Bibliographies: 'Colmation layer'

1

Dizer, H., G. Grützmacher, H. Bartel, H. B. Wiese, R. Szewzyk, and J. M. López-Pila. "Contribution of the colmation layer to the elimination of coliphages by slow sand filtration." Water Science and Technology 50, no. 2 (2004): 211–14. http://dx.doi.org/10.2166/wst.2004.0127.

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River bank or slow sand filtration is a major procedure for processing surface water to drinking water in central europe. In order to model the performance of river bank and slow sand filtration plants, we are studying the different mechanisms by which the elimination of pathogens is realized. An important question concerning the mode of action of slow sand filters and river bank filtration units is the role of the colmation layer or “schmutzdecke” on the elimination of human pathogens. The schmutzdecke is an organic layer which develops at the surface of the sand filter short after the onset of operation. We have inoculated a pilot plant for slow sand filtration with coliphages and determined their rate of breakthrough and their final elimination. In the first experiment, with a colmation layer still missing, the breakthrough of the coliphages in the 80 cm mighty sandy bed amounted to ca. 40%. In contrast, less than 1% of coliphages escaped from the filter as the same experiment was repeated two months later, when a substantial colmation layer had developed. Our preliminary conclusions are that the colmation layer is extremely efficient in eliminating of viruses.

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2

Karpf, Christian, Jens Traenckner, and Peter Krebs. "Hydraulic modelling of sewage exfiltration." Water Science and Technology 59, no. 8 (2009): 1559–65. http://dx.doi.org/10.2166/wst.2009.172.

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Exfiltration of waste water in sewer networks represents a potential danger for the soil and the aquifer. Various modelling approaches have been proposed to quantify sewerage exfiltration and its spatial and temporal variation. Common models are based on the law of Darcy, extended by a more or less detailed consideration of the expansion of leaks, the characteristics of the soil and the colmation layer. In the paper investigations are introduced, which are focused on the actual water content of the soil and its influence on exfiltration rates. Modelling results with HYDRUS 1D show, that under unsaturated conditions initial exfiltration rates are increased compared to saturated conditions. In experiments it was found, that the matrix potential increases the tightness of the colmation layer. Further a colmation model was deduced, which allows the calculation of the thickness and conductivity of the colmation layer.

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3

Ellis, J. B., D. M. Revitt, J. Vollertsen, and D. J. Blackwood. "Sewer exfiltration and the colmation layer." Water Science and Technology 59, no. 11 (2009): 2273–80. http://dx.doi.org/10.2166/wst.2009.271.

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Sewer rig studies demonstrate a rapid exponential decline in exfiltration rates from gaps and joints to establish an ultimate steady-state equilibrium varying between 10−3–10−6 l s−1, with minimum average daily rates per standardised leak area and sewer length varying between 0.02–9.0 l d−1cm−2 and 0.0002–2.0 l s−1 km−1 respectively. These loss rates are much larger than those derived from indirect monitoring/modelling studies which suggest losses between 1.4 × 10−5–0.179 l s−1 km−1. The confusion regarding conflicting definitions of the colmation, transition, bridging and biofilm layers is addressed, and the significance of these clogging layers in terms of both hydraulic and matrix potential on the exfiltration loss is evaluated. The influence of variability and instability of flow and bed turbulence on determining critical leakage conditions following the onset of equilibrium steady-state is assessed. This challenges the generally held assumption that elevated head pressure condition alone is a necessary precursor for rupture of the clogging layers.

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4

Brunke, Matthias. "Colmation and Depth Filtration within Streambeds: Retention of Particles in Hyporheic Interstices." International Review of Hydrobiology 84, no. 2 (1999): 99–117. http://dx.doi.org/10.1002/iroh.199900014.

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AbstractColmation refers to the retention processes that can lead to the clogging of the top layer of channel sediments and decolmation refers to the resuspension of deposited fine particles. Internal colmation, clogging of the interstices directly below the armor layer, may form a thin seal that disconnects surface water from hyporheic water by inhibiting exchange processes. The settling of particles under low flow conditions can cause external colmation. Colmated channel sediments are characterized by reduced porosity and hydraulic conductivity as well as by a consolidated texture. The term ‘depth filtration’ refers to the transport and storage of fine matrix sediments in interstitial layers. Depth filtration is of significance for the transport of colloidal and fine particulate inorganic as well as organic matter within the hyporheic interstices and into the alluvial aquifer. The role of depth filtration is assessed for the content (given in mg per liter) of matrix fine particles retained in the coarse framework sediment of a gravel‐bed river in Switzerland. Sediment samples were taken by freeze‐coring with liquid nitrogen down to 70 cm depth and by piezometers down to 150 cm depth. Seventy‐two percent of the mobile matrix fine particles were smaller than 0.1 mm and 50% were smaller than 0.03 mm. The content of fines tended to increase with depth, although higher accumulations were found at intermediate depths in sediments influenced by exfiltrating ground water. Interstitial detrital particles >90 μm showed vertical distribution patterns opposing those of total particles. These relationships revealed a differential significance of import, storage, and transport within three types of hydrological exchange zones (infiltration, horizontal advection, exfiltration) in the cross‐section of the stream.

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5

Karpf, Christian, and Peter Krebs. "A new sewage exfiltration model – parameters and calibration." Water Science and Technology 63, no. 10 (2011): 2294–99. http://dx.doi.org/10.2166/wst.2011.167.

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Exfiltration of waste water from sewer systems represents a potential danger for the soil and the aquifer. Common models, which are used to describe the exfiltration process, are based on the law of Darcy, extended by a more or less detailed consideration of the expansion of leaks, the characteristics of the soil and the colmation layer. But, due to the complexity of the exfiltration process, the calibration of these models includes a significant uncertainty. In this paper, a new exfiltration approach is introduced, which implements the dynamics of the clogging process and the structural conditions near sewer leaks. The calibration is realised according to experimental studies and analysis of groundwater infiltration to sewers. Furthermore, exfiltration rates and the sensitivity of the approach are estimated and evaluated, respectively, by Monte-Carlo simulations.

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6

Harvey, Ronald W., David W. Metge, Denis R. LeBlanc, et al. "Importance of the Colmation Layer in the Transport and Removal of Cyanobacteria, Viruses, and Dissolved Organic Carbon during Natural Lake-Bank Filtration." Journal of Environmental Quality 44, no. 5 (2015): 1413–23. http://dx.doi.org/10.2134/jeq2015.03.0151.

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7

Rakhimbayev, Shark M., Natalia M. Tolypina, Elena N. Khakhaleva, and Daniil A. Tolypin. "Comparative Resistance of Concrete with Aggregates and Fillers of Different Composition." Materials Science Forum 1017 (January 2021): 133–42. http://dx.doi.org/10.4028/www.scientific.net/msf.1017.133.

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The paper studies the influence of aggregates and fillers with negative and positive electrical surface properties on the corrosion resistance of concrete. The advantage of resistance of fine-grained concrete on marble sand in comparison with concrete on quartz sand, regardless of the type of aggressive environment, is established. At the same time, the stability of samples of powdered concrete with 10 and 30% of fine-grained filler changed little when replacing the quartz powder with marble one. It is shown that the resistance coefficients of powdered concrete samples with quartz filler (10%) do not differ from the resistance coefficients of samples of a similar composition with crushed marble filler, and with an increase in the dosage of the filler (30 %) slightly exceed. It was found that in powder concretes without aggregates, the contact layer between the cement matrix and the aggregate is absent, so the composition of the mineral powder plays a much smaller role in the corrosion processes of cement stone. The obtained results allowed establishing that electrokinetic phenomena play a secondary role, and the main influence on the stability of fine-grained concrete is the processes of pore colmation by chemical reactions, as well as the interaction of the surface layers of the aggregate with the cement matrix.

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8

Rakhimbayev, Shark M., Natalia M. Tolypina, Elena N. Khakhaleva, and Daniil A. Tolypin. "Comparative Resistance of Concrete with Aggregates and Fillers of Different Composition." Materials Science Forum 1017 (January 2021): 133–42. http://dx.doi.org/10.4028/www.scientific.net/msf.1017.133.

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The paper studies the influence of aggregates and fillers with negative and positive electrical surface properties on the corrosion resistance of concrete. The advantage of resistance of fine-grained concrete on marble sand in comparison with concrete on quartz sand, regardless of the type of aggressive environment, is established. At the same time, the stability of samples of powdered concrete with 10 and 30% of fine-grained filler changed little when replacing the quartz powder with marble one. It is shown that the resistance coefficients of powdered concrete samples with quartz filler (10%) do not differ from the resistance coefficients of samples of a similar composition with crushed marble filler, and with an increase in the dosage of the filler (30 %) slightly exceed. It was found that in powder concretes without aggregates, the contact layer between the cement matrix and the aggregate is absent, so the composition of the mineral powder plays a much smaller role in the corrosion processes of cement stone. The obtained results allowed establishing that electrokinetic phenomena play a secondary role, and the main influence on the stability of fine-grained concrete is the processes of pore colmation by chemical reactions, as well as the interaction of the surface layers of the aggregate with the cement matrix.

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9

Gunkel, G., C. Beulker, B. Grupe, and F. Viteri. "Survey and assessment of post volcanic activities of a young caldera lake, Lake Cuicocha, Ecuador." Natural Hazards and Earth System Sciences 9, no. 3 (2009): 699–712. http://dx.doi.org/10.5194/nhess-9-699-2009.

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Abstract. Cuicocha is a young volcano adjacent to the inactive Pleistocene Cotacachi volcano complex, located in the western cordilleras of the Ecuadorian Andes. A series of eruptions with intensive ash emission and collapse of the caldera occurred around 4500–3000 y BP. A crater 3.2 km in diameter and a maximum depth of 450 m was formed. Further eruptions of the volcano occurred 1300 y BP and formed four smaller domes within the caldera. Over the last few hundred years, a caldera lake has developed, with a maximum depth of 148 m. The lake water is characterized by sodium carbonate with elevated concentrations of manganese, calcium and chloride. Nowadays, an emission of gases, mainly CO2, and an input of warm spring water occur in Lake Cuicocha. The zone of high activity is in the western basin of the lake at a depth of 78 m, and continuous gas emissions with sediment resuspension were observed using sonar. In the hypolimnion of the lake, CO2 accumulation occurs up to 0.2% saturation, but the risk of a limnic eruption can be excluded at present. The lake possesses monomictic stratification behaviour, and during overturn an intensive gas exchange with the atmosphere occurs. Investigations concerning the sedimentation processes of the lake suggest only a thin sediment layer of up to 10–20 cm in the deeper lake basin; in the western bay, in the area of gas emissions, the lake bottom is partly depleted of sediment in the form of holes, and no lake colmation exists. Decreases in the lake water level of about 30 cm y−1 indicate a percolation of water into fractures and fissures of the volcano, triggered by a nearby earthquake in 1987.

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10

Borovyk, М. V., А. P. Vovk, and М. V. Gordijchuk. "Colmatating of productive gas formations while drilling wells with abnormally lower hydrostatic pressures." Prospecting and Development of Oil and Gas Fields, no. 4(81) (December 28, 2021): 16–23. http://dx.doi.org/10.31471/1993-9973-2021-4(81)-16-23.

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Today the pressures in productive gas collectors on the Dnieper-Donets rift are considerably lower than hydrostatic ones. Opening such formations while drilling is a challenging task in terms of preventing losses and differential pressures. In order to solve the problem, one needs to improve the methods of effective temporary colmation of productive formations with acid-soluble materials under the conditions of abnormally low formation pressures during drilling on fields with late terms of development. Traditional algorithms of lost circulation control in abnormally low reservoir pressure, developed by leading world services companies, often turn out to be unworkable. In order to conduct the lost circulation control, one often chooses colmatants, which totally align with the principles of ideal packaging, however do not meet the criterion of strength or resistance to significant differential pressure. As a result, in the course of the subsequent drilling there can be another circulation loss in already colmated layer. In Ukraine the lost circulation control sphere is being developed by means of selecting colmatants according to a new principle. The article has proposed the activities for the lost circulation curing and pollution reducing of productive collectors. For this purpose the generalized characteristic-criterion of colmatants has been developed and used. The criterion got a name “flexibility”, i.e. a deformation, compaction and penetration (into porous-fissured medium) capability under immense pressure. With the help of the criterion the set of particular colmatant have been chosen; also, principles of colmatant mixtures selection under the relevant geological and mining conditions have been identified. In many cases, there is no need to calculate the physical parameters of the formation and the circulation loss crack due to flexibility of colmatant; one only has to select the optimal concentrations of materials and the periodicity of input these materials to the mud. The developed technology confirms the need to improve the algorithms for circulation loss prevention and curing, primarily for conditions of abnormally low reservoir pressures.

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Academic literature on the topic 'Colmation layer'

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Journal articles on the topic "Colmation layer"

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