The BOD (biological or biochemical oxygen demand) value indicates the amount of oxygen which is needed for the biological degradation of organic substances in water in mg O2/ l.  Generally, the biological oxygen demand serves as a sum parameter for the assessment of pollution of sewage.

BOD5 and Total BOD

Unlike the special factor BOD5, which according to the standardized lab method the measurement of the biochemical oxygen demand excluding the nitrification part follows after 5 days, the total BOD includes this bacterial oxidation of ammonia to nitrate which allows a continuous online monitoring.

The nitrification is an important part of the sewage treatment processes and should be taken into consideration for optimal control of wastewater treatment plants. Hence, determination of BOD5 is hardly suitable for optimum control of wastewater treatment facilities.

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.