不同浓度范围废水COD检测条件探讨

Detection conditions of the COD of wastewater with different concentrations

针对一些废水在处理过程中COD范围差异大，COD测定准确度、精密度低的问题。考察了不同浓度范围影响COD测定的关键性因素，结果显示：在440、600nm处，Cr（Ⅵ）浓度不适会引起COD测定准确度、精密度降低。采用c（1／6KzCr20，）为0．02、0．05、0．5mol／L的重铬酸钾溶液，分别对COD为0-50、50～150、150—1500ms／L的溶液作标线，标线的线性回归系数R^2均〉0．999，平行水样相对偏差为1．19％～2．61％，加标回收率为95．3％-104．4％。

Aiming at the problems, such as great COD differences of wastewater, and low accuracy and precision of their determinations, the effects of different concentration ranges on the accuracy and precision of COD determination have been studied. The results show that when the wavelength is at 440,600 nm, the inappropriate concentration of Cr（ Ⅵ ） can lower the accuracy and precision. When c （1/6 K2Cr2O7） =0.02,0.05,0.5 mol/L solutions are used respectively for making standard curves on 0-50,50-150,150-1 500 mg/L of COD respectively. For the standard curves with the concentrations, the linear regression coefficients R2 of COD with absorbency are greater than 0.999, relative deviation of parallel sample test is 1.19%-2.61% and the recovery rate between 95.3%-104.4%.