[Fate of polycyclic aromatic hydrocarbons by composting of municipal sewage sludge and rapeseed meal].

The goal of these studies was to determine the fate of 16 polycyclic aromatic hydrocarbons (PAHs) during the 94 days of composting of municipal sewage sludge with rapeseed meal. The total PAHs calculated from the sum of the amounts of the 16 PAHs in the initial mixture of municipal sewage sludge was about 1.792 mg x kg(-1). Then the content of total 16 PAHs was 0.153 mg x kg(-1) at the final of composting. The level of total PAHs fell by about 91.5% (p < 0.05) at the end of composting. While the content of humic substance increased, the content of PAHs decreased in the intermediate stages (31-61 days) of composting. The treatment by composting led to a decrease of all PAHs mainly in 16-31 d, but some differences could be observed between PAHs with three or fewer aromatic rings (N=3) and those with four or more (N=4). The PAHs with N of three or fewer (except phenanthrene) exhibited a continuous decrease, which the PAHs with N of four or more and phenanthrene showed increases between the 31-46 days. This indicates the high potential sorption mainly of PAHs with high molecular weight (N=4) plus phenanthrene, their tight adsorption makes them inaccessible for biodegradation. The high molecular weight PAHs showed a greater reduction of their bioavailability than low molecular weight (except benzo[b]fluoranthene).