| Contents Notes |
"Various chemical liners were evaluated for use in a segregated monolandfill for the disposal of electroplating wastewater sludges. The tests were conducted in an unused portion of a secure landfill in South Carolina. Seven cells were constructed, each 2.4 m (8 ft) square and 1.8 m (6 ft) deep. One cell was reserved as a control, and the other six were used as replicate test cells. Agricultural limestone, hydrous oxides of iron, and fly ash were each used to line two test cells. The control cell was lined with sand. All seven cells were then filled with sludges from the treatment of electroplating wastewaters. Leachate was collected under a CO2 environment from below the cells approximately once a month for 21/2 years and analyzed to evaluate the capacity of the liners to retain heavy metals leached from the sludges. After the last leachate samples were collected in August 1982, each cell was core-sampled to assess the vertical distribution of selected metals in the sludge, the liner and the soils. The concentrations of metals and soluble salts in the leachate varied widely during the first 12 to 15 months then leveled off. The leachate concentrations of the various metals did not appear to be related to levels found in the sludges. The volume of leachate collected indicated the permeabilities of the liners and did not correlate with rainfall. The limestone and hydrous-oxides-of-iron appeared to retain more metals than did fly ash, but no significant metal leaching was observed in any of the test cells. The excavated sludges showed characteristics similar to the raw sludges originally deposited. Because only small amounts of metals were leached from the sludges, the overall relative performance of the liners cannot be judged from this study. Hydrous oxides of iron (derived from ferric sulfate) would probably be prohibitively expensive for this application, however. More studies will be needed before chemical liners can be applied to the full-scale landfilling of metal-finishing sludges." |
