Comparison of COD and TOC in influents and effluents of six industrial wastewater treatment plants in Korea

Objectives : This study compared the CODMn and TOC concentrations of the influent and effluent from six industrial wastewater treatment plants (WWTPs) and the wastewater from manufacturing facilities in the industrial complexes, and to understand the correlation between the two indicators.Methods : The sampling campaigns were performed four times at each WWTP for both influent and effluent. Water quality surveys were also conducted to assess the characteristics of organic matter in the wastewater from the manufacturing facilities. A total of 272 facilities including manufacturing, non-manufacturing, and miscellaneous manufacturing units were surveyed. Results and Discussion : The CODMn/TOC ratios of the influent and the effluent of the WWTPs ranged from 0.78 to 1.79 (average 1.19) and 0.94 to 1.58 (average 1.20), respectively. The ratio of CODMn/TOC ratio in the wastewater from the manufacturing facilities was 1.06~1.22 (average 1.12). Industries with high R2 values for the CODMn/TOC ratios included rubber and plastics manufacturing (CODMn/TOC = 1.17), nonferrous metals manufacturing (CODMn/TOC = 0.94), medical materials and pharmaceutical manufacturing (CODMn/TOC = 0.98), and chemicals manufacturing (CODMn/TOC = 1.27).Conclusion : CODMn/TOC ratios of the influent and effluent of the six plants and the wastewater from manufacturing facilities varied in different ranges for each WWTP, with an average value of 1.12. The results of this study can be used as basic information to manage the effluent water quality of the WWTPs.