Immobilised activated sludge based biosensor for biochemical oxygen demand measurement

Area of Science:

• Environmental Science
• Biotechnology
• Analytical Chemistry

Background:

• Online monitoring of biological wastewater treatment is crucial for process efficiency.
• Existing sensors, like those based on activated sludge, often suffer from short lifetimes.
• There is a need for robust, easily maintainable sensors for real-time wastewater analysis.

Purpose of the Study:

• To develop and evaluate a novel biochemical oxygen demand (BOD) sensor for on-line monitoring of biological treatment processes.
• To overcome the limitations of traditional sensors, particularly regarding sensor lifetime and ease of use.
• To assess the sensor's performance in terms of measurement speed, calibration, and reproducibility.

Main Methods:

• Development of a BOD sensor utilizing immobilized mixed microbial cultures and a dissolved oxygen electrode.
• Implementation of a flow injection system for kinetic mode measurements.
• Testing with OECD synthetic wastewater and real wastewater samples from a food-processing factory.
• Evaluation of sensor response normalization and reproducibility across multiple sensors.

Main Results:

• The sensor achieved a measurement time of 25 seconds with a 4-8 minute recovery period.
• OECD synthetic wastewater proved more suitable for calibration than GGA solution.
• Sensor BOD measurements showed good agreement with standard BOD5 analysis.
• Excellent reproducibility was observed, with standard deviations below +/- 5.6% for single sensors and within +/- 15% for different sensors.

Conclusions:

• The developed BOD sensor is suitable for on-line monitoring of biological wastewater treatment.
• Its design allows for easy biomembrane replacement, making it ideal for short-term applications.
• The sensor offers reliable and reproducible measurements, overcoming drawbacks of previous technologies.