Removal of Selenium from Difficult-to-treat Wastewaters Using an Innovative Reductive-adsorptive Media.pdf

Patrick McKeown, ECT2
Madan Tandukar, ECT2
Steve Woodard, ECT2
Mike Nickelsen, ECT2

Description

Removal of Selenium from Difficult-to-treat Wastewaters Using an Innovative Reductive-adsorptive Media Authors Mr. Patrick McKeown - United States - ECT2 Dr. Madan Tandukar - United States - ECT2 Dr. Steve Woodard - United States - ECT2 Mr. Mike Nickelsen - United States - ECT2 Abstract Selenium is one of the more difficult-to-treat emerged contaminants, and is mostly prevalent in mining and power wastewater. In water and wastewater, selenium generally exists as soluble oxyanions, selenite (SeO32−) and selenate (SeO42−). Out of these, selenate is the more mobile and prevalent species, which also is more difficult to remove. With increasing focus on water quality, the EPA is moving towards tighter selenium discharge limits to as low as 3 µg/L (ppb). This abstract presents two case studies of selenium removal from mining wastewater and coal combustion residue (CCR) effluent using an innovative media. In the mining and CCR wastewaters, selenium is one of the key contaminants that is naturally occurring in soil, groundwater and coal. The new media developed for selenium removal is an engineered and surface-modified iron-based media, which has high surface area, reactivity and contaminant capacity. The media functions by reducing selenate/selenite to elemental selenium, which is then strongly adsorbed on the media surface. Study1: influent mining water had 30 ± 12.6 µg/L of selenium (all selenate) and high concentrations of co-contaminants such as, aluminum, silica, sulfate and phosphate. The pH of the raw water was approximately 2.7. Over 59 days of run time, the system consistently removed selenium to below the target limit of 3 µg/L. The pilot also removed the remaining aluminum in the wastewater. This is an added benefit because aluminum is one of the contaminants that the local government is planning to regulate in the future. Study2: CCR effluent, which contained 374 ± 38.2 µg/L of selenium along with molybdenum, arsenic, boron, sulfate, nitrate. The treatment target for selenium was 12 µg/L. The pilot unit was operated continuously for 30 days with selenium consistently removed below 12 µg/L Additionally, the pilot also consistently removed molybdenum, from 3,000 µg/L to almost non-detect levels.

 
May 14th, 1:00 PM May 14th, 1:30 PM

Removal of Selenium from Difficult-to-treat Wastewaters Using an Innovative Reductive-adsorptive Media.pdf

Grand Rapids, Michigan

Removal of Selenium from Difficult-to-treat Wastewaters Using an Innovative Reductive-adsorptive Media Authors Mr. Patrick McKeown - United States - ECT2 Dr. Madan Tandukar - United States - ECT2 Dr. Steve Woodard - United States - ECT2 Mr. Mike Nickelsen - United States - ECT2 Abstract Selenium is one of the more difficult-to-treat emerged contaminants, and is mostly prevalent in mining and power wastewater. In water and wastewater, selenium generally exists as soluble oxyanions, selenite (SeO32−) and selenate (SeO42−). Out of these, selenate is the more mobile and prevalent species, which also is more difficult to remove. With increasing focus on water quality, the EPA is moving towards tighter selenium discharge limits to as low as 3 µg/L (ppb). This abstract presents two case studies of selenium removal from mining wastewater and coal combustion residue (CCR) effluent using an innovative media. In the mining and CCR wastewaters, selenium is one of the key contaminants that is naturally occurring in soil, groundwater and coal. The new media developed for selenium removal is an engineered and surface-modified iron-based media, which has high surface area, reactivity and contaminant capacity. The media functions by reducing selenate/selenite to elemental selenium, which is then strongly adsorbed on the media surface. Study1: influent mining water had 30 ± 12.6 µg/L of selenium (all selenate) and high concentrations of co-contaminants such as, aluminum, silica, sulfate and phosphate. The pH of the raw water was approximately 2.7. Over 59 days of run time, the system consistently removed selenium to below the target limit of 3 µg/L. The pilot also removed the remaining aluminum in the wastewater. This is an added benefit because aluminum is one of the contaminants that the local government is planning to regulate in the future. Study2: CCR effluent, which contained 374 ± 38.2 µg/L of selenium along with molybdenum, arsenic, boron, sulfate, nitrate. The treatment target for selenium was 12 µg/L. The pilot unit was operated continuously for 30 days with selenium consistently removed below 12 µg/L Additionally, the pilot also consistently removed molybdenum, from 3,000 µg/L to almost non-detect levels.