About the author:
Sara Myers is associate editor for WWD. Myers can be reached at [email protected].
- Location: Basel, Switzerland
- Size: 10,000 cu meters
- Infrastructure: pumps, ultrafiltration, membranes, oxidation reactors,
- ozone generators
In 1986, a large fire at a pharmaceutical plant next to a forest in Basel, Switzerland, poisoned the area’s water. When the fire department extinguished the fire, the water was mixed with chemicals from the plant that infiltrated the soil and the Rhine River.
“The whole Rhine turned red and all the fish died,” said Beat Huesler, lead architect and director of European operations at Oppenheim Architecture who worked on the project. “That made the whole town very sensitive because the drinking water is coming from that area.”
After the accident, the town got its water from a shared water purification plant. Some years later, however, the town started to discuss having its own water plant, which ultimately became the Muttenz Water Purification Plant.
“There was a long political discussion in the town that they thought that the shared water purification plant does not do enough,” Huesler said. “They only have one filter layer or system in place and they did not want to do an additional system. After the political process, the people voted to have their own water purification plant. It was the people themselves who said we want to take it in our own hands to ensure we get the best technology possible on the market.”
A Long Process
The process of treating the water was a four-stage process, complete with its own set of challenges, separate from the difficulties to make a plant in the first place.
“The raw water is river water from the Rhine River that has been infiltrated in a wooded area. The first treatment step is groundwater infiltration. The water is being pumped up again in the advanced oxidation process,” said Jonas Löwenberg, head of sewage department and engineer for CSD Envirotec. “It is a combination of ozone and hydrogen peroxide. They are combined to produce efficient optimization of micropollutants in the water. Next is the granular activated carbon stage. Its purpose is to biologically degrade the metabolites from the first stage. The second stage is not to remove the micropollutants. We then have the activated carbon stage again, like the first stage.“
The water then has to be treated with activated carbon, Löwenberg explained. The water must be dosed until all the carbon comes out. Then, the fourth stage incorporates ultrafiltration membranes.
“They use the ultrafiltration membranes so they’re a pore diameter of 10 nanometers, so that’s very tiny. The activated carbon has a diameter of 10 μm. The pores are so small that they can also remove the bacteria and viruses,” Löwenberg said.
The fourth stage not only retains the activated carbon from entering the drinking distribution network, but also disinfects the water. Two of the stages are to remove micropollutants. The second one is for biological nutrient removal, the degradation of the metabolites and the oxidation products, and the last stage is for disinfection and removing the activated carbon from the water. The plant produces 20,000 cu meters of water everyday.
“They can do 8 tons an hour. What they need in Muttenz everyday for the city is 9,000 cu meters, and the rest of that they are selling to the region and also to the industry close by,” Huesler said. “It’s always doubled what they need.”
The facility’s volume is approximately 10,000 cu meters; however, the total usable area is about 2,000 sq meters of wooded ground filtration of the three levels inside. Building construction costs were approximately $7 million and the expenses for the building’s interior reached approximately $10 million.
Unconventional Space
Huesler explained that he and his colleagues did not want to create an industrial building in the middle of the forest, something others had done before.
“We want to have a building that speaks to the nature, and we also want to have an educational element in the building,” Huesler said. “We want to send school classes there to educate them on how the drinking water is being produced. We wanted to create a building that will have you feel the water, smell the water, and also where you can touch it.”
An engineering team was hired to construct the three-level water treatment facility. Huesler and the other architects built the shell of the building, and during the process, its location changed multiple times. They had first located it in the middle of the forest, and then was pushed further away. It now is at the edge of the forest, approximately 100 meters from where the fire occurred in 1986.
“I think it was a very unique process, I’m not sure if there is any other process like it,” Löwenberg said. “The combination of the four process stages is pretty unique for Europe. We had very little problems with it. Of course, some optimization had to be done in the beginning, especially with how much carbon was dosed. But otherwise it’s been running very well from the beginning. We have almost complete removal of the target compounds that were in there.”