MASTER'S THESIS - SuSanA
MASTER'S THESIS - SuSanA
MASTER'S THESIS - SuSanA
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4 Presentation of technologies for rural areas<br />
4.3.5.2 Unplanted drying bed<br />
An unplanted drying bed (see Figure 4.19) is a man-made drying bed with drainage layer and drainage pipe<br />
at the bottom, that collects liquids through the drainage system. The purpose is the dewatering of the<br />
sludge. The process reduces the sludge volume by 50 to 80 %. The sludge is not stabilised and needs further<br />
treatment (as well as the drained water). For desinfection, co-composting is possible (Tilley et al. 2008).<br />
Figure 4.19: Unplanted sludge drying bed (Tilley et al. 2008)<br />
Unplanted sludge drying beds are appropriate for small to medium size communes. Large space is required<br />
far away from the houses as odours and flies will occur. Advantages are that it is a low-cost treatment with<br />
moderate construction cost and no electricity requirements (Tilley et al. 2008).<br />
4.3.5.3 Planted drying bed<br />
Planted drying beds are similar to unplanted drying beds, but they are constructed with plants and<br />
ventilation pipes (see Figure 4.20). The appearance is therefore similar to vertical flow Cws. Roots facilitate<br />
the water to get out of the sludge as roots are growing through the sludge. Sludge is applied into a<br />
screening chamber, that is installed next to the drying bed. Purpose is the dewatering and stabilisation of<br />
the sludge, but no desinfection. Therefore, planted drying beds should be combined with co-composting.<br />
Sludge application can take place every three to seven days, sludge removal is necessary after two to three<br />
years (Tilley et al. 2008).<br />
Figure 4.20: Planted sludge drying bed (Tilley et al. 2008)<br />
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