Within the Interreg ANCHOR project, four demo sites across the North Sea Region are examining practical solutions for maintaining and improving vacuum-based wastewater systems. One of these demo sites is in Jenfelder Au in Hamburg, where HAMBURG WASSER operates a vacuum sewer system designed to collect blackwater efficiently. A recurring challenge in such systems is the formation of biofilm and, over time, hard incrustations inside the pipes. This article describes why these incrustations occur, how they can be prevented, and how foam ball cleaning offers an effective maintenance method.
Why do incrustations form inside vacuum pipes?
Vacuum sewer systems transport wastewater using air rather than continuous water flow. When transport is not efficient enough or when small air leaks occur, moisture and organic material can remain on the pipe walls. This material forms a soft biofilm layer, which is present in all vacuum systems. Over time, the biofilm can harden and develop into thick, concrete-like incrustations that significantly reduce the internal pipe diameter. As the incrustations grow, the risk of blockages increases, and the system becomes more vulnerable to operational disturbances. Regular and effective maintenance is therefore essential to keep the pipes in good condition.
How the foam ball method works
To prevent the biofilm from developing into hard incrustations, HAMBURG WASSER uses foam balls that are sucked through the vacuum pipes. The foam balls fit tightly inside the pipe and scrape off the soft biofilm layer as they move forward. By removing the biofilm early, the formation of hard deposits can be avoided entirely. The foam ball method can be used not only in public pipes but also in smaller pipes inside buildings, making it a flexible maintenance technique.
Once the cleaning is carried out, the foam balls are removed from the system either using a foam ball catcher installed in the sewer network or directly from the blackwater tank. This ensures that the balls do not enter downstream processes.
Evaluating the cleaning results
Before and after cleaning, camera inspections are used to assess the condition of the pipes. By comparing footage from the same pipe section, operators can clearly see how much biofilm and incrustation has been removed and whether additional cleaning is needed. This visual evaluation helps refine maintenance schedules and improves understanding of where incrustations tend to develop most quickly.
Supporting long term system performance-term system performance
With regular foam ball cleaning, HAMBURG WASSER can maintain the vacuum sewer network effectively and contribute to an expected system lifetime of 75–100 years. The experience from the Hamburg demo site adds important knowledge to the Interreg ANCHOR project, supporting wider learning about how maintenance strategies can extend the lifespan of vacuum systems and reduce the risk of operational failures across the four demo sites in the North Sea Region.
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