1. Introduction
Petroleum extraction in offshore units demands high volumes of water for the secondary recovery of crude oil. Such water is employed to keep the pressure inside the reservoir and allow the recovery of additional amounts of petroleum. As consequence, large amounts of aqueous effluents are generated due to the mixture of the water injected into the well (injected water) and the water already present into the reservoir (formation water). This water is called produced water and its composition is very complex[1]. Depending on their origin, produced waters can contain a wide variety of chemical substances such as organic salts, aliphatic hydrocarbons, PAHs, heavy metals and, occa-sionally, radioactive materials usually called NORM (Normally Occurred Radioactive Materials). A noticeable characteristic of the most produced waters generated in offshore operations is their high salinity [2]. In general, the amount of water extracted in an offshore operation is much higher than the amount of oil. This amount depends on the dimensions of the reservoir, the explored area and the capacity of the exploration unity. The literature reports that the volume of produced water extracted can vary from 2000 to 40,000m3 per day[3]. This is a great problem in the petroleum industry because this water must be characterized and treated before discharging. This operation includes metal evaluation in the produced waters and chromium can be considered an important analyte due to its high toxicity when found in the hexavalent state.
1. Introduction
Petroleum extraction in offshore units demands high volumes of water for the secondary recovery of crude oil. Such water is employed to keep the pressure inside the reservoir and allow the recovery of additional amounts of petroleum. As consequence, large amounts of aqueous effluents are generated due to the mixture of the water injected into the well (injected water) and the water already present into the reservoir (formation water). This water is called produced water and its composition is very complex[1]. Depending on their origin, produced waters can contain a wide variety of chemical substances such as organic salts, aliphatic hydrocarbons, PAHs, heavy metals and, occa-sionally, radioactive materials usually called NORM (Normally Occurred Radioactive Materials). A noticeable characteristic of the most produced waters generated in offshore operations is their high salinity [2]. In general, the amount of water extracted in an offshore operation is much higher than the amount of oil. This amount depends on the dimensions of the reservoir, the explored area and the capacity of the exploration unity. The literature reports that the volume of produced water extracted can vary from 2000 to 40,000m3 per day[3]. This is a great problem in the petroleum industry because this water must be characterized and treated before discharging. This operation includes metal evaluation in the produced waters and chromium can be considered an important analyte due to its high toxicity when found in the hexavalent state.
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