LYSIMETER WASHING OF MSW INCINERATOR BOTTOM

Stockpiled municipal waste incinerator bottom ash is frequently considered for utilization as a construction material. Two 360 kg lysimeter experiments were con-ducted to study percolation washing of contaminants from stockpiled MSW bottom ash. One lysimeter was leached with a concentrated sodium hydroxide solution, as a possible pre-treatment for improvement of the bottom ash characteristics prior to utilization, while the other was leached using distilled water. The lysimeter leachate was analysed, and at the end of the 2-year leaching period, the bottom 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 magnitude lower than that of fresh ash, but long-term contaminant leachability under acidic conditions had not changed. Although alkaline washing 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. Key Words—Municipal solid waste, incinerator bottom ash, lysimeter, column, alkaline washing, leaching, metals, chlorides, sulphate. 1