MUSCAT, Oman — According to a study conducted by researchers at Sultan Qaboos University, the material used to support microbial biofilms could influence their potential role in treating water generated during oil production.
Produced water is the water brought to the surface during oil and gas extraction. It is a major waste stream from the petroleum industry and may contain salts, hydrocarbons, and other contaminants. Constructed wetlands can provide a nature-based approach to its treatment, partly by supporting microbial communities that interact with and potentially break down pollutants.
In this study, researchers examined whether different supporting materials affect the formation, abundance, and composition of biofilms inside a 14-hectare constructed wetland treating oil-produced water located in Rima, Oman (managed by Veolia).
Biofilms are communities of microorganisms that attach to surfaces and grow within self-produced protective layers. The properties of the supporting surface can influence the establishment of microorganisms and the development of the community.
The researchers placed plywood, polypropylene, and natural marble surfaces across three tracks within the constructed wetland. After 30 days, they collected and compared the biofilms that developed on the three materials. They also analyzed the microorganisms suspended in the produced water and those found in naturally floating biofilms.
The results showed that the surface-attached biofilms contained approximately 240 to 3,100 times more bacteria than the surrounding produced water.
Among the three materials, plywood supported the highest bacterial counts. Depending on the wetland track, bacterial abundance on plywood was approximately two to nine times greater than that on polypropylene and three to 11 times greater than that on marble.
Plywood recorded the highest chlorophyll-a concentrations, reaching up to 6.9 micrograms per square centimeter. Chlorophyll-a was used as an indicator of photosynthetic biomass within the biofilms.
Using 16S ribosomal RNA gene sequencing, the team examined the microbial communities associated with different surfaces. Bacteria accounted for more than 98% of the microorganisms detected in the samples, while archaea contributed less than 2%.
The microbial composition of the attached biofilms also differed from that of the surrounding water. The produced water contained a high proportion of Epsilonproteobacteria, whereas the surface-associated biofilms were dominated by Gammaproteobacteria and Alphaproteobacteria and exhibited greater microbial richness.
Functional predictions based on the identified microorganisms indicated that surface-attached biofilms were enriched in bacterial groups associated with hydrocarbon degradation. This enrichment reached up to 55% on wood compared with up to 40% on polypropylene and marble.
Microscopic examination further revealed that the wood-supported biofilms contained a greater abundance of rod-shaped, spherical, and filamentous microorganisms. Image-based spatial analysis also showed stronger continuity in the microbial communities growing on wood.
The findings indicate that the choice of supporting material can substantially shape the biomass, diversity, and predicted functional potential of biofilms in constructed wetlands. Plywood may therefore provide a favorable surface for developing microbial communities associated with hydrocarbon degradation.
This information could help guide the design of future biofilm-based systems for treating water from oil production. However, the researchers did not directly measure whether plywood-supported biofilms removed more oil, hydrocarbons, or other contaminants from the water.
The hydrocarbon-degrading potential was inferred from the microorganisms detected and their known functional associations. Therefore, further experiments are needed to measure contaminant-removal rates, treated-water quality, and long-term performance before wood can be recommended as a more effective treatment material.
The research was led by PhD candidate Arwa Al-Hadhrami under the supervision of Dr. Daniel Blackburn and conducted by a Sultan Qaboos University team representing the College of Agricultural and Marine Sciences and the Water Research Center, Oman. The work received financial support from Veolia Oman.
The article, “Substrate materials determine hydrocarbon-degrading biofilm communities in an artificial wetland for oil-produced water treatment,” was published in Environmental Advances in October 2026.
Environmental Advances
Experimental study
Not applicable
Substrate materials determine hydrocarbon-degrading biofilm communities in an artificial wetland for oil produced water treatment
1-Oct-2026