Vermiremediation of polycyclic aromatic hydrocarbons and heavy metals in sewage sludge composting process

•Vermicomposting of different sewage sludge exhibiting various contamination levels.•Eisenia andrei employed in the process of decomposition of organic matter.•Removal of total heavy metals and polycyclic aromatic compounds.•Heavy metals and PAHs accumulation in earthworms' bodies.

The main objective of this work was to study the dynamics of the degradation of polycyclic aromatic hydrocarbons (PAHs) during sewage sludge vermicomposting. This eco-biotechnology employing earthworms as natural bioreactors for decomposing of organic matter may be used for vermiremediation of particular pollutants present in various organic matter sources. In this experiment, sewage sludge was mixed with bulking agents and precomposted. Afterward, adult Eisenia andrei specimens were introduced into the process. Total heavy metal and PAHs concentration were measured in composts and earthworms before and after the process. While heavy metal concentrations fluctuated mildly in the substratum, several metals clearly accumulated in the earthworms' bodies. Body Accumulation Factors could be ranked as follows (Cd > Cu > Zn > Ni > Cr > Pb). Interestingly, addition of earthworms into the process has led to the high percentage of PAHs removal and some of the 16 priority PAHs analyzed in this study have been accumulated in earthworms' bodies. Applied conditions did not affect worms' viability but they almost completely inhibited their reproduction.