Water treatment is a major challenge for the oil industry. Although TotalEnergies' first choice is to inject produced water back into reservoirs, a lot of it is still being discharged into the environment — taking care to comply with today's standards. Processes, especially biological treatment, already exist to remove the dissolved organic compounds that the technologies currently used on offshore platforms can't treat. But their physical footprint and the equipment weight are incompatible with offshore operations.
To satisfy the new E.U. regulatory requirements, we developed the BIOMEM process, which uses microorganisms that can detoxify produced water more cheaply and with a minimal footprint.
Treating Produced Water Offshore, a Major Challenge
Hydrocyclones and dissolved air flotation (DAF) tanks are installed on our offshore platforms to treat suspended hydrocarbons and ensure the quality of produced water. But this equipment cannot remove dissolved organic compounds, which is a problem now that a new E.U. regulation requires the industry to demonstrate that it has largely detoxified water discharged close to production sites.
Hence the interest in biological solutions, which are used for municipal and industrial wastewater treatment and the biosorption of pollutants such as metals. Bio-solutions are found in TotalEnergies' refineries, which use activated sludge to remove dissolved carbon and nitrogen pollutants. However, this kind of biological treatment requires more space and time than small sites or offshore oil and gas production operations can afford.
So our R&D teams tackled the challenge of reducing the size of the biological process involved by half to two-thirds. They wanted to develop a solution scaled to existing or new onshore and offshore sites, which would be cheaper to use and meet more stringent environmental requirements.
BIOMEM, a Proven-Effective, Disruptive Solution
Our researchers decided to focus on Moving Bed Biofilm Reactor (MBBR) technology. MBBR uses microorganisms that grow a biofilm naturally in tube beds that float in surface-aerated bioreactors. The project has several steps:
- Past laboratory tests at the Lacq Research Center (PERL) proved that the system was effective. It had also been shown that biological treatment could be effective even on produced water containing up to 180 g/L of sodium chloride (NaCl).
- In 2016, the BIOMEM demonstrator, with a flow rate of 4 cubic meters an hour, was installed at a production site in southwestern France to test the process on real produced water. The tests proved that the water can be treated with an hour of residence time, much less than the usual treatment requires. The demonstrator was also equipped with a final stage involving membrane filtration with reverse osmosis, in order to demonstrate the feasibility of desalination after biological treatment when there are plans to reuse the water.
- In 2018, Total plans to conduct a validation pilot to nail down the process in line with salinity. With that accomplished, a first commercial-scale application could be implemented.
Besides being one of the few solutions to meet the requirements of the updated regulations, BIOMEM can save operators a lot of money. For example, for a water flow rate of 100 cubic meters an hour (15,000 barrels a day), BIOMEM could slash investment costs two-thirds compared to a recent project using a conventional process, while offering a footprint small enough for an offshore installation.
The BIOMEM demonstrator in southwestern France.
Water quality before and after treatment in the BIOMEM demonstrator.
Biofilm aeration tube bed for the bacteria.
Sampling on the BIOMEM demonstrator.
Inside the demonstrator – pretreatment.