Elimination of sulfur(IV) interference in five-day biochemical oxygen demand determinations

Abstract

Sulfur dioxide is a reduced species [S^IV] that may exert a positive interference in carbonaceous biochemical oxygen demand (BOD) determination when present in municipal and industrial waste waters. The addition of 0.1 mg dm^–3 of Co²⁺ after pH adjustment to 7.8, followed by agitation for 16 h at 4 °C, resulted in oxidation of the S^IV. The procedure was used on waste-water samples containing 500 mg dm^–3 of S^IV, which were subsequently analysed for five-day BOD (BOD₅). The results were not significantly different from data obtained for control samples. The elimination procedure provided a statistically valid means of removing S^IV interference in BOD determination. The method may provide an efficient procedure for the determination of the carbonaceous BOD of water containing S^IV.