Characterization of Confined Disposal Area Influent and Effluent Particulate and Petroleum Fractions.

摘要

A detailed analysis of contaminants in influents and effluents from two confined dredged material disposal areas is presented. The sites are located at Pinto Island, Mobile Bay, Alabama, and Grassy Island, Detroit, Michigan. The samples were separated into 0.05-micrometers, 0.45-micrometers, and 8.0-micrometers fractions. The total sample and filtrate were analyzed for metals, nutrients, total carbon, organic carbon, chlorinated hydrocarbons, oil and grease, sulfide, and solids content. The total solids were subjected to a geochemical partitioning scheme to determine changes of metal solid phases during confined area disposal. The oil and grease fractions in the samples were analyzed for trace metals. A 48-hour settling test was performed to quantify the migration of soil and grease and chlorinated hydrocarbons during resedimentation of dredged material within a confined area. A statistical analysis of the data was performed to determine the significance of variance in terms of pollutant loading between influent and background water; influent and effluent in terms of removal efficiency; and effluent and background water in terms of potential water quality impact. Tests for significance at the 95 and 99 percent confidence levels are presented. The results show that, in general, the removal efficiency of total trace metals was very similar to the total solids removal. These results are in agreement with the analytical data which show that approximately 99% of the total trace metals was associated with the solid settleable phase (> 8-micrometers).