Development of highly sensitive BOD sensor and its evaluation using preozonation

A highly sensitive microbial sensor for biochemical oxygen demand (BOD) is described based on preozonation of refractory organic compounds in river waters. The hydroxyl radical generated by ozone decomposition was used as oxidant to split up organic compounds. Artificial wastewater (AWW) solutions were employed as standard solutions for the calibrations of the BOD sensor. The degree of degradation of organic compounds after ozonation of humic acid, lignin, tannic acid, gum arabic and surfactants were investigated as total organic carbon (TOC) reduction rates. The ozonation of AWW solutions was carried out by 42.4 g N-1 m(-3) ozone for 3 min at pH 7.0. TOC reduction rates of humic acid and tannic acid were 22% and 18%, respectively, but gum arabic showed extremely low values. The sensor response to 1 mg L-1 BOD after ozonation was twice than that before ozonation. A typical response time of the BOD sensor was ca. 5 min, and the 3 sigma lower detection limit was 0.2 mg l(-1) BOD. BOD values estimated by the biosensor correlated well with those determined by the conventional BOD5 method. (C) 1999 Elsevier Science B.V. All rights reserved.