Speaker
Description
Seepage water can occur when wood chips are stored outdoors. In relation to precipitation, the amount of seepage water is small. It contains high levels of dissolved organic matter. If such water enters surface waters, it could pose a threat to aquatic life. If the water seeps into humus-rich forest soils, microorganisms decompose the dissolved organic matter of the water quickly and thus filter them out. Unsealed pavements at storage yards don’t have a humus-rich and biologically active soil layer. Until now, the filtering effect of a storage area ground was unclear. To investigate this, wood chips were piled up on a gravel storage area and seepage water was collected and analyzed using lysimeters both above and below ground to a depth of 30 cm.
The experiment showed that the COD values (chemical oxygen demand) of the seepage water were significantly lower than in previous experiments. The values in the subsoil did not differ significantly from those on the surface. The BOD and TOC values (biological oxygen demand and total organic carbon) were also low. The reasons for the low COD values are not entirely clear. Possible influencing factors include the smaller size of the wood chip pile, dilution by precipitation water, biological degradation during the retention time in the collection container, and binding to calcium in the filter material of the lysimeters, although only a minor effect could be detected for the latter. No significant filtering effect of the subsoil was observed. There is no danger to soil organisms above the groundwater line from the seepage water because there is sufficient oxygen available. As a precautionary measure, it is recommended not to store wood chips outdoors at sites with very high groundwater levels.
| Keywords | Bioenergy; storage; leachate |
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