Field and Mesocosm Assays of Oil Spill Bioremediation

EU Program: MARINE POLLUTION
Coordinator: Regas Santas
Contract #: PM/XI.C.4/9517, DG-XI
Status: Completed
Year: 1996
Duration: 24 months
EU contact person: A. Barisich, DG-XI
Partners: ELF Aquitaine, Paris; Institut Oceanographique Paul Ricard, Ile des Embiez; CEREMHER (Centre de Recherche Meze Herault), Meze; Battelle Ingenieurtechnik, Frankfurt.

Project objectives

This project aimed at:

1. assessing the biodegradation rate of different oil types under different weather conditions,
2. evaluating the risk of eutrophication from excessive fertiliser application during bioremediation attempts,
3. assessing the bioremediation effectiveness of representative oleophilic and water soluble fertilisers, and
4. comparing biodegradation rates effected by native and introduced decomposer populations.

Brief project description

A polluted site including sandy and rocky areas were selected in Saronicos Gulf near the PETROLA oil refineries. (A major oil spill accident occurred in this location in November 1994). Sediment samples were subjected to quantitative hydrocarbon analysis. The following treatments were established in beach sediments enclosed in crates:

1. two fertiliser types (Inipol A-22, oleophilic; standard water soluble)
2. two fertiliser levels (low, high fertiliser dose - established in baseline measurements)
3. two decomposer groups (native and bacteria strains).

Hydrocarbon degradation was monitored for three months following treatment application. The procedure was repeated three more times, during different seasons of the year. The experiments were repeated in mesocosms simulating a sloping intertidal zone. The tanks housing the mesocosms were built from inert, non-metal materials to prevent toxicity from heavy metal cation release. Water was recirculated in each tank using a non-destructive peristaltic pump for plankton preservation. All mesocosms were operated outdoors, under natural temperature and light fluctuations. Wave action was simulated using automated wave generators, capable of adjusting wave frequency and height. Substrate, water and living organisms from wild unpolluted ecosystems were transferred into the tanks as a natural inoculum for mesocosm development. After reaching steady state, the communities were exposed to a mixture of the most commonly used crude oil types. The oil slicks were subjected to the same fertiliser/decomposer treatment combinations as in the field.

Parameters monitored included:

• Hydrocarbon degradation
• Overall mesocosm health status (indicator organism survival, community composition, species diversity, stress symptoms)
• Eutrophication status (nutrient concentrations, dissolved oxygen, BOD, COD, primary productivity).

The above parameters were monitored weekly at 3 points: the sediment-water interface, the open water, and the shore. The experiments were repeated for a total of 4 times, each time covering the length of a season for a comprehensive evaluation of the bioremediation techniques employed. Based on the experience gained from the project, the partners can work out an emergency action plan and organise a task force to confront oil spill accidents.