Blominmäki sets a new benchmark for wastewater treatment in the Baltic Sea region
At the HSY Blominmäki wastewater treatment plant, Valmet’s automation and measurement solutions enable reliable and high-performance operations in a demanding process environment. Real-time data and centralized control have improved process stability, while supporting everyday efficient decision-making. The outcome is enhanced environmental performance and a significant reduction in nutrient discharges to the Baltic Sea, positioning Blominmäki among the most advanced wastewater treatment plants in the region.
The HSY Blominmäki wastewater treatment plant represents a major step forward in sustainable wastewater management in the Helsinki metropolitan area, in Finland. Built to replace the aging Suomenoja plant, the investment was driven by stricter environmental requirements, population growth, and the need for improved energy efficiency and treatment performance.
Designed to treat wastewater from approximately 500 000 inhabitants by 2040, the underground facility plays a central role in reducing nutrient discharges into the Gulf of Finland. Wastewater flows were gradually redirected to Blominmäki between November 2022 and January 2023, marking a carefully managed transition to full operation.
Following commissioning in 2021–2022, the plant reached stable and efficient operation in 2024. This progress was particularly evident in nitrogen removal performance, with significant reductions both year-on-year and compared to the period before the new plant came online. The nitrogen load from HSY’s treatment plants into the water system decreased by 16% compared to the previous year, and by 54% compared to the period before the Blominmäki plant was operational. These improvements have delivered clear environmental benefits by reducing nutrient inputs to marine waters. By 2025, HSY’s Blominmäki wastewater treatment plant in Espoo had established itself as one of the most efficient treatment plants in the Baltic Sea region.
Valmet DS and Valmet LS installations at Blominmäki treatment plant
Building a foundation for operational excellence with Valmet solutions
The Blominmäki plant placed an order with Valmet as part of the plant’s start-up project. The order included the Valmet DNA automation and information management system, as well as measurements for solids control; Valmet Total Solids Measurement (Valmet TS), Valmet Dry Solids Measurement (Valmet DS), and Valmet Low Solids Measurement (Valmet LS). The scope also covered field engineering of the automation application and instrumentation, factory acceptance testing, automation system installation, commissioning, and training.
HSY’s long-standing experience with the Valmet DNA automation system, especially at the Viikinmäki treatment plant, provided continuity and supported its efficient adoption at Blominmäki. HSY’s Viikinmäki underground treatment plant has been operating with Valmet’s automation system since the 1990s. The system has been continuously updated, and in the future, operations of the new Blominmäki plant can also be controlled from the Viikinmäki control room.
“At HSY, we already have extensive experience with Valmet DNA from our other facilities, which made it a natural choice from an operational perspective. Familiarity with the system supports maintenance, development, and daily use,” says Marina Graan, Head of Production Unit, HSY.
A key benefit of the system is improved process visibility. Operators have access to real-time information across the process, enabling faster decision-making and more consistent control. This helps maintain the treatment performance even when inflow conditions vary.
The automation system provides good overall visibility to the process, and the user interface at Blominmäki is clear and relatively easy to navigate, which supports daily operation.
Valmet’s delivery also included solids measurement that provide continuous data on solids content and process conditions, supporting process monitoring in an environment where sludge characteristics can vary significantly.
Valmet TS installations at Blominmäki treatment plant
The benefit of these measurements lies in improved process awareness. Reliable and real-time data helps operators identify changes earlier and respond proactively, contributing to more stable sludge handling and dewatering performance. Continuous measurement also reduces reliance on manual sample retrieval, improving operational efficiency.
Reliable solids measurements are critical for our process control. Continuous data gives us real-time insight into sludge conditions, helping us monitor the process more effectively and respond quickly to changes. It also reduces the need for manual sampling and supports more efficient use of chemicals, such as polymers, while helping us maintain stable and consistent performance.
Together, automation and measurement solutions support a more controlled and predictable process. Improved monitoring and stability are essential for achieving consistently high treatment performance, while also helping to minimize disturbances and optimize plant operation.
Today, the Blominmäki wastewater treatment plant has established itself as one of the most efficient facilities in the Baltic Sea region. Its strong environmental performance demonstrates how modern technology, combined with operational expertise, can deliver measurable results in reducing nutrient loads and improving water quality.
Key facts
Customer: HSY (Helsinki Region Environmental Services)
Location: Espoo, Finland
Plant type: Underground wastewater treatment plant replacing Suomenoja
Order placed: 2019
Delivery: 2020–2021
Commissioning: 2021–2022
Full operation: January 2023
Design capacity: Approx. 500,000 inhabitants (forecast 2040)
Valmet delivery
- Valmet DNA automation and information management system
- Valmet Total Solids Measurement (Valmet TS) – 12 units
- Valmet Dry Solids Measurement (Valmet DS) – 4 units
- Valmet Low Solids Measurement (Valmet LS) – 5 units
- Field engineering of the automation application and instrumentation
- Factory acceptance testing
- Automation system installation
- Commissioning & training
Key results and benefits
- Significantly improved nitrogen removal performance after plant start-up
- Nitrogen load reduced by 16% year-on-year after stabilization and approximately 54% reduction compared to pre-Blominmäki operation
- Substantial decrease in nutrient discharge to the Gulf of Finland
- Improved process visibility through centralized automation
- More stable and predictable plant operation
- Enhanced operator ability to respond to process variations
- Reduced need for manual sampling through continuous measurements
- High overall treatment efficiency positioning the plant among the most advanced in the Baltic Sea region
