TOC, COD & SAC Analyzers

TOC, COD & SAC Analyzers

TOC, COD, and SAC analyzers measure “sum parameters” used to quantify organic load in water and wastewater systems. Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) represent organic content and oxidizable load, while Spectral Absorption Coefficient (SAC) provides an optical surrogate related to organic content in many natural and municipal waters.

These measurements support regulatory compliance by verifying discharge quality at the outlet and improving operational resilience by monitoring the inlet for load peaks. Inlet monitoring enables earlier interventions to protect biological processes and prevent permit exceedances, while outlet monitoring provides confirmatory documentation. Sum-parameter measurement is also used to assess treatment capacity and, in some contexts, to support fair billing of industrial dischargers consistent with “polluter pays” concepts.

Multiple technologies are applied depending on the goal. TOC and COD analyzers are positioned for “true” TOC/COD values when precision is required, while SAC probes are often selected for surface water and river monitoring and for cost-efficient COD/TOC-equivalent tracking in municipal wastewater when significant fluctuations are not expected. COD measurement may use colorimetric principles (including dichromate-based approaches), and TOC determination can employ methods such as UV digestion with conductivity-based detection, depending on the analyzer design.

Applications include municipal influent and effluent, industrial wastewater discharge, surface water and river monitoring, and process water management where organic contamination must be identified quickly. Data is used for alarm strategies, diversion decisions (e.g., directing high loads to retention), and performance optimization of treatment steps such as aeration and chemical addition.

Implementation considerations include selecting the appropriate sum parameter and technology for the variability of the matrix, providing appropriate sample conditioning, and managing reagents where colorimetric techniques are used. When SAC is used as an equivalent measurement, correlation and validation against lab TOC/COD remain key to maintaining confidence in reported values and control decisions.

George E. Booth Co., an exclusive authorized representative of sales and service for Endress+Hauser.