Abstract

Oil-produced waters are the most abundant wastewater stream in oil exploration and production, and their treatment is one of the most expensive processes in the petroleum industry. Since one of the peculiar characteristics of oil-produced waters is the presence of high salinity, developing an effective phytoremediation system for this type of wastewater first requires the selection of salt-tolerant plants. In this contribution, Halocnemum strobilaceum (Pallas) M. Bieb. and Suaeda fruticosa (L.) Forsk. were tested in experiments with mesocosms trials at different saline concentrations and hydrocarbons to study the plants tolerance and the hydrocarbon degradation capacity. The experimental campaign showed species-specific results: Halocnemum showed better tolerance to salt and hydrocarbons, and Suaeda showed better performance as hydrocarbon degradation.

The metagenomic analysis carried out on the roots of the plants at the end of the test highlighted a significant speciation of the microbial communities, especially evident at the family level. The differences detected were found both in the comparison between the different treatments and between the two plant species. In general, the Pseudomonadaceae family was predominant in mesocosms with Suaeda, whereas the Halomonadaceae family was dominant in those with Halocnemum.

In parallel, some strains showing good potential for promoting plant growth were isolated. In conclusion, the experimentation allowed to identify the operating conditions for which the technology could be exploited as a sustainable alternative to consolidated technologies.