Browsing by Author "Mziray, Nuru Ressa"

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    Treatment of sisal wastewater using constructed wetlands in Tanzania
    (University of Dar es Salaam, 2010) Mziray, Nuru Ressa
    Investigation of the sisal wastewater treatment by using constructed wetland was undertaken at Highlands Sisal Estate located in Ubena Zomozi Ward, Coast Region, and Tanzania. Two subsurface flow constructed wetlands (CW1- planted with Phragmites mauritianus and CW2-unplanted) of equal size (0.6 m long, 0.4m wide and 0.4 m high) were receiving pre-treated sisal wastewater from a Dynamic Roughing Filter (DRF) unit (0.42m long, 0.4m wide and 0.4 m high) at a flow rate of 0.01 m3/day. The hydraulic retention time of the DRF and CW were 2 hrs and 7 days, respectively. Effluent samples were taken for analysis of BOD5, TSS and Turbidity so as to quantify the treatment efficiencies. The respective observed percentage of pollutants removal for DRF, CW1 and CW2, were: BOD5 -30.96, 71.24 and 52.61; TSS- 35.04, 74.70 and 67.47; Turbidity- 34.65, 49.09 and 46.25. By using Stella II software (STELLA®8.1.1) and data from CW1 and CW2, a model for removal of organic carbon in the CW was developed, calibrated and validated. Model results indicated that the main processes for removal of organic carbon were uptake by plants and growth of heterotrophic bacteria (uptake), oxidation and sedimentation. The model developed can be used for predicting the future performance of the ecosystem. This study concluded that the use of subsurface flow constructed wetlands for treatment of pre-treated sisal wastewater is feasible. There was good performance in treatment of important parameters such as pH, BOD5, TSS and Turbidity. It is recommended that for optimization of system treatment performance with respect to BOD5 and TSS removal, a primary treatment system need to be used prior to the CW in order to meet acceptable Tanzanian wastewater discharge standards.