The use of treatment wetlands for petroleum industry effluents

Although the use of treatment wetlands is well established for wastewater categories such as municipal waste, stormwater, and acid mine drainage water, their use in treating a variety of industrial and agricultural wastewaters is less well developed. Several large-scale wetland projects currently exist at oil refineries, and numerous pilot studies of constructed treatment wetlands have been conducted at terminals, gas and oil extraction and pumping stations, and refineries. This paper reviews treatment wetland performance for chemical oxygen demand, biochemical oxygen demand, trace organics, metals, toxicity, total suspended solids, nitrogen, and phosphorus. All of these contaminants can be reliably removed from wastewater by treatment wetlands. Pollutant removal is highly dependent on hydraulic loading and influent concentration and to a lesser extent on internal plant communities, water depth, and hydraulic efficiency. In most cases, data from petroleum industry wetland studies indicate that treatment wetlands are equally or more effective at removing pollutants from petroleum industry wastewaters than from other types of wastewater. Until industry-specific data are more complete, this finding can be used along with published rate constants from other wastewater categories to provide conservative estimates for sizing petroleum industry treatment wetlands.