PhD defence by Ssemiyaga Swaib

Event Date
Monday, 3 July 2017 - 9:00am to 1:00pm
Event Info

ABSTRACT: TITLE: DEWATERING AS A CRITICAL STEP IN URBAN SLUM-BASED FAECAL SLUDGE MANAGEMENT  Faecal sludge (FS), a product from on-site sanitation facilities, poses a management challenge in densely populated urban slums of Sub-Saharan Africa (SSA). The collection and transport of FS from slums to treatment facilities is costly due to high emptying costs; high density of housing units, which limit access to sanitation facilities by vacuum trucks; associated traffic jams and long travel distances to treatment plants. The technologies for decentralised management of FS at a household or community level in slums can eliminate such barriers. This coupled, with potential end-use of the product(s) from FS acceptable at particular slum level, can eventually increase the amounts of FS treated and thus, limit risks to public health and environmental pollution. Since FS contains over 90 % water, dewatering it presents an important step for resource recovery, thus incentivising its management to fully or partially bear its own cost. This study investigated the potential of centrifugation technology in dewatering of FS generated from pit latrines used in slums. Dewaterability extent and dewaterability rate were measured in terms of percent cake solids and capillary suction time, respectively. The average dewatering extent of FS from unlined pit latrines (31.8%) was significantly higher than that of FS from lined latrines (18.6%) (p = 0.000) while the dewaterability rate (1122 and 1485 seconds of FS from lined and unlined pits, respectively) was not significantly different (p = 0.104). The low dewatering extent of FS from lined pits was improved by addition of sawdust and charcoal dust conditioners. The dewatering extent improved by 22.9% and 35.7%, for FS conditioned with sawdust and charcoal dust, respectively, at optimum dosage of 75 % TS. The dewatering of FS conditioned with sawdust and charcoal dust was mainly governed by absorption and permeation (porosity). Centrifuge operating conditions necessary for dewatering FS conditioned with sawdust/ charcoal dust were optimised. Rotational speed was a significant parameter for charcoal dust conditioned FS (p = 0.0019) and sawdust conditioned FS (p = 0.0001). In addition, the quadratic effect of time was significant for only sawdust conditioned FS (p = 0.0494). An optimal centrifugation time of 20 minutes at a speed of 920, 0 and 160 rpm for unconditioned, sawdust and charcoal dust conditioned FS, respectively, yielded the same per cent cake solids when the centrifugation container volume of 50 mL was filled to 70-80% with FS. Results showed that centrifugation technology can be further explored through proto-type design of a hand/cycle-powered centrifuge, thereby enabling decentralised treatment to reduce costs of FS management and support resource recovery at/near the source. Furthermore, emptying equipment that do not require changing FS moisture content should be used, since such emptied FS from pit latrines in slums would  not require a thickening stage.  

Event Venue
CEDAT Conference Hall
Category by Unit
College of Engineering, Design, Art and Technology
Contact Info
Contact Info: 
Prof. Umaru Bagampadde; Dean School of Engineering. bumaru@cedat.mak.ac.ug
Additional Information