Changes of solid phase toxicity during sewage sludge composting in relation to bioavailability of polycyclic aromatic hydrocarbons.

The aim of the present study was to determine the content of the bioaccessible fraction of polycyclic aromatic hydrocarbons (PAHs) in sewage sludges and composts by means of three techniques (solid phase extraction with Tenax-TA and non-exhaustive extraction with hydroxypropyl[beta]cyclodextrin and n-butanol) and at the same time to establish their influence on toxicity for Heterocypris incongruens (Ostracodtoxkit test) and Lepidium sativum (Phytotoxkit test). In the majority of cases sewage sludges negatively influenced on organisms. Generally, sewage sludge composting exerted a positive influence on phytotoxicity, whereas in the case of ecotoxicity a negative effect was noted. The content of the potentially bioaccessible PAHs fraction varied depending on the method applied. Composting usually lowered the content of the potentially bioaccessible fraction. Significant positive relationships were observed mainly between Tenax-TA extracted fraction of individual PAHs and growth inhibition of H. incongruens. Only negative correlations were noted in the case of phytotoxicity.