Verweildauern

Verweildauern (singular Verweildauer) is a German term used across multiple disciplines to denote the time something remains within a defined system before exiting. The plural form Verweildauern is used when discussing several instances or compartments.

In engineering and environmental science, Verweildauern describes how long a parcel of water, a chemical, or a pollutant stays in a reactor, a storage basin, or a river reach. For a well‑mixed volume, the mean residence time τ equals V / Q, where V is volume and Q the volumetric flow rate. More complex models exist for non‑ideal, heterogeneous systems.

In healthcare, the related Verweildauer, or length of stay, measures how long a patient remains in hospital or ward and is used for capacity planning and benchmarking.

In pharmacology and toxicology, residence time describes how long a drug or contaminant remains in tissue or a bodily compartment, affecting exposure, pharmacokinetics, and risk assessment.

Interpreting Verweildauern requires attention to boundary conditions, input and removal processes, and system geometry. Longer residence times imply slower turnover, while shorter times indicate rapid clearance or flushing. Limitations include simplifications in idealized models and heterogeneity of real systems; residence times can vary with flow, season, temperature, and biogeochemical processes.

Etymology: from verweilen (to linger) and Dauer (duration).