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Reference project

Mellifiq ozone solution provides insight into cleaner drinking water

Water treatment .
Drinking water chemical and biological barrier system
Trollhättan Energi
Trollhättan, Sweden
Municipal drinking water plant
Project value (USD)


The future of drinking water in Trollhättan is now a part of Mellifiq’s sustainability agenda

Trollhättan Energi is a public utility company owned and operated by the city of Trollhättan. They supply the city with electricity, internet fiber infrastructure, and clean water among others. One of their latest projects involves building a new drinking water plant with 1500 m3 per hour to supply the city with potable water. Such a water treatment plant can take many years to design and construct. 

The problem.

The city of Trollhättan has been supplied with drinking water by the water treatment plant in neighboring Överby since 1962. After almost 60 years in operation, it is pushing past the expected 50 years of service. The machinery is outdated both in terms of lifecycle and ensuring current water standards.  

The actual plant draws water from the Göta canal, which poses several risks to the production of clean and safe drinking water. It is a high-traffic waterway for both recreational and commercial boats. Furthermore, many local industrial facilities and wastewater treatment plants are discharging effluent into it. Due to these risks, the new drinking water plant will source water directly from Sweden’s largest lake, Vänern, which has its own water composition and particular set of challenges.  

To ensure reliability in the new plant, and a high-quality solution, a comprehensive pilot project was initiated by Trollhättan Energi. The pilot project includes all treatment steps that will comprise the treatment process in the new plant. This is a way to verity the process layout and dimensions of the full-scale systems.  

The pilot project has two parts with a complete process line in small scale at Överby. A complementary study with reduced scope was performed at an existing water treatment plant in Kungälv, which already draws water from lake Vänern. The construction of a new plant will be initiated during 2023, with an expected completion in 2026. 

The solution.

Mellifiq was contacted to supply treatment systems for the pilot project, both in Överby and in Kungälv. The systems are used for meeting new demands on stricter microbial control and removal of micropollutants, such as pharmaceutical residues and pesticides. In recent studies, traces of several micropollutants such as pharmaceutical residues and PFOS and PFAS have been identified in Sweden’s largest lakes. Common practices for this purpose are ozonation and active carbon filtration, a combination which was used at both sites. 

Looking at the best available technologies, ozone was chosen as an extra microbial barrier. Several technology combinations are to be tested in order to find the right recipe to treat the unique water composition in Göta Älv. 

An Ozonetech RENA Vivo ozone system was chosen to execute two separate pilot projects at two different extraction sites. Mellifiq was able to quickly dispatch two fully equipped systems for two years rental time.  

Solution facts.
Mellifiq delivery
Engineering design, consultation, automation, Ozonetech RENA Vivo A-series, commissioning
Automated ozonation at variable output of 0.1-4 ppm dissolved ozone
16 m3/h
Solution dimensions, HxWxD (cm)


As even the smallest model in the RENA series includes all necessary features for a fully functioning water ozonation process, the design can now be scaled to fit the full-scale installation. 

The Mellifiq system can deliver Automated ozonation at variable output of 0.1-4 ppm dissolved ozone. 


The overall scope of the pilot project is to mimic the entire drinking water production process at a small scale and a much lower flow of water. Treating the actual water ensures that the new plant will deliver high-quality drinking water according to today’s standards when scaled up. By running the system during a 6-month period, important data on running cost and maintenance needs were attained.  

 The overall treatment process is configured as follows:  

  • Coagulation with subsequent sand filtration  
  • Ozonation followed by slow-filter 
  • Ultra-filtration 
  • Activated carbon filter as a  polishing step  
  • Several chemical dosing points for pH adjustment 

All products and components were assembled in containerized modules and placed right outside the current facility. This way, there was a limited intrusion on the day-to-day operations of the current plant.

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