TOXICITY OF BALLAST-WATER TREATMENT EFFLUENT TO MARINE ORGANISMS AT PORT VALDEZ, ALASKA*

Abstract

ABSTRACT Approximately 12 million gallons of oily ballast water is taken ashore and treated daily at the Alyeska treatment plant, where tankers take on crude oil at the terminus of the Trans Alaska pipeline near Valdez, Alaska. Most oil is removed, but some light aromatic hydrocarbons (1 to 16 parts per million) remain in the large volume of discharged effluent. Between May and July, the concentration of aromatic hydrocarbons in the treated effluent (measured by gas chromatography) generally declined as the seasonal temperatures increased. We measured the toxicity of the effluent on site at Valdez. For the larvae of crustaceans and of fish the median lethal concentration LC50 was between 10 and 2p percent of treated effluent in 96-hour static tests. For salmon fry and shrimp in repeated acute flow-through assays, the (LC50) was quite consistent, between 20 and 40 percent of treated effluent. Because the concentration of aromatic hydrocarbons was much lower in the later tests but the toxicity of the effluent was not lower, toxicants other than aromatic hydrocarbons must contribute significantly to the toxicity of the effluent from the ballast-water treatment plant.