Sewer Water Harvesting to Support Urban Green Spaces

The overall aim was to provide a conceptual design example of how SWH could be applied in
the Amsterdam context to uncover what kind of impact can be achieved and advise on how SWH can
be implemented From an analysis of potential applications, irrigation of UGS during dry periods was
selected for the focus of the study. Suitable locations were identified, from which the Vondelpark was
selected as study area for this research. Quality requirements for irrigation water and discharge of
treatment residuals were determined. The water demand of the study area was determined by
modelling the soil moisture balance using transformed weather data, taking into account climate
change. Based on these requirements, a conceptual design of an SWH-unit comprised of fine
screening, MF, NF and UV steps. To evaluate this potential impact for Amsterdam as a whole, the
findings from the study area were extrapolated. The cost of SWH were compared to alternative water
sources and the potential direct economic benefits. This demonstrated that costs of SWH are
acceptable and can be further decreased. Furthermore, the potential impact on plant and soil health was
evaluated. Interviews with stakeholders identified barriers and opportunities of SWH and resulted in
some recommendations for larger scale implementation.

The results of this research indicate that SWH can provide a new and reliable water source
during dry periods to support UGS. SWH-units can be designed as mobile and modular units that can
for a large part be operated and monitored remotely. The results further demonstrate that potential
negative environmental effects can be prevented or mitigated and SWH can even improve the plant
and soil health of UGS. From an engineering perspective, challenges related to the water quality are
unlikely to be insurmountable. However, three aspects still require a significant amount of time and
investment before SWH can be implemented on a larger scale. These are: (1) the lack of regulatory
framework, (2) the unresolved responsibility for operation and (3) extensive water quality testing and
environmental impact assessment. To accelerate innovation it is recommended to start as soon as
possible with addressing these remaining issues. Commercial operation of SWH can provide an
interesting opportunity, all the more so because SWH can also be used for household or industrial
applications. The involvement of a wider variety of stakeholders can further help to overcome the
remaining barriers.