MEASUREMENT OF BOD BY INITIAL RATE OF RESPONSE OF A MICROBIAL SENSOR

A biochemical oxygen demand (BOD) sensor, prepared from a mixed microbial culture of Bacillus subtilis and Bacillus licheniformis 7B, is calibrated by determining the initial rate of its response in various standard glucose/glutamic acid BOD-check solutions. The initial rate varies linearly with the five-day BOD value up to a maximum of 80 mg/l. The BOD values of a number of wastewater samples from various sources are determined by this method. They compare favourably with the values obtained by the conventional method. With this technique, the time required for each measurement is about 15-30 s with a baseline recovery time of 4 min between measurements. This is considerably faster than the steady-state method, which requires 15-20 min per measurement and a baseline recovery time of 1-4 h. The bio-oxidation activity of the microbial system depends significantly on the types of organic solutes present in the water and can be enhanced by pre-conditioning the microbes in a culture medium doped with the organic solute.