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The second filtering stage used instead these steel cylindrical filters which are closed Bollmann filters, a patented Schnellfilter, designed in Wien, in 1913, by the Steam generators manufacturing company. These filters trapped fine manganese salts, due to their quartz sand layer. This filtering layer is still used today. The sand layer was 1m deep and had a granulometry of 1-2 mm; it was laid over a 10 cm gravel substrata with particle ranges from 7 to 14 mm. The filters were delivered as subassemblies and joined on site following a hot riveting process. A travelling crane was used in order to place them and to clean them, which is still in place today.

The filtering was carried out under pressure, and the water ran through the sand layer, from the top down. Small solid particles were captured in the sand, while the filtered water was evacuated on the bed of the basin and channeled to two partially underground tanks located behind the building. 

Water treatment is performed depending on the characteristics of the water source. The quality of the ground water source in Timisoara has not changed, therefore water treatment follows today almost the exact same recipe from over one hundred years ago, by iron removal and manganese removal processes. Chlorination is the sole process added to this recipe. Drinking water should not contain any pathogens and chlorine disinfection in water treatment is one of the successful solutions in order to effectively eliminate microorganisms that are dangerous to humans. However, current installations make a huge difference in terms of its operation and maintenance. Operations that used to take hours or even days of hard labor are today a push-button or one-click away.

All done! Water is now safe for drinking and can be supplied to consumers. But how exactly? You will find out the answer to this question in the next station, the pumping house.