Browsing by Author "Mlay, Happiness"

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    Acid Mine drainage (AMD) treatment using constructed wetlands
    (University of Dar es Salaam, 2005) Mlay, Happiness
    A study on the performance of a constructed wetland to treat Acid Mine Drainage (AMD) was carried out in two Horizontal Sub-surface Flow (HSSF) constructed wetlands; one planted with Typha domingensis plants and an unplanted cell used as a control. The wetlands were located at the University of Dar es Salaam (Main Campus). Both units were packed with limestone gravel as substrate and were divided into four equally sized sections along the length: the inlet zone, two central zones and outlet zone. Removal efficiencies of metals and sulphate as well l as change in pH (alkalinity generation) in water were used as performance indicators. It was found that pH increased by about 65 % (from around 4.5-6.0 to about 7.0-8.0), alkali nity generation was almost the same for both cells at about 44.4 % and 44.8 % of the influent akalinity from Typha system and control system, respectively. Sulphate was removed by about 91. I % in the planted wetland and by about 87 % in the control wetland. Copper was removed by 99. l % in the planted wetland and by 72.4 % in the control unit. The retention of copper in planted wetland was about 68% of the initial value and in substrate was about 51 .2 % and 44% of the initial values for Typha un it and control un it, respectively . A dynamic biogeochem ical model was developed by use of the STELLA software version 6.0.1. The model uses different processes to describe the transformation of copper in different compartments and simulates abilities of constructed wetlands to treat Acid Mine Drainage. The results showed that a constructed wetland can be used to treat acid mine drainage.
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    A study on the process of modifying plant oils for rural liquid biofuel in Tanzania
    (University of Dar es Salaam, 2015) Mlay, Happiness
    A study on the process of modifying plant oil (PO) to produce a liquid biofuel, that has similar specifications of diesel fuel grade 4-D for use in low- and medium speed diesel engines was carried out. These engines are commonly used in rural areas for many socio-economic activities. PO’s chemical composition is the major factor that affects diesel engine performance and was the basis for modification. PO samples under study were: Jatropha curcas L. (JO), Croton Megalocarpus (CROT), Ricinus communis (CST) and Excoecaria bussei (EIX) seed oils. PO Modification was carried out in the laboratory and involved degumming, neutralising and blending as major process steps. The reduction efficiencies in viscosity, free fatty acids (FFAs) and phospholipids (gums) were used as performance indicators. Main materials used for blending were fusel oil (FO) and natural gas condensate (NGC). Degumming and neutralisation had no impact on viscosity but they were effective (98%) in gums and FFAs removal respectively. The effect of blending was significant with 50-80% viscosity reduction. The optimum parameters for formulating blends were found to depend on the modifier characteristics and on the fatty acid (FA) composition of PO. The overall results indicated that degummed-neutralised-blended PO’s properties meet the specifications for diesel fuel grade 4-D. basing on laboratory results and other sources, techno-economic analysis of the process was carried out with an aid of SuperPro Designer software. A small-scale modified plant oil (MPO) production plant with an annual capacity of 15 t of MPO (batch process) was designed and simulated and found to be economically viable. It was recommended that engine performance tests to be done in future in order to analyse the short- and long-term effects of MPO on engine.