The main purpose of the lighthouse project VARGA was to transform a traditional wastewater treatment plant into a Water & Resource Recovery Plant. The name, VARGA, is an abbreviation of the Danish name, Vandressource Genvindingsanlæg. In addition, the project has aimed to ensure that the resources in the city’s wastewater and waste are utilized even better than they are today and that more consideration is given to which resources should be harvested from the wastewater for the benefit of the city’s citizens.

The conventional treatment plant was rethought as a resource plant that both purified wastewater and made full use of resources. This was demonstrated at one of Denmark’s largest treatment plants Avedøre (capacity of approx. 400,000 PE) which was constituted a case for demonstration of Danish environmental technology in an international context.

Circular economy was central to the project and the experiences gained further contribute to the Danish national goal of an energy and climate neutral water sector in 2030 as well as the UN agenda on sustainable development.

The lighthouse VARGA project started in 2017 and was completed in 2023.

The project investigated essential parts of the circular economy, focusing on the utilization of carbon and nutrients in urban waste and wastewater to produce biogas and organic food, respectively. The project sought to create synergies utilizing resources across the water, waste, and organic farming sectors.

Major elements in the project included pre-filtration in full scale, phosphorus recovery at pilot scale and active reduction of nitrous oxide (N2O) as well as implementation of several innovative technologies within wastewater treatment, nutrient recovery, and greenhouse gas reduction.

The project has covered the following aspects

• Carbon harvesting and primary sludge concentration
• Phosphorus recovery from sludge ash
• Separate digestion of source-separated organic municipal waste (MSW) with biogas upgrading to biomethane
• Reduction of climate footprint from nitrous oxide emissions, in particular
• Life Cycle Assessment (LCA)
• Economic impact calculations

The project has allowed the parties to delve into many aspects and the results speak for themselves.

After the project, it is now possible to say that the project has helped outline the forward-looking goals for the future treatment plant.

Instead of a conventional wastewater treatment plant, we need to look at wastewater treatment plants as resource plants that both treat wastewater and sustainably utilize resources. Hereby taking into account both the environmental and economic conditions as well as the local infrastructure and industrial symbiosis.

The VARGA project has provided results for an in-depth analysis of how a wastewater treatment plant can be transformed into a resource recovery facility that supports cities and society’s desire for a more circular economy.

In addition, the development project has contributed to knowledge about the potentials and challenges of transforming today’s treatment plants into the future of plants, focusing on recycling and better utilization of resources.

Initial results showed that the Total Added Value was higher after implementing the VARGA concept compared to business as usual – without compromising the treatment efficiency.

The benefits have spread like ripples and paved the way for many new development projects, innovation collaborations, and the start-up of a new company.

At the same time, VARGA, as a reference project, has contributed to an increased business potential for the commercial partners and has created joint dissemination activity with more than 50 presentations at conferences and 14 scientific articles.

BIOFOS, Envidan, ARC, UNISENSE and DTU Sustain were the partners who in collaboration found new methods for achieving CO² neutrality and resource utilization in VARGA.