Analysis of Bacterial Deposition on Metal (Hydr)oxide-Coated Sand Filter Media
✍ Scribed by S.E Truesdail; J Lukasik; S.R Farrah; D.O Shah; R.B Dickinson
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 943 KB
- Volume
- 203
- Category
- Article
- ISSN
- 0021-9797
No coin nor oath required. For personal study only.
✦ Synopsis
media. Several recent papers have described enhanced re-The aim of this study was to investigate the importance of moval efficiencies in filtration systems utilizing metal oxides surface potential in microbial deposition onto modified granular and metal hydroxides (1-5). In spite of some success in surfaces. Recent experimental and theoretical work has indicated this area, a fundamental understanding of why deposition is that surfaces coated with metal oxides and hydroxide rich oxide/ improved to a greater degree in some coatings and not in hydroxide mixtures ((hydr)oxides) have the potential to increase others often appears to be lacking. Improved understanding the capture efficiencies of commercial filtration systems. This of the mechanisms influencing particle attachment could aid study quantitatively compared different metal (hydr)oxide coatin the design of more efficient filter media in a wide range ings in their abilities to enhance bacterial deposition. Specifically, of industrial applications. Bacterial adhesion, however, is the deposition rates of bacterial strains Streptococcus faecalis, Staphylococcus aureus, Salmonella typhimurium, and Escherichia difficult to quantify at a fundamental level. Hydration forces coli were compared for Ottawa sand and surface coatings con-(6), hydrophobic interactions (8-11), macromolecular sisting of aluminum (hydr)oxide, iron (hydr)oxide, and mixed bridging (12), surface roughness (13), and electrical douiron and aluminum (hydr)oxide. The metal-(hydr)oxide-modible-layer and van der Waals forces (1, 7, 14-16) have all fied granular media enhanced bacterial deposition relative to the been proposed as possible influences on adhesion. Many of noncoated Ottawa sand. The electropositive surfaces, the alumithese factors, however, are difficult to experimentally meanum and the mixed (hydr)oxides, had similar average kinetic rate sure for microbial attachment to granular media. An arguable constants, five times larger than the rate constants observed for exception to this observation is the measurement of zeta the untreated Ottawa sand. The measured kinetic rate constants potential and its influence on particle interaction forces. This for the positively charged systems of aluminum (hydr)oxide and study attempts to exploit these electrical double-layer and mixed (hydr)oxide collectors suggested that the overall rate of van der Waals forces with the use of metal hydroxide coatdeposition was limited by the transport of bacteria to the granular surface rather than the rate of attachment. For systems where the ings in order to improve microbial adhesion.
collector surfaces were negatively charged, as in the cases of Ot-
The role of electrical double-layer and van der Waals forces tawa sand and the iron (hydr)oxide coating, large energy barriers in particle deposition is often viewed in terms of DLVO theory to attachment were predicted from DLVO theory but these barriers (17,18). Figure 1 illustrates two regions of particle deposition did not totally inhibit bacterial deposition. The deposition results predicted by DLVO theory for the interaction between two could not be fully explained by DLVO theory and suggested the charged surfaces. The dashed line represents the interaction importance of other factors such as collector charge heterogeneity, expected between a strong negatively charged collector such motility, and bacterial surface appendages in enhanced deposition.
as Ottawa sand and a negative bacteria particle. This line falls