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  • 1
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, April 5, 2012, Vol.399, p.35(6)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.colsurfa.2012.02.021 Byline: Doreen Zirkler, Friederike Lang, Martin Kaupenjohann Keywords: Soil colloid; Vacuum filtration; Centrifugation; Particle size separation Abstract: Display Omitted Author Affiliation: TU Berlin, Department of Soil Science, Ernst-Reuter-Platz 1, 10587 Berlin, Germany Article History: Received 28 October 2011; Revised 2 February 2012; Accepted 17 February 2012
    ISSN: 0927-7757
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 05 April 2012, Vol.399, pp.35-40
    Description: ► Colloid recovery after filtration and centrifugation of soil suspensions was measured. ► Colloid recovery after filtration is 50–97% of the recovery after centrifugation. ► Cellulose nitrate filters retain colloids without losing permeability. ► Recovery of mineral colloids after filtration is less than recovery of organic colloids. ► We recommend centrifugation for soils with colloids of similar density. Soil colloid science requires the separation of the colloids from larger particles in suspensions, which is frequently achieved by filtration. However, the results of filtration may be biased due to (i) pore clogging and (ii) the formation of a filter cake. In order to quantify these effects, we filtrated different volumes of soil suspensions containing mainly mineral (M), mainly organic (O) or mineral and organic (MO) colloids through 1.2 μm membranes. Turbidity and the concentrations of colloid-bound C, Si and Al were measured in the filtrates and, as a reference, in centrifugates of the suspensions. To exclude the influence of the filter cake and examine only pore clogging effects, we conducted the same filtration experiment with suspensions which have been pre-treated by a centrifugal elimination of particles 〉3 μm. Finally, we scanned a membrane after filtration with an electron microscope for the visualisation of possible pore clogging. Turbidity and concentrations of colloid-bound Al and Si in the filtrates of the pre-treated suspensions were one order of magnitude lower than in centrifugates. This discrepancy was most pronounced for M suspensions which indicates that filters preferentially remove mineral colloids. Microscope images revealed no sign for pore clogging and smaller filtrated suspension volumes did not lead to more colloid recovery in pre-treated filtrates. We assume that the colloids are retained within the thick, multilayered structure of the filter without clogging the main pores. When filter cakes are forming (experiment without previous centrifugation), turbidity and concentrations of colloid-bound Al, Si and C decrease with increasing filtration volume. However, the retaining effect of filter cakes seems negligible compared to the retaining effect within the filter. We conclude that the composition of soil colloidal suspensions depends significantly on the technique which is used to remove larger particles. Filtration underestimates the amount of colloids in suspension and centrifugation should be preferred as separation method at least for soils with colloids of similar density, either M or O.
    Keywords: Soil Colloid ; Vacuum Filtration ; Centrifugation ; Particle Size Separation ; Engineering ; Chemistry
    ISSN: 0927-7757
    E-ISSN: 1873-4359
    Source: ScienceDirect Journals (Elsevier)
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  • 3
    Language: English
    In: Colloids and surfaces, 2012, Vol.399, pp.35-40
    Description: Soil colloid science requires the separation of the colloids from larger particles in suspensions, which is frequently achieved by filtration. However, the results of filtration may be biased due to (i) pore clogging and (ii) the formation of a filter cake. In order to quantify these effects, we filtrated different volumes of soil suspensions containing mainly mineral (M), mainly organic (O) or mineral and organic (MO) colloids through 1.2μm membranes. Turbidity and the concentrations of colloid-bound C, Si and Al were measured in the filtrates and, as a reference, in centrifugates of the suspensions. To exclude the influence of the filter cake and examine only pore clogging effects, we conducted the same filtration experiment with suspensions which have been pre-treated by a centrifugal elimination of particles 〉3μm. Finally, we scanned a membrane after filtration with an electron microscope for the visualisation of possible pore clogging. Turbidity and concentrations of colloid-bound Al and Si in the filtrates of the pre-treated suspensions were one order of magnitude lower than in centrifugates. This discrepancy was most pronounced for M suspensions which indicates that filters preferentially remove mineral colloids. Microscope images revealed no sign for pore clogging and smaller filtrated suspension volumes did not lead to more colloid recovery in pre-treated filtrates. We assume that the colloids are retained within the thick, multilayered structure of the filter without clogging the main pores. When filter cakes are forming (experiment without previous centrifugation), turbidity and concentrations of colloid-bound Al, Si and C decrease with increasing filtration volume. However, the retaining effect of filter cakes seems negligible compared to the retaining effect within the filter. We conclude that the composition of soil colloidal suspensions depends significantly on the technique which is used to remove larger particles. Filtration underestimates the amount of colloids in suspension and centrifugation should be preferred as separation method at least for soils with colloids of similar density, either M or O. ; p. 35-40.
    Keywords: Colloids ; Filtrates ; Centrifugation ; Filtration ; Aluminum ; Turbidity ; Soil Colloids ; Silicon ; Filter Cake ; Soil
    ISSN: 0927-7757
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 4
    Language: English
    In: Biomass and Bioenergy, August 2014, Vol.67, pp.89-98
    Description: Biogas production and the amount of thereby incurred digestates increased remarkably in the last decade. Digestates should be used as soil fertilizers to close nutrient cycles. However, knowledge about the elemental composition of digestates from biogas production and element losses or accumulations during fermentation process is insufficient so far. Intending to enlarge the database for the elemental composition of digestates and to investigate element in- and outputs of biogas fermenters, we measured the concentrations of C, N, P, K, S, Ca, Mg, Fe, Mn, Zn, Cu, Pb, Cd, Ni, Mo and Se of digestates and feedstock (ingestates) of four full-scale biogas plants in Germany monthly over a one year period. Ingestates were sewage sludge, fat and mash (SEW1), sewage sludge and fat (SEW2), pig slurry, treacle and food residues (SL) and maize silage (M). We developed a statistical method to calculate the number of required sampling dates which have to be integrated for the calculation of reliable element budgets between ingestates and digestates for the case when information about the amount and composition of the produced biogas is not available. Our results suggest that two (SEW2), five (SEW1, M) and 10 (SL) sampling dates had to be integrated for reliable balances. All fermenters revealed losses of N, most likely due to volatilization of NH . Losses of S (probably H S), Mg (precipitation of struvite), Cd and Zn (precipitation of sulfides) could be detected in some cases. Iron and Mn accumulations can be attributed to attrition of the stirrer.
    Keywords: Digestate ; Heavy Metals ; Nutrients ; Biogas Plant Feedstock ; Element Balance ; Element Recovery ; Engineering ; Environmental Sciences
    ISSN: 0961-9534
    E-ISSN: 1873-2909
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  • 5
    Language: English
    In: 2015
    Keywords: Calcium ; Zinc ; Fertilizers ; Feedstocks ; Magnesium ; Heavy Metals ; Selenium ; Copper ; Lead ; Nutrients ; Manganese ; Iron ; Nitrogen ; Biogeochemical Cycles ; Volatilization ; Molasses ; Digestate ; Carbon ; Molybdenum ; Cadmium ; Fermentation ; Pig Manure ; Magnesium Ammonium Phosphate ; Fermenters ; Biogas Plant Feedstock ; Biogas ; Anaerobic Digestion ; Elemental Composition ; Ammonia ; Phosphorus ; Hydrogen Sulfide ; Element Recovery ; Sewage Sludge ; Element Balance ; Corn Silage ; Databases ; Potassium ; Nickel ; Sulfur ; Soil
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 6
    Language: English
    In: Soil Science Society of America Journal, 2015, Vol.79(6), p.1684(9)
    Description: Digestates from biogas plants provide valuable crop nutrients, such as P. Plant uptake of anions like PO43? causes an alkalinization of the rhizosphere due to release of HCO3?. We investigated the transport of P to an anion sink simulating the anion exchange activity of a plant root in digestate-amended soils and hypothesized that the HCO3? source induces enhanced mineralization of organic P. We expected this effect to strengthen with decreasing distance from the HCO3? source. Anion exchange resins (AERs) saturated with HCO3? were used in an incubation experiment. Available PO4uP was measured in 10 slices of the soiludigestate mixtures (1 mm each) after 2, 8, and 32 d and in the resin and total uncut samples after 2, 4, 8, 16, 32, and 64 d of incubation. Anion exchange resins increased pH by 2 to 3 units. Concentrations of available PO4uP in the uncut samples increased within 4 d, which we attribute to enhanced microbial P mineralization activity. Afterward, PO4uP concentrations decreased within 4 d, which we attribute to precipitation of calcium phosphate due to further increasing pH. Concentrations of PO4uP were lowest near the AER and showed a peak migrating away from the resin with time. A new model linking diffusive transport and mineralization intensity of organic matter as a function of distance from AER could well describe the observed spatial PO4uP distribution and accumulation in the resin. However, further studies are needed to account for mechanisms like precipitation in models for P transport.
    Keywords: Digestants – Research ; Fossilization – Research ; Rhizosphere – Research
    ISSN: 0361-5995
    E-ISSN: 14350661
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  • 7
    Language: English
    Description: Die Biogasbranche ist in den letzten Jahren stark expandiert und produziert große Mengen von Gärresten, die zur Schließung von Nährstoffkreisläufen auf landwirtschaftliche Flächen ausgebracht werden sollten. Bislang sind die Kenntnisse über die Zusammensetzung der Gärreste und ihre Wirkung im Boden, vor allem in wurzelbedingt alkalischem Milieu, jedoch nicht ausreichend. Die Ziele dieser Arbeit waren daher (1) die Bestimmung der Elementzusammensetzung verschiedener Gärreste (aus Klärschlamm, Gülle oder Mais), insbesondere die zeitliche Variabilität and Veränderung während der Fermentation, (2) die Untersuchung der Wirkung von Gärresten auf die organische Bodensubstanz (OBS) unter künstlichen wurzelnahen Bedingungen und (3) die Prüfung, ob der Anionenaustausch durch eine Modellwurzel die P-Verfügbarkeit in einem mit Gärrest gedüngten Boden erhöht. Zur Erreichung dieser Ziele wurden Elementanalysen von Gärresten und ihrem Ausgangsmaterial über ein Jahr zusammen mit einer anschließenden Elementbilanzierung vorgenommen, sowie Inkubationsexperimente mit Gärresten, Böden und Anionenaustauscherharzen als Modellwurzeln durchgeführt. Die Gärreste wiesen eine große Variabilität in Abhängigkeit von ihrem Ausgangsmaterial, aber auch über die Zeit auf. Für eine Elementbilanzierung vom Ausgangsmaterial zum Gärrest sind je nach Gärrest zwei, fünf oder zehn Beprobungstermine erforderlich, um verlässliche Aussagen treffen zu können. Die Bilanzierung ergab eine Abreicherung von Stickstoff (N), Schwefel (S), Magnesium (Mg), Zink (Zn) und Cadmium (Cd) während der Vergärung, vermutlich durch... ; The recently growing biogas sector generates large amounts of by-products, the digestates, which should be applied to arable land in order to recycle valuable nutrients. However, knowledge about the composition of digestates and their fate in soils, especially under root-caused alkaline conditions, is not sufficient so far. Thus, the aims of this thesis were (1) to examine the elemental composition of different digestates (from sewage sludge, slurry or maize), especially the temporal variability and alteration during fermentation, (2) to investigate the effects of digestates on soil organic matter (SOM) under artificial rhizosphere conditions and (3) to test whether the anion exchange of a model root would increase P availability in a digestate amended soil. These objectives were pursued by a one-year analysis of digestates and their feedstock with subsequent element balancing and by incubation experiments with digestates and soil including anion exchange resins as root models. Digestates showed a great variability depending on their feedstock but also over time. For an element balancing from feedstock to digestate, two, five or ten sampling dates depending on the particular digestate were needed for reliable results. During fermentation, depletions of nitrogen (N), sulphur (S), magnesium (Mg), zinc (Zn) and cadmium (Cd) were determined, probably due...
    Keywords: Naturwissenschaften Und Mathematik ; Biogas-Gärrückstände ; Mineralisierung ; Organische Bodensubstanz ; Phosphor ; Biogas Residues ; Mineralisation ; Phosphorus ; Soil Organic Matter
    Source: DataCite
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  • 8
    Language: German
    Keywords: Biogasanlage ; Großtechnische Anlage ; Gärrest ; Bodenchemie ; Humus ; 48.32 Bodenkunde, Bodenbewertung ; 58.30 Biotechnologie ; 58.17 Chemische Prozeßtechnik ; Horticulture
    Source: DataCite
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