Browsing by Author "Butterfield, Phillip W."

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Chlorination of model drinking water biofilm: implications for growth and organic carbon removal
(2002-10) Butterfield, Phillip W.; Camper, Anne K.; Ellis, B. D.; Jones, Warren L.
The influence of chlorine on biofilm in low organic carbon environments typical of drinking water or industrial process water was examined by comparing biomass and kinetic parameters for biofilm growth in a chlorinated reactor to those in a non-chlorinated control. Mixed-population heterotrophic biofilms were developed in rotating annular reactors under low concentration, carbon-limited conditions (<2 mg/L as carbon) using three substrate groups (amino acids, carbohydrates and humic substances). Reactors were operated in parallel under identical conditions with the exception that chlorine was added to one reactor at a dose sufficient to maintain a free chlorine residual of 0.09¯0.15 mg/L in the effluent. The presence of free chlorine resulted in development of less biofilm biomass compared to the control for all substrates investigated. However, specific growth and organic carbon removal rates were on the average five times greater for chlorinated biofilm compared to the control. Observed yield values were less for chlorinated biofilm. Although chlorinated biofilm's specific organic carbon removal rate was high, the low observed yield indicated organic carbon was being utilized for purposes other than creating new cell biomass. The impacts of free chlorine on mixed-population biofilms in low-nutrient environments were different depending upon the available substrate. Biofilms grown using amino acids exhibited the least difference between control and chlorinated kinetic parameters; biofilm grown using carbohydrates had the greatest differences. These findings are particularly relevant to the fundamental kinetic parameters used in models of biofilm growth in piping systems that distribute chlorinated, low-carbon-concentration water.
Development and structure of drinking water biofilms and techniques for their study
(1999-12) Camper, Anne K.; Burr, Mark D.; Ellis, B. D.; Butterfield, Phillip W.; Abernathy, Calvin G.
Development of a toolbox to assess microbial contamination risks in small water systems
(2004-12) Butterfield, Phillip W.; Camper, Anne K.
Individual and small water systems account for the majority of waterborne disease outbreaks recorded in the United States each year. To address this problem a project was undertaken to develop a comprehensive self-assessment toolbox that could be used by small water system personnel to determine where their system has the greatest potential risks from microbial contamination. The toolbox components consist of: (1) a survey that asks specific questions; (2) a ranking tool that computes numerical scores for water system components based on survey answers; (3) comments and results from the ranking tool; (4) a guidance document to help the user understand why certain conditions may represent a risk; and (5) instructions for using the toolbox. A unique feature of the ranking tool is the ability to input expert opinion in the form of scores for each answer and weighting factors. Weighting factors are derived using ranked, pairwise comparisons, and then used to determine numerical scores for system components. Toolbox administrators are allowed to modify weighting factors used by the ranking tool application, thus allowing input of expert opinion.
Effects of carbon source, carbon concentration, and chlorination on growth related parameters of heterotrophic biofilm bacteria
(1999-11) Ellis, B. D.; Butterfield, Phillip W.; Jones, Warren L.; McFeters, Gordon A.; Camper, Anne K.
To investigate the growth of heterotrophic biofilm bacteria, a model biofilm reactor was developed to simulate a drinking water distribution system. Controlled addition of three different carbon sources (amino acids, carbohydrates, and humics) at three different concentrations (500, 1,000, and 2,000 ppb carbon), in the presence and absence of chlorine, was used in separate experiments. An additional experiment was run with a 1:1:2 mixture of the above carbon sources. Biofilm and effluent total and culturable cells, in addition to total and dissolved organic carbon, were measured in order to estimate specific growth rates (SGRs), observed yields, population densities, and bacterial carbon production rates. Bacterial carbon production rates (mg C/L day) were extremely high in the control biofilm communities (range = 295-1,738). Both growth rate and yield decreased with increasing carbon concentrations. Therefore, biofilm growth rates were zero-order with respect to carbon concentrations used in these experiments. There was no correlation between growth rate and carbon concentration, but there was a significant negative correlation between growth rate and biofilm cell density (r = -0.637, p = 0.001 control and r = -0.57, p = 0.021 chlorinated biofilms). Growth efficiency was highest at the lowest carbon concentration (range = 12 - 4.5%, amino acids and humics respectively). Doubling times ranged from 2.3 - 15.4 days in the control biofilms and 1 - 12.3 days in the chlorinated biofilms. Growth rates were significantly higher in the presence of chlorine for the carbohydrates, humics, and mixed carbon sources (p = 0.004, <0.0005, 0.013, respectively). The concept of r/K selection theory was used to explain the results with respect to specific growth rates and yields. Humic removal by the biofilm bacteria (78% and 56% for the control and chlorinated biofilms, respectively) was higher than previously reported literature values for planktonic bacteria. A number of control experiments indicated that filtration of drinking water was as effective as chlorination in controlling bacterial biofilm growth.
Evaluation of Characterization Techniques for Iron Pipe Corrosion Products and Iron Oxide Thin Films
(2008-10) Borch, Thomas; Camper, Anne K.; Biederman, Joel A.; Butterfield, Phillip W.; Gerlach, Robin; Amonette, James E.
A common problem faced by drinking water studies is that of properly characterizing the corrosion products (CP) in iron pipes or synthetic Fe (hydr)oxides used to simulate the iron pipe used in municipal drinking-water systems. The present work compares the relative applicability of a suite of imaging and analytical techniques for the characterization of CPs and synthetic Fe oxide thin films and provide an overview of the type of data that each instrument can provide as well as their limitations to help researchers and consultants choose the best technique for a given task. Crushed CP from a water distribution system and synthetic Fe oxide thin films formed on glass surfaces were chosen as test samples for this evaluation. The CP and synthetic Fe oxide thin films were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive spectroscopy, time-of-flight secondary ion mass spectrometry(ToF-SIMS), X-ray powder diffractometry (XRD), grazing incident diffractometry (GID), transmission electron microscopy (TEM), selected area electron diffraction, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared, MÃ¶ssbauer spectroscopy, Brunauerâ€“Emmettâ€“Teller N2 adsorption and Fe concentration was determined by the ferrozine method. XRD and GID were found to be the most suitable techniques for identification of the mineralogical composition of CP and synthetic Fe oxide thin films, respectively. AFM and a combined ToF-SIMSâ€“AFM approach proved excellent for roughness and depth profiling analysis of synthetic Fe oxide thin films, respectively. Corrosion products were difficult to study by AFM due to their surface roughness, while synthetic Fe oxide thin films resisted most spectroscopic methods due to their limited thickness (118 nm). XPS analysis is not recommended for mixtures of Fe (hydr)oxides due to their spectral similarities. SEM and TEM provided great detail on mineralogical morphology.
Minimizing biofilm in presence of iron oxides and humic substances
(2002-09) Butterfield, Phillip W.; Camper, Anne K.; Biederman, Joel A.; Bargmeyer, Alex Martin
Based upon circumstantial evidence linking elevated coliform bacteria counts in drinking water distribution systems with unlined cast iron pipe, it was hypothesized that adsorption of humic substances by iron oxide containing corrosion products (CPs) can stimulate and/or support biofilm development. Using porous media consisting of iron-oxide-coated glass beads (IOCBs) or actual iron Cps, experiments were performed to evaluate the effectiveness of different corrosion control and disinfection treatments in reducing biofilm when humic substances were the carbon source. Free chlorine was the most effective treatment in minimizing biofilm. Addition of phosphate alone did not significantly reduce biofilm using the CPs, but there was weak evidence it did using the IOCBs. The combination of free chlorine and phosphate was more effective at minimizing biofilm than free chlorine alone when CPs were the media. The presence of humic substances was a major factor when considering biofilm minimization based on results of experiments using both types of iron oxide media. The combination of humic substances and CPs led to an increase in biofilm biomass when free chlorine was not present, similar to conditions that could occur at distribution system dead-ends. Treatment to raise the pH to 9 did not reduce biofilm in experiments using both media, and actually increased biofilm in the experiment using CPs under the conditions tested.
Modified enzyme activity assay to determine biofilm biomass
(2002-06) Butterfield, Phillip W.; Bargmeyer, Alex Martin; Camper, Anne K.; Biederman, Joel A.
An assay of potential exoproteolytic enzyme activity was modified to quantitatively measure the biomass of attached biofilm. The assay utilized the nonfluorescent compound l-leucine-β-naphthylamide (LLβN) that becomes fluorescentwhen bacterial exoenzymes break the peptide bond, releasing the fluorochrome β-naphthylamine. Fluorescence development was measured by pumping the liquid phase of a biofilm sample through a fluorescence detector and recording the detector output using a personal computer. A significant linear relationship was shown to exist between the rate of fluorescence development and the biofilm's biomass as carbon, determined using total direct cell counts, measured cell volumes and an existing relationship between cell volume and cell carbon. The technique was used to measure biofilm biomass for experiments where iron oxides were the substratum. Biofilm biomass measurements made using heterotrophic plate counts (HPCs) on R2A medium were shown to correlate well to biomass measurements made using the modified enzyme assay. The technique was shown to be sufficiently sensitive to measure biomass on samples containing little biofilm biomass, such as those exposed to free chlorine. While granular and porous media were used for the experiments presented, small biofilm coupons could easily be used to measure biofilm biomass, expanding the number of possible applications for the enzyme assay technique.