Replacement of chemical oxygen demand (COD) with total organic carbon (TOC) for monitoring wastewater treatment performance to minimize disposal of toxic analytical waste

Abstract

Chemical oxygen demand (COD) is widely used for wastewater monitoring, design, modeling and plant operational analysis. However this method results in the production of hazardous wastes including mercury and hexavalent chromium. The study examined the replacement of COD with total organic carbon (TOC) for general performance monitoring by comparing their relationship with influent and effluent samples from 11 wastewater treatment plants. Biochemical oxygen demand (BOD₅) was also included in the comparison as a control. The results show significant linear relationships between TOC, COD and BOD₅ in settled (influent) domestic and municipal wastewaters, but only between COD and TOC in treated effluents. The study concludes that TOC can be reliably used for the generic replacement of both COD (COD = 49.2 + 3.00*TOC) and BOD₅ (BOD₅= 23.7 + 1.68*TOC) in influent wastewaters but only for COD (COD = 7.25 + 2.99*TOC) in final effluents.

Keywords:

• TOC
• COD
• BOD₅
• prediction
• wastewater
• correlation
• performance monitoring

Acknowledgments

This research has been funded by Science Foundation Ireland under the Research Frontiers Programme (Grant number: 07/RFP.EEEOBF117). The authors are very grateful to the management and operators of the treatment plants from which sample material was collected.