor 1112 may
CA 2969589 2018-05-02
RUSSIO-1CA
38
operate in at least a partial anaerobic condition, such that the biological
agents may consume and
process dissolved materials.
[0184] The downflow bioreactor 1114 may receive treated water from the
upflow bioreactor
1112. This water may contain excess carbon-based nutrients that may not have
been consumed by
the biological agents in the upflow bioreactor 1112, as well as particles of
selenium or other
byproducts of the biological digestion. The biological activity in the packed
bed downflow
bioreactor 1114 may consume the remaining nutrients as well as mechanically
trap the solid
particles produced by the biological activity.
[0185] The particles trapped in the media 1126 may be mechanically lodged
in biofilm that
may surround the media particles. In other cases, the particles may be
mechanically trapped by the
tortuosity of the media bed.
[0186] A pump 1130 may draw water out of the bioreactor 1114 and pump
produce filtered
water 1132 to a mixing tank 1118, which may be mixed with the clean water 1108
to produce the
system effluent 1120.
[0187] The bioreactors 1112 and 1114 may become less effective over time,
as biomass may
increase and solid and gaseous contaminants may become entrapped in the media.
Each of the
bioreactors may be flushed to restore the media beds.
[0188] Typically, the upflow bioreactor 1112 may be flushed when the
biomass within the
bioreactor may grow such that the media bed expands past an operational limit.
A typical
automated system may have a series of sensors in the bioreactor that may
measure the height of
the media bed. In some cases, such a system may use a sonar system to measure
the bed depth.
When the bed depth may exceed a predefined limit, an automated controller,
such as a
programmable logic controller 1154 may cause the system to perform a backflush
operation.
[0189] The upflow bioreactor 1112 may be flushed by opening the weir 1148
and pumping
larger amounts of concentrated feed water. The weir 1148 may direct the
overflow to the solids
removal system 1146.
CA 2969589 2017-06-05
RUSS I 0-ICA
39
[0190] During a backwash cycle, clean water may be introduced at flow rates
from 120 to
200% of feed water flow, or 2.4 to 10 gpm/ft2. In some cases, backwash water
flow may be
150%, 250%, 300%, or more of the normal feed water flow rate. The flow of
clean water may be
significantly faster than normal operation, which may cause turbulent flow.
Such flow may cause
the media to mechanically abrade and dislodge portions of biofilm. The biofilm
may be carried
into the weir 1148 and processed by a solids removal system 1146.
[0191] In some cases, air scouring may be performed, where an air manifold
in the bottom of
the bioreactor 1112 may be fed high pressure air. The high pressure air may
form bubbles that
may agitate, aerate, and otherwise abrade the media and the biofilm. In many
cases, the bioreactor
1112 may be normally operated under anaerobic conditions, so that aeration may
disrupt the
normal anaerobic conditions of the biological agents. As such, air scouring
may be performed for
a brief period at the beginning of a backwash cycle, such as 30 to 60 seconds.
The backwash cycle
may then continue flushing with clean water for several more minutes to begin
to reestablish an
anaerobic condition.
[0192] The bioreactor 1114 may undergo a backwash cycle from time to time.
The packed
media bed may increase in biomass as well as entrapped particulates, gasses,
and other materials.
As such, the packed media bed may increase in flow resistance, which may be
measured by a
vacuum sensor located upstream of the pump 1130 or by other mechanisms, such
as the energy
consumed by the pump 1130 to achieve a specific volumetric flow rate.
[0193] A programmable logic controller 1154 may sense that the flow through
the packed
media bed of the bioreactor 1114 may increase past a predefined limit, then
may cause a
backwash operation to be performed.
[0194] In many systems, a backwash indication of one of the bioreactors
1112 and 1114 may
cause the other bioreactor to also undergo a backwash operation.
[0195] The backwash operation of the bioreactor 1114 may involve reversing
the pump 1130
and opening a drain on the weir 1144. By reversing the pump 1130, bioreactor
effluent 1136 may
be reintroduced into the bioreactor I 1 14. Excess water over the level of the
weir 1144 may drain
CA 2969589 2017-06-05
RUSS10-1CA
to the solids removal system 1146. The backflow may cause the water to agitate
and clean the
media 1126, and the resulting water may be captured and sent to the solids
removal system 1146.
[0196] Figure 12A is a diagram illustration of an embodiment 1200 showing a
set of
bioreactors during normal operation. An upflow bioreactor 1202 is shown
upstream from a
downflow bioreactor 1204. Embodiment 1200 may represent one example of the
combination of
upflow and downflow bioreactors illustrated elsewhere in this specification.
101971 Infeed water 1206 may be introduced to the bottom of the upflow
bioreactor 1202
through an infeed pump 1208. The infeed water 1206 may be untreated,
unfiltered water, or may
be concentrated water that may be concentrated by a reverse osmosis system or
other
concentration system. The infeed pump 1208 may be controllable to adjust the
water flow into the
upflow bioreactor 1202.
[0198] An expanded media bed 1210 may have media on which biological agents
may attach
themselves. The biological agents may be bacteria, fungi, yeasts, or other
agents or combination
of agents. The biological agents may consume nutrients in the water steam. as
well as harmful
species, such as selenium, mercury, arsenic, or other materials. The agents
may process soluble
forms of harmful materials into precipitate, such as solid elemental forms of
selenium, for
example. The precipitate may be captured in a packed media bed 1216 or other
filtration
mechanisms. In some cases, the precipitate may be entrained in the biomass of
the expanded
media bed 1210.
[0199] The expanded media bed 1210 may be formed by incoming water flow
that may cross
over an overflow weir 1214 to exit the upflow bioreactor 1202. The water flow
may be selected
such that the media may remain in the upflow bioreactor 1202 during normal
operation, yet may
expand the media bed to have increased contact time with the incoming water.
In many cases, the
flow rates may be between 2 gpm/ft2 and 5 gpm/ft2. In some cases, the flow
rates may be as high
as 6, 7, 8, or 10 gpm/ft2, or as low as 1.5, 1.25, 1.0, or 0.75 gpm/ft2.
[0200] The flow rates may define a retention time of the water in each of
the bioreactors
1202 and 1204, as well as a total retention time for the pair of bioreactors.
In a typical system, the
hydraulic retention time for both bioreactors may be in the range of 15 to 45
minutes. Some
CA 2969589 2017-12-04
RUSSIO-1CA
41
systems may be in the range of 20 to 40 minutes, while other systems may be in
the range of 25 to
35 minutes. In general, the longer the retention time, the more biomass may be
created and the
more cleaning may occur. Empty bed contact time may reflect the time that
water is in contact
with the reactive beds. In a typical design, the empty bed retention times may
be several minutes
more than the hydraulic retention times.
[0201] The two bioreactors 1202 and 1204 may have different retention
times. In some
systems, the downflow bioreactor may have bed contact times that are
substantially the same as
the upflow bioreactor, while in other systems, the downflow bioreactor may
have 1.25, 1.5, 1.75,
2.0, 2.5, 3.0, 4.0 times the bed contact time as the upflow bioreactor. Still
other systems may have
more than 4 times the bed contact time in the downflow bioreactor as the
upflow bioreactor.
[0202] A sonar sensor 1226 may be able to measure the height of the
expanded media bed
1210 during operation. Other types of sensors may also be used to detect the
media bed height,
including optical switches, turbidity probes, and other sensors. In some
cases, the top of the media
bed may be maintained some distance below the water height 1212, while in
other cases, the
media bed may be permitted to reach to the water height 1212.
[0203] The sonar sensor 1226 may be used to adjust the incoming flow rate
of the infeed
water 1206 by adjusting the speed of the pump 1208. The sonar sensor 1226 may
be used to speed
up or slow down the pump 1208 such that the top of the media bed 1210
maintains a
predetermined level. In some cases, the sonar sensor 1226 may be used to
measure the bottom of
the media bed 1210 and a programmable logic controller may adjust the speed of
the pump 1208
to maintain a predefined bottom level of the media bed 1210.
[0204] Partially treated water from the upflow bioreactor 1202 may cascade
into the
downflow bioreactor 1204 across the overflow weir 1214. In many cases, the
overflow weir 1214
may be a wall that may separate the two bioreactors. The downflow bioreactor
1204 may have a
screen 1238 or other device that may prevent media from being drawn into the
pump 1220 and
into the treated effluent 1222.
[0205] An outflow pump 1220 may draw water out of the downflow bioreactor
1204 to
generate treated effluent 1222. The outflow pump 1220 may pull water, creating
a negative
CA 2969589 2017-06-05
RUSSIO-ICA
42
pressure across the packed media bed 1216. A pressure or vacuum sensor 1224 on
the line
between the bioreactor 1204 and the pump 1220 may measure the amount of
negative pressure
that the pump 1220 may be creating.
[0206] The pump 1220 may be controlled through a programmable logic
controller or other
device to maintain the water height 1218 at a predefined level. A water height
sensor 1228 may be
an input to such a controller, and the controller may increase the speed of
the pump 1220 when
the water height 1218 may rise, or may decrease the speed of the pump 1220
when the water
height 1218 may drop.
[0207] The negative pressure measured on the pressure sensor 1224 may be an
indicator of a
backwash operation. As the packed media bed 1216 may entrain gasses,
precipitates, and as
biomass may increase, the resistance to downward flow may increase. At a
predefined level, a
programmable logic controller may identify that a backflush operation may be
appropriate.
[0208] The bioreactor 1204 may have a flushing weir 1234, which may drain
to a solids
removal system 1236. In many cases, such a drain may be gravity fed, although
some cases may
have a pump for assisting the flow.
[0209] The media bed 1216 may be supported by a screen 1238, or other media
retention
device, which could include an underdrain.
[0210] The bioreactor 1204 may operate at a flow rate of 2.5 to 3.5
gpm/ft2. In other cases,
the down flow bioreactor 1204 may operate at a flow rate between 2 and 4
gpm/ft2, 1 and 5
gpm/ft2, or over 5 gpm/ft2. In many case, the bioreactor 1204 may operate at a
lower flow rate
than the bioreactor 1202. Such a design may permit higher contact time in the
second bioreactor
than the first bioreactor in some cases.
[0211] Figure 12B is a diagram illustration of an embodiment 1240 showing a
backwash
operation for both upflow bioreactor 1202 and downflow bioreactor 1204.
[0212] During a backflush operation for upflow bioreactor 1202, the
feedwater pump 1208
may pump untreated infeed water 1206 into the bioreactor 1202 from the bottom.
A valve 1246
may be configured to direct water from the pump 1208 into the bioreactor 1202,
and may also be
CA 2969589 2017-06-05
RUSS10-1CA
43
configured to drain the bioreactor 1202 into the solids removal system 1261.
During a backflush
operation, a pump or valve attached to the weir 1230 may draw water into the
solids removal
system 1232.
[0213] A backflush operation of the upflow bioreactor 1202 may draw down
the water level
to the level of the weir 1230, then may pump feed water into the bottom of the
bioreactor 1202. In
some cases, a pressurized air injector may be used for air scouring of the
bioreactor 1202. A filter
screen 1252 may prevent media and other large objects from being lost into the
weir 1230.
[0214] The clean water may be pumped in at 120% to 200% of the normal
operating flow
rates. The speeds may be selected such that the media bed 1248 may be
agitated, abraded, or
otherwise cleaned. In many cases, the speeds may be selected to encourage
turbulent flow, rather
than plug flow as in normal operation. Any precipitate, excess biomass, or
other solids may be
collected in the weir 1230 and processed by the solids removal system 1261.
[0215] The downflow bioreactor 1204 may be backwashed by reversing the pump
1220
which may pump treated effluent 1222 into the bottom of the bioreactor 1204. A
valve 1256 may
be configured to direct water from the pump 1254 into the bioreactor 1204, or
may be configured
to drain the bioreactor 1204 into the solids removal system 1261.
[0216] During a backwash operation, the weir 1234 may be opened to drain
excess water
into the solids removal system 1236. In many cases, a filter screen 1258 may
prevent media and
other objects from being lost in the weir 1234.
[0217] The backwash operation may be performed at flow rates of 12 to 15
gpm/ft2 which
may be selected to clean the media bed 1256. The cleaning operation may remove
entrapped
gasses, and dislodge precipitates as well as excess biomass from the media bed
1256. The solids
may be captured by the weir 1234 and processed by the solids removal system
1261. Some
systems may include an injector for compressed air 1260 which may provide an
air scour of the
bioreactor 1204.
[0218] Figure 12C is a diagram illustration of an embodiment 1262 showing
an upflow
bioreactor 1202 and downflow bioreactor 1204 undergoing a deconcentrator
operation. The
CA 2969589 2017-06-05
RUSSIO-1CA
44
deconcentrator operation may be performed when shutting down a set of
bioreactors, such as
when power may be interrupted or during normal servicing.
[0219] A deconcentrator operation may flush the bioreactors with clean
water to reduce the
concentration of sealants in the bioreactors. In many cases, especially when
treated water
concentrated by reverse osmosis where anti-scalants are injected beforehand,
superconcentrated
amounts of sealants may be present in the water. If the water flow may be
inadvertently stopped,
the sealants may come out of solution and harden inside the bioreactors. The
deconcentrator
operation may reduce the concentration of sealants to ensure that the
bioreactors may be restarted
easily without fouling.
[0220] A deconcentrator operation may cause clean water 1242 to be
introduced into the
bottom of the downflow bioreactor 1204. The clean water 1242 may be clean
water or permeate
from an upstream reverse osmosis system, or may be bioreactor effluent that
may have been
diluted with clean water. In some cases, a deconcentrator operation may begin
by backwashing
with bioreactor effluent, which may drain diluted bioreactor effluent into the
piping. From Figure
11, an example of treated water from the bioreactors may be the bioreactor
effluent 1136, while
an example of diluted water may be the water in mixing tank 1118.
[0221] During deconcentration, the media bed 1264 may be expanded to
deconcentrate any
sealants in the media bed 1264, and the water may overflow the overflow weir
1214 back into the
normally upflow bioreactor 1202.
[0222] The valve 1246 at the bottom of the upflow bioreactor 1202 may be
configured to
drain into the solids removal system 1261, and the excess water from the
bioreactor 1204 may
flush or deconcentrate the water in the bioreactor 1202. The water height 1270
may drop as the
valve 1246 may be opened.
[0223] In some systems, the valve 1246 may be configured to allow excess
water to drain
back into the feed water source. Such a configuration may be possible when the
feed water source
may be physically lower than the bioreactor 1202.
CA 2969589 2017-06-05
RUSSIO-ICA
[0224] The deconcentrator operation may be configured as a fail safe
configuration. In such a
configuration, a tank of clean water 1242 may be located physically above the
water height 1266,
which may cause the inflow of water to be performed by gravity. The pump 1220
may be capable
of allowing the gravity-fed water to pass by the pump, and the valve 1256 may
be configured in a
normally-open fashion to automatically switch to permit flow for the
deconcentrator operation.
Similarly, the valve 1246 may be configured in a normally open fashion to
drain the bioreactor
1202. Such a configuration may cause the deconcentrator operation to be
automatically performed
when power may be lost.
[0225] When a deconcentrator operation is performed under power, the flow
rates of water
entering the downstream bioreactor 1204 may be similar to the flow rates for
normal back
flushing operation.
[0226] In some cases, a fail safe deconcentrator operation may be performed
using battery
backup or an alternative power source. In such a case, the deconcentrator
operation may be
initiated by a programmable logic controller when a power disruption may be
detected, and valve
operations, pump operations, or other operations may be powered using battery
backup or an
alternative power source.
[0227] Figure 13 is a flowchart diagram of an embodiment 1300 showing a
method for
operating a dual bioreactor system, such as the system of embodiment 1200 and
others in this
specification.
[0228] The system may be configured for operation in block 1302 and normal
operation may
begin in block 1304. During normal operation, a programmable logic controller
or other controller
may check various sensors to determine when a backwash condition may be met in
block 1306. If
the conditions are met for a backwash in block 1306, a backwash operation may
be performed in
block 1308.
[0229] If the backwash conditions are not met in block 1306, a check may be
made in block
1310 for a deconcentrator condition. A deconcentrator condition may be a power
failure, or in
some cases, may be a condition where a train of bioreactors may be taken
offline for some
purpose, including regular maintenance.
CA 2969589 2017-06-05
RUSS1O-ICA
46
[0230] The deconcentrator operation involve both bioreactors, both of which
may be have
operations happening in parallel.
[0231] The upflow bioreactor sequence may begin in block 1312, where the
infeed pump
may be stopped in block 1314 and any infeed valves may be closed in block
1316. A drain from
the bioreactor may be opened in block 1318 to drain the bioreactor contents to
a solids handling
system. In some cases, the drain may allow water from the bioreactor to drain
back into the water
source.
[0232] The downflow bioreactor sequence may begin in block 1320, where the
outflow
pump may be stopped in block 1322 as well as any outflow valve 1324. A clean
water flush valve
may be opened in block 1326 to cause clean water to feed into the downflow
bioreactor.
[0233] When configured in this state, the system may flush in block 1328,
where the
incoming clean water may deconcentrate the downflow bioreactor, and the
overflow from the
downflow bioreactor may spill into the upflow bioreactor to deconcentrate the
upflow bioreactor.
The result may be deconcentrated conditions in both bioreactors. When the
system is ready for
resuming operations in block 1330, the process may resume at 1304.
[0234] Figure 14 is a flowchart illustration of an embodiment 1400 showing
a backwash
sequence, which may be similar to the backwash sequence of block 1308 in
embodiment 1300.
[0235] A backwash sequence may be similar to a flush sequence. In a
backwash sequence,
the bioreactors are agitated and, in some cases, scoured to dislodge and
remove solids. A flush
sequence may be similar, but may be performed to release gases that may be
entrapped in a
bioreactor's media bed.
[0236] 1 he operations of an upflow bioreactor 1402 may be shown in the
center column,
while the operations of a downflow bioreactor 1404 may be shown in the right
hand column.
[0237] The backwash sequence may begin in block 1406. The operations of the
upflow
bioreactor 1402 and downflow bioreactor 1404 may be performed in parallel. In
a typical use
case, the backflush operations of the two bioreactors may be performed
independently.
CA 2969589 2017-06-05
RUSS1O-ICA
47
[0238] The upflow bioreactor 1402 may stop incoming water flow in block
1408. A flush
weir may be opened in block 1412.
[0239] The feed water pump may be started in block 1416 and water may be
introduced to
clean the media bed. In some cases, the feed water pump may be set to a higher
than normal flow
rate. This may cause the media bed to discharge gases, as well as agitate and
remove excess
biomass and solids from the media bed.
[0240] In some cases, an air scour system may be activated in block 1418 to
help
mechanically scrub the bioreactor and the media bed. A typical air scour may
be performed for a
relatively short period of time compared to the backwash water flow because an
upflow bioreactor
may be normally operated in an anaerobic condition, which may be somewhat
upset by the air
scour operation.
[0241] The backflush may operate until the end of cycle in block 1420,
after which the feed
water pump may be stopped in block 1422 and the feed water valve closed in
block 1424. The
flush weir may be closed in block 1426, which may end the backwash cycle for
the upflow
bioreactor 1402.
[0242] The downflow bioreactor 1404 may begin a backwash cycle by stopping
the outflow
pump in block 1428, opening a flush weir in block 1430, and opening a backwash
valve in block
1432.
[0243] A backwash pump may be started in block 1434. In some cases, an air
scour
operation may be performed in block 1436. The backflush operation may continue
in block 1438
until an end of cycle timeout or other indicator occurs. The backwash pump may
be turned off in
block 1440 and a backwash valve may be closed in block 1442. The flush weir
may be closed in
block 1444, and the backwash of the downflow bioreactor 1404 may be complete.
When both
backwash operations have completed, the backwash sequence may end in block
1446.
[0244] Example 1:
[0245] An industrial water treatment system was constructed for treating
mine water runoff.
The system capacity was 500 gallons per minute.
CA 2969589 2017-06-05
RUSSIO-1CA
48
[0246] This system had two trains each of ultrafiltration and reverse
osmosis filtering, which
fed three bioreactor trains. The incoming raw water had up to 800 PPB of
dissolved selenium. The
concentrate sent to the bioreactors contained up to 3200 PPB of dissolved
selenium, and the
bioreactor effluent produced on average less than 64 PPB. The finished water
contained less than
16 PPB of dissolved selenium.
[0247] Example 2:
[0248] An industrial water treatment system was constructed for treating
mine water runoff.
The system capacity was 2000 gallons per minute.
[0249] This system had six trains each of ultrafiltration and reverse
osmosis filtering, which
fed six bioreactor trains. The incoming raw water had up to 300 PPB of
dissolved selenium. The
concentrate sent to the bioreactors contained up to 1200 PPB of dissolved
selenium, and the
bioreactor effluent produced an average of less than 20 PPB. The finished
water contained less
than 5 PPB of dissolved selenium.
[0250] All references to gallons in this specification refer to US gallons.
[0251] When elements are referred to as being "connected" or "coupled," the
elements can
be directly connected or coupled together or one or more intervening elements
may also be
present. In contrast, when elements are referred to as being "directly
connected" or "directly
coupled," there are no intervening elements present.
[0252] In the specification and claims, references to "a processor" include
multiple
processors. In some cases, a process that may be performed by "a processor"
may be actually
performed by multiple processors on the same device or on different devices.
For the purposes of
this specification and claims, any reference to "a processor" shall include
multiple processors,
which may be on the same device or different devices, unless expressly
specified otherwise.
[0253] When elements are referred to as being "connected" or "coupled," the
elements can
be directly connected or coupled together or one or more intervening elements
may also be
present. In contrast, when elements are referred to as being "directly
connected" or "directly
coupled," there are no intervening elements present.
CA 2969589 2017-06-05
RUSSIO-ICA
49
[0254] The subject matter may be embodied as devices, systems, methods,
and/or computer
program products. Accordingly, some or all of the subject matter may be
embodied in hardware
and/or in software (including firmware, resident software, micro-code, state
machines, gate
arrays, etc.) Furthermore, the subject matter may take the form of a computer
program product on
a computer-usable or computer-readable storage medium having computer-usable
or computer-
readable program code embodied in the medium for use by or in connection with
an instruction
execution system. In the context of this document, a computer-usable or
computer-readable
medium may be any medium that can contain, store, communicate, propagate, or
transport the
program for use by or in connection with the instruction execution system,
apparatus, or device.
[0255] The computer-usable or computer-readable medium may be, for example
but not
limited to, an electronic, magnetic, optical, electromagnetic, infrared, or
semiconductor system,
apparatus, device, or propagation medium. By way of example, and not
limitation, computer
readable media may comprise computer storage media and communication media.
[0256] Computer storage media includes volatile and nonvolatile, removable
and non-
removable media implemented in any method or technology for storage of
information such as
computer readable instructions, data structures, program modules or other
data. Computer storage
media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other
memory
technology, CD-ROM, digital versatile disks (DVD) or other optical storage,
magnetic cassettes,
magnetic tape, magnetic disk storage or other magnetic storage devices, or any
other medium
which can be used to store the desired information and which can accessed by
an instruction
execution system. Note that the computer-usable or computer-readable medium
could be paper or
another suitable medium upon which the program is printed, as the program can
be electronically
captured, via, for instance, optical scanning of the paper or other medium,
then compiled,
interpreted, of otherwise processed in a suitable form.
[0257] The foregoing description of the subject matter has been presented
for purposes of
illustration and description. It is not intended to be exhaustive or to limit
the subject matter to the
precise form disclosed, and other modifications and variations may be possible
in light of the
above teachings. The embodiment was chosen and described in order to best
explain the
CA 2969589 2017-06-05
RUSSIO-ICA
principles of the invention and its practical application to thereby enable
others skilled in the art to
best utilize the invention in various embodiments and various modifications as
are suited to the
particular use contemplated. It is intended that the appended claims be
construed to include other
alternative embodiments except insofar as limited by the prior art.
[0258] To the extent that the appended claims have been drafted without
multiple
dependencies, this has been done only to accommodate formal requirements in
jurisdictions which
do not allow such multiple dependencies. It should be noted that all possible
combinations of
features which would be implied by rendering the claims multiply dependent are
explicitly
envisaged and should be considered part of the invention.
CA 2969589 2017-06-05
