Metal Concentrations in Sludges from Treatment Lagoons

Metal

Copper

Wet sludge (mg/L) Dry solids (mg/kg) Iron

Wet sludge (mg/L) Dry solids (mg/kg) Lead

Wet sludge (mg/L) Dry solids (mg/kg) Mercury

Wet sludge (mg/L) Dry solids (mg/kg) Zinc

Facultative Lagoonsa

8.9 144

54.6 840

Partial-Mix Aerated Lagoonsb

10.1 809.2

21.1

85.2 2729

a Average of values from two facultative lagoons in Utah. b Average of values from two partial-mix aerated lagoons in Alaska.

Source: Schneiter, R.W. and Middlebrooks, E.J., Cold Region Wastewater Lagoon Sludge: Accumulation, Characterization, and Digestion, Contract Report DACA89-79-C0011, U.S. Cold Regions Research and Engineering Laboratory, Hanover, NH, 1981.

If metal removal is a process requirement and the local climate is close to subtropical, the use of water hyacinths in shallow ponds may be considered. Tests with full-scale systems in both Louisiana and Florida (Kamber, 1982) have documented excellent removal, with uptake by the plant itself being a major factor. The plant tissue concentrations may range from hundreds to thousands of times that of the water or sediment concentrations, indicating that bioaccumulation of trace elements by the plant occurs. Metal removals in a pilot hyacinth system in central Florida are presented in Table 3.15. Hyacinths have also been shown to be particularly effective in extracting metals from photoprocessing wastewater at a system in Louisiana (Kamber, 1982)

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