API Publ 4717:2002 pdf download.Predictors of Water-soluble Organics (WS0s) in Produced Water— A Literature Review
The U.S. Environmental Protection Agency (EPA) or a state agency designated by EPA issues region wide (general) or site- specific National Pollutant Discharge Elimination System (NPDES) permits to regulate discharges of treated produced water to State and Federal offshore waters of the United States. Produced water intended for ocean discharge is first treated in various oil/water separation devices to remove dispersed oil droplets. Current general permits for Federal offshore waters of the Gulf of Mexico have limits for total oil and grease in produced water of 42 mg/L (ppm) daily maximum and 29 mg/L monthly average. EPA requires oil and grease concentrations in produced water to be monitored by EPA Method 413.1 or 1664 (EPA, 1983, 1995). Both methods are gravimetric. Nonpolar and slightly polar organic matter in produced water is extracted with Freon ® (Method 413.1) or n-hexane (Method 1664). In Method 1664, the analyst has the option to treat the hexane extract with silica gel to remove polar interfering compounds. The extract is dried and weighed to derive a concentration of total extractable organic matter (total oil and grease). Although the oil and grease methods are inexpensive and easy to perform, there are two technical problems that may have implications for the regulation of discharges of produced water to offshore marine waters. First, low-molecular-weight, volatile alkane and aromatic hydrocarbon (BTEX) analytes are lost by evaporation during sample processing. Second, many non-hydrocarbon organics, and possibly some metals, are extracted by the solvent and measured as part of the total oil and grease in produced water, even after extract cleanup with silica gel.
Loss of volatile hydrocarbons is not a concern, since these chemicals are not persistent in surface waters and so are unlikely to contribute to the toxicity of produced water plumes to marine animals (Neff, 1997). In a regulatory context, the second problem is more of an issue. The analytical methods may grossly overestimate the concentration of petroleum hydrocarbons in produced water if the concentration of non-hydrocarbon organic matter in the produced water is high (Brown et al., 1990, 1992; Otto and Arnold, 1996). Typical produced water from production platforms in U.S. Gulf of Mexico may contain 50 to more than 500 mg/L (ppm) 1 total organic carbon (TOC), of which approximately 8.5 to 16% is petroleum hydrocarbons (Neff et al., 1989). The remaining TOC is a mixture of non-hydrocarbon organics, including water-soluble production treatment chemicals, phenols, organic acids, alcohols, and ketones. These non-hydrocarbon organic fractions of produced water have not been well characterized. Some information is available about water-soluble production treatment chemicals, organic acids, and phenols (Neff, 1997).
API Publ 4717:2002 pdf download
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