Browsing by Author "Bwapwa, Joseph Kapuku."

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Analysis of an anaerobic baffled reactor treating complex particulate wastewater in an abr-membrane bioreactor unit.
(2010) Bwapwa, Joseph Kapuku.; Foxon, Katherine Maria.; Buckley, Christopher Andrew.
Providing water and proper sanitation to poor communities by 2015 is one of the United Nations targets for this millennium. In South Africa many communities aspire to waterborne sanitation. However, there is a technology gap for decentralized and sustainable waterborne sanitation systems capable of treating domestic wastewater (Foxon et al., 2006). Although domestic wastewater is more commonly treated using aerobic processes, anaerobic processes may be more appropriate for decentralized applications since they do not require aeration. Research is currently being undertaken to understand the behavior of a combined ABR-MBR unit for treating domestic wastewater. In this study, the anaerobic baffled reactor (ABR) was investigated by analyzing physico-chemical and biochemical data from experiments on a laboratory-scale ABR. This anaerobic reactor was treating complex particulate wastewater made up of sludge from the ventilated improved pit latrine toilets (known as VIP sludge). The main focus of this study was to establish the relationship between the increasing organic loading rates and the effluent characteristics (such as chemical oxygen demand: COD and extrapolymeric substances: EPS). The present work was structured in two parts; in the first part the reactor was operated at constant hydraulic retention time (HRT) without controlling feed characteristics. In the second part, the ABR was operated with step increases in organic loading rates. It was logistically not possible to provide a feed of real domestic wastewater to the laboratory-scale equipment. Consequently, a pit latrine sludge diluted with tap water was used to feed the ABR. This feed was found to have different biodegradability characteristics compared to domestic wastewater. However, the results still give insight into the performance of the ABR and into the treatability of VIP sludge. COD removal ranged from 52 to 80 % depending on the inlet COD. Some COD removal was due to solids retention in compartments, while it was estimated that only 28% of COD removal was due to biological degradation. Soluble extrapolymeric substances (proteins and carbohydrates) which are usually a by -product of anaerobic degradation were higher in the feed than in the effluent despite the increasing organic loading rates. However, more than 50 % of soluble extrapolymeric substances from the influent remained in the effluent and were found (in a parallel project) to influence membrane fouling in the membrane section of the experimental set-up (ABR-MBR unit). Parameters such as pH, conductivity, alkalinity, total and volatile solids were also investigated in this study. The pH decreased slightly from the inlet to the outlet during all runs even though the loading rates were increased. Conductivity increased significantly from influent to effluent with the increasing organic loading rates. Large amounts of total solids were retained in the reactor during the treatment process. Low alkalinity production was recorded during the operation of the reactor. In most cases, the data recorded in this study showed a low biological activity taking place while the reactor was working at room temperatures. Overall, up to 80% of removal efficiencies in terms of total COD and solids were recorded with increasing organic loading rates at constant hydraulic retention time. While these results do not allow the prediction of ABR-MBR performance during the treatment of real wastewater, it was concluded that: Most solids retention occurred in the feed tank. Most COD removal occurred as a result of solids retention and digestion. Loading characteristics did not strongly influence effluent EPS, pH or alkalinity, but did influence COD and conductivity. The relatively low biodegradability of the feedstock indicates that anaerobic digestion is not the most appropriate treatment for VIP sludge.
Production of jet fuel from microalgae biomass cultivated in saline domestic wastewater.
(2018) Bwapwa, Joseph Kapuku.; Trois, Cristina.; Anandraj, Akash.
Jet fuel from crude petroleum oil is known as the most efficient energy carrier for the aviation sector. Environmental concerns and economic pressure drive major industries to adapt to current global revolution towards alternative, sustainable, and clean fuels. In this study conversion of algae biomass to jet fuel is presented as a novel technology of low carbon footprint and a cost-effective jet fuel. In this current study, it is reported that there is a possibility of substantially converting microalgae oil into aviation fuel by adapting and applying the same processes used for the conversion of fossil crude petroleum oil into conventional jet fuel. The drawback, however, remains the low oil output from used species of microalgae and the general operating costs which are still at developmental stages. A part from the introduction and the literature review making respectively chapter 1 and chapter 2, this study, therefore, has focused on the magnification of lipid production and the simplification of the conversion processes in chapter 3. Microalgae cells were physiologically stressed by totally depriving them of all growth nutrients for three days aiming to modify their genetic physiology which in turn will favour the yield of lipid and bio-oil. An elaborate experiment was established from algae biomass cultivation to jet fuel production. The experiment involved biomass cultivation, harvesting and bio-oil extraction using a solvent mixture made of methanol and chloroform. Thermal cracking without catalyst or pyrolysis of crude bio-oil were undertaken to break down the carbon chains in order to complete the fractionation. ASTM methods and standards related to aviation fuels were used to generate the relevant data. The conceptual design with a simplified conversion process undertaken in chapter 4 was established based on the experiment completed in chapter 3. It suggested to cultivate the species in domestic wastewater ponds or use the seawater/saline water because the used species was comfortable in saline or marine environment. Parameters such as density, kinematic viscosity, flash point, freezing point, total sulfur, net heat of combustion and distillation were evaluated during the experiment in chapters 3 and 4. It was found that the majority of parameters analysed regarding the algae-based jet fuel from the laboratory was complying to ASTM standards. However, it will require additional processes such as upgrading and reforming to enhance the quality of jet fuel and improve the level of some parameters such as density and freezing point which were not rigorously complying with ASTM standards. Also, the improvement involves the use of the same additives used for conventional jet fuels for flow ability and freezing at higher altitudes. The scaling up of the production process is still a challenge due to operating costs. In this regard, blending algae-based jet fuel and the conventional jet fuel in 50/50, 80/20 and 20/80 ratios was carried out and evaluated in Chapter 5 and Chapter 6 as an alternative approach for sustainability.