Finland. Turun Seudun Puhdistamo Oy

Date of agreement:30 Sep 2020
Customer:Turun Seudun Puhdistamo Oy
Amount in EUR:EUR 9 million
Maturity:30 years
NACE sector / loan type:Collection, purification and distribution of water

Financing from NIB Environmental Bond proceeds

NEB-eligible share: 100%

NEB category: Blue Bond project

Amount disbursed: EUR 9 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 additional loan has been provided to Turun seudun puhdistamo Oy (TSP) for the construction of a new wastewater removal channel at the Kakolanmäki wastewater treatment plant (WWTP) in Turku, Finland.

In 2018, NIB provided a EUR 15 million loan for TSP’s investment programme. The pre-estimated project costs have increased from EUR 30 million to EUR 48 million, hence creating a need for further financing. Due to new tendering procedures, some works were postponed and project completion is now estimated for spring 2023.

The project is aimed at adapting the wastewater and storm water systems to deal with the impacts of climate change.

A new effluent removal channel will be constructed underground from the WWTP to the harbour, as the capacity of the existing combined sewer is insufficient and leads to system overflows during heavy rainfall.

The project will separate the wastewater and storm water discharge systems, and thus increase their efficiency. It will enable the plant to use its full capacity during downpours and limit the amount of unrefined wastewater discharged into the Baltic Sea.

The Kakolanmäki WWTP processes wastewater from approximately 300,000 residents as well as industries in the Turku region. Its operator, TSP, is a wastewater treatment service provider that is owned by 14 municipalities, with the city of Turku having the largest shareholding.

Fulfilment of NIB's mandate


The investment is a significant addition to the company’s tangible assets and will secure the supply of water treatment services in the region in periods of heavy rainfall, which are expected to increase over the coming decades. Further, it will improve zoning flexibility in urban areas, as insufficient capacity in the underground drainage system would require more surface area to be allocated for storm water management.


The new effluent removal channel will enable the WWTP to utilise its full water treatment capacity during extreme weather conditions. It will reduce overflows of untreated wastewater as well as the nutrient and microbiological load on the environment.

Moreover, the investment will prevent the systems from flooding in the future, as heavy rainfall is expected to become more frequent and maximum sea levels are estimated to rise.

The microbiological load will be further reduced by installing effluent disinfection units with ultraviolet light technology. The microbiological concentration is estimated to decrease from approximately 16,500 E. coli per 100 millilitres of water to a maximum of 500 E. coli / 100 ml.

Impact indicators in relation to the investments:

  • Affected population
  • Volume of treated water
  • Summary of the wastewater system overflows
  • Average and maximum microbiological concentration in the effluent

Sustainability summary

No significant negative environmental or social impacts have been identified in relation to the project. The investment is in accordance with the existing environmental permit of the wastewater treatment plant and has been considered in the local master plans.

Press release

NIB provides additional loan for Turku’s wastewater treatment modernisation

Press release

NIB ger ytterligare lån för Åbos moderniseringsprojekt för avloppsrening