A Comparative Study Of On-Line And Laboratory TOC Analyzers For Analysis Of Municipal Wastewater

Wastewater treatment plans (WWTPs) use the Biological Oxygen Demand (BOD) test to measure oxygen consumed by decomposition of organic matter in secondary wastewater treatment processes. Total organic carbon (TOC) analysis provides a direct quantitative measurement of organic contamination in water and wastewater, whereas, BOD tests provide an indirect, empirical estimation of organic contamination.

In 40 CFR 133.104 the U.S. EPA allows wastewater treatment plants to substitute TOC analysis for BOD monitoring of oxygen-demanding substances. WWTPs seeking to substitute and report TOC values for BOD values must conduct a long-term correlation study and submit results to the regulatory body that issued the NPDES permit to their facility. Study data must be collected using USEPA-approved methods intended for NPDES permit compliance reporting.

Test methods for regulatory compliance reporting are currently based upon laboratory analysis. This includes both TOC and BOD. Once the correlation between BOD and TOC results is established, the TOC in wastewater streams can be accurately and quickly determined by an online TOC analyzer.

This application note presents comparative data obtained on influent and effluent wastewater samples using laboratory and on-line TOC analyzers employing the heated sodium persulfate oxidation technique in USEPA-approved methods 415.3 and SM 5310C.