NRU :: Browsing by Author "Nyenje, Philip M."

Browsing by Author "Nyenje, Philip M."

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Assessing Ambient And Internal Environmental Conditions Of Pit Latrines In Urban Slums Of Kampala, Uganda: Effect On Performance
(Journal of Water, Sanitation and Hygiene for Development, 2017) Nakagiri, Anne; Niwagaba, Charles B.; Nyenje, Philip M.; Kulabako, Robinah K.; Tumuhairwe, John B.; Kansiime, Frank
There is increasing interest to improve the functionality and performance of pit latrines in low income urban areas. This study aimed at assessing the ambient and pit environmental conditions and their implications on the performance (smell and fly nuisance) of pit latrines. Forty-two pit latrines were investigated in urban slums of Kampala, Uganda, through field observation and measurements of ambient and pit environmental conditions. The implications were assessed using oxygen-reduction potential (ORP) and its association with smell/insect nuisances. The pit temperature (21 to 30.7 °C), pH (5.0–11.8) and ORP (−247 to 65.9 mV) were consistently, significantly different (p < 0.001) between the surface and 0.5 m depth of pit content. The conditions in most (95%) pit latrines were anoxic (ORP < +50 mV), and mainly within the acid formation range (ORP −199 to −51 mV). Most smelling pit latrines and flies were within the acid formation ORP range, with a significant association (gamma, G = 0.797, p = 0.014) between ORP and smell in clean latrines only. The results suggest that ventilation of pit latrines within urban slums was not sufficient. Additionally, cleanliness, moisture reduction and waste stabilisation could address bad smells in pit latrines, ultimately improving their usage in urban slums.
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.
Observed controls on resilience of groundwater to climate variability in sub-Saharan Africa
(Nature, 2019) Cuthbert, Mark O.; Taylor, Richard G.; Owor, Michael; Nyenje, Philip M.; Kukuric, Neno
Groundwater in sub-Saharan Africa supports livelihoods and poverty alleviation1,2, maintains vital ecosystems, and strongly influences terrestrial water and energy budgets3. Yet the hydrological processes that govern groundwater recharge and sustainability—and their sensitivity to climatic variability—are poorly constrained4,5. Given the absence of firm observational constraints, it remains to be seen whether model-based projections of decreased water resources in dry parts of the region4 are justified. Here we show, through analysis of multidecadal groundwater hydrographs across sub-Saharan Africa, that levels of aridity dictate the predominant recharge processes, whereas local hydrogeology influences the type and sensitivity of precipitation–recharge relationships. Recharge in some humid locations varies by as little as five per cent (by coefficient of variation) across a wide range of annual precipitation values. Other regions, by contrast, show roughly linear precipitation–recharge relationships, with precipitation thresholds (of roughly ten millimetres or less per day) governing the initiation of recharge. These thresholds tend to rise as aridity increases, and recharge in drylands is more episodic and increasingly dominated by focused recharge through losses from ephemeral overland flows. Extreme annual recharge is commonly associated with intense rainfall and flooding events, themselves often driven by large-scale climate controls. Intense precipitation, even during years of lower overall precipitation, produces some of the largest years of recharge in some dry subtropical locations. Our results therefore challenge the ‘high certainty’ consensus regarding decreasing water resources4 in such regions of sub-Saharan Africa. The potential resilience of groundwater to climate variability in many areas that is revealed by these precipitation–recharge relationships is essential for informing reliable predictions of climate-change impacts and adaptation strategies.
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.
Performance Of Pit Latrines In Urban Poor Areas: A Case Of Kampala, Uganda
(Habitat international, 2015) Nakagiri, Anne; Kulabako, Robinah N.; Nyenje, Philip M.; Tumuhairwe, John B.; Niwagaba, Charles B.; Kansiime, Frank
In many urban poor areas of Sub-Saharan Africa (SSA), demand for human excreta disposal is met, predominantly by pit latrines. This study aimed at determining the status of pit latrines (design, construction, operation and maintenance) and its influence on latrine performance (filling, smell and insect nuisance). The study was conducted on 130 pit latrines in typical urban poor areas of Kampala, Uganda. Data on design, construction, usage, operation and performance of the pit latrines was collected by interviews, observations and measurements; and analysed by descriptive statistics, bi-variate analysis and logistic regression. Results showed that the level of pit content was predicted by rain or storm water entry, terrain, cleaning before or after use and number of households using the latrine. Smell was predicted by cleanliness, stance length, superstructure material and whether the latrine was private or public. The predictor of presence of flies was the superstructure material. To improve the performance of pit latrines in urban poor areas, researchers and practitioners should develop local latrine design standards (dimensions, construction materials and number of users) and cleaning guidelines for local policy makers to implement.

Browsing by Author "Nyenje, Philip M."

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