Ballast Water Treatment Advisory
Our Mission

The mission of ABS is to serve the public interest as well as the 

needs of our clients by promoting the security of life, property 

and the natural environment primarily through the development 

and verifi cation of standards for the design, construction and 

operational maintenance of marine-related facilities.

Quality & Environmental Policy

It is the policy of ABS to be responsive to the individual and 

collective needs of our clients as well as those of the public at 

large, to provide quality services in support of our mission, and 

to provide our services consistent with international standards 

developed to avoid, reduce or control pollution to the environment.

All of our client commitments, supporting actions, and services 

delivered must be recognized as expressions of Quality. We pledge 

to monitor our performance as an on-going activity and to strive for 

continuous improvement.

We commit to operate consistent with applicable environmental 

legislation and regulations and to provide a framework for 

establishing and reviewing environmental objectives and targets.
ABS BALLAST WATER TREATMENT ADVISORY • 1

Ballast Water Treatment Advisory

Table of Contents

Introduction

I. Regulatory Developments

a. International Regulatory Status (IMO)

b. Overview of Some Regional, National & Local Regulations

II. BWT Technologies

 a. Overview of Treatment Technologies

 b. Treatment System Approval by IMO & Member States

III. BWT Considerations

 a. Considerations for Selection of Treatment Systems

 b. Treatment Technology Factors

 c. General Treatment System Considerations

 d. Challenges for Installation Engineering

IV. Evaluation Checklists

 a. Vessel Ballast System Particulars – Owner Supplied Data

 b. Ship & Service Characteristics that Impact BWT Selection – 

Owner Supplied Data

 c. Treatment Technology Factors – Vendor Supplied Data

 d. General Treatment System Considerations – Vendor Supplied Data

 e. Challenges for Installation Engineering – Owner Supplied Data

Appendix: Technical Information for Ballast Water Treatment Systems

Disclaimer

The development and approval of ballast water treatment systems is a dynamic process. 

The information contained in this ABS Advisory Notice should not be construed as being 

all encompassing and readers are urged to contact ABS or review the latest IMO information 

available to determine the extent to which the status of the various systems included here 

may have changed and if other systems have been proposed for review and approval.
2 • ABS BALLAST WATER TREATMENT ADVISORY

T

he ballast water and sediments carried 

by ships have been identifi ed as a major 

pathway for the transport of harmful 

invasive aquatic organisms and pathogens. 

Ships often take on ballast water in one port 

and carry such ballast to other ports where it 

is discharged. The ballast water and sediments 

contain living organisms which, despite the 

harsh conditions in the ballast tanks and piping 

systems, survive to compete with native species 

in the port of discharge. If the non-native 

organisms have few natural predators or other 

natural controls they may become invasive 

and change the local ecosystems, sometimes 

dramatically. 

The direct economic impact of aquatic invasive 

species, as well as the potential long term 

damage to the health of the local marine 

environment and the people who depend on 

that environment, is substantial and has been 

well documented. International, national and 

regional regulations have been implemented to 

control the transport of the aquatic organisms. 

The current efforts rely on ballast water 

management (BWM) practices, including 

ballast exchange, and other measures aimed 

at preventing or minimizing the uptake and 

discharge of contaminated water or sediment 

when ballasting or deballasting. These methods 

may not be completely effective in preventing 

invasive species and furthermore are not 

required if the safety of the vessel would be at 

risk during the exchange. Systems that treat 

ballast water to remove or kill organisms are 

not only potentially more reliable but are 

designed and installed to achieve measurable 

effi cacy levels while not impacting vessel safety. 

This ABS Advisory Notice has been produced 

to summarize the current state of ballast water 

treatment regulations and available technologies 

in order to provide useful guidance to 

shipowners, operators, and builders in their 

decisions about suitable treatment options. 

This Notice contains fi ve sections:

Introduction

Section 1 Regulatory Developments

Section 2 Overview of Treatment Technologies

Section 3 Considerations for System Selection, 

Installation and Operation

Section 4 Evaluation Checklists

Appendix Available Systems
ABS BALLAST WATER TREATMENT ADVISORY • 3

Section 1: 

Regulatory 

Developments

International Regulatory 

Status (IMO)

In 2004, the IMO adopted the International Convention for the Control and Management of Ships’ 

Ballast Water and Sediments. The Convention calls 

for ships to conduct a ballast water exchange or to 

meet a concentration-based ballast water discharge 

standard in accordance with a gradually implemented schedule linked to the ship’s build date and 

the amount of ballast carried on board the ship. 

Acceptance of the Convention has been slow. 

Entry into force will occur 12 months after ratifi cation by 30 States representing 35 percent of world 

merchant shipping gross tonnage. The current 

information on ratifi cation is included in Table 1. 

Because of the slow pace of adoption, the implementation deadlines written into the Convention 

have become obsolete before they could become 

mandatory. This has required adjustments to the 

implementation schedule. This uncertain regulatory schedule makes it all the more diffi cult for 

owners, builders and manufacturers to plan for 

the necessary equipment. 

Until such time as the Convention enters into 

force and the implementation schedule becomes 

binding internationally, action to address the issue 

of invasive species is increasingly occurring at 

national, regional and local levels. More than a 

dozen individual nations, in addition to regions as 

diverse as northwest Europe, the Great Lakes and 

Antarctica, have introduced specifi c regulations 

addressing the discharge of 

ballast in their waters. Further 

complicating the issue, 

individual local government 

authorities such as those in 

California, Michigan, New 

York and others within the 

US, and the State of Victoria 

in Australia, have introduced 

local ballast water management 

requirements. A small number 

of these jurisdictions may 

prohibit the discharge of 

ballast water entirely (Panama within the Panama 

Canal), require chlorination (Buenos Aires), or 

restrict in-port discharge to an approved onshore 

reception facility.

Owners are encouraged to contact their relevant 

fl ag State, port agents or shipowner association 

for the latest specifi c information on national 

or regional requirements as new and additional 

requirements are being mandated on a regular 

basis. The following sections provide information 

on the requirements for treatment as outlined in 

the IMO Convention. A few signifi cant regional 

developments are also provided.

Applicability of the IMO BWM Convention

The 2004 IMO BWM Convention applies to all 

vessel types operating in the aquatic environment 

and designed to carry ballast water that are entitled 

to fl y the fl ag of a Party to the Convention. This 

includes submersibles, fl oating craft and platforms 

including fl oating storage units (FSUs) and fl oating 

production storage and offl oading units (FPSOs), 

although the applicable requirements vary. Refer to 

Table 1 for a list of Parties to the Convention.

IMO BWM Convention Treatment Standards 

The Convention includes two regulations that 

prescribe ballast water management standards; 

Regulation D-1 addresses the Ballast Water 

Exchange standard and Regulation D-2 details the 

Ballast Water Performance standard.

Ballast water exchange is founded on the principle 

that organisms and pathogens contained in ballast 

water taken on board from coastal waters will not 

survive when discharged into deep oceans or open 

seas, as these waters have different temperatures, 

salinity and chemical composition. Similarly the 

deep ocean waters or open seas, when compared 

to the coastal waters, contain fewer organisms 

Table 1: Status of Ratifi cation of the IMO BWM Convention

(As of 1 June 2010)

States % Tonnage Parties to the Convention:

Needed: 30 Needed: 35% Albania, Antigua and Barbuda, Barbados, 

Brazil, Canada, Cook Islands, Egypt, France, 

Kenya, Kiribati, Republic of Korea, Liberia, 

Maldives, Marshall Islands, Mexico, the 

Netherlands, Nigeria, Norway, Saint Kitts 

and Nevis, Sierra Leone, South Africa, Spain, 

Sweden, Syrian Arab Republic and Tuvalu.

Currently: 25 Currently: 

24.28%
4 • ABS BALLAST WATER TREATMENT ADVISORY

Ballast 

Cpty 

(m3

)

Build 

Date

*First Intermediate or Renewal Survey, whichever occurs fi rst, after the anniversary date 

 of delivery in the respective year

2009 2010 2011 2012 2013 2014 2015 2016 2017

< 1,500

< 2009

in 2009 Note: D-1; D-2 by 2nd Annual but not beyond 31 Dec. 2011 or EIF, whichever is later

> 2009 D-2 (at delivery or EIF, whichever is later)

> 1,500

or 

< 5,000

< 2009

in 2009 Note: D-1; D-2 by 2nd Annual but not beyond 31 Dec. 2011 or EIF, whichever is later

> 2009 D-2 (at delivery or EIF, whichever is later)

> 5,000

< 2012

> 2012

and pathogens and those that do exist are less 

likely to adapt to the new coastal or freshwater 

environment. Therefore the probability of organism 

and pathogen transfer through ballast water is 

signifi cantly reduced.

As a result, an exchange of ballast water is 

performed while the vessel is located in the deep 

ocean. Ships performing ballast water exchange are 

required to do so with an effi ciency of at least 95 

percent volumetric exchange. Acceptable methods 

for ballast water exchange are the Sequential 

Method, the Flow-through Method and the 

Dilution Method. 

Noting that ballast water exchange presents 

signifi cant operational concerns and challenges, 

and also that ballast exchange may not provide a 

totally effective solution to reduce the spread of 

unwanted aquatic organisms and pathogens from 

ships’ ballast water over time, the Convention 

requires an upgrade to the installation of ballast 

water treatment systems in accordance with a 

specifi ed schedule. 

The D-2 standard mandates compliance with a 

specifi ed biological result. This criterion is in the 

form of specifi c limits on aquatic life in the ballast 

discharge as detailed:

Ships conducting ballast water management in 

accordance with this regulation shall discharge:

• Less than 10 viable organism per m3

 > 50μ in 

minimum dimension, and 

• Less than 10 viable organisms per ml < 50μ 

and >10μ in minimum dimension, and

• Less than the following concentrations of 

indicator microbes:

 – Toxicognic Vibrio cholera less than 

1 colony forming unit (cfu) per 100 ml, 

or less than 1 cfu per 1 gram zooplankton 

samples

 – Escherichia coli less than 250 cfu per 100 ml

 – Intestinal Enterococci less than 100 cfu 

per 100 ml 

The D-2 standard is the metric used to measure 

the effi cacy of the treatment system and it applies 

to the system as installed on board and used in 

actual operations. All treatment systems must 

be type approved by an Administration under a 

robust protocol which requires that they satisfy 

this standard in full scale operations. In any port 

or offshore terminal, an offi cer authorized by a 

Party to the Convention may board a vessel to 

which the Convention applies and test the ballast 

water discharge for compliance by taking samples.

IMO Convention Compliance Timeframe

Table 2 indicates the implementation schedule 

of the 2004 BWM Convention as revised by 

Resolution A.1005(25) which addresses ships 

with a build date of 2009. This adjustment was 

adopted as a result of a review of the entry into 

force provisions of the Convention during the 

25th Session of the IMO Assembly in November 

2007 and the stage of development of approved 

Table 2: IMO BWM Convention Implementation Schedule

Revised per Resolution A.1005(25)

D-1 or D-2 D-2*

D-2*

D-2*

D-1 or D-2

D-1 or D-2

N/A D-2 (at delivery or EIF, whichever is later)

Note: EIF = Entry into force
ABS BALLAST WATER TREATMENT ADVISORY • 5

ballast water treatment technologies. Further 

clarifi cation was provided in IMO BWM.2/Circ.19 

issued at the Marine Environment Protection 

Committee (MEPC) in July 2009 about the 

implementation dates for the D-2 standard for 

ships built before 2009 with ballast capacity of no 

more than 5,000 m3

 and also ships built before 

2012 with ballast capacity of more than 5,000 m3.

The following examples are instructive in how 

to interpret Table 2.

• A ship with a ballast capacity less than 5,000 

m3

 constructed in 2009 will not be required to 

comply with regulation D-2 until its second 

annual survey but no later than 31 December 

2011 or EIF, whichever is later.

• A ship with a ballast water capacity of less than 

5,000 m3

 constructed after 2009 shall be able 

to conduct treatment that at least meets the 

D-2 standard upon delivery or EIF, whichever 

is later.

• A ship with a ballast water capacity of greater 

than 5,000 m3

 constructed before 2012 is 

required to comply with the D-2 standard not 

later than the fi rst intermediate or renewal 

survey, whichever occurs fi rst, after the 

anniversary date of the ship in 2016.

Recent IMO Activity Related to 

the 2004 Convention

MEPC 59, held in July 2009, further considered 

ships built in 2010 and the availability of 

approved treatment systems as well as the status 

of ratifi cation. The Committee agreed that there 

were a suffi cient number of approved ballast 

water treatment systems available to support 

the full implementation of the Convention and 

there was no need to delay the entry into force 

any further. The only remaining impediment that 

remains is ratifi cation by the required number of 

member States. Until shipyards begin to include 

treatment systems in their new building designs, 

the onus may rest with the owner to specify the 

installation of a ballast water treatment system 

(or at least plan for suffi cient space for future 

installation) in their contract with the shipyard 

or to retrofi t these systems into ships that are 

only a few years old. 

At MEPC 59 new guidelines were also 

developed for the safe handling and storage of 

chemicals used to treat ballast water and for 

safety procedures for risks to the ship and crew 

resulting from the treatment process.

IMO Guidelines Available 

Since the adoption of the Convention, IMO has 

been working to develop a series of guidelines that 

further clarify and expand upon the requirements 

put forward in the Convention. All 14 of the 

planned guidelines have been completed and 

are available from IMO. A list of the guidelines 

supporting the Ballast Water Convention is as 

follows: 

G1. Sediment Reception Facilities

 MEPC.152(55)

G2. Guidelines for Ballast Water Sampling

 MEPC.173(58)

G3. BW Equivalent Compliance 

 MEPC.123(53)

G4. BWM and the Development of BWM Plans

 MEPC.127(53)

G5. BW Reception Facilities 

 MEPC.153(55) 

G6. BW Exchange – Operational 

 MEPC.124(53)

G7. Risk Assessment under Regulation 4-A 

of the BW Convention 

 MEPC.162(56)

G8. Guidelines for Approval of BW 

Management Systems 

 MEPC.125(53)

 Rev. MEPC.174(58)

G9. Approval of BWM Systems that make 

use of Active Substances 

 MEPC.126(53)

 Revision MEPC.169(57)

G10. Approval and Oversight of Prototype 

BW Treatment Programs

 MEPC.140(54)

G11. Guidelines for BW Exchange Design 

and Construction Standard

 MEPC.149(55)

G12. Design and Construction to Facilitate 

Sediment Control on Ships

 MEPC.150(55)

G13. Guidelines for Additional Measures 

Regarding BWM Including 

Emergency Situations 

 MEPC161(56) 

G14. Guidelines on Designation of Areas for BWE

 MEPC.151(55)

Note: BW = Ballast Water

 BWM = Ballast Water Management

 BWE = Ballast Water Exchange
6 • ABS BALLAST WATER TREATMENT ADVISORY

Of special interest to owners and builders are the 

requirements for ballast water sampling contained 

in G2 as it impacts ballast system design and 

operation. The objective of the G2 guideline is to 

provide all parties, including Port State Control 

offi cers, with practical and technical guidance on 

ballast water sampling and analysis for determining 

if the ship is in compliance with the ballast 

water management convention. It is important 

to note that the G2 guideline discusses general 

sampling procedures and does not address the 

legal requirements as the legislative procedures 

and requirements for enforcement action based on 

biological testing are signifi cantly different from 

country to country. The guideline includes the 

following important issues related to operation 

of the treatment system:

• It was recognized by IMO that the sampling must 

be simple, rapid and applicable at the point of 

ballast discharge and safe to the ship and crew. 

Time needed for the analysis of the collected 

samples shall not be used as a basis for unduly 

delaying the operation, departure or movement 

of the vessel.

• The sample is to be taken from the discharge 

line, as near to the point of discharge as possible, 

during discharge. Note that the G8 guideline 

also calls for sampling points; however, the 

points in the G2 guideline are not just for 

testing during the type approval but also for 

in-service testing. Tank sampling for those 

systems which use a treatment system is not 

preferred as the scientifi c trials have shown 

that these samples may not provide accurate 

estimates of the organism concentration. 

An exception to this guidance may be when 

the ballast tanks are emptied through direct 

overboard discharge valves such as in upper 

wing tanks.

• Isokinetic sampling ports are recommended 

so that the sample water is collected at 

the same fl ow rate as the ballast water in 

the discharge line, since this will lessen 

the likelihood of there being a difference 

in the organism and particulate matter 

concentrations.

• Initial and indicative analysis to establish 

whether a ship is complying with the D-2 

standard may be undertaken by a microscope 

and, if further doubt exists, the samples are to 

undergo a more stringent analysis to establish 

if the D-2 standard is being met.
The use of monitoring and in line recording 

devices of physical and/or chemical indicators are 

being proposed and developed as a valid means to 

verify that the ballast water is adequately treated 

and conforms to the ballast water treatment 

performance standard.

Regulation C-1 of the Convention enables a Party 

to the Convention, either individually or jointly 

with other parties, to take additional measures in 

addition to those in the Convention to prevent, 

reduce or eliminate the transfer of harmful 

organisms and pathogens. In recognizing the 

potential impact that such measures may have on 

international shipping, IMO developed the G13 

guideline. The provisions in this regulation and 

guideline are interesting in that they allow for these 

additional measures under international Law only 

if the MEPC approves these additional measures. 

The evaluation criteria to be used by the MEPC in 

determining whether it grants its approval for the 

additional measures to control aquatic invasive 

species in a specifi ed region is if it would adversely 

impact areas adjacent to the region or impact 

the safety or commercial nature of international 

shipping activities. It is not certain how regional 

measures in excess of IMO requirements would 

be viewed under this guideline. This is potentially 

very important for those vessels intending to transit 

to regions with local requirements, for example 

US waters. 

Guidelines G8 to G10 address the approval 

of ballast water treatment systems. These are 

discussed in Section 2 of this Advisory Notice.

Overview of Some Regional, 

National & Local Regulations

United States/USCG

The United States fi rst passed ballast water 

legislation in 1990 as the Nonindigenous Aquatic 

Nuisance Prevention and Control Act of 1990 

(NANPCA). This law established the Coast Guard’s 

(USCG) regulatory jurisdiction over ballast water 

management, mandated a regional ballast water 

management program for the Great Lakes and 

called for studies to document the need for a 

national ballast water management program. 

To implement the NANPCA the USCG published 

a fi nal rule in the Federal Register on 8 April 

1993 wherein 33 CFR Part 151, Subpart C, the 

mandatory ballast water management requirements 

for ships entering the waters of the Great Lakes 

after operating outside of the US Exclusive 

Economic Zone were established. These regulations 

were extended to portions of the Hudson River 

in 1994. In 1996 the US Congress enacted the 

National Invasive Species Act (NISA). This charged 

the USCG with establishing a voluntary ballast 

ABS BALLAST WATER TREATMENT ADVISORY • 7
8 • ABS BALLAST WATER TREATMENT ADVISORY

water management program for all other US 

ports and required vessels to submit ballast water 

management reports. 

In addition, this Act directed the USCG to 

submit a report to the US Congress on the 

effectiveness of the voluntary program and 

to make the program mandatory if the rate of 

compliance with the voluntary guidelines was 

determined to be inadequate. In May 1999 the 

USCG published an interim rule in the Federal 

Register entitled “Implementation of the National 

Invasive Species Act of 1996”. This interim rule 

created the mandatory ballast water reporting 

and recordkeeping requirements and prompted 

voluntary BWM practices (including ballast water 

exchange) for all vessels entering all waters of the 

United States after operating outside the exclusive 

economic zone. 

In November 2001 the interim rule was amended 

and published as a fi nal rule. On 3 June 2002, the 

USCG submitted the fi rst ballast water management 

report to Congress wherein it was concluded 

that compliance with the mandatory reporting 

requirements was insuffi cient to allow for an 

accurate assessment of the voluntary ballast water 

management program. This report to Congress 

also stated that it is the intention of the Secretary 

of Homeland Security to have the USCG take 

additional actions to reduce the infl ow of aquatic 

nuisance species. In June 2004, the voluntary 

guidelines of 33 CFR 151, Subpart D were made 

mandatory for all vessels equipped with ballast 

water tanks. 

In the last several years there have been a number 

of bills introduced in the US Congress that propose 

a ballast discharge standard. None have yet become 

law. However, the USCG has recently released 

a notice of proposed rulemaking (FR 44633 28 

August 2009). The report of proposed rulemaking 

and regulatory analysis includes an assessment 

of the economic impact of treatment standards 

between the IMO D-2 levels and levels up to 1,000 

times more stringent (see Table 3). 

The proposed treatment regulation calls for a 

two phase implementation schedule. The Phase 

1 standard is the same as the IMO D-2 and the 

implementation schedule is similar to the IMO 

schedule. Existing ships (those built prior to 

1 January 2012) with ballast water capacity of 

between 1,500 and 5,000 m3

 will be required to 

meet this standard by their 1st dry docking after 

1 January 2014. Ships with ballast water capacity 

of less than 1,500 m3

 or greater than 5,000 m3 must 

meet the standard by their fi rst drydocking after 

1 January 2016. New vessels (those with build 

dates on or after 1 January 2012) will be required 

to meet it at delivery. 

The proposed Phase 2 standard is up to 1000 

times more stringent than the Phase I (and IMO) 

standard. The Phase 2 discharge requirements must 

be met by new ships with a build date on or after 

1 January 2016. For ships with a build date before 

1 January 2016, the compliance date is the fi rst 

drydocking after 1 January 2016 or fi ve years after 

a Phase 1 system was installed, whichever is later. A 

‘practicability review’ to be conducted by the USCG 

Table 3: Discharge Standards in USCG Proposed Regulation 

(August 2009)

Organism Size US Proposed Law 

Phase 1 Standard

US Proposed Law 

Phase 2 Standard IMO Regulation D-2

> 50 μm in min dimension < 10 viable organisms/m3 < 1 viable organisms/100m3 < 10 viable organisms/m3

< 50 μ and >10μ in min. 

dimension < 10 viable organisms/ml < 1 viable organisms/100ml < 10 viable organisms/ml

< 10 μm in min. dimension no limit < 103

 bacteria/100 ml

< 104

 viruses/100 ml no limit

Escherichia coli < 250 cfu/100 ml < 126 cfu/100 ml < 250 cfu/100 ml

Intestinal enterococci < 100 cfu/100 ml < 33 cfu/100 ml < 100 cfu/100 ml

Toxicogenic Vibrio cholerae < 1 cfu/100 ml < 1 cfu/100 ml 

< 1 cfu/100 ml or 

< 1 cfu/gram wet weight 

zooplankton samples
ABS BALLAST WATER TREATMENT ADVISORY • 9

Table 4: Discharge Standards in Current California Law

is also proposed for 2013 to evaluate whether 

the technology to achieve the Phase 2 standard is 

available in order to confi rm the future phase entry 

into force dates.

While the standards and schedule generally apply 

to all commercial ships discharging ballast in US 

waters, there is a notable exemption for crude oil 

tankers engaged in coastwise trade. 

Ballast discharges in US ports are further regulated 

by the Vessel General Permit (VGP) for the 

National Pollution Discharge Elimination System 

(NPDES) program under the Clean Water Act 

(CWA). Previously exempted from the NPDES 

program, ballast water discharges in port must 

now be documented and the vessel must follow 

federal regulation aimed at controlling discharge 

of harmful or invasive elements within the ballast 

water. Treatment is not explicitly required and 

there is no treatment standard in US Federal 

regulatory regime in the current VGP. However, the 

CWA allows each individual State to add specifi c 

provisions, including performance standards, to the 

VGP. A treatment system that uses active substances 

(chemicals or biological agents) would be subject 

to scrutiny under the Clean Water Act. 

California

California’s Marine Invasive Species Act (2003) 

established the Marine Invasive Species Program 

and directed a state agency to develop performance 

standards for ballast water discharge. In 2006 the 

State passed the Coastal Ecosystems Protection Act 

(SB497) which incorporated the recommended 

standards and made them mandatory. The 

implementation schedule was initially set to match 

the IMO schedule. In 2008, a review required 

by the law of available treatment technologies 

recommended that the implementation date for 

new ships be delayed one year to 2010.

As shown in Table 4, the California standards are 

much more stringent than the IMO standards and 

similar (but not identical) to the Phase 2 standard 

recently proposed by the USCG (see Table 3). The 

California law includes very explicit guidelines for 

sampling points and methods.

Further, note that California law currently sets a 

fi nal discharge implementation date of 1 January 

2020 that specifi es zero detectable living organisms 

for all size ranges in the ballast discharge stream.

Others

In the US, some Great Lakes states such as Illinois, 

Indiana, Minnesota and Ohio, are also considering 

their own discharge standards in line with the 

IMO D-2 requirements. In addition to California, 

New York and Pennsylvania have moved into law 

discharge standards that exceed IMO D-2.

Several other Administrations have passed laws 

regulating ballast water that include provisions 

for best practices and ballast exchange. Some are 

also considering discharge standards in line with 

the IMO D-2 requirements as they consider their 

decision to ratify the 2004 IMO Convention. 

Organism Size California Law IMO Regulation D-2 US Proposed Law 

Phase 2 Standard

> 50 μm in min. dimension No detectable living organisms < 10 viable organisms/m3 < 1 viable organisms/100 m3

< 50 μ and > 10μ in min. 

dimension < 0.01 living organisms per ml < 10 viable organisms/ml < 1 viable organisms/100 ml 

< 10 μm in min. dimension < 103

 bacteria/100 ml

< 104

 viruses/100 ml no limit < 103

 bacteria/100 ml

< 104

 viruses/100 ml

Escherichia coli < 126 cfu3

/100 ml < 250 cfu/100 ml < 126 cfu/100 ml 

Intestinal enterococci < 33 cfu/100 ml < 100 cfu/100 ml < 33 cfu/100 ml 

Toxicogenic Vibrio cholerae

< 1 cfu/100 ml or 

< 1cfu/gram wet weight 

zoological samples 

< 1 cfu/100 ml or 

< 1 cfu/gram wet weight 

zooplankton samples

< 1 cfu/100 ml 
10 • ABS BALLAST WATER TREATMENT ADVISORY

Section 2

BWT Technologies

This section of the Advisory Notice provides 

an explanation of treatment technologies 

currently being developed, the regulatory approval 

process certifying vendor-supplied equipment as 

compliant with the regulation, and a list of available 

systems currently on the market as of 

the date of publication of this document. 

Overview of Treatment 

Technologies

IMO defi nes ballast water treatment equipment as:

“...the equipment which mechanically, 

physically, chemically or biologically processes 

either singularly or in combination to remove, 

render harmless or avoid the uptake or 

discharge of harmful organisms or pathogens. 

Ballast water treatment equipment may operate 

at the uptake or discharge of ballast water, 

during the voyage, or at a combination of 

these events.”

Types of Treatment Technologies

The technologies currently available or being 

developed can generally be grouped under three 

broad categories based on their primary mechanism 

for rendering the organism inactive: mechanical, 

physical and chemical. These groups and the more 

promising technologies related to each are shown in 

Figure 1 and described briefl y in the following text.

Mechanical Systems

• Filtration – sediment and particles are removed 

with disk and screen fi lters during ballast intake. 

They are often self-cleaning with a back-fl ushing 

cycle. The waste stream is directed overboard 

back to the water source. These fi ltration systems 

create pressure drops and a reduced fl ow rate due 

to resistance in the fi lter elements and the selfcleaning procedures.

• Cyclonic separation – solid particles are 

separated from the water due to centrifugal 

forces. Only those particles with a specifi c gravity 

greater than that of water can be separated.

• Electro-mechanical separation – a fl occulent is 

injected that attaches to organisms and sediment. 

Magnetic separation and fi ltration is used to 

remove the solid particles.

Physical Disinfection

• Ultraviolet light – UV radiation is used to 

attack and break down the cell membrane 

killing the organism outright or destroying its 

ability to reproduce. The effectiveness depends 

on the turbidity of the ballast water (i.e. the 

concentration of sediments) as this could 

limit the transmission of the UV radiation. UV 

lights are required to be maintained and power 

consumption needs to be considered.

• Cavitation/ultrasounds – venturi pipes or slit 

plates are used to generate cavitation bubbles and 

this high energy bubble creation and collapse 

results in hydrodynamic forces and ultrasonic 

oscillations, or high frequency noise, which 

disrupts the cell walls of organisms effectively 

killing them.

Figure 1: Treatment Technology Types

Mechanical Systems Physical Disinfection Chemical Treatment

Electro-mechanical 

Separation

Deoxygenation

Filtration Ultraviolet Light Disinfecting Biocides

Cyclonic Separation Cavitation Electrolytic Chlorination
ABS BALLAST WATER TREATMENT ADVISORY • 11

• De-oxygenation – 

various methods are 

used to remove the 

dissolved oxygen 

in the ballast water 

and replace it with 

inactive gases, such 

as nitrogen or other 

inert gas. Removing 

the oxygen not only 

kills the aerobic organisms but it can also have 

benefi ts for corrosion prevention provided that 

the oxygen content is maintained at the correct 

levels. De-oxygenation can require a prolonged 

period in order to render the organisms and 

pathogens harmless to the receiving waters.

Chemical Treatment

• Chemical biocides – pre-prepared or 

packaged disinfectants designed to be 

dosed into the ballast fl ow and kill the living 

organisms by chemical poisoning or oxidation. 

Typical biocides include chlorine, chloride 

ions, chlorine dioxide, sodium hypochlorite 

and ozone. Residual biocides in the ballast 

water must meet ballast discharge standards 

which may necessitate neutralization 

techniques.

• Electrolytic chlorination – electrical current is 

applied directly to the ballast water fl ow in an 

electrolytic chamber, generating free chlorine, 

sodium hypochlorite and hydroxyl radicals, 

causing electrochemical oxidation through the 

creation of ozone and hydrogen peroxide. This 

method is limited in effectiveness to seawater 

having a certain level of dissolved salt and, 

could also create unwanted residuals.

Types of chemical treatments include Active 

Substances or Preparations. The offi cial defi nitions given in the BWM Convention are as 

follows:

• Active substance – a substance or organism, 

including a virus or a fungus that has a general 

or specifi c action on or against harmful aquatic 

organisms and pathogens. 

• Preparation – any commercial formulation 

containing one or more active substances including any additives. This term also includes 

any active substances generated on board for 

the purpose of ballast water treatment and any 

relevant chemicals formed in the ballast water 

treatment system that make use of active substances to comply with the BWM Convention.

Technical Challenges 

& System Combinations

The treatment technologies differ in method 

and rate of application, scalability, holding time 

(required for kill rates and safe discharge), power 

requirements, effects on other ship systems or 

structure (corrosion), inherent safety and costs of 

operation. In many cases their effi cacy varies with 

conditions of the ballast water, fl ow rates, volume 

of water treated and holding time. There are also 

issues of whether treatment is done at intake, while 

being held on board, at discharge, 

or a combination of the three times. 

For instance, fi ltration, separation and UV radiation 

are done during ballast loading and discharge and 

are sized for the maximum fl ow rate in the ballast 

system. Conversely chemical biocides and deoxygenation are usually applied to attain a certain 

concentration in the water in the ballast tanks. The 

effi cacies of these systems do not depend so much 

on the fl ow rate of the pumps as the time the ballast 

is allowed to remain in the tanks to achieve the 

desired kill rate. Short voyages can be a problem 

for these technologies. 

Matching the treatment technology to the ship 

type, or more accurately the ballast system type, 

and vessel service is the key to designing 

a successful ballast water treatment system. 

To overcome the limitations of a particular technology many proposed treatment systems are based 

on a combination of two or more technologies. 

Although there are approved chemical disinfection 

only treatments, these are also combined with some 

form of pre-treatment to make them more effective 

for certain vessel or ballast conditions. 

The most prevalent system types are ones that 

combine mechanical separation/fi ltration with 

UV radiation or chemical disinfection. The initial 

mechanical separation/fi ltration is used to remove 

the larger organisms in order to increase the 

effectiveness of the secondary treatments.
Treatment System Approval 

by IMO & Member States

IMO Approval Regime

Regulation D-3 of the BWM Convention requires 

that the ballast water treatment systems must be 

approved by the Flag State Administration and for 

those treatment systems which make use of active 

substances or preparations, by the IMO as well. It 

is important to note that the Convention requires 

that discharges of ballast water from ships must 

meet the D-2 performance standard on an ongoing 

basis. 

However type approval of a ballast treatment 

system should not be considered as an indication 

that a given system will work on all vessels in all 

situations. Even after installing a type approved 

system, the owner/operator is still responsible 

for compliance of the discharge throughout the 

vessel’s life. 

To achieve consistency in the approval process, 

IMO has prepared several Guidelines. 

G8 Guidelines for Approval of Ballast Water 

Management Systems 

 Resolution MEPC.174(58)

G9 Procedure for Approval of Ballast 

Water Management Systems that 

Make Use of Active Substances 

 Resolution MEPC.169(57)

G10 Guidelines for Approval and Oversight 

of Prototype Ballast Water Treatment 

Technology Programs 

 Draft Resolution MEPC.140(54)

These guidelines outline the approval framework 

and a uniform manner of testing, analysis of 

samples and evaluation of results. G8 and G9 

together address the approval required under 

Regulation D-3 of the Convention. G8 addresses 

the suitability and effi cacy of the system. In addition, where it can be reasonably concluded that 

the treatment process could result in changes to 

the chemical composition of the treated water 

such that adverse impacts to the receiving waters 

might occur upon discharge, additional testing 

will be required by the G8 Guidelines. G9 addresses the acceptability of any active substances 

and preparations for use in ballast water treatment 

systems concerning ship safety, human health and 

the aquatic environment. G9 is provided as a safeguard for the sustainable use of active substances 

and preparations. 

To encourage the development of new ballast 

water treatment technologies, the Convention 

includes an allowance for short term approval of a 

treatment system that undergoes prototype testing 

according to G10. For any ship that participates in 

12 • ABS BALLAST WATER TREATMENT ADVISORY
ABS BALLAST WATER TREATMENT ADVISORY • 13

a prototype testing program, the requirements of 

Regulation D-2 shall not apply until fi ve years after 

the date the equipment was installed or fi ve years 

after the date on which the ship would otherwise 

be required to comply with D-2, whichever is later.

The G8/G9 approval process is a robust and 

lengthy process requiring approximately one 

year to complete. It includes the following:

• Documentation review and approval of the 

design and construction of the system and 

determine if there are any fundamental 

problems that might constrain the ability of the 

system to manage ballast water or operate safely. 

• Successful compliance with environ-mental 

testing by an approved laboratory of all system 

components. This testing 

is to include specifi ed limits of vibration, 

temperature, humidity, fl uctuations in power 

supply, inclination and, if applicable, protection 

from green water impact.

• Land-based testing to confi rm that the system 

can meet the D-2 standard for a range of 

water conditions (fresh, brackish and sea). 

The land-based approval testing is intended 

to provide replicability and comparability 

to other treatment systems. Any limitations 

imposed by the treatment system on the testing 

procedure should be noted and evaluated by 

the Administration in its consideration for type 

approval. In some situations, the land-based 

testing can be done on scaled-down equipment. 

• Shipboard testing of a complete, full scale 

system throughout a full ballast cycle (uptake, 

storage, treatment, and discharge). At least three 

consecutive successful test cycles that comply 

with regulation D-2 are required over a period 

not less than six months.

Once the technical review and testing are completed to the satisfaction of the Administration 

and the Administration is satisfi ed that the quality 

assurance program employed by the manufacturer 

will mean that the equipment can be produced 

consistently to the required specifi cation, a Type 

Approval Certifi cate may be issued. When a type 

approved ballast water treatment system is installed on board a vessel, an installation survey 

is conducted to confi rm that the system has been 

installed as designed, is ready for operation, and 

conforms to the Type Approval Certifi cate. Upon 

successful completion of the installation survey, 

a BWM Certifi cate may be issued as required by 

the Convention.

Systems with active substances or preparations 

must undergo the additional approval process 

contained in the IMO G9 Guideline to verify that 

the potential hazardous properties of the active 

substance or preparations or relevant chemicals 

formed in treated ballast water do not create 

any unreasonable risk to the ship and personnel 

and that the ballast water is no longer toxic. The 

toxicity testing is needed to confi rm that the 

active substance or preparation used does not 

cause conditions which have the potential of 

harming the receiving environment or human 

health.

The additional approval required under the G9 

uses a two-tier methodology consisting of a Basic 

and Final Approval.

• Basic approval confi rms that, based on the 

information available, there are no unacceptable 

adverse effects, nor a potential for unreasonable 

risk to the environment, human health, 

property or resources. It includes screening 

for persistency, bioaccumulation and toxicity. 

Testing is conducted in a laboratory under 

conditions simulating ballast water discharge 

following treatment.

• Final approval confi rms the previous 

evaluations of risks to the ship, crew and the 

environment including the storage, handling 

and application of active substances or 

preparations, remain valid and the concerns 

expressed during the basic approval process 
IMO. This technical group is the Group of Experts 

on the Scientifi c Aspects of Marine Environmental 

Protection – Ballast Water Working Group 

(GESAMP-BWWG). The GESAMP-BWWG makes 

a recommendation to the IMO MEPC which, on 

the basis of the GESAMP-BWWG’s report, will 

confer approval on a treatment system that uses 

active substances. 

The overall approval process is summarized in 

Table 5. Shaded parts (G9) can be omitted for 

systems not using active substances 

(e.g., de-oxygenation or ultrasonic). 

A more complete fl ow chart of 

the approval process is shown in 

Figure 2.

Verifying Equipment Approval

Any system which is being considered 

for installation on board a ship should 

have a valid Type Approval Certifi cate 

in the proper form and signed by 

the Administration. This certifi cate 

should: 

• Identify the type and model of the 

system, related equipment assembly 

drawings and model specifi cation 

numbers;

• Include a reference to the full 

performance test protocol on 

which the approval is based and 

be accompanied by a copy of the 

original test results;

• State the specifi c application for 

which the treatment system is 

approved, e.g. for specifi c ballast 

water capacities, fl ow rates, 

salinity or temperature regimes, 

or other limiting conditions or 

circumstances as appropriate.

have been addressed, as well as the residual 

toxicity of the discharge conforms to the 

evaluation undertaken for basic approval. In 

addition a risk evaluation is performed at the 

fi nal approval to qualitatively account for the 

cumulative effects that may occur due to the 

nature of shipping and port operations.

Both steps involve not only review by the 

Administration, but also a direct and complete 

review by a special technical group set up within 

Table 5: Ballast Water Treatment System Approval Process Overview

Approval Process for Manufacturer Ship Specifi c 

Approval

Key Steps in 

Approval Process

Documentation 

Review 

& Approval

Basic Approval 

for Active 

Substances 

(G9)

System 

Approval Land 

& Shipboard 

Testing

Final Approval 

for Active 

Substances 

(G9)

Type Approval 

Certifi cate

Installation 

Survey

Approval 

Authority Administration GESAMPBWWG, IMO Administration GESAMPBWWG, IMO Administration Administration

14 • ABS BALLAST WATER TREATMENT ADVISORY
ABS BALLAST WATER TREATMENT ADVISORY • 15

Figure 2: Flow Chart of Ballast Water Management System Approval 

BWM System

(treatment, control & monitoring)

Yes

Yes

No

Yes

Yes

Yes

Yes

No

No No

G(9)

G(9)

G(8)

Type

Approval

Prototype

Testing G(10)

Yes

Yes

No

Yes No

Results may 

be used

No

No

No

Yes

Yes

No

No

Manufacturer tests 

found satisfactory 

by a government

BWNS includes active 

substances

Basic approval or 

active substances 

granted by IMO

Land-based testing 

to D-2 standard 

is satisfactory

Shipboard testing 

to D-2 standard 

is satisfactory

BWMS includes 

active substances

BWMS adversely changes 

chemical composition 

of treated water

Shipboard testing 

to evaluate against 

D-2 standard

All BW discharged 

during test period 

meets D-2 standard

Ship issued BWM 

Certifi cate after functional 

test of BWMS

Documentation review & approval by a government

BMW system test 

protocol options

Final approval for 

active substances 

granted by IMO

Government grants 

type approval 

of BWMS

Type Approved BWMS 

can be installed on board 

any ship
16 • ABS BALLAST WATER TREATMENT ADVISORY

Table 6: BWM System Approvals as of MEPC 60

Approval Status of BWM Systems using Active Substances (G9)

Treatment System Approval Status

The following tables summarize the current basic, fi nal and type approval status of record. Systems that 

have received fi nal and/or type approval are described more fully in the Appendix of this publication. 

System Name Proposed By Approval Type Approved By

PureBallast System Norway Basic & Final MEPC 56

SEDNA-Ocean BWM System using PERACLEAN Ocean System Germany

Basic MEPC 54

Final MEPC 57

OceanSaver BWM System Norway

Basic MEPC 57

Final MEPC 58

Electro-Cleen System (Electrolytic Disinfection) Korea

Basic MEPC 54

Final MEPC 58

RWO BWMS (CleanBallast) using EctoSys Electro-chemical System Germany

Basic MEPC 55

Final MEPC 59

NK-03 Blue Ballast System (Ozone) Korea

Basic MEPC 56

Final MEPC 59

Hitachi BW Purifi cation System (ClearBallast) Japan

Basic MEPC 57

Final MEPC 59

Hamworthy Sedinox BWMS Netherlands

Basic MEPC 58

Final MEPC 59

Resource Ballast Technologies System (Unitor) South Africa

Basic MEPC 57

Final MEPC 60

GloEn-Patrol System Korea

Basic MEPC 57

Final MEPC 60, 

JFE BallastAce (in cooperation with TG) Japan

Basic MEPC 58

Final MEPC 60

HHI BWMS (EcoBallast) Republic of Korea

Basic MEPC 59

Final MEPC 60

FineBallast Ozone System Japan Basic MEPC 55

Ecochlor BW Treatment System Germany Basic MEPC 58

Blue Ocean Shield BWMS China Basic MEPC 59

AquaTriComb BW Treatment System Germany Basic MEPC 59

SiCURE BWMS Germany Basic MEPC 60

Sunrui BWMS China Basic MEPC 60

DESMI Ocean Guard BWMS Denmark Basic MEPC 60

Blue Ocean Guardian (BOG) BWMS Republic of Korea Basic MEPC 60

HHI BWMS (HiBallast) Republic of Korea Basic MEPC 60

KS BWMS (En-Ballast) Republic of Korea Basic MEPC 60

OceanGuard BWMS Norway Basic MEPC 60

Severn Trent DeNora BalPure Germany Basic MEPC 60
ABS BALLAST WATER TREATMENT ADVISORY • 17

Table 7: Ballast Water Management Systems with Type Approval Certifi cation (G8)

Approval 

Date

Name of 

Administration

Name of the Ballast 

Water Management 

System

Active Substance 

Employed

1 June 2008 Norwegian 

Administration PureBallast System

Free radicals Cl2-, ClB-, 

Br2- and CO3-

(Refer to MEPC 56/2/2, 

Annex 5)

2 June 2008

Federal Maritime and 

Hydrographic Agency, 

Germany

SEDNA® BWMS 

(Using Peraclean®

Ocean System)

(temporarily withdrawn 

from the market)

PERACLEAN® Ocean

(Refer to MEPC 57/2/10, 

Annex 7)

3 September 2008

Offi ce of the Maritime 

Administration, 

Marshall Islands

NEI Treatment System 

VOS-2500-101 None Used

4 December 2008

Ministry of Land, 

Transport and 

Maritime Affairs, 

Republic of Korea

Electro-CleenTM System

HOCl (OCl-), HOBr (OBr-). 

O3 (H2O2), OH-

(Refer to MEPC 58/2/7, 

Annex 7)

5 April 2009 Norwegian 

Administration

OceanSaver® Ballast Water 

Management System 

(OS BWMS)

HClO, Cl2, O3, H2O2, ClO2

and ClO-

(Refer to MEPC 58/2/8, 

Annex 4)

6 April 2009 The United Kingdom

Hyde GUARDIANTM

Ballast Water 

Management System

None Used

7 November 2009

Ministry of Land, 

Transport and 

Maritime Affairs, 

Republic of Korea

NK-O3 BlueBallast System 

(Ozone)

O3

(Refer to MEPC 59/2/16, 

Annex 6)

8 November 2009 Norwegian 

Administration OptiMarin Ballast System None Used

9 December 2009

Ministry of Land, 

Transport and 

Maritime Affairs, 

Republic of Korea

GloEn-PatrolTM

MPUV irradiation

(Refer to MEPC 60/2/11, 

Annex 4)

10 March 2010

Maritime Bureau, Ministry 

of Land, Infrastructure, 

Transport and Tourism of 

Japanese Government

Hitachi ClearBallast

PAC, Fe3

O4 and PASA

(Refer to MEPC 59/2/19, 

Annex 4)
Section 3

Considerations

This section has been prepared to summarize for 

vessel owners, operators and builders the practical 

realities of shipboard ballast water systems so 

that they can be in a better position to evaluate 

treatment technology options and plan for their 

installation. Included are discussions of the key 

features of ships’ ballast water handling systems 

and practices, and the features of the various 

treatment technologies that will have an important 

impact on the ship or ballast practices and costs. 

Considerations for Selection 

of Treatment Systems 

Overview

Ballast water treatment is still an evolving technology with an ever-growing number of manufacturers 

developing systems to meet the anticipated regulatory requirements. Readers are urged to contact 

ABS or review the latest IMO information to 

determine the current status of treatment system 

approvals. This current situation means that there 

is limited in-service experience for the systems 

being offered and there is a general understanding 

that no single system is suitable for all ship types or 

service. The owner/operator must make a considered choice for the ballast water treatment that best 

suits the demands of the ship and service taking 

into account vendor specifi cations and the extent 

of shore side and shipboard testing carried out during the type approval process. A careful engineering 

analysis of the following factors bring order to 

the decision-making process. These issues are 

discussed in some detail as follows. 

Ship and Vessel Service Characteristics 

that Impact BWT Selection

• Ship type and capacity

• Ballast water handling practices including 

NOBOBS (no ballast on board ships)

• Ballast water characteristics

• Vessel service characteristics

• Ballast system characteristics

Treatment Technology Factors 

• Treatment method 

• Treatment system pressure drops

• Equipment size and space requirements 

• Materials, equipment protection (IP rating) 

and hazardous spaces

• Power requirements

• Impacts on ballast tank and pipe corrosion

• Health and safety (handling, operation and 

maintenance)

General Treatment System Considerations

• Proven effi cacy and offi cial approvals

• Vendor qualifi cations and reputation

• Maintenance requirements and system 

reliability

• Simple operation (control and monitoring)

• Life cycle costs

Challenges for Installation Engineering 

• Intake/discharge isolation 

(cross-contamination)

• Sampling and in-service testing

• Maintaining ballasting fl exibility

Ship Type & Capacity

In most instances, the ship type will be the 

largest single determinant in selecting a 

suitable treatment system. For this purpose 

it is convenient to consider two groups of ship 

types: high ballast dependent ships such as 

tankers and bulkers; and low ballast dependent 

ships such as containerships, general cargo ships, 

18 • ABS BALLAST WATER TREATMENT ADVISORY
ABS BALLAST WATER TREATMENT ADVISORY • 19

and cruise ships. These groupings are based 

on differences in total ballast capacity, amount 

of discharge at any one port and ballast fl ow 

rates.

As the data in Table 8 indicates, there is a wide 

range of ballast capacities and pumping rates 

common to the commercial ship sector. Notably, 

the high ballast-dependent vessels regularly sail 

in ballast only conditions (without cargo). Their 

pump rates are designed to allow full load or 

discharge in a fi xed period of time to facilitate 

rapid port turnaround times (typically 12, 18 or 

24 hours for ballast operations). The low ballast 

dependent vessels generally have smaller ballast 

capacities and also may rarely undertake a ballast 

only voyage. Their pumps do not typically have 

to handle a full load of ballast on a regular basis. 

Movement of ballast is more limited and often is 

a shift (one tank to another to adjust trim or heel) 

rather than a simple full ballast load/discharge 

operation.

Ballast Water Handling Practices

The proper sizing of a treatment system depends 

on the amount of ballast that has to be treated 

at any given port, more so than the total ballast 

capacity or maximum fl ow rate. If, through active 

ballast management, discharge can be reduced 

or eliminated then treatment demands decrease. 

For example, most containerships rarely need to 

discharge a full ballast load at any one time. 

It also should be noted that a large amount of 

the treatment system prototype testing is done 

on moderately sized systems (< 250 m3/hour) 

or is scaled up from other industries and not all 

systems scale up well to the sizes required for the 

high ballast capacity pumping rates or volumes 

of several thousand m3/hour. 

Another ballast practice issue that impacts 

treatment selection is how accumulated mud and 

silt in the ballast tanks is addressed. This residue 

itself can contain invasive species even when the 

tank is empty of water (a NOBOB – no ballast on 

board condition). Even if ballast is loaded locally 

it can become contaminated by the residue in the 

tank. This may necessitate the treatment of ballast 

water on discharge as well as loading. If there is 

little mud accumulation and the tanks are cleaned 

regularly, this may be less of a concern and the 

treatment system can be selected accordingly. 

For those ships constructed in or after 2009, 

compliance with G12 guideline is to be applied.

Ballast Water Characteristics

Turbidity, salinity and silt content can impact 

the effi cacy, maintenance or reliability of some 

technologies. If regular calls in a port are planned 

where the water has high mud/silt content or has a 

low salt content (fresh or brackish) this should be 

considered in the treatment technology selection.

Vessel Service Characteristics

The vessel service or trade route may also be 

critical for treatment system selection. For example, 

certain ship types may not be discharging ballast 

in the US so there will be no concern for US 

regulations and the key regulatory requirement 

and effi cacy standards will be those from IMO. If 

treatment options for local requirements are too 

expensive, then operators trading to those areas 

only occasionally may opt to forego shipboard 

installation of additional treatment capability and 

instead adjust their ballast management to avoid 

discharge or pay high use costs for a shore/port 

based system (where available).

Common Ballast System Characteristics

There are also a number of other vessel features 

related to ship type that are not exclusive to the 

high/low ballast dependent categorization defi ned 

above yet have an impact on treatment system 

selection. These include the number of separate 

ballast systems (e.g., oil tankers often have two, 

one in way of the cargo area and one aft of the 

cargo), whether eductors are used to supplement 

ballast discharge, small or crowded engine rooms, 

or explosion proof ballast equipment requirements. 

How these features represent design challenges for 

treatment systems are discussed in the following 

sections. 

Diagram of Ballast Water Management System
20 • ABS BALLAST WATER TREATMENT ADVISORY

Table 8: Ballast Water Capacity & Ballast Pump Rates by Vessel Type

Vessel Category Vessel Type Representative Ballast 

Capacity (m3)

Representative 

Pump Rate (m3)

High Ballast 

Dependent 

Vessels

Bulk Carriers

Handy 18,000 1,300

Panamax 35,000 1,800

Capesize 65,000 3,000

Tankers

Handy 6,500 1,100

Handymax-Aframax 31,000 2,500

Suezmax 54,000 3,125

VLCC 90,000 5,000

ULCC 95,000 5,800

Low Ballast 

Dependent 

Vessels

Containerships

Feeder 3,000 250

Feedermax 3,500 400

Handy 8,000 400

Subpanamax 14,000 500

Panamax 17,000 500

Postpanamax 20,000 750

Other Vessels

Chemical Carriers 11,000 600

Passenger Ships 3,000 250

General Cargo 4,500 400

Ro/Ro 8,000 400

Combination Vessels 7,000 400

Note: Representative values are nominal values that refl ect a combination of data sources and vessel sizes in each category.

Treatment Technology Factors 

The second most important set of factors in 

selecting a suitable treatment system, after ship 

type and service, are the operating characteristics 

and requirements of the individual treatment 

technologies. As noted in Section 2 of this 

Notice, BWT Technologies, there are numerous 

technologies being actively researched and 

implemented that should be able to meet at least 

the IMO discharge standards. These technologies 

differ in method and rate of application, scalability, 

required holding time, power and related system 

requirements, impacts on corrosion and inherent 

safety. Each ship’s design, as well as an owner’s 

particular operating practices and internal risk 

assessments, will determine how important each 

of these factors is in the selection process. Taken 

together, these factors and how the treatment 

systems address them, indicate the level of analysis 

required for effective implementation of the 

particular treatment system. 

In any case, the following endeavors to describe 

the more important factors to help provide a 

framework for system consideration. 

Treatment Method

The methods and technologies being considered 

for ballast water treatment can be grouped by basic 

approach as follows:

• Mechanical systems (fi ltration or separation)

• Physical disinfection (UV radiation, cavitation, 

de-oxygenation, etc.)

• Chemical treatment (biocides and electrochlorination)
less than 1 bar to about 2 bar. In some cases, 

back pressure valves may need to be added to 

the system after a separator to provide suffi cient 

backpressure for clearing out sludge and/or selfcleaning. If the installation requires signifi cant 

lengths of new ballast piping and valving then 

some additional pressure drops will be introduced 

that could prove signifi cant. 

The self cleaning or back-fl ushing operation will 

redirect some of the ballast fl ow directly overboard 

and reduce the fl ow rate into the tank further. 

Some cyclones redirect as much as 5 percent to 

10 percent of the fl ow stream for sludge removal. 

The pressure drops and self cleaning process will 

impact in-service fl ow rates and system design 

pressure. For most ships it is not expected that 

ballast pumps will need to be upgraded. However, 

the actual fl ow rates of ballast delivered to the 

tanks achievable with the selected system must 

be used when evaluating ballasting times and 

operation of the treatment system. It could be that 

ballasting with some treatment systems with high 

pressure drops and self-cleaning systems could 

take 20 percent longer than ballasting without 

treatment.

It should also be noted that at some level of 

additional system resistance, gravity ballasting 

may no longer be feasible because the pressure 

differentials with the sea water are reduced and 

acceptable fl ow rates cannot be maintained. 

Some separation equipment simply cannot run 

without suffi cient system pressure drop. This will 

ultimately increase the total power required for 

the ballasting operation because the main pumps 

will have to be operated for a longer period. 

Each system has a few fundamental 

characteristics that impact its suitability for 

certain ship types, service or fl ow rates. Most of 

the treatment systems use a combination of two 

or more of these technologies to overcome an 

individual technology’s shortcomings.

Mechanical Systems

These require redirecting the full ballast 

fl ow through fi lters, hydrocyclones or other 

separators. For high volume applications, the size 

of the equipment required can be problematic. If 

they are used during ballast discharge, the fi ltrate 

must be maintained on board. High sediment 

loads can cause problems for fi lters.

Physical Disinfection

Ultraviolet radiation and cavitation require 

processing of the entire ballast fl ow but holding 

time is not required as treatment is complete 

once the water passes through the equipment. 

UV exposure is usually done at both intake and 

discharge. Its effectiveness degrades with cloudy 

or turbid water that restricts light penetration. 

De-oxygenation can be done at intake to the 

full ballast fl ow or directly in the ballast tanks 

with bubblers. However, the full kill rates may 

take several days to achieve so the ballast tanks 

must also have a closed vent system and be fully 

inerted. 

Chemical Treatment

These treatments are dosed into the existing 

ballast piping during intake or directly into the 

ballast tanks. The dosage rates must be adjusted 

to provide the desired kill rate. The chemicals are 

usually lethal within several hours of treatment 

so long holding times are not required. However, 

the chemicals must be 

neutralized or be allowed 

to become biologically 

ineffective before the ballast 

water can be considered 

safe for discharge.

Treatment System 

Pressure Drops

The treatment systems that 

process the full ballast fl ow 

through fi lters, separation 

systems or venturi’s, create 

added resistance to ballast 

fl ow. The pressure drops for 

such elements vary, with 

most systems claiming from 

ABS BALLAST WATER TREATMENT ADVISORY • 21
22 • ABS BALLAST WATER TREATMENT ADVISORY

Equipment Size & Space Requirements

Treatment systems come in all shapes and sizes. 

The footprint requirements can vary from 1 to 

25 m2 for a system that can handle 200 m3/hour. 

For a 2,000 m3/hour system the space requirements 

can be 1 to 100 m2. Systems that use fi ltration or 

require generating equipment for disinfection, inert 

gas generators for example, tend to increase in size 

with ballast fl ow rates more than other systems that 

treat with chemical dosing. 

Another very important space consideration is 

the ballast piping itself. If the treatment system 

requires new branch lines to be installed, this can 

sometimes have an even greater impact on the 

space requirements than the treatment equipment 

itself. In most engine rooms, the ballast piping 

is the largest pipe used. On small containerships 

with medium capacity pumps it can be over 250 

mm. In the high ballast capacity ships it can easily 

be over 500 mm diameter. It can be a challenge 

to fi nd room for tie-in points to the manifold area 

around the ballast pumps as well as space in the 

ER to run signifi cant lengths of pipe to remote 

locations if suffi cient room for a piece of treatment 

equipment is unavailable. Systems that do not 

require redirecting main ballast fl ow certainly have 

an advantage in this case. 

In addition to the total or overall size of the 

treatment equipment, the system’s modularity may 

also impact the ease with which it can be installed 

in an existing engine room. Taking delivery of a 

system preassembled on a skid and expecting it to 

be installed in a single lift is unrealistic unless it is 

going in at new construction. To reduce installation 

costs and time, system components will usually 

be lifted and fi tted separately. So the ability of a 

system to be easily broken down into modules of 

convenient size and located in various areas in the 

engine room gives the installer many more options 

for completing the work. 

Not to be overlooked in the search for space for 

system installation is the need to provide for 

Table 9: Important Treatment Method Characteristics

Treatment 

Process Method of Treatment When Applied Time for Lethality

Effort on 

Corrosion

Chlorine 

Generation 

Use electrolytic cell to generate chlorine and bromine 

that act as biocides. Next, sodium sulfate neutralizes 

the ballast water prior to discharge. As long as free 

chlorine exists in the tank, biocide will be active so 

dosage can be adjusted to keep biocide always active.

At uptake and 

neutralize at 

discharge

Hours

High dosage levels 

promote steel 

corrosion

Chemical 

Application

Mix proprietary chemicals with the ballast water 

in metered dosage rates at intake to kill living 

organisms. Chemicals degrade over time so 

ballast will be safe to discharge.

At uptake via eductor 24 hours

High dosage levels 

promote steel 

corrosion

Filtration & 

Radiation

Filtration of the incoming water, usually with 

self-cleaning 50 micron fi lters, in parallel with discharge 

of fi ltrate to the waters where intake takes place. 

Ballast water is exposed to a form of radiation, such as 

UV energy or other hydroxyl radical generator, 

to kill smaller organisms and bacteria.

At uptake for fi lter 

and UV and at 

discharge for UV

At treatment No effect

De-oxygenation

Mix inert gas generated on board with the ballast 

water, either by a venturi eductor or by bubbling from 

pipes in the tanks. This removes oxygen from the water 

and lowers pH, therefore killing the living organisms. 

This process requires the atmosphere in the ballast 

tank be maintained in an inert condition.

At uptake for some 

systems and in tanks 

for others

4 to 6 days Relatively less 

corrosive

Ozone 

Generation

Ozone is generated on board and acts as a biocide. 

It is applied during the ballast pumping process by 

eductor either at uptake or discharge. It can 

be combined with fi ltration or other methods 

of treatment.

At uptake for 

some systems and 

at discharge 

for others

Up to 15 hours

Limited effect as 

ozone has short 

life. If treated 

at discharge, no 

effect.
ABS BALLAST WATER TREATMENT ADVISORY • 23

adequate access to the equipment for maintenance. 

This can include ladders and platforms, additional 

lighting, lifting eyes or crane rails, space for 

storage and handling of consumables and 

cleaning of internal components (as required). 

Space requirements for storage and handling of 

chemicals used in treatment systems should also 

be considered. This space can be outside the 

engine room and may require fi re fi ghting system, 

ventilation system, etc. Requirements related to the 

Material Safety Data Sheet (MSDS) are described 

later in this Advisory Notice.

Materials, Equipment Protection (IP Rating) 

& Hazardous Spaces

A ballast water treatment system must meet all 

the normal requirements for shipboard materials, 

equipment protection and hazardous space safety. 

The materials used in the system components 

and the level of equipment protection (IP rating) 

provided should be reviewed at the type approval 

stage and certifi ed as to be in compliance with the 

Class requirements for similar equipment installed 

in similar locations on board. One important 

aspect of this approval is review of the materials 

for fi re rating if the review authority deems the 

treatment system an ‘essential’ system. In that case, 

some plastic pipe materials may not be allowed. 

Additionally, valve materials and remote operation/

shut downs may be required. These issues are not 

normally a concern for shipowners, unless they 

wish to specify higher grade materials for longer 

design service life and lower maintenance costs. 

Critical to selecting a system however, is an 

understanding of the restrictions that may be 

placed on equipment location due to the specifi c 

regulations regarding the class of equipment that 

can be placed in a hazardous space. Equipment 

placed in the engine room does not have special 

explosion (EX) requirements whereas equipment 

in the pump room of an oil tanker must be 

intrinsically safe (EX ia or EX ib), except that 

explosion proof lighting enclosures and lights 

are allowed in pump rooms. Further, ballast from 

tanks adjacent to cargo oil tanks cannot be run 

through pipe in the engine room. Large treatment 

systems or ones that use UV lamp banks (which 

cannot be made intrinsically safe) may fi nd these 

requirements especially diffi cult to overcome. 

Recent rule developments have opened up the 

previously strict interpretations of the electrical 

equipment requirements by allowing, “...electrical 

equipment, cables and wiring which do not 

conform to the standards may be installed in 

hazardous locations based on a risk assessment to 

the satisfaction of the Administration, to ensure 

that an equivalent level of safety is assured.” 

(Refer to the amendment to SOLAS Reg. II-1/45.11 

which entered in force on 1 July 2006 for ships 

constructed after 2007.) The installation of nonintrinsically safe equipment in the pump room 

could be considered on a case by case basis taking 

into consideration the equipment within the 

pump room, the arrangement of the equipment, 

the number of air changes, etc., subject to the 

standards, interpretation and risk assessment 

approach of the approving authority.

Power Requirements

Electrical power consumption by ballast water 

treatment systems is potentially a signifi cant 

hurdle for some technologies on the high ballast 

dependent ships. Large power consumers such as 

UV light banks, electrolytic chlorination systems 

and de-oxygenation systems can require 150 to 

over 200 kW for a 2,000/m3

 treatment fl ow rate. 

If these systems must operate when other large 

shipboard consumers are also operating, total 

ship service electrical generating capacity may 

be insuffi cient. 

The large electrical loads are also the main 

operating cost for these systems. In contrast, 

treatment systems that rely on chemical biocides 

and preparations that can be dosed into the ballast 

fl ow have an almost insignifi cant electrical load 

impact but require storage space, handling and 

dispensing equipment.
24 • ABS BALLAST WATER TREATMENT ADVISORY

Impacts on Ballast Tank & Pipe Corrosion

For all ships, but especially the high ballast 

dependent ships, the battle against steel wastage 

due to salt water-induced corrosion can be the 

single largest maintenance cost as the vessel ages. 

Treatment systems that change the chemical 

composition of the ballast water and/or the 

atmosphere in the ballast tanks can impact the 

corrosion rates in the tanks and piping. If not 

designed and handled properly, treatment systems 

may also damage ballast tank coatings resulting 

in increased coating maintenance and ultimately 

increased corrosion as well. 

Systems that remove oxygen and maintain an inert, 

oxygen-deprived condition in the tanks can offer 

signifi cant reductions in corrosion rates. Some 

of the change in oxidation rate is attributable to 

changes in pH caused by the treatment. Some 

vendor studies have actually concluded that savings 

on steel and coating renewals over the life of the 

vessel are much greater than the life cycle costs 

of the treatment systems. Alternatively, many of 

the chemical biocides and preparations, including 

ozone, have been linked to increased corrosion 

rates. 

Experimental data is not always conclusive 

regarding the impact of chemical disinfectants 

in actual service conditions in ships’ ballast 

tanks with standard tank coatings and anodes, 

normal cycling of ballast levels and chemical 

concentrations required for treatment. Even 

de-oxygenation systems can cause accelerated 

corrosion if they completely remove the oxygen 

and create a condition that promotes anaerobictype, microbiologically-infl uenced corrosion. This 

could be in the form of acid-producing bacteria 

(APB) and sulfate-reducing bacteria (SRB). The 

condition may be accentuated if there is an 

alternating oxygenated/de-oxygenated condition. 

In order for de-oxygenation to be benefi cial for 

corrosion protection, it has to reduce the oxygen 

levels suffi ciently to slow oxidation and kill any 

biofi lms that might form, but not so low as to 

provide an atmosphere conducive to the growth 

of APBs and SRBs. 

With the currently available data, it is diffi cult to 

predict, with a high degree of confi dence, exactly 

how different treatment systems will change 

corrosion rates. At this point, it is necessary to 

move forward with an understanding of this 

uncertainty and plan maintenance and inspection 

intervals to suit expected risks appropriately. 

Coating manufacturers should also be consulted 

regarding the reaction of their coatings to the 

planned additives. Only when suffi cient operational 

experience is gained with given treatment systems 

will clearer guidelines be possible. 

Health & Safety (Handling, Operation 

& Maintenance)

The use of chemical biocides and other active 

substances on board ships raises a concern over the 

health and safety of those responsible for operating 

the equipment and handling the materials, as well 

as the risk of unintentional discharge into the 

environment. Treatment systems that use active 

substances or preparations must undergo a strict 

review and approval process to identify persistence, 

bioaccumulation and toxicity. If the system is 

given fi nal approval by IMO, this indicates that 

persistence, bioaccumulation and toxicity are 

below threshold levels and that, if the substances 

are handled as directed, they are considered safe 

for shipboard use. 

Every system using active substances should 

be provided with a Material Safety Data Sheet 

(MSDS) which describes the proper storage and 

handling procedures as well as the information 

on the quantity to be added to the ballast water 

and the maximum allowable concentration of the 

substances in the treated water. Further, the system 

should not permit exceedance of the maximum 

dosage and maximum allowable discharge 

concentration at any time. 

It is important to note that limits for the level of 

active biocides that may remain in the discharged 

ballast can also be regulated by local water quality 

regulations and can vary by port. If discharging in 

sensitive areas, a treatment system with diffi cult to 

control biocide inactivation might not be the right 

choice. At the very least, the manufacturer should 
be requested to provide written confi rmation that 

the effl uent meets the requirements within the local 

jurisdictions that the vessel is likely to operate in. 

Compliance with these guidelines should indicate 

that all reasonable precautions have been taken 

to protect the health and safety of the crew and 

environment. Nevertheless, it does put an added 

hazardous material management burden on 

the crew. The skill and training of the crew and 

their ability to manage this safety risk should be 

considered when selecting a treatment system. 

General Treatment System 

Considerations

All ballast water treatment technologies share 

certain common selection criteria that should be 

considered in addition to the ship and technology 

specifi c factors. 

Proven Effi cacy & Offi cial Approvals

First and foremost, a system must meet the 

discharge standard applicable to the vessel’s 

voyage where ballast discharges are planned or 

likely. General worldwide service is covered by 

the IMO Convention’s requirements but some 

local authorities, such as the state of California, 

have more stringent requirements and earlier 

implementation dates. A certifi cate of type 

approval from a fl ag Administration would 

indicate that, under test conditions, the system 

meets the discharge standards required. Unless the 

installation is part of a prototype or type approval 

test, the equipment supplier should be able to 

produce the type approval certifi cate. Systems 

with type approval are also listed on the IMO 

website. This formal approval of the equipment 

will be necessary if the vessel is to obtain the 

IMO Ballast Water Management Certifi cate 

showing compliance with the BWM 

Convention following successful 

system functional tests on board. 

Vendor Qualifi cations & Reputation

As with any piece of equipment, the 

ability of the vendor or manufacturer 

to deliver the product on time 

and in the quantities requested is 

very important. However with this 

emerging technology, the production 

capacity is unproven and still 

very small in most cases. Some 

manufacturers may suffer from long 

lead times on orders, especially if 

demand increases rapidly. Even though production 

facilities are subject to quality control review by 

the type approval authority, until a track record is 

established, manufacturing quality and reliability 

can be an unknown. Those systems relying on 

existing technologies or marine components will 

have an advantage in this regard. 

Maintenance Requirements 

& System Reliability

There is insuffi cient experience with treatment 

system options to establish a good baseline for 

system reliability. Those systems relying on 

existing technologies or marine components will 

be able to provide better reliability estimates. 

Lacking in-service experience, an indication of 

reliability risk may be available by considering the 

system complexity. Filters, UV light chambers and 

simple chemical dosing systems are among the 

least complex options and regular maintenance 

is possible with ship’s crew. Electrochlorination 

and other chemical generating systems as well as 

systems with more than two stages of treatment 

can be considered among the most complex. 

Simple Operation: Control & Monitoring

All treatment systems should provide a simple 

to use remote control panel at or near the main 

ballast control panel. It should include indicator 

lights for key valves and system operations and 

an on/off control. Most systems will provide 

main control panels near the equipment that 

allow local operation but also monitor system 

operation. Beyond this, it is up to the owner how 

far integration of the treatment system is carried 

in the main control/alarm/monitoring system. If 

full integration is required, additional tie-ins with 

system electronics may need to be special ordered 

from the manufacturer.

ABS BALLAST WATER TREATMENT ADVISORY • 25
26 • ABS BALLAST WATER TREATMENT ADVISORY

Life Cycle Cost

The bottom line concern for owners is the true life 

cycle cost of the system. Acquisition costs are the 

most straightforward to determine because they are 

directly quoted by the vendors and include all their 

sunk costs for research and development, approvals 

and certifi cation. Installation costs vary from 

system to system and are more diffi cult to quantify. 

Installation costs include changes to existing 

piping, equipment and structure, as well as the 

direct equipment installation, connection, startup, 

testing and survey by the approval authority. Most 

systems will require some out of service time for 

the ship in order to complete the installation but 

none of those currently on the market is likely to 

require drydocking. 

Establishing both installation and operating costs 

is diffi cult as both will vary signifi cantly depending 

upon the type and size of ship, the system selected 

and prevailing market conditions. When evaluating 

the probable operating costs of a system, the 

following should be taken into account:

• Energy required to operate the system 

including electric power and fuel for generating 

treatment materials (ozone, inert gas and other 

biocides)

• Consumables such as chemicals, lamps and 

fi lter elements 

• Crew labor to operate and maintain the system, 

including training

• Periodic maintenance, servicing and 

component replacement 

Challenges for Installation 

Engineering

Many of the challenges related to engineering the 

actual installation of a ballast water treatment system are addressed in the section describing the 

treatment technology factors. These challenges can 

be especially acute when installing a system on an existing vessel. Finding solutions 

to treatment system back 

pressure and potential fl ow 

rate reductions, power consumption demands, control 

system integration and space 

requirements, as a well as 

access for installation, can 

be diffi cult and costly. 

As these are worked out with the vendor, design 

engineer and class the following additional factors 

should be taken into consideration as a successful 

installation can still be problematic if they are not 

properly addressed.

Intake/Discharge Isolation: 

Cross-Contamination

When designing the piping system modifi cation 

required for treatment system installation, care 

is required to prevent any accidental crosscontamination of intake and discharge water. 

This is a concern for systems that redirect the 

main ballast fl ow. Cross-contamination can occur 

if contaminated water, either from the sea chest 

or a tank which may require treatment prior to 

discharge, passes through a pipe that is shared by 

the treated ballast water being discharged. Valves 

which do not provide a reliable seal may also allow 

some contamination of treated ballast.

The ideal isolation of intake and discharge fl ows 

is not always possible. However, in two pump 

ballast systems where fl exibility in the ballasting/ 

deballasting time is acceptable, it is recommended 

that one pump be dedicated for ballast intake and 

one for discharge. Transfers between tanks should 

be done by the ‘discharge’ or ‘clean’ pump unless 

treatment is active in the ballast tanks (as with deoxygenation). 

Sampling & In-Service Testing

Port State Control and other authorized regulatory 

offi cers may, at any time for the purpose of 

determining whether the ship is in compliance 

with the discharge requirements, come on board 

and take samples of the ballast water. Designing 

proper and convenient sampling and testing 

facilities should be considered an important part 

of the installation engineering. As noted in Section 

1 of this Notice, IMO Guideline G2, Guidelines 

for Ballast Water Sampling, calls for sampling to 

be simple, rapid, applicable at the point of ballast 

Invasive Species

The map shows the estimated 

distribution of invasive marine 

species. Many marine 

organisms are carried 

in ballast water or on 

the hulls of ships.

Sources: Benjamin S. Halpern, National Center for Ecological Analysis & Synthesis Graham Roberts, Jonathan Corum/The New York Times

High
discharge and safe to the ship and crew. G2 further 

contains very specifi c requirements for size, 

location and maintenance guidelines of isokinetic 

sampling ports. 

Unfortunately, sampling and analysis methodologies to test for compliance with the Convention 

are still in development. While research is ongoing, there currently exists no specifi c guidance for 

the best way to take, handle and analyze samples. 

There are no protocols for the volume of water 

required, the conditions in which the samples are 

stored (e.g., light, temperature, storage container), 

how biota collection from a sample is accomplished, the statistical method used to count biota, 

nor direction on sample disposal (can it simply be 

discharged?).

The sample volume and method for biota collection 

are key to the design of the sampling facilities. 

They should include fl exible hoses, holding tanks 

and work area. Unfortunately, with the sampling 

port required to be near the discharge that is often 

located in the engine room where space is limited, 

handling of signifi cant quantities of water may be 

diffi cult to arrange or simply impractical.

Maintaining Ballasting Flexibility

Ideally, full ballast system operational fl exibility can 

be maintained with the selected treatment system. 

However, providing for the treatment of all isolated 

ballast systems on board, maintaining maximum 

fl ow rates at all times and providing for stripping 

systems (eductors) to continue to be used, may 

not be necessary for particular ships 

or even cost effective. For example, a 

vessel that does not move signifi cant 

ballast during normal operations may 

not need the treatment system to handle 

full pumping fl ow rates. Eductor-based 

stripping systems may not need special 

attention if the full treatment course is 

completed in the tank before discharge, 

or if the eductor power water can be 

taken from a treated source. Dedicating 

ballast pumps for intake and discharge 

may reduce fl exibility but may simplify 

piping connections and lower the risk of 

cross-contamination. 

Obtaining As-built Vessel Information

For most existing vessels, detailed 

as-built drawings of the ship’s ballast 

piping system and engine room 

arrangement may not be readily 

available. Nevertheless, detailed dimensional 

information is required for all vessel systems 

and outfi ts that may be impacted by the new 

equipment in order to properly evaluate locations 

for equipment installation and piping runs and 

avoid interferences. Further, installation sequence 

planning requires a detailed understanding of 

routes for equipment access and the minimum 

clearances available. Availability of suitable 

equipment lifting points also needs to be 

documented. Gathering of this information is 

important to a smooth installation (as well as 

possible treatment selection decisions) and should 

not be overlooked. Advanced techniques using 

3-D laser scanning technology may be useful in 

this regard. 

Making a Treatment System Selection

With such a wide array of ballast water treatment 

technologies available and the numerous, often 

competing constraints on any one system, the 

evaluation and selection of the best equipment 

is not straightforward. There are many factors to 

consider. The issues highlighted in this Advisory 

provide an overview of the principal considerations 

that an owner/operator should bear in mind when 

specifying a ballast water treatment solution. 

As a fi rst step in the evaluation process, the 

information contained in Table 10 should be 

considered. This was compiled to summarize, 

in a general sense, the suitability of the primary 

treatment technologies with a range of vessel 

types and sizes.

ABS BALLAST WATER TREATMENT ADVISORY • 27
28 • ABS BALLAST WATER TREATMENT ADVISORY

As can be seen, in only a few cases are treatment 

technologies deemed unsuitable for particular 

vessel types. The selection process then must take 

up the details. As an aid for use in this process, a 

checklist of key questions and considerations has 

been included in the System Evaluation Checklist 

Section at the end of this Advisory Notice. This 

can be useful in establishing criteria. The value 

and rating of each factor is left up to the individual 

responsible for making the purchasing decision.

Table 10: Suitability of a Ballast Treatment System Type to a Vessel Type

Vessel Category Vessel Size Range Chlorine 

Generate

Chemical 

Apply

Filter & 

Radiate Deoxygenate Ozone Generate

Bulk Carriers

Handy-Handymax < 60,000 DWT Yes Yes Yes Yes Yes

Panamax-Kamsarmax < 60,000-90,000 DWT Yes Yes Yes Yes Yes

Capesize >1200,000 DWT Except Large Yes Except Large Yes Yes

Tankers

Handy < 35,000 DWT Some Systems Yes Some Systems Yes Some Systems

Handymax-Aframax 35,000-120,000 DWT Some Systems Yes Some Systems Yes Some Systems

Suezmax 160,000-180,000 DWT Some Systems Yes Some Systems Some Systems Some Systems

VLCC 200,000-320,000 DWT No, Too Large Yes No, Too Large Some Systems Some Systems

ULCC > 320,000 DWT No, Too Large Yes No, Too Large Some Systems Some Systems

Containerships

Feeder < 500-3,000 TEU Yes Yes Yes Yes Yes

Panamax 3,000-4,500 TEU Yes Yes Yes Yes Yes

Postpanamax 4,500-9,000 TEU Yes Yes Yes Yes Yes

Ultralarge > 9,000 TEU Yes Yes Yes Yes Yes

Other Vessels

Passenger Ship All Sizes Yes Yes Yes Yes Yes

Gas Carrier All Sizes Except Large Yes Except Large Some Systems Some Systems

Chemical Carrier All Sizes Some Systems Yes Some Systems Some Systems Some Systems

RORO All Sizes Yes Yes Yes Yes Yes

Combination Vessel All Sizes Yes Yes Yes Yes Yes

General Cargo All Sizes Yes Yes Yes Yes Yes

Fishing Vessels All Sizes Yes Yes Yes Yes Yes

OSVs All Sizes Yes Yes Yes Yes Yes

Note: For tankers, chemical carriers and gas carriers, some systems are not suitable, either because they are not designed to be 

installed in a hazardous atmosphere such as a tanker pump room or because they are not produced at the high capacity required 

for large tankers.
ABS BALLAST WATER TREATMENT ADVISORY • 29

Vessel Ballast System Particulars 

Owner Supplied Data

1. Ballast system arrangement

a. Total ballast capacity

b. Number of ballast tanks

c. Minimum/maximum ballast tank size

d. Are ballast tanks contiguous with cargo oil or other hazardous cargo tanks?

e. Is there a dedicated set of heel control tanks (FW or SW)?

f. Number of separate ballast systems (not served by same pump)

g. Proper and convenient sampling and testing facilities 

2. Ballast system equipment

a. Number of ballast pumps and rating (fl ow rate and pressure for each)

b. Overall ballast rate (m3

/hour)

c. Ballast pump location (ER, pump room, main deck, etc.)

d. Main ballast line confi guration (ring main or single line)

e. Type of stripping system, if any

f. Are all ballast system valves remotely operated?

g. Are ballast pumps/piping shared with other systems (bilge, fi re, cooling water)?

h. Number and location of sea chests (height above bottom)

i. Diameter of main ballast line to/from pumps

j. Number and size of spare circuit breakers on main switchboard

k. Estimated spare electrical capacity during ballasting operations

Evaluation Checklists
30 • ABS BALLAST WATER TREATMENT ADVISORY

Ship & Service Characteristics that Impact BWT Selection 

Owner Supplied Data

1. Ship type and capacity

a. Ship type: high ballast dependent or low ballast dependent

2. Ballast water handling practices 

a. On average, how much ballast is loaded or discharged at any given port?

b. What are the time constraints on ballast intake (how fast must it happen)?

c. Maximum required fl ow rate for intake of ballast 

d. What are the time constraints on ballast discharge (how fast must it happen)?

e. Maximum required fl ow rate for discharge of ballast

f. Sediment build up in tanks (little, moderate, signifi cant) 

g. Is treatment required for possible NOBOB condition?

h. Minimum time ballast is held in a tank between port calls

3. Ballast water characteristics

a. Are there freshwater ports encountered where ballast is taken in?

b. Minimum salinity of brackish water encountered 

c. Turbidity or silt content of port water (low, moderate, heavy)

4. Vessel service characteristics

a. Any unique service constraints or trading patterns regarding ballast use?

b. Is there trade to special BWT zones: California, Great Lakes, Australia, etc.?

c. Does active ballast management allow zero ballast discharge in some/all ports?

5. Ballast system characteristics

a. What are the gravity intake/discharge practices?

b. Can internal ballast transfer for trim, heel, bending moment control be 

 easily accomplished?

evaluation checklist
ABS BALLAST WATER TREATMENT ADVISORY • 31

Treatment Technology Factors 

Vendor Supplied Data

1. Treatment method 

a. Description of technology offered (all stages)

b. For UV system: lamp type, required minimum intensity and water clarity

c. For chemical: Required minimum dosage rate and minimum holding time

 Neutralizing agents (how created, stored, dosed?)

 How long before safe to discharge?

 Chemicals generated on board or supplied as preparations?

d. For de-oxygenation: How much inert gas required?

 Minimum holding time

2. Treatment system capacity

a. Overall treatment capacity (m3)

b. Overall treatment rate (m3

/hour)

3. Treatment system pressure drops

a. Expected pressure drops added by treatment system to main ballast fl ow

b. Quantity of ballast redirected for cleaning or sludge discharge

c. Is gravity intake/discharge possible with this system?

4. Equipment size and space requirements 

a. Total space required for treatment equipment

b. Size of largest single component 

c. Weight of largest single component

d. Space required for maintenance (element removal, etc.)

5. Materials, equipment protection (IP rating) and hazardous spaces

a. IP rating of components

b. EX rating of components

c. Any special risk assessments performed to date for hazardous space installations?

6. Power requirements

a. Average and maximum power requirements and operating voltage

b. Duration of maximum power consumption as function of ballast process

7. Impacts on ballast tank and pipe corrosion

a. Is there published R&D available regarding the impact on tank and pipe corrosion rates?

8. Health and safety (handling, operation, maintenance)

a. Quantity of treatment chemicals needed (per ton of ballast water treated) 

b. For active substances: a copy of the MEPC fi nal approval with recommendations

c. For active substances: Material Safety Data Sheets

evaluation checklist
32 • ABS BALLAST WATER TREATMENT ADVISORY

General Treatment System Considerations 

Vendor Supplied Data

1. Proven effi cacy and offi cial approvals

a. Copy of Type Approval Certifi cate issued by, on behalf of, a Government

b. System limitations or operating guidelines from Type Approval process

2. Vendor qualifi cations and reputation

a. Annual production capacity of manufacturer

b. Which components are custom made or incorporate new/novel technology?

c. How many units have been built at the factory to be used for this installation?

d. Client referrals for previously installed systems

3. Maintenance requirements and system reliability

a. How many units of similar capacity have been installed?

b. What is average duration of operating experience per unit?

c. What is standard maintenance protocol?

d. What is expected service life?

4. Simple operation: control and monitoring

a. Type of remote control system included

b. Ease of connection to primary control and monitoring system

5. Life cycle costs

a. Estimated power consumption for normal ballast operations

b. Fuel consumption expected for inert gas generation

c. Cost of consumables (chemicals, lamps, fi lter elements)

d. Expected frequency of resupply of consumables for planned system size

e. What major components are most likely to need replacement within 10, 15, 20, 25 years? 

 What is their cost?

evaluation checklist
ABS BALLAST WATER TREATMENT ADVISORY • 33

Challenges for Installation Engineering 

Owner Supplied Data

1. Intake/discharge isolation: cross-contamination

a. Can piping installation options provide good contamination protection?

b. Can intake and discharge pumps be isolated and dedicated to that service?

2. Sampling and in-service testing

a. Is there adequate space and facilities for sampling and testing?

3. Maintaining ballasting fl exibility

a. Can the treatment system options selected provide full ballast fl exibility?

4. Other

a. Is there space for all system components and ballast connections?

b. What are the access openings and routes for bringing in new treatment system components?

c. What are the access needs during system operation and maintenance?

d. Are switchboard modifi cations required?

e. Are control system modifi cations required?

References and Suggested Further Reading

Standards for Living Organisms in Ships’ Ballast Water Discharged in US Waters, Notice of Proposed Rulemaking, 

Preliminary Regulatory Analysis and Initial Regulatory Flexibility Analysis, USCG-2001-10486, June 2008

evaluation checklist
34 • ABS BALLAST WATER TREATMENT ADVISORY

Technical Information for Ballast Water Treatment Systems 

The following pages summarize the key technical and performance data for treatment systems, which 

are currently being offered on the market that are in various stages of approval as of the publication 

of this Advisory Notice.

It should be noted that some ballast water treatment systems which use chemical biocides and de-oxygent 

may require additional treatment prior to the water being discharged into receiving waters.

Systems with Type Approval Certifi cation

1. PureBallast System

2. Electro-CleenTM System (ECS)

3. OceanSaver® Ballast Water Management System 

4. Venturi Oxygen Stripping (VOS) System

5. Hyde GuardianTM Ballast Water Management System

6. NK-O3 Blue Ballast/Nutech O3

7. OptiMarin Ballast System (OBS)

8. Hitachi ClearBallast System

9. GloEn-PatrolTM System

Systems with Final Approval for Active Substances

1. Resource Ballast Technology/Unitor BWTS

2. JFE BallastAce System

3. HHI EcoBallast System

4. RWO CleanBallast System

5. Sedinox System

Appendix
ABS BALLAST WATER TREATMENT ADVISORY • 35

PureBallast System

Methods: Filtration + ultraviolet/TiO2 (AOT)

Operational Notes: PureBallast is based on advanced oxidation technology, or AOT. Titanium dioxide 

catalysts generate free radicals when hit by light.The radicals, whose lifetime is only 

a few milliseconds, break down the cell membrane of micro-organisms without the 

use of chemicals or the creation of harmful residues (the system was, nevertheless, 

approved under the G9 regime for Active Substances). PureBallast’s patented 

version of the AOT technology, known as Wallenius AOT, has been industrialized 

in a joint venture between Alfa Laval and Wallenius Water. 

 During ballasting, water is processed through the fi lter to remove any particles 

or organisms larger than 50 microns in size. It then passes through the AOT 

treatment to the ship’s ballast system. Back-fl ushing water is returned over board at 

the ballasting site. During deballasting, the fi lter is bypassed and the ballast water 

receives a second dose of AOT before being discharged overboard.

Manufacturer: Alfa Laval, Norway

Link/Reference: www.pureballast.alfalaval.com

Approval Status: Final Approval for Active Substances, July 2007

 Type Approval, June 2008, Norway

APPENDIX
36 • ABS BALLAST WATER TREATMENT ADVISORY

Electro-CleenTM System (ECS)

Methods: Electrolysis/electrochlorination

Operational Notes: Disinfection is carried out directly by the electrical potential and by the generation 

of free chlorine, sodium hypochlorite, hydroxyl radicals and electrochemical 

oxidation through the creation of ozone and hydrogen peroxide. 

Manufacturer: Techcross Company Ltd., Republic of Korea

Link/Reference: www.techcross.net

Approval Status: Final Approval for Active Substances, October 2008

 Type Approval, December 2008, Republic of Korea 

APPENDIX
ABS BALLAST WATER TREATMENT ADVISORY • 37

OceanSaver® Ballast Water Management System

Methods: Filtration + hydrodynamic cavitation + de-oxygenation (nitrogen) 

+ electrodialytic process

Operational Notes: After fi ltration intense pressure pulses are used to create hydrodynamic cavitation 

of suffi cient intensity to rupture cell membranes and destroy particles and 

organisms. The ballast water is then super saturated by the injection of nitrogen 

causing the oxygen dissolved in the water to be released, leaving the water in the 

tanks defi cient of oxygen. The released oxygen and nitrogen is evacuated from 

the tanks via a controlled ventilation arrangement usually through a pressurevacuum device so as to avoid the further natural release of nitrogen over time and 

to prevent potential contamination by outside air. The fi nal stage of treatment 

incorporates an isolated electrodialytic process which is based on the principles of 

an electrochemical activation technology. This is applied to a small portion of fl ow 

(greater than 5 percent by volume) producing a disinfectant which is returned to 

the main fl ow after the cavitation and the nitrogen saturation. This greatly enhances 

the disinfectant properties. The activated substances naturally degrade over a very 

short period of time. 

Manufacturer: OceanSaver AS, Norway

Link/Reference: www.oceansaver.com

Approval Status: Final Approval for Active Substances, October 2008 

 Type Approval, April 2009, Norway

APPENDIX
38 • ABS BALLAST WATER TREATMENT ADVISORY

Venturi Oxygen StrippingTM System

Methods: De-oxygenation + cavitation + lowering pH

Operational Notes: Inert gas is introduced into the ballast during intake through a venturi system. 

The cavitation caused in the venturi system damages the organism and is the 

fi rst stage physical treatment. The inert gas removes oxygen from the water and 

lowers the pH level. The ballast tanks are kept inerted to maintain the hypoxic 

condition. This condition kills living organisms during the holding period in the 

tank (one to 48 hours). There are no active substances used. 

Manufacturer: NEI Treatment Systems LLC, United States of America

Link/Reference: www.nei-marine.com

Approval Status: Type Approval, September 2008, Marshall Islands

APPENDIX
ABS BALLAST WATER TREATMENT ADVISORY • 39

Hyde GUARDIANTM Ballast Water Treatment System

Methods: Filtration + ultraviolet light

Operational Notes: During ballasting, water is processed through the fi lter to remove any particles 

or organisms larger than 50 microns in size. It then passes through the UV 

treatment and to the ship’s ballast system. Back-fl ushing water is returned over 

board at the ballasting site. During deballasting, the fi lter is bypassed and the 

ballast water receives a second dose of ultraviolet light before being discharged 

overboard. There are no active substances used. 

Manufacturer: Hyde Marine, Inc., United States of America

Link/Reference: www.hydemarine.com

Approval Status: Type Approval, April 2009, United Kingdom 

APPENDIX
40 • ABS BALLAST WATER TREATMENT ADVISORY

NK-O3 Blue Ballast System/Nutech O3

Methods: Ozone + thiosulphate neutralizer

Operational Notes: The conversion of oxygen into ozone is carried out by an electric discharge fi eld. 

Ozone is then injected into the ballast stream at the outlet of the ballast pumps 

and kills a percentage of invasive marine species by direct contact. The remainder 

of the invasive marine species are killed when the ozone reacts with bromine that 

naturally occurs in sea water to create other biocides. The ozone and bromine 

related biocides naturally decay. Only trace amounts of the bromine compounds 

remain in the treated water. If the levels are too high, a neutralizer injects 

thiosulphate to reduce them to acceptable levels. The ozone system produces a low 

concentration of active substances.

Manufacturer: NK Company, Ltd., Republic of Korea

 Nutech O3, Inc., Republic of Korea

Link/Reference: www.nkcf.com

 www.nutech-03.com

Approval Status: Type Approval, October 2009, Republic of Korea

 Final Approval for Active Substances, November 2009

APPENDIX
ABS BALLAST WATER TREATMENT ADVISORY • 41

OptiMarin Ballast System (OBS)

Methods: Filtration + ultravoilet light

Operational Notes: During ballasting, water is processed through the fi lter to remove any particles or 

organisms larger than 40 microns in size. It then passes through the UV treatment 

and to the ship’s ballast system. Back-fl ushing water is returned over board at the 

ballasting site. During deballasting, the fi lter is bypassed and the ballast water 

receives a second dose of ultravoilet light before being discharged overboard. There 

are no active substances used.

Manufacturer: OptimMarin AS

Link/Reference: www.optimarin.com

Approval Status: Type Approval, November 2009, Norway 

APPENDIX
42 • ABS BALLAST WATER TREATMENT ADVISORY

Hitachi ClearBallast Ballast Water Purifi cation System

Methods: Flocculent injection + magnetic separation + fi ltration

Operational Notes: Coagulation technology forms magnetic fl ocs by adding and agitating a coagulant 

and magnetic powder to the sea water to capture plankton, viruses, mud and sand. 

A high speed magnetic separator collects the magnetic fl ocs and the residual fl ocs 

are removed with a fi lter separator. Onboard storage of premixed fl occulants/

chemicals required. Accumulation, storage and disposal of sludge is required. 

Manufacturer: Hitachi Plant Technologies, Ltd. and Mitsubishi Heavy Industries, Ltd., Japan

Link/Reference: www.hitachi-pt.com

Approval Status: Final Approval for Active Substances, July 2009

Type Approval, March 2010, Japan 

APPENDIX
ABS BALLAST WATER TREATMENT ADVISORY • 43

APPENDIX

GloEn-PatrolTM System

Methods: Filtration + ultraviolet radiation

Operational Notes: During ballasting, water is processed through the fi lter to remove any particles or 

organisms larger than 50 microns in size. The ballast then passes through the UV 

treatment unit utilizing high intensity, medium pressure UV lamps for sterilization 

and on to the ship’s ballast system. Back-fl ushing water is returned over board at 

the ballasting site. During deballasting, the fi lter is bypassed and the ballast water 

receives a second dose of UV before being discharged overboard.

Manufacturer: PANASIA Co., Ltd., Republic of Korea

Link/Reference: www.worldpanasia.com

Approval Status: Type Approval, December 2009, Republic of Korea 

 Final Approval for Active Substances, March 2010
44 • ABS BALLAST WATER TREATMENT ADVISORY

APPENDIX

Resource Ballast Technology/Unitor BWTS

Methods: Mechanical cavitation + ozone + sodium hypochlorite injection + fi ltration

Operational Notes: The ballast water is treated on intake only. Cavitation and the application of the 

disinfectants electro-chlorination with sodium hypochlorite and ozone oxidation 

all take place. A screen-type self-cleaning fi lter is installed after the pump for the 

physical separation. The cavitation creates very strong sheer forces that effectively 

rupture the aquatic organisms. Electrodes mounted inside the reactor vessels 

produce sodium hypochlorite at a concentration of less than1.5 ppm. A small 

ozone generator incorporated in the control system provides ozone at less than 

1.5 ppm. The ozone provides disinfection both in brackish and fresh water. Both 

these disinfectants degrade rapidly without any effect on discharged ballast. The 

disinfectants employed are produced within the system and thus no additional 

facilities for the storage, make-up or dosing of chemicals are required.

Manufacturer: Resource Ballast Technologies (Pty.) Ltd., South Africa 

Link/Reference: www.resource-technology.com

Approval Status: Final Approval for Active Substances, March 2010
ABS BALLAST WATER TREATMENT ADVISORY • 45

APPENDIX

JFE BallastAce System

(using TG Ballastcleaner & TG Environmentalguard)

Methods: Filtration + chlorination + cavitation + residual control

Operational Notes: During ballasting, mechanical separation removes organisms larger than 35 

microns. Back-fl ushing water is returned over board at the ballasting site. Chemical 

dosing with sodium chlorine and sodium sulfi te preceeds a mechanical treatment 

with cavitation in multiple venturi tubes. A residual oxidizing agent is quenched by 

a reducing agent at discharge.

Manufacturer: JFE Engineering Corporation, Japan

(in cooperation with the Toagosei Group, Japan)

Link/Reference: www.jfe-eng.co.jp

Approval Status: Final Approval for Active Substances, March 2010

Type Approval, May 2010, Japan
46 • ABS BALLAST WATER TREATMENT ADVISORY

APPENDIX

HHI EcoBallast System

Methods: Filtration + ultraviolet light

Operational Notes: During ballasting, water is processed through the fi lter to remove any particles or 

organisms larger than 50 microns in size. The ballast then passes through the UV 

treatment unit utilizing high intensity, medium pressure UV lamps for sterilization 

and on to the ship’s ballast system. The UV lamps are arranged in a unique helix 

arrangement to maximize probability of exposure. Back-fl ushing water is returned 

over board at the ballasting site. During deballasting, the fi lter is bypassed and the 

ballast water receives a second dose of ultraviolet light before being discharged 

overboard. 

Manufacturer: Hyundai Heavy Industries, Republic of Korea

Link/Reference: www.hhi.co.kr

Approval Status: Final Approval for Active Substances, March 2010
ABS BALLAST WATER TREATMENT ADVISORY • 47

APPENDIX

RWO CleanBallast System

Methods: Filtration + electro-chemical oxidation

Operational Notes: A disk-type fi lter system is used for mechanical separation to 40 to 45 microns 

when taking in ballast water followed by the EctoSys® disinfection unit. This unit is 

an electro-chemical system utilizing electrodes with high oxygen over potential that 

produces powerful disinfectants such as hydroxyl radicals and also provides direct 

oxidation of microorganisms on the electrode surface. No chemicals or precursor 

substances are added to the ballast water. Neither the hydroxyl radicals nor any of 

the theoretically produced by-products are bio-accumulative or persistent. Ballast 

water can also be run through the disinfection unit at discharge.

Manufacturer: RWO GmbH, Marine Water Technology, Germany

Link/Reference: www.rwo.de

Approval Status: Final Approval for Active Substances, July 2009
48 • ABS BALLAST WATER TREATMENT ADVISORY

APPENDIX

Sedinox System

Methods: Filtration + electrolysis (chloride ion disinfectant)

Operational Notes: This is a two-stage treatment. The fi rst, the Sedimentor, is a hydrocyclone that 

removes sediment and biota during uptake. The second stage, the Termanox, is an 

electrolytic process based on the electrolysis of sodium chloride present in seawater. 

The Sedinox unit is the control system.

Manufacturer: Hamworthy, PLC, the Netherlands

 (formerly Greenship BV, the Netherlands)

Link/Reference: www.hamworthy.com

Approval Status: Final Approval for Active Substances, July 2009

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