Background: PETROLEUM WASTEWATER TREATMENT
Crude oil development and refineries generate a large amount of wastewater that has both process and non-process origins. Depending on the type of crude oil, composition of condensate and treatment processes, the characteristics of refinery wastewater vary according to a complex pattern. The design and operation of modern refinery wastewater treatment plants are challenging and are essentially technology driven. In order to process this wastewater, the sources of wastewater pollutants need to be identified to specific sources and operations, and suitable treatment technologies selected.
The quantity of wastewaters generated and their characteristics depend on the process configuration. As a general guide, approximately 3.5–5 cubic meters (m3) of wastewater per ton of crude are generated when cooling water is recycled.
Refineries generate polluted wastewaters, containing biochemical oxygen demand (BOD) and chemical oxygen demand (COD) levels of approximately 150–250 milligrams per liter (mg/l) and 300–600 mg/l, respectively; phenol levels of 20–200 mg/l; oil levels of 100–300 mg/l in desalter water and up to 5,000 mg/l in tank bottoms; benzene levels of 1–100 mg/l; benzo(a)pyrene levels of less than 1 to 100 mg/l; heavy metals levels of 0.1–100 mg/l for chrome and 0.2–10 mg/l for lead; and other pollutants.
Refineries also generate solid wastes and sludges (ranging from 3 to 5 kg per ton of crude processed), 80% of which may be considered hazardous because of the presence of toxic organics and heavy metals.
Currently at the majority of refineries, wastewater treated stream with presence of polyaromatic compounds, phenols and cobalt diluted by sea water and discharged into the sea or at some collection pits. The dilution does not degrade or eliminate these, thus making a strong case for the design and implementation of further treatment processes that should include biological reactors.
Refinery Wastewate Profile
The petroleum refining industry converts crude oil into more than 2500 refined products, including liquefied petroleum gas, gasoline, kerosene, aviation fuel, diesel fuel, fuel oils, lubricating oils, and feedstocks for the petrochemical industry. Typically, petroleum refining activities start with receipt of crude oil for storage at the refinery, include all petroleum handling and refining operations, and they terminate with storage prior to shipping the refined products from the refinery.
The petroleum refining industry employs a wide variety of physical and chemical treatment processes. A refinery processing flow scheme is largely determined by the composition of the crude oil feedstock and the chosen final petroleum products.
Large volumes of water are employed in refining processes, especially for cooling systems, distillation, hydrotreating, and desalting. Tank drains, equipment flushing, surface water runoff and sanitary wastewaters are also generated. It is therefore clear that refinery wastewater can be broadly categorized as process or non-process wastewater. In most modern refineries, these different wastewaters are channeled in separate sewer systems. At least two different independent sewers exist in most petroleum refineries: one that handles storm water and surface runoff and another that handles all process water and water produced from utilities units.
Solution: In order, to be able to reuse the treated wastewater, the dissolved oils, hydrocarbons and other constituents that sum up to the COD level must be removed. Biological treatment of refinery wastewater has proven to be the most economical and reliable tool after preliminary oil/water separation.
Among hydrocarbons present in refinery wastewater, phenol is one of the main dissolved components and it is also one of the toughest hydrocarbons to degrade biologically. We offer proprietary mix of bacterium that is proven to metabolize these contaminants.
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