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Assessment of a Moisture Application System for Compost Biofilters

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1009176.(doi:10.13031/2013.29821)
Authors:   Lucas Dutra de Melo, George B Day, Joe L Taraba, Guilherme Del Nero Maia
Keywords:   Keywords: Biofilter, compost, drying rate, moisture application, soaker hose

Moisture content is a key physical property for organic media in biofilters. It can affect both its efficiency and useful life. Therefore, it is important to understand the drying process of the media and from there, to design a moisture control system. The present work intends to estimate the shape of the drying front that advances through an upflow biofilter. Three pilot-scale biofilters (0.6m x 0.81m x 0.61m) were filled with sieved compost at 90% of its water holding capacity and subjected to an air flow rate of 8.7 m/s for drying. Samples were collected at random positions in each of three levels every 12 hours during this process and analyzed using the standard oven moisture method. This procedure was set up to determinate the shape of the drying front within the media stack. The initial moisture content (wb) of biofilters 1, 2, & 3 were 40%, 41%, and 44% respectively. The lower level(s) dried the fastest to reach final moisture contents of 11%, 11% and 13% for biofilter 1, 2 and 3 respectively. These values were achieved at 31, 55 and 62 hrs for the lower, middle, and upper levels of the biofilters. The results support a drying front which leaves a conical moisture area within the media owing to the difference in the drying rate for each level. This indicates different water requirements for different levels; therefore the need for soaker hoses is position-dependent within the biofilter. Water to maintain media moisture can be delivered to the biofilter with a calibrated soaker hose. Six meters of soaker hose were calibrated to determine water flow as a function of pressure. The hoses were allowed to flow for 3 minutes, with pressure varying from 27.6 kPa to 124.1 kPa in 13.8 kPa increments. The volume was measured at the end of each period. . Linear regression of the hose calibration data provided flow as a function of pressure with an R2 of 0.97.

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