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PubMed1999

Comparison of microvascular filtration in human arms with and without postmastectomy oedema.

Oedema is caused by impaired lymphatic drainage and/or increased microvascular filtration. To assess a postulated role for the latter in postmastectomy oedema, filtration was studied in the forearms of 14 healthy subjects and 22 patients with chronic, unilateral arm oedema caused by surgical and radiological treatment for breast cancer. A new non-contact optical device (the Perometer) and a conventional mercury strain gauge were used simultaneously to record forearm swelling rates caused by microvascular filtration during applied venous congestion. Filtration rate (FR) per 100 ml tissue was measured over 10-15 min at a venous pressure of 30 cmH2O, a pressure reached in the dependent forearm (FR30), and then at 60 cmH2O (FR60). Apparent filtration capacity of 100 ml soft tissue (CFCa) was calculated from FR60 - FR30/30, after adjustment for bone volume. The Perometer and strain gauge gave similar results in normal and oedematous arms. Mean CFCa in healthy subjects was (3.8+/-0.4) x 10(-3) ml (100 ml)-1 cmH2O-1 min-1, close to literature values. In the patients, FR30 was 47 % lower in the oedematous forearm than in the opposite, unaffected forearm (P = 0.04). FR60 showed a similar trend but did not reach significance (P = 0.15). The values of CFCa of (2.2+/-0.5) x 10(-3) ml (100 ml)-1 cmH2O-1 min-1 in the oedematous arm and (2.8+/-0.5) x 10(-3) ml (100 ml)-1 cmH2O-1 min-1 in the unaffected arm were not significantly different (P = 0.47). When differences in arm volume on the two sides were taken into account, the total fluid load on the lymphatic system of the oedematous forearm was (411.0+/-82.2) x 10(-3) ml min-1 at 30 cmH2O and (1168+/-235.6) x 10(-3) ml min-1 at 60 cmH2O, similar to the normal side, namely (503.7+/-109.3) 10(-3) ml min-1 and (1063+/-152.0) x 10(-3) ml min-1, respectively (P >/= 0.50). The filtration capacity of the entire oedematous forearm (CFCa scaled up by total soft tissue volume), (25.4+/-6.2) x 10(-3) ml cmH2O-1 min-1, was not significantly greater than that of the normal forearm, (18.3+/-2.6) x 10(-3) ml cmH2O-1 min-1 (P = 0.40). The results indicate that no major change occurs in the microvascular hydraulic permeability-area product of the forearm, or in the total filtration load on the lymph drainage system during dependency, in the arm with postmastectomy oedema compared with the normal arm. This argues against a significant haemodynamic contribution to postmastectomy oedema.

Aged↗
PubMed1981

Serum substitute in epithelial cell culture media: nonfat dry milk filtrate.

A number of milk types and milk fractions were investigated as possible substitutes for serum in cell culture media. A filtrate of reconstituted nonfat dry milk showed promise. Culture fluids containing 5% of the nonfat dry milk filtrate were used to propagate primary and continuous cell cultures, and the cell growth from these cultures was compared with that of cells grown in a serum-containing medium. The nonfat dry milk filtrate-supplemented medium supported the growth of all epithelial cells tested, but two fibroblast-type cultures failed to replicate. Cells grown in the medium containing the milk filtrate grew slowly for 2 to 3 days and then propagated to confluency in 6 to 8 days. Viable cell counts of 9 days were comparable to those of serum-grown cells that had been propagated for 7 days. Cells grown in the milk filtrate could be split 1 to 4 when subcultures were prepared. Cell growth could be stimulated by refeeding on days 2 to 3 or by the addition of 30 microM 2-mercaptoethanol to the growth medium. Virus susceptibility and titer comparisons with poliovirus 1, coxsackievirus B2, echovirus 7, and herpes simplex virus indicated that approximately the same data were obtained when either the nonfat dry milk filtrate-treated or the serum-treated cells were studied. The nonfat dry milk filtrate is inexpensive, is easily prepared, and is a substitute for serum in epithelial cell culture media.

Animals↗
PubMed1984

Microvascular filtration in subjects with connective tissue disorders.

A simple non-invasive method for studying microvascular filtration in the non-articular tissues of the forearm is described. Rates of filtration under a standard hydrostatic pressure were measured in 20 normal female subjects and 44 female subjects with connective tissue disorders. An increased mean filtration rate was found in 14 subjects with rheumatoid arthritis. In 20 subjects with systemic lupus erythematosus and 10 subjects with scleroderma no such generalised increase in filtration rates was seen, but isolated cases had very high filtration rates, suggesting a more heterogeneous physiological disturbance. Increased filtration was not associated with the presence of oedema. This confirms doubts raised by other workers about the importance of filtration in the genesis of clinical oedema.

Adult↗
PubMed1997

Changes in water microbial quality during bank filtration of lake water.

We studied, during a 2-year period, how the microbial stability of water changed when humus-rich lake water was filtered through the ground at a bank filtration water plant. The changes in microbial quality were followed as microbial numbers and growth activity. The filtration decreased microbial counts and growth ([3H]thymidine technique) in water up to 90%. The reduction in bacterial counts and growth depended on the filtration distance. The reduction was greatest between the lake and the first sampling point. Microbial numbers and growth declined steadily after infiltration with increased filtration distance. Viable counts of heterotrophic bacteria decreased faster than total bacterial counts along filtration. The microbial numbers and bacterial production in water followed seasonal changes in water temperature. Simultaneously with the microbial numbers, the concentrations of total organic carbon and assimilable organic carbon decreased during bank filtration. These results showed that microbial stability of humus-rich water was increased by filtration to a level generally found in natural groundwaters.

Bacteria↗
PubMed1986

Growth-enhancing effect of Branhamella catarrhalis culture filtrates on the L-forms of Haemophilus influenzae.

Haemophilus influenzae is a common respiratory pathogen and recurrent infection due to H. influenzae is a phenomenon often present in patients with chronic respiratory tract infections. The effects of Neisseria perflava and B. catarrhalis culture filtrates on the growth and reversion of H. influenzae L-forms were determined using the L-forms of H. influenzae induced and subcultured in a medium containing 10% sucrose and these culture filtrates. When each culture filtrate of two strains of N. perflava was added, the viable count of revertants reached a peak of growth after 48 hr and exceeded 10(4) CFU/ml even 48 days after the subculture. Adding each culture filtrate of six strains of B. catarrhalis, the viable count of revertants from the L-forms of H. influenzae was much higher than that in the absence of any filtrate (negative control). The filtrate of a culture prepared from one of the six strains of B. catarrhalis was subjected to biochemical analysis. The molecular weight of the growth-enhancing factor(s) was determined to be approximately 1,000 to 5,000. Some peptide fractions showed growth-enhancing effects on the L-forms of H. influenzae. These findings suggest that culture filtrates may be important clues as to the correlation between recurrent infections due to H. influenzae and the growth of L-forms in the sputum of the patients with chronic respiratory tract infections, during or after the administration of beta-lactam antibiotics.

Cell Division↗
PubMed2002

Cytotoxicity of Aspergillus fumigatus culture filtrate against macrophages.

Aspergillus fumigatus causes serious, life-threatening human infection, and is one of the most important pathogenic fungi. Little is known, however, about its mechanism of infection or its virulence factors. To learn about its virulence factors, the effect of the culture filtrate of A. fumigatus on macrophages was studied. When cocultured with A. fumigatus in 96-well microplates, murine peritoneal macrophages showed significant morphological changes indicating serious cellular damage, even when the macrophages were not in direct contact with the fungus. Then culture filtrates of Aspergillus spp., A. fumigatus, A. flavus, A. terreus and A. niger, were prepared by culturing the fungus in 96-well or 24-well microplates for 24 h, and the effect of the culture filtrates was determined by culturing macrophages with or without culture filtrate. When cultured with the culture filtrate of A. fumigatus at a concentration of 1% or higher, macrophages demonstrated significant morphological changes, leading to their death. Treatment with heat greatly lowered the activity of the culture filtrate. In contrast, culture filtrates of A. terreus and A. flavus showed no detectable effect on macrophages, whereas A. niger did display a similar, but much weaker effect. Our study strongly suggests that A. fumigatus releases a toxic product (s) in the medium very rapidly, and this may be critically involved as the virulence factor in human infection, at least in part, by causing serious injury to macrophages.

Animals↗
PubMed1992

[Rapid detection of mycobacteria in sputa using media supplemented with culture filtrate of Gemella haemolysans].

The effect of the culture filtrate Gemella haemolysans in enhancing mycobacterial growth has been previously demonstrated. In the present studies, an attempt was made to confirm whether the addition of the filtrate into the medium would be an effective method to promote the rapid detection of mycobacteria in sputum specimens of patients. One-hundred and one sputum specimens pretreated with NaOH were inoculated with various media (Dubos, Dubos-agar, 1% Ogawa, Kudo PD, and Middlebrook 7H9) supplemented with the culture filtrate of Gemella haemolysans grown in blood-BHI or blood-HEM at the dilutions of 1/32 or 1/64. Addition of the filtrate reduced the amount of time required to detect mycobacterial growth (Mycobacterium tuberculosis, M. avium complex, and M. kansassi) by an average of 60-70%. The media containing the filtrate formed significantly larger numbers of colonies compared with the control media, and those colonies inoculated developed more rapidly in size. The findings clearly indicated that the culture filtrate promotes the effective growth of mycobacteria which cannot or only slowly grows in ordinary media. Also indicated was that the addition of the culture filtrate of Gemella haemolysans into media provides as a useful tool to allow the rapid diagnosis of mycobacterial diseases.

Bacteriological Techniques↗
PubMed1991

Influence of white blood cells on the filterability of human erythrocytes: modelling of the filtration process and experimental results.

In medical research and clinical practice, the increasing application of filtration measurements, to characterize the erythrocyte deformability has aroused an intensive discussion about possible erroneous interpretations of measured values (filterability indices). In the present paper the influence of white blood cells (WBC) on these indices is described and discussed in relation to a mathematical model of the filtration process. We found for two gravity filtration systems, using cellulose filters and concentrated erythrocytes suspensions sensitivities of their filterability indices of (1 +/- 0.1)% per 100 WBC/microliter (initial filtration rate measurement) and (3 +/- 0.3)% per 100 WBC/microliter (hemofiltrometer). In comparison to Nuclepore filtration systems with sensitivities of 5-12% per 100 WBC/microliters, cellulose filters were much less sensitive to WBC. The necessity, advantages and disadvantages of additional procedures for WBC removal are discussed. A standardization of residual WBC-count in limits of 500 +/- 300 WBC/microliters at a hematocrit of 60% is proposed. Fitting of the filtration curves of the hemofiltrometer to a model function may either improve the accuracy of estimation of filterability indices or divide them into two model parameters with different WBC-sensitivities: the initial filtration rate parameter having a low WBC-sensitivity ((0.9 +/- 0.2)% per 100 WBC/microliter) and the occlusion related parameter having a 12 times higher sensitivity ((11 +/- 1)% per 100 WBC/microliter). Interpretation, advantages and disadvantages of the model parameters are discussed also in comparison to the filterability index.

Cellulose↗
PubMed1990

Gel filtration: a new method to analyze and separate red blood cells with different deformabilities.

Filtration of red blood cells through agarose gels (Sephadex, Sepharose, and Superose) was used to assess red cell deformability and simultaneously obtain fractions of red cells with different properties. The hemoglobin concentration in each fraction was used to define a filtration profile of red cells. It was found that gel filtration was a reproducible process. A gel filtration index (GFI) was derived from the height and the width of the filtration curve at half the maximum height. Osmotically treated red cells, red cells partially hardened with increasing glutaraldehyde concentrations, and mixtures of normal and hardened red cells were used to test the method. Changes in red cell deformability were sensitively detected by the GFI. The first fractions eluted from the column contained red cells with normal deformability, whereas the later fractions contained primarily less deformable cells with an increased membrane elastic modulus. By repeated filtration of late fractions it was possible to enrich the suspensions with less deformable cells. Patients with chronic renal failure had a decreased filterability; their GFI was 1.04 +/- 0.27 (n = 15) compared with 1.18 +/- 0.17 in controls (n = 20, p less than 0.05). We conclude that gel filtration is useful to detect and isolate abnormal red cell subpopulations. It could be a valuable tool for the investigation of disorders such as sickle cell anemia.

Chromatography, Gel↗
PubMed1985

Activation of the rat liver cytosol glucocorticoid receptor by sephacryl S-300 filtration in the presence and absence of molybdate. Physical properties of the receptor and evidence for an activation inhibitor.

The DNA-binding and physical properties of the rat liver cytosol glucocorticoid receptor were determined before and after Sephacryl S-300 filtration in the presence or absence of molybdate. Cytosol was prepared and labeled with [3H]triamcinolone acetonide in buffer containing molybdate. Prior to gel filtration, only 5 +/- 3% (mean +/- S.E.) of labeled receptors bound to DNA-cellulose. After gel filtration in the presence and absence of molybdate, the per cent of labeled receptors binding to DNA-cellulose was 57 +/- 10% and 83 +/- 1%, respectively. Nonreceptor fractions from the Sephacryl S-300 column contained a heat-stable factor which blocked receptor activation but did not block the binding of activated receptors to DNA-cellulose. The activation inhibitor eluted from the column in the region of the albumin standard, but after heating its size was considerably reduced (Mr less than 3500). Receptors activated by Sephacryl S-300 filtration underwent the same size changes in the presence or absence of molybdate. Prior to gel filtration, the S20,w of labeled receptors in the presence of molybdate was 9.2 +/- 0.2 S. After filtration in the presence and absence of molybdate, the S20,w of labeled receptors was 4.2 +/- 0.2 and 4.4 +/- 0.1 S, respectively. The Stokes radius (Rs) of labeled receptors after gel filtration in either the presence or absence of molybdate was 65 +/- 1 A. From the Rs and S20,w values, the molecular weight (Mr) of activated receptors was calculated to be 115,000 to 121,000, which was in close agreement with the Mr of affinity-labeled receptors determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Animals↗
PubMed1982

Bird manure filtrate agar for the formation of the perfect state of Cryptococcus neoformans, Filobasidiella neoformans. A comparative study of the agars prepared from pigeon and canary manure.

An account is given to two pairs of C. neoformans strains on two different bird manure filtrate agars, i.e. pigeon manure filtrate and canary manure filtrate agar. Basidiospore formation was observed in both pairs after 3 d incubation at 26 degrees C on both media. 0.1% biphenyl in pigeon manure filtrate agar showed an inhibitory activity on the formation of the perfect state of the C. neoformans pairs tested. Concentrated pigeon manure filtrate allowed growth of the imperfect, however not of the perfect state of C. neoformans. On canary manure filtrate agar, a brown color effect (BCE) of the colonies of the C. neoformans strains was observed in addition to their formation of the perfect state. Except for a known self-fertile strain no self-fertility could be seen in 40 C. neoformans strains on pigeon manure filtrate agar. Attention is drawn to the risk of laboratory infection when handling the perfect state of C. neoformans.

Agar↗
PubMed1997

[Niobium filtration in dental radiology. Effects on image quality and on dosage].

UNLABELLED: The necessity of reducing the radiation dose to the patient in diagnostic radiology according to the ALARA guideline established by the ICRP has stimulated the research on additional filtration systems capable of removing the low-energy photons increasing the dose and worsening image quality. Very few literature studies deal with the effects of niobium filtration on image quality in dental radiography with the use of modulation transfer function (MTF) and square wave response function (SWRF). Only one study has considered those effects measuring dose absorption in an anthropomorphic phantom. THE AIMS OF OUR STUDY WERE: 1) to study the effects of a 30 microns additional niobium filter on image quality using the SWRF; 2) to compare the doses absorbed in vivo during a complete radiographic survey of the mouth, both with and without niobium filtration. Qualitative studies led us to conclude that niobium filtration does not significantly worsen radiographic image quality. The following doses were measured in the exposures with niobium filtration: 1678 microGy to 6000 microGy (intraoral doses) and 75 microGy to 3643 microGy (skin doses). The comparison with the doses measured during the exposures made with conventional filtration indicates that dose reduction is not significantly advantageous relative to risk reduction. In conclusion, additional niobium filtration is not advisable in dental radiology, also because of the filter cost and of the increased wear of the unit.

Adolescent↗
PubMed2002

Fuji surge technique and continuous in-line filtration to improve the quality of single donor platelet concentrates.

White blood cell (WBC)-reduced single donor platelet concentrates (SDPs) can be collected by most cell separators. WBC reduction can be achieved directly during plateletpheresis or by filtration. Continuous filtration with low filtration rates provides SDPs of good purity. To compensate the platelet (PLT) loss due to filtration, the PLT yield in the unfiltered primary product should be optimal. Fifty donors underwent plateletpheresis with the MCS+ blood cell separator (Haemonetics) with the new Fuji surge technique and continuous WBC filtration. Twelve SDPs were analysed for PLT yield, red blood cells (RBC), WBC, and pH after collection (Day 0) and at the end of storage (Day 5). Thereafter, further 38 SDPs were measured for PLT and WBC content in routine production at Day 0. PLT were determined electronically, RBC and WBC were counted manually (Neubauer and Nageotte chamber, respectively). For pH measurement, a pH-meter was used. Mean blood volume processed was 2621 +/- 112 ml in a donation time of 76 +/- 10 min. An average PLT yield of 3.45 +/- 0.88 x 10(11) was collected in a product volume of 325 +/- 77 ml. The collection efficiency was 60.0 +/- 5.5%. WBC contamination of all units tested was 0.046 +/- 0.059 x 10(6) and the RBC content of the SDPs analysed at Day 0 was 0.014 +/- 0.003 x 10(9). The pH was well maintained over the storage period of 5 days. The data indicate that Fuji surge technique and continuous in-line leukocyte filtration allow for the collection of SDPs with high platelet yield and low leukocyte contamination, meeting the Council of Europe quality standards.

Blood Cell Count↗
PubMed1992

The effects of dopamine and a low protein diet on glomerular filtration rate and renal plasma flow in the aged kidney.

The aims of this study were to determine the effects of dopamine and a low protein diet on glomerular filtration rate and effective renal plasma flow in the aged kidney. Effective renal plasma flow was measured using 125I-labelled hippuran and glomerular filtration rate using 51Cr-labelled EDTA. Low-dose continuous intravenous dopamine 3 micrograms.kg-1.min-1 in 10 healthy elderly volunteers caused a significant increase in effective renal plasma flow but not in the mean glomerular filtration rate when compared with baseline. However, glomerular filtration rate did increase substantially in 5 subjects (mean 14.4, SD 1.3). This implied that the elderly kidney was working maximally without reserve capacity in half the elderly. Since renal function is likely to be even more reduced in elderly patients with congestive cardiac failure, dopamine infusions may have little place in this condition in some older patients. A low protein diet (0.69 g.kg-1) in the same volunteers reduced glomerular filtration rate, suggesting that protein restriction may help to reduce the increased filtration rate in the remaining nephrons, thereby leading to structural and functional preservation in the aged kidney.

Age Factors↗
PubMed2002

Leukocyte filtration fails to limit functional neutrophil activity during cardiac surgery.

OBJECTIVE AND DESIGN: The beneficial effects of leukocyte filtration on the outcome of cardiac surgery with cardiopulmonary bypass (CPB) is probably due to the limitation of pathogenesis mediated by over-stimulated neutrophils. However, the influence of leukocyte filtration on the functional neutrophil activity has not been studied in detail. Therefore, by using different filtration timing strategies we determined neutrophil effector functions before and after the filter passage as well as blood surrogate markers for neutrophil activation. METHODS: We randomly assigned 80 cardiac surgery patients to four groups (n = 20 each) without (1) and with three different filtration timing strategies (II-IV). As functional end points neutrophil phagocytic activity and oxidative burst upon ex vivo stimulation with E.coli were analyzed from blood of 31 patients whereas polymorphonuclear elastase (PMNE), myeloperoxidase, and malondialdehyde (MDA), a marker for lipid peroxidation was determined in plasma samples from 80 patients. Blood was harvested immediately before and behind the filter (Pall LG6) at different times during CPB. RESULTS: We found that none of the filtration strategies either reduced the number of neutrophils capable of eliciting phagocytic activity and oxidative burst or the activity per cell. In contrast, PMNE and MPO levels in peripheral venous blood were found to be significantly increased in groups II-IV compared with group I throughout the entire filtration period in all patients. MDA was not enhanced in the filter groups. CONCLUSIONS: Our results show that the leukocyte depletion filter in the arterial line of the heart-lung machine failed to limit neutrophil stimulation but rather augmented PMNE plasma levels. We speculate that augmented PMNE and MPO levels mainly stem from neutrophils that are captured within the mesh of the leukocyte filter.

Aged↗
PubMed1991

Evaluation of Niobi-X filtration in intraoral radiology.

This investigation studied the effect of adding niobium filtration to the dental x-ray beam assessing reduction in patient x-ray exposure and changes in image quality. Clinical radiographs were made with the use of D- or E-speed film with either aluminum or aluminum plus 25 microns or 30 microns of added niobium filtration. Similar exposures were made on a head phantom, measuring the absorbed dose to radiosensitive sites in the head and neck. Results indicated that the addition of 25 microns or 30 microns of niobium filtration does not significantly degrade the subjective image quality of diagnostic radiographs when D-speed film is used. With E-speed film, however, the addition of niobium filtration significantly degrades the diagnostic image quality. The addition of niobium filtration results in a 20% to 30% reduction in patient dose. We conclude that the use of niobium filtration with D-speed dental film is a positive contribution to patient care.

Aluminum↗
PubMed1976

Variability of Alternaria alternata: biochemical and immunological characteristics of culture filtrates from seven isolates.

Biochemical variability of culture filtrates from the common allergenic mold Alternaria alternata was studied. Differences between culture filtrates from 7 different isolates and between 4 batches of culture filtrate from the same isolate were observed, suggesting the unreliability of presently employed biochemical methods in the routine standardization of mold allergens and the possibility of difficulties in developing standard techniques for their purification. Dextranases, cellulases, and agarases, found in one culture filtrate, may be a further source of problems in laboratory techniques employing A. alternata. The proportions of nitrogen:carbohydrate:dialyzed dry weight were different in culture filtrates from each isolate. Polysaccharides in culture filtrates from 3 of the 7 isolated contained glucose, mannose, xylose, galactose, and a fifth, unidentified sugar. Polysaccharides from one isolate lacked xylose, and the fifth sugar was not demonstrable in 4 of the isolates. Despite the biochemical differences, extensive antigenic cross-reactivity between different isolates was found in precipitin studies and inhibition of antibody binding.

Alternaria↗
PubMed2005

Filtration and transport of Bacillus subtilis spores and the F-RNA phage MS2 in a coarse alluvial gravel aquifer: implications in the estimation of setback distances.

Filtration of Bacillus subtilis spores and the F-RNA phage MS2 (MS2) on a field scale in a coarse alluvial gravel aquifer was evaluated from the authors' previously published data. An advection-dispersion model that is coupled with first-order attachment kinetics was used in this study to interpret microbial concentration vs. time breakthrough curves (BTC) at sampling wells. Based on attachment rates (katt) that were determined by applying the model to the breakthrough data, filter factors (f) were calculated and compared with f values estimated from the slopes of log (cmax/co) vs. distance plots. These two independent approaches resulted in nearly identical filter factors, suggesting that both approaches are useful in determining reductions in microbial concentrations over transport distance. Applying the graphic approach to analyse spatial data, we have also estimated the f values for different aquifers using information provided by some other published field studies. The results show that values of f, in units of log (cmax/co) m(-1), are consistently in the order of 10(-2) for clean coarse gravel aquifers, 10(-3) for contaminated coarse gravel aquifers, and generally 10(-1) for sandy fine gravel aquifers and river and coastal sand aquifers. For each aquifer category, the f values for bacteriophages and bacteria are in the same order-of-magnitude. The f values estimated in this study indicate that for every one-log reduction in microbial concentration in groundwater, it requires a few tens of meters of travel in clean coarse gravel aquifers, but a few hundreds of meters in contaminated coarse gravel aquifers. In contrast, a one-log reduction generally only requires a few meters of travel in sandy fine gravel aquifers and sand aquifers. Considering the highest concentration in human effluent is in the order of 10(4) pfu/l for enteroviruses and 10(6) cfu/100 ml for faecal coliform bacteria, a 7-log reduction in microbial concentration would comply with the drinking water standards for the downgradient wells under natural gradient conditions. Based on the results of this study, a 7-log reduction would require 125-280 m travel in clean coarse gravel aquifers, 1.7-3.9 km travel in contaminated coarse gravel aquifers, 33-61 m travel in clean sandy fine gravel aquifers, 33-129 m travel in contaminated sandy fine gravel aquifers, and 37-44 m travel in contaminated river and coastal sand aquifers. These recommended setback distances are for a worst-case scenario, assuming direct discharge of raw effluent into the saturated zone of an aquifer. Filtration theory was applied to calculate collision efficiency (alpha) from model-derived attachment rates (katt), and the results are compared with those reported in the literature. The calculated alpha values vary by two orders-of-magnitude, depending on whether collision efficiency is estimated from the effective particle size (d10) or the mean particle size (d50). Collision efficiency values for MS-2 are similar to those previously reported in the literature (e.g. ) [DeBorde, D.C., Woessner, W.W., Kiley, QT., Ball, P., 1999. Rapid transport of viruses in a floodplain aquifer. Water Res. 33 (10), 2229-2238]. However, the collision efficiency values calculated for Bacillus subtilis spores were unrealistic, suggesting that filtration theory is not appropriate for theoretically estimating filtration capacity for poorly sorted coarse gravel aquifer media. This is not surprising, as filtration theory was developed for uniform sand filters and does not consider particle size distribution. Thus, we do not recommend the use of filtration theory to estimate the filter factor or setback distances. Either of the methods applied in this work (BTC or concentration vs. distance analyses), which takes into account aquifer heterogeneities and site-specific conditions, appear to be most useful in determining filter factors and setback distances.

Bacillus subtilis↗