Prince William Sound Regional Citizens’ Advisory Council ~ Citizens promoting environmentally safe operation of the Alyeska terminal and associated tankers.

VALDEZ: PO Box 3089 / 130 S. Meals, Ste. 202, Valdez AK 99686 ~ toll-free: 877.478.7221 ph: 907.834.5000 fax: 907.835.5926 

ANCHORAGE: 3709 Spenard Rd., Ste. 100, Anchorage, AK 99503 ~ toll-free: 800.478.7221 ph: 907.277.7222 fax: 907.277.4523

www.pwsrcac.org ~ see other PWSRCAC fact sheets at www.pwsrcac.org/resources/factsheet.html

Ballast Water Treatment Facility FACT SHEET

February 2007

Overview

The Ballast Water Treatment Facility at the Valdez tanker terminal processes “dirty” ballast—seawater stored 

in the cargo tanks of empty oil tankers for stability on the open ocean. When tankers arrive in Valdez to load 

oil, they must first offload oily ballast water. At the ballast water facility, the oil and water are separated. The 

recovered oil is put back into the system and loaded onto tankers as cargo, while the treated water is discharged 

into Port Valdez. Treatment is a three-stage process.

see also:

www.pwsrcac.org/projects/TermOps/bwtf.html

www.pwsrcac.org/projects/TermOps/airqual.html

www.pwsrcac.org/newsroom/bwtfads.html

Air Pollution

Air emissions from the ballast water treatment facility are currently 

unregulated, yet they greatly exceed 

the threshold at which the Environmental Protection Agency deems a 

facility a major source of hazardous 

air emissions. The council continues 

to monitor this issue and to vigorously support reduction of hazardous air emissions from the facility.

Stage 1: GRAVITY SEPARATION. Oily ballast water and other 

facility waste water is pumped into 

large gravity separation tanks (also 

called 90s tanks) where the oil floats to 

the surface. That oil is then skimmed 

off, stored in recovered crude oil tanks 

(also called 80s tanks) and eventually 

loaded onto tankers as cargo.

Gravity separation tanks.

Stage 2: DISSOLVED AIR FLOTATION. Next, waste water is routed 

into dissolved air flotation (DAF) cells 

for further removal of hydrocarbons. 

Air and polymers are introduced and 

dissolved into the waste water under 

pressure as it is piped to the DAF cells. 

Release of the pressure as the water enters the DAF cells causes the formation 

of very tiny bubbles that accelerate the 

process of separating the remaining oil 

droplets from the water. The polymer 

binds the oil together, while tiny air 

bubbles float the polymerized oil to the 

surface. Oil recovered at this stage is 

also reloaded as cargo.

Dissolved air flotation cells.

Stage 3: BIOLOGICAL TREATMENT. Waste water from the DAF cells 

is sent to biological treatment tanks for 

the final stage of hydrocarbon removal. 

Oil-consuming microbes and volatilization to atmosphere removes additional 

hydrocarbons including certain aromatic hydrocarbons known as BTEX 

(benzene, toluene, ethylbenzene, and 

xylene). Benzene is a known human 

carcinogen. The hydrocarbon content 

of the treated water discharged into 

Port Valdez is strictly regulated by a 

federal permit.

Biological treatment tank.

Alyeska Pipeline Service Co. is in the process of substantially upgrading 

and redesigning this facility to reduce air and water pollution.