Risk assessment of PAHs in solid residues from supercritical water gasification of sewage sludge

In this study, the contents of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge (SS) and solid residue (SR) from supercritical water gasification of SS were analyzed and the pollution degree and human health risk with PAHs in SS and SR samples were determined. SR samples were collected from different reaction condition, according to different reaction temperature, time and water content. The results show that the contents of PAHs in SR samples were increased after gasification reaction, ranging from 1541 to 8234.8 mu g/kg, and that the PAHs with 4-6 rings are major pollutants in the SR samples. Based on Nemero Index P, the classification evaluation shows that the SR samples almost exceed the light polluted. While, the health risk assessment according to Benzo[a]pyrene total potency equivalents present that the health risks from PAHs are acceptable for children and adults using the SR sample for agricultural land.