Volatilization of Toxic Organic Compounds During In-Vessel Composting of Hazardous Waste

Abstract

ABSTRACT

The fates of aromatic hydrocarbons in an American Petroleum Institute separator sludge (Hazardous Waste K051) undergoing in-vessel composting were investigated. Amounts of each compound that were volatilized, degraded, and residual were determined. Volatilization of alkylated benzenes was rapid and increased proportionately with increasing chemical concentration (up to 10-15% of the original mass). Above a critical concentration, cumulative volatilized compound increased to >50% of the original mass. Dimethylnaphthalene volatilized at a slower rate over a longer time period. In experiments with less than the critical concentration, <10% dimethylnaphthalene was volatilized. In experiments with high original concentrations, >30% was volatilized. The 3-4-ring aromatics were not detected in the exiting air stream.

At low loading rates (5%) and low spiked chemical concentrations (200-400 mg/kg waste), final residual concentrations of all analyzed hydrocarbons were reduced to <10% of the original concentration. Most volatile chemical half-lives averaged <5 days. Degradation was slower and incomplete at high loading rates (10%) and high spiked chemical concentrations (400-800 mg/kg waste).

Although all treatments effectively depleted most of the chemicals from the finished compost, their fate was not the same. Volatilization was the dominant loss mechanism for the alkylated benzenes for treatments with the highest chemical concentrations. The volatilized chemicals remain a source of air pollution.