Fate and Transport of Nutrients in Groundwater and Surface Water in an Urban Slum Catchment, Kampala, Uganda
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Urban informal settlements or slums are growing rapidly in cities in sub-Saharan Africa. Most often, a sewer system is not present and the commonly-used low-cost onsite wastewater handling practices, typically pit latrines, are frequently unplanned, uncontrolled and inefficient. Consequently, most households dispose of their untreated or partially treated wastewater on-site, generating high loads of nutrients to groundwater and streams draining these areas. However, the fate of nutrients in urban slums is generally unknown. In excess, these nutrients can cause eutrophication in downstream water bodies.
This book provides an understanding of the hydro-geochemical processes affecting the generation, fate and transport of nutrients (nitrogen and phosphorus) in a typical urban slum area in Kampala, Uganda. The approach used combined experimental and modeling techniques, using a large set of hydrochemical and geochemical data collected from shallow groundwater, drainage channels and precipitation.
The results show that both nitrogen-containing acid precipitation and domestic wastewater from slum areas are important sources of nutrients in urban slum catchments. For nutrients leaching to groundwater, pit latrines retained over 80% of the nutrient mass input while the underlying alluvial sandy aquifer was also an effective sink of nutrients where nitrogen was removed by denitrification and anaerobic oxidation and phosphorus by adsorption to calcite. In surface water, nutrient attenuation processes are limited. This study argues that groundwater may not be important as regards to eutrophication implying that management interventions in slum areas should primarily focus on nutrients released into drainage channels. This research is of broad interest as urbanization is an ongoing trend and many developing countries lack proper sanitation systems.
Table of Contents
2. Eutrophication and nutrient release in urban areas of sub-Saharan Africa — a review
3. Using hydrochemical tracers to identify sources of nutrients in unsewered urban catchments
4. Nutrient pollution in shallow aquifers underlying pit latrines and domestic solid waste dumps in urban slums
5. Understanding the fate of sanitation-related nutrients in a shallow sandy aquifer below an urban slum area
6. Phosphorus transport and retention in a channel draining an urban tropical catchment with informal settlements
7.Conclusions, recommendations and future research needs
Philip Mayanja Nyenje (1977, Kampala, Uganda) obtained his Bachelor of Science (first class) in Civil Engineering from Makerere University, Uganda in 2003 and a Master of Science (greatest distinction) in Water Resources Engineering from Katholieke Universiteit of Leuven and the Vrije Universiteit of Brussels in Belgium in 2007. For this PhD research he carried out research at UNESCO-IHE and Delft University of Technology, on the processes governing the fate and transport of sanitation-related nutrients in groundwater and surface water in an urban informal settlement (or slum) in Kampala, Uganda. He has presented his work at several international conferences and has published several papers in highly-ranked international peer-reviewed journals. His research interests include contaminant transport in groundwater and surface water, hydrological processes, tracer hydrology and hydrochemistry, water quality modelling and water resources engineering and management.