Gaseous Oxygen Uptake in Porous Media at Different Moisture Contents and Airflow Velocities

• The presence and distribution of water in the pore space isa critical factor for flow and transport of gases throughunsaturated porous media. The water content also affectsthe biological activity necessary for treatment of pollutedgas streams in biofilters. In this research, microbial activityand quantity of inactive volume in a porous mediumas a function of moisture content and gas flow rate wereinvestigated. Yard waste compost was used as a test medium,and oxygen uptake rate measurements were used toquantify microbial activity and effective active compostvolume using batch and column flow-through systems.Compost water contents were varied from air-dry to fieldcapacity and gas flows ranged from 0.2 to 2 L min1. Theresults showed that overall microbial activity and therelative fraction of active compost medium volume increasedwith airflow velocity for all levels of water contentup to a certain flow rate above which the oxygen uptakerate assumed a constant value independent of gas flow.The actual value of the maximum oxygen uptake rate wascontrolled by the water content. The oxygen uptake ratealso increased with increasing water content and reacheda maximum between 42 and 48% volumetric water content,above which it decreased, again likely because offormation of inactive zones in the compost medium.Overall, maximum possible oxygen uptake rate as a functionof gas flow rate across all water contents and gas flowscould be approximated by a linear expression. The relativefraction of active volume also increased with gas flowrate and reached approximately 80% for the highest gasflows used.

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NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Oceanografi, hydrologi och vattenresurser (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Oceanography, Hydrology and Water Resources (hsv//eng)

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