Note: Descriptions are shown in the official language in which they were submitted.
A SYSTEM AND METHOD FOR TREATING WATER SYSTEMS WITH
HIGH VOLTAGE DISCHARGE AND OZONE
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application Serial
Nos. 61/983,678 and 61/983,685, both filed on April 24, 2014, and U.S.
Application Serial No. 14/695,519 filed April 24, 2015.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] This invention relates to a system and method for treating flowing
water systems using a high voltage discharge to generate plasma and using the
ozone by-product from the high voltage generation for enhanced treatment of
the
water. The system and method of the invention are particularly useful in
treating
cooling tower or other recirculating or closed-loop systems.
2. Description of Related Art
[0002] Anthropogenic water systems are critical components commonly
found in most of the world's energy producing facilities, industrial and
manufacturing plants, hospitals, and other institutional complexes and
buildings.
These systems consume around 700 billion gallons of water annually with a cost
of $1.8 billion in make-up water and sewage handling costs alone. All of these
anthropogenic water systems require some form of treatment, either chemical or
non-chemical, to control the build-up of scale, biofilm and other corrosion by-
products on the important heat transfer surfaces that are necessary for
efficient
system operation.
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[0003] For water systems involving heat exchange, such as cooling
towers and boilers, effective treatment to remove these contaminants and to
prolong the amount of time before the systems are re-contaminated can save
significant amounts of money. An effective and thorough treatment may save
costs for labor and treatment chemicals by reducing the frequency of periodic
treatments or reducing the amount of chemicals needed for routine maintenance
and/or periodic treatments. Such a treatment may also save on energy costs
through the operation of clean heat exchange surfaces. Fouling of heat
exchange surfaces costs U.S. industry hundreds of millions of dollars every
year
and is directly related to an increase in energy consumption of almost 3
quadrillion Btus (quads) annually.
[0004] To maximize the water usage and minimize waste, many of these
systems employ a series of chemical treatments that protect the system against
scaling, biofilm formation, and corrosion. These chemical treatments allow the
water to be reused and recycled a number of times before it becomes necessary
to discharge the water and replace it with fresh water. Increasing the
duration for
which the water may be circulated significantly reduces the amount of water
that
is discharged to the sewage system and minimizes the amount of make-up water
that is needed to replace the bleed off. However, many chemical treatment
compositions and methods may damage the components of the water system
being treated as the chemicals used are highly corrosive. There is also an
environmental down side to harsh chemical treatments, including growing
concern over the formation of toxic disinfection-by-products such as
trihalomethanes, haloacetonitriles, and halophenols that have been identified
in
the discharge water being released into the environment. It is estimated that
there are 536 billion pounds of water treatment chemicals discharged annually
as
a result of cooling tower treatments, which may impact a variety of species
living
in or near areas and water-ways receiving the discharge or bacterial
components
of sewage treatment plants receiving the discharge.
[0005] In an attempt to minimize the environmental impact associated
with some chemical treatments, many water treatment companies, and more
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importantly their customers, are looking to use non-chemical based water
treatment technologies to maintain the performance of their systems. There are
currently about 30 non-chemical treatment devices or water conditioning
technologies that are commercially available for use in both commercial and
residential water systems. These systems can be divided into three categories:
(1) Indirect chemical producers that use a benign or safe chemical additive
such
as air or salt to produce the biocide. These systems include ozone generators
and electrochemical hypochlorite generators and mixed oxidant generators. (2)
Direct chemical producers that generate the active chemical species from
direct
interaction on the water. These devices use mechanical processes, such as
hydrodynamic cavitation or sonic cavitation, to produce hydroxyl radicals
along
with localized areas of high temperatures and pressures in the water. Other
types of devices that would fit into this category are ultraviolet light
systems. (3)
Electrical and Magnetic devices, including plasma generation, use induced
electrical and magnetic fields to induce ion migration and movement that can
result in cell death through electroporation, or ion cyclotron resonance
effects
within the cell wall. Out of all of these technologies the electrical and
magnetic
devices are the most common; however, they are the technologies that have the
least rigorous scientific support. The direct and indirect chemical approaches
have more scientific credibility; however, this greater understanding may have
limited their potential applications and hence they have not been able to
capture
a larger portion of the market share.
[0006] The application of high voltage discharge and generating plasma
within water is known in the prior art. For example, an article published by
B.R.
Locke at a/. (Ind Eng. Chem Res 2006, 45,882-905) describes electrode
configuration and geometry, the pulsed arc vs. pulsed corona, and the chemical
species that are formed during an electrohydraulic discharge and non-thermal
plasma in water discharge process. The article addresses many of the
fundamental issues related to using this technique for water treatment, but it
fails
to address the practical applications related to water treatment in an
industrial,
commercial, or residential environment, especially related to the need for
multiple
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ground points to minimize the effect of the electromagnetic radiation released
into the water and surrounding atmosphere.
[0007] In a more recent publication Bruggeman eta/ published an
extensive review on non-thermal plasmas in and in contact with liquids in
which
he outlined 14 different reactor configurations that included many of the
electrode
geometries outlined in the article by Locke. (P. Bruggeman, and C. Leys, J.
Phys. D. Appl. Phys, 2009, 1-28). In most of these reactor types the fluid
being
treated by the plasma discharge is a bulk discharge system with no flow (such
as
a bubble corona discharge reactor, discharge reactor with submerged liquid
jet,
electrolysis discharge reactor or capillary needle discharge reactor system);
however, there is also a description of a dielectric barrier discharge (DBD)
reactor where a fluid and air stream are introduced on either side of the of
the
barrier in a bubble discharge reactor. The article notes that even when the
bubbles were not in contact with the electrodes there was a possibility of
generating plasma within the bubbles, and that the sparking voltage of the
system decreases with increased bubble rate. There is no mention of the effect
of bubble size on the spark voltage. Indeed it was also noted that bubbles
when
situated along the surface of an insulator resulted in streamers that were
shaped
and situated along the bubble surface and that the discharge is always
generated
at the triple junction between the electrode, the bubble wall, and the
insulator.
[0008] It is also know to use ozone gas to treat water. For example, in an
article by Gupta etal. (S. B. Gupta, IEEE Transactions on Plasma Science,
2008,
36, 40, 1612-163) the use of an advanced oxidation process resulting from
pulsed discharges in water is described. The process described by Gupta uses
oxygen gas or ozone gas supplied into the discharge reactor from secondary
independent sources (and not from the high voltage generator). They also
report
that system output and performance is highly dependent an solution
conductivity.
For systems where water conductivity can be high, such as in cooling tower and
closed loop applications, higher voltage discharges are needed and this in
turn
creates problems with increased electromagnetic radiation.
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[0009] In order to generate plasma or produce an electrohydraulic
discharge between a high voltage electrode and a ground electrode in water,
especially in a water system where the water chemistry (conductivity, chemical
composition, dissolved solids, planktonic bacterial counts, pH etc.), can
change
over time requires a high voltage power supply that can generate up to and
above over 200 kV potential difference between the two electrodes. One known
system for generating voltages sufficient to generate plasma or produce an
electrohydraulic discharge in water is a Marx generator or a Marx ladder. A
Marx
generator uses a circuit that generates a high voltage pulse by changing a set
of
capacitors in parallel then using a spark gap trigger to suddenly discharge
the
capacitors in series. Typically, the components are supported by a frame
within
a housing containing a pressurized gas. Many of these high voltage generators
are designed with maximum energy density as the ultimate goal and are
designed as such using gasses like SF6 and increased pressure in the spark gap
chamber to facilitate higher breakdown voltages. As a result of these high
breakdown voltages, every time the spark gap is activated there is some
metallic
loss as a portion of the spark gap electrode is vaporized. The vaporized metal
may then be deposited on components of the high voltage generator and after
some accumulation may disrupt the timing of the spark gap discharge. This is
not a problem for high voltage systems that are being run for short periods of
time, such as for use with static water treatment operations; but, for a
system that
is designed to run for months to years at a time, such as for treatment of
flowing
water systems, this is highly problematic.
[0010] There are several prior art patents or published patent applications
that address plasma generation for various purposes, including water treatment
or purification, such as U.S. Patent Application Pub No. 2009/0297409
(generation of flow discharge plasmas at either atmospheric or higher
pressures),
U.S. Patent Application Pub No. 2006/0060464 (generation of plasma in fluids,
in
particular formed within the bubbles generated and contained in an aqueous
medium and describing multiple electrode configurations, including a
configuration to trap the bubbles and have them act as a dielectric barrier to
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increase the voltage across the electrodes), U.S. Patent No. 6,558,638 (using
high voltage discharge to treat liquids, while incorporating a gas delivery
means
for generating bubbles in the discharge zone), and U.S. Patent Application Pub
No. 2010/0219136 (pulsed plasma discharge to treat fluid such as water at a
flow rate of 5 gpm while consuming only 120-150 Watts of power).
[0011] There are also numerous patents disclosing Marx generator
designs. For example, U.S. Patent No. 3,505,533 discloses a Marx generator
coupled with a Blumlein transmission line (a voltage doubling line). The spark
gaps of the Marx are in an enclosed housing filled with a pressurized inert
gas
(CO2 and Argon) and the entire device is submersed in oil. U.S. Patent No.
7,498,697 discloses a Marx generator with a conductive plastic connection
structure that is mounted to an insulating layer for mechanical retention. The
conductive plastic replaces coupling and charging resistors and will have long
term resistance to high voltages.
[0012] The known prior art discloses systems and methods for generating
high voltage discharges to generate plasma to create chemically active
species,
exhibit physical effects, and control water chemistry. However, the known
prior
art does not address the how to apply this technology of using plasma
discharge
to treat larger volumes of flowing water in an industrial, commercial or
residential
setting over longer periods of time without damaging other components of the
water system, including the controllers and monitors that are needed for scale
and corrosion control, blowdown, and water conservation measures.
Additionally, the known prior art does not address use of this technology in
re-
circulating water systems having variable conductivity over time. Finally, the
known prior art does not disclose the capture and use of ozone generated by a
Marx generated as an additional water treatment.
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SUMMARY OF THE INVENTION
[0013] This invention relates to a treatment system and method using
non-chemical technologies to treat flowing water systems, such as cooling
towers
and closed-loop or recirculating water systems. This treatment system and
method involves generating a high frequency and high voltage discharge
between two electrodes submerged in the water being treated. With each
discharge between the electrodes there is a number of long lived oxidative
chemicals (ozone, hydrogen peroxide) and short lived oxidative chemicals
(super
oxides, hydroxyl radicals, and hydrogen radicals) generated, UV radiation is
also
generated, together with sonic shockwaves. These effects are well known in the
prior art and have been used for periodic treatment of static water systems,
but
have not previously been used to effectively treat flowing or re-circulating
water
systems. According to one preferred embodiment of the invention, a treatment
system and method for producing high voltage to generate plasma to treat water
in a flowing or re-circulating water system are provided. The treatment system
and method effectively provide a substantially continuous treatment for water
flowing through a reaction chamber in which plasma is repeatedly generated at
predetermined time intervals over prolonged periods of operation, without
damaging components of the water system.
[0014] According to one preferred embodiment, a treatment system and
method utilize a plasma reaction chamber or reactor unit that enables a long
term
plasma or electrohydraulic discharge to occur in flowing water that can have
changing conductivity, temperature and dissolved solids. One preferred
embodiment of a reactor unit according to the invention comprises a body that
is
capped on both ends with fittings that allow water and optionally gasses to be
introduced and removed from the reactor body, and for electrical connections
to
be made with the high voltage and ground electrodes. According to another
preferred embodiment, a reactor unit comprises an electrode mount assembly
disposed within the reactor unit. An electrode mount assembly preferably
comprises a configuration that reduced choke points with the reactor or plasma
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discharge zone and that funnels gas bubbles into the plasma discharge zone to
aid in plasma generation when the conductivity of the water increases.
[0015] According to another preferred embodiment of the treatment
system and method of the invention, ozone gas produced as a by-product of high
voltage generation is captured and used to enhance the water treatment. In
order to maximize the reaction area for the high voltage discharges in highly
conductive water found in flowing and re-circulating water systems, power
supplies with the capability of generating over 200 kV are preferred. A by-
product in the operation of these power supplies is the production of ozone
gas
that should be removed or it may damage components of the high voltage
generator system, such as the support structure. In this embodiment, that
ozone
is captured and introduced into the water being treated, preferably in a
plasma
reaction chamber, to enhance the water treatment.
[0016] According to yet another preferred embodiment, a gas infusing
system is provided to introduce the ozone by-product or other gases, such as
air
or reactive gases, into the water being treated to further enhance the
treatment.
These gases are preferably added to the water prior to entering a reaction
chamber where plasma generation occurs or are generated in-situ within a
reaction chamber. Preferred embodiments of a gas infusing system include a
microbubbler, a venturi input or venturi injector, hydrodynamic cavitation
system,
sonicating probes, or a combination thereof. A gas infusing system preferably
introduces a fine dispersion of bubbles into the water being treated, which
further
aids in plasma generation because the dielectric breakdown strength of air/gas
is
less than that of water. As the plasma breakdown is initiated in air or gas
molecules, ionized electrons from the air or gas molecules will then carryover
and begin electron ionization in the water molecules.
[0017] According to another preferred embodiment of a treatment system
and method according to the invention, a continuous duty high voltage
generator
is provided. A preferred high voltage generator has a Marx generator or Marx
ladder configuration. A known problem with prior art Marx generators is that
metal from the spark gap electrodes becomes deposited on the sides of the wall
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of the Marx ladder closed support structure and other components of the high
voltage generator system disrupting the timing of the spark gap discharge,
which
would prevent or interfere with the formation of plasma. A preferred
embodiment
of a Marx generator support structure according to the invention comprises an
open frame of increased height and width to increase the distance between the
spark gap electrodes. With the increased spacing between the spark gap
electrodes, metal deposits do not bridge the gap as quickly as with a narrower
support enclosure. According to another preferred embodiment of a Marx
generator support structure, a bottom connecting portion of the frame is
submerged in an oil bath to electrically isolate it from a capacitor bank.
Another
preferred embodiment comprises a support structure that is coated with a
mineral
oil to prevent or inhibit metal deposits from forming on the surfaces of the
support
structure surface and to allow easy removal of any deposit that do form on the
surfaces. According to another preferred embodiment, a support structure is
made from ozone resistant materials, as ozone is known to weaken some
materials which can result in mechanical failure of the support structure.
According to another preferred embodiment, a housing or cover is placed over
the Marx generator support structure to capture ozone for use in enhanced
water
treatment and to facilitate operation of the Marx generator at reduced or
negative
pressure.
[0018] According to another preferred embodiment of the invention, a
system and method for treating water includes one or more control systems
connected to one or more components. According to a preferred embodiment, a
control system times a pulsed high voltage discharge to occur at specific time
increments or intervals to prevent over heating of the water, wiring, or other
critical power supply components of the treatment system and water system.
According to yet another embodiment, a control system comprises a feedback
loop that records the water conductivity, which increases with cycles of re-
circulation, as water flows through the water system and treatment system. As
the conductivity increases, the controller increases the flow of air or other
gases
9
(such a through a gas infusing system) into a reaction chamber to aid in
plasma
discharge.
[0019] According to
another preferred embodiment of the invention,
various protective devices, such as isolated power supply, grounded metal
components, and electromagnetic interference devices, are used throughout the
treatment system and/or water system to protect the components of the water
system from excess voltage produced. According to
another preferred
embodiment, excess energy produced by the high voltage discharge (which is
normally wasted) is captured to further condition and treat the water. Current
is
allowed to flow through wire loops connecting water system piping to a ground
to
generate a magnetic field in the water. This magnetic field has been shown to
have a beneficial effect in water treatment and avoids the damaging effects of
the
large amounts of electromagnetic radiation throughout the entire water system
have on the electronic control systems used to measure conductivity, pH,
biological activity, as well as to control pumps and other critical system
components that are typically found with systems that directly generate a high
voltage discharge into a water supply. The use of a high voltage discharge
without having multiple ground points or other protective device in the water
or
adequate shielding around the high voltage components severely limits the
applicability of the existing prior art.
[0019a] In accordance with an aspect of an embodiment, there is
provided a treatment system for treating water in a flowing water system with
a
plasma discharge, the treatment system comprising: a high voltage generator
comprising a plurality of capacitors, resistors, and spark gap electrodes
configured
in a Marx ladder circuit, a support structure for the spark gap electrodes,
and a
housing; a reaction chamber comprising an inlet configured to receive at least
a
portion of water flowing through the water system as water to be treated, an
outlet
configured to return the portion of water back to the water system after being
treated with the plasma discharge, and a reactor body; a gas infusion system
disposed upstream of the inlet or within the reaction chamber to add bubbles
of
one or more gases into the water to be treated; a high voltage electrode and a
ground electrode at least partially disposed in the reaction chamber and
configured to generate the plasma discharge within the water in the reactor
body
when a high voltage pulse is produced by the high voltage generator; an
electrode
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mounting assembly disposed within the reaction chamber, the electrode mounting
assembly configured to hold the high voltage electrode and the ground
electrode
within the reactor body; and wherein at least a part of the high voltage
electrode is
configured to contact the water in the reactor body while the high voltage
pulse is
transmitted from the high voltage generator.
[0019b] In accordance with another aspect of an embodiment, there is
provided a method of treating a flowing water stream, the method comprising:
generating a high voltage pulse and ozone using a Marx ladder circuit
comprising
a plurality of capacitors, resistors, and spark gap switches, wherein the
spark gap
switches are supported by an open support structure; supplying the high
voltage
pulse to a high voltage electrode, wherein the high voltage electrode and a
ground
electrode are at least partially disposed in water from the flowing water
stream;
generating a plasma discharge in the water between the high voltage electrode
and the ground electrodes; and one or more of: (a) contacting at least a
portion
of the support structure with oil to reduce metal deposits on the support
structure;
(b) supplying the ozone generated by the Marx ladder circuit to the flowing
water
stream upstream of the high voltage electrode or between the high voltage
electrode and the ground electrode; (c) supplying a gas other than ozone to
the
flowing water stream upstream of the high voltage electrode or between the
high
voltage electrode and the ground electrode; or (d) operating the Marx ladder
circuit at a pressure less than one atmosphere.
[0020] Treatment
systems and methods according to the invention
effectively remove biofilm and algae along with other deposits from the water
in
the water system without requiring the use of harsh chemicals and without
damaging components of the water system. The treatment systems and methods
of the invention are also more effective than prior art treatments since
substantial
deposits and algae were observed being released from water systems treated
according to the invention even when the water flowing through the water
system
was considered to be clean (based on prior chemical treatment or because it
primarily consisted of new water from a municipal supply). When the treatments
according to the invention are used, increased copper corrosion rates are also
observed, which indicates that the heat exchanger tubes are being effectively
cleaned of biofilm growth and other deposits resulting in increased heat
exchange
efficiency.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The apparatus of the invention is further described and explained
in relation to the following drawings wherein:
FIG. 1 is a schematic view of one preferred embodiment of a system
according to the invention;
FIGS. 2A and 2B are graphs showing electromagnetic fields measured in
one experiment when an embodiment of the invention was not applied;
FIG. 3 is a graph showing electromagnetic fields measured in another
experiment using a preferred embodiment of the invention;
FIG. 4 is a schematic view of another preferred embodiment of a system
according to the invention;
FIG. 5 is a schematic view of another preferred embodiment of a system
according to the invention;
FIG. 6 is a front elevation view of a preferred embodiment of a reaction
chamber and electrode mount assembly according to the invention;
FIG. 7 is a front elevation of an alternate preferred embodiment of the
electrode mount assembly and ground electrode of FIG. 6;
FIG. 8 is a bottom perspective view of a preferred embodiment of a high
voltage mounting base according to the invention;
FIG. 9A is a bottom perspective view of another preferred embodiment of
a high voltage mounting base according to the invention;
FIG. 9B is a top plan view of the high voltage mounting base of FIG. 9A;
FIG. 10 is a top perspective view of a preferred embodiment of a ground
electrode mounting base according to the invention;
FIG. 11 is a bottom perspective view of the ground electrode mounting
base of FIG. 9;
FIG. 12 is a front elevation view of the ground electrode mounting base of
FIG. 9;
FIG. 13 is a bottom plan view of the ground electrode mounting base of
FIG. 9;
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FIG. 14 is a bottom perspective view of another preferred embodiment of
a ground electrode mounting base according to the invention;
FIG. 15 is a perspective view of a preferred embodiment of a Marx ladder
support structure according to the invention;
FIG. 16 is a top plan view of the Marx ladder support structure of FIG. 15;
FIG. 17 is a side elevation view of the Marx ladder support structure of
FIG. 15;
FIG. 18 is another perspective view of the Marx ladder support structure of
FIG. 15;
FIG. 19 is a cross sectional, front elevation view of a preferred
embodiment of a high voltage generator system, showing an outer housing,
spark gap chamber, and Marx ladder support structure;
FIG. 20 is a top plan view of a portion of the high voltage generator
system of FIG. 19;
HG. 21 is a perspective view of a portion of the high voltage generator
system of FIG. 19;
FIG. 22 is a circuit layout for the Marx ladder of FIG. 15.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] A preferred embodiment of a treatment system according to the
invention is depicted in FIG. 1. Treatment system 10 preferably comprises a
gas
infusing system 28, a plasma reaction chamber 36, a high voltage generator
system 40, power system 46, and various component protection devices.
Treatment system 10 is easily added to an existing water system 12. Water
system 12 can be any residential, commercial or industrial water system,
particularly those used for cooling applications and recirculated water
systems,
such as cooling towers, Water system 12 includes well known components that
are not depicted in FIG. 1. A water stream 14 from the water system 12 being
treated passes through various sensors 16 commonly used in monitoring water
systems, such as pH sensors, temperature, and conductivity. Depending on the
size of the water system 12 and volume of water flowing through the water
system 12, all of the water in the system may pass through the treatment
system
or only a portion or side stream may pass through treatment system 10. Most
preferably, treatment system 10 comprises a shut-off valve or diverter to
bypass
the treatment system, such as when the treatment system is shut-down for
maintenance, without having to also shut-down or reduce flow of water through
the water system
[0023] Water stream 18 preferably flows through gas infusing system 28,
which infuses water stream 18 with fine bubbles of air and/or gas. Preferably,
gas infusing system 28 comprises one or more micro-bubbler devices 20, where
air or gas 22, reactive gas 26, and/or ozone 30 are introduced into the water
stream as fine bubbles upstream of plasma reaction chamber 36. Reactive
gases, such as ozone, mono-atomic oxygen, meta-stable singlet delta oxygen,
vapor phase hydrogen dioxide, chlorine gas, chlorine dioxide gas, may also be
used to achieve maximum removal of microbiological species from water system
12. The use and selection of such gases will depend on water conditions within
water system 12. It is not required to add air, ozone, or other gas streams to
water stream 18, or that such be added as micro-bubbles, but the micro-bubbles
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aid in plasma generation and the ozone gas or reactive gas also serve to treat
the water of the water system. If bubbles are added, stream 24, infused with
bubbles feeds plasma reaction chamber 36, otherwise stream 18 feeds plasma
reaction chamber 36.
[0024] In another preferred embodiment gas infusing system 28
comprises a venturi system for infusing a fine bubble dispersion of air/gas,
reactive gas, and/or ozone into water stream 18 to produce water stream 24.
The venturi input is located upstream of the high voltage reaction chamber 36
and introduces micro-bubbles of one or more of these gases into the high
voltage
discharge area within the reaction chamber 36. In another preferred embodiment
the micro-bubbles are generated by incorporating a hydrodynamic cavitation
system that introduces a highly dispersed suspension of micro-bubbles produce
by the hydrodynamic cavitation process into a reaction zone within reaction
chamber 36. In a fourth preferred embodiment, a venturi system and
hydrodynamic cavitation system are used together. The combination has the
advantage of generating a synergistic environment for optimized reaction
kinetics
and active species generation. In a fifth preferred embodiment, the high
voltage
reaction chamber 36 could be coupled with a plurality of sonicating probes
that
could generate micro-bubbles in situ within a high voltage discharge zone
within
chamber 36, again providing synergistic reaction performance. Finally in a
sixth
preferred embodiment, one or more of these gases could be venturied into the
high voltage reaction zone together with the micro-bubbles being generated by
the sonicating probes. The introduction of micro-bubbles using any of these
systems or devices or any combination of these systems and devices, the
components and applications of which are well known in the art, further aid in
plasma generation because the dielectric breakdown strength of air or gas is
less
than that of water. As the plasma breakdown is initiated in the air or other
gas
molecules, ionized electrons from the air or other gas will then carryover and
begin electron ionization in the water molecules.
[0025] According to another preferred embodiment, one or more
components of a gas infusing system 28 are connected to a controller (which
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may be a controller for the water system or a separate controller for the
treatment
system). The controller operates to increase the flow of air or other gases
into
reaction chamber 36 in response to increased measurements of conductivity in
the water (which is typically measured as part of the water system control
functionality). The increased air flow aids in ensuring that a plasma
discharge
occurs even when the conductivity of the water is high.
[0026] Reaction chamber 36 preferably comprises a sealed, water-tight
housing 35 surrounded and shielded by an inner dielectric barrier layer 34a
and
outer ground shield 34b. The dielectric barrier 34a is a non-conductive layer
that
prevents arcing to the ground layer 34b, which is a conductive outer layer
tied to
the ground. The dielectric barrier 34a and ground shield 34b reduce
electromagnetic interferences radiating from the reaction chamber 36. If
reaction
chamber 36 is not shielded, sensitive electronic equipment may be damaged by
the plasma generated within the chamber 36. Within reaction chamber 36 are
disposed a high voltage electrode and a ground electrode which generate a
plasma discharge within chamber 36 as voltage generated in high voltage
generator system 40 is transmitted to the high voltage electrode within
chamber
36. These components for generating a plasma discharge are well known to
those of ordinary skill in the art. The shape and configuration of reaction
chamber 36, housing 35, and the high voltage and ground electrodes within
reaction chamber 36 are not critical and any known shape and configuration may
be used, although a preferred embodiment of an electrode mount assembly and
reaction chamber as shown in FIGS. 6-7 and discussed below is most preferably
used. Another ground 48 is also disposed in contact with ground layer 34b
surrounding housing 35, which is needed to generate the plasma discharge in
reaction chamber 36. Ground 48 may act as a ground electrode or may be
connected to a thicker rod or other conductor to act as the ground electrode.
A
highly insulated high voltage wire 38 connects the high voltage generator
system
40 with the high voltage electrode in reaction chamber 36. Wire 38 is
preferably
insulated with a high strength dielectric to prevent arcing to other
electronic
devices, metal structures, or people/operators. Wire 38 may act as the high
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voltage electrode or may be connected to a thicker rod or other conductor to
act
as the electrode. Treated water stream 60 exits the reaction chamber 36 and
returns to sump 54 (particularly where water system 12 is a cooling tower) or
other components or piping of water system 12 to be recirculated through the
system. Inlet and outlet couplings for water streams 24 and 50 into and out of
chamber 36 should be grounded.
[00271 High voltage generator system 40 may generate a high frequency,
high voltage pulse that exceeds 200 kV on each discharge step. The high
voltage generator system 40 preferably comprises a Marx ladder or Marx
generator 42 disposed within a spark gap chamber 41 within an outer housing 43
(such as in the preferred embodiment shown in FIG. 19) that includes a
dielectric
barrier to isolate the Marx ladder 42 from the surrounding environment and
prevent arcing from the internal components to nearby metal structures,
electrical
outlets, and other monitoring and control systems. To be effective in treating
conductive waters similar to those seen in traditional cooling towers or
closed
loop systems, the high voltage generator system 40 is preferably capable of a
voltage output of 200 kV for an electrode gap of around 5 mm between the high
voltage discharge electrode and the ground electrode in the reaction chamber
36. Although other gap distances may be used with modifications that would be
understood by one of ordinary skill in the art, a gap distance of around 5 mm
is
preferred. This is preferred because a larger gap distance requires an
increase
in output voltage, which can introduce additional issues, such as component
failure in the high voltage generator system 40, and a smaller gap distance
reduces the volume of water being exposed to the plasma discharge.
(0028] In one preferred embodiment, the high voltage generator system
40 comprises a stage 1 low voltage component (driver circuit 39, as shown in
FIG. 19 and 22) that takes the 110V output from a typical wall outlet and
generates a 40 kV DC signal. This is achieved by a Zero Volt switching circuit
that pulses the input from a flyback transformer. The number of turns on the
transformer can be increased or decreased to change the output voltage of the
flyback transformer. An advantage of using a Zero Volt Switching driver
circuit is
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that it features a high noise immunity, that is not susceptible to
electromagnetic
interference that is created in pulsed power systems. Digital or other
circuits can
also be used, but they are more sensitive to outside interference generated by
the plasma reaction chamber 36 than a Zero Volt Switching driver. To protect
the electronics from the high voltage output this is constructed as a
separated
shielded entity. The signal from the stage 1 low voltage component (driver
circuit
39) is used to charge a capacitor bank in the Marx generator 42, which has the
capacitors assembled in parallel. When the capacitor bank reaches the
discharge limit, it triggers a cascading discharge event between spark gaps in
a
Marx ladder so as the terminal voltage is greater than 200 kV between the
discharge and ground electrode.
[0029] Air pumps 44 or other devices to pressurize or blow air are
preferably integrated into high voltage generator system 40, but may also be
external to generator 40 and connected with appropriate conduit to permit air
flow
into generator 40. Air pumps 44 blow air through the high voltage generator
system 40 to quench the electrodes of the Marx ladder 42, which aids in
increasing electrode lifetime. Air pumps 44 flush air across the electrodes
and
out of the spark gap chamber 41. Ozone gas 30 generated from the spark gap
chamber 41 is withdrawn from high voltage generator system 40 and preferably
recycled back to be injected or infused into water stream 18 to provide
further
water treatment. Ozone gas generated from the Marx ladder is typically
considered a waste product, but it is beneficially used according to the
invention
as a source of water treatment. Most preferably, the ozone gas 30 is venturied
into water stream 18 at or near an inlet into reaction chamber 36. This
permits
the introduction of ozone (and other components of air, such as nitrogen) into
the
water supply and also aerates the water stream 18 with fine micro-bubbles to
form feed stream 24. The use of the ozone by-product from the high voltage
generator system 40 combined with plasma discharge has been found to be
synergistic and particularly effective in reducing planktonic bacteria in the
water
being treated.
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[0030] Treatment system 10 also comprises a power system 46 and
various protective devices to protect the components of the water system from
excess voltage produced. Power
system 46 preferably comprises an
uninterruptable power supply or isolation transformer, which reduces any
transient voltage spikes from entering the power supply of the building in
which
water system 12 is housed. This also isolates the high voltage generator
system
40 from other electronic components of the building and the water system 12,
such as sensors 16 which have a separate, uninterruptable power supply or
isolation transformer 60. A grounded metal component 56 is preferably placed
in
a water reservoir for the water system 12 (such as sump 54 in the case of a
cooling tower). Grounded metal component 56 is preferably a piece of metal or
mesh with a large surface area, but other shapes and configurations may be
used. This
grounded component reduces or eliminates electromagnetic
interference through the water. Electromagnetic interference suppressors 58
are
preferably connected to or clamped on electronic components of water system
12, particularly any sensors (such as sensors 16) that will be used to monitor
water qualities- such as conductivity, temperature, and pH. Other grounding
devices, such as 52, may be added as necessary to other reservoirs or piping
within water system 12 or connecting water system 12 with treatment system 10.
In one preferred embodiment, grounding device 52 comprises a screw inserted
into a wall of a pipe through which water in the water system is flowing, with
a
length of wire connected at one end to the head of the screw and wrapped
around the pipe several times, with the other end connected to ground. Other
grounding devices or configurations may also be used as will be understood by
those of ordinary skill in the art. Typically, these grounding devices will be
placed
on or near specific types of equipment, such as a corrater (corrosion
monitoring
system), chemical controller, flow controller, conductivity probe, or will be
spaced
out throughout the water system with 2 - 4 devices used in most large water
system applications. These grounding devices serve to protect the components
of water system 12 and also allow the energy from the multiple ground points
to
be harvested and stored in a capacitor or inductor. The harvested and stored
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energy may be used to generate low level energetic fields (electromagnetic or
electrochemical) that provide further benefits to the water treatment process.
Electromagnetic fields have been used to prevent chemical scale formation and
have been used to induce electroporation and ion cyclotron resonance, which
have been shown to have antimicrobial properties. Electrochemical reactions
can generate areas of localized high and low pH and can induce electroporation
as well. They may also generate low level electromagnetic fields locally
within
the water system without storing the energy. For example, with a wrapped wire
device around a pipe in the water system as described above, each time a pulse
(from the plasma) is sinked to ground, a current will flow through the wire
loops
around the pipe to generate a magnetic field in the water flowing through the
pipe
at that location,
[0031] Treatment system 10 also preferably comprises a controller or a
timer in order to activate the treatment system 10 at periodic intervals. A
controller or timer would periodically turn on various components, including
power system 46 to charge the high voltage generator system 40, air pumps 44,
and components of gas infusion system 28, such as microbubbler 20. Once high
voltage is discharged from high voltage generator system 40 to reaction
chamber
36 and a plasma discharge is generated within reactor housing 35, the
components of the treatment system would be shut-off until it is time for the
next
cycle. This activation/deactivation cycle repeats at periodic intervals,
preferably
around 15 minute intervals, over the course of a substantially continuous
treatment cycle lasting several weeks to several months during normal
operations of the water system and treatment system. Periodic
activation/deactivation reduces overall system heating and increases
efficiency.
As the system heats up, more energy will be dissipated in the Marx generator
40,
which results in more charging losses and less energy being available for
plasma
generation within reactor housing 35. Allowing the system to cool during
periodic
deactivation reduces charging losses and increases efficiency. Periodic
activation/deactivation will also allow the ozone from the spark gap chamber
to
be flushed out on a regular basis (and preferably fed into reactor housing to
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enhance the water treatment) and maintain a pulsed arc discharge over the
greater than 5 mm electrode gap between the high voltage electrode and ground
electrode in the reactor housing. In order to operate the system safely it is
preferred to power the system through a switch box 45 that features a ground
fault circuit interrupt. This emergency stop system will trigger if the
current
flowing from the device does not match the current sinking into the device.
[0032] The following are examples wherein a treatment system 10
according to various embodiments of the invention was tested.
[0033] Example 1A. Direct discharge into an unprotected system:
In the first set of experiments, a pilot cooling tower was used. Components of
this experimental system that correspond with the systems depicted in FIG. 1
are
labeled according to the reference numbers in FIG. 1. A cooling tower (total
volume 100 L) water system 12 was charged with water and the system was set
to circulate. The water chemistry was monitored using an Advantage Control
system and biological monitoring as performed using two in-house biological
monitoring systems and a ChemTrak biological monitor. These systems are
typically found or are similar to those typically found in larger scale
commercial or
industrial cooling tower operations. To incorporate the high voltage generator
system into the cooling tower, a side-stream flow (stream 18) was pulled from
the
heat exchanger rack via a mechanical ball valve and 12 feet of 0.75 inch
diameter clear flexible PVC tubing. This valve allows the system to change
flow
dynamics based on the specific composition of the water being treated. For
example, changing the flow rate past the venturi changes how the gas bubbles
are distributed into the water and this in turn can change the form of the
plasma
generated at the high voltage discharge electrode. Also volume and flow rate
are
important in terms of treatment of the entire system water for biological
control
using directed high voltage discharge because successful treatment depends not
only on the amount of energy being delivered, but also the treatment time.
Since
bacteria are constantly replicating in a typical system within a large volume
of
water, it is important to achieve a high enough flow rate through the reaction
chamber 36 in order to ensure that the entire volume of system water is
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repeatedly treated or cycled through the high voltage discharge zone to
increase
total treatment time (the total amount of time a column of water with
biological
constituents in in contact with the high voltage discharge).
[0034] Using this setup on the pilot cooling towers allows for a maximum
of 2 gpm side-stream flow. This tubing was connected to a plasma chamber 36
via a threaded polyethylene barbed fitting. At the outlet of the reaction
chamber,
feet of clear PVC tubing is used to drain the water exiting the reaction
chamber
(stream 50) into the sump 54. None of the grounding points (such as ground 52
and 56) described with respect to a preferred embodiment above was put in
place. The reaction chamber 36 was connected to a high voltage generator
system 40. The unit was activated and a pulsed spark discharge in water with
1,500 pmhos conductivity was observed over a 1 cm electrode gap. Immediately
upon activating the high voltage generator system 40, flow control relays of
water
system 12 began to activate off and on, cutting off power to the water system
12.
The electronics in the Advantage Controller over loaded and shut the system
down and the biomonitor output (located on the other side of the room from the
high voltage generator system 40) overloaded and shut off. Figures 2A and 2B
show the electromagnetic fields measured in the water with the plasma unit on
in
this test embodiment, with water flow and no water flow with the
electromagnetic
fields traveling through the water in both cases. It can be seen that when the
water is flowing (FIG. 2A) there is a high resonance electromagnetic pulse
penetrating the water circulating through the system. It can be seen that even
when the water is not flowing (FIG. 2B) there was still a measurable
electromagnetic field resulting from the high voltage discharge.
[0035] Example 1B. Direct discharge Into a protected system: The
experiment of 1A was repeated, but with a multiple ground protective system in
place. Grounds were placed in a sump 54 and parts of the tubing (using a screw
and wire wrapping as discussed above) throughout system. Figure 3 shows that
there is a significant reduction in the electromagnetic field in the water.
Using the
multiple ground system, it is now possible to run the high voltage discharge
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system for several hours continuously without causing problems to the
electronic
control and monitoring equipment used as part of the water system 12.
[0036] Example 2. Bench Trials for Removal of Microorganisms:
Four bench-level studies were conducted to determine the efficacy of a non-
thermal plasma discharge in water to inactivate microorganisms. It is known
that
a plasma discharge in water will generate active oxygen species, UV radiation,
and pressure field shock waves all of which can inactivate microorganisms. A
plasma discharge can be achieved by increasing the electric field in a
solution
beyond its breakdown voltage. The breakdown voltage is dependent on the
conductivity and the dielectric properties of the solution. It has been
observed
that a relationship exists between the input energy and the log reduction of
the
microorganisms in the system. It has also been documented that the input
energy needed to achieve a one log reduction (known as D-value) in E. coil can
vary from 14 J/L to greater than 366 J/L. As for experiments with certain
species
of pseudomonas, it has been reported that 85 kJ/L is the average input energy
needed to achieve one log reduction.
[0037] In a first experimental set, a rod to cylinder electrode
configuration was placed in a beaker containing 1,600 mL of water (800 mL of
tap water and 800 mL of distilled water). Ozone generated from a Marx
generator (from the non-thermal plasma's voltage multiplier) was aerated into
a
secondary beaker containing 1,600 mL of water (also 800 mL of tap water and
800 mL of distilled water) (beaker #2). For these tests, Escherichia coli (E.
coil)
was utilized because of its high susceptibility to inactivation by directed
energy
methods. For each of the beakers containing 1,600 mL of the described water, 2
mL of a TSB stock solution with a known concentration of suspended E. coil was
used to inoculate each of the water filled beakers for a final E. coil
concentration
of 4.65 x 106cfu/mL (Test #1) and 4,50 x 106 cfu/mL. For the plasma only
beaker
test (beaker #1), the cylinder electrode diameter was increased from a 1/4
inch
(which generated an arc discharge) to a 1 inch size so that a pulsed corona
was
generated during the discharge. A purpose of this test was to determine which
of
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an arc discharge (which puts more energy into the system, which is preferred)
or
a pulsed corona results in the most biological inactivation.
[0038] As for the ozone treatment only beaker, ozone was pushed
through a Marx generator chamber and bubbled into the beaker with the use of
an airstone. During the experiments, 25 mL samples were collected
independently from each beaker at 0 min., 2 min., 4 min., 10 min., 20 min.,
and
30 min. and bioassayed for cfu/mL determination. The results of the pulsed
corona discharge plasma only test are shown in Table 1 below under Test #1.
[0039] A second experiment combined the aerated ozone and a rod to
cylinder electrode setup into a single beaker containing 1,600 mL of water
(800
mL of tap water and 800 nil_ of distilled water) (Test #2). For this test, 2
mL of a
TSB stock solution with a known concentration of suspended E. coil was used to
inoculate the water filled beaker for a final E. col! concentration of 6.10 x
106
cfu/mL. The cylinder electrode diameter 1/4 inch so that a pulsed spark
(pulsed
arc discharge) would be generated in the solution during discharge and the
ozone generated by a Marx generator was bubbled into the beaker beneath the
electrode setup. During the experiment, 25 mL samples were collected at 0
min.,
min., 30 min., 45 min., and 60 min. and bioassayed for cfu/mL determination.
The results are shown in Table 1 below under Test # 2.
[0040] A third experiment featured a rod to cylinder electrode
configuration placed in a beaker containing 1,600 mL of water (800 mL of tap
water and 800 mL of distilled water) (Test #3). Ozone generated from a Marx
generator (from the non-thermal plasma's voltage multiplier) was aerated into
a
secondary beaker containing 1,800 mL of water (again 800 mL of tap water and
800 mL of distilled water). For this study, Escherichia coil (E. coil) was
utilized
because of its high susceptibility to inactivation by directed energy methods.
For
each of the beakers containing 1,600 mL of the described water, 2 mL of a TSB
stock solution with a known concentration of suspended E. coil was used to
inoculate each of the water filled beakers for a final E. coil concentration
of 3.05 x
106 cfu/mL and 3.40 x 106 cfu/mL respectively. Similar to the second
experiment,
the cylinder electrode diameter was lowered so that a pulsed spark (pulsed arc
24
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discharge) would be generated in the solution during discharge. As for the
ozone treatment only beaker, ozone was pushed through the Marx generator
chamber and bubbled into the beaker with the use of an airstone. During the
experiment, 25 mL samples were collected independently from each beaker at 0
min., 10 min., 15 min., 30 min., and 45 min. and bioassayed for cfu/mL
determination. The results are shown in Table 1 under Test #3.
[0041] In a fourth experiment, the aerated ozone was combined with and
a rod to cylinder electrode setup into a single beaker containing 2000, mL
of
water (1,000 mL of tap water and 1,000 mL of distilled water) (Test #4). For
this
test, 5 mL of a TSB stock solution with a known concentration of suspended
Pseudomonas putida was used to inoculate the water filled beaker for a final
Pseudo. putida concentration of 7.00 x 107 cfu/mL. Different from the first
experiment, the cylinder electrode diameter was lowered so that a pulsed spark
(pulsed arc discharge) would be generated in the solution during discharge and
the ozone generated by a Marx generator was bubbled into the beaker beneath
the electrode setup. During the experiment, 25 mL samples were collected at 0
min., 15 min., 30 min., 45 min., and 60 min, and bioassayed for cfu/mL
determination. The results are shown in Tables 1 and 2.
[0042] Table 1 ¨ Summary of Plasma Effectiveness Studies (Bench-Level Testing)
o
N _ Test 11,(E;coli)
Test 2 (E. coli) Test 3 (E. coli) Test 4 (Pseudo..
putida) .
u.
.
= .
Plasma Only Study Plasma + Ozone Study Plasma Only Study
Plasma + Ozone Study
4,
-A
Pulsed Corona Discharge Pulsed Spark (Pulsed Arc) Pulsed Spark
(Pulsed Arc) Pulsed Spark (Pulsed Arc) c,
=
in a beaker with no Ozone Discharge plus Ozone Discharge in a
beaker with Discharge plus Ozone
Treatment no Ozone
Treatment
, - . ,. .. _ , ..- -,-. .7- -..,-
..; . .. - 7 - 7 ' ,... -E'... T.' = : ' :.. --: ,..-1.':-,
-:=-==-2: 5-- Log-.
:'.." Log .....- -=- .... . ...= ..:=-.- -
., .-1_..=g.._,..- - .:,..,..- -. =---.:-, - _- -14 - ,
., :., , ..--,-,.. .,-----.-.. ,
Sample ........ ,. , , --.. _ bample.- . _-.:, - '
, . ,. - --:, . , Sample ..... _ _-. . : :,.....-bampie ,.-
-- .
- Reduction. - , .... - . ,- ' Reduction -
.-- , , -= = L :-Reduction ,.,,L,-_-_;:., .. : Reduction
1
, .. , . . , , ..,,
.. ,
0 min: .: '-r/ -0 inin.... ... r ,.. 0 min.
Icontrol) .,../
A__,.L:,,,,,;(7_,-;fociin:fritio-::
(ContrOl)- (ContrOl)...=
- 6.67.1log'-. 6.19166 .-.'
. idl, .... 6.48 log
_. , , .
.--- Cfki/ML -:- __ A ._ iiiiiii.L-,,_-=:
//1.4 J.. cfu/mL :- A P
2
.
.
.
.
r.)
.
c., 2 min. 0.15 10 min. 1.28 10 min.
2.74 __ 15 min 0.72
0
,
0
4 min. 0.23 __ 30 min. 5.79 15 min.
3.82 30 min. 1.46
min. DAD 45 min. 5.14 30 min.
4.20 45 min. 1.55
30 min. 0.99 60 min. ?6.79
45 min. 4.46 60 min. . 1.85 .0
n
5
=
u.
-a-
N
fl I
4=.
0
o
[0043] Table 2 - Summary of Plasma Effectiveness Studies (Bench-Level Testing)
1,4
=
,--,
u.
,----- _
c,
.r.,
: (Plasma ONLY) Study Using E. coil as ! (Ozone ONLY) Study Using E.
coil as --.1
Target Organism i Target
Organism c,
z>
I
: .... ,...õ.. ..Sa mp I e MEM ' Lag.' Den- 'ty
:':.:-',:"iPµ le : .:Hc....f..!;:9m4; = ..,,I.Oti1-fe.1:kePs
- Co r6t.r-01 : 3 05 6+06 11111P .; . . .. .
...:..õ
:-_oeltecir z , ' 640,6+06 6,63
C. min y--:. - : =-=_- .. 10min
.,.. .. .. . .
.- Pci:M-TN.nra67,Ci 645.6+03 ME :-
P.O.st;Treetrneni. 060E4-06: 6.82
.:,,. , . .:,.:.:. ..,
...._,õ
, ii. '.l..-;,4......,---.%--:,-,-..,
0
"i a :lt.p.:;:.:: ' -:' iS rnin
, - -, .
, .
Post Tmariiiiik:- 4.60.6+02 ::-
..!.4101:Treatment 0306+05 5.80
..
.
mn i . '':" :
2
,
P oat Tre a tatettel 1.90E+02 2.28 ....
0.itiA:Tretine.i.itli: 1.23E+05 5.09
.,
- ' 46l'in-,YiLiN'-',-.t .-.:- --. :_::-,:46r9iiii:-
:;:.:;,:]. ,
F 0 st Ti'll-ft:::', 1,05.6+02 2.02: .-- 0,44,T.ii
.:41.ien-1- v 1.11.+05 6..07 .
i
L .
'
7¨ .....___ . .. .
---
i
; Plasma 4, Ozone Study Using E. coil as i Plasma + Ozone Study Using
Pseudo.
I Target Organism ! putida as Target
Organism
L i
A- - airiPle : - ::1.?i':PF.Virri1: _ , - Lou,
Density i,.!, = - S4motiv-.:,.,..: , cfUltatt _ Lcigiti.periaity :
w
cn
: Control . - 6.10.6+06 , 079 . Conte! _.
, 1,01.61707 . . 7,90,
.
ci)
rain : 15 min
tv
o
. -Post Treatment - 3.26.E405 6.51 Post
Treatment 1.92.6+06 6,20 -
.
u.
-,-:-5
L 30 min 30 Min
--4
FraSt Treatment 10.6+01 1.00 Post Treatment
3.45E+06_ 5.54. !A
.r.,
o
i.. 46 rnin . 45 rain
I = :P.Ost Treatment 450E+01_ 1.65 Post Marne-
FA 2.66.6+06 5.45
1 :
' 60 min- : 60 min
'
[0021] Referring to FIG. 4, a field test was also performed using a
preferred embodiment of the system and method of the invention. The goal
for this field test was to install a plasma water treatment system 110 in a
cooling tower water system 112 that used oxidizing biocides to control the
microbial population in the water. The cooling tower water system 112 had a
total volume of 1,400 gallons and was situated at street level outside the
administrative building of a local University. A control unit 170 that
monitored
water flow and water conductivity was used to control the water system blow
down and chemical feed into the sump 154. This unit maintained water
conductivity between 900 pmhos and 1500 pmhos. The plasma treatment
system 110 comprises a high voltage generator 140 and a plasma reaction
chamber 136. High voltage generator comprises a Marx ladder or Marx
generator 142 disposed within a spark gap chamber 141 within an outer
housing 143 that includes a dielectric barrier. Ozone gas stream 130 is
withdrawn from spark gap chamber 141 and is injected into inlet water stream
114 via a venturi 121. Although not used initially in this test, air 122
and/or
reactive gas 126 could also be injected into the water stream through a micro-
bubbler or similar device 120. A tee, mixer, or similar connecting device 129
may be used to infuse stream 124 (containing ozone) with micro-bubbles of
air and/or reactive gas from micro-bubbler 120 and provide an inlet into
reaction chamber 136. Reaction chamber 136 comprises a sealed, water-
tight housing 135 surrounded and shielded by an inner dielectric barrier layer
134a and outer ground shield 134b. The dielectric barrier 134a is a non-
conductive layer that prevents arcing to the ground layer 134b, which is a
conductive outer layer tied to the ground. Within reaction chamber 136 are
disposed a high voltage electrode and a ground electrode which generate a
plasma discharge within chamber 136 as voltage generated in high voltage
generator 140 is transmitted to the high voltage electrode within chamber 136
via wire 138. Wire 138 may act as the high voltage electrode or may be
connected to a thicker rid or other conductor to act as the electrode. Another
ground 148 is also disposed in contact with ground layer 134b surrounding
housing 135.
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Ground 148 may act as the ground electrode or may be connected to a thicker
rod or other conductor to act as the electrode. Reaction chamber 136 in this
field
test was around 4 inches in diameter. The reaction chamber 136 in this field
test
was plumbed directly into the existing water lines of water system 112. The
reactor inlet 129 was connected to the water line 114 from the high pressure
side
of the pump 113 which was removing the water from the cooling tower sump 154.
A venturi 121 inserted into the line between the pump 113 and the reactor 136
was used to draw ozone gas 130 generated by the Marx ladder 142 into the
water being treated. The treated water 150 exiting the reaction chamber 136
was returned to the output side of the chiller where it circulated back into
the
cooling tower.
[0045] When the system 110 was installed initially, none of the
recommended precautions or protective measures mentioned in reference to
FIG. 1 and treatment system 10 were in place. The system 110 was installed in
close proximity to the water system master control system, it was not
grounded,
there was no shielding of the controller unit and there were no ferrite beads
around the sensors leads for EMI suppression. The high voltage generator 140
was plugged directly into main electrical outlet in the wall.
[0046] To start the process, water stream 114 was introduced into the
reaction chamber 136 and the high voltage system 140 was activated.
Immediately the electromagnetic feedback through the water caused the
conductivity meter on the water system 112 to jump to 6000 pmhos, forcing the
water system 112 into an immediate blow down mode that resulted in water
being dumped to the drain. Without one or more of the protective measures
referenced with system 10 of FIG. 1, it would be impossible to effectively
operate
a high voltage discharge treatment system in a cooling water system.
[0047] The set-up of systems 110 and 112 were then reconfigured with
the water control unit 170 (used to control various components of the water
system 112) being isolated within a housing 172 and by clamping ferrite beads
158 around the wires leading to the conductivity sensor 116. Housing 172
encloses water system control unit 170 during operation of system 110, but
29
comprises an openable door or a removable cover so that the interior may be
accessed for service. Housing 172 is preferably a metal box, but other
shielding materials such as plastics, concrete or metal plastic composites may
also be used. The high voltage generator 140 was moved to the opposite
side of the room from the controller (approximately 12 feet away, and
preferably at least 6 feet away) and the power supply 146 was switched from
directly connected to the mains to being run through a UPS. The sump 154 in
the cooling tower was grounded 156, as was the return (treated) water line
150 grounded by 151. Optionally, ferrite beads 158 may also be wrapped
around treated water line 150. When the system 110 was activated there was
no negative impact on the control system 170 or sensor 116, allowing the
cooling tower system 112 to operate normally.
[0048] Using this set up, the water treatment system 110 was run for 6
months without the addition of biocide. During the process, ozone gas 130
generated in the Marx ladder 142 was introduced into the water entering the
reaction chamber 136. This produced a fine stream of bubbles at the high
voltage electrode surface. When the water had a low conductivity around 900
pmhos this would be sufficient to generate a plasma discharge, but as the
conductivity increased with increasing number of cycles of concentration, this
was no longer adequate to generate a plasma discharge in the reaction
chamber. As the water conductivity increases, parasitic electrochemical
reactions become the favored mechanism for the discharge of the electrons,
and the ability to generate a plasma is diminished. Additional air 122 was
introduced into the reaction chamber that provided a more robust air curtain
between the ground electrode and the high voltage discharge electrode
allowing plasma to be generated in water with conductivity in excess of 1500
pmhos. Once the conductivity reaches a pre-set threshold, usually around
1500 pmhos, the cooling tower or other water system goes into blow down
mode, dumping the high conductivity water to the drain and replacing it with
new water (usually fresh water from a municipal supply, but other water
sources with lower conductivity levels may be used).
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[0049] Referring to FIG. 5, another preferred embodiment of plasma
treatment system 210 was tested in a second field trial. System 210 was
installed to treat a 2,200 gallon stainless steel/galvanized cooling tower
water
system 212. During this installation, the high voltage generator 240 and the
plasma reactor chamber 236 were shielded within a housing 260 and placed
on the outside wall away from the water control unit 170 and sensors 216 of
water system 212. Housing 260 is preferably at least 6 feet away from water
control unit 270 and sensors 216. Housing 260 is preferably made of metal,
but other materials such as plastic or metal plastic composites may also be
used. Housing 260 encloses system 210 during operation, but comprises an
openable door or a removable cover so that the interior may be accessed for
service. When housing 260 is used, it is not necessary to enclose control unit
170 in a housing (such as housing 172 used with system 110), but such a
housing may also be used for added protection of the control unit. The water
214 from the sump 254 was circulated through the plasma reactor using a
pump 213 that was placed directly in to the sump 254 which was grounded
256. The high voltage generator 240 was connected directly to the main
electrical outlet as power supply 246, but the outlet was on its own breaker
circuit. With this set-up, system 210 was able to continuously operate for 6
months (at which time the cooling system was shut-down for winter, but it is
believed the system could have continued operating with this embodiment of
the invention for a longer period if cooling was needed) without any
electrical
or EMI issues interfering with operation of water system 212.
[0050] Any combination of protective measures, such as a grounded
piece of metal or mesh with a large surface area placed within a sump (similar
to 56), electromagnetic interference suppressors (such as 58), grounded wire
wrapped pipe segments or ferrite beads (such as 52 or 158 or 258), a
protective housing (such as 260) around the high voltage generator and
plasma reaction chamber, a protective housing around the water control unit
(such as 172), locating the high voltage supply and reaction chamber a
sufficient distance from the water control unit and sensors, segregated power
supply for the high voltage
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generator (such as an outlet on its own breaker circuit or a UPS or isolation
transformer), and/or segregated power supply for the water control unit or
sensors (such as a separate UPS or isolation transformer) may be used with any
treatment system according to the invention to protect the water system
components from any interference or damage and to permit the treatment system
to operate continuously for extended periods of time. Any
combination of
grounding devices may also be used with any treatment system according to the
invention to harvest (and to store using capacitors or inductors) excess
energy
generated by the treatment system and to generate low level energetic fields
(electromagnetic or electrochemical) that provide further benefits to the
water
treatment process.
[0051] The ability to control pressure drop across a reactor housing within
which a plasma discharge will occur, is important for ensuring sufficient
discharge, especially if ozone, air or other gas is being added to the inlet
water
stream to supplement the dielectric barrier of the high voltage discharge
electrode. Paschen's Law is an equation that describes the break down voltage
necessary to start a discharge between two electrodes as a function of
pressure
and gap length (distance between the high voltage electrode and ground
electrode). In the initiation of a plasma discharge, the first ionization
energy of an
electron must be reached to dislodge and liberate an electron that when
accelerated results in chain reaction electron avalanche as the liberated
electrons collide with the atoms. The higher the pressure of the discharge
medium the more collisions that occur as the electron travels from the
discharge
electrode to the ground, and this randomizes the electron direction, which in
turn
can result in electron deceleration resulting in a failed discharge between
the
electrodes. Because water can be viewed as a highly condensed gas, pressure
drop across the electrode becomes a major contributing factor to the ability
to
successfully produce an electrohydraulic discharge within reactor housing.
[0052] Additionally, as flow velocity through the reactor housing
increases, choke points can develop in certain areas of flow through the
reactor
housing and these choke points cause pressure increases that impact the
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pressure drop across reactor housing. In order to successfully discharge
plasma
in reactor housing, it is preferred to minimize these potential choke points.
As
such, it is preferred that the treatment systems according to the invention
(such
as system 10, 110, or 210) be configured so that treated water stream on the
outlet end of reactor housing has the highest flow coefficient possible,
according
to the following equation:
F
where Cv = Flow coefficient or flow capacity rating of valve. (volume of water
of
flow in gpm)
F = Rate of flow (US gallons per minute)
SG = Specific gravity of fluid (Water = 1)
AP = Pressure drop across body (psi).
[0053] There are several factors that can be manipulated either
individually or together, that will optimize the pressure drop across the body
and
the flow rate of the fluid through the reactor. Lowering the flow rate is not
desirable, as that lowers the flow coefficient and it is preferred that the
flow
coefficient on the discharge end be as high as possible. Lowering the flow
rate
also minimizes contact time and decreases efficiency, which are not desirable.
Additionally, it is preferred to minimize the pressure drop across reactor
housing
135 to increase the flow coefficient. In experiments conducted using treatment
systems according to the invention, it was determined that minimizing the
pressure on the discharge end of reaction chamber aids in the formation of
plasma by lowering the breakdown voltage. In high conductivity water, such as
the water frequently encountered in re-circulating water system, lowering the
breakdown voltage results in less parasitic current losses (V=iR) and
therefore
more energy will be input into the water being treated via plasma.
[00541 In addition to minimizing the pressure on the discharge end,
diminished plasma generation associated with increased conductivity in the
water
being treated may also be addressed by (1) moving the high voltage electrode
and the ground electrode closer together (but this has the drawback of
reducing
33
the volume of water being exposed to the plasma discharge), (2) increasing
the voltage between the ground and high voltage electrode (but this has the
drawback of possible component failure in the high voltage generator), or (3)
increasing the gas phase dielectric barrier around the high voltage electrode.
The treatment systems and methods according to the invention most
preferably rely on increasing the gas phase dielectric barrier through the use
of a gas infusion system to add bubbles to the water being treated as the most
favorable way to aid in plasma generation in high conductivity water.
[0055] Referring to FIGS. 6-7, a preferred embodiment of a reaction
chamber 136 and electrode mount assembly 80 are shown. The reaction
chamber 136 is like that shown in FIG.4 and could be used with treatment
system 10, 110, or 210. Reaction chamber 136 comprises a sealed, water-
tight housing 135 capped at both ends 137, 139 and having fittings or ports
129, 133 that allow water and gasses to be introduced and removed from the
reactor housing 135, and for electrical connections to be made with the high
voltage electrode 138 and ground electrode 148. In this embodiment, a
continuous stream of water 114 is pumped from a source in the water system
being treated into the reactor housing 135 and then out through the top as
treated water 150. As the water flows into the reactor housing 135, ozone gas
130 (preferably generated in the high voltage power supply 140 (not shown in
FIG. 6)), may be introduced into the water using a venturi 121 or other type
of
gas injector/diffuser. The water/ozone mixture 124 then enters inlet port 129
where is it optionally mixed with compressed air 122 or other gases (which
may be bubbled through a microbubbler, such as 120) prior to entering reactor
housing 135. Disposed within reactor housing 135 is an electrode mount
assembly 80 connected at one end to high voltage electrode 138 and at the
opposite end to ground electrode 148. The potential difference between the
high voltage electrode and the ground electrode results in a plasma discharge
in the water between the high voltage base 82 and ground base 92, in an area
referred to herein as the high voltage discharge area or zone or plasma
discharge area or zone (shown as 101 on FIG. 6).
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[0056] Referring to FIGS. 6-14, disposed within reactor housing 135 is an
electrode mount assembly 80. Electrode mount assembly 80 preferably
comprises a high voltage base 82, a ground base 92, and a ground electrode
tube 147. The high voltage base 82 and ground base 92 are configured to hold
the high voltage electrode and ground electrode at a fixed distance from each
other, so that the electrode gap is around 1 to 10 mm, and most preferably
around 5 mm. This distance allows a sufficient volume of water to be exposed
to
the plasma, particularly when the preferred ground electrode configuration as
discussed below is used, while not requiring an increase in the output voltage
from the high voltage generator. High voltage base 82 preferably has a wheel-
shaped configuration comprising a central hub 88, a plurality of spokes 86
extending radially outward from hub 88 and terminating at outer ring or rim
84.
Hub 88 preferably has a slightly tapered or truncated cone configuration (as
shown in FIG. 8), but may also be substantially cylindrical. An opening 90 is
disposed though hub 88 and high voltage wire 138 (or a thicker rod or
conducting
material connected to wire 138) fits within opening 90 to act as a high
voltage
electrode. Most preferably, high voltage wire 138 has a dielectric coating on
its
entire length to minimize parasitic electrochemical reactions.
[0057] Spokes 86 are preferably angled relative to hub 88 and rim 84 (as
shown in FIGS. 6-7), which minimizes the contact area of the hub to the high
voltage wire electrode , thereby increasing charge density on the electrode by
reducing conduction through the plastic material of the hub. Rim 84 is
preferably
has a shape and size configured to mate with the shape and size of reactor
housing 135 (or 35 or 235). Reactor housing is most preferably cylindrical, so
rim 84 is also preferably cylindrical with a diameter slightly smaller than
the inner
diameter of reactor housing 135 so that high voltage base 82 may be inserted
into the reactor housing 135 and will fit snugly against an internal wall of
housing
135. The open wheel-like configuration of high voltage base 82 aids in
eliminating any pressure choke points that could impede the plasma production.
[0058] Another preferred embodiment of a high voltage base 182 for use
with electrode mounting assembly 80 is shown in FIGS. 9A-9B. High voltage
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base 182 preferably comprises a central hub 188, a plurality of spokes 186
extending radially outward from hub 188 and terminating at rim 184. High
voltage base 182 is similar to base 82, except in this embodiment hub 188 is
preferably substantially cylindrical and spokes 188 are not angled relative to
hub
188 and rim 184. A substantially cylindrical hub provides greater precision in
the
gap distance between the high voltage wire/electrode and the ground electrode.
A substantially cylindrical hub 188 may also be used with angled spokes,
similar
to FIGS. 6-7.
[0059] Referring to FIGS. 7 and 10-13, ground base 92 preferably
comprises a rim 94, a body 96 extending from rim 94, and a collar 98 extending
from body 96. An opening 100 is disposed through collar 98. Rim 94 preferably
has a shape and size configured to mate with the shape and size of reactor
housing 135 (or 35 or 235). Reactor housing is most preferably cylindrical, so
rim 94 is also preferably cylindrical with a diameter slightly smaller than
the inner
diameter of reactor housing 135 so that ground base 92 may be inserted into
the
reactor housing 135 and will fit snugly against an internal wall of housing
135.
Body 96 preferably has a closed, truncated cone or dome like shape, which aids
in funneling any added gas bubbles into plasma discharge zone 101 and toward
high voltage electrode 138.
[0060] Another preferred embodiment of a ground base 192 is shown in
FIG. 14. Ground base 192 preferably comprises a rim 194, a body 196
extending from rim 194, and a collar 198 extending from body 196, all similar
to
ground base 92. An opening 200 is disposed through collar 198. Unlike ground
base 92, ground base 192 has an added wheel-like structure (similar to high
voltage base 182), Ground base 192 also comprises a central hub 204, a
plurality of spokes 202 extending radially outward from hub 204 and
terminating
at rim 194, and an opening 206 disposed through hub 204.
[0061] A ground wire 148 is disposed through opening 100 and
connected to ground electrode tube 147. A tab with an aperture may be provided
at an end of ground electrode tube 147 to facilitate connection to ground wire
148. Most preferably, ground electrode tube 147 (as shown in FIGS. 6-7)
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comprises a substantially cylindrical body (or other shape configured to be
inserted in collar 98) or hollow tube with a plurality of openings 149
disposed
through a sidewall of the body. Ground electrode tube 147 is preferably made
of
titanium, but other conductive materials, such as stainless steel or copper
may
also be used. Openings 149 are preferably circular having a diameter between
about 4mm and 8 mm; but other shapes may also be used. The size of the
openings 149 are large enough to allow excess gas to escape and prevent a
pressure choke point inside plasma discharge zone 101. Openings 149 have the
advantage of greater field enhancement around the edges of the openings, which
produce unformed field lines that enhance the effect of the field. Openings
149
also have the advantage of allowing the plasma discharges to be visible (as a
bright light) when reactor housing 135 is clear or has a viewing window. An
exterior sidewall of ground electrode tube 147 preferably has a dielectric
barrier
coating, such as non-conductive ceramic or glass, to reduce parasitic
electrochemical reactions on the outer surface of ground electrode tube 147
and
maximize the potential for generating a plasma in the plasma discharge zone
101.
[0062] Ground electrode tube 147 is most preferably configured to fit
within collar 98 and within hub 88 (as shown in FIG. 7) to connect high
voltage
base 82 and ground base 92. Ground electrode tube 147 may be releasably
attached to collar 98 and/or hub 88, such as by screws. Alternatively, ground
electrode tube 147 may not extend all the way to hub 88 (as shown in FIG. 6).
In
that configuration, high voltage base 80 and ground base 92 are spaced apart
by
their relative locations within reactor body 135 and held in place by
friction,
another structure extending from ground electrode base to high voltage base,
or
other means, such as a lip or other protrusion within reactor body 135
configured
to mate with rims 94 and 84, to position high voltage electrode 138 relative
to
ground electrode tube 147. A lower end of high voltage electrode 138 is
disposed through hub 88 and into ground electrode tube 147. Although high
voltage electrode 138 may extend all the way to ground electrode base 92 or
substantially through the length of ground electrode tube 147 (as shown in
FIG.
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6), most preferably high voltage electrode 138 extends into tube 147 only a
short
distance of around 4 to 30 mm (as shown in FIG. 7) to avoid having the high
voltage electrode interfere with the flow of water through reactor body 135.
High
voltage electrode 138 and ground electrode tube 147 are preferably sized and
configured to provide a gap between the two electrodes of around 1 to 10 mm,
and most preferably around 5 mm. In the configurations shown in FIGS. 6-7,
where high voltage electrode 138 is a rod partially disposed within and
substantially concentric within ground electrode tube 147, the gap is the
radial
distance between an outer wall of the high voltage electrode and an inner wall
of
ground electrode tube 147. Ground electrode tube 147 is most preferably around
2 to 4 inches in length. Having a relatively shorter electrode allows for
greater
charge concentration, which helps with the discharge.
[0063] High voltage wire 138 and ground wire 148 are preferably made of
solid metal, rather than braided wire. This makes connections easier because a
solid wire is easier to seal in end fittings 137, 139 or ports 129, 133. Solid
wiring
also eliminates potential problems with water wicking from the reactor housing
135 to an inner wire core, which could be dangerous.
[0064] Electrode mounting assembly 80, and any variation on the
components of assembly 80, may be used with any reaction chamber/housing in
any treatment system and method according to the invention, including reactor
housing 35, 135, and 235. The preferred electrode mount and ground electrode
configuration as shown in FIGS. 6-7 allow plasma to be generated under a range
of water chemistry conditions. For example, as the conductivity of the water
increases with cycles of re-circulation, the amount of air/gas/ozone that can
be
delivered to the plasma discharge zone 101 can be increased by simply
changing the gas flow rate. Increased gas flow rate corresponds to an increase
in the gas phase dielectric barrier to achieve greater plasma discharge under
high conductivity conditions, without having to alter the distance between the
electrodes or increase the voltage between the ground and high voltage
electrode.
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[0065] A series of tests were performed with a gas infusion system,
reaction chamber, and electrode mount assembly similar to that shown in FIG.
6.
The water system used was a cooling tower located at a local university and
the
water had a conductivity range of 980 mmhos to 1900mmhos. The treatment
system was run continuously over a 4 month period. The discharge voltage was
set at 240 kV and the electrode gap between the high voltage and ground
electrodes was 5 mm. The reactor housing was made of transparent material so
the inside of the housing was visible. During operation, plasma discharge
between the ground and high voltage electrode and bubbles being forced into
the
space between the ground and high voltage electrode were both observed.
Once the conductivity increased to over 1000 mmhos, plasma discharge was not
observed with the use of bubbles introduced through the venturi alone;
however,
plasma discharge was again observed once additional compressed air was
introduced into the space between the ground and high voltage electrodes.
[00661 A preferred embodiment for a support structure 62 for a Marx
generator used in any high voltage generator according to the invention, such
as
high voltage generator system 40, 140, or 240, is shown in FIGS. 15-18.
Support
structure 62 preferably comprises upper support arm 66T, lower support arm
66B, and one or more end support arms 66E extending between lower support
arm 66B and upper support arm 66T. Upper support arm 66T preferably forms a
substantially rectangular shape with an open central portion. Similarly, lower
support arm 66B preferably forms a substantially rectangular shape with an
open
central portion. Vertical end support arms 66E connect the upper and lower
support arms 66T and 66B at one end of the support structure 62 to form a
generally U-shaped frame. The other end of the support structure 62 is
preferably substantially open, with no vertical connectors to join arms 66T
and
66B. Attachment tabs 64 are preferably disposed at one end of support
structure
62, extending outwardly from each of the top and bottom support arms 66T and
66B. Disposed through tabs 64 are apertures 65. Tabs 64 and apertures 65
facilitate securing the support structure 62 to a bottom surface of spark gap
chamber 41 or outer housing 43, depending on the configuration of chamber 41
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and housing 43, or to a capacitor bank housing 77 disposed within spark gap
chamber 41 or outer housing 43. Support structure 62 may also be integrally
formed from a single part with spark gap chamber 41 or outer housing 43.
[0067] Extending upwardly from each lower support arm 66B are a
plurality of paired posts 70A-71A, 70B-71B, and 70C-71C. A plurality of first
posts 70A, 70B, and 70C extend from a first side (forward side) of lower
support
arm 66B and a plurality of second posts 71A, 71B, and 71C extend from a
second (rearward) side of lower support arm 66B. With reference to FIGS. 20-21
(which show the Marx ladder support structure 62 on capacitor bank housing 77,
with connections between the two), and the circuit diagram of FIG. 22. (which
is
representative of a typical circuit for a Marx generator or Marx ladder, that
may
be connected to support structure 62), a spark gap switch (S1, S2, etc.),
comprising two spaced apart electrodes 76, is disposed between each pair of
posts, such that S1 is between 70A and 71A and 52 is between 70B and 71B,
etc. Disposed through each post is an aperture 72, though which a spark gap
electrode mount 73 is disposed. A spark gap electrode 76 is attached at an end
of the spark gap electrode mount 73 disposed inside support structure 62. This
forms a plurality of spark gap electrode pairs between each pair of posts 70A-
71A, 70B-71B, etc. The electrodes 76 and mounts 73 are preferably configured
to allow the electrode to move laterally along the mount to selectively adjust
the
gap distance between each pair of spark gap electrodes. Most preferably, the
spark gap electrode mounts 73 comprise a screw on to which each electrode 76
is attached in threaded engagement on an end of the mount 73 disposed within
Marx ladder support structure 62. This preferred configuration allows the
relative
positions of each pair of electrodes 76 to be selectively modified to move
them
closer together or farther apart within Marx ladder structure 62 to increase
or
decrease the spark gap distance by simply rotating the electrodes 76 along the
length of mount 73. Most preferably the spark gap distance between each pair
of
electrodes 76 is around 15 to 40 mm. Alternatively, each spark gap electrode
76
may be fixed at an end of each mount 73 within structure 62 and the mounts 73
may be configured for lateral movement relative to posts 70, 71 to selectively
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adjust the gap distance. A combination of adjustable electrodes and adjustable
mounts may also be used.
[0068] Most preferably, Marx ladder structure 62 rests on a capacitor
bank housing 77. Within capacitor bank housing 77 are a plurality of
capacitors
and resistors connected together according well-known Marx ladder circuitry. A
plurality of apertures are disposed through an upper end or removable cover of
housing 77 to allow wiring 75 is pass in order to connect the capacitors to
the
spark gap switches. An end of each mount 73 disposed outside the Marx ladder
structure 62 is connected by wiring 75 to capacitors within a capacitor bank
housing 77, such that capacitor Cl is connected to the mounts 73 on post pair
70A-71A, capacitor C2 is connected to the mounts 73 on post pair 708-71B, and
so forth. Most preferably, 3 to 6 pairs of posts are provided for structure
62, but
additional pairs may be provided as needed to generate sufficient voltage as
will
be understood by those of ordinary skill in the art. For example, there would
be
five pairs of posts for a circuit as shown in FIG. 22, one pair for each spark
gap
switch Sl-S5. Variations in these arrangements may be made, as will be
understood by those of ordinary skill in the art.
[0069] The dimensions of structure 62 are preferably around 2 inches
wide by 2 inches high and 3 inches wide by 3 inches high, for a 14 inch
length.
As described herein, width is a dimension substantially between a pair of
posts
70-71, height is the dimension of vertical support arms 66E in a direction
from
lower support arm 66B toward upper support arm 66T, and length is the longer
dimension of support arms 661, 66B in a direction from vertical support arms
66E
toward tabs 64. These dimensions are preferred in order to physically separate
the spark gap electrodes to aid in preventing the spark gaps from being
bridged
by metal deposits, which would disrupt generation of the high voltage pulse in
the
Marx ladder. Most preferably, the gap distance between the spark gap
electrodes 76 (the distance between a pair of electrodes 73 on each pair of
posts
70-71, as shown on FIG. 20 as G) is around 15 mm to 40 mm, and most
preferably around 27mm. The gap distance may be selectively increased or
decreased by moving electrodes 76 on electrode mounts 73, which changes the
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voltage produced by the high voltage generator. Additionally, other sizes for
the
support structure 62 may be used to scale the spark gap dimensions,
particularly
if a larger gap than what is achievable by variation of distance on mounts 73
is
desired. Additionally, larger widths and heights may be used, but it is
believed
that much larger than 3X3 does not offer any significant advantage to overall
system operation because metal deposition in the channel is no longer a factor
in
system failure at larger dimensions.
[0070] The support arms 66T, 66B, and 66E form a substantially open
support structure frame. Many prior art Marx ladders are in enclosed
structures,
which can result in problems such as parasitic discharge as a result of metal
depositing on the walls of the Marx chamber or support structure. By having a
substantially open structure for a support frame 62, these problems are
avoided.
For example, by moving away from the closed support structure and moving to
an open support system that physically isolates the spark gap electrodes from
each other. With the configuration of the preferred support structure 62,
including the preferred dimensions, any metal deposits resulting from the
spark
gap discharge cannot make a bridge between the electrodes and therefore
cannot interfere with the discharge timing.
[0071] Support structure 62 is preferably made of ozone resistant
materials, such as teflon, ABS, or fiberglass. Since ozone is generated by the
Marx ladder, it is preferred to use such resistant materials to fabricate the
support
structure 62 to avoid damaging the structure. Using
materials that are
susceptible to being attacked by ozone can weaken the support structure of the
spark gap electrodes and with a repeated, substantially continuous fire use
needed for treating flowing water systems according to the invention, this
weakened structure can undergo mechanical failure and break. It is also
preferred to coat the surfaces of support structure 62 with oil, such as
mineral oil
or silicon oil. The oil will aid in preventing any metal from the spark gap
electrodes from depositing onto to surfaces of support structure 62. If
deposits
are observed they can be easily cleared away by wiping the oil layer off and
reapplying a fresh coating. Additionally, it is preferred that lower support
arm
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66B, a lower portion of posts 70, 71, and a lower portion of vertical end
support
arms 66E be submerged in an oil bath 74, as shown in FIG. 19.
[0072] Referring to FIGS. 19-21, a preferred housing configuration for
high voltage generator system 40 is shown. High voltage generator system 40
preferably comprises an outer housing 43, a spark gap chamber 41, and a Marx
ladder 42. Marx ladder 42 preferably comprises a support structure 62, a
capacitor bank housing 77, a low voltage driver circuit 39, a plurality of
capacitors
C, resistors R, and spark gap electrodes 76. Connections through outer housing
43 are provided for connecting an external power source (such as a wall
outlet)
to driver circuit 39 and for connecting air pumps 44 to spark gap chamber 41
and
for withdrawing ozone (and other components of air) from within spark gap
chamber 41.
[0073] Outer housing 43 is preferably a structure configured to enclose
spark gap chamber 41 and Marx ladder 42. It preferably has a removable cover
or top or an openable door to allow access to the interior of the housing 43
and
access to spark gap chamber 41. Outer housing 43 is preferably made from
polycarbonate, lexan or another rigid polymer, but other materials may be
used.
Outer housing 43 also preferably includes a dielectric barrier to isolate the
Marx
ladder 42 from the surrounding environment and prevent arcing from the
internal
components to nearby metal structures, electrical outlets, and other
monitoring
and control systems. Such a dielectric barrier may be a separate layer of
material or coating on an inside or on an exterior of housing 43.
[0074] Capacitor bank housing 77 preferably has a removable upper
cover or openable door to allow access to the capacitors C and resistors R
within
the housing. Apertures are provided in the upper cover of housing 77 to allow
wires to connect the capacitors to spark gap electrodes 76 through spark gap
electrode mounts 73. Another aperture is disposed through housing to connect
the capacitor bank to low voltage driver circuit 39. Housing 77 is preferably
configured to contain an oil bath 74 having sufficient volume to at least
partially
submerge the capacitors. Mineral oil or silicon oil may be used for oil bath
74.
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Capacitor bank housing 77 may be disposed within spark gap chamber 41 or
may be external to spark gap chamber 41.
[0075] Spark gap chamber 41 may comprise another structure to enclose
at least the Marx ladder support structure 62 and may enclose other components
of the Marx ladder 42. Spark gap chamber 41 preferably has a removable top or
cover or openable door so that support structure 62 (or other components of
Marx ladder 42 within spark gap chamber 41) may be accessed. In that
configuration, lower support arm 66B of Marx ladder support structure 62 would
rest on a bottom surface of spark gap chamber 41. Alternatively, spark gap
chamber may be a removable cover that fits over support structure 62 (and may
fit over other components of Marx ladder 42) but does not have a bottom
structure. In that configuration, lower support arm 66B of support structure
62 for
high voltage generator 42 would rest on an upper surface of capacitor bank
housing 77 (or alternatively on a bottom surface of outer housing 43). If a
removable cover is used, a seal is preferably provided to allow ozone to be
pumped or suctioned out of spark gap chamber 41. An interior surface of spark
gap chamber 41 and any piping or conduit used to transport the ozone generated
by the high voltage generator 42 to reaction chamber 36 are preferably made of
ozone resistant materials, such as teflon, ABS, or fiberglass. The use of such
resistant materials to fabricate these parts is preferred to avoid damaging
them
by exposure to ozone. A second oil bath 74 is optionally disposed in the
bottom
of spark gap chamber 41 or outer housing 43 or may be disposed in a separate
tray or other container (not shown) for Marx ladder support structure 62. Oil
bath
74 preferably has sufficient volume so that lower support arm 66B, a lower
portion of posts 70, 71, and a lower portion of vertical end support arms 66E
are
submerged in the oil. Mineral oil or silicon oil may be used for oil bath 74.
Support structure 62 is also preferably coated in oil. Outer housing 43 may be
configured to act as a housing for high voltage generator system 40 and a
spark
gap chamber, so that a separate spark gap chamber 41 is not required with
modifications as will be understood by those of ordinary skill in the art. A
configuration without a separate spark gap chamber may be particularly useful
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when a primary outer housing is provided to contain both the high voltage
generator system and reaction chamber (such as housing 260, which contains
high voltage generator system 240 and reaction chamber 236).
[0076] Various apertures or ports are disposed through sidewalls on outer
housing 43,spark gap chamber 41, and capacitor bank housing 77 to allow power
to be supplied to the Marx ladder 42 from power system 46, to allow voltage to
be carried from the Marx ladder 42 to reaction chamber 36, to allow air to be
blown into spark gap chamber 41 from air pumps/compressors 44 through a
conduit 47, and to allow ozone 30 to be removed. Air pumps 44 may be used to
cool high voltage generator 42, pressurize the spark gap chamber 41, and/or to
remove ozone (force ozone out of spark gap chamber or outer housing) through
a conduit or piping. A venturi or vacuum pump may also be used to remove
ozone from spark gap chamber by suction and to pressurize spark gap chamber.
[0077] Most preferably, spark gap chamber 41 (or outer housing 43 if a
separate spark gap chamber is not used) is maintained at a reduced pressure or
a negative pressure, less than 1 atmosphere, which supports intermittent
firing of
the spark gaps to periodically generate a high voltage pulse. Typical Marx
ladder
generators are operated at pressures greater than 1 atmosphere. The treatment
systems and methods according to the invention require substantially
continuous
high voltage generation (repeated cycles of charging and discharging,
preferably
with some period of deactivation for cooling between each repeated cycle) in
order to treat a flowing or re-circulating water system. In order to operate a
Marx
ladder according to the invention, such as 42, 142, or 242, in such a
substantially
continuous operation mode, it is preferred to reduce the pressure or operate
in a
vacuum, which allows the system to multiply at lower voltages and extends the
life of the Marx ladder.
[0078] Any of the components of treatment systems according to the
invention described herein, including various gas infusing system components,
electrode mount assembly 80, and Marx ladder support structure 62, may be
used together in any combination with other components or other embodiments
within the scope of the invention, Any particular treatment system embodiment,
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such as treatment systems 10, 110, and 210, is not limited to only those
components and configurations specifically described with respect to that
embedment,
[0079j A preferred method of treating water in a flowing or re-circulating
water system comprises generating a high voltage pulse in a high voltage
generator preferably comprising a Marx ladder, directing the high voltage
pulse to
a high voltage electrode disposed in proximity to a ground electrode with a
flow
of water to be treated passing between the ground and high voltage electrodes,
and generating a plasma discharge in the flowing water in a plasma discharge
zone disposed between and around the high voltage and ground electrodes.
Most preferably, water flows continuously through the discharge zone and
plasma is periodically generated (around every 15 minutes) based on periodic
operation of the Marx ladder. According to another preferred embodiment, a
method of treating water further comprises injecting air or other gas into the
plasma discharge zone. According to yet another preferred embodiment, a
method comprises capturing ozone gas, which is produced as a by-product in
generating the high voltage pulse in the Marx ladder, and injecting the ozone
into
the plasma discharge zone. Most preferably, the injection of air or gas
increases
as the level of conductivity in the water increases with repeated cycles of re-
circulation. A preferred method further comprises pumping air over or
suctioning
air through a housing for the Marx ladder to aid in cooling the components of
the
Marx ladder, flushing ozone from within the housing, and pressurizing the
housing and the Marx ladder is preferably operated under reduced pressure or
vacuum conditions. A preferred method further comprises protecting various
components of the water system from interference or damage that may be
caused by the high voltage pulse generation or plasma discharge. Additionally,
excess energy produced by a high voltage discharge is captured and used to
further condition the water in the water system. Most preferably, methods of
treating water according to the invention use components of the water
treatment
systems described herein.
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[0080] According to another preferred method, the conductivity of the
water is periodically measured (which measurements may be performed by
existing equipment in the water system or equipment incorporated into a
treatment system) and one or more parameters of treatment are modified or
adjusted when the conductivity level reaches a predetermined threshold. These
operating parameters may be adjusted by (1) moving the high voltage electrode
and the ground electrode closer together; (2) increasing a voltage of the high
voltage pulse supplied to the high voltage electrode; (3) increasing a rate of
adding bubbles into the flowing water stream; or (4) reducing the pressure of
the
flowing water stream at the outlet of the reaction chamber. Any combination of
steps may be used to aid in plasma generation under high water conductivity
conditions.
[0081] References herein to water systems include any type of flowing
water system, including industrial, commercial, and residential, that requires
periodic treatment to control or eliminate growth of microbiological species.
Water flowing through the water system may contain contaminants or chemical
or biological treatment agents. References herein to continuous or
substantially
continuous and the like refer to operations of a treatment system according to
the
invention over a prolonged period of time, with repeated cycles of
activation/deactivation of treatment system components, as occurring during
normal operating periods of the water system and treatment system and not
during times of shut-down (such as seasonal shut-down of the water system or
shut-down of the water system or treatment system for maintenance). The
components depicted in the figures are not drawn to scale but are merely
intended as representations of the various components used in preferred
embodiments of treatment systems according to the invention and water systems
with which those treatment systems are used. Additionally, certain components
of the water systems depicted in the figures may be in other locations
relative to
other components of the water systems and the systems of the invention than as
depicted in the drawings. Those of ordinary skill in the art will appreciate
upon
reading this specification, that modifications and alterations to the system
and
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methods for treating flowing water with a ,plasma discharge and ozone while
protecting the components of the water systems may be made within the scope
of the invention and it is intended that the scope of the invention disclosed
herein
be limited only by the broadest interpretation of the appended claims to which
the
inventors are legally entitled.
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