BIOMEM could give the operator a leg up on offshore produced water discharge regulations, which are expected to become more stringent in certain areas.
Researchers at French major Total have developed a biological treatment approach to detoxify produced water. BIOMEM, which is based on the moving bed bioreactor (MBBR), has been successfully piloted in Gabon and is now undergoing final cost and risk assessments to gain internal qualification in 2021.
BIOMEM targets dissolved compounds such as polycyclic aromatic hydrocarbons and benzene-toluene-xylenes, as well as some process additives and heavy metals. Current offshore discharge regulations do not address these constituents; however, expectations of rule-tightening led Total to embark on BIOMEM’s development.
“We expect more stringent regulations across OSPAR zones [areas covered by the Convention for the Protection of the Marine Environment of the North-East Atlantic]. We also expect stricter regulation to move towards coastal Africa, where Total has many operations,” Matthieu Jacob, water treatment R&D project leader at Total’s Lacq Research Center, told WiO.
Technology already exists to remove compounds of concern (bioreactors and activated sludge, for example), but their large footprint and sensitivity to fluctuations in feedwater quality make them inappropriate for offshore oil & gas operations. These technologies are also better suited to lower water volumes and salinity levels than typically seen in offshore operations. With operational needs in mind, Jacob’s team began innovating established biological treatment technologies to create an ideal solution for offshore activities. Researchers developed BIOMEM, which entails activated sludge free biomass and supported biomass cultured under a biofilm structure directly on a biofilm carrier.
“The advantage of supported biomass is that it’s a lot more resistant to process variation or process shock in terms of produced water composition, and it also traces very well to salinity,” Jacob said.
Pilot- and bench-scale testing began at the Lacq Research Center in France using water with a salinity level of 30 mg/L at a residence time of 30 minutes. The tests yielded positive results, demonstrating significant toxicity reduction with 60-70% of targeted compounds removed via a treatment system that is six times cheaper and four times smaller than conventional technology.
In September 2019, researchers began a seven-month BIOMEM pilot at an onshore terminal in Cap Lopez, Gabon. The technology’s performance was tested on 100 g/L salinity produced water under different residence times. At three hours, BIOMEM reached more than 60% organic carbon removal efficiency and 95% biological organic carbon removal efficiency. Tests at one-hour residence times also demonstrated promising results.
“Many people say you cannot treat very salty water with a bioreactor,” Jacob said. “This Gabon test proved that you can treat very salty produced water if you acclimate your biomass correctly, and that it’s possible with this type of process to have not perfect but significant removal efficiency and a promising residence time.”
Though the technology is being developed primarily for offshore applications, first deployment – anticipated in 2023 or 2024 – is likely to be at an onshore facility to reduce associated risk and allow for the collection of more performance data.