Authors: Ima, C.S. And D.D. Mann
Download file: https://library.csbe-scgab.ca/docs/journal/53/C0813.pdf
Published in: CBE Journal » CBE Journal Volume 53 (2011)
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Description: Biofilter media are subject to continuous variation in. moisture content. Movement of air through the biofilter causes. drying of the media to the extent that biofiltration would be. inefficient. Water is added to increase the moisture content to the. required levels. The cycle of drying and wetting is repeated on a. daily basis. Tests were conducted to measure the variation in. lateral pressure caused by these wetting and drying cycles in. model bins using woodchips as the medium. Three model. biofilter bins (0.5m by 0.5m, and 1.2 m tall) were used. Lateral. pressures were measured with flat metal diaphragm transducers. mounted on the bin wall at 0.2, 0.5, 0.7, and 0.9 m above the bin. floor while moisture content was measured with relative humidity. sensors located at 0.2, 0.6, and 1.0 m above the bin floor.. A metric ruler was used to measure the amount of settling of the. media that occurred after each cycle. Wetting of the material was. achieved by surface irrigation using a watering can. A ventilation. fan was used as a means of facilitating the drying phase. Five. wetting and drying cycles were examined. The results showed. that both lateral pressure and amount of settling increased as the. number of wetting and drying cycles increased. Analysis of. variance (Duncan's test) performed at the 5% error rate showed. significant differences (PB0.0001) between pressure values. observed in the different cycles at each transducer location for. the three bins. The greatest value of lateral pressure in each cycle. was observed near the bottom of the bin (i.e., at the 0.2 m. location) whereas the greatest pressure increase as well as the. greatest overpressure factors in bins 1, 2, and 3 occurred at. 0.7, 0.5, and 0.7 m locations, respectively. Multiple regression. analysis was used to generate a prediction model that estimated. peak lateral pressure as a function of media moisture content,. bulk density, and height.
Keywords: lateral pressure, variation, biofilter, woodchips, wetting and drying cycles, media settling
Citation: Ima, C.S. and D.D. Mann. 2011. Lateral pressure variation in a model biofilter due to wetting and drying cycles. Canadian Biosystems Engineering 53:6.1-6.7