Abstract
A previously developed scheme for speciation of metals in fresh waters was applied to the analysis of a sewage treatment final effluent and to the river upstream and downstream of the effluent outfall. In this treatment plant Cd levels were high in influent and effluent. Additional metals studied were Pb, Cu, Fe , and Mn. The scheme separates particles into six size fractions. Further analysis determines total non-filterable metal, total filterable metal, ASV-labile metal, Chelex-labile metal and ultraviolet irradiation-ASV-labile metal. In the final effluent, the largest fraction (> 12 micrometers) contained 20% of the Cd, 52% of the Pb, 32% of the Cu, 58% of the Fe, and 13% of the Man. The smallest fraction (< 0.015 micrometers) contained 45% of the Cd, 10% of the Pb, 47% of the Cu, 4% of the Fe, and 83% of the Mn. Intermediate-sized fractions each contained up to 24% of the total amount of each metal. Cd and Cu , but not Pb and Fe, appeared to be complexed with organic matter. Comparing similar analyses of the river upstream and downstream of the outfall showed changes in speciation. A large part of the Cd was added to the smallest size fraction. The major proportions of Pb, Cu, and Fe were added to the colloidal and particulate size fractions, minimizing immediate toxicity to aquatic life. Most of the Mn was present in the smallest fraction. (Cassar-FRC)