高氯废水化学需氧量标准测定方法适用性分析

Applicability Analysis of Standard Determination Methods for Chemical Oxygen Demand(COD)of High-chlorine Wastewater

以不同氯离子浓度的水样为研究对象,选用重铬酸盐法、快速消解分光光度法、氯气校正法、碘化钾碱性高锰酸钾法4种不同分析方法同时进行测试,从精密度、准确度方面进行比对分析,以期得到不同水质最为合适的分析方法,确保检测结果能真实反映水体所受污染程度。实验结果表明,对于高氯低COD样品,在准确度和精密度方面,用碘化钾碱性高锰酸钾法可以得到稳定可靠的结果,其余3种标准方法随着氯离子浓度的增加出现方法不适用或偏离标准值的现象;对于高氯高COD样品,除碘化钾碱性高锰酸钾法不适用外,其余3种方法在准确度和精密度方面,均随着氯离子浓度的增加而下降,相对而言,氯气校正法所受影响相对小些;在实际应用中,碘化钾碱性高锰酸钾法准确度最高,氯气校正法尚可满足要求,重铬酸盐法和分光光度法受氯离子浓度和COD值匹配性的影响较大。因此,建议高氯低COD样品首选碘化钾碱性高锰酸钾法,其次选用氯气校正法,但由于目前我国水污染排放标准中允许排放浓度均以重铬酸盐法的测定结果为依据,所以建议国家尽快组织制订用碘化钾碱性高锰酸钾法测定工业废水COD的排放标准;实验结果表明:高氯高COD样品,采用重铬酸盐法较为适宜。

This paper aimed at selecting the most appropriate determination methods based on water quality so that the results obtained could exactly reflect the pollution degree of water bodies. For this purpose, four standard methods （i.e., the dichromate method, fast digestion-spectrophotometric method, chlorine emendation method and potassium iodide alkaline permanganate method） were applied to water sample analyses with various chloride concentrations. The comparative analyses of experimental data were conducted with regard to the degree of measurement precision and accuracy. For water samples with low COD and high chloride, the stable and reliable results could be obtained through the potassium iodide alkaline permanganate method, but the other three methods became not suitable as high variation occurred as the concentration of chloride ions increased. By contrast, the potassium iodide alkaline permanganate method was not suitable for high chloride samples with high COD. In fact, the degree of precision and accuracy of all the other three methods also decreased with the rise of concentration of chloride ions. By comparison among the remaining three methods, the chlorine emendation method was least affected by the change of chloride ion concentration. In practical application, the potassium iodide alkaline permanganate method had the highest accuracy among the four standard determination methods and the chlorine emendation method could meet the basic requirements, while the dichromate method and the fast digestion-spectrophotometric method were strongly affected by the concentration of chloride ions and the COD values of the sample. Therefore, for high chloride samples with low COD values, the potassium iodide alkaline permanganate method should be the first choice and the chlorine emendation method should be the second. However, since the maximum discharge concentration of the current discharge standard in China is based on the results of the dichromate method, we suggest that relevant authorities should set a new discharge standard using the potassium iodide alkaline permanganate method as soon as possible. According to our experimental results, it is preferable to apply the dichromate method to high chloride samples with high COD values.