Determination of COD of High Chloride Wastewater by Subtraction Method

Significant errors occur when COD value of high chloride wastewater is determined by the national standard,and the error is increased with the increasing of chloride concentration.Therefore,the subtraction method was used for determination of COD of high chloride wastewaters with high COD and low COD.The results show that the error is low than 5% when the chloride concentrations in high and low COD wastewater are less than 12 500 mg/L and 8 000 mg/L respectively,meeting the permissible range of the national standard.Significant errors occur when the chloride concentration exceeds the above-mentioned values.