The Petroleum harbour project is the third pilot remediation, which was carried out within the framework of POSW (the national development programme for treatment processes of polluted sediments). The main objectives of the pilot remediation are:
– to demonstrate the biological treatment of dredged materials on a practical scale;
– to gain knowledge and experience for the future remediation of the total Petroleum harbour.
A strict tender procedure was carefully executed in order to select the most effective and ‘state of the art’ biodegradation technology. The selected remediation chain was a combination of ‘standard’ soil treatment technology and newly developed biotechnology. The contaminated sediments were separated by hydrocyclones, then the sand fraction was cleaned by froth flotation, and the fines were treated in a continuous flow reactor consisting of a cascade of 4 bioreactor tanks. A belt press was used for dewatering the fines. Dredging, biotechnological treatment and the effects of the remediation on the environment were monitored in detail. The quality of the treated sand fraction complied with the Dutch standards for re- use and was actually applied in a project of Rijkswaterstaat. Biodegradation resulted in a substantial decrease of the oil and PAH's contents, but due to the lack of breakdown of a few high-molecular PAH's, the quality requirements of the contract were not achieved. For less heavily polluted sediments and soils the applied biotechnology may be more effective. The results of the project show that biodegradation in bioreactors on a large scale is feasible. Furthermore useful information was gathered for the future remediation of the Petroleum harbour. It is concluded that the two main objectives of the project have been attained. Finally some recommendations for the future clean-up of the Petroleum harbour are given.