The way to a biocide-free city – NAVEBGO research project to investigate the impact of biocide substances on groundwater at the University of Freiburg: a conversation with Prof. Jens Lange, hydrologist and project coordinator.

“For humans, animals and plants, groundwater is the most important resource for survival and is therefore considered particularly worthy of protection…

More than 70 percent of drinking water comes from groundwater. It is therefore the most important drinking water resource in Germany.”

(taken from the website of the BMUV German Ministry of Environment – on the subject of water protection )

“Biocides are chemicals or microorganisms used in the non-agricultural sector to combat pests. The difference to plant protection products is that biocides are intended to protect human health and products, while plant protection products are intended to protect plants. This means that the type and place of application are also different (on people or in their home – in the field or in the greenhouse and storage).” (Wikipedia)

Measurements in the groundwater carried out by the University of Freiburg found biocides contained in facade paints. These are organic additives that are known as pesticides in agriculture and are now largely banned there. While the use of pesticides in the agricultural sector has been well researched, the same toxins can still be found in conventional facade paints.

As mobile substances, biocides are washed out of facades by heavy rain and get into the groundwater. To examine these connections in more detail, the NAVEBGO project was set up in an interdisciplinary manner as part of the Interreg Oberrhein with the support of EU funds and ended on September 30th, 2022.

We talk to Prof. Jens Lange, Professor of Hydrology at the University of Freiburg and NAVEBGO project manager, about the importance of the project – a summary follows here:

In addition to studying the substances, the field of investigation included many sociological aspects and looked at all stakeholders involved in facade design. On the one hand, there are painters and decorators, paint manufacturers, architects, but of course also the residents of the houses and their perception are a crucial element, as these are an important lever to eliminate biocidal contamination in the future.

In general, fungi and algae on house fronts are considered dangerous and ugly, so they are quickly painted over when stains appear on house walls. Fungi and algae on the outside of houses are not pests but should be a natural part of the urban ecosystem of the future.

There is often no knowledge about these connections. The current trend towards white cubes when building houses also promotes the leaching of pollutants, since flat roofs create a large surface area for rain to attack.

On the other hand, pitched roofs with overhang help to keep rainwater away from the facades. The sustainable planning and design of urban development must therefore also consider a possible change in trends in architecture.

New approaches and alternatives to the tendency to paint white are green facades (in Freiburg there is a municipal subsidy program for builders to green facades and roofs), clinker or stone walls. The creative eye of architects can find alternatives here through greenery, materials, and their mixture with artistic, new elements.

A solution to the biocide problem must therefore take various directions into account – when asked about what he believes to be the most creative solution of recent times, Prof. Lange mentions a lecture by Linus Stegbauer, University of Stuttgart, who is working on greening with microalgae, which is applied to the wall with a special Gel and provides filtering and cooling effects.

Many elements and their interaction are important for water management in the city of the future. The reduction of biocides as described here is one such area, along with the recycling of gray water (household water), seepage (sponge city principle) and renewable energies, as well as digital applications for the management and control of water.

A follow-up project for NAVEBGO is already being planned to investigate further sources of biocides in households. Biocides in wastewater (service water from households) flow directly into the sewage treatment plants and are not completely broken down there.

Biocide research is a young branch of science and offers many new tracks to water protection. The group of researchers in this field is currently still manageable – the University of Freiburg and the NAVEBGO project play an important role in putting this science into practice.

The biocide research and a lecture by Prof. Lange, findings from the funding project on facade greening of the city and other related topics to do with water and SDG 6 are interesting additions to specialist conferences that are planned in Freiburg.

Architects, urban planners, sustainability concepts, paint manufacturers, painters, etc. will find a concentration of experts and case studies here that make it worth holding the next conferences in Freiburg.

Project website in German and French

NAVEBGO findings to download


If you plan a conference and want to wrap it around SDG 6 – Water and Sanitation, contact:

Christina Fritsch, Project Head Freiburg Convention Bureau / MICE / Netzwerk

Tel.: +49 761 3881-15 25 • Mobil: +49 151 22 507 198  •

See you in Freiburg!


A FrauBlau project for water and conferences.

Congresses, conferences and meetings must create meaning and contribute to positive change. To see them only from a commercial point of view does not go far enough. In this series, we present aspects related to SDG 6 – water and sanitation, which enable new programs and knowledge exchange on these topics in Freiburg.


Johanna Fischer /FrauBlau – an initiative of ecomice

for Freiburg Convention Bureau, October 27, 2022