13種のCOD値の関係と意義および塩素イオンの影響について

抄録

COD values of the standard substances and effluent treated human excrement were determined by 13 methods and the influence of Cl^- on the COD values was investegated. The results are as follows ; 1. When KMnO₄ was used as an oxidant (KMnO₄ method), COD values of standard substances were zero or very low comparing with the values obtained by methods using K₂Cr₂O₇ as an oxidant (K₂Cr₂O₇ method). Low COD value was also obtained on the effluent of treated human excrement by KMnO₄ method. Therefore, the COD value by KMnO₄ method is meaningless as an indicater of sewage pollution. 2. By K₂Cr₂O₇ method, especially with Ag₂SO₄ as a catalyst, high COD values were obtained for almost every standard substances and effluent of treated human excrement. In this case, COD values were also obtained by the inorganic substances such as NH₃ and Cl^-. 3. KMnO₄ method was slightly affected by Cl^-, while K₂Cr₂O₇ method was greatly influenced by Cl^-. The influence of Cl^- in K₂Cr₂O₇ method can be eliminated by adding HgSO₄ to the sample.