Urban Water Interfaces

Interfaces

...between natural compartments (natural interface: e.g. surface water - groundwater).

...in technical systems (technical interface: e.g. waste water - gas space in sewer systems)

or

...between natural and technical systems (e.g. bank filtration)

The urban water system

Urban water systems are characterized by close linkages between:

  • Natural aquatic ecosystems that have been heavily modified in terms of their morphology, water and material fluxes, and aquatic communities.
  • Large-scale technical systems for water production, water treatment, water storage and distribution for drinking water consumption, waste water and runoff collection and treatment, and subsequent discharge into receiving waters.
  • Multiple uses such as waterways and recreational activities.

Of the multiple natural and technical interfaces in the urban water cycle, we consider in particular:

Water surfaces

Water surfaces serve as bidirectional exchange surfaces for water, gases, particles, and heat between the atmosphere and urban water bodies. The expected temperature increase due to climate change strongly affects this exchange, impacting evaporation, greenhouse gas emissions, cyanobacterial bloom formation, non-native species invasion, urban lake ecosystem dynamics, and urban microclimate.

Urban soils and vegetation

Städtische Böden und Vegetation stehen in Verbindung mit der Atmosphäre und dem Grundwasser und werden durch den Eintrag von Schadstoffen (z. B. Schwermetalle, Salze und Reifenabrieb) stark beeinträchtigt. Sie sind vom Temperaturanstieg infolge des Klimawandels betroffen, dienen der Grundwasseranreicherung und der Speicherung von Regenwasser oder geklärtem Abwasser und wirken sich durch Evapotranspiration ("green fluxes") positiv auf das städtische Mikroklima aus.

Aquifers and sediments

Aquifers and sediments interface between urban water bodies and the subsurface and act as dynamic sinks and sources of urban water and solute fluxes in the hyporheic zone and in bank filtration ("blue fluxes") through the degradation of pollutants such as micropollutants. Their ecological functions are generally severely impacted by engineered systems and management measures and are likely to be further altered by climate change.

Sewer systems

Water treatment

Among the technical interfaces, water treatment links the (waste) water phase with the solid phase, includes treatment of groundwater, surface water, and waste water, and provides opportunities for innovative control of pollutant removal (e.g., trace organics) through natural (e.g., deiodination, sorption) or advanced engineering processes (e.g., anaerobic or microbial transformations).

Fluxes and processes at interfaces describe the exchange of water, solutes, gases and energy.

They are quite complex, characterized by steep physical and biogeochemical gradients, a high number of (micro)organisms and reaction rates, coupled nonlinear processes with feedback effects in possibly heterogeneous and dynamic structures.

The linkage between natural and engineered systems is evident in bank filtration, discharge of treated waste water to surface waters, recharge of polluted runoff, and artificial ground water recharge. These processes are very complex and a comprehensive understanding requires further detailed studies on the coupling of physicochemical processes and microbiological transformations under different environmental conditions.

The UWI research training group continues to focus on the similarities of interfaces at different scales. By studying several urban water interfaces, we plan to generalize interface concepts in terms of measurement, modeling, and scaling methods and techniques during the second funding period. This remains a unique selling point and a key strength compared to other collaborative research projects that focus on single interfaces in less complex environments than the urban water system. Increased research will be conducted on commonalities between a range of natural and engineered urban water interfaces, for example gas exchange processes at water surfaces of urban water bodies and at (waste) water surfaces in sewer systems.