LAR's BioMonitor is an online BOD analyzer for the determination of the total biochemical oxygen demand (BOD). The analyzers' functional principle is similar to a miniature biological waste water treatment plant. The waste water to be tested is mixed with the plant's own activated sludge and air and continuously passed through a multistage measurement cascade. Upon exiting the cascade, the residual oxygen is measured with an oxygen sensor. Due to the usage of the plant's own sludge, the BioMonitor delivers direct information on the treatment processes and thus, allows the highest applicability on the real process. In contrast to the commonly used BOD5 measurement, that needs 5 days and measures the carbonaceous-BOD only, LAR's BOD analyzer determines the Total-BOD of a sample within minutes. The total-BOD reflects the degradation of nitrogen as well as carbon compounds. The fast and representative BOD analysis allows operators to control their waste water treatment effectively. Moreover, due to nutrient dosage and/or aeration strategies enormous cost savings can be realized.