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Nicholas Johnson

Doctoral Candidate
University of California, Los Angeles

Doctoral Candidate in the Department of Civil and Environmental Engineering at UCLA Scope of Work: My current work at UCLA consists of developing bioaugmented adsorbent systems and biofilms that can treat aqueous environmental contaminant mixtures including 1,4-dioxane, chlorinated solvents, and metals. Previously I worked on adsorption for the removal of hexavalent chromium and arsenic from water. Previous Education: B.S. and M.S. from UC Davis in Civil & Environmental Engineering



Treatment of 1,4-dioxane in Mixtures with Chlorinated Solvents and Metals Using Bacterial Biofilms

Biodegradation is a promising sustainable technology for the treatment of groundwater pollutants such as 1,4-dioxane. However, 1,4-dioxane is commonly found with co-contaminants, such as chlorinated solvents, and inorganics containing Cr(VI) and Cu(II), which can be deleterious for removal efficiency. We investigated bacterial biofilms for the removal of 1,4-dioxane in the presence of various mixtures of chlorinated solvents, Cr(VI), and Cu(II). Column studies were conducted using metabolic and cometabolic 1,4-dioxane-degrading bacteria Pseudonocardia dioxanivorans CB1190 and Mycobacterium austroafricanum JOB5. When attached to quartz sand and soil, CB1190 removed significantly more 1,4-dioxane in the presence of 1,1-dichloroethene and Cu(II) ions when compared with planktonic culture studies. JOB5-bioaugmented sand was able to remove both 1,4-dioxane and Cr(VI) at a wide range of concentrations. These findings are relevant to bacterial growth modes in the subsurface and some ex-situ reactor geometries and should be valuable in predicting biodegradation rates and inhibitory effects of contaminant mixtures.

Authors: Nicholas W. Johnson, Shu Zhang, Phillip Gedalanga, Linduo Zhao, Baohua Gu, Shaily Mahendra


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