INFORMATION
- Contaminant: Selenium
- Matrix: Industrial Wastewater
- Reagent(s): SeleniumZero™
- Site location: Refineries, Western United States
The problem: Effluent from sour water strippers and other wastewater streams at oil refineries are often impacted with selenium due to the presence of selenium in sour crude oil that is carried through the refining process. Selenium concentrations in these wastewaters can reach over 1 milligram per liter (mg/L) while the national maximum contaminant level is 0.05 mg/L. Existing removal methods are costly, difficult to operate, and/or require a large footprint. The client wanted to know whether SeleniumZero™ could effectively remove selenium from these waste streams.
How PRIMA helped: PRIMA performed screening-level column tests to evaluate the ability SeleniumZero™, a form of Sulfur Modified Iron (SMI™), to remove selenium from various waste streams found within several refineries. In some cases, the water was pre-treated to adjust pH or remove oil. Results confirmed that SeleniumZero™ could reduce selenium concentrations, in some cases to below 5 mg/L. Based on the results of the testing, field pilot tests were conducted at two sites. At one site, the field pilot ran for 6 months and decreased selenium concentrations from 0.6-1.8 mg/L in the influent to less than 0.002 mg/L using no pre-treatment and 10 minute empty bed contact time (EBCT); the resulting selenium capacity was greater than 12 mg Se/g SeleniumZero®. At the second site, the test ran for 30 days and decreased selenium from 0.64-1.2 mg/L in the influent to less than 0.004 mg/L, also with no pre-treatment and 10 minute EBCT.
For more information about this project, see our presentation “Removal of Selenium from Refinery Wastewater using Sulfur Modified Iron (SMI)” on our Resources – Webinars and Presentations page.