🔬 Introduction: what are bacterial sensors?

Bacterial sensors, also known as microbial biosensors, are measurement devices that use living microorganisms as the sensing element. Unlike traditional chemical or physical sensors, biosensors respond to environmental changes through a biological response - such as changes in fluorescence, enzymatic activity, or biomass growth.

Their job at wastewater treatment plants is to detect heavy metals, toxic substances, organic overload, and changes in pH and oxygen levels in real time, among other things. It's not just an add-on - it's an early warning system.

⚙️ How do bacterial sensors work?

A typical biosensor consists of:

• reaction cell - bacteria's habitat,
• detection system - For example, electrodes, cameras, photodetectors,
• processing interface - Converts the biological signal into digital data,
• communication system - sends data to SCADA or the cloud.

Example? Bacteria E. coli glowing in the presence of mercury - the stronger the fluorescence, the higher the concentration of the toxin.

🧪 Practical applications in treatment plants

• Detection of industrial discharges - The bacterial response is faster than classical analysis.
• Protection of activated sludge - warn of compounds that destabilize biological processes.
• Heavy metal monitoring - alarm before toxic ions affect nitrifying bacteria.
• Zone monitoring in networks - help identify sources of pollution.

🧬 Types of bacteria used in sensors

The most commonly used microorganisms:

• Escherichia coli - Reacts to many toxins, easy to modify,
• Pseudomonas putida - resistant, useful with organic substances,
• Vibrio fischeri - Natural luminescence, ideal for light testing,
• Bacillus subtilis - strong, aerobic, popular in screening tests.

Some sensors use bacteria from local bio-sediments - they adapt better to the conditions of the treatment plant.

⚠️ Advantages and limitations

✅ Advantages:

• rapid response to toxins,
• low operating costs,
• high sensitivity,
• continuous operation,
• SCADA integration capability.

❌ Limitations:

• The need to refresh the bacterial cultures,
• Sensitivity to changes in pH and temperature,
• lower selectivity than classical chemical probes,
• Formal difficulties (e.g., legalization).

🌍 Examples of implementations

• Germany: Bavaria - sensors Vibrio fischeri have detected illegal discharges into rivers.
• France: Marseille - system E. coli controls rainwater effluent.
• Poland: Poznan - Local bacteria detected toxic contamination from chemical industry.

🤖 The future of biosensors

• Integration with AI (analysis of biological reactions),
• Miniaturization (coin-sized sensors),
• Self-renewing colonies,
• ISO eco-certification (using biosensors as evidence of environmental response).

💬 Summary

Bio-sensors are the modern eyes and ears of wastewater treatment plants - sensitive, cheap, fast. When everything is based on biology, it is worth listening to those who feel it best: microorganisms. And if they say "too much" - it means something is wrong.

Do you have questions? Are you testing such sensors at your place? Let us know in the comments!