1,4Dioxane and PAH removal with Ozone Peroxide Advanced Oxidation Process

Minnesota Pollution Control Agency (MPCA) contracted with AECOM to design full-scale potable water treatment for volatile organic compound (VOCs), 1,4 Dioxane, and poly aromatic hydrocarbon (PAH) removal at two potable wells for a Minneapolis metro area water system. AECOM completed testing to confirm the treatment processes selected for the full-scale design. Pilot and bench scale testing included spiking 1,4 Dioxane and PAHs, oxidation with chlorine, filtration, air stripping, and advanced oxidation process (AOP). Two AOP treatment systems were originally reviewed: 1.ultraviolet light and hydrogen peroxide AOP and 2. ozone and hydrogen peroxide AOP. Final testing focused on ozone and hydrogen peroxide AOP. The proposed system was designed to remove iron, manganese, radium, volatile organic compounds (VOCs), PAHs, and 1,4 dioxane. Ammonia and nitrate were reviewed due to the presence of ammonia in the raw water.

Existing granular media filtration is utilized for iron and radium removal. Manganese removal is incomplete due to competition with ammonia for oxidant within the system.

VOC removal including cis-1,2-dichloroethene (DCE), Trans-1,2- DCE, Dichlorofluroomethane, Trichloroethene (TCE), and vinyl chloride was successful with the air stripping process.

The advanced oxidation process testing resulted in 99% reduction in 1,4 dioxane from 23 ppb to 0.13 ppb with ozone and hydrogen peroxide AOP, meeting the state treatment requirements. Various doses of ozone and hydrogen peroxide were used with varying results in the pilot testing process and will be discussed. PAH reduction was also reviewed with 94% reduction in the preliminary iron and manganese filtration process. Additional review is currently underway for PAH reduction in the AOP process and results will be available at the time of the conference.

This presentation summarizes testing objectives, layout, and results from initial bench scale testing, pilot testing at the well sites, and additional bench scale testing for chemical dose optimization.