This feasibility study being conducted in Bornholm is investigating ways of purifying the treated wastewater from wastewater treatment plants so that it can be used as ultrapure water (UPW) for the production of hydrogen by electrolysis (PtX). In order to satisfy these high requirements, membrane-based technologies such as reverse osmosis (RO) are required to purify the treated wastewater effluent.
If successful, the island’s seven existing wastewater treatment plants, or an envisioned centralised one, could provide the required amount of ultrapure water that a potential 0,8-gigawatt PtX plant will need for operation. While wastewater is the main focus, the option of using the same purification processes to produce ultrapure water from brackish water is also being considered. Brackish water, with Baltic Sea water near Bornholm at 7 – 8‰ salinity, is a cost-saving option for electrolysis.
- Location: Bornholm island (Denmark)
- Water source: Treated wastewater from wastewater treatment plants
- Type of treatment: Membrane-based technologies such as reverse osmosis (RO)
- Target water quality: Ultrapure water (UPW)
- Utilisation: Hydrogen production by electrolysis
- Return to natural cycle: WWTP recirculation, environmental discharge (diffusion systems) or Zero Liquid Discharge (resource recovery)
- Responsible: BEOF – Bornholm’s Energy & Utility Co. A/S
- Available: Summer 2025