Europe: towards the use of wastewater for irrigation

On 13 May, the European Parliament definitively adopted the regulation on the reutilization of wastewater. The Commission, which had proposed this text in 2018, hailed this decision, considered as a step forward in limiting water shortages aggravated by climate change.

 

By harmonizing the rules in the European Union, and by setting minimum quality requirements, this new regulation provides a framework for facilitating the used of non-potable wastewater for irrigating farmland. The member States have been given a deadline for bringing their installations into conformity with the regulation (priority being given to wastewater treatment plants) of 3 years. The objective is to quadruple the reutilization of wastewater from now to 2025, to reach 6.6 billion cubic meters.

Agriculture, a thirsty drinker of water

The agricultural sector consumes on average 22% of the total volumes of water withdrawn in Europe. However, the situation is highly variable, with certain countries in southern Europe systematically resorting to irrigation for their agriculture, which alone monopolizes up to 80% of withdrawals. In these countries, irrigation can multiply agricultural production by six and the profits derived from the production by four. The same variability can be observed for the reuse of wastewater, as a function of more or less severe national regulations: France uses only 0.6% whereas this figure is 9% in Italy and 13% in Spain. Globally, recourse to irrigation remains relatively modest in Europe.

Water withdrawal ratios by continent – Source : FAO 

At the global level, Kuwait, Israel and Singapore, countries subject to severe droughts, feature at the forefront regarding irrigation, if the percentage of water reused in relation to the total quantity of water used is considered. Retreated wastewater is used for a variety of functions: the irrigation of green spaces and crops, firefighting, washing roads and recharging aquifers. The world’s foremost pioneer is the State of California, which issued the first regulations on water use at the beginning of the 20^th century. Since then, California has evolved with ever more efficient treatments to ensure water of excellent quality, and has become a model for many countries. To conclude this worldwide overview, the case of Singapore stands out. Due to its very dense demography and climatic conditions, this island of 699 km² had to face increasingly serious water shortages, making it turn to the reuse of wastewater. To achieve this, Singapore developed an innovative treatment process that combines microfiltration, reverse osmosis and UV radiation. This strategy, named NEWater, above all serves the industrial sector although part of the water produced is mixed with water of natural origin before feeding the drinking water network. Today, 5 plants supply a third of Singapore’s drinking water requirements. The aim is to cover 50% of demand by 2060.

Facilitate the reuse of wastewater in a consumer and environmentally friendly way

This new European regulation therefore opens the door to a change in practices, by adapting the regulation, by imposing health requirements and greater transparency for consumers, in order to remove another barrier, this time psychological, that of acceptability. The European Commission emphasizes the fact that “citizens will have access to online information on the practices utilized regarding water reuse in their member States”. This information will be of different types: the quantity and quality of the recycled water; the permits issued; the results of conformity controls, etc., updated at least once a year.

The reuse of treated urban wastewater represents a genuine opportunity for agriculture in the context of climate change. In addition to its availability, treated wastewater is an alternative source of nutriments, confirmed by the FAO in a report dating back to 2010. In particular, it estimated that if all the “black water” (raw sewage) was exploited, the use of nitrate fertilizers could be reduced by 30% and phosphate fertilizers by 15%. Lastly, the environmental benefits are obvious, since it would reduce withdrawals from rivers and aquifers.

Although proof of wastewater reuse for agriculture by the civilizations of ancient Greece and Rome, the potential for development lies before us, combined with research into circular economies. The conditions of success include the transformation of infrastructures, with wastewater treatment plants which should be designed as resource recovery plants, according to Marc Heran, Professor at the University of Montpellier – European Membrane Institute (EMI).