Enhanced Capacity and Reliability: Rehabilitation of Pressure Sewer for Safe Wastewater Disposal

In contrast to conventional gravity systems, pressure sewers rely on pumps to transport wastewater. Such systems can be used independently from land topography but require expert design and quality components to ensure their uncompromised performance while protecting public health and the environment. Pipelife Finland's expertise and excellent product range helped successfully rehabilitate an outdated pressure sewer in Oulu, Finland. 

_{A Vital Upgrade for Future Capacity}

In 2022, Oulun Vesi, the water utility in Oulu, Finland, started a major rehabilitation of its sewage network. The project's initial phase required replacing an old pressure sewer in Hietasaari, originally built in the 1970s, that carries wastewater to the Taskila treatment plant. After 50 years of service, the sewer had reached its limit, lacking the capacity to support the community of around 100,000 people. 

It was decided to replace the outdated transmission line with two new pipes, enhancing the network's capacity and ensuring safe wastewater disposal in the future. The experienced contractor Varpaisjärvi Maansiirto ja Vesitekniikka Oy (VMSV), specializing in sustainable civil engineering, was commissioned to carry out the project. 

"The new sewer line will consist of two DN 800 sewer pipes and a DN 200 sewer pipe, along with smaller branches. In the first phase, our goal was to rehabilitate a 1,160-meter section of the line," says Tomi Niemilä, Site Manager at VMSV Oy. 

_{Overcoming Installation Challenges}

Pipelife Finland supplied a comprehensive range of products for the project, including 24-meter-long HDPE pressure pipes, valves, connectors and fittings, as well as robust PE pipes with protective coating for particularly demanding installation conditions.

As the pipeline crosses Hietasaari district, a popular recreational area, the work was carried out in a way that minimizes environmental disturbance. In some areas, the felling of trees was still needed and was handled by Eräjorma Oy, also responsible for butt welding the large-diameter pressure pipes.

"We have custom-built equipment specifically designed for this type of welding work," says Ismo Pudas, Representative of Eräjorma Oy. 

According to Erkki Sonninen, Regional Manager for Eastern Finland at Pipelife, thorough planning and open communication were crucial in a project of this scale, ensuring all products were supplied to the customer within the agreed timeframe. 

"We held numerous discussions among all parties and always found solutions to any issues that arose," explains Sonninen.

_{HDPE Pipes: The Go-To Choice for Pressure Sewer Systems}

The design and quality of pressure sewer systems are critical for their long-term reliability. PE 80 pressure pipes are the preferred choice for these systems due to their light weight, flexibility, and ease of installation, which reduces the need for joints. Furthermore, PE pipes offer excellent flow properties and high resistance to corrosion, temperature fluctuations and chemicals, ensuring a service life of at least 100 years.

For particularly challenging installation conditions, such as trenchless installation, PE 100 RC pipes with an additional protective layer are used to safeguard against point loads and mechanical damage. 

_{Future-Proofing Oulu's Wastewater Network} 

The first phase of Hietasaari sewer rehabilitation was successfully completed in October 2022. Thanks to the efficient collaboration between Pipelife Finland, VMSV Oy and Eräjorma Oy, the challenging project stayed on schedule. 

"Pipelife delivered all products on time, and I would highly recommend them for similar projects in the future," sums up Niemilä. 

The project has not only addressed the immediate needs of the Oulu community by enhancing the sewer network's capacity and reliability but also set a new standard for future infrastructure projects in the region. Thanks to the use of highly durable materials and meticulous planning, the upgraded system is poised to serve the community efficiently for decades, supporting the city's growth and environmental sustainability.