H_2O_2对COD测定的干扰及消除研究

Study on the interference of H_2O_2 on COD test and the correction method

COD是表征水体有机物污染状况的重要参数,而实际水样成分复杂往往对COD测定产生干扰,其中H2O2尤为明显。通过实验分析H2O2对COD干扰状况并提出消除干扰的措施。研究表明,H2O2作为还原剂使COD测定值高于实际值;H2O2浓度与COD之间呈现线性关系,R2为0.999 7,线性方程为y=0.466 4x+0.249 5,1mg的H2O2能引起0.466 4mg的COD变化。在低、高2种浓度的COD标准溶液体系中,线性方程计算的ΔCOD1(即H2O2引起的COD变化值)与ΔCOD2(COD测定值与原水COD的差值)差值为原水COD的1.28%～11.80%、0.16%～5.95%;在低、高2种浓度的工业废水体系中,线性方程计算的ΔCOD1与ΔCOD2差值分别为0.1～5.9、32.7～75.6mg/L,为原水COD的1.28%～14.00%、2.35%～5.44%;在生活污水体系中,线性方程计算的ΔCOD1与ΔCOD2差值为6.8～30.3mg/L,为原水COD的2.98%～13.40%。通过线性方程,较好地反映出实际的COD差异,可以消除H2O2对COD测定的干扰。该方法简单准确,能够较好地反映实际水样的COD情况。

COD is a widely used indicator for identifying the characteristics of wastewater. However, the com-plicated component, especially H2O2, in real wastewater could interference the COD detection. The interference of H2O2 on COD testing value and the correction method were investigated in this paper. Results showed that H2O2 as a reducing agent could increase the COD testing values. H2O2 concentration was liner correlated with COD testing values. The linear equation was y=0. 466 4x＋0. 249 5 （R^2 =0. 999 7）, means 1 mg of H2O2 could cause 0. 466 4 mg of COD alteration. The variation of COD caused by H2O2 was calculated by linear equations （ACODI） and determina-tion （ACOD2） respectively; the D-value of ACOD1 and ACOD2 were 1. 28%-11. 80%, 0. 16%-5. 95% of original COD in low and high concentrate standard COD solutions. The D-value of △COD1 and △COD2 were 0. 1-5.9, 32.7-75.6 mg/L in industrial waste water of low and high concentration system; the differences were 1. 28%-14.00%, 2.35%-5.44% of original COD;The D-value of ACODI and ACOD2 was 6.8-30.3 mg/L in sewage water system; the differences was 2.98%-13.40% of original COD. The correlation equation could better reflect the variation of COD, it could be used to correct the interference caused by H2O2. The method is simple and accurate, and could reflect the COD values in the real wastewater sample.