Module 9 : Ballast Water Treatment

Question 1

Ballast Use

Answer 1

To maintain a desired trim, depth, and list

Question 2

Ballast Water Management

Answer 2

1. Exchanged
2. Treated
3. Transferred to a shore facility
4. Retained on board

Question 3

Exceptions

Answer 3

1. The uptake or release of water is necessary for the purpose of ensuring vessel safety in an emergency situation or saving life at sea
2. Necessary to avoid or minimize the discharge of a pollutant from the vessel
3. The release results from an accident of navigation as long as it wasn’t due to poor seamanship

Question 4

Ballast Water Exchange

Answer 4

95% of volume, 200 NM from shore, 200 m minimum depth
1. Sequential (empty and then refill) 95% volumetric exchange
2. Flow-through (overflow) 3x tank volume
3. Dilution (filling and discharge simultaneously) 3x tank volume

Question 5

Ballast Water Treatment

Answer 5

1. Mechanical (filters)
2. Physical (UV, heat)
3. Chemical
4. Any combination

Question 6

Mechanical Ballast Water Treatment

Answer 6

Separate out larger marine organisms and improve efficiency of secondary treatment.
Filtration: about 91% effective, very ecologically acceptable
Cyclonic: vortex that drives organisms in one direction and clean water in the other. No moving parts, nothing that will get clogged. Less effective

Question 7

Physical Ballast Water Treatment

Answer 7

Ultrasound: generate cavitation bubbles, when the bubbles reach their max volume, they collapse causing cavitation. This results is localized high temperatures and pressures. Hydrodynamic shear forces kill organisms. Non-chemical, environmentally-friendly, little maintenance. Robust and easy to operate.
Ultraviolet: act on the DNA of the organisms to make them harmless and prevent reproduction.
Heat Treatment: reach a temperature where the organisms are killed. Can take a long time and can increase corrosion in the tanks

Question 8

Chemical Water Ballast Treatment

Answer 8

Use biocides to remove invasive organisms, but must be degradable or removable before discharge.
Oxidizing biocides are general disinfectatnts, acting by destroying the organic structures like cell membrane and nucleic acids.
Non-oxidizing biocides act on the reproductive, neural or metabolic functions of the organism.

Question 9

Ballast Treatment Systems

Answer 9

Usually a combination of 2-3 methods, like physical first and chemical second. Choice of system depends on type of ship, space, cost