Biological transformations and removal of selenium in refinery wastewaters
- and others
The six petroleum refineries the San Francisco (CA) Bay Area are completing a cooperative study of potential treatment technologies to reduce selenium concentrations in their final effluents. Biological treatment was identified early in the selenium removal technology study as a potential treatment technology based on existing wastewater treatment at the Bay Area refineries and previous studies of biological selenium transformations in agricultural drain waters. The goal of this eight-month study was to evaluate biological selenium transformation and removal processes through field testing at the Shell Oil Company`s Martinez Manufacturing Complex (MMC). Refinery wastewater selenium speciation showed that selenocyanate is the predominant species in stripped sour water and that selenite and selenate are the predominant species after biological treatment. The field testing study focused on five selenium transformation pathways: oxidation, assimilative reduction, dissimilative reduction, biomethylation, and other detoxification processes. Aerobic suspended growth, anoxic/aerobic suspended growth, and anoxic fixed film biological treatment systems were investigated to evaluate enhanced selenium removal through modification of existing biotreaters or through addition of a new biological treatment unit process. The field testing, results showed that oxidation of selenocyante, assimilative reduction, oxidation of elemental selenium, and dissimilative reduction are predominant pathways for selenium transformation and removal. Oxidation of selenocyante to selenite occurs under aerobic conditions in well-operated refinery treatment systems. Assimilative reduction of selenite under aerobic conditions results in total selenium removal proportional to biomass production. Dissimilative reduction of selenite under anoxic conditions results in formation of elemental selenium.
- OSTI ID:
- 416872
- Report Number(s):
- CONF-951023-; TRN: 96:005001-0029
- Resource Relation:
- Conference: 68. annual conference and exposition of the Water Environment Federation, Miami Beach, FL (United States), 21-25 Oct 1995; Other Information: PBD: 1996; Related Information: Is Part Of WEFTEC `95: 68th annual conference & exposition; PB: 498 p.
- Country of Publication:
- United States
- Language:
- English
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