A 1994 oil well eruption in northern Italy resulted in the release of crude oil to the agricultural area of Trecate, Italy. From the beginning, Battelle has worked with the oil well owner, Agip, to remediate the 15-square kilometers of contaminated fields. Six years later, most of the impacted area has been returned to farming use. Two parcels remained to be treated: the farmland just south of the well and the well site itself.

The most heavily polluted fields presented a unique opportunity for phytoremediation, a process of removing contaminants through crop cultivation. Contaminated soils were removed and treated in biopiles. The treated soils, with residual contamination levels too high to allow traditional use, were returned to the fields and planted with a variety of crops natural to the affected area. The studies lasted two years and included cultures of maize, sorghum, soya, clover, rye grass, fescue and alfalfa in the summer seasons and colza, fescue, rye grass, triticale and vetch in the winter seasons.

Periodically, soils and plants from these plots were analyzed for residual hydrocarbons. The results show that hydrocarbon degradation under phytoremediation had a slow start, with some plants exhibiting poor growth initially. In subsequent seasons, however, hydrocarbon degradation was significant under most conditions. Distinctly better results were exhibited by maize, sorghum, and triticale, while plots with clover and alfalfa improved quite slowly. After two years, the residual contaminant levels have dropped below 1000 parts per million and continue to fall. This remediation project demonstrated the beneficial effects and success of this approach in improving natural biodegradation.

At the well site, soil contamination existed to at least 3 meters below the surface. For speedy remediation of the site as industrial land, it was decided to excavate and to wash and thermally treat the soil, then return it to the site as clean landfill. The treatment is more expensive than biodegradation technologies but more economically and environmentally sound than removal of soil to a dumpsite. This work was performed by contractors from Italy and Belgium and accompanied by monitoring of contamination levels by Battelle.

During the spring 2000 farming season, egrets, storks and grey herons were visible to Battelle’s onsite analytical staff, providing reassurance to the success of the remediation. The final step will be the presentation of detailed pollutant monitoring and residue analyses to Agip, insurers and Italian authorities.

For more information, contact Klaus Mueller, 41-22-827-2302, muellerk@battelle.org.