Alternative resources and water reuse

Increase water availability through reuse and alternative resources

One way of being careful about the current freshwater resources – especially groundwater – is to use alternative freshwater resources, and to reuse the water that we do have before we discharge it to the surface water and out of the system. How do you make responsible use of alternative water resources, without putting pressure on the environment and creating risks to public health? And how do you organise the collaboration between different sectors, water supply and water demand that is needed for alternative resources and reuse?

Reuse and alternatives, from brackish groundwater to effluent

KWR works with water users on suitable alternatives, from brackish groundwater as a drinking water resource, to the use of rainwater in greenhouse farming and in the city, to the possibilities for the sustainable use of residual water from industry or treated effluent from wastewater treatment plants. In this work, KWR often establishes connections between sectors. Soil and subsurface are key to the creation of such collaborations, because that is where the space can be found that is needed for the temporary storage of water, so as to fix the temporal mismatchbetween supply and demand.

Methods, tools and products

Residual water for agriculture

The agricultural sector, and land-based agriculture in particular, needs water in the growing season, which typically coincides with dry periods when water availability is limited. At KWR, we work on exploratory research and pilot projects concerning the use of residual water as an alternative source of freshwater for agriculture. In a pilot project in Haaksbergen, we investigated whether irrigation with WWTP effluent via drainage can be used in an agricultural land parcel, and what impact this has on the water provision and the distribution of substances in the root zone and the groundwater. In the ‘Boer Bier Water’ project, this was studied using industrial residual water from the Bavaria brewery (Swinkels). Whether industrial residual water can also be stored in the subsurface for use in greenhouse horticulture was investigated in the Dinteloordpilot.

Reuse in the urban area

The urban environment has a strong demand for water – for public green spaces for instance – and climate change means that this demand will continue to grow in the future. At the same time, cities produce large volumes of residual water, and they also need to be able to quickly discharge rainwater. KWR studies whether these alternative sources are suitable – or can be made suitable – to meet part of the urban water demand. For example, the Urban Waterbuffer was developed to store rainwater in winter in order to use it in the summer to irrigate football pitches. In the Urban Photosynthesisproject we researched whether treated urban wastewater can be used to meet the water requirements of so-called blue-green roofs, a combination of solar energy with water storage.

Reuse in drinking water production

The drinking water production process generates flushing water. The amount of this water varies between production sites, but the volumes can be considerable. Together with several water utilities, KWR investigated whether this water could for instance be used for nature purposes. To this end, we developed a calculation tool which, on the basis of water and solute balances, offers insight into the effects of the reuse of flushing water on, among others, habitat factors for vegetation.

From pilots to large-scale implementation

Pilots offer an important means of closely studying the performance of innovative water reuse techniques, but making a contribution to the water transition requires the larger-scale implementation of suitable new solutions. KWR regularly explores (future) large-scale reuse applications, including within the Water in the Circular Economy (WiCE) research programme. Recent examples include anexploratory research project on current developments and future scenarios for the further use of treated industrial and household residual water, and a regional exploratory study, RWZI als Waterfabriek(WWTP as Water Factory), to quantify the potential contribution of the large-scale reuse of WWTP effluent.

Projects

  • In the regional exploratory study, RWZI als Waterfabriek (WWTP as Water Factory) which is part of the WiCE programme, we explored the role that reuse of treated WWTP effluent could play in the freshwater supply within two case studies. This alternative source of freshwater could potentially meet a significant part of the water needs of agriculture or industry. The approach and the case study results were used to develop an action framework, with which the reuse of effluent in other areas can be explored in a standardised method.
  • In the urban environment both the demand for water and the supply of residual water are substantial. This presents opportunities for closing the water cycle. In the Urban Photosynthesis project, we researched whether treated urban wastewater can be used to meet the water demand of blue-green roofs. The project revealed that wastewater from showers in the apartments can very well be treated via integrated, small-scale constructed wetlands on the roof. At the same time, the shower water can be used as a water resource for the vegetation on blue-green roofs. 
  • Many pilots are focused on reuse for low-value reuse. But can residual water also be an alternative source for water for human consumption? In the Ultieme Waterfabriek [Ultimate Water Factory] project, together with stakeholders in the water sector, we study how, and under what conditions, treated wastewater can be made available as an supplementary resource of drinking water.