Sweden. City of Stockholm

Date of agreement:13 Jun 2016
Customer:City of Stockholm
Amount in SEK:SEK 3,000 million
Amount in EUR:EUR 321.7 million
Maturity:10 years
NACE sector / loan type:Sewage and refuse disposal, sanitation and similar activities

This loan has a positive effect on maritime environments: 100%

Financing from NIB Environmental Bond proceeds

NEB-eligible share: 100%

NEB category: Water management and protection

Amount disbursed: EUR 317.2 million

Note: For loans in other currencies than EUR, the equivalent in EUR is based on the exchange rate effective for the disbursement. Read more about the NIB Environmental Bonds


The loan has been provided for an expansion of the Henriksdal underground wastewater treatment plant and to construct a 15-kilometre sewer tunnel under the southern-central part of Stockholm, Sweden.

The City of Stockholm has decided to double the capacity at Henriksdal to more than 500,000 cubic metres per day and close its wastewater treatment facility at Bromma. The wastewater currently collected at Bromma will be transported by gravity to Henriksdal through the new tunnel at depths of between 23 and 55 metres.

This will increase the capacity of Stockholm’s sewer network. In addition, the production of biogas at Henriksdal will almost double to 35 million normal cubic metres per year.

The city estimates that an annual population growth of around 2.5% could result in a capacity need for a population equivalent to 1.6 million people by the year 2040. Improving the sewer network will also lessen overflows of untreated wastewater discharged into Lake Mälaren.

The use of membrane bioreactor (MBR) technology at Henriksdal is expected to significantly reduce discharges of phosphorous and nitrogen into the Baltic Sea. The MBR will also prepare for the installation of pharmaceutical cleaning equipment, if that becomes a legal requirement.

Stockholm is the capital of Sweden and the most populous city in the Nordic–Baltic region, with 923,516 residents at year-end 2015. The city is one of the fastest-growing regions in Europe and benefits from a strong economy and a rapidly growing population.

Fulfilment of NIB's mandate


The extension of wastewater services will increase the flexibility to gradually accommodate higher wastewater loads from a growing region. While the quality of wastewater treatment is generally high in Stockholm, investments are needed to accommodate population growth and the increasing frequency of heavy rain.

The increased quality of the wastewater treatment is expected to have a positive impact on the productivity of public sector services.


The increased transport capacity of the sewer network is expected to reduce the overflow of untreated wastewater into Lake Mälaren from an estimated 185,000 cubic metres annually to less than 10,000.

The new MBR technology will result in 40% lower discharges of phosphorus and 33% lower discharges of nitrogen into the Baltic Sea. It will also remove all particles larger than 0.04 micrometres, i.e. all microplastics, from the wastewater.

Sustainability summary

This is a project with a potentially extensive environmental and/or social impact (category A, read more)

The major potential for negative environmental impact relates to noise during the construction phase of the tunnel. No risk is foreseen of any negative impact on groundwater quality. Leftover materials from the tunnel construction will be used at building sites in the Stockholm area.

The city will change its sludge treatment technology, and the production of biogas will almost double to 35 million normal cubic metres annually from 18.2. The increase is largely due to the treatment of external organic waste in the form of food waste and fats from fat separators.

Press release

NIB finances world’s largest underground wastewater facility

Press release

NIB finansierar världens största underjordiska reningsverk