Jun 25 2009
HELSINKI – Ari Nevalainen showed an encoded piece of plastic to an electronic sensor. In front of his little white car, a gray aluminum door, set into a granite hillside, cracked open and the two halves slid into the rock walls.
Mr. Nevalainen, gaunt and serious, tapped the accelerator and the car rolled forward, taking us into a subterranean world that looked like something out of James Bond: an eerily-lighted tunnel, high and wide enough to accommodate a tractor-trailer. Big stainless steel pipes snaked along the top of the tunnel.
We parked in a big open space, maybe 90-feet beneath the ground, glowing in a wash of pale yellow light. Something that smelled like sulfur was strong in the air. We were at the heart of one of Finland’s biggest environmental projects: a sprawling underground factory that turns the city’s sewage into almost drinkable water then pushes it out through a separate tunnel nearly five miles into the Baltic Sea. Out there, in a sea so polluted that the herring are choking, Helsinki does no harm.
“We’re proud of the quality of our waste water,” said Mr. Nevalainen, the chief spokesman for Helsinki Water, the municipal water works. So far, he said, no one from the James Bond movies has tried to rent the underground location. But, he agreed, it would be a perfect place for shoot-em-up chase scenes.
The objective of the Helsinki plant is to get rid of the city’s waste without further damaging the Baltic Sea. The people of Helsinki have been struggling against ghastly pollution in the Baltic Sea and the closer Bay of Finland for nearly a century. More than half a dozen countries are still polluting the Baltic though most them have agreed to work together on a clean-up.
Helsinki set up its first sewage treatment plant in 1910 when complaints started coming in that you could not have a decent picnic or go for a swim off a popular beach. The city’s toilets needed emptying somewhere and the beach was suffering.
In those days, most of Europe just dumped its waste and found other places to picnic. Eighty-four years later, in 1994, Helsinki opened the phantasmagoric Viikinmaki treatment plant that I visited. With their spare sense of style and design, the Finns wanted a place where the waste water could be converted into harmless goop without smelling up the city and without disturbing the landscape – the winter’s snow blanket and the green of summer.
So they put their main sewage treatment plant deep underground. It was not such great shakes for them. They already had tunnels wending under much of Helsinki, for shopping and parking, especially in winter.
Down there below Helsinki, Tommi Fred, the director of waste water treatment for Helsinki Water, showed me how it was done. From all over Helsinki, sewer lines converge on the Viikinimaki plant. The sewage comes in 150 feet below the ground and gets pumped up into huge, rectangular vats that reveal some hint of the contents with their sharp aroma.
The water rushes through metal screens that catch clumps of waste and debris. Then it slows down to let sand and grit settle. The waste water goes into another tank where dark, thick sludge gradually sinks to the bottom. Next the dirty water – minus the sludge - moves into another set of deep, rectangular tanks. Dozens of devices that look like shower heads are set into the bottom of the tank, pointing up. The shower heads spray air into the water and curls of white foam form on the surface.
The sludge gets heated and compressed and eventually trucked off to be sold as a nutrient for lawns and gardens. In the process, the sludge gives off bio gas which is used to heat the plant and which provides 50 percent of its electricity.
In the final step of cleaning, the waste water is run through a concrete vat filled with millions of tiny white polystyrene balls that draw off the last of the bacteria – a quality-enhancing measure used in only a few other countries. Powerful electric pumps then drive the water though the rock tunnel into the Baltic.
The Helsinki plant, experts say, is one of the most effective in Europe. “We are certainly one of the lowest in operational costs,” Mr. Fred said, “and with excellent quality.”
Professor Riku Vahala, an engineer who specializes in water at the Helsinki University of Technology, said that 15 years after opening, the Viikinimaki plant is no longer the fanciest, most advanced waste treatment plant in Europe. But, he said, Helsinki still gets more bad stuff out of its sewage than do most others.
“It’s how they fine tune it,” Professor Vahala said. “That’s how they take the best results out of the plant.”