​​The municipality of Kalajoki sits on Finland’s west coast in the Gulf of Bothnia, the northernmost arm of the Baltic Sea. The area is an extremely popular tourist destination, especially during the summer months when bathers and other visitors flock to experience the Hiekkasärkät sand dunes, Rahja archipelago, and tens of kilometers of nature trails, among other natural treasures.

​​Founded in 1968 by the municipalities of Sievi, Nivala, and Ylivieska, Vesikolmio is responsible for the region’s water distribution, wastewater treatment, and sewer network, and is the largest water utility in Finland today. The water supply is drawn from groundwater and serves approximately 54,000 people.

​Wastewater is processed on behalf of approximately 30,000 people at Vesikolmio’s Keskuspuhdistamo central treatment facility, which was completed in 2018. “Keskuspuhdistamo is a biochemical co-precipitation plant. The treatment process comprises pumping stations, screening, sand removal, an activated sludge process, and a flotation unit,” explains Petri Lamminaho, Operating Supervisor at Vesikolmio.

​​During the first phase of the project the facility processed wastewater from the towns of Kalajoki and Ylivieska and the municipalities of Alavieska and Sievi. During the second phase of the project, completed in 2022, the facility also began processing wastewater from the towns of Haapajärvi and Nivala. The Keskuspuhdistamo facility now serves a population equivalent of 40,900.

​​Protecting bathers and nature with fast, effective wastewater disinfection

​“During the summer bathing season from May 1^st to August 31^st we disinfect wastewater before it is discharged to the Baltic Sea,” says Vesikolmio CEO Risto Bergbacka. “This is in accordance with our environmental permit, but we also apply disinfection during other periods when it is deemed necessary by wastewater quality.” During summer, the permitted limit for E. coli in wastewater is 1,000 CFU/100 ml and for intestinal enterococci 400 CFU/100 ml.

​The environmental permit requires that wastewater disinfection is performed in such a way that it does not harm fish species or other aquatic organisms. Vesikolmio therefore turned to long-term partner Kemira to support them with this requirement. “We have an excellent working relationship with the team at Vesikolmio, so we were happy to support them with planning and implementing the disinfection step at Keskuspuhdistamo, explains Kemira’s Eelis Kähkönen, Account Manager, Central Finland, Industry and Water.

​Vesikolmio chose Kemira KemConnect™ DEX for this purpose – a proven solution for the chemical disinfection of everything from raw water to industrial and municipal wastewater and stormwater overflows. KemConnect™ DEX uses performic acid, which is manufactured on-site in a specially designed unit supplied by Kemira.

​KemConnect™ DEX is easy to integrate into existing water treatment infrastructure without large capital expenditure.

​​Performic acid is very effective at low doses with a short contact time of less than 10 minutes, degrading very quickly in treated water. It has a high toxicity to bacteria and pathogens and low toxicity to aquatic life.

​​“A big advantage of this kind of treatment is that the systems and equipment needed are easy to integrate into existing water treatment infrastructure without large capital expenditure,” Kähkönen points out.

​“Compared to a technology such as UV disinfection, Kemira’s solution was a much more economical and low-maintenance option,” says Bergbacka. “We can scale the disinfection process up or down as needed simply by adjusting the dosage based on real-time data about the wastewater quality.”

​Compared to a technology such as UV disinfection, Kemira’s solution was a much more economical and low-maintenance option.

​“Furthermore, KemConnect™ DEX was extremely easy to take into use,” highlights Lamminaho. “We received good support from Kemira throughout the planning and implementation process as well as comprehensive training for our staff on site.”

​Vesikolmio’s goal is to clean wastewater economically, efficiently, and with respect for nature. “We strive to utilize the best available technology in wastewater treatment and we are constantly developing our operations,” says Bergbacka. “Kemira’s solution has been working extremely well since it was installed, and we look forward to continuing and further strengthening our cooperation in the years to come.”