Showing papers on "Biofilm published in 1988"
TL;DR: Experiments showed that monochloramine was as effective as free chlorine for inactivation of biofilm bacteria and the interaction of biocides with pipe surfaces provides important insights into strategies for control ofBiofilm bacteria.
Abstract: The current project was developed to examine inactivation of biofilm bacteria and to characterize the interaction of biocides with pipe surfaces. Unattached bacteria were quite susceptible to the variety of disinfectants tested. Viable bacterial counts were reduced 99% by exposure to 0.08 mg of hypochlorous acid (pH 7.0) per liter (1 to 2 degrees C) for 1 min. For monochloramine, 94 mg/liter was required to kill 99% of the bacteria within 1 min. These results were consistent with those found by other investigators. Biofilm bacteria grown on the surfaces of granular activated carbon particles, metal coupons, or glass microscope slides were 150 to more than 3,000 times more resistant to hypochlorous acid (free chlorine, pH 7.0) than were unattached cells. In contrast, resistance of biofilm bacteria to monochloramine disinfection ranged from 2- to 100-fold more than that of unattached cells. The results suggested that, relative to inactivation of unattached bacteria, monochloramine was better able to penetrate and kill biofilm bacteria than free chlorine. For free chlorine, the data indicated that transport of the disinfectant into the biofilm was a major rate-limiting factor. Because of this phenomenon, increasing the level of free chlorine did not increase disinfection efficiency. Experiments where equal weights of disinfectants were used suggested that the greater penetrating power of monochloramine compensated for its limited disinfection activity. These studies showed that monochloramine was as effective as free chlorine for inactivation of biofilm bacteria. The research provides important insights into strategies for control of biofilm bacteria.
583 citations
555 citations
TL;DR: In this article, a biofilm reactor, termed the permeable-support biofilm (PSB), was developed in which oxygen was supplied to the interior of the biofilm through a permeable membrane.
103 citations
TL;DR: The oxidation rate of ferrous iron by biofilm of Thiobacillus ferrooxidans was determined and the kinetics of the process was described by the Monod equation with respect to the mass of the biofilm and with ferrous ions as the limiting substrate.
Abstract: The influence of temperature, pH, and substrate and product concentrations on the oxidation rate of ferrous iron by biofilm of Thiobacillus ferrooxidans was determined. The experiments were performed in an inverse fluidized-bed biofilm reactor in which the biofilm thickness was kept constant at 80 μm. Oxygen concentration and diffusion through the biofilm did not limit the oxidation rate. The oxidation rate was almost unaffected by temperature between 13 and 38°C, pH between 1.3 and 2.2, ferric iron concentration up to 14 g/L, or ferrous iron concentration from 4 to 13 g/L. The kinetics of the process was described by the Monod equation with respect to the mass of the biofilm and with ferrous ions as the limiting substrate.
73 citations
TL;DR: There is little doubt that increasing the extent of biofilm, by the addition of surfaces in daphnid-rearing tanks, will result in higher productivities in large-scale installations.
56 citations
01 Jan 1988
39 citations
TL;DR: A study of the development of biofilm colonizing the surfaces of pipes in a drinking-water distribution system has shown that water velocity significantly influenced the nature and physiological activity of the biofilm.
Abstract: A study of the development of biofilm colonizing the surfaces of pipes in a drinking-water distribution system has shown that water velocity significantly influenced the nature and physiological activity of the biofilm. Biofilm developed at a velocity of 0.5 m s−1 actively oxidized and deposited manganese, but at 0.01 m s−1 no manganese was deposited. Budding bacteria were the dominant microorganisms depositing manganese but a variety of other organisms were also present in the biofilms. The budding bacteria oxidizing manganese were Pedomicrobium manganicum and Metallogenium.
35 citations
TL;DR: In this paper, a simple model based on a reaction scheme NO 3 − → NO 2 − → products of two consecutive zero-order reactions was developed to understand the reactor start-up, changes of biofilm density with biofilm thickness, reactor hydrodynamics and axial concentration profiles of nitrate and nitrite species.
33 citations
Journal Article•
TL;DR: In this article, the effects of the attaching surface on biofilm shear loss and accumulation were investigated using two granular ac tivated carbons with very different surface structures, and the BFAC model was used to interpret the experimental results.
Abstract: Effects of the attaching surface on biofilm shear loss and accumulation were investigated using two granular ac tivated carbons with very different surface structures. Experimental evaluations were performed with a completely-mixed flow reactor. The BFAC model was used to interpret the experimental results. Results showed that a very irregular carbon surface provided better protection for initial biofilm growth and an earlier start for bio regeneration than did the spherical medium. The initial biofilm loss rates for the 2 carbons were 0.0 and 0.2 day-1, respectively and the shear loss rate coefficients were increased to 0.6 to 1.2 day-1 for both carbons after complete growth. During a period of rapid biofilm growth and GAC bioregeneration, the biofilm loss rate increased as a complex function that could not be de scribed by a simple first-order loss function. /. Water Pollut. Con trol Fed., 60, 362 (1988).
32 citations
TL;DR: The model shows why layered fixed‐film reactors can withstand high and inhibitory concentrations of volatile fatty acids as well as severe overloading without failure and predicts both substrate flux net uptake and methane production for steady‐state conditions.
Abstract: Development of a novel two-layer anaerobic biofilm model is based on substrate utilization kinetics and mass transport. The model is applied to steady-state conditions for a fixed-film anaerobic reactor. The microbial film is considered to consist of two distinct biofilm layers, one adjacent to the second, with an acidogenic bacteria biofilm forming the outer layer and a methanogenic film the inner one. The model assumes that sugars are only metabolized by the first layer and converted into volatile fatty acids (VFA), while fatty acids are taken up only by the inner layer. The model is able to predict both substrate flux net uptake and methane production for steady-state conditions. The results of modeling agree with methane production experimental data published elsewhere. Further, the model shows why layered fixed-film reactors can withstand high and inhibitory concentrations of volatile fatty acids as well as severe overloading without failure.
23 citations
TL;DR: The tested biofilm kinetic model successfully predicted the rates at which p -cresol and the 2,4- d ester were removed by natural biofilms when the experimental reactors were operated under a wide range of biological and mass transport conditions.
TL;DR: The extended steady state biofilm model is utilized to predict the performance of a completely mixed biofilm reactor in terms of substrate removal, biofilm accumulation, soluble microbial products (SMP) formation, and total soluble organic carbon (SOC) removal.
Abstract: The extended steady state biofilm model is utilized to predict the performance of a completely mixed biofilm reactor in terms of substrate removal, biofilm accumulation, soluble microbial products (SMP) formation, and total soluble organic carbon (SOC) removal. Three important aspects of how SMP formation affects the effluent quality from biofilm reactors for the concentration range of practical interest are relevant to advanced wastewater treatment, groundwater recharge, and drinking water treatment. First, for intermediate surface loadings, the concentrations of the effluent SMP and SOC are directly proportional to the influent substrate concentration, and SMP comprises the majority of effluent SOC. However, for high and very low loading, residual substrate is most of the effluent SOC. Second, SMP formation and SOC removal by the steady state biofilms are affected by both substrate utilization kinetics and reactor conditions. Changing reactor conditions, such as hydraulic detention time, affect the actual surface loading, while kinetic parameters, such as biofilm loss rate and cell yield, control the minimum achievable substrate concentration (S\dm\di\dn) and the minimum flux to give a deep biofilm (J\dd\de\de\dp). Third, in order to achieve the best treatment efficiency in terms of organic carbon (C), the biofilm reactor must maintain an optimum biofilm thickness that gives the lowest SOC concentration. At least in concept, biofilm thickness can be controlled by manipulating the shear loss component of the biofilm loss rate.
TL;DR: Observations made in this study suggest that bacterial adherence may not require an obvious biofilm layer, and therefore biomaterial infections involving other regions of the body may not need to be reported.
TL;DR: Results from the model system indicate that biocides may increase the time before the development of high microbial numbers, both in the biofilm and the coolant.
TL;DR: Antibiotic-induced inhibition of incorporation of [3H]leucine into the cells in the biofilm was far less pronounced than incorporation into planktonic cells and, furthermore, correlated well with loss in viable counts.
Abstract: A simple radiochemical method for evaluating the action of antibiotics on Escherichia coli cells in biofilms is reported. After growth, biofilms of E. coli ATCC 25922 on disks of urinary catheter material were suspended in fresh medium containing or lacking an antibiotic, incubated for 4 h at 37 degrees C, and pulse-labeled with (/sup 3/H)leucine for 5 min. Radioactivity in trichloracetic acid-precipitable material in the biofilm and in the surrounding medium (planktonic E. coli) was then measured. Antibiotic-induced inhibition of incorporation of (/sup 3/H)leucine into the cells in the biofilm was far less pronounced than incorporation into planktonic cells and, furthermore, correlated well with loss in viable counts. The method is simple, inexpensive, and extremely timesaving.
TL;DR: In this article, the authors used a recirculating chamber in situ to measure the bacterial oxygen uptake rate (BUR) for sewage fungus biofilms in rivers and found that BUR decreased with time during measurements.
01 Jan 1988
TL;DR: In this article, the influence of biofilm kinetics on the biofilm structure was studied at macroscopic and microscopic levels, and it was evident that the traditional modelling of wastewater treatment processes in biofilm reactors based on substrate removal kinetics alone will fail in many cases, due to the inevitable changes in the biofil structure not taken into consideration.
Abstract: Experimental investigations on the kinetics of wastewater treatment processes in biofilms were performed in a laboratory reactor. Parallel with the kinetic experiments, the influence of the biofilm kinetics on the biofilm structure was studied at macroscopic and microscopic levels. The close interrelationship between biofilm kinetics and structural changes caused by the kinetics is illustrated by several examples. From the study, it is evident that the traditional modelling of wastewater treatment processes in biofilm reactors based on substrate removal kinetics alone will fail in many cases, due to the inevitable changes in the biofilm structure not taken into consideration. Therefore design rules for substrate removal in biofilms used for wastewater treatment must include correlations between the removal kinetics and the structure and development of the biological film.
Dissertation•
01 Jan 1988