Helsinki Region Environmental Services HSY

Purely better – every day

The raw water of the Pitkäkoski and Vanhakaupunki water treatment plants comes from Lake Päijänne in Central Finland, along a 120-kilometre-long rock tunnel. At the water treatment plants, raw water is treated to become supply water and then led to the water supply network.

The Viikinmäki wastewater treatment plant located in Helsinki is the largest treatment plant in Finland and the Nordic countries. The wastewater of approximately 890,000 residents is processed by activated sludge process which is located underground.

The Suomenoja wastewater treatment plant, which started as a pond treatment plant in 1963, is the second largest wastewater treatment plant in Finland. The wastewater of approximately 390,000 residents. The Blominmäki treatment plant will replace the Suomenoja plant in 2022.

Visit Viikinmäki WWTP as a technical tour of IWA World Water Conference: Join the Nordic Technical Tour – Finnish Water Way in Helsinki! – Finnish Water Forum (FI).

WWTP Blominmäki

Blominmäki wastewater treatment plant will replace the current Suomenoja wastewater treatment plant. The capacity of the Suomenoja treatment plant is no longer sufficient to treat the entire area’s wastewater because the population and expectations for intensified wastewater treatment increase.

After its completion in 2022, the treatment plant will process the wastewater of 400,000 residents from Espoo and Kauniainen, Kirkkonummi, Siuntio and Western Vantaa.

The underground facilities of the treatment plant can be eventually expanded to cater for the wastewater of over a million residents, and so the new location of the treatment plant offers facilities for at least a hundred years.

By 2040, it is estimated that 150,000 m3 of wastewater will flow through the new treatment plant daily. The volume exceeds the current volume of wastewater flowing to the Suomenoja treatment plant by about half.

The nutrient load on the Baltic Sea will be reduced from the current load. The goal is to remove from wastewater over 96% of the phosphorus and organic matter as well as over 90% of the nitrogen it contains.

Pilot Plant RAVITA™

HSY’s development work related to nutrient recovery has been based on the separation of the phosphorus nutrient fraction from the sludge fraction, which allows maximum and cost-effective nutrient recovery while also enabling more efficient wastewater treatment. We are developing a treatment method for post-precipitation chemical phosphorus sludge, the end-product of which is phosphoric acid suitable for industry as a raw material or, alternatively, ammonium phosphate to be used directly as a fertilizer. Phosphoric acid is a valuable and versatile chemical, while ammonium phosphate is suitable for use as fertilizer as such.

A RAVITA DEMO pilot plant, size class 1,000 PE, has been built at the Viikinmäki wastewater treatment plant for the development work. The aim of the pilot plant is to coordinate and optimize the sub-processes of the RAVITA process. Additional objectives include studying the quality and quality of the side streams generated and assessing the cost of the process at full scale.

Membrane filtration

HSY has recently started to look at new treatment options in drinking water treatment to answer the capacity deficit presented by a prolonged downtime of one treatment plants. Submerged ultrafiltration coupled with aluminium-based coagulant was selected into further trails, as it is capable of producing water equal to or even surpassing the coagulation-filtration process. The designing and building of a plant-scale pilot starts in autumn of 2022, and the pilot is operational in 2024.

Activated carbon

Activated carbon an effective adsorbent that removes small molecular size NOM from water and improves taste and odour of our product. However, coal-based activated carbon has substantial environmental and social impacts. We conducted an LCA and sustainability study on several activated carbon materials, focusing on both renewability and origin of the raw material. Following the conclusions of these studies, we are commencing trials for more responsible types of activated carbon in 2022.