Abstract:

Consider the problem of the dissolved gas influences the measurement accuracy of the chemical oxygen demand (COD) based on the method of ozone combined with ultraviolet radiation (O₃/UV), we proposed estimation models of dissolved gas quantity for COD determination. In terms of the parameters collected and experimental results from the COD standard solution digestion with different concentrations, the estimation models of dissolved oxygen and carbon dioxide based on PLC-LSSVMs are established respectively. The outputs of the estimation models are used as compensation for the COD detection model. The results show that the estimation models have higher estimation accuracy than the model established by PLS or LSSVMs alone. The relative errors of the COD measured by O₃/UV method after the estimated dissolved gas amount is compensated and the national standard method is both less than 5%. This study is of great significance for improving the accuracy of COD detection by O₃/UV method.

Key words: chemical oxygen demand, carbon dioxide, PLS, LSSVMs, experimental verification, model, prediction

摘要：

针对臭氧协同紫外方法(O₃/UV)检测化学需氧量(COD)时存在溶解性气体影响测量精度的问题，提出了一种COD检测过程中气体溶解量的估计方法，用于对COD检测模型的补偿。采集不同浓度的COD标准水样在消解过程中的测量数据和实验分析数据，基于PLS-LSSVMs建立溶解氧量和溶解二氧化碳量的估计模型，将模型的输出作为COD检测模型的补偿项。实验结果表明，基于PLS-LSSVMs建立的模型比PLS或者LSSVMs单独建立的模型估计精度高。采用溶解气体量估计模型进行补偿后的O₃/UV法检测COD与国标法测量结果相对误差均小于5%。对提高O₃/UV法检测COD精度具有重要意义。

关键词: 化学需氧量, 二氧化碳, 偏最小二乘, 最小二乘支持向量机, 实验验证, 模型, 预测