EFFECTIVENESS OF A LARGE-SCALE BALLAST TREATMENT PROCESS

Abstract

ABSTRACT A study dealing with the effectiveness of large-scale treatment of ballast water was conducted at the terminal treatment facility of the Alaska Pipeline in Port Valdez, Alaska. Three principal questions addressed by the study were: the effectiveness of petroleum removal from ballast water; the nature of the chemical changes in the process stream; and the suitability of various analytical techniques for monitoring plant operation and measuring the quality of the final effluent. The following analytical operations were performed on-site in Port Valdez: determination of “total oil” by Freon 113 extraction, followed by IR and gravimetric measurement methods; determination of nonvolatile dissolved and nonvolatile suspended organic materials by TOC analysis; determination of volatile organics by gas chromatography; and accumulator column separation and chloroform extraction of dissolved nonvolatile organic matter for subsequent HPLC and GC/MS analysis. It was found that the final effluent contained volatile organic matter composed primarily of aromatic hydrocarbons (benzene, toluene, and xylenes) (48 percent), dissolved organic materials of petroleum nonhydrocarbon type (36 percent), and suspended organic matter which is traditionally defined as water-insoluble “oil” (16 percent). The bulk of the separation of oil from water, it was found, takes place in primary gravity separators (more than 99 percent), and that the secondary aeration-flocculation operation removes only approximately one-half of the remaining fraction of one percent. The studies also showed that standard methods for determination of “total oil” by extraction and either IR or gravimetric methods are insufficient for monitoring the quality of the final treated effluent. This is because the principal organic components in treated effluent are volatile aromatic hydrocarbons and dissolved petroleum non-hydrocarbons. The standard method for “total oil” analysis by extraction-IR is not calibrated for detection of such components, while evaporation of solvent during the gravimetric procedure results in the loss of the largest single group of organics present in the effluent: aromatic hydrocarbons.