JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH Part A—Toxic/Hazardous Substances & Environmental Engineering Vol. A39, No. 1, pp. 1–17, 2004 Solid Phase Treatment of an Aged Soil Contaminated by Polycyclic Aromatic Hydrocarbons Marco Negri, 1 Andrea Manfredini, 2 Sabrina Saponaro, 1 Claudia Sorlini, 2 Luca Bonomo, 1 Anna Valle, 2 and Elisabetta Zanardini 2, * 1 Dipartimento Ingegneria Idraulica, Ambientale, Infrastrutture Viarie, Rilevamento, Sez. Ambientale, Politecnico di Milano, Milan, Italy 2 Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Sez. Microbiologia Agraria Alimentare ed Ecologica, Universita` degli Studi di Milano, Milan, Italy ABSTRACT Laboratory scale tests were carried out in order to evaluate the removal efficiency of polyaromatic hydrocarbons (PAHs) during the different biological treatments of a Manufacturing Gas Plant site aged soil, heavily contaminated by high molecular weight compounds. Biodegradation studies were carried out at nearly 25  C in solid phase reactors. Three tests were performed, over a period of 100 days for each test. In the first test (P1-bioaugmentated), soil was mixed with wood chips and urea at the start of the treatment and after six weeks from the beginning of the test was also periodically inoculated (at 42, 54, 69, 82, and 96 days) with selected consortia of autochthonous PAH-degrading bacteria. The second test (P2-biostimulated) was performed similarly to the previous one, but without any inoculations. In the third test (P3-control) only soil was introduced. All systems were aerated daily and humidified at the occurrence. PAH concentra- tion, total cultivable heterotrophs, PAH-degrading bacteria, mycetes, pH, ATP *Correspondence: Elisabetta Zanardini, Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Sez. Microbiologia Agraria Alimentare ed Ecologica, Universita` degli Studi di Milano via Celoria 2-20133 Milan, Italy; E-mail: elisabetta.zanardini@unimi.it. 1 DOI: 10.1081/ESE-120027365 1093-4529 (Print); 1532-4117 (Online) Copyright & 2004 by Marcel Dekker, Inc. www.dekker.com