Online monitoring and early warning system for bacterial contamination in public surface waters in Breda, the Netherlands

Source(s): Climate-ADAPT
Areal view of Almere in the Netherlands.
Pavlo Glazkov/Shutterstock

In Breda, a remote monitoring system for the presence of potentially harmful bacteria in surface and river waters triggers early warnings for local authorities. This allows them to take preventive measures and protect people against negative health impacts of microbiological contamination when recreating in public waters.

Due to climate change, extreme precipitation events are becoming more frequent and intense, leading to flooding and possible overflow of combined sewage systems and drinking water and wastewater treatment installations. This increases the contamination risk of recreational water, which can expose people to microbiological contaminants and the associated health risks. At the same time, these waters are used by the public to cool down on increasingly frequent hot days. Continuous monitoring of bacterial enzymes in water allows preventive actions to maintain user safety. In Breda, local city authorities and the public receive early warning notifications from an online bacterial enzyme monitoring systems, BACTcontrol, to monitor the water quality in public, surface waters and diminish the risk for disease outbreaks and adverse health effects among recreants.

Case Study Description


Over the past years, several EU countries have experienced hotter than usual summers, while at the same time heavy summer rainfall events has ravaged several areas (e.g., leading to floods in Germany and Belgium in July 2021, in Slovenia in August 2023, in Greece, Bulgaria and Türkiye in September 2023). During heatwaves, people flock to lakes, river shores and other surface waters to cool off. More frequent and intense extreme precipitation events and floods, induced by climate change, can overflow sewers and infrastructures such as drinking and wastewater treatment systems. Water catchment and sewage infrastructure congestion force untreated water and wastewater into public water systems affecting drinking water or recreational areas. This can expose the public to harmful micro-organisms, which represent a health risk of gastro-intestinal illnesses, itch or other illnesses. It is essential to quickly detect faecal pollution (by the presence of enterococci and toxin-producing E.coli. bacteria), which is a strong indication of the possible presence of several pathogens (including viruses, bacteria, parasites), and inform the public whether it is safe to swim in specific areas.

In Breda, people seek cooling during hot summer days near the municipality's surface waters (such as De Singel canals, Waterakkers or Belcrum Beach), which are not allowed to become official bathing waters due to the proximity of sewer overflows and agricultural production land. The Breda authority is however responsible for public health and aims to inform the public about the water quality in surface waters in a reliable and effective way.

Microbiological methods for assessing water quality have long relied on collecting samples and quantifying the microorganisms from a sample of culture. Given the low frequency of sampling (1x/week) and the long sample processing time, people may have already been exposed to contaminated water and been infected by the time the results are available. Alternatively, preventively restricting access to potentially contaminated recreational water while waiting for sampling results, may unnecessary impede the public from cooling.


The overall objective of online enzyme monitoring and early warning in Breda is to monitor microbiological water quality of its open waters and to mitigate negative health impacts due to deteriorated water quality. More specifically, this includes: -Improving, accelerating and allowing for more frequent detection of incidents impairing microbiological water quality; -Reducing the time between contamination and response; -Informing/alerting public authorities and the public about water quality and restrictive measures.

Adaptation Options Implemented In This Case


The city of Breda shares up-to-date information on the water quality of its surface waters that are frequently used by the public for recreation. Maps visualize traffic light information based on bathing water quality standards from the Bathing Water Quality Directive, i.e. green for water quality meeting the standards in official bathing waters[1]; orange for water quality meeting the standards in non-official bathing waters; red for surface water quality below the standards, hence posing a health risk. To allow for a quick and effective assessment of the water quality, the city of Breda uses an online enzyme monitoring system, BACTcontrol[2]. It allows early detection of deterioration in the microbiological quality of water, enabling preventative actions and early warnings to maintain the microbiological quality of water and to protect public health.

The BACTcontrol sensor continuously takes samples in the water and analyzes them on the spot for the presence and activity of specific enzymes of E.coli, coliforms, enterococci and bacteria in general, as an indicator of the presence of bacterial contamination. The system transmits the measured data online to a data platform, where local city authorities can consult, review and translate the information. If threshold concentrations are exceeded, warning notifications and changed traffic light information are exchanged with the public via a public website. If the microbial concentrations reduce and meet the bathing water quality standards again, the system allows for a quick removal of the warning message to the public. Physical water sampling and lab or mobile analysis complement the online enzyme monitoring system after the latter has given a warning message for further investigation and evaluation of the contamination.

[1] Since there are no surface waters that are allowed to become official bathing waters in the city, the green light is not assigned in Breda.

[2] Manufactured by microLAN, the Netherlands


Case developed and implemented as a Climate Change Adaptation Measure.

Additional Details

Stakeholder Participation

The implementation of the water quality monitoring and early warning system involves several stakeholders, including public authorities in water management, public health and recreation, local (i.e., city level) and national regulators, as well as the research and private sector stakeholders. The regional water authority (Waterschap Brabantse Delta) in collaboration with Aquon is responsible for data collection, while the city of Breda focusses on data processing and disclosure. While the BACTcontrol technology was developed by the private company microLAN and the measuring plan by the private company Partners4Urbanwater, engagement of water management and public health authorities in the city of Breda[1] contributed to successful development and implementation of the integral operational system.

[1] The system was also implemented and tested in other cities, including Amsterdam (the Netherlands)

Success and Limiting Factors

The BACTcontrol system allows for quick analysis (1-2 hours) and requires limited manual work, which can be carried out at the sampling location in contrast with conventional microbiological methods requiring lab-grown cultures (24-48 hours). This results in almost real-time warning messages in case of contamination, which contributes to the prevention of health risks.

Costs and Benefits

The system costs around EUR 85 000 on an annual basis. This includes the annual cost for operating the BactControl sensor between May and September (bathing season) of around EUR 30 000. The required lab sampling and analysis for microbiological contamination complementing the in-situ enzymatic measurements cost around EUR 20 000 annually. Annual costs for the management of the public website with warning message and water quality information sum up to EUR 10 000, while another EUR 25 000 has to be allocated to data analysis, policy follow-up and work instructions.

At the macro-level, the speed and accessibility of online monitoring and early warning for bacterial contamination in public waters prevents significant social and environmental costs by protecting public health against water-borne diseases. The online monitoring system provides public authorities with continuous insights into the water quality of surface waters, which allows them to issue timely warming messages. Climate change is expected to increase the frequency of incidents compromising surface water quality, so public health authorities, water utilities, municipalities and recreation managers can prevent significant social and environmental costs by being prepared to rapidly detect microbiological risks and respond to water quality issues.

Existing legislation such as the European Bathing Water Directive regulate water quality in recreational waters. As online enzyme monitoring is a developing technology, it is currently not regulated nor required under existing regulatory frameworks for bathing waters.

Implementation Time

Completion of testing and validation of the enzyme monitoring and early warning system takes several months.

Life Time

In the future, the online monitoring and early warning system will remain highly relevant for stakeholders involved in water management and public health. Considering warming and the projected increase in flooding, authorities responsible for managing surface water quality will increasingly rely on monitoring tools to manage microbiological contamination and early warning systems to protect human health. Very specifically, the BACTcontrol sensor is developed to require limited maintenance and to function unattended for several months. The associated portal that issues early warning system for the public requires regular updates.


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