Browsing by Author "Zelver, Nick"

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Analysis and Monitoring of Heat Transfer Tube Fouling
(1982-10) Zelver, Nick; Flandreau, J. R.; Spataro, W. H.; Chapple, K. R.; Characklis, William G.; Roe, Frank L.
Bacterial characterization of toilet bowl biofilms
(1998-08) Pitts, Betsey; Stewart, Philip S.; McFeters, Gordon A.; Hamilton, Martin A.; Willse, Alan Ray; Zelver, Nick
Methods have been developed and applied for sampling, characterizing and quantifying naturally occurring toilet bowl biofilms. Ceramic porcelain disks mounted in neoprene rubber strips were sealed in place in toilet bowls in three residences in Bozeman, Montana. In each bowl, duplicate strips were placed above, at and below the water level. In 7 consecutive weeks, duplicate disks from each zone in each bowl were removed. Surface biofouling was measured by viable cell areal density. Specific fouling rates were calculated and variability among toilet bowls and water levels was assessed. Specific fouling rates ranged from 0.0 to 0.46d‐1. Average areal cell densities at the end of 7 weeks ranged from 103 to 107cfu cm‐2. The extent of fouling was highest below the water line. Neutralization of the chlorine residual (typically 0.9 mg l‐1) in one toilet did not increase the extent of fouling compared to the controls. Biofilm areal viable cell densities and bowl water viable counts were positively correlated (r = 0.78). The visual threshold for detection of toilet bowl biofilm by the naked eye was approximately 105 cfu cm‐2. In a heavily fouled toilet bowl, the biofilm was up to 20 μm thick. Microorganisms were isolated from the biofilm and identified. Of the 32 organisms that were further characterized, 10 were identified as Pseudomonas, Sphingomonas or Chryseomonas species.
Biofilm growth and hydraulic performance
(1980) Picologlou, B. F.; Zelver, Nick; Characklis, William G.
An experimental investigation of the deleterious effect of microbial slime layers on the hydraulic performance of water conduits is presented. The underlying mechanisms that lead to an increase of frictional losses in the conduit are explored and their relative importance is discussed. It is shown that although the slime layer is viscoelastic and filamentous, its effect on frictional resistance can be adequately represented through an increase in rigid equivalent sand roughness of the conduit wall.
Biofouling control with UV/peroxide - A laboratory study
(1981) Zelver, Nick; Legan, R.; Characklis, William G.
Biofouling film development and its effects on energy losses: a laboratory study
(1980) Characklis, William G.; Bryers, James D.; Trulear, Michael Gerald; Zelver, Nick
Experiments on biofouling of tubes are reported. Processes leading to fouling biological film development are identified and the procedures used in the experimental work are described. Results concerning the growth of biofouling and its effects on fluid friction and heat transfer are presented.
Color measurement as a means of quantifying surface biofouling
(1998-11) Pitts, Betsey; Hamilton, Martin A.; McFeters, Gordon A.; Stewart, Philip S.; Willse, Alan Ray; Zelver, Nick
Laboratory reactors fitted with removable ceramic porcelain growth surfaces were inoculated with a consortium of biofilm forming environmental isolates. A Minolta colorimeter CR-200 (Minolta Camera Co., Ltd, Ramsey, NJ) was used in conjunction with a specially designed adapter to evaluate the reflective color of the porcelain disks as biofilm accumulated on them. Areal viable cell counts were monitored over a period of eleven days in two separate experiments and direct color measurements of the untreated, microbially fouled test surfaces were collected. This colorimetric assay was both non-destructive and immediate. A strong linear relationship between log cell density and log color change was observed. The Pearson product moment correlation coefficient for all 45 observations combined was r=0.95. Separate regression lines for each experiment were not significantly different (P=0.19). When adjusted for time, the (partial) correlation coefficient between log cell density and log color change was r=0.87, which suggests that the relationship between the two measures can not be explained by their mutual dependence on time. Reflective color measurement provided a rapid, non-destructive and quantitative measure of biofilm accumulation.
Development of a standardized antibiofilm test
(2001) Zelver, Nick
Discriminating between biofouling and scaling in a deposition monitor
(1981) Zelver, Nick; Characklis, William G.; Roe, Frank L.
Dynamics of Biofilm Processes: Methods
(1982-01) Characklis, William G.; Bryers, James D.; Trulear, Michael Gerald; Zelver, Nick
Methods available for measuring biofilm accumulation are presented. The methods are conveniently classified as either direct or indirect measurement techniques. The direct techniques involve measurement of biofilm thickness or biofilm mass. The indirect measurement techniques include (1) methods for measuring specific biofilm constituents (e.g. polysaccharide) and (2) methods for determining microbial activity within the biofilm. These methods are discussed in relation to their use in both laboratory studies and in the field for continuous monitoring of biofilm processe
Energy losses in water conduits: monitoring and diagnosis
(1981) Characklis, William G.; Zelver, Nick; Turakhia, Mukesh Harilal
Fouling in heat exchange equipment
(1981) Characklis, William G.; Zelver, Nick; Turakhia, Mukesh Harilal
Hydraulic deterioration due to microbial slime growths
(1978) Characklis, William G.; Zelver, Nick; Picologlou, B. F.
Influence of biofouling and biofouling control techniques on corrosion of copper-nickel tubes
(1983) Characklis, William G.; Zelver, Nick; Nelson, Christopher H.; Lewis, R. O.; Dobb, David E.; Pagenkopf, G. K.
Measuring antimicrobial effects on biofilm bacteria: From laboratory to field
(1999) Zelver, Nick; Hamilton, Martin A.; Pitts, Betsey; Goeres, Darla M.; Walker, Diane K.; Sturman, Paul J.; Heersink, Joanna
Microbial film development and associated energy losses
(1979) Bryers, James D.; Characklis, William G.; Zelver, Nick; Nimmons, M. G.
Microbial Films and Energy Losses
(1984) Characklis, William G.; Zelver, Nick; Turakhia, Mukesh Harilal
Fouling microbial film formation can cause significant energy losses as reflected by increased fluid frictional resistance and heat tranfer resistance. Methods to predict and monitor rate of microbial film formation and its effect on energy losses in different environments is essential for efficient design and operation of engineering systems. This paper will discuss measurement methods and their incorporation in predictive models.
A microtiter-plate screening method for biofilm disinfection and removal
(2003-08) Pitts, Betsey; Hamilton, Martin A.; Zelver, Nick; Stewart, Philip S.
A quantitative spectrophotometric method was developed to measure the removal and killing efficacy of antibiofilm agents. Biofilms of Pseudomonas aeruginosa or Staphylococcus epidermidis were grown in 96-well plates, treated with an agent, then stained with either the biomass indicator crystal violet or the respiratory indicator 5-cyano-2,3-ditolyl tetrazolium chloride. This rapid screening method is sensitive enough to elucidate concentration–response relationships as well as differences between species responses to treatments. Using these assays, agents can be ranked by their ability to remove or kill biofilm.
Monitoring of fouling deposits: a key to heat exchanger management
(1985-09) Roe, Frank L.; Zelver, Nick; Characklis, William G.
The fouling of heat exchanger and other piping or vessel surfaces can be monitored by measuring pressure, flow, temperature, and heat flux, then using the results to calculate fluid frictional resistance. Results can be employed to evaluate treatments for fouling control and study the effect of equipment configurations and operating conditions on containment buildup.
On-line side-stream monitoring of biofouling
(1993) Roe, Frank L.; Wentland, Eric Jon; Zelver, Nick; Warwood, B. K.; Waters, Ralf; Characklis, William G.
Potential for Monitoring Fouling in the Food Industry
(1985) Zelver, Nick; Roe, Frank L.; Characklis, William G.