Water reuse for irrigation
This content is extracted from Pistocchi et al., 2018, under Decision 2011/833/EU
Water reuse has been identified by the European Commission as a relevant solution to be further promoted in the EU to address water scarcity. This opportunity was highlighted again in the context of the EU action plan for a Circular Economy (COM(2015) 614 final). In particular, the Commission committed to table a legislative proposal setting minimum quality requirements for water reuse. This initiative has been included in the Commission Work Programme 2017. In order to support the decisions to be taken on the matter, the costs and benefits of water reuse need to be clearly identified and quantified to the best possible extent.
The JRC (Pistocchi et al., 2018) has estimated the distribution of costs of reclaiming and transporting treated wastewater for reuse in agricultural irrigation across Europe. The assessment considers treatment costs as well as the costs associated to the water transport infrastructure and to energy for pumping. The study highlights a high variability of costs depending on the location of irrigated agricultural land with respect to the wastewater treatment plants. Treatment costs alone may be minor, about 8 €cents/m3, compared to the other costs, with the majority of the theoretical water reuse volume available at typical total costs below or at 50 €cents/m3. However, when treatment requirements become more stringent, treatment costs are expected to increase to 0.23 €/m3, causing total costs to shift consistently. The energy requirements for pumping of reclaimed water from wastewater treatment plants to agricultural land follow a distribution with a median of about 0.5 kWh/m3 and an interquartile range of another 0.5 kWh/m3, which seems slightly higher than reported in representative cases of irrigation with conventional water sources.
The total volumes of water that can be in principle reused for irrigation are significant and may contribute to the reduction of water stress up to around 10% in regions where irrigation is an important component of demand. Water reuse may also contribute, in a less apparent and more uncertain way, to nutrient pollution mitigation.
While the treatment and energy costs are rather minor, the total costs depend significantly on infrastructure costs and the distance from the UWWTP to the irrigated land, therefore for farmers the attractiveness of water reuse will vary. This indicates that
- reuse is most suitable where irrigation infrastructure already exists and the necessary additional investments are limited,
- the cost of water reuse should be considered in a broader context as a water management tool.
This context should be extended to include, on the one side, the whole value chain supplied by agriculture and, on the other side, the process of river basin management where reuse may represent a measure with important co-benefits.