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Characterization of peri-urban anthropogenic pollution in Kampala, Uganda
KTH, Superseded Departments, Land and Water Resources Engineering. KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Management and Assessment.
KTH, Superseded Departments, Land and Water Resources Engineering. KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Management and Assessment.
2004 (English)In: WEDC International Conference on people centred approaches to water and environmental sanitation, 2004, 474-482 p.Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
2004. 474-482 p.
National Category
Other Environmental Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6053Scopus ID: 2-s2.0-34249818718OAI: oai:DiVA.org:kth-6053DiVA: diva2:10644
Conference
30th WEDC International Conference, Vientiane
Note
QC 20101207Available from: 2006-08-17 Created: 2006-08-17 Last updated: 2012-02-13Bibliographically approved
In thesis
1. Analysis of the impact of anthropogenic pollution on shallow groundwater in peri-urban Kampala
Open this publication in new window or tab >>Analysis of the impact of anthropogenic pollution on shallow groundwater in peri-urban Kampala
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

An investigation to assess the anthropogenic pollutant loads, transport and impact on shallow groundwater in one of Kampala’s peri-urban areas (Bwaise III Parish) was undertaken. Bwaise III is a densely populated informal settlement with a high water table (<1.5 m) and inadequate basic social services infrastructure (e.g, sanitation, safe water supply, roads, etc).

Field surveys were undertaken to identify, locate and quantify various pollutant sources. Information on the usability and operational aspects of the excreta and solid waste management systems was obtained from consultations with the residents. Water from installed monitoring wells and one operational protected spring and wastewater (sullage) characteristics (quality, discharges for drains and spring, water levels for the wells) as well as soil characteristics (soil stratigraphy, physical and chemical) were determined through field and laboratory measurements. Laboratory batch experiments were undertaken to estimate phosphorus sorption potential of the soils.

The results reveal that excreta disposal systems, solid waste and sullage are the major contributors to shallow groundwater contamination. High contaminant loads from these sources accumulate within the area resulting in widespread contamination. The water table responds rapidly to short rains (48hr) due to the pervious and shallow (<1 m) vadose zone, which consists of mostly organic fill material. Rapid water quality deterioration (increased thermotolerant coliforms, organic content in the form of total kjedahl nitrogen, phosphorus) following rains potentially follows from leaching, desorption and macropore flow. Spatial variation of the water quality in the area is largely related to anthropogenic activities within the vicinity of the well sources. Animal rearing, solid waste dumps and latrines are seen to result in increased localised microbial and organic content during the rains. The spring discharge with high nitrate levels does not respond to short rains suggesting that this source is fed by regional baseflow. The corresponding high microbial contamination in this case is a result of observed poor maintenance of the protection structure leading to direct ingress of contaminated surface runoff. Natural attenuation of contaminants is very limited. Estimated bacteria die-off rates are very low, about 0.01hr-1, suggesting a high risk for microbial contamination. The soils still have potential to retain additional phosphorus, whose sorption is largely a function of iron, available phosphorus and moisture content of the soils. This is also seen with the model results in which the phosphorus contaminant plume sticks to the surface irrespective of the rainfall infiltration rates. Simulation results show that continuous heavy intense rains (> 0.25mm/min) result in rapid flooding occurring within 1hr to 2 days. With lower rains, the water table does not rise to the surface, and no flooding takes place.

Protection of the shallow groundwater in the area requires socio-technical measures targeting reduction of pollutant loads within the area as well as a wider spring catchment. Re-protection of the spring, coupled with awareness creation, should be immediately addressed so as to reduce microbial contamination. Community participation in solidwaste management should be encouraged. Resource recovery systems such as composting of the mostly organic waste and use of ecological sanitation toilet systems should be piloted in the area. Successful operation of the systems however depends on continuous sensitisation of the communities.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. x, 56 p.
Series
Trita-LWR. LIC, ISSN 1650-8629 ; 2029
Keyword
Shallow groundwater, Sanitation, Peri-urban, Vadose zone, Anthropogenic, Modelling
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-4077 (URN)91-7178-103-X (ISBN)
Supervisors
Note
QC 20101207Available from: 2006-08-17 Created: 2006-08-17 Last updated: 2010-12-07Bibliographically approved
2. Environmental sanitation situation and solute transport in variably saturated soil in peri-urban Kampala
Open this publication in new window or tab >>Environmental sanitation situation and solute transport in variably saturated soil in peri-urban Kampala
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The environmental sanitation situation in Kampala’s peri-urban areas was reviewed and investigated through field studies, structured interviews with personnel from key institutions and administration of questionnaires to households in a selected peri-urban settlement (Bwaise III Parish).  In this settlement, specific field and laboratory measurements were undertaken so as to create a better understanding of the environmental sanitation situation, anthropogenic pollution loads and their transport and impact (with a focus on Phosphorus) in Kampala’s Peri-urban areas in pursuit of interventions for improving the environmental sanitation and protecting the shallow groundwater resource there. The review revealed that the urban poor in Kampala, like elsewhere in developing countries, are faced with inadequate basic services caused by a combination of institutional, legal and socio-economic issues and that the communities’ coping strategies are in most cases detrimental to their health and well-being. Field surveys showed that excreta disposal systems, solid waste and greywater are major contributors to the widespread shallow groundwater contamination in the area. Field measurements revealed that the water table responds rapidly to short rains (48 h) due to the pervious (10-5-10-3 m/s) and shallow (<1 mbgl) vadose zone, which consists of foreign material (due to reclamation). This anthropogenically influenced vadose zone has a limited contaminant attenuation capacity resulting in water quality deterioration following rains. The only operational spring in the area is fed by regional baseflow meaning a wider protection zone. The spring discharge exhibited microbial quality deterioration after rains primarily as a result of poor maintenance of the protection structure. Subsurface phosphorus (P) transport mechanisms appeared to be a combination of adsorption, precipitation, leaching from the soil media and through macropore flow with the latter two playing an important role in the wet season. The Langmuir isotherm described the phosphorus sorption data well (R2³ 0.95) and the best prediction of Langmuir sorption maximum (Cmax) had organic carbon, Ca and available phosphorus and soil pH as significant predictors. Loosely bound P (NH4Cl-P) was the least fraction (<0.4% of total P) in all layers indicating a high binding capacity of P by the soils implying that the soils have a capacity to adsorb additional P loads. Simulation results from the preliminary numerical model built in this study based on field and laboratory measurements indicate that rainfall infiltration rates > 7x10-3 mm/s drive shallow groundwater contamination with higher intense rains of relatively longer duration (³ 70 mm within 48 h) reducing phosphorus transport. Sensitivity analysis of the model input with respect to how long it takes to pollute the subsurfacehad the phosphorus sorption coefficients as being more influential than the pore size and air entry values. There are however, key contrasts between the model simulations and field observations which are useful in guiding new efforts in data collection. The study reveals that intervention measures to improve the environmental sanitation and protect the shallow groundwater in the peri-urban settlements are of a multidisciplinary nature necessitating action research with community participation.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. xiv, 60 p.
Series
Trita-LWR. PHD, ISSN 1650-8602 ; 1059
Keyword
Environmental Sanitation, Kampala, Modelling, Phosphorus transport, Shallow groundwater, Peri-urban, Vadose zone
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-24595 (URN)978-91-7415-728-4 (ISBN)
Public defence
2010-09-30, Makerere University, Uganda, 09:15 (English)
Opponent
Supervisors
Note
QC 20100917Available from: 2010-09-17 Created: 2010-09-17 Last updated: 2010-12-01Bibliographically approved

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