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Environmental sanitation situation and solute transport in variably saturated soil in peri-urban Kampala
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Management and Assessment.
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 [en]
Environmental Sanitation, Kampala, Modelling, Phosphorus transport, Shallow groundwater, Peri-urban, Vadose zone
National Category
Other Environmental Engineering
Identifiers
URN: urn:nbn:se:kth:diva-24595ISBN: 978-91-7415-728-4 (print)OAI: oai:DiVA.org:kth-24595DiVA: diva2:352105
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
List of papers
1. Characterization of peri-urban anthropogenic pollution in Kampala, Uganda
Open this publication in new window or tab >>Characterization of peri-urban anthropogenic pollution in Kampala, Uganda
2004 (English)In: WEDC International Conference on people centred approaches to water and environmental sanitation, 2004, 474-482 p.Conference paper, Published paper (Refereed)
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-6053 (URN)2-s2.0-34249818718 (Scopus ID)
Conference
30th WEDC International Conference, Vientiane
Note
QC 20101207Available from: 2006-08-17 Created: 2006-08-17 Last updated: 2012-02-13Bibliographically approved
2. Study of the impact of land use and hydrogeological settings on the shallow groundwater quality in a peri-urban area of Kampala, Uganda
Open this publication in new window or tab >>Study of the impact of land use and hydrogeological settings on the shallow groundwater quality in a peri-urban area of Kampala, Uganda
2007 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 381, no 03-jan, 180-199 p.Article in journal (Refereed) Published
Abstract [en]

A study to assess the impacts of land use and hydrogeological characteristics on the shallow groundwater in one of Kampala's peri-urban areas (Bwaise III Parish) was undertaken for a period of 19 months. Water quality monitoring was carried out for 16 installed wells and one operational protected spring to ascertain the seasonal variation. The aspects of hydrogeological setting investigated in the study were the subsurface unconsolidated material characteristics (stratigraphy, lithology, hydraulic conductivity, porosity and chemical content), seasonal groundwater depths and spring discharge, topography and rainfall of the area. Both laboratory and field measurements were carried out to determine the soil and water characteristics. Field surveys were also undertaken to identify and locate the various land use activities that may potentially pollute. The results demonstrate that the water table in the area responds rapidly to short rains (48 h) due to the pervious (10(-5)-10(-3) ms(-1)) 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 the rains. There is widespread contamination of the groundwater with high organic (up to 370 mgTKN/l and 779 mgNO(3)(-)/l), thermotolerant coliforms (TTCs) and faecal streptococci (FS) (median values as high as 126E3 cfu/100 ml and 154E3 cfu/100 ml respectively) and total phosphorus (up to 13 mg/l) levels originating from multiple sources of contamination. These include animal rearing, solid waste dumping, pit latrine construction and greywater/stormwater disposal in unlined channels leading to increased localised microbial (faecal) and organic (TKNNO3-) contamination during the rains. The spring discharge (range 1.22-1.48 m(3)/h) with high nitrate levels (median values of 117 and 129 mg/l in the wet and dry seasons) did not vary significantly with season (p=0.087) suggesting that this source is fed by regional base flow. However, the microbial quality deterioration observed in the spring discharge after a rain event (median values of 815TTCs cftr/100ml and 433 FS cfa/100ml) was attributed to the poor maintenance of the protection structure. Identification and selection of appropriate management solutions for the protection of shallow groundwater in informal settlements should not only be based on water quality problems and the causal physical characteristics as demonstrated by this study, but also institutional and socio-economic factors.

Keyword
peri-urban, hydrogeological setting, land use, thermotolerant coliforms, total phosphorus, total Kjedahl nitrogen, water, risk, soil, settlements, management, phosphorus
National Category
Oceanography, Hydrology, Water Resources
Identifiers
urn:nbn:se:kth:diva-16765 (URN)10.1016/j.scitotenv.2007.03.035 (DOI)000247831700017 ()2-s2.0-34249800094 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Phosphorus transport in shallow groundwater in peri-urban Kampala, Uganda: results from field and laboratory measurements
Open this publication in new window or tab >>Phosphorus transport in shallow groundwater in peri-urban Kampala, Uganda: results from field and laboratory measurements
2008 (English)In: Environmental Geology, ISSN 0943-0105, E-ISSN 1432-0495, Vol. 53, no 7, 1535-1551 p.Article in journal (Refereed) Published
Abstract [en]

To understand Phosphorus (P) sources and transport processes in the subsurface in Bwaise III Parish, Kampala, P attenuation and adsorption capacities of soils were studied in situ and from laboratory measurements. Relationships between sorption parameters and soil matrix properties, rates and mechanism of the adsorption process and soil P fractions were also investigated. P was generally higher in the wet than the dry season, but for both seasons, the maximum was 5 mgP/l. P transport mechanisms appeared to be a combination of adsorption, precipitation, leaching from the soil media and by colloids with the latter two playing an important role in the wet season. The sorption process comprised two phases with the first stage rate constants being about fourfold those of the second stage. The Langmuir isotherm described the sorption data well (R-2 >= 0.95) with the second soil layer exhibiting the highest sorption maximum (C-max) (average value 0.6 +/- 0.17 mgP/gDW). The best prediction of C-max had organic carbon, Ca, available P and soil pH. Residual P consisting mostly of organics was the main fraction in all the layers followed by inorganic HCl-P and NaOH-P in the top and middle layers, respectively. Loosely bound P (NH4Cl-P) was the least fraction (< 0.4% of total P) in all layers indicating the high binding capacity of P by the soils. The study results suggest that P dynamics is related to Ca, Fe and organic carbon content of the soils.

Keyword
peri-urban, Phosphorus, shallow groundwater, adsorption, Uganda, soil, sorption, phosphate, sediments, water, adsorption, fractions, leachate, duckweed, release
Identifiers
urn:nbn:se:kth:diva-17268 (URN)10.1007/s00254-007-0764-0 (DOI)000252276100017 ()2-s2.0-38149047526 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
4. Modelling of flow and phosphorus transport in variably saturated soil in a peri-urban settlement in Kampala, Uganda
Open this publication in new window or tab >>Modelling of flow and phosphorus transport in variably saturated soil in a peri-urban settlement in Kampala, Uganda
(English)Article in journal (Other academic) Submitted
Identifiers
urn:nbn:se:kth:diva-24567 (URN)
Note
QS 20120327Available from: 2010-09-17 Created: 2010-09-17 Last updated: 2012-03-27Bibliographically approved
5. Using field measurements and solute transport modelling to assess potential for natural remediation of phosphorus in variably staturated soil in a peri-urban settlement in Kampala, Uganda
Open this publication in new window or tab >>Using field measurements and solute transport modelling to assess potential for natural remediation of phosphorus in variably staturated soil in a peri-urban settlement in Kampala, Uganda
(English)Article in journal (Other academic) Submitted
Identifiers
urn:nbn:se:kth:diva-24593 (URN)
Note
QS 20120327Available from: 2010-09-17 Created: 2010-09-17 Last updated: 2012-03-27Bibliographically approved
6. Environmental health practices, constraints and possible interventions in peri-urban settlements in developing countries - a review of Kampala, Uganda
Open this publication in new window or tab >>Environmental health practices, constraints and possible interventions in peri-urban settlements in developing countries - a review of Kampala, Uganda
2010 (English)In: International Journal of Environmental Health Research, ISSN 0960-3123, E-ISSN 1369-1619, Vol. 20, no 4, 231-257 p.Article in journal (Refereed) Published
Abstract [en]

Like most cities in developing countries, Uganda's capital city, Kampala, is experiencing urbanisation leading to an increase in population, and rapid development of peri-urban (informal) settlements. More than 60% of the city's population resides in these settlements which have the lowest basic service levels (sanitation, water supply, solid waste collection, stormwater and greywater disposal). A review of earlier studies on infrastructure development and sustainability within Kampala's peri-urban settlements, field surveys in a typical peri-urban settlement in the city (Bwaise III Parish), and structured interviews with key personnel from the National Water and Sewerage Corporation (NWSC), Kampala City Council (KCC), and the National Environment Management Authority (NEMA) were undertaken. Findings on current environmental health practices as well as perspectives of local communities and interviewed institutions on problems, constraints and possible solutions to basic service provision are presented. The implications of these viewpoints for possible environmental health interventions are presented.

Keyword
drainage, peri-urban, sanitation, solid waste management, water supply
Identifiers
urn:nbn:se:kth:diva-24505 (URN)10.1080/09603120903545745 (DOI)000280057300001 ()2-s2.0-77954858265 (Scopus ID)
Note
QC 20100913Available from: 2010-09-13 Created: 2010-09-13 Last updated: 2017-12-12Bibliographically approved

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