Our Research Focus: Achieving Zero Harmful Discharge to Sea

Article by Benaiah Anabaraonye AMIChemE

Benaiah Anabaraonye discusses the Danish Offshore Technology Centre’s role in developing and accelerating sustainable offshore solutions

HYDROCARBON extraction and offshore wind power might seem worlds apart, but they share a common challenge: their impact on marine ecosystems. Understanding this connection is critical to protecting our oceans while moving towards more sustainable energy solutions.

Produced water, the largest waste stream in oil and gas operations, is a significant offshore challenge – globally, over 50 billion cubic metres are generated each year. This wastewater contains a complex mixture of reservoir brines, dispersed hydrocarbons, dissolved organic compounds, and a cocktail of added chemicals. In the North Sea region, which includes the UK and Denmark, most of this wastewater is discharged to the sea after extensive treatment. While these treatment processes mitigate environmental concerns, when the wastewater is discharged offshore, it could still have negative environmental consequences.

At the Danish Offshore Technology Centre (DOTC), based at the Technical University of Denmark, we have a clear vision: to achieve zero harmful discharge to sea. While our primary research focus is on the sustainable handling of produced water, we have recently received funding to investigate the impact of newer and less-studied offshore technologies, including offshore wind farms, on the marine environment. We are developing technologies, processes, and protocols that address current regulations and anticipate new stringent ones.

Since you can’t manage what you can’t measure, our work begins with asking a simple question: what’s in the water?

In the North Sea region, most of this wastewater is discharged to the sea after extensive treatment

What’s in the water?

The discharge of produced water is strictly regulated in the North Sea region under OSPAR (Oslo-Paris convention) guidelines, which currently set a maximum monthly average of 30 mg/L for dispersed oil in water. But this is not sufficient. In our recent review paper, we have identified critical knowledge gaps and numerous areas where current regulations can be improved.1

But perhaps, it is easier to demonstrate in the lab.

We ran a series of experiments using a simple microfluidic device to understand the behaviour of oil droplets in offshore wastewater (Figure 1). We used a real, relatively clean, offshore wastewater sample with only 4 mg/L of oil in water and showed that there are active components in the water phase. These components decrease how often smaller droplets merge (coalescence frequency), and make the separation of oil from water much harder.2

The water phase contains a cocktail of various added production chemicals, many of which are guarded intellectual properties of the suppliers. Studies also show that components in this phase, including metals and various organic chemicals, are the main drivers of ecotoxicity. The complexity of these challenges led us to develop better testing strategies. We are carrying out comprehensive ecotoxicity and biodegradability studies to understand which components of the wastewater are problematic and how long they persist in the environment. For these studies, operators provide wastewater samples freshly collected from the platform, sometimes expediting the process through helicopter transport! Our results will allow operators to assess the environmental impact of new chemicals and improve the quality of regulatory reporting.

Figure 1: Droplet generation in a microfluidic device. (a) toluene in de-ionised water, (b) toluene in offshore wastewater (4 mg/L of oil in water), (c) crude oil in offshore wastewater (4 mg/L of oil in water)

Making it happen

We are intent on creating an environment that allows innovation to thrive, and continue to make room for radical ideas. Our Radical Innovation Sprint (RIS) programme provides funding for anyone, including PhD students and industry partners, to execute unconventional ideas within a three-month timeframe. This has been a real game-changer for researchers and as a result of a sprint, we are actively developing effective biodegradable and sustainable chemicals that will replace conventional ones.

Collaboration is at the core of the way we work. DOTC is a network organisation, and my programme – one of ten – relies on the diverse expertise resident in five universities and over 60 engaged partners. When we initiated the produced water management programme in 2020, we reached out to experts both within and outside our network to join us in this mission for a world with zero harmful discharge to sea. A key part of my role is to ensure this collaborative network model thrives.

We understand the criticality of environmental responsibility. Therefore, we are focused on accelerating the technology readiness levels (TRL) of the technologies and methodologies being developed. We achieve this by assessing the TRLs of our projects at regular intervals through a gated process. At these assessment meetings, researchers, industry partners, and technical advisors – who have deep industry experience – evaluate the current state of the research and technology development to accelerate their development, identify current risks and challenges, explore application potentials, and provide a clear path for future work.

I have also seen firsthand how our unique working model, one that houses academics and industry specialists under the same roof, accelerates innovation and maximises real-world impact. I have not seen this focused approach to applied research anywhere else and wish I’d had a similar opportunity as a PhD student!

Produced water, the largest waste stream in oil and gas operations, is a significant offshore challenge – globally, over 50 billion cubic metres are generated each year

From lab to pilot

This focused approach to applied research has allowed us to move studies beyond the lab. I will highlight three projects for now.

Two of our projects have received grants from the Danish government’s Energy Technology Development and Demonstration Program (EUDP). These grants support universities and companies as they develop and demonstrate novel energy technologies. In the first project, we are developing the world’s largest moving bed biofilm reactor (MBBR) for the treatment of offshore wastewater. The goal is to significantly reduce, through biological treatments, the impacts of problematic chemicals in produced water. Further, unlike many treatment technologies, MBBR will have a rather low footprint as it will be placed on the seafloor below an oil platform. We are currently making final modifications to the reactor in preparation for the next phase of tests. In the second project, we are developing a new oil-in-water sensor that combines advanced fluorescence and complex data analysis techniques. These techniques allow us to better quantify the distribution of several components in the wastewater. We regularly test the performance of this new sensor on real samples and at realistic process conditions (Figure 2). It’s perhaps too early to say much about the sensor, but after analysing the leading sensors on the market, we are convinced that we are providing a technology that is more accurate and better accounts for the complexities of the components in crude oil. It is also a fast and low-cost technique that does not require sample preparation.

We are also working on treatment solutions for triazine-based hydrogen sulfide (H2S) scavengers, a chemical family that, while effective, has a significant negative environmental impact on marine ecosystems. In some cases, they constitute over 50% of the overall expenditure on production chemicals. We are developing new membranes to separate and recycle unspent scavengers, while applying oxidation techniques to eliminate toxicity in the waste stream before discharge in the ocean. These technologies are being tested at a wastewater treatment facility and preliminary results look promising.

Figure 2: Pilot plant at Aalborg University, Esbjerg. The DOTC test new devices and control systems under representative conditions

New horizons

The shift from oil platforms to offshore wind farms will inevitably lead to significant reductions in carbon dioxide emissions and will play a critical role in the green transition. It is, however, important to recognise that wind turbines rely on lubricants and other oil-based chemicals to run effectively. A leading wind turbine manufacturer recently told us that a large wind turbine could have up to 8,000 L of these fluids. Considering the larger scale and harsh operational conditions of offshore wind turbines, the risk of oil leakages becomes a pressing concern. This reality prompts a series of important questions: How do we manage accidental spills? Are the chemicals toxic to marine ecosystems? Should new regulations be put in place? Surprisingly, most environmental assessments of offshore wind farms do not address these concerns. Further, accidental discharges from offshore wind farms will have more delocalised profiles, with potentially multiple points of discharge. This could make treatment and containment more challenging.

We have recently received funding from the VELUX Foundation to assess and address the potential impacts of accidental spills on the marine ecosystems. Our first task is to systematically study the chemical and physical properties of the oil droplets – understand their size distributions and how they move in the ocean. We will then study which chemicals are toxic to marine ecosystems and whether they are biodegradable. The results from these studies will significantly improve how we risk assess and manage the inevitable expansion of offshore energy production.

In an increasingly impact-conscious world, achieving zero harmful discharge to sea is critical. My team and I are confident that the technologies we are developing at DOTC will move us towards this vision.


1. Ann F Nielsen, Anders Baun, Simon I Andersen, & Lars Skjolding, Critical review of the OSPAR risk-based approach for offshore-produced water discharges. Integrated Environmental Assessment and Management, vol 19,5 pp1172–1187 (2022), https://doi.org/10.1002/ieam.4715
2. Liridon Aliti, Alexander Shapiro, & Simon Andersen, Microfluidic Study of Oil Droplet Stability in Produced Water with Combinations of Production Chemicals. Energy and Fuels vol 37,3 pp1836–1847 (2023), https://doi.org/10.1021/acs.energyfuels.2c03294

To read more articles in this series, as it develops, visit: https://www.thechemicalengineer.com/tags/our-research-focus/

Article by Benaiah Anabaraonye AMIChemE

Programme manager for the Produced Water Management Programme at the Danish Offshore Technology Centre (DOTC)

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