How do we use water? What is the state of our water resources? What are the impacts of climate change? Important questions to which there are often no simple answers. Only one thing is certain: Due to climate change, the management of water resources faces new challenges. For this reason, we concentrate all our efforts on tackling these issues at KWB.
Many regions, including our home region Berlin-Brandenburg, struggle with heavy rainfall and drought, and solutions for sustainable water management are needed. The water demand for private use, industrial and agricultural purposes has to be as covered in the long term as the demand for our ecosystems, forests and wetlands. Brandenburg already suffers from a severe water stress, Berlin from increasing water stress. Low precipitation levels of well below 600 millimetres per year lead, among other things, to a declining groundwater recharge, to crop failures or to forest damages. In recent years, long periods of drought and heat still exacerbate the situation.
Water reuse in europe
To reduce the pressure on water resources, the new EU Regulation 2020/741 on “Minimum Requirements for Water Reuse” has been in force since June 2020. So far, the regulation only applies to the irrigation of agricultural land with treated wastewater (aka reclaimed water). From June 2023, the regulation will be valid in all EU member states.
Countries such as Spain, France and Cyprus already successfully use reclaimed water for irrigation. The water shortage in these countries has made this necessary for many years. The different practices will now be standardised across Europe. Based on the WHO standards, minimum requirements are being set, particularly for hygienic water quality.
However, the standardisation leaves some questions unanswered. For example, although risks of water reuse for the environment are considered in risk management, implementation and countermeasures are not specified. Instead, requirements are to be defined on a site-specific basis in order to minimise environmental and health risks, which involves enormous efforts in risk assessment and risk prevention.
In Germany, reclaimed water is discharged into rivers or other surface waters and can be returned to the regional water cycle, as in Berlin. In dry regions, the proportion of the wastewater treatment plant effluent in the water body corresponds seasonally in some cases to more than 50 percent of the water quantity. It thus represents an important quantitative contribution of the necessary minimum runoff of the water bodies.
Controversial: Reclaimed water in agriculture
Among other topics, our research projects are dedicated to minimising quality risks in water reuse. The EU project AquaNES demonstrated synergies between technical and natural water treatment processes to reduce the content of bacteria and viruses as well as anthropogenic trace substances (e.g. pharmaceutical residues). In Berlin, the combination of ozone treatment with constructed wetlands and activated carbon filters for treating the sewage plant effluent was tested as a possible process for advanced wastewater treatment. According to the new EU regulation on water reuse, the wastewater treated in this way could be used for the irrigation of agricultural products that are not intended for raw consumption.
Whether the new EU regulation actually creates incentives for water reuse in Germany remains questionable. According to a study by the German Federal Environment Agency (UBA, 2016), there would be sufficient water resources for agriculture in Germany, although an increase in the amount of irrigation of up to 75% is expected locally. The costs for the required infrastructure expansion (e.g. for the water transport from sewage treatment plants to the fields) appear high. There are also other measures that can be taken to respond to climate change: for example, modified crops or water-saving irrigation techniques.
All in all, the reuse of reclaimed water for agricultural irrigation is technically feasible, but its demand and implementation remain controversial in Germany. In Berlin and Brandenburg, reclaimed water is partly used to support the water balance and indirectly to support drinking water supply. Berlin’s water service provider Berliner Wasserbetriebe, to give an example, has set up an advanced wastewater treatment scheme to remove pharmaceutical residues at the Schönerlinde WWTP. The plant effluent is also used to irrigate the surrounding forest and meadows. This demonstrates that there wouldn’t be hardly any obstacle to the use of purified wastewater in agriculture – except for the competing existing water use, such as the minimum runoff of water bodies, groundwater recharge or other irrigation purposes. Finally, holistic water use concepts are always to be recommended that consider the multifaceted usage interests in the respective region.
Author Elisa Rose, Researcher at Kompetenzzentrum Wasser Berlin
