U.S. patent application number 13/369430 was filed with the patent office on 2012-06-07 for system for treatment and neutralization of oxidizing agents in ballast water.
This patent application is currently assigned to SEVERN TRENT DE NORA, LLC. Invention is credited to Harold E. Childers, II, Randolfo Fernandez, David W. Hill, Rudolf Matousek, James B. Moore.
Application Number | 20120138516 13/369430 |
Document ID | / |
Family ID | 38875454 |
Filed Date | 2012-06-07 |
United States Patent
Application |
20120138516 |
Kind Code |
A1 |
Childers, II; Harold E. ; et
al. |
June 7, 2012 |
System for Treatment and Neutralization of Oxidizing Agents in
Ballast Water
Abstract
A system for treating ballast water includes one or more
electrolytic cells in fluid communication with a salt water source
and in fluid communication with one or more ballast water tanks, a
means for controlling hypochlorite generation by the one or more
electrolytic cells, and a neutralization system in fluid
communication with the one or more ballast water tanks. The
neutralization system includes a means for measuring presence of
oxidizing agents in the ballast water, a reducing agent source in
fluid communication with the ballast water, and a means for
controlling the amount of reducing agent supplied to the ballast
water in communication with the means for measuring presence of
oxidizing agents in the ballast water. The system may include a
flow meter for measuring a ballast water flow rate and/or a TOC
analyzer for measuring a TOC content of the ballast water.
Inventors: |
Childers, II; Harold E.;
(Houston, TX) ; Fernandez; Randolfo; (Houston,
TX) ; Matousek; Rudolf; (Richmond, TX) ;
Moore; James B.; (Katy, TX) ; Hill; David W.;
(Sugar Land, TX) |
Assignee: |
SEVERN TRENT DE NORA, LLC
Sugar Land
TX
|
Family ID: |
38875454 |
Appl. No.: |
13/369430 |
Filed: |
February 9, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11757315 |
Jun 1, 2007 |
8147673 |
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13369430 |
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11037642 |
Jan 18, 2005 |
7244348 |
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11757315 |
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Current U.S.
Class: |
210/87 ;
210/96.1 |
Current CPC
Class: |
C02F 1/70 20130101; B63J
4/004 20130101; C02F 2103/008 20130101; C02F 2209/04 20130101; C02F
2209/40 20130101; C02F 2201/46125 20130101; B63J 4/002 20130101;
C02F 2301/043 20130101; C02F 9/00 20130101; G01N 33/1846 20130101;
C02F 2303/185 20130101; C02F 2209/005 20130101; C02F 2303/04
20130101; C02F 1/4674 20130101; C02F 2209/29 20130101; C02F 2209/20
20130101 |
Class at
Publication: |
210/87 ;
210/96.1 |
International
Class: |
C02F 1/76 20060101
C02F001/76; C02F 1/467 20060101 C02F001/467; C02F 1/70 20060101
C02F001/70; C25B 1/26 20060101 C25B001/26 |
Claims
1. A system for treating ballast water, the system comprising: one
or more electrolytic cells in fluid communication with a salt water
source and in fluid communication with one or more ballast water
tanks; a means for controlling hypochlorite generation by the one
or more electrolytic cells; and a neutralization system in fluid
communication with the one or more ballast water tanks, the
neutralization system comprising: a means for measuring presence of
oxidizing agents in the ballast water, a reducing agent source in
fluid communication with the ballast water, and a means for
controlling the amount of reducing agent supplied to the ballast
water, the means for controlling the amount of reducing agent
supplied in communication with the means for measuring presence of
oxidizing agents in the ballast water.
2. The system of claim 1, further comprising at least one of: a
flow meter for measuring a flow rate of the ballast water, the flow
meter in communication with the means for controlling hypochlorite
generation; and a total organic carbon analyzer for measuring a
total organic carbon content of the ballast water, the total
organic carbon analyzer in communication with the means for
controlling hypochlorite generation.
3. The system of claim 2, the means for controlling hypochlorite
generation comprising: a control system in communication with at
least one of: the flow meter and the total organic carbon analyzer;
and a power source electrically connected to the one of more
electrolytic cells, wherein the control system controls an amperage
applied to the one or more hypochlorite electrolytic cells
responsive to at least one of: the total organic carbon content
measured by the total organic carbon analyzer and the flow rate of
the ballast water measured by the flow meter.
4. The system of claim 1, the means for measuring presence of
oxidizing agents in the ballast water comprising one or more
oxidation/reduction potential analyzers for determining an
oxidation/reduction potential of the ballast water.
5. The system of claim 4, the one or more oxidation/reduction
potential analyzers in communication with the means for controlling
hypochlorite generation, wherein the means for controlling
hypochlorite generation utilizes the determined oxidation/reduction
potential of the ballast water to confirm the presence of excess
oxidizing agents in the ballast water.
6. The system of claim 1, the reducing agent source comprising: a
reducing agent tank; and a pump in fluid communication with the
reducing agent tank and in fluid communication with the one or more
ballast water tanks, the pump in communication with the means for
controlling the amount of reducing agent supplied to the ballast
water.
7. The system of claim 6, the reducing agent source comprising one
or more reducing agents selected from a group consisting of: sodium
sulfite, sodium metabisulfite, sodium bisulfite, sulfur dioxide,
and sodium thiosulfate.
8. The system of claim 6, further comprising: a means for
discharging the ballast water from the one or more ballast water
tanks.
9. The system of claim 8, the means for discharging the ballast
water from the one or more ballast water tanks comprising: one or
more discharge pumps in fluid communication with the one or more
ballast water tanks; and discharge piping in fluid communication
with the one or more discharge pumps, wherein the discharge piping
defines a discharge opening.
10. The system of claim 9, wherein the neutralization system is in
fluid communication with the means for discharging the ballast
water from the one or more ballast water tanks.
11. A system for treating ballast water, the system comprising: one
or more electrolytic cells in fluid communication with a side
stream diverted from a main ballast water stream and in fluid
communication with one or more ballast water tanks; a means for
controlling hypochlorite generated in the side stream by the one or
more electrolytic cells; at least one of: a flow meter for
measuring a flow rate of the ballast water, the flow meter in
communication with the means for controlling hypochlorite
generation, and a total organic carbon analyzer for measuring a
total organic carbon content of the ballast water, the total
organic carbon analyzer in communication with the means for
controlling hypochlorite generation, wherein the means for
controlling hypochlorite generation controls an amperage applied to
the one or more electrolytic cells responsive to at least one of:
the total organic carbon content measured by the total organic
carbon analyzer and the flow rate of the ballast water measured by
the flow meter; the system for treating ballast water further
comprising: a neutralization system in fluid communication with the
one or more ballast water tanks, the neutralization system
comprising: one or more oxidation/reduction potential analyzers for
measuring an oxidation/reduction potential of the ballast water, a
reducing agent source in fluid communication with the ballast
water, and a means for controlling the amount of reducing agent
supplied to the ballast water responsive to the measured
oxidation/reduction potential of the ballast water.
12. The system of claim 11, further comprising: a means for
removing hydrogen gas from the side stream, the hydrogen gas
generated as a by-product of hypochlorite generation.
13. The system of claim 12, the means for removing hydrogen gas
from the side stream comprising: a hydrocyclone separator
comprising a cylindrical top section and a conical bottom section,
the separator facilitating a separation process for removing
hydrogen gas from the side stream entering the separator, the
separation process resulting in removal of the hydrogen gas through
the top section of the separator, the side stream having the
hydrogen gas removed therefrom exiting the separator through the
bottom section.
14. The system of claim 11, further comprising: a filter positioned
upstream of the one or more electrolytic cells to remove debris
from the side stream prior to entering the one or more electrolytic
cells.
15. The system of claim 14, wherein the filter is a self-cleaning
filter that measures a pressure differential across the filter and
initiates a cleaning process responsive to a determination that the
pressure differential has reached a predetermined threshold or
responsive to a determination that a predetermined amount of time
has elapsed.
16. The system of claim 11, further comprising: a booster pump for
increasing a pressure of the side stream prior to re-introduction
of the side stream into the main ballast water stream.
17. The system of claim 11, wherein the side stream is diverted
from the main ballast stream upstream of the one or more ballast
water tanks or the side stream is taken from ballast water present
in the one or more ballast water tanks.
18. The system of claim 11, the means for controlling hypochlorite
generation controlling the amount of hypochlorite generated in
order to maintain a weight ratio of hypochlorite to total organic
carbon content.
19. A system for treating ballast water, the system comprising: one
or more electrolytic cells in fluid communication with a side
stream diverted from a main ballast water stream and in fluid
communication with one or more ballast water tanks; a means for
controlling hypochlorite generated in the side stream by the one or
more electrolytic cells; at least one of: a flow meter for
measuring a flow rate of the ballast water, the flow meter in
communication with the means for controlling hypochlorite
generation, and a total organic carbon analyzer for measuring a
total organic carbon content of the ballast water, the total
organic carbon analyzer in communication with the means for
controlling hypochlorite generation, wherein the means for
controlling hypochlorite generation controls an amperage applied to
the one or more electrolytic cells responsive to at least one of:
the total organic carbon content measured by the total organic
carbon analyzer and the flow rate of the ballast water measured by
the flow meter; the system for treating ballast water further
comprising: a neutralization system positioned downstream from the
one or more ballast tanks, the neutralization system comprising a
sulfite auxiliary system that comprises: a sulfite tank, a pump,
and a sulfite analyzer.
20. The system of claim 19, wherein the sulfite analyzer converts
sulfite ions present in a treated effluent to sulfur dioxide,
measures an amount of sulfur dioxide produced, and provides a
control output to control the feed supplied from the sulfite tank
to de-chlorinate the ballast water responsive to the amount of
measured sulfur dioxide.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a divisional of U.S. application Ser.
No. 11/757,315 filed on Jun. 1, 2007, which is a
continuation-in-part of U.S. application Ser. No. 11/037,642 filed
on Jan. 18, 2005 and now issued as U.S. Pat. No. 7,244,348.
FIELD OF THE INVENTION
[0002] The system and process of this invention relate generally to
a system and process for the treatment of ballast water to
eliminate marine species and pathogenic bacteria from ballast
water. More particularly, the system and process of this invention
treats ballast water with hypochlorite produced on-site.
BACKGROUND OF THE INVENTION
[0003] Ballast water is used to balance the weight distribution in
a marine vessel. Ballast water is pumped into tanks where it is
stored to properly balance a vessel for a voyage. Often ballast
water is taken on at one port and transported to another where it
is emptied into the new port. This common practice has an inherent
danger. Releasing the ballast water taken aboard from a distant
location can be both harmful to the environment and dangerous to
human and animals in a new port.
[0004] The introduction of non-native marine life into a new
ecosystem can have a devastating effect on the native flora and
fauna which may not have natural defenses to the new species.
Additionally, harmful bacterial pathogens, such as cholera, may be
present in the origination port. These pathogens can multiply in
the ballast tanks over time and cause an outbreak of illness in the
area where they are released.
[0005] The dangers posed by the marine life and pathogens may be
controlled by killing those species present in the ballast water.
For the past century, chlorination has become the standard way to
disinfect water supplies, potable water, wastewater and swimming
pools, for example, to eliminate epidemics of waterborne
diseases.
SUMMARY OF THE INVENTION
[0006] The present invention provides a system and method for
treating ballast water in a marine vessel. Ballast water is piped
onto a vessel in one port or harbor and discharged upon reaching
another port. On-site hypochlorite generation allows the ballast
water to be treated on board the vessel before the ballast water is
released in a distant port. Treating the ballast water with
hypochlorite generated from the ballast water itself or an
alternate salt water source eliminates many of the marine organisms
and bacteria which may be transported from the first port and
propagated within the ballast water tanks. The elimination of these
organisms in turn eliminates the introduction of non-native marine
species into the water, and prevents outbreaks of water born
diseases such as cholera.
[0007] Halogen-containing oxidizing agents, such as NaClO, HOCl and
HOBr, are produced by hypochlorite generation and intended to kill
organisms in ballast water onboard a vessel. When the ballast water
containing the oxidizing agents is released from the vessel the
oxidizing agents are potentially dangerous to the marine flora and
fauna around the vessel.
[0008] In one embodiment of the system of the invention, the system
comprises a neutralization system to reduce the oxidizing agents to
form neutral salts of the halogens. The neutralization system
comprises a means for measuring presence of oxidizing agents in the
ballast water, a reducing agent source in fluid communication with
the ballast water, and a means for controlling the amount of
reducing agent supplied to the ballast water. The means for
controlling the amount of reducing agent is in communication with
the means for measuring presence of oxidizing agents.
[0009] In one aspect of the neutralization system, the means for
measuring presence of oxidizing agents in the ballast water can
comprise one or more oxidation/reduction potential analyzers for
determining the oxidation/reduction potential of the ballast water.
The means for measuring presence of oxidizing agents in the ballast
water may comprise a means for measuring the total residual oxidant
(TRO) in the ballast water.
[0010] In another aspect of the neutralization system, the reducing
agent source can comprise a reducing agent tank and a pump in fluid
communication with the reducing agent tank. The pump is in
communication with the means for controlling the amount of reducing
agent.
[0011] In additional aspect, the reducing agent source can comprise
any combination of suitable reducing agents. Examples of suitable
reducing agents include sodium sulfite, sodium metabisulfite,
sodium bisulfite, sulfur dioxide, and sodium thiosulfate.
[0012] In another embodiment of the neutralization system, the
system further comprises a means for verifying the effectiveness of
the neutralization of oxidizing agents in the ballast water.
[0013] In an additional embodiment, the system for treating ballast
water of the present invention comprises one or more hypochlorite
electrolytic cells and a neutralization system. The hypochlorite
electrolytic cells are in fluid communication with a salt water
source and one or more ballast water tanks. The neutralization
system is in fluid communication with the ballast water tanks.
[0014] In another embodiment, the system for treating ballast water
further comprises a means for discharging the ballast water from
the ballast water tanks. In one aspect, the means for discharging
the ballast water from the ballast water tanks can comprise one or
more discharge pumps in fluid communication with the ballast water
tanks and discharge piping in fluid communication with the
discharge pumps. The discharge piping defines a discharge opening
to outside of the vessel. The neutralization system can be in fluid
communication with the means for discharging the ballast water from
the ballast water tanks.
[0015] In additional embodiments of the system for treating ballast
water, the system for treating ballast water can comprise any
combination of a means for controlling hypochlorite generation, a
flow meter for measuring ballast water flow rate, a total organic
carbon analyzer for measuring total organic carbon content of the
ballast water, a means for verifying the effectiveness of the
ballast water treatment, and a means for verifying the
effectiveness of the neutralization of the oxidizing agents in the
ballast water.
[0016] In one embodiment of the process of this invention, the
process comprises neutralizing the oxidizing agents in the ballast
water onboard a vessel by measuring the oxidation/reduction
potential of the ballast water. One or more reducing agents are
added to the ballast water to neutralize the oxidizing agents in
the ballast water in response to the measured oxidation/reduction
potential. In one aspect, the amount of reducing agent added to the
ballast water can be modulated to maintain an oxidation/reduction
potential measurement that indicates excess reducing agent is
present in the ballast water. In another aspect, the
oxidation/reduction potential can be maintained at less than about
200 mV. In still another aspect, the oxidation/reduction potential
is maintained at about 0 mV.
[0017] The oxidation/reduction potential of the ballast water can
be measured at any suitable site. Examples of suitable sites
include within the one or more ballast water tanks, downstream from
the ballast water tank, upstream from one or more ballast water
discharge pumps, downstream from the ballast water discharge pumps,
prior to the addition of reducing agent, and after the addition of
reducing agent.
[0018] In additional embodiments of the neutralization process, the
process can further comprise any combination of recording the
oxidation/reduction potential of the ballast water at timed
intervals, providing the recorded oxidation/reduction potentials to
a regulatory agency, and removing the recorded oxidation/reduction
potentials with a portable data recording device.
[0019] In a further embodiment of the process of this invention,
the process comprises treating the ballast water with generated
hypochlorite and neutralizing the ballast water. The process
comprises drawing ballast water onboard a vessel and feeding the
ballast water to one or more ballast tanks. Salt water from a salt
water source is piped to the one or more hypochlorite electrolytic
cells. An amperage is applied to the one or more hypochlorite
electrolytic cells to produce hypochlorite within the salt water.
The salt water comprising hypochlorite is introduced to the ballast
water. The ballast water may be measured to determine the presence
of oxidizing agents in the ballast water with a means for measuring
presence of oxidizing agents. Reducing agent is added to the
ballast water in response to the measured presence of oxidizing
agents in order to neutralize the oxidizing agents prior to
discharge of the ballast water from the vessel.
[0020] In one aspect, the salt water source comprises a side stream
removed from the ballast water. In another aspect, the means for
measuring presence of oxidizing agents comprises one or more
oxidation/reduction potential analyzers.
[0021] In another embodiment, the process for treating ballast
water further comprises measuring the oxidation/reduction potential
of the ballast water and adding a reducing agent to the ballast
water to neutralize oxidizing agents present in the ballast water
in response to the measured oxidation/reduction potential. The
ballast water is then discharged from the vessel. In one aspect,
the amount of reducing agent added to the ballast water is
modulated to maintain an oxidation/reduction potential measurement
that indicates excess reducing agent is present in the ballast
water. In another aspect, the process further comprises measuring
and recording the oxidation reduction potential of the combined
ballast water and side stream to confirm that excess oxidizing
agents are present. Optionally, residual oxidizing agent(s) can be
maintained at a concentration of at least 1 ppm.
[0022] In a further embodiment, the process further comprises
measuring and recording process data. Examples of process data
which may be recorded include ballast water flow rate, amperage
applied to the hypochlorite electrolytic cells, voltage of the
hypochlorite electrolytic cells, oxidation/reduction potential of
the ballast water and side stream combined, and oxidation/reduction
potential of the ballast water prior to discharge from the
vessel.
[0023] In additional embodiments, the amount of hypochlorite
generated may be controlled by modulating the amperage applied to
the hypochlorite electrolytic cells. The hypochlorite generated may
be controlled in response to the measured flow rate of the ballast
water or the total organic carbon content of the ballast water. In
another aspect, the amount of hypochlorite generated can be
controlled to ensure that excess oxidizing agent(s) exist in the
ballast water.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic of this invention's system for
treating ballast water.
[0025] FIG. 2 is a schematic of this invention's system for
neutralizing chlorine.
[0026] FIG. 3 is a chart showing the experimental results of
treating ballast water with the system and method of this
invention.
[0027] FIG. 4 is another chart showing the experimental results of
treating ballast water with the system and method of this
invention.
[0028] FIG. 5 is a schematic of one embodiment of the system for
treating ballast water.
[0029] FIG. 6 is a schematic of one embodiment of the system for
de-halogenating ballast water.
DETAILED DESCRIPTION
[0030] The present invention provides a system and process for
treating ballast water. One preferred on-site reaction for creating
sodium hypochlorite (NaOCl) is illustrated in the following
equation:
NaCl+H.sub.20+2e.sup.-.fwdarw.NaOCl+H.sub.2.uparw.
[0031] Referring to FIG. 1, in one preferred embodiment of the
invention in which the ballast water is treated on-site, water is
pumped on board a marine vessel, a ship or oil rig, for example.
The water is either seawater with natural salt content or
freshwater. In one embodiment, a side stream of ballast water is
separated from the main water stream going to the ballast tanks
170. In an alternative embodiment, the side stream is drawn from
the ballast water tanks 170 after the main ballast water stream has
entered the ballast water tanks 170. The side stream flows through
the side stream piping 100 to one or more hypochlorite electrolytic
cells 130 where hypochlorite is generated either from the salt
naturally present in the ballast water, if seawater, or from added
chloride salts if fresh water. Seawater is used for the purposes of
this description, but this invention is not limited to seawater.
Any chlorine-generating salt water may be used.
[0032] The one or more electrolytic cells are equipped with
electrodes energized under direct anodic and cathodic current. In
this condition, partial electrolysis of sodium chloride (NaCl)
contained in raw seawater occurs. The aqueous solution of sodium
chloride (NaCl), which is completely dissociated as sodium ion
(Na+) and chlorine ion (Cl.sup.-), reacts at the anode to generate
free chlorine. The hydroxide ions (OH.sup.-) in the water migrate
from the cathodic area and react with Na+ and Cl.sub.2 near the
anode to produce sodium hypochlorite (NaOCl) and hydrogen
(H.sub.2).
[0033] Sodium hypochlorite in water hydrolyzes to form hypochlorous
acid (HOCl). Some of the HOCl reacts with the bromine in the water
to form hypobromous acid (HOBr). HOCl and HOBr act as oxidizing
agents used to treat the ballast water. Further chemical reactions
may occur that generate additional oxidizing agents.
[0034] In one aspect, the water can then flow into a hydrogen
separator 140 where the hydrogen byproduct (H.sub.2) of the
hypochlorite generation is separated from the side stream. The side
stream is then reintroduced to the ballast water stream to kill
marine organisms and bacteria in the ballast water tanks.
[0035] In one embodiment of the invention, the hydrogen separator
140 can comprise a hydrocyclone separator. The hydrogen separator
140 can also comprise a means for venting hydrogen to the
atmosphere 145. Additionally, the hydrogen separator 140 can
comprise a tube with a pressure relief valve to allow the hydrogen
to separate from the liquid. Separating hydrogen from the water
stream is important, as hydrogen is highly flammable. Hydrogen is
flammable in air in concentrations as low as 4.1% and as high as
74%. Without the use of a hydrogen separator 140, it is possible
for hydrogen to be introduced into the ballast water tanks where it
could potentially reach hydrogen-air concentrations in the
flammability range.
[0036] One hydrocyclone separator 140 of this invention comprises a
cylindrical top section and a conical bottom section. Water from
the one or more electrolytic cells, containing hydrogen, enters the
side of the top section. The hydrogen exits the top of the
separator, while the water exits the bottom. The water enters
tangentially to the side of the cylindrical section so that the
water travels in a circular path around the cylindrical and conical
sections before flowing out the bottom of the separator,
facilitating the separation of the water and hydrogen.
[0037] In another embodiment of the invention, a chlorine analyzer
150, in fluid communication with the ballast water stream, measures
the chlorine content of the ballast water. The chlorine analyzer
150 can be positioned downstream from the one or more electrolytic
cells 130. In one aspect, the chlorine analyzer 150 is positioned
downstream from the point where the chlorinated side stream
(treatment stream) reenters the ballast water stream. The chlorine
analyzer 150 may further comprise a sampling unit that modulates
the hypochlorite content in ballast water by measuring the chlorine
level in the water and emitting a signal to the electrolytic cells
130 to adjust the amount of hypochlorite generated in the side
stream relative to a predetermined concentration in the ballast
tank and piping. The chlorine analyzer 150 functions by taking a
sample and mixing it with an acidic iodide or potassium iodide
reagent. The chlorine present in the sample oxidizes the iodide to
iodine. The liberated iodine is measured by a membrane-covered,
amperometric type sensor. The level of iodine is proportional to
the total chlorine concentration in the sample.
[0038] Referring now to FIG. 5, an alternative embodiment of the
system comprises a total organic carbon analyzer. In this
embodiment, the system for treating ballast water comprises one or
more hypochlorite electrolytic cells 130 in fluid communication
with a salt water source 400. The salt water source can be a side
stream 416 of the ballast water drawn onboard the vessel, water
already in the ballast water tanks 220, a sea chest, a separate
salt water tank, or any other source. The hypochlorite electrolytic
cells 130 are also in fluid communication with the ballast water
402. Hypochlorite produced within the salt water by the
hypochlorite electrolytic cells 130 is added to the ballast water.
This addition can be made either in the stream of ballast water
drawn onboard the vessel, directly to the ballast tanks, or at any
other suitable location.
[0039] A total organic carbon analyzer 403 is also in fluid
communication with the ballast water 402. A total organic carbon
(TOC) analyzer 403 is a device which measures the concentration of
carbon in water from organic sources, such as microorganisms, plant
materials, algae, humic materials, organic acids, and mineral
compounds of organic origin. Total organic carbon analyzers are
available from the manufacturers O.I. Analytical.TM. and HACH.TM.
Instruments. As a general rule, it is known in the art that about 1
ppm of chlorine is required to neutralize about 1 ppm of TOC.
[0040] The system further comprises a means for controlling
hypochlorite generation 404 in communication with the total organic
carbon analyzer 403. While the means for controlling hypochlorite
generation 404 can comprise any suitable equipment, in one
embodiment it comprises a control system 405 in communication with
the total organic carbon analyzer 403 and a power source 406 that
is electrically connected to the hypochlorite electrolytic cells
130. The control system 405 can adjust the amperage applied to the
hypochlorite electrolytic cells 130 in response to the TOC
measurement.
[0041] In another embodiment, the system further comprises a flow
meter 407 in fluid communication with the ballast water 402. The
flow meter 407 is in communication with the means for controlling
hypochlorite generation 404. The flow meter 407 can be placed in
the ballast water stream drawn onboard the vessel to measure the
ballast water flow rate. The means for controlling hypochlorite
generation 404 can utilize the ballast water flow rate and the TOC
measurement to determine the amount of hypochlorite required to be
generated to kill the organisms in the ballast water and thus the
amperage that must be applied to the hypochlorite electrolytic
cells 130 to generate the hypochlorite.
[0042] In yet another embodiment, the system comprises an
oxidation/reduction potential analyzer 408 in addition to the TOC
analyzer. In general, an oxidation/reduction potential (ORP)
analyzer measures voltage across a circuit formed by a reference
electrode and a measurement electrode, with the subject solution
between the electrodes. The oxidation/reduction potential of the
ballast water is proportional to the concentration of the HOCl and
HOBr oxidizing agents in the ballast water. Both HOCl and HOBr are
oxidizing agents that include the halogens chlorine and bromine,
respectively. Oxidizing agents steal electrons from the unwanted
plants and animals in the ballast water, altering their chemical
makeup and killing them. The oxidation/reduction potential analyzer
is in fluid communication with the ballast water. The ORP analyzer
408 communicates the oxidation/reduction potential to the means for
controlling hypochlorite generation 404. The ORP analyzer 408 may
communicate the measured oxidation/reduction potential to control
system 405, which in turn may control the means for controlling
hypochlorite generation 404 to modify the amperage applied to the
electrolytic cells in response to the measured oxidation/reduction
potential. The control system 405 may be a programmable logic
controller (PLC). When the ORP analyzer 408 is placed downstream
from the point of addition 409 of the hypochlorite to the ballast
water, the means for controlling hypochlorite generation 404 can
use the measurement to confirm the presence of excess oxidizing
agent(s) in the ballast water to ensure that enough hypochlorite is
present to kill all microorganisms in the ballast water.
[0043] In still another embodiment, the system comprises a means
for recording system data 410. The means for recording system data
410 can comprise any data recording equipment known in the art.
Examples of such data recording equipment include computerized
equipment, such as hard drives, flash memory, CD-ROM's, and
magnetic disks, as well as non-computerized recording equipment,
such as paper plots. System data to be recorded can include any
data desirable to one skilled in the art, including, but not
limited to, ballast water flow rate, amperage applied to and cell
voltage of the hypochlorite electrolytic cells 130,
oxidation/reduction potential of the ballast water 402 and side
stream 416 combined, and oxidation/reduction potential of the
ballast water prior to discharge from the vessel. The PLC may also
be used to record system data.
[0044] In a further embodiment, the system can comprise a means for
verifying the effectiveness 411 of the ballast water treatment. The
means for verifying the effectiveness of the ballast water
treatment can be included within the means for recording system
data 410 or the means for controlling hypochlorite generation 404.
The means for verifying the effectiveness of the ballast water
treatment can comprise any means known in the art capable of
generating and/or analyzing data that demonstrates to a regulatory
authority, such as the Coast Guard or Port Authority, that ballast
water treatment was properly performed. For example, the means 506
for verifying the effectiveness of the neutralization of the
oxidizing agents in the ballast water may comprise one or more
oxidation/reduction potential analyzers. The means for verifying
the effectiveness of the ballast water treatment may utilize
various means for generating, representing, recording and/or
analyzing data including, but not limited to, a plot of system
data, a removable hard drive or flash drive, downloading system
data on a lap top computer or a handheld device, transferring
system data over the internet, or wirelessly transmitting system
data to an off vessel location. The regulatory authority may use
this information to confirm that the ballast water was properly
treated.
[0045] In still a further embodiment, the system comprises one or
more ballast water tanks 220 and a means for discharging 412 the
ballast water from the ballast tanks 220. The means for discharging
412 the ballast water can comprise any suitable combination of
pumps, siphons, and piping to remove the ballast water from the
ballast tanks and the vessel. In one aspect, the means for
discharging 412 the ballast water from the ballast tanks 220
comprises one or more discharge pumps 413 in fluid communication
with the ballast tanks 220, discharge piping 414 in fluid
communication with the discharge pumps 413, and a discharge opening
415 to outside the vessel.
[0046] In an additional embodiment, the system can comprise a means
417 for neutralizing oxidizing agents present in the ballast water.
The means 417 can comprise a sulfite auxiliary system 200 or a
neutralization system 500.
[0047] Referring again to FIG. 1, in another alternative embodiment
of this invention, a filter 180 is present and in fluid
communication with the ballast water stream. The filter can be
positioned upstream from the side stream leading to the one or more
electrolytic cells to remove debris from the side stream. The
filter is preferably a 50-micron self-cleaning filter. A
self-cleaning filter measures the pressure differential across the
filter. As the filter screen becomes clogged with the debris
removed by the filter, the pressure differential increases. Once
the pressure differential reaches a certain setpoint or a
predetermined amount of time has lapsed, the filter screen is
cleaned by a suction scanner with nozzles that spiral across the
inner surface of the screen. The filtration debris is vacuumed from
the screen and expelled out the exhaust valve.
[0048] In another embodiment of the invention, the hypochlorite
electrolytic cell comprises a tubular cell. The tubular cell
comprises an outer monopolar tube and inner bipolar tube. The
hypochlorite electrolytic cell can also comprise other types of
electrolytic cells. Many types of hypochlorite electrolytic cells
are known within the on-site, electrochlorination industry. Other
types of electrolytic cells include a plate type hypochlorite
generator. The electrolytic cell is selected because of its
configuration of connection nodes to the electrodes and the
hydraulic flow of liquid throughout the cell.
[0049] In still another embodiment of the invention, a booster pump
110 is connected to the side stream piping 100 to increase the
pressure of water through the ballast water treatment system. A
pressure drop occurs as the side stream passes through the
hypochlorite electrolytic cells 120. In order to allow the side
stream to be reintroduced into the ballast water stream, the
pressure of the side stream may be increased by the booster pump
110. The booster pump 100 can be positioned either upstream or
downstream from the hypochlorite electrolytic cells 120.
[0050] Ballast water is typically taken aboard in one port or
harbor and then released at the next harbor. Residual oxidizing
agents such as HOCl and HOBr present in the ballast water and not
consumed in the treatment of the ballast water are potentially
harmful to the marine ecosystem in the new harbor where the ballast
water is discharged. The residual oxidizing agents could kill
native flora and fauna in the ecosystem. Consuming or neutralizing
these residual oxidizing agents immediately prior to discharging
the ballast water protects against damage to native flora and
fauna. In one embodiment of the invention, a sulfite auxiliary
system 200 can be added to neutralize residual oxidizing agents
present in the ballast water tank 170 before the ballast water is
released from the vessel into the port, ocean, lake, or river. The
sulfite auxiliary system can be positioned downstream from the
ballast tanks. Referring to FIG. 1, the sulfite auxiliary system
200 can comprise a sulfite tank 210, a pump 220, and a sulfite
analyzer 230. In one aspect the pump of the sulfite auxiliary
system 200 is a diaphragm-metering pump. The diaphragm metering
pump controls the flow of sulfite used to neutralize residual
chlorine.
[0051] The sulfite auxiliary system 200 removes residual chlorine
by reacting the chlorine with sulfur dioxide gas, a solution of
sodium bisulfite, or sodium sulfite. The residual chlorine is
consumed in the following reaction:
Na.sub.2SO.sub.3+Cl.sub.2+H.sub.2O.fwdarw.Na.sub.2SO.sub.4+2HCl
So long as excess sulfite ions are present in the effluent,
effectively no chlorine is present. The sulfite analyzer converts
the sulfite ions in the treated water sample to sulfur dioxide by
mixing the sample with acid. The sulfur dioxide is then stripped
from the sample and measured by a gas sensor. The analyzer 230
provides a control output to control the feed from the sulfite tank
to neutralize oxidizing agents present in the ballast water
stream.
[0052] Alternatively, as shown in FIG. 6 a neutralization system
500 can be employed for neutralizing oxidizing agents in the
ballast water. Neutralization of oxidizing agents containing
halogens generates neutral salt derivatives of the halogens which
no longer function as oxidizing agents. The neutralization system
500 comprises a means 502 for measuring presence of oxidizing
agents in the ballast water, a reducing agent source 501 in fluid
communication with the ballast water, and a means for controlling
the amount of reducing agent 503 supplied to the ballast water. The
means for controlling the amount 503 of reducing agent is in
communication with the means 502 for measuring presence of
oxidizing agents in the ballast water.
[0053] The means 502 for measuring presence of oxidizing agents in
the ballast water can comprise one or more oxidation/reduction
potential analyzers, one or more chlorine analyzers, or wet
chemical analysis with potassium iodine indicator and sodium
thiosulfate titration. The means for controlling the amount of
reducing agent 503 can comprise any combination of equipment know
in the art, including, but not limited to, a control system, a
computer, a programmable logic controller, and a pump.
[0054] In one aspect, the reducing agent source 501 can comprise a
reducing agent tank 505 and a pump 504 in fluid communication with
the reducing agent tank 505. The pump 504 is in communication with
the means for controlling the amount of reducing agent 503.
Suitable pumps include a variable dosing pump.
[0055] In another aspect, the reducing agent source 501 can
comprise one or more suitable reducing agents. Examples of suitable
reducing agents include sodium sulfite, sodium metabisulfite,
sodium bisulfite, sulfur dioxide, and sodium thiosulfate.
[0056] In still another aspect, the neutralization system 500
comprises a means 506 for verifying the effectiveness of the
neutralization of the oxidizing agents in the ballast water. The
means 506 for verifying the effectiveness of the neutralization can
comprise any means known in the art capable of generating and/or
analyzing data that demonstrates that the oxidizing agents in the
ballast water were properly neutralized. For example, the means 506
for verifying the effectiveness of the neutralization of the
oxidizing agents in the ballast water may comprise one or more
oxidation/reduction potential analyzers. The means 506 may utilize
various means for generating, representing, recording and/or
analyzing the data, including, but not limited to, a plot of system
data, a removable hard drive or flash drive, downloading system
data on a lap top computer or a handheld device, transferring
system data over the internet, or wirelessly transmitting system
data to an off vessel location. Optionally, the means 506 can be
included in the means for controlling the amount of reducing agent
503. A regulatory authority can use this data to confirm that the
oxidizing agents present in the ballast water were properly
neutralized.
[0057] In another embodiment of the system for treating ballast
water, the system comprises one or more hypochlorite electrolytic
cells 130 in fluid communication with a salt water source 400 and
one or more ballast water tanks 220, and a neutralization system
500 in fluid communication with the ballast water tanks 220. In one
embodiment, salt water source 400 can be a side stream 416 of the
ballast water drawn onboard the vessel.
[0058] In one aspect, the system can comprise a means for
discharging 412 the ballast water from the ballast tanks. In one
embodiment, the means for discharging 412 the ballast water from
the ballast tanks 220 comprises one or more discharge pumps 413 in
fluid communication with the ballast tanks 220, and discharge
piping 414 in fluid communication with the discharge pumps 413. The
discharge piping 414 can define a discharge opening 415 to allow
the ballast water to be removed from the vessel. In another aspect,
the neutralization system 500 is in fluid communication with the
means for discharging 412 the ballast water from the ballast
tanks.
[0059] In yet another aspect, the system can further comprise a
means for controlling hypochlorite generation 404. Additionally,
the system can comprise a flow meter 407 for measuring ballast
water flow rate. The flow meter is in communication with the means
for controlling hypochlorite generation 404.
[0060] In still another aspect, the system can further comprise a
means 410 for verifying the effectiveness of the ballast water
treatment. The system can also comprise a means 506 for verifying
the effectiveness of the neutralization of oxidizing agents present
in the ballast water. Optionally, both the means 410 for verifying
the effectiveness of the ballast water treatment and the means 506
for verifying the effectiveness of the neutralization of the
oxidizing agents in the ballast water can be included within the
means for controlling the hypochlorite generation 404.
[0061] In one embodiment of a method of this invention, ballast
water is treated by first drawing a ballast water stream on board
the vessel. The ballast water stream may then be filtered. A
portion of the filtered ballast water stream is drawn off through
the side stream piping 100 to form a treatment stream. This
treatment stream is piped to hypochlorite electrolytic cells, where
a current is applied to the cells to produce hypochlorite within
the treatment stream. Hydrogen, which is flammable, is separated
from the treatment stream before the treatment stream is
reintroduced into the main ballast water stream. The ballast water
stream containing the hypochlorite is sampled after the treatment
stream is reintroduced the ballast water stream to determine the
chlorine concentration of the ballast water stream.
[0062] In one aspect of the method of this invention, the treatment
stream is removed from the ballast water stream before the stream
enters the ballast water tank. Alternatively, the treatment stream
is drawn off of the ballast water tanks. The treatment stream is
then treated with hypochlorite and reintroduced into the ballast
water stream before the stream enters the ballast water tank. The
hypochlorite electrolytic cells use natural salt water when the
ballast water tanks take on seawater, to generate hypochlorite in
the treatment stream. Alternatively, if fresh water is used as
ballast water, a sodium chloride salt can be added to the fresh
water to supply the chloride ion.
[0063] In an alternative embodiment of the method, the pressure of
the treatment stream, which drops as the stream enters the side
stream piping 100, is increased with a pump to allow for
re-introduction of the side stream into the main ballast water
stream. In another preferred embodiment of the method, the ballast
water stream is filtered prior to entering the treatment stream. In
another embodiment of the method, hydrogen is separated from the
treatment stream by a hydrocyclone separator.
[0064] In another embodiment of the method, the ballast water
stream is sampled after the treatment stream is reintroduced into
the ballast water to determine the chlorine concentration of the
ballast water stream. The chlorine concentration of the ballast
water stream is measured by a chlorine analyzer. The current in the
hypochlorite electrolytic cells is adjusted in response to the
measured chlorine concentration to increase or decrease the
hypochlorite generated in the treatment stream to achieve the
proper concentration of hypochlorite in the ballast water tank.
[0065] In one embodiment of the process of this invention, the
process for treating ballast water comprises ascertaining the total
organic carbon content of the ballast water. The total organic
carbon content can be ascertained in any suitable manner including
measuring with a total organic carbon analyzer, obtaining a value
from a reference source, and sampling the ballast water and
measuring TOC content with analytical equipment. When measuring the
total organic carbon content of the ballast water, a measurement or
sample can be taken at any suitable location, including in the
incoming ballast water, the water outside the vessel, and the water
in the ballast tanks.
[0066] To generate hypochlorite, salt water from a salt water
source 400 is piped to one or more hypochlorite electrolytic cells
100. In one aspect of the process, the salt water source can be a
side stream 416 of the ballast water drawn onboard the vessel. An
amperage is applied to the one or more hypochlorite electrolytic
cells to produce the hypochlorite within the salt water. The salt
water comprising hypochlorite is introduced to the ballast water to
treat the ballast water. In one embodiment, the hypochlorite is
introduced to the ballast water upstream of the ballast water tanks
to facilitate mixing of the hypochlorite and ballast water.
Hypochlorite production by the hypochlorite electrolytic cells is
modulated in response to the total organic carbon content of the
ballast water. The higher the TOC content of the ballast water the
greater the amount of hypochlorite that must be produced.
[0067] In another embodiment of the process, the step of modulating
hypochlorite production by the hypochlorite electrolytic cells in
response to the total organic carbon content comprises adjusting
the amperage applied to the hypochlorite electrolytic cells.
Increasing amperage results in increased hypochlorite production.
In one aspect, hypochlorite production is modulated to maintain the
presence of residual oxidizing agents in the ballast water.
Residual oxidizing agents refers to oxidizing agents in excess of
the amount required to kill all the microorganisms present in the
ballast water. The presence of residual oxidizing agents in the
ballast water ensures that no microorganisms remain in the ballast
water that can multiply in the ballast water tanks. In another
aspect, hypochlorite production by the hypochlorite electrolytic
cells in modulated so that the weight ratio of hypochlorite in the
ballast water to total organic carbon in the ballast water ranges
from about 1.0 to about 3.0. A weight ratio greater than 1.0 should
maintain residual oxidizing agents in the ballast water.
[0068] In an additional embodiment of the process, ballast water is
drawn onboard the vessel and the flow rate of the ballast water is
measured. The flow rate is combined with the TOC content of the
ballast water to determine the hypochlorite generation rate
required to treat the ballast water.
[0069] In one aspect of the process, process data can be measured
and recorded. Examples of process data include total organic carbon
content of the ballast water, ballast water flow rate, amperage
applied to the hypochlorite electrolytic cells, oxidation/reduction
potential of the ballast water and salt water comprising
hypochlorite combined, and oxidation/reduction potential of the
ballast water prior to discharge from the vessel.
[0070] In still another aspect of the process, residual oxidizing
agents present in the ballast water and produced by the
electrolytic cells in response to the TOC content can be
neutralized prior to discharging the ballast water from the
vessel.
[0071] In an alternative method of this invention, ballast water is
treated by drawing a ballast water stream onto a marine vessel,
filtering the ballast water stream, and removing a portion of the
filtered ballast water stream to form a treatment stream. The
treatment stream is then piped to hypochlorite electrolytic cells,
where a current is applied to the cells to produce hypochlorite
within the treatment stream. Hydrogen is separated from the
treatment stream by a means for venting. The treatment stream is
reintroduced into the ballast water stream and the pressure of the
treatment stream may be increased to allow for the re-introduction.
The ballast water stream may be sampled after the treatment stream
is reintroduced to determine the concentration of oxidizing agents
in the ballast water stream. For example, the stream may be sample
to determine the TRO level of the stream. The current in the one or
more hypochlorite electrolytic cells is adjusted in response to the
measured concentration to increase or decrease the hypochlorite
generated in the treatment stream. The treated ballast water stream
can then piped to the ballast tanks. Finally, prior to discharge,
residual oxidizing agents are neutralized in the ballast water
stream downstream from the one or more hypochlorite electrolytic
cells with sulfite.
[0072] In one embodiment of the method, hydrogen is separated from
the treatment stream by a hydrocyclone separator. Alternatively,
the means for venting hydrogen can comprise venting the ballast
water tanks to the atmosphere.
[0073] In another embodiment of the method, the step of
neutralizing residual oxidizing agents comprises piping the ballast
water stream to a sulfite auxiliary system. The sulfite auxiliary
system is positioned downstream from the ballast water tanks.
[0074] In one embodiment, the process for neutralizing oxidizing
agents present in the ballast water onboard a vessel comprises
measuring the oxidation/reduction potential of the ballast water.
One or more reducing agents are added to the ballast water in
response to the measured oxidation/reduction potential. In one
aspect, the amount of reducing agent added to the ballast water can
be modulated to maintain an oxidation/reduction potential
measurement that indicates excess reducing agent is present in the
ballast water. When excess reducing agent is present, potentially
harmful oxidizing agents such as those containing halogens like
chlorine and bromine should not be present. In another aspect, the
oxidation/reduction potential is maintained at less than about 200
mV. An OPR of less than 200 mV indicates that excess reducing agent
exists. In still another aspect, the oxidation/reduction potential
is maintained at about 0 mV.
[0075] Examples of suitable sites for measuring oxidation/reduction
potential include within the one or more ballast water tanks 220,
downstream from the ballast water tanks 220, upstream from one or
more ballast water discharge pumps 413, downstream from the ballast
water discharge pumps 413, prior to the addition of reducing agent,
after the addition of reducing agent, and combinations thereof. In
another embodiment of the process, the oxidation/reduction
potential of the ballast water can be recorded at timed intervals.
The recorded oxidation/reduction potentials can be monitored to
confirm that neutralization was performed properly. Optionally, the
recorded oxidation/reduction potentials may be provided to a
regulatory agency. In another aspect, the recorded
oxidation/reduction potentials can be removed from the vessel with
a portable data recording device.
[0076] The process for treating ballast water can comprise
neutralizing oxidizing agents present in the ballast water. In one
embodiment, the process for treating ballast water comprises
drawing ballast water 402 onboard a vessel. The ballast water is
fed to one or more ballast tanks 220 on the vessel. Salt water is
piped from a salt water source 400 to one or more hypochlorite
electrolytic cells 130 to generate hypochlorite. The salt water
source can be a side stream 416 removed from the ballast water or
any other suitable source. An amperage is applied to the one or
more hypochlorite electrolytic cells 130 to produce hypochlorite
within the salt water. The salt water comprising hypochlorite is
introduced to the ballast water to treat microorganisms in the
ballast water. In one embodiment, the salt water comprising
hypochlorite is added upstream of the ballast tanks to facilitate
mixing of the hypochlorite and the ballast water within a pipe.
[0077] In one aspect of the process for treating and neutralizing
oxidizing agents present in the ballast water, the means 502 for
measuring presence of oxidizing agents in the ballast water
comprises an oxidation/reduction potential analyzer. Optionally,
the amount of reducing agent added to the ballast water is
modulated to maintain an oxidation/reduction potential measurement
that indicates excess reducing agent is present in the ballast
water.
[0078] In another embodiment of the process for treating and
neutralizing oxidizing agents present in the ballast water, the
process further comprises measuring and recording the oxidation
reduction potential of the combined ballast water and hypochlorite
to confirm that excess oxidizing agents are present. Excess
oxidizing agents in the ballast water will ensure that no
microorganism will multiply in the ballast water tanks. In one
aspect, the process can further comprise controlling the amount of
hypochlorite generated to ensure that excess oxidizing agents are
in the ballast water.
[0079] In still another embodiment, the process comprises measuring
and recording process data. The process data can be later reviewed
to determine the effectiveness of the ballast water treatment or
the neutralization process. Examples of process data which may be
recorded include ballast water flow rate, amperage applied to the
hypochlorite electrolytic cells, cell voltage, oxidation/reduction
potential of the ballast water and side stream combined, and
oxidation/reduction potential of the ballast water prior to
discharge from the vessel.
[0080] In yet another embodiment of the process, the amount of
hypochlorite generated may be controlled by measuring the flow rate
of the ballast water and modulating the amperage applied to the
hypochlorite electrolytic cells. This method of control is also
known as flow pacing. To keep pace with the amount of ballast water
drawn onboard the vessel and its inherent microorganism content,
the amperage applied to the electrolytic cells may be proportional
to the flow rate of the ballast water.
[0081] Alternatively, the amount of hypochlorite generated may be
controlled in response to the total organic carbon content of the
ballast water. Hypochlorite generated can be generated to maintain
a weight ratio of hypochlorite to total organic carbon content.
TEST EXAMPLES
Example 1
Sodium Hypochlorite Mesocosm September 2004
[0082] The first test of the sodium hypochlorite
generator/filtration treatment system was started on Sep. 3, 2004.
The experiment included a chlorine/no filtration treatment and
chlorine with filtration treatment. The target chlorination level
was 4 mg/L. Initial chlorine levels for the filtered treatment were
3.5 mg/L and 2.95 mg/L without filtration. There were 4 mesocosms
(tanks) per treatment and 4 control mesocosms. The mesocosms were
analyzed for Total Residual Oxidant (Cl.sub.2 mg/L), culturable
heterotrophic bacteria, chlorophyll a, and zooplankton at 5, 24,
48, 120, and 240 hours following treatment.
Procedure
Total Residual Oxidant
[0083] Total Residual Oxidant (TRO) was measured as Cl.sub.2 using
a Hach.TM. Spectrophotometer and Hach.TM. Colorimeter. DPD powder
pillows were used for the analysis. TRO measurements were after the
initial fill and at all of the time points listed above. The
1500-gallon tank of raw seawater was tested for bacteria levels
before the start of the experiment. Water samples taken at the 5
time points were also tested for bacteria levels.
Culturable Bacteria
[0084] Bacteria colonies were cultured from known volumes of water
to calculate colony-forming units (CFU) per liter of water.
Colonies were cultured on petri dishes containing a growth medium
suited for marine heterotrophic bacteria. The inoculated medium was
analyzed for colony formation after a few days at room temperature
incubation.
Chlorophyll a
[0085] Water samples were also taken for chlorophyll a analysis.
Chlorophyll a is an indicator for the presence of live
phytoplankton. A known volume of sample water was filtered through
glass fiber filters with a pore size small enough to retain
phytoplankton cells. The filters were frozen for later analysis in
our Seattle laboratory. Chlorophyll a was extracted from the
filters using acetone and then analyzed for fluorescence to
determine the concentration in .mu.g/L.
Mesozooplankton
[0086] Mesozooplankton were collected in Mystery Bay, using a 110
.mu.m mesh net 1 meter diameter the morning of the test. Enough
were collected to achieve approximately 150 mesozooplankton per
liter. A Stempel pipette was used three times to collect a
randomized 5 ml sample of the mesozooplankton "soup". The
densities, counted using a dissecting scope, were used to calculate
how much of the "soup" was needed for the 1500-gallon tanks to
achieve 150 mesozooplankton per liter. The calculated amount of
soup was poured into the tank and allowed to settle for at least an
hour to let zooplankton acclimate. Three preliminary samples were
collected out of the 1500-gallon tank after mixing. These were used
to check calculation and to see the effects of the pumps. Sampling
periods for mesozooplankton were 5, 24, 48, 120, and 240 hours.
Samples were collected out of the 72-gallon mesocosms using a
1-liter Nalgene bottle after thoroughly mixing the contents of the
mesocosm. Liter sample was filtered through a 73 .mu.m sieve and
placed in counting tray. Mesozooplankton counted were placed into
one of eight generic categories and then by state; live, dead
(absolutely no response to poking) or moribund (internal movement
and no flight response to needle poke).
Results for Example 1
[0087] Total Residual Oxidant (TRO) levels declined steadily for
the duration of the experiment. (FIG. 3). TRO in the nonfiltered
test tanks dropped more than the filtered test tanks in the first 5
hours and then the TRO dissipated equally for the remaining time
points.
[0088] Bacteria were greatly reduced in both treatments and showed
minimal rebound over the 10 days of the experiment. There was a
slight rebound of bacteria in the treatment without filtration.
[0089] Chlorophyll a is an indicator of phytoplankton. In the
treated seawater, Chlorophyll a levels were at or below the
detection limit starting with the 5-hour time point and continued
to drop for both of the treatments.
[0090] In the control tanks, chlorophyll a levels declined over the
duration of the experiment, likely due to the absence of light
since all of the mesocosms were covered.
[0091] After the first treatment trial it was concluded that no
statistical difference could be found between the two treatments,
at all time points and states. The difference between the control
and treatments was highly significant. Some mesozooplankton were
still able to get through the 50 .mu.m filter, all were dead except
for 2 organisms.
Example 2
Sodium Hypochlorite Mesocosm October 2004
[0092] The second test of the sodium hypochlorite
generator/filtration treatment system was started on Oct. 12, 2004.
Two experiments were performed. The first experiment compared two
treatments, filtration/chlorination (.about.1.0 mg Cl.sub.2/L)
versus filtration only. The second experiment compared a
chlorination dose of 1.0 mg Cl.sub.2/L with a dose of 1.6 mg
Cl.sub.2/L. Each experiment included 4 mesocosms per treatment and
4 control tanks. The mesocosms were analyzed for Total Residual
Oxidant (TRO) (mg Cl.sub.2/L), culturable heterotrophic bacteria,
chlorophyll a, and zooplankton at 5, 24, 48, and 240 hours
following treatment. Culturable phytoplankton was enumerated in the
first experiment. Samples were also collected at 5 hours for
nutrient and total organic carbon (TOC) analysis. The temperature
in the mesocosms fluctuated between 12.0.degree. C. and
14.0.degree. C.
Procedure
[0093] The procedure for Example 2 was the similar to the procedure
used in Example 1 except for the phytoplankton technique.
Phytoplankton Most Probable Number Technique
[0094] During the first October experiment we tested the use of the
Most Probable Number (MPN) technique, a dilution based culture
method, to enumerate viable phytoplankton cells after treatment.
Phytoplankton samples were collected from each treatment (control,
filtered, and filtered and chlorinated) at four time points (5, 24,
48, and 240 hours). Each sample was filtered onto a glass fiber
filter, and this filter (containing phytoplankton cells) was used
to inoculate phytoplankton growth medium (f/2) over a dilution
series. The inoculations were then transferred to incubators set to
optimize growth (12:12 light:dark cycle, 13.degree. C.). The
pattern of growth over the dilution series allows for a calculation
of the MPN, an estimate of the number of viable phytoplankton cells
per L. Using this technique we can determine the effectiveness of a
particular treatment at reducing the number of viable phytoplankton
by comparing control and treatment abundance estimates.
Results
[0095] Total Residual Oxidant--The goal of the filtration with
chlorination treatment was to dose to an initial TRO level between
0.5 and 1.0 mg Cl.sub.2/L. The actual dose achieved had an average
TRO of 1.11 mg Cl.sub.2/L at the initial filling of the mesocosms
(FIG. 4). This TRO declined 54% in the first 5 hours to a TRO of
0.51 mg Cl.sub.2/L. TRO degradation slowed with time and completely
disappeared by 240 hours. TRO for the chlorination only treatments
of the second experiment showed a similar degradation curve. The
goal of the chlorination only treatments was to dose with an
initial TRO of 1.0 and 1.5 mg Cl.sub.2/L. The actual dose averages
were 0.94 mg Cl.sub.2/L and 1.61 mg Cl.sub.2/L TRO. Highest percent
reduction of TRO occurred with the lowest TRO dose.
[0096] Culturable Bacteria were initially reduced in all 3 of the
chlorinated treatments at 5 hours. Although slightly suppressed,
bacteria in the chlorinated treatments rebounded to levels higher
than the controls by 240 hours. The filtration only treatment
showed negligible reduction in bacteria at 5 hours with levels
equal to the control treatment at subsequent treatments.
[0097] Mesozooplankton--Chlorine plus filtration had an immediate
effect upon the zooplankton, reaching a 95% mortality at 5 hours
and complete mortality at 24 hours. By 48 hours the high chlorine
treatment results were similar to the filtration with chlorination
treatment. At 5 hours the filtration with chlorine treatment had no
live organisms per L, there were only 1-2 moribund organisms per L
at this time. The percent dead of the two controls were similar
except for the 48 hours sample.
[0098] Chlorophyll a is an indicator of phytoplankton biomass. The
filtration with chlorination treatment showed the greatest initial
reduction in chlorophyll a compared with the chlorination only
treatments. At 5 hours chlorophyll a levels were reduced by 98% for
the filtration with chlorination treatment when compared to the
control treatment. The filtration only treatment showed slight
reduction when compared with the control treatment. In the control
tanks, chlorophyll a declined over the duration of the experiment,
likely due to the absence of light since all of the mesocosms were
covered.
[0099] The phytoplankton culture (MPN) technique shows that the
number of viable phytoplankton cells was greatly reduced by
filtration compared to the control. Some of the inoculations showed
positive growth over the entire series of dilutions, thus allowing
us to only estimate the MPN as greater than or equal to result. It
appears that filtration removes as much as 50% of the viable
phytoplankton from the mesocosms. The reduction of viable
phytoplankton was more dramatic when water was treated with the
combined filtration and chlorination system. Numbers of viable
phytoplankton were reduced 99% by this treatment compared to the
control.
[0100] Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made herein without departing
from the spirit and scope of the invention as defined by the
appended claims.
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