Browsing by Author "Semiyaga, Swaib"

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    Decentralized opt 1 ions for faecal sludge management in urban slum 2 areas of Sub-Saharan Africa: A review of technologies, practices and 3 end-uses
    (Resources, Conservation and Recycling, 2015) Semiyaga, Swaib; Okure, Mackay A. E.; Niwagaba, Charles B.; Katukiza, Alex Y.; Kansiime, Frank
    Faecal sludge (FS), a product from on-site sanitation systems, poses a management challenge in densely populated urban slums of Sub-Saharan Africa (SSA). Currently, FS or its liquid fraction after dewatering is co-treated with sewage in conventional treatment plants. When dewatered, the solid stream is dried and stored further as the terminal treatment or is co-treated directly with organic solid wastes in composting or anaerobic digestion systems. To implement these, FS has to be collected and transported. Also, land is needed, but it is in most cases limited in slums or their vicinity. The collection and transport of FS from slums is costly due to lack of access, traffic congestion and long travel distances to treatment plants. Moreover, uncollected FS poses health risks and pollutes surface and/or ground water within slums. This review demonstrates that currently utilized technologies and practices fall short in various ways and discusses the possibility of minimizing FS management related costs, risks and pollution in urban slums by decentralized treatment and end-use. It also discusses the possible FS-derived end-products and their benefits to urban slum dwellers. Substitution of a part of natural materials (sand and clay) when building and/or biomass (firewood and charcoal) for cooking with FS derived end-products could multiply the benefits of improved sanitation to slum dwellers.
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    Enhancing Faecal Sludge Dewaterability and End use By Conditioning With Sawdust and Charcoal Dust
    (Environmental Technology, 2018) Semiyaga, Swaib; Okure, Mackay A. E.; Niwagaba, Charles B.; Nyenje, Philip M.; Kansiime, Frank
    Faecal sludge (FS) treatment in urban slums of low-income countries of sub-Saharan Africa is poor or non-existent. FS contains over 90% water and therefore dewatering it within slums decreases transport costs, facilitates local treatment and end-use. This study was designed to enhance the dewatering efficiency of FS, using two locally available physical conditioners (sawdust and charcoal dust), each applied at dosages of 0%, 25%, 50%, 75%, 100% and 125% TS. The optimum dosage for both conditioners occurred at 50% and 75% for cake moisture content and capillary suction time, respectively. The dewatering rate improved by 14.3% and 15.8%, whereas dewatering extent (% cake solids) improved by 22.9% and 35.7%, for sawdust and charcoal dust, respectively. The dewatering in FS conditioned with sawdust and charcoal dust was mainly governed by absorption and permeation (porosity), respectively. The FS calorific value improved (from 11.4 MJ kg−1) by 42% and 49% with 50% TS dosage of sawdust and charcoal dust, respectively. The FS structure also became porous after dewatering which hastens the subsequent drying and/or composting processes. Due to comparable performance in dewatering, sawdust or charcoal dust, whichever is locally available, is recommended to treat FS in low-income urban slum settlements.
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    Optimisation of Centrifuge Operating Conditions for Dewatering Physically Conditioned Faecal Sludge from Urban
    (Environmental Technology & Innovation, 2017) Semiyaga, Swaib; Niwagaba, Charles B.; Nyenje, Philip M.; Kansiime, Frank
    Decentralised faecal sludge (FS) dewatering in urban slums using centrifugation technology has potential to reduce public health risks and environmental pollution caused by indiscriminate disposal of untreated FS. A laboratory-scale centrifuge was applied to dewater FS from lined pit latrines, conditioned with sawdust and charcoal dust. Response surface methodology and central composite design were used to construct and model relationships between independent variables (FS volume, centrifugation time and speed) and the dependent variable (per cent cake solids) for unconditioned and conditioned (sawdust and charcoal dust) FS. The results demonstrated that the centrifugation technology can yield more per cent cake solids at reduced speeds when physically conditioned. Rotational speed was a significant parameter for unconditioned (original) () and charcoal dust conditioned FS (). Significant parameters for sawdust conditioned FS were speed () and quadratic effect of time (). An optimal centrifugation time of 20 minutes and centrifugation container volume of 50 mL at 70–80% full of FS for conditioned FS were obtained. The centrifugation speeds tested in this paper provide critical information for proto-type design of a hand-powered centrifuge, the operating conditions and its subsequent set-up. This can serve as an option for dewatering FS from commonly used sanitation facilities in urban slums, thereby enabling decentralised treatment to reduce costs of FS management and support resource recovery at the source.
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    A Value Proposition: Resource Recovery From Faecal Sludge—Can It Be The Driver For Improved Sanitation?
    (Resources, Conservation and Recycling, 2014) Diener, Stefan; Semiyaga, Swaib; Niwagaba, Charles B.; Muspratt, Ashley Murray; Gning, Jean Birane; Mbéguéré, Mbaye; Ennin, Joseph Effah; Zurbrugg, Christian; Strande, Linda
    There is currently a lack of access to affordable sanitation in urban areas of Sub-Saharan Africa. This study evaluated the potential for resource recovery from innovative faecal sludge treatment processes to generate a profit that could help sustain the sanitation service chain. A total of 242 interviews were conducted in Accra, Ghana; Dakar, Senegal; and Kampala, Uganda to compare markets in different cultural and regional contexts. Products identified to have potential market value include dry sludge as a fuel for combustion, biogas from anaerobic digestion, protein derived from sludge processing as animal feed, sludge as a component in building materials, and sludge as a soil conditioner. The market demand and potential revenue varied from city to city based on factors such as sludge characteristics, existing markets, local and regional industrial sectors, subsidies, and locally available materials. Use as a soil conditioner, which has been the most common end use of treated sludge, was not as profitable as other end uses. These findings should help policy and decision makers of sanitation service provision to design financially viable management systems based on resource recovery options.