Online vs. Laboratory BOD Testing

While laboratory BOD₅ tests are standardized and widely used, they have limitations, including delayed results and potential for sample contamination. In contrast, online BOD monitoring systems provide immediate data, facilitating rapid response to changes in wastewater composition and enhancing overall treatment efficiency.

Role of Dissolved Oxygen in BOD

Dissolved oxygen (DO) is crucial for the aerobic decomposition of organic matter. BOD measurements reflect the oxygen demand of microorganisms during this process. Maintaining adequate DO levels is essential to prevent anaerobic conditions, which can lead to undesirable byproducts and odors.

TOC vs. BOD: Key Differences

Total Organic Carbon (TOC) and BOD both assess organic pollution but differ in scope and application:

• TOC: Measures the total amount of carbon in organic compounds, providing a quick assessment of organic content.

• BOD: Measures the amount of oxygen required for microbial decomposition of organic matter, indicating the potential impact on oxygen levels in receiving waters.

TOC analysis is faster but may not fully represent the biodegradable fraction of organic matter, whereas BOD provides insight into the biological effects on aquatic systems.

What is the significance of BOD in wastewater treatment?

BOD indicates the amount of organic pollution in water, helping assess the effectiveness of treatment processes and ensuring compliance with environmental regulations.

How does online BOD monitoring improve wastewater management?

Online monitoring provides real-time data, allowing for immediate adjustments to treatment processes, improving efficiency, and reducing the risk of regulatory violations.

What are the advantages of TOC analysis over BOD testing?

TOC analysis offers faster results and measures all organic carbon present, but it doesn’t differentiate between biodegra

Online measurement of BOD Measurement using cascades and O2-Sensor

Similar to the working principle of a biological treatment plant, in this WWTP simulation, the sewage is mixed with activated sludge under aeration and continuously led through the drain cascade. On leaving the reactor cascade the remaining oxygen will be determined with the O2 sensor, whereby the volumes of wastewater, activated sludge and air are specifically defined and monitored. With this method it is important to use the plants-own biomass to simulate the real biology of the particular wastewater treatment plant. Hence, the measurement results have specific relevance relating to the WWTP and its unique properties.

Our LAR™ BioMonitor™ regulates not only the optimal control of the oxygen input to the activated sludge reactors of the wastewater treatment facilities, but monitors the incoming contaminations of their influent. This enables the operator to even out possible peak pollutions, thereby maintaining aeration at a regulated level, as usually it is these peak pollutions which cause additional aeration, which in turn is energy consuming and expensive.

BOD determination by O2-Electrode

Common BOD analyzers allow a determination within 10 to 30 minutes, whereby short-term measurements of the oxygen consumption through O2 electrodes dominate. However, as oxygen is hardly soluble in water, very often low measurement results are found, which then need to be extrapolated. Essentially, this method really only is suitable in determining very easily degradable substances.

Activated Sludge Respiration (ASR) and Sludge Activity

The biomass or sludge of a wastewater treatment plant not only needs oxygen to decompose substances, but also for the endogenic respiration, the so-called activated sludge respiration or sludge activity. This oxygen turnover of the bacteria is measured in mg/l*min (volume/time).

This amount of the total oxygen consumption is measured separately online in the BioMonitor – by use of the reference cascade, through which only the sludge and air is led. The decrease of oxygen concentration of the inlet air corresponds to the ASR.

On comparing the results of the sludge activity to the results at the cascade’s drain gives the conclusion as to the anaerobic decomposability of the biomass and even toxins may be highlighted.