Within the Interreg ANCHOR project, four demo sites across the North Sea Region are exploring how vacuum‑based wastewater systems function in real‑world conditions. One of these demo sites is Oceanhamnen in Helsingborg, where NSVA operates a vacuum system designed to collect concentrated blackwater as part of a long‑term ambition to increase nutrient recovery. This article describes how the system works, why leak detection is necessary, and how NSVA monitors and tests the system to ensure reliable and efficient operation.
Why vacuum is used in blackwater collection
To keep blackwater concentrated and suitable for nutrient recovery, it must be transported under vacuum. In Oceanhamnen, the system maintains an underpressure of around –0.5 bar. When a toilet is flushed, vacuum pumps start automatically to restore the vacuum level, and the system is built with redundancy so it can continue operating during peak loads or maintenance work.
Because no vacuum system is completely airtight, small leaks are expected. Industry standards therefore specify acceptable levels of vacuum loss during commissioning. In buildings, up to 20 percent loss over a defined period is common, while sewer pipelines typically follow a standard of no more than 20 percent loss over 40 minutes. Vacuum pumps can compensate for small leaks, but larger ones increase energy demand and can compromise operation. If vacuum levels fall too low, toilets can no longer be flushed, which is why systematic leak detection is essential.
Continuous monitoring through pressure sensors
At the Oceanhamnen demo site, NSVA monitors vacuum levels continuously using pressure sensors installed in larger buildings. The sensors are placed on the vacuum pipes, positioned away from the flow direction to minimize clogging risks. Each sensor includes a display that allows property owners to check the current pressure locally.
All sensors communicate with NSVA’s SCADA system through 4G modems, providing real‑time data from each connected building. This digital monitoring is an important part of the Oceanhamnen demo site’s contribution to the wider ANCHOR project, where one objective is to compare how different vacuum systems perform across the four demo sites.
How leak detection is performed at the pump station
The pump station in Oceanhamnen contains additional pressure sensors as well as motorized valves. Each vacuum line usually serves one to three buildings, which makes it possible to isolate and test lines individually. Leak detection is typically performed at night, around 03:00 a.m., when the system is used least. During a test, a motorized valve closes a selected vacuum line, and the pressure inside the closed line is monitored. A slow drop in pressure is expected due to normal micro‑leakage, but a rapid decline indicates a more substantial leak. The following morning, operators review the pressure curves in the SCADA system to identify any unusual patterns.
Benefits for system reliability and shared learning
These monthly leak detection routines allow NSVA to inform property owners when leaks are found inside their buildings and help maintain the overall stability of the vacuum system. The experiences collected in Oceanhamnen also benefit the other demo sites within the Interreg ANCHOR project. By comparing results and operational patterns across all four locations, the project aims to build shared knowledge on how vacuum wastewater systems behave, how they can be improved, and how they can support future resource‑efficient sanitation solutions in the North Sea Region.
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