The effect of processing on the heavy metal content in compost

Abstract

Mixed collected, mechanically separated domestic waste was composted, applying four different techniques. For each technique applied, the process was monitored in time and the influence of the total time of composting on the heavy metal concentration in the final product was studied.

Waste was composted in a “simulator” (total time of composting (Te) 19 days), on a compost pile with small dimensions and forced aeration (Te=41 days), on a compost pile with small dimensions which was aerated by a turning every 14 days (Te=70 days), and on a compost pile which was aerated by only two intermediate turnings (Te=166 days). For each experiment particle sizes, and heavy metal contents, dry weight, organic content, total organic carbon, and pH, in the total composting material (0–70 mm) and in the small fraction (0–6 mm), were monitored in time.

The particle size analysis showed that the efficiency of the composting (percentage 0–6 nm of the final product), was not influenced by the total time of composting.

The observed heavy metal concentrations indicated a relationship between the total time of composting and the heavy metal concentration of the final product.

Shorter times of composting tend to result in lower Cu, Pb, and Zn concentrations in the mature compost.