AWWA JAW56621

Analytical methods were developed to accurately determine the levels of the most prevalenttrace metal contaminants in a variety of alum feedstocks used in the coagulation process ofdrinking water treatment. A combination of chelation ion chromatography, chelationextraction-atomic absorption spectrometry, and hydride generation atomic fluorescenceallowed for the selective isolation of trace metals from the alum matrix with a high degree ofprecision and sensitivity. Trace levels of arsenic, cadmium, chromium, copper, manganese,nickel, lead, and zinc were found in the range of 20-330 ug/g aluminum (Al); iron, recognizedas a co-contaminant in the raw material, was present at 20 mg/g Al. By extrapolating thesemeasured levels to an upper yet realistic applied dosage of alum in drinking water treatment,the authors could predict the contaminants' concentrations (under a worst-case scenario) inboth the finished water and alum sludge. For finished water even if it was assumed that noneof the trace metals was removed during coagulation, the contaminants' concentrations didnot exceed drinking water standards, and their contribution reached only a small fraction ofthe permitted maximum contaminant level. In a scenario in which the trace metals wereassumed to be removed during the coagulation process, levels that would accumulate in thealum sludge would not be significant enough to heavily influence decisions to apply alumsludge to land for agricultural uses. Includes 24 references, tables, figures.

Product Details

Edition:

Vol. 94 - No. 5

Published:

05/01/2002

Number of Pages:

12

File Size:

1 file , 800 KB