| 1. |
- Aullón Alcaine, Anna, et al.
(författare)
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Distribution and mobility of geogenic arsenic in the shallow aquifers of the northeast of La Pampa, Argentina
- 2012
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Ingår i: Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment. - 9780415637633 ; , s. 132-134
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Konferensbidrag (refereegranskat)abstract
- Groundwater contamination with elevated Arsenic (As) and other toxic trace elements has been studied in the central part of the vast Chaco-Pampean Plain, in the city of Quemú Quemú, northeastern La Pampa, Argentina. The groundwater samples were mostly alkaline with pH ranging up to 9.18, oxidizing and characterized by high EC. The concentration of total As (5.58-535 μg/L) and fluoride (0.5-14.2 mg/L) in some samples exceeded the recommended WHO drinking water guideline and the Argentine national drinking water standard. Arsenic was positively correlated with bicarbonate (HCO 3 -), Boron (B), Fluoride (F) and Vanadium (V). Long-term consumption of the groundwater could pose a severe health threat for the local community.
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| 2. |
- Aullón Alcaine, Anna, et al.
(författare)
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Geogenic arsenic and fluoride in shallow aquifers of northeastern La Pampa, Argentina : mobility constraints
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- High concentrations of geogenic arsenic (As) and fluoride (F-) in groundwater have been reported at elevated concentrations in different parts of the Chaco-Pampean Plain, in Argentina, where more than 2 million people may be exposed to high levels of these toxic elements through drinking water. Groundwater from the shallow aquifer is far exceeding the permissible WHO Standard limits of 10 μg/L for As and 1.5 mg/L for fluoride, as well as the Argentinean Standard limit of 50 μg/L for As. Geogenic As results due to the weathering of ash originated by volcanic eruptions from the Andean Cordillera and transported by wind and deposited along with the sediments and also as discrete layers and lenses over large geographical area containing around 90% of rhyolitic glass. Groundwater is hosted in a sandy silty interconnected system of aquifers and aquitards within the The Pampean aquifer. A total of 44 groundwater samples were collected from the shallow aquifers in NE of La Pampa province. Two rural areas covering an area of 600km2 in Quemú Quemú (QQ) and 300km2 in Intendente Alvear (IA) were investigated in the present study. Groundwater was circum-neutral to alkaline (pH 7.43-9.18), predominantly oxidizing (Eh ~0.24 V) with widely variable EC range (456-11,400 μS/cm). The major cation dissolved in groundwater was Na+, while the predominant anions were HCO3-, Cl- and SO42-, respectively. Water type in QQ was mostly Na-HCO3- while in IA, the composition differed between Na-HCO3- and Na-Cl-SO42- water types. Groundwater composition showed high degree of mineralization and high salinity evidenced by high EC. In discharge areas, high evaporation rates result in high salinity of shallow groundwater and visible salts incrustations on the surface of the lakes. Elevated concentrations of NO3- and PO43- observed in some wells indicated possible anthropogenic contamination. Total As concentration in groundwater from QQ ranged from 5.58 to 535 μg/L, where 94% of the wells exceeded the WHO standard limit for safe drinking water of 10 μg/L, and 56% of the wells exceeded the old Argentine standard limit of 50 μg/L. F- concentrations revealed heterogeneity and high concentrations in some wells (0.5-14.2 mg/L), 78% of samples in QQ study area exceeded the WHO standard limit of 1.5 mg/L. Under oxidizing conditions and neutral to alkaline pH, arsenate (AsV) species predominated, mainly in HAsO42- forms. As "hotspots" indicated locally contamination and correlated positively with F-, HCO3-, B and V and showed negative correlation with salinity, dissolved Fe, Al and Mn. The mechanisms involved in the mobilization of As in the shallow aquifers are controlled by the rise of pH, variations in Eh conditions and the presence of competitor ions (HCO3-, PO43-, Si, V oxyanions). Geochemical processes like adsorption/desorption, precipitation/dissolution and redox reactions may trigger to As mobilization in the shallow aquifers of La Pampa region.
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| 3. |
- Aullón Alcaine, Anna, et al.
(författare)
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Hydrogeochemical controls on the mobility of arsenic, fluoride and other geogenic co-contaminants in the shallow aquifers of northeastern La Pampa Province in Argentina
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 715
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Tidskriftsartikel (refereegranskat)abstract
- Elevated Arsenic (As) and Fluoride (F) concentrations in groundwater have been studied in the shallow aquifers of northeastern of La Pampa province, in the Chaco-Pampean plain, Argentina. The source of As and co-contaminants is mainly geogenic, from the weathering of volcanic ash and loess (rhyolitic glass) that erupted from the Andean volcanic range. In this study we have assessed the groundwater quality in two semi-arid areas of La Pampa. We have also identified the spatial distribution of As and co-contaminants in groundwater and determined the major factors controlling the mobilization of As in the shallow aquifers. The groundwater samples were circum-neutral to alkaline (7.4 to 92), oxidizing (Eh similar to 0.24 V) and characterized by high salinity (EC = 456-11,400 mu S/cm) and Na+-HCO3- water types in recharge areas. Carbonate concretions ("tosca") were abundant in the upper layers of the shallow aquifer. The concentration of total As (5.6 to 535 mu g/L) and F (0.5 to 14.2 mg/L) were heterogeneous and exceeded the recommended WHO Guidelines and the Argentine Standards for drinking water. The predominant As species were arsenate As(V) oxyanions, determined by thermodynamic calculations. Arsenic was positively correlated with bicarbonate (HCO3-), fluoride (F), boron (B) and vanadium (V), but negatively correlated with iron (Fe), aluminium (Al), and manganese (Mn), which were present in low concentrations. The highest amount of As in sediments was from the surface of the dry lake. The mechanisms for As mobilization are associated with multiple factors: geochemical reactions, hydrogeological characteristics of the local aquifer and climatic factors. Desorption of As(V) at high pH, and ion competition for adsorption sites are considered the principal mechanisms for As mobilization in the shallow aquifers. In addition, the long-term consumption of the groundwater could pose a threat for the health of the local community and low cost remediation techniques are required to improve the drinking water quality.
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| 4. |
- Bakyayita, Grace Kizito, 1971-
(författare)
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Batch Sorption Studies of Aqueous Cadmium and Lead from Contaminated Water onto Selected Biosorbents
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Groundwater, wastewater, surface runoff and surface water samples from Lake Victoria basin, Uganda was assessed for trace metals contamination. Untreated, base-treated and peroxide-treated biosorbents from Albizia coriaria, Coffea canephora, Cyperus papyrus, Erythrina abyssinica and Musa spp were investigated for removal of selected trace metals from contaminated water in batch studies. The assessed shallow groundwater and surface water was contaminated with iron and manganese. Selected speciation studies using Visual MINTEQ showed that in leachates from Municipal dumpsites 74% of the metal ions were bound to DOM, 13% were free ions and 13% were in inorganic forms moreover for urban streams 37% of the metal ions were bound to DOM, 44% were free ions and 19% were in inorganic forms. The metal levels in surface water, landfill leachate and surface runoff showed elevated levels and revealed increased risks to environmental health. Risk analysis based on the Swedish EPA showed that varied risks of negative effects in 30% – 76% of the sample sites ranging from high to increased risk in surface water whereas the results from Bio-met tool showed potential risk to toxicity effects of Cu2+, Ni2+, Zn2+ and Pb2+ in 15.3% - 30.8% surface water samples and 8.3% - 62.5% groundwater samples. Batch sorption studies revealed that the optimal conditions for Cd2+ and Pb2+ ions uptake were; pH 3.5 – 5.0 for contact time 3.0 – 3.5 hours and biosorbent dosage 10 – 12.5 g/L. Base-treated biosorbents showed 10 – 17 % sorption enhancement for Cd2+ ions and 1.6 – 2.3 % uptake reduction for Pb2+ ions. The biomass negative potential for binding base cations was in the order; Musa spp. > A. coriaria > E. abyssinica and base treatment reduced DOC leaching from biosorbents in the order; E. abyssinica > A. coriaria > Musa spp. Speciation studies showed that more ions were complexed to DOC in solutions at various pH levels. The maximum sorption intensities for both Cd2+ and Pb2+ ions uptake onto biomass occurred for low initial metal concentration; 5 mg/L. Freundlich model best fitted data for Pb2+ ions ions uptake whereas Temkin model fitted the sorption data for Cd2+ ions onto both treated and untreated biomass. For peroxide treated biomass, the maximum sorption efficiencies for both Cd2+ and Pb2+ ions were between 95.2 – 98.7% for C.canephora, 79.9 – 92.2% for Musa spp. and 42.0 – 91.3% for C.papyrus in non-competitive media and 90.8 – 98.0% for C.canephora, 56.4 – 89.3% for Musa spp. and 19.5 – 90.4% for C.papyrus in competitive media. The Langmiur model fitted non-competitive sorption data with 0.769 ≤ R2 ≥ 0.999 and the Freundlich model fitted competitive sorption data with 0.867 ≤ R2 ≥ 0.989. The pseudo second order kinetic model fitted the sorption data for Cd2+ and Pb2+ ions for untreated, peroxide treated and base treated biomass with 0.917 ≤ R2 ≥ 1.000. The sorption of trace metals was a complex potentially monolayer chemisorption with heterogeneous surface properties exhibited. In competitive sorption, sorption suppression effects observed were greater for Cd2+ than Pb2+ ions. The comparative studies on sorption performance presented agreement and no significant difference between the untreated and base treated biosorbents.
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| 5. |
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| 6. |
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| 7. |
- Coomar, Poulomee, et al.
(författare)
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Contrasting controls on hydrogeochemistry of arsenic-enriched groundwater in the homologous tectonic settings of Andean and Himalayan basin aquifers, Latin America and South Asia
- 2019
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 689, s. 1370-1387
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Tidskriftsartikel (refereegranskat)abstract
- High groundwater arsenic (As) across the globe has been one of the most well researched environmental concerns during the last two decades. Consequently, a large scientific knowledge-base has been developed on As distributions from local to global scales. However, differences in bulk sediment As concentrations cannot account for the As concentration variability in groundwater. Instead, in general, only aquifers in sedimentary basins adjacent to mountain chains (orogenic foreland basins) along continental convergent tectonic margins are found to be As enriched. We illustrate this association by integrating observations from long-term studies of two of the largest orogenic systems (i.e., As sources) and the aquifers in their associated foreland basins (As sinks), which are located in opposite hemispheres and experience distinct differences in climate and land-use patterns. The Andean orogenic system of South America (AB), an active continental margin, is in principle a modern analogue of the Himalayan orogenic system associated with the Indus-Ganges-Brahmaputra river systems in South Asia (HB). In general, the differences in hydrogeochemistry between AB and HB groundwaters are conspicuous. Major-solute composition of the arid, oxic AB groundwater exhibits a mixed-ion hydrochemical facies dominated by Na-Ca-Cl-SO4-HCO3. Molar calculations and thermodynamic modeling show that although groundwater of AB is influenced by cation exchange, its hydrochemical evolution is predominated by feldspar dissolution and relationships with secondary clays. In contrast, humid, strongly reducing groundwater of HB is dominated by Ca-HCO3 facies, suggestive of calcite dissolution, along with some weathering of silicates (monosiallitization). This work demonstrates that although hydrogeochemical evolutionary trends may vary with local climate and lithology, the fundamental similarities in global tectonic settings can still lead to the elevated concentrations of groundwater As.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Engström, Emma, 1982-
(författare)
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Predicting the transport of Escherichia coli to groundwater
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Groundwater contamination with pathogens poses a health risk worldwide. Predictive modeling could provide decision support for risk analysis in this context. This study therefore aimed to improve predictive modeling of the transport of Escherichia coli (E. coli) to groundwater. Primarily, it included a review of the state-of-the-art of the underlying process, influencing factors and modeling approaches that relate to E. coli transport in the unsaturated zone. Subsequently, two recently developed models were innovatively applied to the context of microbial contamination. The Active Region Model was evaluated as an alternative to the traditional, uniform flow model (Richard’s equation) to describe bacterial transport in a wastewater treatment facility. It resulted in removal rates that were two orders of magnitude smaller than the traditional approach, more consistently with observations. The study moreover assessed the relevance of a spatial probit model to estimate the probability of groundwater source contamination with thermotolerant coliforms in a case study in Juba, South Sudan. A conventional probit regression model resulted in spatially auto-correlated residuals, pointing to that the spatial model was more accurate. The results of this approach indicated that the local topography and the near presence of areas with informal settlements (Tukul zones) were associated with contamination. Statistical analyses moreover suggested that the depth of cumulative, long-term antecedent rainfall and on-site hygiene were significant risk factors. The findings indicated that the contributing groundwater was contaminated in Juba, and that contamination could be both local and regional in extent. They are relevant for environments with similar climatic, hydrogeological and socioeconomic characteristics, which are common in Sub-Saharan Africa. The results indicated that it is important to consider spatial interactions in this subject area. There is a need for studies that assess the distance within which such interactions can occur, using both mechanistic and statistical methods. Lastly, the results in this study consistently emphasized the importance of flow patterns for E. coli transport. It is thus recommended that future studies evaluate how models of preferential flow and transport can incorporate microbial fate. The multidisciplinary nature of the subject calls for a systems approach and collaboration between disciplines.
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| 12. |
- Engström, Emma, et al.
(författare)
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Prevalence of microbiological contaminants in groundwater sources and risk factor assessment in Juba, South Sudan
- 2015
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Ingår i: Science of the Total Environment. - : Elsevier B.V.. - 0048-9697 .- 1879-1026. ; 515-516, s. 181-187
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Tidskriftsartikel (refereegranskat)abstract
- In low-income regions, drinking water is often derived from groundwater sources, which might spread diarrheal disease if they are microbiologically polluted. This study aimed to investigate the occurrence of fecal contamination in 147 improved groundwater sources in Juba, South Sudan and to assess potential contributing risk factors, based on bivariate statistical analysis. Thermotolerant coliforms (TTCs) were detected in 66% of the investigated sources, including 95 boreholes, breaching the health-based recommendations for drinking water. A significant association (p<. 0.05) was determined between the presence of TTCs and the depth of cumulative, long-term prior precipitation (both within the previous five days and within the past month). No such link was found to short-term rainfall, the presence of latrines or damages in the borehole apron. However, the risk factor analysis further suggested, to a lesser degree, that the local topography and on-site hygiene were additionally significant. In summary, the analysis indicated that an important contamination mechanism was fecal pollution of the contributing groundwater, which was unlikely due to the presence of latrines; instead, infiltration from contaminated surface water was more probable. The reduction in fecal sources in the environment in Juba is thus recommended, for example, through constructing latrines or designating protection areas near water sources. The study results contribute to the understanding of microbiological contamination of groundwater sources in areas with low incomes and high population densities, tropical climates and weathered basement complex environments, which are common in urban sub-Saharan Africa.
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| 13. |
- Engström, Emma, et al.
(författare)
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Water Transport, Retention, and Survival of Escherichia coli in Unsaturated Porous Media : A Comprehensive Review of Processes, Models, and Factors
- 2015
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Ingår i: Critical reviews in environmental science and technology. - : Informa UK Limited. - 1064-3389 .- 1547-6537. ; 45:1
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Forskningsöversikt (refereegranskat)abstract
- The vadose zone can function as both a filter and a passage for bacteria. This review evaluates when and why either effect will apply based on available literature. It summarizes theories and experimental research that address the related, underlying bacterial attenuation processes, the applied macro-scale modeling approaches, and the influencing factors - including the cell, soil, solution and system characteristics. Results point to that the relative importance of each removal mechanism depends on the moisture content and the solution ionic strength. The limitations of available modeling approaches are discussed. It remains unclear in which contexts these are reliable for predictions. The temporal first-order kinetic Escherichia coli (E. coli) removal coefficient ranges three orders of magnitude, from 10(-4) to 10(-1)/min. Results suggest that this rate depends on the pore-water velocity. Spatial filtration of E. coli increases with slower flow and higher collector surface heterogeneity. It could be insignificant in the case of heavy and sudden infiltration and subsequent transport in preferential flow paths, induced, for example, by plant roots or cracks in clayey soils. Future research thus needs to address transport as an effect of extreme weather events such as droughts and subsequent floods.
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| 14. |
- Hamisi, Rajabu, 1978-, et al.
(författare)
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A new modelling approach for phosphorus mobility and retention processes in the Oxundaån catchment, Sweden
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Eutrophication is the most significant threat towater quality in the entire Baltic Sea region. Its causes are nutrientover-enrichment from diffuse and point sources. Thematic strategies forsustainable mitigation of phosphorus loss from sewage drainage systems andrunoffs from arable land require a holistic approach to identify the criticalpolluting sources and implement relevant policy for adaptive water qualitymanagement. The use of constructed wetlands constitutes one such strategy thatcan mitigate phosphorus loss. However, insufficient understanding about phosphorusmobility and retention in catchments significantly hinders efforts to identifysuitable sites for constructed wetlands and implement alternative, adaptive andeffective management actions. This study aims to evaluate the long-termphosphorus mobility and retention in the Oxudaån catchment in Sweden, andthereby propose suitable sites to localize constructed wetlands. The Soil andWater Assessment watershed model was applied to map and quantify the phosphorusloading from diffuse and point sources under the scenarios of land usemanagement practices. Simulation results have demonstrated the positivecorrelation between the phosphorus concentration with the surface runoffs andnegative correlation with the pH. Overall, Oxundaån catchment indicates a decreasingtrend of phosphorus loading in the Verkaån and Oxundaån riverine of around 2.1% and 1.3 % per year, respectively. The present study suggests the suitablesites for localizing constructed wetlands in the south-west and north-east ofOxundaån lake based on the factor of low slope topography and soilpermeability. The simulation results from the SWAT model offer evidence thatcan guide the localization and choice of management interventions to achieve asustainable mitigation of phosphorus loss. This study concludes that, while singlemanagement actions can help solve the problem of eutrophication, a moreeffective and sustainable mitigation of eutrophication will require the integrationof multiple adaptive land use management approaches.
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| 15. |
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| 16. |
- Hamisi, Rajabu, et al.
(författare)
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Long-term phosphorus sorption and leaching in sand filters for onsite treatment systems
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 833, s. 155254-155254
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Tidskriftsartikel (refereegranskat)abstract
- The sorption capacities of sand filters used for onsite wastewater treatment and their associated risks of phosphorus (P) leaching on contact with rainwater were investigated in column experiments and with modelling tool for over 300 days. Columns packed with sand were exposed to real domestic wastewater of different characteristics and hydraulic loading modes. The wastewater fed into the columns was effluent collected from three different treatment units in the field: a septic tank (ST), biofiltration tank (BF) and Polonite® filter bag (PO). The risk of P leaching to groundwater and surface water was also assessed, by exposing the same sand columns to natural rainwater. Overall results indicated that sand soils can exhibit different adsorption and desorption capacities for electrical conductivity (EC), Total-P, phosphate-P and total suspended solids, depending on the characteristics of influent wastewater, loading rate and total operation time. The removal efficiencies of the sand columns increased in the order ST (98.16 %) > PO (93.36%) > BF (81.57%) for PO4-P and slightly decreased ST (97.11 %) > PO (92.06%) > BF (76.76%) for Total-P columns. All sand columns loaded with actual wastewater solutions from septic tanks and biofiltration tank have demonstrated high risks of phosphorus leaching (> 99.99%) to the groundwater. The modelling was successful captured behavior of EC tracer and adsorption of PO4-P with acceptable prediction uncertainty in the PO < 8% columns. The modelling results indicated that the decrease of loading rate from 83.3 mL d-1 to 20.83 mL d-1 led to an average increase of removal efficiency and prolong operational lifetime and mass of adsorbed Total-P in the sand soil. This study concludes that sand is a valuable filter medium at low loading rate for phosphorus removal in full-scale operations of onsite treatment systems, however very vulnerable for leaching P when in contact with rainwater.
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| 17. |
- Hamisi, Rajabu, 1978-
(författare)
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Modelling phosphorus dynamics in constructed wetlands upgraded with reactive filter media
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Developing low-cost and effective technologies to upgrade phosphorus (P) removal from the catchment runoffs and rural wastewater treatment facilities is one of the main research agendas to save the Baltic Sea from eutrophication. In Sweden, the construction of the constructed wetlands has been one of the environmental objectives for wastewater quality improvement in the small communities. However, the insufficiently understanding of the mechanisms underlying the process of phosphorus mobility and sorption in the constructed wetlands has limited design of the effective constructed wetlands. To provide the better understanding of sorption process in the catchment and constructed wetland system, this thesis used the GIS-based Soil and Water Assessment Tool (SWAT) to predict phosphorus mobility and identify the critical diffusing sources of phosphorus loss in the Oxunda catchment (Paper I). Then, the study developed the three-dimensional numerical Reactive TRAnsPort Model (RETRAP - 3D) in the COMSOL Multiphysics® for evaluating the long - term sorption processes and removal efficiencies of the porous reactive media for upgrading the performance of constructed wetlands (Paper II and III). The latter model coupled many physics equations to solve process of water flow, reaction kinetics and solute transport in the porous reactive adsorbent media for application in the constructed wetlands. The data from the field measurements and column experiments have been used to demonstrate the model simulation accuracy to capture the process of phosphorus sorption in the real environment. Modeling results ranked the phosphorus removal efficiency of the adsorbent media as follows: Polonite® (88 %), Filtralite P® (85%), BFS (62%), Wollastonite (57 %). The satisfactory agreement which obtained between the simulated outputs and measured data confirmed that the SWAT and RETRAP-3D are useful tools for describing various processes in the complicated system. However, further study is required to generate and validate more experimental data to evaluate the sensitivity of local parameters.
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| 18. |
- Hamisi, Rajabu, 1978-, et al.
(författare)
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Modelling phosphorus recovery by reactive adsorbent in a vertical subsurface flow constructed wetland
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Phosphorus removal efficiencies by four low - costsreactive adsorbent media were evaluated in the long - time period using thethree - dimensional model of the vertical subsurface flow constructed wetlandsin the COMSOL Multiphysics® software. Evaluations were made for Polonite,Filtralite P, Sorbulite and Wollastonite adsorbent media with the aims ofpredicting their long - term sorption capacity and describing the phenomena ofsorption mechanisms when applied in the vertical subsurface flow constructedwetlands for wastewater purification. The 3D model of the vertical flowconstructed wetlands were dimensioned to Swedish EPA guidelines for small scalewastewater treatment, and calibrated at saturated media using the breakthroughdata derived from the column experiments of similar adsorbent mediaapplication, and the local sensitivity analysis were performed for waterquality and hydraulic loading parameters. It was observed that the breakthroughcurves developed by model were significantly correlated to the experimentaldata. The overall findings showed that Polonite® could be the potentialreactive adsorbent for phosphorus removal in the VF-CWs application, and itsremoval efficiency was discovered to last for 5 years. The large variation ofmedia sorption capacities discovered to be affected more by factor of pH andhydraulic loading rates than the particle size. High degree of predictionaccuracy which is demonstrated by this model suggest that the proposed model isa useful tool for predicting pollutants removal in various reactive porousmedia.
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| 19. |
- Hamisi, Rajabu, et al.
(författare)
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Optimization of on-site wastewater treatment efficiency and recovery based on nutrient mobility and adsorption kinetics modelling using HYDRUS-2D coupled with PHREEQC
- 2024
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 492
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Tidskriftsartikel (refereegranskat)abstract
- A closed-loop on-site wastewater treatment system (OWT) was studied comprising steps of septic tank to remove organics (Biological Oxygen Demand (BOD)), biofiltration clarifier for biological removal of nitrogen (N), phosphorus (P) and BOD, reactive Polonite® filter for chemical adsorption and precipitation removal of dissolved P, and tidal flow constructed wetland (TFCW) sand filter for polishing the effluent to low P and N effluent Swedish standards. The field experimental data that have been used to optimize TFCW design in the numerical modelling using HYDRUS-2D coupled with and without PHREEQC indicated that the adsorption efficiency of the reactive Polonite® adsorbent was nearly double to that obtained in TFCW sand filters for PO4-P (95 %) and Total-P (85 %) removal in summer at a high temperature range (15.4–18.8 °C) and pH range (9.9–10.8). The weaker PO4-P (53 %) and Total-P (25 %) removal efficiency in winter was due to a low temperature (1.5–8.1 °C) and low pH (7.2–7.9). This decrease in pH was attributed to salinity in the domestic wastewater and dilution of rainwater. Modelling results revealed that the transport mechanisms and rate of P adsorption kinetics in the TFCW sand filters enhanced with calcium and iron flow from chemical dissolution in the preceding Polonite® adsorbent was increased with the increase in temperature. However, the P adsorption was less sensitive at high ferrihydrite (Fe(OH)3) dose, suggesting limited effects of cations dissolution and abundance of metal oxides and hydroxide ions at the mineral surface for anions exchange with phosphate for surface complexation. The strategy of combining field data and modelling provided valuable insights for assessing adaptability and optimizing TFCW design under variable fluxes and scenario effects of insulated/uninsulated and dilution by rainwater in cold-climate regions.
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| 20. |
- Hamisi, Rajabu, et al.
(författare)
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Performance of a tidal flow constructed wetland used for post-treatment of on-site wastewater in cold climate
- 2022
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Ingår i: Journal of Water Process Engineering. - : Elsevier BV. - 2214-7144. ; 47
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Tidskriftsartikel (refereegranskat)abstract
- The performance of a tidal flow constructed wetland (TFCW) following wastewater treatment in a package plant designed for two households was studied in a nine-month field trial and its design evaluated through process modelling and pumping tests. The TFCW is operated by filling and draining periods lasting five to nine days, depending on wastewater production by users. The effects of passive aeration, temperature, influent concentration of nutrients and bacteria as well as hydraulic loading on the treatment efficacy of the TFCW system were studied. Results showed that the TFCW system removed ammonium-nitrogen (NH4-N, 76%), phosphate -phosphorus (PO4-P, 56%), total inorganic nitrogen (TIN, 28%) and reduced water pH by15%. The removal efficiency of TIN was significantly improved in the summer (> 50%). The average influent concentration of total phosphorus (TP) was low after the preceding package plant treatment (1.12 mg L-1), but the TFCW showed ability to further reduce TP to the average concentration of 0.57 mg L-1. A coupled reactive transport model was developed in the COMSOL Multiphysics (R) 5.6 software to predict processes of water flow and was validated against the actual data from the field. The modelling exhibited a satisfactory prediction accuracy and capability to capture behavior of effluent PO4-P, NH4-N and dissolved oxygen concentration. Moreover, modelling processes helped to understand the defects of water flow and adsorption processes within the treatment wetland.
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| 21. |
- Hamisi, Rajabu, 1978-, et al.
(författare)
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Reactive transport modelling of long-term phosphorus dynamic in the compact constructed wetland using COMSOL Multiphysics
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Ingår i: Ecological Engineering Journal.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A three-dimensional reactive transport model (RETRAP-3D) was developed by this study in the COMSOL Multiphysics®software to evaluate the long-term sorption capacity and mechanisms of dissolved reactive phosphorus removal in reactive adsorbent. The model coupledphysics interfaces for water flow, transport of reactive species, reaction kinetics for chemical compositions and biofilm development. Simulations were conducted for Polonite®, Filtralite P®, and Blast Furnace Slag mediaat fully saturated media, equilibrium miscible solution and isothermal heat transfer conditions. The model was validated using column experimental data ofsimilar media for application in constructed filter beds. The general modelling results showed good agreement with the measured breakthrough data. The most significant DIP retention capacity (P < 0.02) and longest residence time(1250 days) has been found for Polonite® and the most insignificant DIP retention for blast furnace slag (P > 0.54). The DIP removal was significantly correlated to factors of pH change, media characteristics, hydraulic dosage and retention times. These results demonstrate the reliability of the model as aflexible tool to predict the long-term performance of filter media and better understand processes within the system under various operational, weather and wastewater conditions.
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| 22. |
- Hamisi, Rajabu, et al.
(författare)
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Treatment efficiency and recovery in sand filters for on-site wastewater treatment: Column studies and reactive modelling
- 2024
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Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 462
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Tidskriftsartikel (refereegranskat)abstract
- This study examined the adsorption capacity and treatment efficiency of sand filters in on-site treatment systems for cold climate regions. The effects of different operating conditions, porosity and kinetics parameters were investigated in column experiments and COMSOL Multiphysics® modelling, to comprehensively reveal the mechanisms and optimize treatment efficiency of nitrogen (N) and phosphorus (P) removal in a field tidal flow constructed wetland (TFCW), treating effluent from a package treatment plant with P filter material. The results from column experiments with sand showed that Total-P adsorption rate was dependent on feed water quality (Septic tank >0.77 ± 0.06 g kg−1; Biotreatment >0.41 ± 0.07 g kg−1; Reactive material Polonite® <0.18 ± 0.07 g kg−1). In the field TFCW trial, Total-P adsorption in the top layer (>1.42 ± 0.55 g kg−1) and middle layer (>1.06 ± 0.51 g kg−1) was twice that in laboratory columns, due to strong interaction with the air-water interface and use of fluctuated domestic wastewater solutions. The breakthrough curve (BTCs) of the coarse sand matched the physical behaviour of tracer electrical conductivity (EC) in effluent from the sand column experiments. The modelling results demonstrated that high filter porosity and low hydraulic load were significant factors for optimal removal of NH4–N, Total-N, PO4–P, Total- P in the top layer (>99.95 ± 0.03 %, 44.37 ± 28.75%, 70.89 ± 28.30%, 76.18 ± 20.3%), middle layer (>98.94 ± 1.77%, 18.23 ± 23.04%, 76.62 ± 28.73%, 65.40 ± 31.85%) and deep layer (>99.99 ± 0.02%, 65.50 ± 20.64%, 75.53 ± 23.16%, 41.54 ± 28.81%) in the TFCW system, respectively. The results show that on-site wastewater treatment in cold climate TFCW can be applied as a technology to polish effluent from a three-step pretreatment system. However, hydraulic optimization is an important factor for the design of the TFCW to receive a successful long-term operating system.
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| 23. |
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| 24. |
- Kizito, Frank, et al.
(författare)
-
A web-based Customer Account Management portal for an urban water utility in Uganda
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The Kampala Water Supply Service Area (KWSSA) is one of twenty-two urban centres managed by theNational Water and Sewerage Corporation (NWSC), a public utility owned by the Government of Uganda. Owing to the size of the city and the scope of operations, management of KWSSA is decentralized to eleven administrative units referred to as Branches, which in turn are further subdivided into smaller geographical units, called Territories. “Territorial Management”, a concept practiced within KWSSA, involves sub-division of the area ofoperation of a utility into geographical units small enough for a designated individual, the TerritorialManager (TM), to gain a personal knowledge of, and greater contact with, the customers within hisjurisdiction. This closer focus should, in principle, enable the TM to better control aspects of water sales and revenue collection within his territory, and at the same time make him more directly accountable forits performance relative to that of the company as a whole. Proper territorial management should act bothas an incentive for competition amongst territories (leading to global performance gains) and a basis forreward of exceptional achievers. This paper describes the establishment of a web portal providing an integration framework for various GIS tools and services designed to support territorial customer account management within KWSSA. Inthe paper, a geodatabase has been established for a selected “Model Branch”, and a set of prototype webmappingapplications designed and implemented. These tools provide functionality for tracking the connection status of individual customers, their consumption and payment histories, as well as complaints received from the customers. The various tools have been brought together within a single vertical webportal, which also provides links to other kinds of information as well as customized content aggregations(mash-ups) relating to the organization.
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| 25. |
- Kizito, Frank, et al.
(författare)
-
Bridging the gap between academic research and technological practice: Roles, benefits and pitfalls of action research in information systems development
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper highlights the shortfalls of traditional approaches to academic research in the technological sciences, with respect to their failure to effectively impact on practice and tosupport joint learning between academicians and practitioners. Action Research (AR) is proposedas a suitable way of bridging this gap. AR is an inquiry process that involves partnership between researchers and practitioners for the purpose of addressing a real life problem issue, while simultaneously generating scientific knowledge. It is recognized that AR methods provide apotential avenue to improve the practical relevance of Information Systems (IS) research. An ARapproach has been used in an ongoing study involving the development of Decision SupportSystems (DSS) for water supply management in Uganda. The study seeks to explore how thedegree of adoption of DSS in practice, generally perceived to be low, may be improved.However, AR is not without its challenges, many of which are both contextual and emergent innature, and these are highlighted in the paper. The case study thus provides an opportunity, notonly to carry out research specific to the particular field of study (IS development), but also to reflect on the roles, benefits and pitfalls of AR as a research approach.
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| 26. |
- Kizito, Frank, et al.
(författare)
-
Development of decision support tools for decentralised urban water supply management in Uganda : An action research approach
- 2009
-
Ingår i: Computers, Environment and Urban Systems. - : Elsevier BV. - 0198-9715 .- 1873-7587. ; 33:2, s. 122-137
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study in which four real-life problem situations are used to explore the challenges of developing and implementing decision support tools within air urban water utility. In the Study, all Action Research approach is used. with theoretical considerations leading to specific actions being implemented, which ill turn yield results that are used to reflect upon the original theoretical assumptions. Results of the study emphasize the need for proper problem-structuring prior to the formulation of actions, the challenges of moving from planning to action; the importance of User involvement in the development of tools; and how a good match of people, problem-structuring, proactiveness and participatory tools development is required for effective decision support provision. The study also highlights the challenges of embedding decision support within existing work systems ill organizations. The Action Research approach is shown to be useful in bridging the gap between theory and practice, aiding the development of decision Support tools of immediate and practical benefit to organizations.
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| 27. |
- Kizito, Frank, 1970-
(författare)
-
Development of Decision Support Tools for Urban Water Supply Management in Uganda
- 2008
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this study, five real-life problem situations were used to explore the challenges of developing and implementing decision support tools for management of an urban water utility in Uganda. The study sought to explore how the degree of adoption of formal decision support tools in practice, generally perceived to be low, could be improved. In the study, an Action Research (AR) approach was used. AR is an inquiry process that involves partnership between researchers and practitioners for the purpose of addressing a real-life problem issue, while simultaneously gener-ating scientific knowledge. Unlike other research methods where the researcher seeks to study organizational phenomena but not to change them, the action researcher attempts to create or-ganizational change and simultaneously to study the process. It is recognized that AR methods provide a potential avenue to improve the practical relevance of Information Systems (IS) re-search. The five cases that were considered in the study involved participatory problem structuring to address water distribution bottlenecks; identification of Non-Revenue Water (NRW) reduction strategies; facilitation of decentralized management of customer accounts; monitoring and con-trol of procurements and expenditure; and geospatial investigation of declining water sales. Dur-ing the study, participation in problem identification was achieved through discussions and brain-storming sessions bringing together top and middle managers within the organization. A number of prototype decision support tools were developed and implemented. Maps and other geovisu-alization tools were also used to inform and enhance the processes of collective problem identifi-cation and structuring. Results of the study emphasized the need for proper problem structuring prior to the formula-tion of actions; the challenge of moving from planning to action; the importance of user in-volvement in the development of tools; and the need to manage IS implementation as part of a holistic, organization-wide change process. The challenges of embedding formal decision support within existing work systems in organizations were highlighted, and recommendations were made on how best to achieve this. The AR approach was found to be useful in bridging the gap be-tween academic research and technological practice, thus supporting the development of IS with immediate and practical benefits to organizations.
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| 28. |
- Kizito, Frank, et al.
(författare)
-
Exploring “commercial” water losses in an urban water supply system in Uganda : A geostatistical modeling approach
- 2008
-
Ingår i: Applied Spatial Analysis and Policy. - 1874-463X.
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Like many urban water utilities, Kampala Water (KW) in Uganda has faced challenges in dealing with Non-Revenue Water, defined as the difference between water produced and water sold. One particular challenge has been in quantifying and localizing the “apparent” or “commercial” losses fraction of the water balance relating to the KW service area. This paper presents a study in which geostatistical modelling was used to investigate the possible causes of stagnation in watersales volumes within a selected part of the KW service area, despite continued growth in thecustomer base resulting from connection of new customers. In the study, a variogram model ofwater sales volumes was established. This model was then used to predict water sales volumes ona raster grid throughout the study area. The predicted volumes were compared with actual watersales for a selected period, and a difference map was generated. Subsequently, post plots of thelocations of various reported field anomalies (aged and defective meters, water supplyinsufficiencies, leaks, illegal consumption, disconnected accounts, and accounts billed onestimated consumption) were overlaid in turn on the difference map of water sales volumes.These map overlays were used to explore the spatial correlations between the prevalence of thedifferent categories of field anomalies and occurrences of large differences between actual andpredicted water sales volumes. The comparisons served to highlight the locations and possiblecauses of significant drops in water sales volumes. Through the study, a geostatistical analysis toolwas developed consisting of computer code written using R, an open-source statistical computingand graphics language and environment. This tool will be incorporated as a module within aspatial decision support system prototype being developed for the KW service area.
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| 29. |
- Kizito, Frank, et al.
(författare)
-
Hydraulic modelling as a tool for problem analysis and decision support : Case study of the Naguru water supply system in Uganda
-
Ingår i: Journal of Hydroinformatics. - 1464-7141 .- 1465-1734.
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes a study in which hydraulic modeling was applied as a tool to guide planningand decision-making to address water distribution bottlenecks within an urban water supplysystem in Uganda. In response to chronic supply intermittencies and an ever-increasing outcryfrom affected customers, a number of interventions were proposed - and some implemented -formulated largely based on intuition, rule-of-thumb, and experience of the network operationalstaff. However, in recognition of the constraints of this approach in the face of an increasinglycomplex and ever-expanding network, a more rigorous and scientific approach was applied, inwhich simulation modeling was used to evaluate system performance under the various proposed interventions. Model results indicated that most of the proposed alternatives, including those thathad already been implemented, would yield unsatisfactory performance in the medium to longterm, albeit providing minimal relief in the short term. The study thus demonstrated the importance of application of formal tools such as hydraulic modeling as a replacement for moreintuitive and judgment-based network management approaches, especially given the large,complex and problem-prone water supply systems characteristic of urban utilities in developingcountries.
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| 30. |
- Kizito, Frank, et al.
(författare)
-
Using geovisualisation to support participatory problem structuring and decision making for an urban water utility in Uganda
- 2008
-
Ingår i: Applied GIS. - 1832-5505. ; 4:2, s. 1-33
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes the application of geovisualisation to facilitate participatory identification and structuring of problems in an urban water supply system in Uganda. The city of Kampala has experienced rapid expansion over the years, with a corresponding increase inthe demand for piped water supply. However, this demand was not well matched with expansion of the water supply system, and as a result parts of the city have been facingchronic supply anomalies and insufficiencies. Faced with the task of identifying remedies to theproblems in the system, the city water company undertook a formal participatory problemstructuring and decision analysis process, to try and understand the underlying causes of system failures as well as the geospatial patterns of these failures. As part of this process,analysis, mapping and geovisualisation of data derived from historical records of waterconsumption, as well as records of pipe breakages, supply intermittences, and other recordedcustomer complaints, was done. The maps so produced were key in bringing the variousstakeholders and decision makers to a common understanding of the problem issues, andhelped in the formulation of alternative courses of action. Furthermore, with the establishment of a formal discussion forum for problem analysis and decision making, structured participatory decision making was entrenched within the company’s work ethos. It is hoped that in future,the coupling of the geovisualisation tools with the existing operational databases in thecompany will result in the development of a functional spatial decision support system and adynamic framework for system performance monitoring and reliability assessment.
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| 31. |
- Kizito, Frank, 1970-
(författare)
-
Water supply management in an urban utility : A prototype decision support framework
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this study, four real-life problem situations were used to explore the challenges of developing and implementing decision support tools for planning and management within an urban water utility. The study sought to explore how the degree of adoption of formal decision support tools in practice, generally perceived to be low, could be improved. In the study, an Action Research (AR) approach was used. AR is an inquiry process that involves partnership between researchers and practitioners for the purpose of addressing a real-life problem issue, while simultaneously generating scientific knowledge. Unlike other research methods where the researcher seeks to study organizational phenomena but not to change them, the action researcher attempts to create organizational change and simultaneously to study the process. During the study, a number of prototype data management tools were developed. GIS-based spatial analysis and visualisation tools were extensively used to inform and enhance the processes of participatory problem identification and structuring, while a number of modelling tools were applied in the generation and evaluation of alternative solutions. As an outcome of the study, a prototype framework for the application of decision support tools within an urban water supply planning and management context was proposed. The study highlighted the challenges of embedding formal decision support processes within existing work systems in organizations, and recommendations were made on how best to achieve this. The AR approach was found to be useful in bridging the gap between academic research and technological practice, supporting the development of computerised planning and decision support tools of practical benefit to organizations.
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| 32. |
- Kizito, Frank, et al.
(författare)
-
When Action Plans Yield No Actions : Challenges of ImplementingNon-Revenue Water Reduction Strategies in an Urban Water Utilityin Uganda
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The classical approach to water loss management in a piped water supply system is to gain anunderstanding of the underlying factors contributing to losses, both physical and non-physical,within the system, and there after to formulate and implement strategies and actions aimed attackling these underlying causes. However, undertaking extensive root-cause analysis, and generating detailed Action Plans as an output of this process, does not in itself guaranteeeffective redress in the face of high system losses, nor do detailed Action Plans automatically translate into effective remedial actions. Based on experiences within a real-life organization, this paper explores the challenge of moving from planning to action and from problem analysis to theeffective implementation of identified solutions, and a number of prerequisites to achieving this end are proposed.
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| 33. |
- Kulabako, N. R., et al.
(författare)
-
Phosphorus transport in shallow groundwater in peri-urban Kampala, Uganda : results from field and laboratory measurements
- 2008
-
Ingår i: Environmental Geology. - : Springer Science and Business Media LLC. - 0943-0105 .- 1432-0495. ; 53:7, s. 1535-1551
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 34. |
- Kulabako, N. R., et al.
(författare)
-
Study of the impact of land use and hydrogeological settings on the shallow groundwater quality in a peri-urban area of Kampala, Uganda
- 2007
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 381:03-jan, s. 180-199
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 35. |
- Kulabako, Robinah, 1971-
(författare)
-
Analysis of the impact of anthropogenic pollution on shallow groundwater in peri-urban Kampala
- 2005
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 36. |
- Kulabako, Robinah, 1971-
(författare)
-
Environmental sanitation situation and solute transport in variably saturated soil in peri-urban Kampala
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
- Kulabako, Robinah Nakawunde, et al.
(författare)
-
Environmental health practices, constraints and possible interventions in peri-urban settlements in developing countries - a review of Kampala, Uganda
- 2010
-
Ingår i: International Journal of Environmental Health Research. - : Informa UK Limited. - 0960-3123 .- 1369-1619. ; 20:4, s. 231-257
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 41. |
- Kulabako, R. N., et al.
(författare)
-
Numerical modeling for preliminary assessment of natural remediation of phosphorus in variably saturated soil in a peri-urban settlement in Kampala, Uganda
- 2011
-
Ingår i: Geochemical Modeling of Groundwater, Vadose and Geothermal Systems. - : CRC Press. - 9781439870532 - 9781138074446 ; , s. 267-283
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The limited financial and technological resources available to clean polluted aquifers particularly in the developing countries such as in Sub-Saharan Africa where degradation of groundwater is recognized as one of the most serious water resources problem implies that contamination of groundwater resources remains a growing public health hazard (Xu and Usher, 2006). In this case, natural attenuation (or monitored natural attenuation-MNA) appears to be a possible contaminated land management option necessitating investigation. Attenuation is generally most effective in the unsaturated (vadose) zone.
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| 42. |
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| 43. |
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| 44. |
- Kumar, Manish, et al.
(författare)
-
Arsenic enrichment in groundwater in the middle Gangetic Plain of Ghazipur District in Uttar Pradesh, India
- 2010
-
Ingår i: Journal of Geochemical Exploration. - : Elsevier BV. - 0375-6742 .- 1879-1689. ; 105:3, s. 83-94
-
Tidskriftsartikel (refereegranskat)abstract
- Groundwater with high geogenic arsenic (As) is extensively present in the Holocene alluvial aquifers of Ghazipur District in the middle Gangetic Plain, India. A shift in the climatic conditions, weathering of carbonate and silicate minerals, surface water interactions, ion exchange, redox processes, and anthropogenic activities are responsible for high concentrations of cations, anions and As in the groundwater. The spatial and temporal variations for As concentrations were greater in the pre-monsoon (6.4-259.5 mu g/L) when compared to the post-monsoon period (5.1-205.5 mu g/L). The As enrichment was encountered in the sampling sites that were close to the Ganges River (i.e. south and southeast part of Ghazipur district). The depth profile of As revealed that low concentrations of NO3- are associated with high concentration of As and that As depleted with increasing depth. The poor relationship between As and Fe indicates the As release into the groundwater, depends on several processes such as mineral weathering, O-2 consumption, and NO3- reduction and is de-coupled from Fe cycling. Correlation matrix and factor analysis were used to identify various factors influencing the gradual As enrichment in the middle Gangetic Plain. Groundwater is generally supersaturated with respect to calcite and dolomite in post-monsoon period, but not in pre-monsoon period. Saturation in both periods is reached for crystalline Fe phases such as goethite, but not with respect to poorly crystalline Fe phases and any As-bearing phase. The results indicate release of arsenic in redox processes in dry period and dilution of arsenic concentration by recharge during monsoon. Increased concentrations of bicarbonate after monsoon are caused by intense flushing of unsaturated zone, where CO2 is formed by decomposition of organic matter and reactions with carbonate minerals in solid phase. The present study is vital considering the fact that groundwater is an exclusive source of drinking water in the region which not only makes situation alarming but also calls for the immediate attention.
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| 45. |
- Lindström, Riitta, 1957-
(författare)
-
Groundwater vulnerability assessment using process-based models
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus of this thesis is on groundwater vulnerability assessment by process-based simulation models and data acquisition for these assessments. A modelling system for intrinsic groundwater vulnerability assessment in water supply areas was developed, consisting of flow- and transport models for the unsaturated zone and the groundwater zone, coupled to a geographical informa-tion system. The system was applied to a water supply area located close to a major road south of Stockholm. Chloride was used as an indicator in determining the vulnerability for groundwater contamination from the road. The approach was useful to illustrate the dynamic change of chlo-ride concentrations both during the stage of continuous application and after the applications was terminated. A structure and content of a database for flow and transport modelling, based on hydrogeological environments, was outlined. An existing hydrogeological parameter database, HPAR at the Geological Survey of Sweden (SGU), was examined as a potential source of data for the new database. Values for some important parameters needed for groundwater modelling, such as hydraulic conductivity and effective porosity, were lacking in the three municipal HPAR databases that were studied. It was suggested that these data should be added, together with information on the hydrogeological environments, for all geographical positions of interest. Without such minimum information, the efficient use of modelling tools could not be expected. Typical profiles of three common Swedish hydrogeological environments (sand deposits, glacial till and clay covered areas) were used to represent generic input data to model simulations in the unsaturated zone so that the importance of soil, vegetation type and groundwater levels on turn-over times of conservative contaminants transported by natural recharge could be examined. The same profiles were used to predict the penetration depth of accidental liquid spills that occur at the land surface level. In the case of contaminant transport by natural recharge, water storage in the soil profile and vegetation type played an important role for turnover times. For liquid spills, the hydraulic con-ductivity was found to be of major importance, while the water retention properties were of less importance. Modelling, together with available data sources, were successfully used to demon-strate the vulnerability of different environmental conditions.
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| 46. |
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| 47. |
- Maity, Jyoti Prakash, et al.
(författare)
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Arsenic-enriched groundwaters of India, Bangladesh and Taiwan-Comparison of hydrochemical characteristics and mobility constraints
- 2011
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Ingår i: Journal of Environmental Science and Health. Part A. - : Informa UK Limited. - 1093-4529 .- 1532-4117. ; 46:11, s. 1163-1176
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic (As) enrichment in groundwater has become a major global environmental disaster. Groundwater samples were collected from 64 sites located in the districts of 24-Parganas (S), and Nadia in West Bengal, India (Bhagirathi sub-basin), and 51 sites located in the districts of Comilla, Noakhali, Magura, Brahman baria, Laxmipur, Munshiganj, Faridpur and Jhenaida in Bangladesh (Padma-Meghna sub-basin). Groundwater samples were also collected from two As-affected areas (Chianan and Lanyang plains) of Taiwan (n = 26). The concentrations of major solutes in groundwater of the Padma-Meghna sub-basin are more variable than the Bhagirathi sub-basin, suggesting variations in the depositional and hydrological settings. Arsenic concentrations in groundwaters of the studied areas showed large variations, with mean As concentrations of 125 mu g/L (range: 0.20 to 1,301 mu g/L) in Bhagirathi sub-basin, 145 mu g/L (range: 0.20 to 891 mu g/L) in Padma-Meghna sub-basin, 209 mu g/L (range: 1.3 to 575 mu g/L) in Chianan plain, and 102 mu g/L (range: 2.5 to 348 mu g/L) in Lanyang plain groundwater. The concentrations of Fe, and Mn are also highly variable, and are mostly above the WHO-recommended guideline values and local (Indian and Bangladeshi) drinking water standard. Piper plot shows that groundwaters of both Bhagirathi and Padma-Meghna sub-basins are of Ca-HCO(3) type. The Chianan plain groundwaters are of Na-Cl type, suggesting seawater intrusion, whereas Lanyang plain groundwaters are mostly of Na-HCO(3) type. The study shows that reductive dissolution of Fe(III)-oxyhydroxides is the dominant geochemical process releasing As from sediment to groundwater in all studied areas.
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| 48. |
- Mukherjee, A., et al.
(författare)
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Wide spread arsenic in deeper groundwater of western Bengal basin, West Bengal, India : Implications for sustainable alternate drinking water sources
- 2012
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Ingår i: Understanding the Geological and Medical Interface of Arsenic, As 2012. - : Taylor & Francis Group. ; , s. 522-525
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Konferensbidrag (refereegranskat)abstract
- Availability of safe drinking water is a major concern in the delta plains of the major Himalayan-Tibetan rivers in southern and southeastern Asia. While indiscriminate use of rivers and other surface water bodies for disposal of sewage and industrial waste has rendered them non-potable, natural, non-point source, elevated Arsenic (As) concentrations in groundwater exceeding the World Health Organization's (WHO) guideline value for drinking water of 0.01 mg/L have put millions of people at risk. Hence, finding an alternate, suitable and sustainable drinking-water source has been a priority in these areas. Generally, higher concentrations of dissolved As are found in groundwater of shallower aquifers and several studies have advocated deeper aquifers as a possible safe substitute. Using a composite hydrogeological approach, we demonstrate that regional-scale deeper groundwater As contamination in the western Bengal basin is dependent on the aquifer-aquitard framework and complex redox processes with partial equilibrium under natural flow conditions. Widespread deep irrigation pumping may be drawing shallower, contaminated groundwater down to greater depths. These findings have severe implications on finding alternate drinking water sources, in West Bengal, and adjoining areas of Bangladesh, with plausible similar geological and hydrogeological framework.
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| 49. |
- Ngirane-Katashaya, G., et al.
(författare)
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Decision Support Systems for Water Resources Management in Uganda : The Need
- 2007
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Ingår i: Sustainable Development of Water Resources, Water Supply and Environmental Sanitation. - 9781843801191 ; , s. 267-270
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Konferensbidrag (refereegranskat)abstract
- Water is a major factor in the socio-economic fabric of Ugandan society and a major determinant of the development potential of the country. However, management of water resources is a complex problem that typically involves a variety of stakeholder interests and environmental uncertainties. The plurality of concerns establishes a pressing need for improved planning and management capabilities, and in this respect it has been noted that decision-making related to water resource management would benefit from engineering expertise combined with suitable use of informatics. In spite of rapidly advancing computer technology and the proliferation of software for decision support, relatively few Decision Support Systems have been developed, implemented, and evaluated in the field of water resources management in Uganda. Such tools need to be structured to fit in with existing policy frameworks in Uganda?s water sector, and should be tailored to the local conditions prevailing in the country.
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| 50. |
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