Environment The second most expensive project in the entire Helsinki metropolitan area is underway in the middle of Espoo – now the work of the years is coming to an end

Pallid the blue light shines in the underground abyss. The light is particularly visible because the overall look of the Blominmäki wastewater treatment plant is engineered gray.

The odor characteristic of wastewater is not yet floating in underground facilities, as the new plant will be commissioned in Espoo next summer. The treatment plant already looks pretty complete, but the final installations and extensive system testing will take time.

The blue light comes from UV treatment using ultraviolet radiation, which makes the treated wastewater even cleaner before it starts flowing from Blominmäki for eight kilometers towards Finno and the discharge pipe to the sea. UV treatment kills bacteria.

When completed, Blominmäki will replace the old Suomenoja treatment plant and treat the wastewater of 400,000 inhabitants from Espoo and Kauniainen, Kirkkonummi, Siuntio and Länsi-Vantaa.

This EUR 488 million construction contract is the second largest infrastructure project in the Helsinki metropolitan area extension of the western metro after a billion contract. Laajasalo tramway the main contract ranks third.

UV cleaning is just one of the technical intricacies of Blominmäki. The latest is disc filters that trap phosphorus and the smallest crumbs in their membranes.

Managing Director of Helsinki Region Environmental Services (HSY) Tommi Fred and Blominmäki Project Manager Kari Reinikainen are satisfied with the operation of the completed facility.

In Blominmäki, 96 per cent of phosphorus and 90 per cent of nitrogen can be treated from wastewater. The Gulf of Finland thanks.

Disc filtration has been tested at the Viikinmäki wastewater treatment plant, but Blominmäki is the first large Finnish plant to install these. The technology is already in use in a few small treatment plants.

The disc filter equipment manufactured by the French group Veolia came to Finland from Sweden in giant containers. Finnish installers installed the equipment.

Inside each housing rotates 30 2.5-meter-diameter film-coated discs through which tiny holes are squeezed into the wastewater. The discs occasionally rise above the water surface, allowing a hard lateral shower to clean the membranes.

In some Dark water is already visible in the giant cleaning basins of Blominmäki, but they only prohibit test use. Pool leaks have been patched and pumps, drainage routes and bottom scrapers have been tested.

Scrapers that look like giant irons transport sludge and solids out of the cleaning process. The sludge is pumped to the digester.

The heat from the wastewater is also recovered. In terms of heat, the treatment plant is self-sufficient. The biogas generated in the digester is also recovered. Blominmäki is able to generate 70% of its electricity needs itself.

Sewage treatment plant The placement to the north of Ring Road III means that the wastewater flows back and forth under Espoo. For decades, the flow of sewers has been directed towards Suomenoja. There will be no change to this.

Instead, the connecting tunnels excavated into the rock transport the wastewater collected to Suomenoja eight kilometers further north to Blominmäki. The treated wastewater travels back to Suomenoja and towards the discharge tunnel.

In addition, kilometers of wastewater accumulate within Blominmäki from one treatment process to another.

There are numerous connecting pipes inside the plant, which direct the wastewater to different stages. The lowest point of the treatment plant is 20 meters below sea level. Wastewater from this inlet pumping station is first lifted up 30 meters to the start of the treatment process.

The plant has a lot to maintain and clean to ensure a smooth process.

“We have a cleaning day every day,” says Reinikainen.

Blominmäki the underground world is confused by its size assessment. Something says the number of excavations. Approximately 800,000 cubic meters of rock have been excavated for the halls and connecting tunnels of the treatment plant.

This corresponds to about eight Parliament Houses.

However, rock is also left for possible extensions. Pools could be excavated on Blominäki to treat the wastewater of 540,000 people by 2040.

“In Viikinmäki, Helsinki, the expansion reserve has already been used. If you want to expand the treatment plant there, you should use neighboring rock, ”says Tommi Fred.

Blominmäki construction began with excavations more than six years ago, in the fall of 2015. It had been preceded by years of planning and decision-making.

As the largest investment in HSY’s history now begins to be completed, more time will be spent on other tasks under the leadership of the contract. HSY has a long list of water and sewer connections to be renovated.

“It is great that Blominmäki is being completed, but at the same time it has been easier. There have been many difficulties along the way, ”Fred describes.

The construction work will not get rid of even in Blominmäki, as the line of the Espoo – Salo straight line has been adapted next to the treatment plant. The new train line towards Turku would be below Ring Road III and would run on the bridge next to the Gumböle golf courses towards Mynttilä.

Read more: The waste of almost half a million people will soon flow to Espoo – Photos tell what a huge cave looks like now