An immobilized microbial consortium is formulated which comprises of a synergistic mixture of isolated bacteria namely, Aeromonas hydrophila, Pseudomonas aeruginosa, Yersinia enterocolitica, Serratia liquefaciens, Pseudomonas fluoresces, Enterobacter cloaca, Klebsiella oxytoca, Citrobacter amalonaticus and Enterobacter sakazaki. The formulated microbial consortium is immobilized on charged nylon membrane. The said immobilized microbial consortium is attached to dissolved oxygen probe for the preparation of electrode assembly. The prepared electrode assembly is used for rapid and reliable BOD estimation. The prepared electrode assembly is used for monitoring of BOD load of synthetic samples such as Glucose-Glutamic acid (GGA) used as a reference standard in BOD analysis and industrial effluents; covering a range from low to high biodegradable organic matter.