LYSIMETER WASHING OF MSW INCINERATOR BOTTOM ASH

Stockpiled municipal waste incinerator bottom ash is frequently consid ered for utilization as a construction material. Two 360 kg lysimeter experiments were conducted to study percolation washing of contaminant s from stockpiled MSW bottom ash. One lysimeter was leached with a con centrated sodium hydroxide solution, as a possible pre-treatment for i mprovement of the bottom ash characteristics prior to utilization, whi le the other was leached using distilled water. The lysimeter leachate was analysed, and at the end of the 2-year leaching period, the botto m ash from each lysimeter was subjected to several laboratory tests to assess the effect of the treatments. The laboratory tests showed that distilled water leachability of both treated ashes was an order of ma gnitude lower than that of fresh ash, but long-term contaminant leacha bility under acidic conditions had not changed. Although alkaline wash ing clearly resulted in greater contaminant removal than did distilled water washing, the chemical properties of the alkaline-leached bottom ash were not significantly different from those of the water-leached ash.