Moisture percolation

Subsurface runoff. When precipitation hits the land surface, the vast majority does not go directly into the network of streams and rivers in fact, it may be cycled several times before ever reaching a river and the ocean. Instead, most precipitation that is not intercepted by the vegetation canopy and re-evaporated infiltrates into the soil, where it may reside as soil moisture, percolate down to ground-water, or be transpired by plants. 

One of the most widely used spray-drying techniques for coffee extract involves spraying percolated coffee extract at 40°F into the top of a baffled tower of hot air at 480°F initially. The cooler wet air is removed toward the bottom of the tower and finally a powder of the coffee extract solids leaves the tower at about 90°F. These solids are in the form of hollow beads and contain 3% moisture. 

The harmful liquid that collects at the bottom of a landfill is known as leachate. The generation of leachate is a result of uncontrolled runoff, and percolation of precipitation and irrigation water into the landfill. Leachate can also include the moisture content initially contained in the waste, as well as infiltrating groundwater. Leachate contains a variety of chemical constituents derived from the solubilization of the materials deposited in the landfill and from the products of the chemical and biochemical reactions occurring within the landfill under the anaerobic conditions. 

Modeling The numerical model UNSAT-H was used to predict the annual and cumulative percolation through the cover. The model was calibrated with 12 months of soil moisture content and weather data. Following calibration, UNSAT-H predicted a cumulative percolation of 50 cm for the ET cover and 95 cm for a conventional cover over a 10-year period. The model predicted an annual percolation of approximately 0 cm for both covers during the first year. During years 3-10 of the simulation, the model predicted less annual percolation for the ET cover than for the conventional cover. 

Performance data Percolation is being measured with a lysimeter connected to flow monitoring systems, soil moisture is being measured with water content reflectometers, and soil matric potential and soil temperature are being monitored with heat dissipation units. From November 1999 to July 2002, the capillary barrier cover system had a cumulative percolation of 0.5 mm. Total precipitation was 837 mm over the 32-month period. Additional field data were collected through 2005. 

The ALCD has collected data on percolation using lysimeters and soil moisture to monitor cover performance. Total precipitation (precip.) and percolation (perc.) volumes based on 5 years of data are provided in Table 25.6. The ET covers generally have less percolation than the Subtitle D cover for each year shown. More information on the ALCD cover performance can be found in Dwyer.39... 

Table 54—Percentage Distribution of Moisture Left in Columns of Sand after Percolation Had Continued for 2 and One-half Years (King 1899)...

Wet heating is more effective for bran stabilization for oil extraction than is dry heating. Lipase is inactivated in 3 minutes at 100°C (37). The equipment that can be used include steam cookers, blanchers, autoclaves, and screw extruders with injected steam and water (30). Extrusion with steam injection and up to 10% added water reduces the temperature required for lipase inactivation. Temperatures are reduced to 100-120°C. Product may be held at 100°C for 1.5-3.0 minutes before drying to a stable moisture content. Bran expands as it exits the extruder, and water flashes to steam (8). Porous pellets assist in solvent percolation during oil extraction. Fines are agglomerated as well. 

The concentration of natural, dissolved organic carbon (DOC) content in the soil moisture of shallow soils is often 5 to 10 ppm. This DOC may percolate downward in the unsaturated zone, perhaps in association with colloidal-sized clay particles. Its aerobic bacterial oxidation can produce increasing amounts of CO2 with depth (cf. Wood and Petraitis 1984 Wood 1985). 

Once moisture has penetrated into the piles, there is little evaporation from any appreciable depth. Taking a conservative viewpoint, evaporation was considered to be zero, so that the net water available to percolate through the phosphogypsum remains 122 cm/year for a normal year. 

By contrast, the ECP must have conjugated rigid-rod macromolecules. Several such polymers show high electrical conductivity (usually after doping), viz. polyacetylene (PAc), polyaniline (PANI), polypyrrole (PPy), polyparaphenylenes (PPP), or poly-3-octyl thiophene (POT). The resins are expensive, difficult to process, brittle and affected by ambient moisture, thus blending is desirable. For uniaxially stretched fibers the percolation threshold is 1.8 vol%, hence low concentration of ECP (usually 5-6 vol%) provides sufficient phase co-continuity to ascertain conductivity similar to that of copper wires (see Table 1.79). 

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