Experimental Study of Emitted Volatile Organic Pollutants from Wastewater Treatment Ponds in Oil Refineries

Wastewater treatment unit in an oil refinery is one of the main emission sources of volatile organic compounds and exposure to these pollutants has major negative impacts on refinery staff and residents of adjacent areas. The purpose of this study is to investigate the concentration of volatile organic compounds in refinery effluents and to estimate the emission of these compounds into the air. Concentration and pollution load of volatile organic compounds in operating units and basins of treatment unit wastewater were analyzed using gas chromatography and emission estimation of them was done using the Rank 2 and Rank 3 of the US Environmental Protection Agency. The pollution received by wastewater plant was 1095 ton/y of five components: benzene, toluene, xylene, ethyl benzene and hexane, while 5379 ton/y for the eleven pollutants including previous five components plus pentane, heptane, methyl cyclohexane, 1-2-4 tri-methylbenzene, 1-3-5 tri-methylbenzene and dodecane. Based on refinery feed, for each ton of crude oil processed, 187 g of the total 5 compounds and 692 g of 11 compounds are produced from operational units; but only 78% of the 11 compounds and 60% of the 5 compounds could reach the treatment unit, which indicates the emission of pollutants in the transfer path. Overall, for each ton of processed crude oil, 48.5 g of 5 compounds and 241.6 g of 11 compounds from effluent treatment ponds are emitted to the atmosphere. Identifying the sources of volatile organic compounds production is one of the ways to reduce the pollution load entering the treatment unit and thus reduces the emission from the refinery. Based on these results, refineries could apply proper strategies for emission decrease. This research has been done for a refinery with ten megatons capacity per year and medium complexity, which could be used by any analogous refinery in the world.