Treatment of Oily Wastewaters from Onshore Operations

A study of the effectiveness of large-scale treatment of ballast water was conducted at the terminal facility of the Trans-Alaska Pipeline in Port Valdez. The treatment plant performance evaluation was conducted during three separate periods: Summer 1978, Winter 1979, and Summer 1979. It was found that the plant is generally effective in reducing the petroleum content of the ballast water. On the average, the oil content of incoming ballast water (ranging between 7 000 and 10 000 mg/l is reduced to an organic load equal to 10 mg C/l in the final effluent. The bulk of the organic content reduction takes place in the gravity separator, where approximately 99.8% petroleum is removed. Typically, the final treated effluent contains 45 to 50% volatile aromatic hydrocarbons and 35 to 40% dissolved nonvolatile organics. The remaining 10 to 20% suspended organic matter, which is composed of aliphatic hydrocarbons and other water-insoluble fractions of petroleum, may properly be defined as "the oil." Based on plant discharge records and experimental data generated by this study, the estimated average daily discharge of aromatic hydrocarbons is 265 l (70 gal).