Why combining natural systems with engineered treatment processes?

The synergistic benefits of cNES go beyond the mere addition of the processes. Combinations of natural systems with engineered processes increase removal efficiencies, reduce land requirements, and are essential to preserve the advantages of this low-cost, low-energy and ecosystem services providing treatment solution.

Whilst many natural treatment components have proven their effectiveness in water treatment over recent decades (Kazner et al., 2012) in addition to the ecological and social benefits compared to purely engineered systems (e.g. treatment systems as habitats, potential recreational use), their capacity may become limited due to space restrictions (e.g. size of CW and infiltration basins) or negatively impacted by flow variations during floods and droughts. Combination of natural treatment components with engineered pre- and post-treatment processes help to improve performance and increase treatment resilience of natural systems.

Benefits of engineered pre-treatment

The reasons why engineered pre-treatment is necessary prior to natural systems are presented below.

Bank Filtration

Pre-treatment does not apply to BF systems, as in case of BF (abstraction of water from aquifers that are hydraulically connected to a surface water body) there is no treatment process prior to BF.


  • Enhanced system performance and efficiency
  • Removal of critical contaminants from source water (e.g. micropollutants, pathogens, antibiotic resistant bacteria and genes)
  • Safeguarding long-term system performance
  • Improved quality of infiltrated water to meet high regulatory demands and quality standards

Constructed Wetlands

  • Improved quality of source water (e.g., ozonation as pre-treatment is able to oxidize a compounds recalcitrant to removal in wetlands)
  • Improved treatment efficiency
  • Reduced land requirements and costs

Pre Treatment Engineered Processes

The AquaNES DSS focus on three types of natural systems and their combinations with engineered pre- or post-treatment processes. The engineered pre-treatment processes under consideration are presented below.

Bank Filtration

Not Applicable

Constructed Wetlands

Examined engineered pre-treatment processes combined with CW systems

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