Content uploaded by Jeffery Cordell
Author content
All content in this area was uploaded by Jeffery Cordell on Oct 01, 2015
Content may be subject to copyright.
Electrolytic Sodium Hypochlorite System for Treatment of
Ballast Water
Rudolf C. Matousek,*David W. Hill,* Russell P. Herwig,
†
Jeffery R. Cordell,
†
Bryan C. Nielsen,
†
Nissa C. Ferm,
†
David J. Lawrence,
†
and Jake C. Perrins
†
*Severn Trent DeNora, Sugar Land, Texas, USA
†
University of Washington, Seattle, Washington, USA
The potential problems of organisms introduced by ballast water are well docu-
mented. In other settings, electrolytic generation of sodium hypochlorite from sea-
water has proven to be a simple and safe method of handling and injecting a biocide
into water. After the hypochlorite oxidizes organisms, it reverts back to the chloride
ion. Mesocosm-scale testing of this technology combined with filtration, using organ-
isms from Puget Sound, Washington, demonstrated that hypochlorite generation and
use may be a viable method to eliminate aquatic nuisance species from ballast water
while minimizing disinfection byproducts and residual toxicity. These experiments
were conducted at the U.S. Geological Survey Marine Field Station on Marrowstone
Island, Washington. Results from the first set of studies of the system showed that
hypochlorite levels greater than 3.0 ppm hypochlorite with or without filtration reduced
bacteria by more than 99.999%, reduced phytoplankton by more than 99%, and
reduced mesozooplankton by more than 99%. Filtration improved efficacy only when
hypochlorite concentration was initially less than 1.5 ppm.
1. Introduction
1.1 Regulations
THE MARINE ENVIRONMENT PROTECTION COMMITTEE (MEPC) of
the International Maritime Organization met in February 2004.
The committee adopted a new world Ballast Water Convention
that will enter into force 12 months after ratification by 30 member
states representing 35% of the world’s gross tonnage. The Con-
vention is divided into articles and, more importantly for the de-
velopment of ballast water treatment technologies, an annex that
includes technical standards and requirements in the regulations
for the control and management of ship ballast. All ships, includ-
ing submersibles, floating craft, floating storage units (FSUs), and
floating production, storage, and offloading units (FPSOs), are to
manage their ballast water in accordance with an approved ballast
water management plan and record such management in a ballast
water record book. All ships greater than or equal to 400 gt are to
be surveyed (initial, annual intermediate, and renewal) and
certificated (not exceeding 5 years). Table 1 summarizes the
implementation schedule of the type of treatment required accord-
ing to the age of ship and its ballast capacity as per the provi-
sions of the Convention (International Maritime Organization
2004).
Indicator microbe concentrations shall not exceed:
• Toxicogenic Vibrio cholerae: 1 colony forming unit (cfu)
per 100 ml
•Escherichia coli: 250 cfu per 100 ml
• Intestinal Enterococci: 100 cfu per 100 ml.
Ballast water exchange is to take place as follows:
• At least 200 nautical miles from the nearest land and 200
m water depth OR
• In the event throughout the intended route the sea area
does not afford the above characteristics, in a sea area desig-
nated by the port state. There may be a need to alter the ship’s
intended route to exchange ballast in the designated area.
States may establish additional ballast water management mea-
sures for ships to meet based on guidelines, which remain to be
Presented at the 2005 Ship Production Symposium, Society of Naval Ar-
chitects and Marine Engineers, October 19 to 21, Houston, Texas.
Journal of Ship Production, Vol. 22, No. 3, August 2006, pp. 160–171
160 AUGUST 2006 8756/1417/06/2203-0160$00.49/0 JOURNAL OF SHIP PRODUCTION
developed. The MEPC shall undertake a review of the Ballast
Water Standards no later than 2006 and is to include an assessment
of the technologies available that achieve the standard. As part of
the assessment, the MEPC requires significant documentation of
the system, with efficacy data for both land-based and shipboard
tests. Criteria for such testing have been established and outlined
in MEPC document MEPC 52/WP.7 titled “Guidelines for Ap-
proval of Ballast Water Management Systems.”
As a result of these regulations, there is a need for a proven,
viable, cost-effective ballast water treatment system by 2007. This
will allow ship designers to specify and incorporate such devices
into ships that begin construction after January 1, 2009. This paper
is the summary of land-based work on a ballast water treatment
(BWT) system utilizing on-site hypochlorite generation.
1.2. Ballast water management strategies
1.2.1. Open-ocean ballast water exchange. Most environmental
scientists agree that ballast water that is exchanged in the open
seas presents less of an ecological threat or risk to the receiving
waters. The question is whether the threat has been reduced to an
acceptable level. As presently engineered and practiced, reballast-
ing does not exchange 100% of the ballast water or remove all of
the sediments that are found in ballast water tanks. The amount of
the exchange varies from ship to ship. Older ships tend to ex-
change less efficiently than newer ships. Dickman and Zhang
(1999) examined four containerships that took on ballast in
Mexico and discharged 21 days later in Hong Kong. After this
period, few of the dinoflagellate and diatom species taken on in
Mexico were alive in the ballast water in Hong Kong. Five ships
that reballasted in the open ocean reduced the diatom and dino-
flagellate populations by 48%. They concluded from results of this
and previous study that older vessels were less effective in remov-
ing diatom and dinoflagellate species than newer ships. The reason
could be that the reballasting design of older ships was less effi-
cient in removing water and sediments located near the bottom of
the ballast tanks and that the bottom water is associated with a
large number of resting cysts and cells. Ships sampled in Puget
Sound by the University of Washington’s ballast water team
showed that even in ships that reported open ocean exchange, up
to 50% of the organisms were nonnative to the northeastern Pa-
cific.
1.2.2. Ballast water treatment technologies. A variety of treat-
ment technologies are suggested for the removal or reduction of
organisms that are found in ballast water. The challenge is to
develop a technology that is effective against a variety of biologi-
cal taxa and that is capable of quickly treating the very large
volumes of ballast water that are associated with large ships.
Treatment technologies may be developed for on-board or at-port
applications. Technologies that have received most of the recent
consideration include (1) cyclonic separation, (2) heat treatment,
(3) electric pulse, (4) ultraviolet light, (5) filtration, and (6) bio-
cides. These technologies were listed and reviewed in the National
Research Council publication “Stemming the Tide: Controlling
Introductions of Nonindigenous Species by Ships’Ballast Water”
(National Research Council 1996). We briefly review the pro-
posed technologies and provide some comment.
Cyclonic separation. A more sophisticated and more recently
developed technology involves cyclonic separation. This is nor-
mally accomplished using hydrocyclones. If properly designed
and applied, hydrocyclones will require less pump pressure than
screen filters and will allow separation of sediments and other
suspended solids to approximately 20 µm. Hydrocyclones are lim-
ited, however, to separating solids with a specific gravity greater
than, or less than, water. Many types of organisms (e.g., bacteria
and other microorganisms) will not be separated from the water
since their specific gravity is extremely close to seawater.
Ultraviolet light. In close contact, ultraviolet (UV) light treat-
ment is effective in killing non–spore-forming microorganisms. It
does not appear effective in inactivating higher organisms or the
cyst or resting stages of protozoa. Ultraviolet light was not effec-
tive in totally eliminating dinoflagellates. Montani et al. (1995)
found that after exposure to ultraviolet light for 2 hours, the ger-
mination of Chattonella sp. cysts decreased to 6% of the control,
whereas germination of cysts of other species of dinoflagellates
(Alexandrium sp. and Gymnodinium sp.) was more than 40% of
the controls. The University of Washington research team has
performed controlled mesocosm tests at the Marrowstone Marine
Field Station in which Puget Sound seawater was amended with
additional zooplankton. The amended seawater was exposed to
moderate levels of UV light. They found that zooplankton mor-
tality was delayed and did not immediately occur. The microbial
populations were quickly reduced in number following exposure
to the UV light but rebounded to their original levels within a few
days.
Heat treatment. The use of waste heat from the ship’s propul-
sion and service cooling is an attractive option for the inactivation
of organisms in ballast water. No chemical byproducts or residuals
Table 1 Ballast water treatment implementation schedule
Ballast Capacity (m
3
) Construction Date 2009 2010 2011 2012 2013 2014 2015 2016 2017
<1,500 <2009 D1 or D2 D2
>2009 D2
>1,500 <2009 D1 or D2 D2
<5,000 >2009 D2
>5,000 <2012 D1 or D2
>2012 D2
D1 ⳱ballast water exchange (95% volumetric exchange) or pumping through three times the volume of each tank.
D2 ⳱ballast water treatment systems approved by the Administration with treatment efficacy of:
+ Not more than 10 viable organisms per m
3
>50 m.
+ Not more than 10 viable organisms per milliliter >10 and <50 m.
AUGUST 2006 JOURNAL OF SHIP PRODUCTION 161
would be associated with the discharge of heat-treated ballast
water. A number of factors will limit the practicality of thermal
treatment primarily related to the volume of water that is associ-
ated with large vessels and the amount of energy required to heat
the volume. Thermal treatment may be more applicable to ballast
water originating from warmer environments. Heat required for
thermal treatment could be reduced where water temperatures are
at tropical or summer levels (30 deg C or higher). The heat loss to
the ambient waters outside of the hull must be considered. Dif-
ferent types of organisms or organisms from different parts of the
world may have different sensitivities to heat. A few recent studies
suggest that heating ballast water is the best method for killing a
variety of higher organisms and microorganisms that are found in
ballast water. Rigby et al. (1999) showed how a cost-effective
heating technique using waste heat from a ship engine could be
used to kill many unwanted organisms. In an ocean trial, heated
water flushed through one of the ballast tanks resulted in the
destruction of all zooplankton with very limited survival of the
original phytoplankton.
Electric pulse. Small-scale experiments have been performed
by applying electrical voltages in the 15 to 45 kV range with pulse
duration of 1 µs. Large energy sources would be required for
systems capable of treating large volumes of ballast water (Na-
tional Research Council 1996).
Filtration. The physical separation and removal of organisms
can be accomplished during ballasting operations using a ship-
board filtration system. Some would argue that this technology is
the most promising choice. Filtering ballast water as it is loaded is
an attractive option since it would minimize the introduction of
unwanted organisms. The options for onboard filtration systems
are either mesh strainers or deep media filtration. Many problems
associated with a strainer technology have been solved with the
development of commercially available continuously cleaned
screening systems. Media filters are attractive in principal because
small-size particles can be removed, but these filters are most
likely unrealistic for on-board treatment of ballast water because
of the large footprint that would be required. The primary disad-
vantage of the strainer filters is that many organisms are smaller
than strainers and would pass through the treatment system. A
study for the Canadian Coast Guard (1992) concluded that the
physical removal of organisms by filtering may be an effective
stand-alone treatment process or may be used in conjunction with
other technologies, such as chemical treatment or UV sterilization.
Flow-through centrifugation systems can separate particles prior
to filtering to reduce filter clogging.
Biocides. The addition of chemicals that would kill or inactivate
a variety of organisms found in ballast water is an attractive treat-
ment technology because of the ease of application. A biocide
could simply be added to the ballast tank and allowed to react for
a specified period. Biocides are among the most widely used in-
dustrial chemicals, and there is a large body of knowledge about
their use in wastewater treatment. If similar concentrations were
required to inactivate organisms found in ballast water, then a
large ship would need to carry only a few cubic meters of biocide
per voyage. The use of biocides for ballast water treatment has
been rejected by some for several reasons, including the reluctance
to add toxic chemicals to water that may be discharged back into
the ocean, the unknown effectiveness of biocides against target
organisms, and compliance with discharge regulations around the
world. Oxidizing biocides such as chlorine, chlorine salts, and
ozone have been used for decades in a variety of sanitizing appli-
cations. Ozone is a strong oxidizing agent used for treatment of
potable and industrial waters. With the increasing environmental
concern associated with the use of chlorine, ozone has received
greater attention in recent years. Ozone is an unstable gas that
must be generated as needed, and some reviewers have concluded
that ozone may not be practical for shipboard use (National Re-
search Council 1996). Along with generation, ozone efficacy is a
problem due to the gas–liquid contact requiring elaborate diffu-
sion equipment. In salt water, ozone produces many of the similar
residual compounds as chlorination. Nonoxidizing biocides such
as glutaraldehyde or vitamin K have also have been suggested.
2. Electrochlorination
2.1. Background
Seawater (normally between 15 and 35 grams/liter) or other
water containing NaCl may be used to generate a disinfecting
solution containing chlorine by passing a direct electrical current
through the solution. On-site generation of hypochlorite from sea-
water has been used for over 25 years. These systems can be
purchased as completely skid-mounted systems that generate so-
dium hypochlorite from seawater. These systems are used in re-
fining, petrochemical power plants, offshore drilling production,
and marine applications around the world. Systems can be scaled
to the appropriate size depending on the quantity of hypochlorite
required.
The type of electrolytic cell commonly used in these marine and
offshore applications is a “tube within a tube.”A cell consists of
one anode, one cathode, and one bipolar tube with the necessary
ancillary hardware to facilitate assembly. The outer anode and
cathode are manufactured from seamless titanium pipe. The anode
surface is coated with proprietary precious metal oxides, primarily
ruthenium and iridium. Seawater enters one end of the cell and
passes between the cathode, the anode, and bipolar tube annular
spaces. When direct current is applied to the cell, sodium hypo-
chlorite results. One cell can produce up to 5.5 kg/day, and a
maximum of 12 cells can be connected in series for a capacity of
65 kg/day per train.
In some applications, such as ballast water treatment, a dechlo-
rination step can be added to the process. This requires adding a
reducing agent, such as sodium sulfite, to the end of the system to
neutralize any residual chlorine at the point of discharge. The end
result is a nontoxic stream with no free chlorine.
2.2. Chemistry
The process is based on the partial electrolysis of NaCl present
in seawater as it flows through an unseparated electrolytic cell.
The resulting solution exiting the cell is a mixture of seawater,
sodium hypochlorite (hypo), hydrogen gas, and hypochlorous
acid. Electrolysis of sodium chloride solution (seawater in this
study) is the passage of direct current between an anode (positive
pole) and a cathode (negative pole) to separate salt and water into
their basic elements. Chlorine generated at the anode immediately
goes through chemical reactions to form sodium hypochlorite and
hypochlorous acid. Reactions are shown below:
Cl
−
→Cl
2
(aq) + 2e
−
Eo ⳱1.396 V (1)
162 AUGUST 2006 JOURNAL OF SHIP PRODUCTION
which is hydrolyzed in solution to form hypochlorous acid:
Cl
2
+2H
2
O→2HOCl + 2H
+
(2)
Hypochlorous acid dissociates to hypochlorite at alkaline pH levels:
HOCl →OCl
−
+H
+
pKa =7.5 (3)
In seawater bromide ions are present, together with a range of
inorganic cations as well as possibly ammonia and a variety of
organic compounds. The reaction of molecular chlorine or hypo-
chlorite ions with ammonia or amino compounds leads to the
disinfectants, and they react to destroy bacteria and microorgan-
isms in the water just as do chlorine, hypochlorous acid, and
hypochlorite ions. The rapid oxidation of bromide ions will also
occur and (as with chlorine) in the aqueous environment form
hypobromous acid (HOBr) and hypobromite ions (OBr
−
). These
reactions will also be equilibrium processes, dependent on tem-
perature and pH. Note also that brominated species will react with
ammonia and/or amino compounds if present in the water, just like
the chlorine analogues.
Hydrogen and hydroxides are formed at the cathode, the hy-
drogen forms a gas and is vented, and the hydroxide aids in the
formation of sodium hypobromite and increases the exit stream pH
to approximately 8.5. This reaction is shown as follows:
2H
2
O+2e
−
→H
2
(g) +2OH
−
Eo =−0.828 V (4)
Because the electrolytic cell used for this application is unsepa-
rated, the reactants at both anode and cathode can further react to
form the respective end products shown in the overall electro-
chemical and chemical reaction as follows:
NaCl +H
+
+Br
−
+2e →NaOBr +H
2
+Cl
−
Salt +Water +Energy →Sodium Hypochlorite +Hydrogen
(5)
2.3. Disinfection by-products
Disinfecting agents, such as chlorine, ozone, chlorine dioxide,
and chloramines, react with natural organic material present in
water to produce disinfection by-products (DBPs). Most of the
research and interest in DBPs has been with drinking water. DBPs
have been known since 1974, when chloroform was identified as
DBP resulting from the chlorination of tap water. Since then,
hundreds of DBPs have been identified in drinking water. The
benefit of disinfecting drinking water is obvious, as thousands of
people died from waterborne disease before municipalities began
to disinfect drinking water, but it is also generally recognized that
it is important to minimize the formation of DBPs in drinking
water. Several DBPs have been linked to cancer in laboratory
animals, and as a result, the US Environmental Protection Agency
(EPA) has regulated some DBPs.
While we anticipate that most people will not be drinking bal-
last water and other treated seawater, we have evaluated the for-
mation of selected DBPs that may be formed following the gen-
eration of hypochlorite in seawater. Seawater is significantly
different from freshwater, not just because of the relatively high
concentration of Na
+
and Cl
-
and oftentimes higher levels of natu-
ral organic material, but also because of the presence of Br
−
(bro-
mide). The presence of this ion may lead to the formation of
bromate (BrO
3
−
), a compound that is considered a possible human
carcinogen. In the United States, bromate is regulated at 10 µg/L
(10 parts per billion) in drinking water. Seawater contains a typical
bromide concentration of 65 mg/L, so the concentration in sea-
water is significant. Therefore, bromate was one of the DBPs
measured in our research. In addition, the presence of haloacetic
acids (HAAs) and trihalomethanes (THMs) are a concern and
were measured as part of the overall study.
One other component of the ballast water treatment system is
the neutralization of the free halogen (hypochlorite and hypobro-
mite) prior to discharge from the ballast tanks. Sodium sulfite is
used, and the simplified reaction is shown below to form sodium
sulfate. As shown in the equation, neutralization occurs at one to
one molar ratio but two to one (sulfite to halogen) as a weight
ratio.
Na
2
SO
3
+Cl
2
+H
2
O–>Na
2
SO
4
+2HCl
Sodium Sulfite +Chlorine +Water –> Sodium Sulfate
+Hydrochloric Acid (6)
Typically, there are 4 g/L sulfate in seawater, and based on the
concentrations of halogen required, only 10 mg of sulfate will be
added to the discharge ballast water. Also, the amount of HCl
generated is negligible and will not change the pH of the discharge
ballast water.
3. Pilot electrochlorination ballast water treatment
3.1. Background
The University of Washington School of Aquatic and Fishery
Sciences performed third-party verification tests on the Severn
Trent DeNora’s Electrochlorination Ballast Water Treatment
(BWT) System (BalPure; Severn Trent DeNora, Sugar Land, TX).
The pilot plant system consisted of two 5.7 m
3
(1,500 gallon) raw
seawater holding tanks. The water was pumped through a 50-m
self-cleaning filter. When the pressure drop reached a preset value,
the filter was automatically back flushed while continuing to op-
erate. A stream volume of roughly 10% of the inlet flow to the
filter was generated, containing the removed organisms and solid
contaminants. During a ballast water operation, this stream would
be discharged overboard. For purposes of this test, the stream was
collected.
After the water was filtered, a side stream was fed to the elec-
trolytic cell, where oxidizers were generated. This oxidized stream
was then injected and mixed with the main stream. After the
hypochlorite stream was mixed with the mainstream, the water
was sampled and the free halogens were measured and recorded.
This on-line real-time free halogen value was used to automati-
cally adjust the amount of hypochlorite generated for the ballast
water treatment. Based on previous lab tests, the expected required
dosage after filtration ranged from 1 ppm up to 5 ppm.
Once the water was treated, it was placed in replicate dark
mesocosms. This step was analogous to ballast water in ballast
tank conditions. After 7 to 14 days of storage, the seawater was
monitored before it was “discharged.”A dehalogenation agent,
such as sodium sulfite, was injected into the water to react or
neutralize any free halogens. A schematic of the pilot process is
shown in Fig. 1.
AUGUST 2006 JOURNAL OF SHIP PRODUCTION 163
3.2. University of Washington test program
3.2.1. Test site. During the past 4 years, the University of Wash-
ington has been conducting ballast water treatment technology
testing at the USGS Marrowstone Island Marine Field Station. To
date, experiments have been conducted with Puget Sound seawa-
ter amended with locally obtained zooplankton greater than
73 m.
The Marrowstone Marine Field Station is located on Marrow-
stone Island at the northwestern entrance to Puget Sound, Wash-
ington, USA. The station is a former US Coast Guard lighthouse,
acquired by USGS in 1974. Besides the old lighthouse keeper’s
residence, the station has a laboratory/office building, two wet labs
with constant seawater flow, several large tanks, many smaller
tanks, a pump house, and shop. Approximately $4 million was
invested in construction during the 1990s. Seawater for the labo-
ratory is drawn directly from northern Puget Sound. Seawater
effluent from the laboratories can be chlorinated and released into
a lagoon, and the station has the required permits for releasing
treated seawater. Presently, seawater can be pumped at a maxi-
mum rate of 1,500 liters (400 gallons) per minute. The station’s
filtration system was bypassed for obtaining untreated seawater,
Fig. 1 Pilot electrochlorination treatment system
164 AUGUST 2006 JOURNAL OF SHIP PRODUCTION
and large tanks were spiked with additional zooplankton before
passage through the electrolytic seawater ballast water treatment
equipment.
3.2.2. Research plan. The specific objectives of the research
were to evaluate the efficacy of the filtration and hypochlorite
treatment system both with and without the filtration system.
For the mesocosm experiments (see below), the University of
Washington research team conducted experiments with the ballast
water treatment system to determine the viability of Puget Sound
zooplankton, phytoplankton, and microorganisms and measure the
concentration of selected disinfectant by-products after treatment
with the BALPURE.
3.2.3. Experimental design and sampling. Four replicate 280
liter (75 gallon) circular tanks were used for each treatment and
control condition. The Severn Trent De Nora treatment system
incorporates two steps, a filtration step that is followed by the
addition of generated hypochlorite. The efficacy of the system was
examined separately for each component, and for the filtration and
chlorine components used together. For the control, seawater
passed through the system without applying the filtration and chlo-
rination steps. Because pumps may destroy some of the zooplank-
ton present in the seawater, separate controls with and without the
pump/flow network were used, to determine mortality caused by
the pumping system versus that caused by the treatment.
To increase the sensitivity of the mesozooplankton analyses,
additional mesozooplankton were mixed with ambient Puget
Sound seawater for the mesocosm experiments. Mesozooplankton
were collected in Kilisut Harbor, Washington, usinga1mdiam-
eter, 110 m mesh net, approximately 2 hours prior to the start of
the mesocosm experiment. Mesozooplankton were added to the
1,500 gallon supply tank to obtain a density of approximately 150
to 200 individual organisms per liter. A Hensen-Stempel pipet was
used to collect three randomized 5 ml samples of the meso-
zooplankton concentrate from the collecting vessel after vigorous
stirring. The counts from these subsamples were used to calculate
how much of the concentrate was needed to achieve 150 to 200
mesozooplankton per liter for the start of the experiment and for
restocking mesocosms after the dechlorination step. The appro-
priate number of zooplankton were mixed with the 1,500 gallon
supply tank and allowed to acclimate for at least 1 hour before
they were pumped through the treatment system.
After thoroughly mixing the contents of mesocosms, plankton
samples were collected using 1 L Nalgene wide-mouth bottles.
Each sample was filtered through a 73 m sieve and placed in a
counting tray. Samples were observed with a stereomicroscope.
Each organism observed was classified into one of eight taxo-
nomic groups and categorized as live (vigorous movement or es-
cape response when probed), dead (no movement observed, no
response to probing), or moribund (internal and/or external move-
ment observed, but no escape response to probing).
In some experiments, after performing the dechlorination step at
24 hours, the contents of the tanks were pumped through a 73 m
mesh screen to remove any remaining live and dead meso-
zooplankton. The filtered mesocosm water was dosed with fresh
mesozooplankton concentrate.
Hypochlorite was tested at a range of concentrations, a high
value near 5 ppm and a low value near 1 ppm. This was done to
begin to understand the minimum amount of hypochlorite needed
to achieve proposed discharge standards. Each mesocosm was
sampled at standard intervals over the 10 day tests. Samples were
analyzed for viability of zooplankton, phytoplankton, and bacteria.
Mesocosm experiments with the Severn Trent De Nora system
were run and are planned during different seasons (i.e., fall, win-
ter, spring, and summer) to capture a wide range of organisms and
environmental conditions. We describe here preliminary results
from a portion of our mesocosm experiments that are in progress.
3.3. Monitoring methods
The change in viable microorganisms and zooplankton before
and after passage through the Severn Trent De Nora system were
evaluated using several methods. Since the chemical and physical
characteristics of the ballast water influence the effectiveness of
treatment, chemical and physical parameters were also measured.
Table 2 lists the monitoring methods that were used. Each unit of
the system was tested separately and in combination (filtration,
hypochlorite, sulfite neutralization).
3.3.1. Hypochlorite and by-product chemistries. Treated sea-
water samples were collected to determine the concentration of the
following disinfectant-related compounds: (1) total residual chlo-
rine (or total residual oxidant [TRO]), (2) trihalomethanes
(THMs), (3) haloacetic acids (HAAs), (4) bromate. TRO was mea-
sured at the site as Cl
2
using a Hach Colorimeter (The Hach
Company, Loveland, CO). DPD powder pillows (Hach) were used
for the analysis.
The DBPs analyzed were trihalomethanes (THMs), five halo-
acetic acids (HAA5), and bromate. Chlorite analysis was not per-
formed in our study. The THMs analyzed, using USEPA Method
524.2, were chloroform, bromodichloromethane, dibromochloro-
methane, and bromoform. In addition to the specific THMs, the
total THM (TTHM) was also determined. The HAA5s analyzed,
using US EPA Method 552.2, were monochloroacetic acid, di-
chloroacetic acid, trichloroacetic acid, bromoacetic acid, and di-
bromoacetic acid. Bromochloroacetic acid was also determined.
Bromate analysis was performed using ion chromatography, using
USEPA Method 317. Samples were collected from one represen-
tative tank per treatment and control. Samples were collected in
glass containers provided by the analytical laboratories and refrig-
erated until shipment. Samples were packed with ice in coolers
Table 2 Methods used to evaluate treated and control seawater
used in mesocosm experiments at the USGS Marine Field Station
at Marrowstone
General chemical and physical
parameters
Selected macrofaunal identification
and viability
pH Zooplankton
Temperature
Salinity Microbiological methods
Nutrients Total culturable bacteria
Total organic carbon Chlorophyll a
Hypochlorite and by-product chemistry
Total residual chlorine or total
residual oxidant (TRO)
Trihalomethanes (THM)
Haloacetic acids
Bromate
Toxicity assay
Whole effluent toxicity (WET)
bioassay
AUGUST 2006 JOURNAL OF SHIP PRODUCTION 165
provided and shipped by overnight express service to arrive at the
analytical laboratories after the first samples were collected from
the mesocosm experiment within 7 days. To follow US EPA meth-
ods, analyses for THMs and HAAs need to be performed within
14 days of collection and for bromates within 28 days. Bromate
samples were sent to and analyzed by Nova Chem Laboratories,
Inc. (Oxford, Ohio). THM and HAA samples were sent to and
analyzed by Edge Analytical, Inc. (Burlington, Washington). Both
of these companies are certified contract laboratories.
3.3.2. Culturable bacteria. Water samples collected were enu-
merated for culturable bacteria. Bacteria were enumerated as
colony forming units (CFU) per liter of water. Colonies were
cultured on petri dishes containing a growth medium suited for
marine heterotrophic bacteria, called marine R2A agar. The in-
oculated medium was analyzed for colony formation after 5 days
of room temperature incubation.
3.3.3. Chlorophyll a.Chlorophyll awas measured as an indicator
of phytoplankton biomass. Water was filtered through glass fiber
filters with a pore size small enough to retain phytoplankton cells.
Chlorophyll awas extracted from the filters using acetone and
then analyzed for fluorescence to determine the concentration in
g/L (Holm-Hansen & Reimann 1978). Although chlorophyll a
analysis provides an assessment of the reduction in phytoplankton
concentration after treatment, it does not provide a direct measure
of the viability of phytoplankton after treatment.
4. Test results
Three separate tests of the BALPURE were conducted over a
6-month period in 2004. The test conditions and results are de-
scribed below.
4.1. Test 1
4.1.1. Conditions. The first experiment was done with and with-
out filtration at an initial chlorine concentration of 3.5 mg/L.
Sample sets were taken at 0, 5, 24, 48, 120, 240 hours following
treatment and analyzed for total residual oxidant (TRO), cultur-
able heterotrophic bacteria, chlorophyll a, and zooplankton viabil-
ity. This provided the benchmark for future studies.
4.1.2. Results and discussion. TRO levels declined steadily
throughout the experiment (Fig. 2). TRO in the nonfiltered test
tanks dropped more than in the filtered test tanks during the first
5 hours. This was a result of organisms being removed by the
filtering step and creating a smaller oxidant demand. After the
initial drop, the rate of TRO decay over the next 10 days was the
same for both test conditions.
Bacteria were greatly reduced in both treatments and showed
minimal rebound over the 10 day experimental period (Fig. 3).
Statistically there was no difference in number of bacteria for
filtered or unfiltered conditions.
Chlorophyll ais an indicator of phytoplankton biomass. In the
treated seawater, chlorophyll alevels were at or below the detec-
tion limit beginning with the sample 5 hours after treatment (Fig.
4). Chlorophyll alevels declined over time in the control tanks
because the experiments were conducted in the dark.
For the mesozooplankton, there was no significant difference
between the results for filtered and unfiltered tests (Fig. 5). There
were no living organisms in the unfiltered tanks and only one live
polychaete larva in the filtered tanks.
4.2. Test 2
4.2.1. Conditions. The second test was composed of two experi-
ments, consisting of comparing chlorination without filtration at
Fig. 2 Total residual oxidant (mg Cl
2
/L)
166 AUGUST 2006 JOURNAL OF SHIP PRODUCTION
the relatively low dose rates of 1.0 ppm and 1.6 ppm. Sampling
frequency and analysis were the same as in Test 1.
4.2.2. Results and discussion. The TRO level dropped quickly
by approximately 0.6 ppm in the first 5 hours and 1.0 ppm in the
first 24 hours. Higher residual TRO persisted in both the higher
chlorine dose treatment and the filtration treatment (Fig. 6). TRO
disappeared in all treatments by 10 days.
Bacteria amounts in the first experiment were reduced only
when chlorine was added. Because the amount of chlorine added
was so small, the bacteria grew back to levels equal to those before
treatment. In Test 2, the chlorine levels of 1.5 and 1.0 ppm were
insufficient to keep bacteria from growing after approximately 4
days. But the rate of bacteria growth was inversely proportional to
the initial chlorine concentration. This is shown in Figs. 7 and 8.
In other words, a minimum level of TRO needs to be maintained
to prevent bacteria from multiplying.
Chlorophyll ais an indicator of phytoplankton biomass. As
observed in Test 1, control samples had approximately 12 g/L of
chlorophyll a, the filtered-only sample 7 g/L, and filtration com-
bined with 1.0 ppm chlorine eliminated all chlorophyll a.Inex-
periment 2, even with only 1.0 ppm chlorine and no filtration,
chlorophyll awas at the detection limit within 48 hours.
In this experiment, densities of approximately 200 individual
organisms per liter were used. Fifty m filtration reduced con-
centrations to approximately 35 live individual organisms per liter
Fig. 4 Chlorophyll a(µg/L)
Fig. 3 Culturable heterotrophic bacteria
AUGUST 2006 JOURNAL OF SHIP PRODUCTION 167
(greater than IMO convention). Addition of 1.0 ppm chlorine re-
duced the count to less than 10, and 1.0 ppm combined with
filtration eliminated all live zooplankton.
4.3. Test 3
4.3.1. Conditions. The primary objective of Test 3 was to mea-
sure disinfection by-products and to examine the residual toxicity
of neutralized seawater after chlorination. The benchmark analy-
ses, done in Test 1 and Test 2, were conducted. A chlorination
level of approximately 3.5 ppm was used to maximize disinfection
by-products. Filtration was not used in this experiment. One half
of the test set (Group B) was neutralized with sodium bisulfite
after 24 hours to simulate neutralization of ballast discharge. Ex-
cess sodium bisulfite was added at a sulfite-to-TRO ratio of 3:1
(10.5 mg NaHSO
3
/L) to ensure that no residual sodium hypochlo-
rite or TRO remained in the water. To evaluate the treated sea-
water for residual toxicity, the neutralized seawater was filtered
with a 73 m filter to remove dead organisms and was replenished
Fig. 6 Total residual oxidant (mg Cl
2
/L)
Fig. 5 Live mesozooplankton per liter
168 AUGUST 2006 JOURNAL OF SHIP PRODUCTION
with new phytoplankton and zooplankton to approximately the
original densities.
4.3.2. Results and discussion. Similar to previous tests, control
groups with and without bisulfite had no decrease in bacteria
levels or large changes in phytoplankton or zooplankton.
Similar to previous tests, the TRO level dropped approximately
0.5 ppm in the first 5 hours after treatment, dropped approximately
1.0 ppm during the first 24 hours, and then slowly decreased. In
mesocosms with added bisulfite, TRO dropped immediately from
2.5 ppm to 0 ppm.
Bacteria counts were greatly reduced in the treatment tanks by
5 hours compared to control tanks. The mortality pattern was
identical, as shown in Fig. 2, as long as there was a residual TRO
present in the tank. Those tanks that were neutralized in Group B
(TRO at 0.0 ppm) showed immediate bacteria growth to control
levels that were sustained for the remainder of the test. This sug-
gests that the dechlorinated water was no longer toxic or inhibitory
Fig. 7 Experiment 1: culturable heterotrophic bacteria
Fig. 8 Experiment 2: culturable heterotrophic bacteria
AUGUST 2006 JOURNAL OF SHIP PRODUCTION 169
to bacteria following the addition of sodium bisulfite. The number
of culturable bacteria increased from 10 to 10
6
CFU/L.
After chlorination, chlorophyll aconcentrations in treatment
tanks ranged from 0.00 to 0.02 g/L, indicating an almost total
eradication of phytoplankton resulting from chlorination. Again,
the pattern was similar to Fig. 4. For Group B and after neutral-
ization and back addition, the chlorophyll alevels were at and
sustained at control group concentrations. This indicated a non-
toxic environment for phytoplankton.
Zooplankton showed a 98% to 100% mortality rate when
treated with 3.5 ppm chlorine compared to controls, similar to Test
2. After dechlorination and restocking of Group B, new zooplank-
ton survived as well as in control samples.
Disinfection by-product analysis was performed throughout the
mesocosm testing. Although there are no DBP regulations for
ballast water, regulated drinking water DBPs and their US EPA
maximum contaminant level (MCL) standards were used as a
guide for the DBP analysis. Drinking water MCLs for the tested
by-products are 0.080 mg/L for the total trihalomethanes (TTHM),
0.060 mg/L for five selected haloacetic acids (HAA5), and 0.010
mg/L for bromate. In Test 3, TTHM and HAA5 levels were below
drinking water MCL in all samples. Bromochloroacetic acid is not
an HAA5 regulated under current drinking water standards.
Results for the various disinfection by-product concentrations
are listed in Tables 3, 4, and 5. The results indicate that the DBP
created in treating ballast water are below the limits for all three
components of disinfection by-products for drinking water.
5. Conclusions
Several conclusions can be made from the research completed
by the University of Washington:
1. The BALPURE Electrooxidation System, when used to treat
incoming seawater, is a promising treatment technology to
meet the proposed IMO standards.
2. Dechlorinated ballast water effluent (discharge) was not
toxic to Puget Sound organisms.
3. Disinfection by-products that were formed during the tests
Table 3 Trihalomethane results
Time (h) Treatment
Trihalomethanes (g/L)
Chloroform Bromoform Bromodichloromethane Chlorodibromomethane Total THM (TTHM)
0 Control <0.5 <0.5 <0.5 <0.5 <0.5
0 Treatment B <0.5 43.1 <0.5 1.1 44.2
24 Treatment A <0.5 67.7 <0.5 1.8 69.5
24 Treatment B NA NA NA NA NA
27 Treatment B <0.5 70.6 <0.5 1.9 72.5
48 Treatment B <0.5 68.1 <0.5 1.8 69.9
48 Treatment A <0.5 68.0 <0.5 2.2 70.2
Detection limits 0.5 0.5 0.5 0.5 0.5
NA ⳱not analyzed.
Table 4 Haloacetic acids results
Time (h) Treatment
Haloacetic Acids (g/L)
DBAA MBAA MCAA DCAA TCAA HAA5 BCAA
0 Control <1.0 <1.0 <2.0 <1.0 <1.0 <1.0 <1.0
0 Treatment B 1.9 <1.0 <2.0 <1.0 <1.0 1.9 <1.0
24 Treatment A 1.8 <1.0 <2.0 <1.0 <1.0 1.8 <1.0
24 Treatment B 7.8 <1.0 <2.0 <1.0 <1.0 7.8 <1.0
27 Treatment B 7.1 <1.0 <2.0 <1.0 <1.0 7.1 <1.0
48 Treatment B 6.2* <1.0 <2.0 <1.0 <1.0 6.2 <1.0
48 Treatment A 9.9 1.4 2.3 1.6 <1.0 15.2 9.2
†
Detection limits 1.0 1.0 2.0 1.0 1.0 1.0 1.0
DBAA ⳱dibromoacetic acid; MBAA ⳱monobromoacetic acid; MCAA ⳱monochloroacetic acid; DCAA ⳱dichloroacetic acid (Severn); BCAA ⳱
bromochloroacetic acid; TCAA ⳱trichloroacetic acid; NA ⳱no analysis performed.
*Outside holding time.
†
Matrix-induced bias of saltwater.
Table 5 Bromate results
Time (hours) Treatment (g/L)
0 Control <1.0
0 Treatment B <1.0
24 Treatment A <1.0
24 Treatment B <1.0
27 Treatment B NA
48 Treatment B NA
48 Treatment A <1.0
Detection limits 1.0
170 AUGUST 2006 JOURNAL OF SHIP PRODUCTION
were below the concentrations set for drinking water stan-
dards.
4. Filtration was not necessary to meet IMO standards if suf-
ficient TRO was added and remained.
5. Operating costs are less than $0.02 per m
3
of ballast water
based on power and sulfite requirements.
References
CANADIAN COAST GUARD. 1992 A review and evaluation of ballast water
management and treatment options to reduce the potential for the introduc-
tion of nonnative species to the Great Lakes, Pollutech Environmental Lim-
ited for the Canadian Coast Guard, Ship Safety Branch.
DICKMAN, M., AND ZHANG, F. Z. 1999. Mid-ocean exchange of container
vessel ballast water. 2: Effects of vessel type in the transport of diatoms and
dinoflagellates from Manzanillo, Mexico, to Hong Kong, China, Marine
Ecology Progress Series, 176, 253–262.
HOLM-HANSEN, O., AND RIEMANN, B. 1978 Chlorophyll adetermination:
improvements in methodology, Oikos, 30, 438–448.
IMO. 2004 Ballast Water Management Convention, International Maritime
Organization.
MONTANI, S., MEKSUMPUN, S., AND ICHIMI, K. 1995 Chemical and physical
treatments for destruction of phytoflagellate cysts, Journal of Marine Bio-
technology, 2, 179–181.
NATIONAL RESEARCH COUNCIL. 1996 Stemming the Tide: Controlling In-
troductions of Nonindigenous Species, Committee on Ships’Ballast Opera-
tions, Marine Board, Commission on Engineering and Technical Systems,
National Academy Press, Washington, DC.
PARSONS, T. R., MAITA, Y., AND LALLI, C. M. 1984 A Manual of Chemical
and Biological Methods for Seawater Analysis, Pergamon Press, New York.
RIGBY, G. R., HALLEGRAEFF, G. M., AND SUTTON, C. 1999 Novel ballast
water heating technique offers cost-effective treatment to reduce the risk of
global transport of harmful marine organisms, Marine Ecology Progress
Series, 191, 289–293.
XIE, Y. 2000 Disinfection by-product analysis in drinking water, American
Laboratory Shelton, 32, 50–54.
AUGUST 2006 JOURNAL OF SHIP PRODUCTION 171
