Teräväniemi wastewater treatment plant

Renovation increases the efficiency of the Äänekoski wastewater treatment plant

Äänekoski is a lively industrial city of about 18,000 residents located at the southern end of lake Keitele in Central Finland. Äänekosken Energia Oy is in charge of the city’s water management, district heating and electricity transmission network. The wastewater treatment plant, built in the 1970s, was modernised and renovated by Suomen Maastorakentajat, these days known as NYAB, in a massive project that was completed in 2018. The renovation gave the plant another 30–50 years of more efficient, environmentally friendly activities.

The Teräväniemi wastewater treatment plant in Äänekoski is one of the largest municipal installations built in the 1970s. Renovations were in order due to the old age of the plant, the need for increased capacity and the stricter environmental permit requirements which the old plant could no longer fulfil. In addition to the waters of the municipal residents, the plant also treats water from the Valio plants.

Äänekosken Energia, the owner of the plant, divided the project into three contracts for competitive tendering: the renovation of the main building, the construction of new aeration tanks and a new post-treatment facility. The contracts included the renovation of the building and the replacement of the machinery, electrical installations and HPAC. With its special expertise and strong market position in water infrastructure projects, NYAB won all the contracts. The total value of the project amounted to about EUR 10 million.

Sustainable development

The new Teräväniemi treatment plant fulfils strict environmental requirements and treats wastewater with the activated sludge process which makes use of microbes. The water that is released into lake Keitele after treatment is extremely pure, and the comprehensive automatisation of the plant ensures consistent treatment results around the clock. In addition, the treatment plant uses the heat recovered from the wastewater.

“Stricter discharge limits require more extensive treatment of the water, which increases the running costs of the plant. However, the improved energy efficiency means lower running costs, and the environmental impact is considerably smaller, thanks to the reduced emissions. The increased capacity enables the plant to also treat the wastewater from the nearby population centres of Suolahti and Sumiainen that previously had a separate treatment plant which had also arrived at the end of its service life and was, consequently, run down. This created savings in the overall running costs,” says Äänekosken Energia’s Production Engineer Atte Myllylä, who was in charge of the project.

The project proceeded according to plan and the cooperation with the client was efficient from start to finish.

“Renovating a wastewater treatment plant is a more challenging project than building a new one as the plant needs to remain running at all times,” says Construction Manager Aleksi Rajala from NYAB. “We have implemented several similar projects in the last decade. Now, most of the large wastewater treatment plants built about 50 years ago have been renovated, but our work continues with smaller plants and other water infrastructure projects.”