Browsing by Author "Mgimba, Christopher"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    Evaluation of the potential of constructed wetland for the removal of chromium and cod from tannery wastewater-a case of Kibaha Tanneries
    (University of Dar es Salaam, 2010) Mgimba, Christopher
    This study was aimed at evaluating the potential of the constructed wetland in the removal of chromium from the tannery wastewater and establishing the mechanisms through which chromium is removed from the wastewater. The experiment was carried out in the experimental HSSFCW system which consisted of two cells. One of the cells was planted with Phragmites mauritianus and the other cell was used as a control for the study. The solution of chromium with the concentration of 150mg/l was made by dissolving chromium powder [Cr2(SO4)3] in the water from stabilization pond. The water samples were collected at an interval of four days and were analysed for various parameters including chromium, chemical oxygen demand (COD), temperature, pH and electric conductivity (EC).The study showed that at stage where the low level of chromium removal was almost uniform, the planted cell achieved chromium removal efficiency of 99.94% while in the control cell was 87.89%. The COD removal efficiency in the planted cell was 93.93% and in the control cell it was 87.38%. The chromium mass balance was determined and the results showed that out of the total chromium removed, 91.14% removed through precipitation on gravels and on the root surfaces, and only 5.44% was removed through plants uptake. The results suggest that chromium (III) in the constructed wetland is mainly removed by precipitation, and the largest proportion was precipitated on the gravels. Therefore, this study recommends for the development of full scale model constructed wetlands for treating wastewater from tanneries. It recommends for further investigation on the enhancement of the chromium precipitation in form of sulfide by incorporating microorganisms.