Prince William Sound Regional Citizens' Advisory Council Updated: 1/29/05 

NIS Treatment Options for 

Ballast Water

Tanker-Based Shore-Based

load clean 

ballast

ballast water 

treatment

facility*

Ballast Water 

Management

• Sequential 

ballast water 

exchange

• Flow through 

ballast water 

exchange

• Intake 

minimization 

Physical 

Separation

• Filtration

• Hydro-cyclones

Secondary Treatment

• Ultra violet

• Thermal

• Ultrasound

• Magnetic

• Electrical

Mechanical Chemical

• Biocides

• Chlorine

• Ozone

• Hydrogen 

peroxide

• Chlorine dioxide

• Glutaraldehyde

• Other *physical, mechanical, and chemical, or 

a combination of methods may be used 

Adapted from Hurley, Mackey, et.al., 2001

Under 

Development

BALLAST WATER TREATMENT METHODS 

Fact Sheet 1 Overview

 Prince William Sound, Alaska Crude Oil Tankers

Prince William Sound Regional Citizens’ Advisory Council (PWSRCAC) is specifically interested in examining 

and identifying ballast water treatment technologies that may be successfully used to control nonindigenous species 

(NIS) introduction into Prince William Sound (PWS), Alaska via crude oil tanker ballast water. 

Ballast water treatment methods are typically categorized as either tanker-based or shore-based treatment 

technologies. Treatment options can include ballast water management operational procedures, physical separation, 

or secondary treatment. There are also a number of new technologies emerging that are identified as “under 

development.” As illustrated below, NIS can be managed by a variety of available technologies. 

When selecting an appropriate ballast water treatment technology, one of the first steps in the evaluation process is 

to determine the targeted alien invader. You must know which NIS you are concerned about and what potential 

methods would be best suited to treat the NIS of concern, since certain technologies are better suited than others for 

treating particular NIS. For example, larger NIS typically require a filtration system to limit the amount of NIS 

initially taken into the ship’s tanks; however, microscopic NIS typically require additional chemical, physical or 

heat treatment to kill organisms that bypass the filtration system. In selecting a technology for Prince William 

Sound, Alaska, a focused alien invader target, or range of targets must be identified. PWSRCAC’s current research 

shows that NIS range in size from large NIS such as crabs to microscopic NIS (see the PWSRCAC NIS Species 

Fact Sheets for more information). It is expected that a combination of technologies may be required to address this 

wide range NIS for PWS Alaska. 

As shown in the figure above, there are both tanker-based and shore-based treatment options available. While much 

of the Prince William Sound Alaska tanker company efforts have been focused on tanker-based treatment options, 

cost effective shore-based treatment options may also be an alterative. The Prince William Sound, Alaska tanker 
Prince William Sound Regional Citizens' Advisory Council Updated: 1/29/05 

trade route is unique; it is a dedicated and predictable trade route. Dedicated PWS tankers load oil in Port Valdez 

and transport it to various refineries on the West Coast of the United States. Those same tankers return to Port 

Valdez with ballast water. The ballast water is offloaded in Port Valdez and oil is again loaded on the tanker. The 

Valdez Marine Terminal in Port Valdez is already equipped with a Ballast Water Treatment Facility to treat oily 

un-segregated ballast water. Expansion and modification of the Ballast Water Treatment Facility to also treat 

segregated ballast for NIS may be a logical economy of scale for this particular trade route and warrants further 

evaluation. Shore-based treatment technology options are much more mature and readily available, which may 

make this a more cost effective and quicker option for consideration. 

Tanker-based treatment options are full of technical and economic challenges; however, they may be the only 

option in unpredictable, widely varying trade routes that don’t lend themselves to shore-based treatment options. 

Technical challenges for tanker-based treatment options include: vessel safety, fire hazards, corrosion, space 

limitations, vessel design limitations, inability to treat full volume during transit route, and “dead-spots” in tanks 

that remain untreated. While tanker-based ozone treatment has been studied as an option for Prince William Sound, 

research shows that ozone can be effective for disinfection of some organisms in ballast water, but may have a 

reduced effect on some mollusks and crustacean larvae and dinoflagellate cysts in the sediment. 

The International Maritime Organization (IMO)1

 has found that treatment technologies should be: (1) safe; (2) 

environmentally acceptable; (3) practicable; (4) cost effective; and (5) biologically effective. Very few technologies 

at this current stage meet all five criteria. One of the most significant problems in evaluating technology options is 

the lack of technology standards. Researchers and entrepreneurs continually point out the need to develop and 

implement international standards and procedures for the evaluation and approval of new ballast water treatment 

systems. 

In summary, most ballast water treatment technologies are still under development. Ballast water exchange remains 

the primary method in use worldwide. So far, the most effective and promising technologies involve a combination 

of technologies using primary treatment options (filtration or cyclonic separation) followed by an additional 

chemical or mechanical treatment. 

Periodic searches of recently-published research will be conducted by PWSRCAC to keep abreast of current 

literature for new and emerging technologies. As national and international pressure to solve the NIS invasions 

problem continues, universities, government agencies and private companies are racing to develop commercially 

viable technologies to treat NIS in ballast water. The quality and quantity of technology treatment options will 

continue to expand and should be watched closely over the next couple of years, while the search for a viable 

treatment technology for the PWS Tanker trade continues. 

Prince William Sound Regional Citizens’ Advisory Council (PWSRCAC) 

Welcomes Your Input 

PWSRCAC is a non-profit citizens’ council that is actively examining and identifying ballast water treatment 

technologies that may be successfully used to control NIS introduction into Prince William Sound (PWS), Alaska 

via crude oil tanker ballast water. 

If you have information on ballast water treatment technologies that may be successful in PWS, Alaska crude oil 

tanker trade, please send this information to the PWSRCAC NIS Project Manager, Lisa Ka’aihue at 

kaaihue@pwsrcac.org or contact us at 1-800-478-7221. 

 

1

 www.imo.org