BOD sensor using magnetic activated sludge

Abstract A biochemical oxygen demand (BOD) sensor, consisting of a Pb(−)|NaOH|Pt|O 2 (+) electric cell, was constructed. The sensor is basically one application of a dissolved oxygen electrode. Magnetic sludge was prepared by mixing magnetite powder with acclimated activated sludge. A magnetic cathode, comprised of a Sm-Co magnet plated with platinum, was covered by a Teflon membrane; magnetic sludge was simply layered on the membrane by magnetic attraction. The magnetic sludge decomposed the BOD component with consumption of oxygen. The BOD could therefore be determined by measuring the electric current produced by the BOD sensor. This current was then converted into the concentration change of oxygen transported through the Teflon membrane from the magnetic sludge layer.