MASTER'S THESIS - SuSanA

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5 Learning from already implemented CWs (in Albania and the Balkan region) An additional settling chamber was added during reconstruction works in 2010. The flow diagram for the wastewater treatment is given in Figure 5.5 (p. 59). Figure 5.5: Flow diagram of constructed wetland at SOS children’s village, Tirana (Gjinali et al. 2011) The raw wastewater is pre-treated in an Imhoff tank, which is located at the lowest point of the area, next to the pumping chamber and a second settling chamber that is used since first reconstruction. This construction is the result of using the old collection tank by reconstructing it to a Imhoff tank with second settling chamber and pumping chamber between Inhoff tank and settling chamber. Originally this re-use of already existing parts should help saving money. Figure 5.6: Imhoff tank and settling tank at the constructed wetland plant in November 2011 (Niebel 2011) 59
5 Learning from already implemented CWs (in Albania and the Balkan region) The pre-treated water is pumped to one of the two vertical filter beds, which are used alternately in a weekly rhythm. After passing the vertical filter bed, the water flows to the horizontal filter bed. Both stages, vertical and horizontal filters, are planted with aquatic plants. In the horizontal filter the bacterial pollution will be removed and treated wastewater can therefore be reused, e.g. for gardening. The cleaned water is stored in a collection tank next to the filter bed. Sludge from the Imhoff tank is taken out by opening a valve of the sludge pipe and using the physical pressure in the tank to press out the sludge through the pipe. Sludge is distributed evenly on a planted sludge drying bed that is located next to the Imhoff tank. Some of the water in the sludge will evaporate. The other part of the water that is infiltrating the sludge drying bed is collected with a drainage system in the bed and sent back to the Imhoff tank. As filter material the same sand was used in the horizontal and the vertical filter bed due to the fact that there was no other sand available. Sand came from Tirana and has a size of 0 - 2 mm with a k f -value of 5·10 -4 m/s ≤ k f ≤ 5·10 -3 m/s. To seal the filter bed to the ground, a geo-textile was used. Both vertical filter beds have a surface area of 165 m 2 each and a depth of 0.6 m. The horizontal filter bed has a surface area of 220 m 2 and contains in addition a 0.6 m wide stripe of gravel at both sides of the filter, one serves as inlet area and the other as outlet area. While the ground of the horizontal filter bed has a slope of 1 %, the surface is horizontal. Therefore the depth varies from 0.6 m to 0.83 m. The sludge drying bed has a surface area of 72 m 2 with thin sand layers of only 0.15 m, planted with the same plants as the filter beds. Dewatered stabilised sludge has to be removed every three to four years. Figure 5.7: Horizontal filter bed with only few vegetation in November 2011 (Niebel 2011) While both vertical filter beds show well growing aquatic plants, on the horizontal filter bed nearly no desired plantation is visible (see Figure 5.7, horizontal filter bed in front of the picture, the two vertical filter beds are on the left and right side of the visitors on the picture). This is caused by the fact that the plants were very small when planted and the roots did not reach the wastewater that was lead through the filter bed with a very low level (Nowak 2011,b). Water level in the horizontal filter is the same as in the shaft between horizontal filter and storage tank, which is determined by an effluent pipe with movable kneefitting and extension in the shaft. 60
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MASTER'S THESIS UIM/2011/7
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1 Problem Statement / Background At
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Bauhaus-University Weimar FACULTY O
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List of Abbreviations ADA ADF ALL A
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UNECE VF WB WFD WHO WRA WSP WSS WSS
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Table of content Preface...........
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5.3 Other constructed wetland plant
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Figure 5.15: Design of small size C
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1 Introduction 1.3 Milestones After
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2 Methodology • Edvin Pacara from
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2 Methodology interview as the auth
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3.1.4 Dam partly surrounding the fi
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4.3.6 4.3.7 4.3.8 PE-pressure pipe
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APPENDIX C - Site visits 1 Site vis
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APPENDIX C - Site visits 1.3 Wastew
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APPENDIX C - Site visits Figure C.1
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APPENDIX C - Site visits 4.3 Result
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APPENDIX C - Site visits The villag
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