Effect Of Heterogeneity On Bacterial Transport And Deposition

Author : Huixin Zhang
Publisher :
ISBN 13 :
Total Pages : 220 pages
Book Rating : 4.:/5 (956 download)

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Download or read book Coupled Effects on the Transport and Deposition of Biocolloidal Particles in Saturated Porous Media written by Huixin Zhang and published by . This book was released on 2016 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transport and deposition of biocolloidal particles in porous media is a crucial phenomenon in understanding environmental challenges from pathogen contamination to bioremediation of soil and water. The fate and transport of biocolloidal particles in porous media is influenced by many factors ranging from the bulk solution condition (e.g. ionic strength and oxygen tension), microbial particle's surface property (e.g. surface charge and extracellular polymeric substances (EPS)) to porous media property (e.g. surface charge). This dissertation is focused on exploring the role anaerobic conditions have on microbial cell transport in packed bed columns and the mechanisms involved in the transport process. In addition, this dissertation evaluated the filtration of a recently developed surrogate for pathogenic Cryptosporidium and elucidated the mechanisms affecting its removal. The body of work was constructed in three individual parts. In the first part, experiments were performed in glass bead packed bed columns under strictly anaerobic conditions to examine the effects of solution ionic strength (1, 10 and 100 mM) on the transport of three microbial species (Dehalococcoides, Geobacter, and Methanomethylovorans) in an enriched anaerobic trichloroethene (TCE) dechlorinating mixed culture. Experimental results interestingly indicated that regardless of the microorganisms' distinct surface properties, they showed similar travel ability with normalized breakthrough concentrations (C/C0) of 0.95, 0.84, and 0.56 at 1, 10 and 100 mM, respectively. The microorganisms also exhibited almost equal sensitivity to solution ionic strength changes, possibly due to interactions and the heterogeneity among different microbial species in the culture. When using this culture for in situ bioremediation of TCE contaminated sites, success can be readily achieved when the microbial species in the culture travel in a similar fashion. In the second part, experiments were performed in glass bead packed bed columns under aerobic and strictly anaerobic conditions to examine the effects of solution ionic strength (1, 10 and 100 mM) and oxygen tension on the fate of the facultative Pseudomonas aeruginosa. Experimental results indicated that growth under aerobic or anaerobic conditions altered the surface properties of P. aeruginosa through bacterial surface substrates (e.g. 1.19 and 1.23 times higher protein and polysaccharides content under anaerobic conditions than under aerobic conditions). This significantly influenced the transport and deposition of P. aeruginosa in the saturated porous media as lower normalized breakthrough concentrations were observed under aerobic conditions (C/C0 = 0.89, 0.61 and 0.44 at 1, 10 and 100 mM, respectively) as compared to anaerobic conditions (C/C0 = 0.90, 0.74, 0.54 at 1, 10 and 100 mM, respectively). When predicting the travel trajectory of P. aeruginosa through natural aquifers, practitioners need to be aware that deposition rates obtained under aerobic conditions are not the same under anaerobic conditions. As such, research exploring the transport ability of a broad range of species under anaerobic conditions needs to be further developed. In the third part, experiments were performed in quartz sand packed bed columns under aerobic conditions to examine how a Cryptosporidium surrogate (glycoprotein modified microspheres) transport is affected by variables such as flow velocity, alum addition and humic acid (HA) adsorption. Experimental results showed increased normalized breakthrough concentrations of the glycoprotein modified microspheres with increased flow rate (C/C0 of 0.006, 0.017 and 0.030 at 4.6, 10.9 and 21.8 m/day, respectively), possibly due to increased hydrodynamic forces. Addition of 5 mg/L alum significantly increased the removal of the modified microspheres (C/C0 of 0.003, 0.003 and 0.010 at 4.6, 10.9 and 21.8 m/day, respectively), while the adsorption of 1 mg/L HA on the sand collector induced the opposite effect (C/C0 of 0.062 and 0.015 as compared to 0.017 and 0.003 at 10.9 m/day). The combined effects of alum and HA for Cryptosporidium surrogate removal seemingly eliminated the effects of alum in filtration. The utilization of this surrogate can satisfy the need for studying the filtration of Cryposporidium as their surface properties and structures resembled well to those of the viable Cryptosporidium, while eliminating personnel health hazards.