Browsing by Author "Nzabuheraheza, Francois Dominicus"

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    Performance of constructed wetland coupled with dynamic roughing filter in the treatment of mixed wastewaters: a case of two Macrophytes planted in Series
    (University of Dar es Salaam, 2007) Nzabuheraheza, Francois Dominicus
    A study of BOD5 removal from wastewater in coupled Dynamic Roughing Filter (DRF) and Horizontal Subsurface Flow Constructed Wetland (HSSFCW) system was carried out at the University of Dar es Salaam, which is located at latitude 6° 48' S and longitude 39° 13' E. The overall objective was to assess the performance of the DRF-HSSFCW treating mixed wastewaters using two macrophytes planted in series (Cyperus papyrus and Phragmites maurif ianus). The mixture re was made of domestic waste from the University of Dar es Salaam main campus (80 %), Kimara abattoir wastewater (10 %), and Mwenge soft drinks wastewater (I0 %). The overall BODs removal in DRF¬ HSSFCW system was 92%. The BOD5 concentration in CW effluent was about 28 mg/l, Which is within the recommended effluent standards (TBS, 1989; FAO, 1997; WHO 1998). This high performance was attributed to a number of factors, namely the removal of mainly suspended solids (removal efficiency of about 64 %) in the DRF and C. papyrus and P. mauritianus roots, which were weaved together in CW and hence provided a good filter mat and a better bacterial attachment. Optimum parameters for design of DRF system were found to be: (i) low flow rate (Q, = 0.50 m3/m2 .day), (ii) small gravel size (Gs) of 12-18 mm (gravel diameter), and (iii) big filter media thickness (Gt) of 25 cm. In the HSSFCW, the optimum removal efficiency of BOD5 (80 %) was obtained with a flow rate of 0.060 m3/m2 .day. Mathematical model estimated removal efficiency of about 92 % BODs. Thus the model was considered to be an appropriate tool for system design and prediction of BOD, removal in the above treating mixed wastewater in tropical condition.