Produced water discharges are monitored under the National Pollutant Discharge Elimination System (NPDES) programme, and one of its provisions requires that oil and grease concentration in the water be measured and reported to the EPA using EPA Method 413.1, a laboratory gravimeter method. Industry is interested first of all in how a future change in this method will impact discharges. In addition, industry has an interest in on-platform routine monitoring methods to help ensure compliance and to optimise operational efficiency.The current EPA Method 413.1, which is now specified in over 10000 different NPDES permits in 25 different classifications, uses Freon-113 (a chlorfluorocarbon) as the solvent. Concern with the role of chlorofluorocarb-ons in ozone depletion and global climate change has raised the need for an alternate solvent. The EPA published in 1994 a revised method for oil and grease measurement that uses n-hexane as the solvent (Method 1664).Both EPA and API have conducted studies to compare results obtained using the different solvents (Freon or n-hexane) in the gravimetric technique for EPA reporting as specified in Method 413.1 and 1664 respectively. Results from a joint EPA-API study which used streams from various offshore platforms, refineries, and marketing terminals will be presented and discussed.Results from an API project to value various analytical methods for measuring oil and grease content of produced water will also be discussed.Two areas will be presented:1. Method 1644 Performance Verification2. Detailed Evaluation of On-Platform Monitoring Techniques.
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