Toxicity evaluation of produced formation waters after filtration treatment

During the last years many authors have characterized the produced formation waters (PFWs) with respect to chemical compounds and toxicity. Most of data are related to PFWs collected on offshore platform after treatment process. The available results showed that the particulate phase had an influence on PFW toxicity. Assuming the toxicity of PFWs treated on platform, the aim of this paper is to study the toxicity of these PFWs after a further filtration treatment carried out in laboratory. For this purpose PFWs were sampled from three natural gas platforms located in the Adriatic Sea (Italy) below treatment system. The eco-toxicological bioassays have been conducted on test-organisms belonging to different trophic levels such as bacteria, algae, crustaceans and fishes. The PFWs resulted toxic according to an overall assessment obtained through the bioassays. Furthermore, it has been possible to identify the species that were more sensitive to the tested PFWs, namely Tigriopus fulvus, Dicentrarchus labrax and Vibrio fischeri. Besides, a chemical characterization was reported related to the contaminants present in the PFWs to go with eco-toxicological assessment. Barium, zinc and manganese showed the most concentrations among the metals and the lower molecular weight components were common among the organic compounds. Some differences among PFWs were observed both for toxicity and chemical composition. The highest toxicity was recorded in PFWs (PFW1 and PFW2) containing the highest concentrations of some metals (Ba, Mn and Zn) and/or BTEX.