POWERSTEP energy audits: Interview with Dines Thornberg of BIOFOS
The Danish water services company BIOFOS is taking part in the free energy audits currently being carried out by the POWERSTEP project. We asked Dines Thornberg of BIOFOS about the company's participation in the audit and his expectations.
Read below the full interview.
Dines Thornberg, your company BIOFOS A/S has been selected for the free energy audits to be carried out by the POWERSTEP project. Before we talk about the audit, could you first say a few words about your company and its current wastewater treatment operations in Denmark?
BIOFOS is the largest wastewater treatment utility in Denmark. We are receiving the wastewater of Copenhagen from about 1.2 million people. We operate three large and two small wastewater treatment plants located in central and west Copenhagen. The plants discharge 115 billion litres of cleaned water to the ocean each year. BIOFOS is a limited liability company owned by 15 municipalities and it employs 165 people.
One of your wastewater treatment plants is among the 20 WWTPs selected for the free energy audits that will be performed by the POWERSTEP project partner Veolia Germany. Which one of your plants will be undergoing the audit and why was BIOFOS A/S interested in participating in these audits?
The two largest plants, Lynetten and Avedøre, will be energy audited with the software tool OCEAN. For BIOFOS, the auditing is one activity among many that reaches the strategic goal of becoming as energy-producing as possible, while still cleaning the water to the required standards. The audit will help us to pinpoint the areas where we should prioritise actions on energy saving and production.
Could you say something about the current energy consumption of your wastewater treatment plants? What kind of treatment technologies do you currently have in place?
BIOFOS is overall an energy producer today. In 2016, we bought 55 GWh (power, heat, oil) and sold 91 GWh (heat, biogas, power). We aim to increase the ratio between bought and sold energy.
The water treatment is based on activated sludge plants with biological removal of nitrogen and phosphorus. Digesters produce biogas on the basis of both primary and secondary sludge. The digested sludge is dewatered, dried and mono-incinerated in two plants. The plant in Lynetten is exploiting the heat created during the treatment process so as to export it to the district heating system in Copenhagen.
From your experience, what do you see as the biggest challenge in transforming the current energy-consuming wastewater treatment process into an energy producing, or at least energy-neutral, process?
I believe the single most important unit to obtain energy productivity, is the digester. The production of biogas is crucial to obtain an energy-positive status. There are many tricks to optimising the gas production and more are under development.
Of course, the use of energy is also important. The challenge is to treat the wastewater to an even higher quality without affecting the energy consumption too much. Since the price of oil, and energy in general, has been decreasing in the last few years, this actually poses a challenge to the business case of many of the actions we would like to take on both energy saving and production.
As part of the auditing process, specific scenarios will be developed to show the benefits of implementing the POWERSTEP concept in the WWTPs. What expectations do you have from the energy audit and the POWERSTEP technologies?
We expect to gain knowledge on the key technologies of POWERSTEP so as to better understand how they work and to maximise the potential for energy saving and production. We also hope to receive important input for BIOFOS-specific business cases that will form a basis for decisions on potentially large investments.
Dines Thornberg is Development Manager at BIOFOS. He is trained as a Chemical Engineer and holds an industrial PhD in the control of WWTPs. His department employs five people and manages 10-15 projects with a focus on resources and processes that allows for the company to meet new emission standards.
Read more about the energy audits here. The results will be made available in a summary report at the end of the project.