https://www.ajol.info/index.php/wsa/issue/feed Water SA 2021-03-10T07:53:27+00:00 Water SA Editor watersa@wrc.org.za Open Journal Systems <p>This journal publishes refereed, original work in all branches of water science, technology, engineering and policy. This includes: water resource development; the hydrological cycle; surface hydrology; geohydrology, hydropedology and hydrometeorology; limnology; freshwater and estuarine ecology; salinisation; treatment and management of municipal and industrial water and wastewater; treatment and disposal of sewage sludge; environmental pollution control; environmental and drinking water quality; drinking water treatment; water services, including domestic water supply and sanitation services; agricultural water; aquaculture in terms of its impact on the water resource; water policy and governance; water economics; water as a social good. <em>Water SA</em> is intended to serve both international and Southern African readers and authors. Contributions which are not of broad international interest must make a specific contribution to Southern Africa (defined for this purpose to include the countries of South Africa, Swaziland, Lesotho, Namibia, Botswana, Zimbabwe and Mozambique). Submissions of predominantly local interest outside of Southern Africa will not be considered.</p><p> </p><p>Contributions may take the form of a paper, a critical review, a short communication, a rapid communication, a technical note or comments on papers already published. A <strong>paper </strong>is a comprehensive contribution to the subject, including introduction, experimental information and discussion of results. (Technical accounts involving application of well-known techniques, and situation assessment/observation/sampling papers reporting results of work not carried out as a research activity, cannot be considered.) A <strong>review </strong>is an authoritative, critical account of recent and current research in a specific field to which the author has made notable contributions. A <strong>short communication </strong>is a concise account of new and significant findings to inform readers of preliminary or limited research results. A <strong>rapid communication </strong>is an original contribution which merits prompt publication to publicise the findings of very recent research with immediate significance. A <strong>technical note </strong>describes an original process or technique without necessarily including extensive data, theory or critical evaluation. <strong>Comments </strong>on papers already published are sent to the authors of the paper for reply and both the comments and the authors’ reply will be published in the upcoming issue of <em>Water SA</em>. Preference is given to concise contributions.</p><p style="line-height: 140%; background: white;">Other websites related to this journal: <span style="line-height: 140%; font-family: Arial; color: #111111; font-size: 9.5pt;"><a href="http://www.wrc.org.za/" target="_blank"><span style="color: #337755;">http://www.wrc.org.za </span></a></span></p><p style="line-height: 140%; background: white;"><em><span style="line-height: 140%; font-family: Arial; color: #111111; font-size: 9.5pt;">WaterSA</span></em><span style="line-height: 140%; font-family: Arial; color: #111111; font-size: 9.5pt;"> is also available electronically through SABINET Online <a title="http://reference.sabinet.co.za/sa_epublication/waters" href="http://reference.sabinet.co.za/sa_epublication/waters" target="_blank">http://reference.sabinet.co.za/sa_epublication/waters</a></span></p> https://www.ajol.info/index.php/wsa/article/view/204516 Intermittent water supply: a South African perspective 2021-03-10T07:46:31+00:00 Carlo Loubser carloloubser@sun.ac.za Bubala Mwiinga Chimbanga carloloubser@sun.ac.za Heinz Jacobs carloloubser@sun.ac.za <p>The prevalence of intermittent water supply in South Africa was investigated in this research study. Data on intermittent water supply in South Africa was collated by considering the following four sources: a targeted water services provider survey; published databases and related reports; open-access publications, such as online media articles; and field visits by the project team to selected areas. The data were spatially and temporally analysed to determine the prevalence of intermittent water supply. The population affected by intermittent water supply increased by ∼26% between 2008 and 2017, which exceeds the population increase of ∼12% over the same period. Moreover, 22 million people in South Africa were affected by intermittent water supply in 2017. Results from this study confirm an increased prevalence of intermittent water supply over time and show that 65 of the 231 municipalities in South Africa supplied water intermittently, 32 had continuous water supply and 134 had no data. Fundamentally, the outcomes highlight the widespread occurrence of intermittent water supply in South Africa, which is in line with the poor state of water services delivery in South Africa, as portrayed in the 2018 National Water and Sanitation Master Plan by the national Department of Water and Sanitation.</p> 2021-03-08T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204520 A review of trends in scientific coverage of water governance in South Africa and what this means for agenda-setting of public investment in water governance R&D 2021-03-10T07:47:01+00:00 Inga Jacobs-Mata i.jacobs-mata@cgiar.org Patience Mukuyu i.jacobs-mata@cgiar.org John Dini i.jacobs-mata@cgiar.org <p>A review of global trends in water governance reveals a paradigm dominated by political and institutional change which becomes increasingly aligned with global shifts towards sustainability and also a rapid decline in the hydraulic mission. Closely aligned to these trends, but distinct in its own trajectory, South Africa’s water governance dynamics have evolved through a period of considerable socio-political change marked by inequitable resource allocation and water scarcity. This paper presents the results of a review of water governance research and development (R&amp;D) trends in South Africa, aimed at informing the national funding agency – the Water Research Commission (WRC) – in its agenda-setting process for future water governance research. Through a bibliometric analysis, a data-mining exercise, and stakeholder consultations, this paper distils four key areas of focus for the future of water governance research in South Africa: (i) that future water governance research needs to be more needs-based, solution-oriented and embedded within real-life contexts; (ii) the need for a paradigm shift in water governance research to a constructive, adaptive and rapid response research agenda in an environment of increasing change and uncertainty; (iii) the need for the enabling environment to be strengthened, including acknowledgement of the role of individuals as agents of change, and the role of WRC in establishing a community of practice for water governance experts that can respond to issues with agility; and (iv) a consolidation of fragmented project-based knowledge to a programmatic approach that builds the pipeline of expertise in the water governance R&amp;D domain.</p> 2021-03-08T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204523 Economic valuation of the averted degradation of the Vyeboom Wetland in the Theewaterskloof Dam catchment, South Africa 2021-03-10T07:48:51+00:00 Daniel Marais prevision@mweb.co.za Theo Fischer prevision@mweb.co.za Donovan Kotze prevision@mweb.co.za Bennie Haasbroek prevision@mweb.co.za Malin Govender prevision@mweb.co.za James Pugin prevision@mweb.co.za Annabel Horn prevision@mweb.co.za <p>Wetlands within the catchments of water supply dams have potential to make important contributions to water-related ecosystem services, particularly water quality enhancement. Wetlands are facing growing threats and continuing degradation. There have been limited attempts at evaluating the contribution of South African wetlands, and their rehabilitation, for water quality enhancement and other water-related ecosystem services. A comprehensive and integrated wetland services economic assessment determined the value of the Vyeboom Wetland in the catchment of the Theewaterskloof Dam. The water of this dam is a significant contributor to the City of Cape Town’s water supply. The economic valuation model integrates hydrological, catchment status and economic models, with a long-term (80-year monthly) wetland water balance from a calibrated hydrological model as a driver for the nutrient removal aspect. The economic valuation builds on a water quality enhancement model, based on the minimisation of indirect use replacement cost principle, supplemented by a sediment retention and carbon storage assessment. The capability of the economic valuation model is illustrated by assessing the rehabilitation of a 25-ha area in the Vyeboom Wetland, which is currently intact, but is under threat of being severely degraded by the advancing erosion headcut. It was assumed that the current state of the Vyeboom Wetland is almost pristine (only 1 ha degraded), but that a further 24 ha would degrade over a period of 50 years, following spatial changes over time. By balancing the total investment in offsetting the potential loss in benefits, it is evident that an amount of 2.5 million ZAR could be afforded for rehabilitation. If, instead of a logistic degradation profile, the wetland is assumed to already be in a state of accelerated deterioration, the rehabilitation project budget for Vyeboom Wetland will increase once the other intrinsic benefits described are considered in the analysis.</p> 2021-03-08T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204525 The influence of a high-density sludge acid mine drainage (AMD) chemical treatment plant on water quality along the Blesbokspruit Wetland, South Africa 2021-03-10T07:49:23+00:00 Mauro Lourenco mauro95cesar@gmail.com Chris Curtis mauro95cesar@gmail.com <p>The Eastern Basin chemical acid mine drainage (AMD) treatment plant is one of the world’s largest high-density sludge (HDS) plants, and came into operation in August 2016. The plant is situated near the inoperative Grootvlei Mine in Springs, South Africa, and upstream of the Blesbokspruit Wetland, a former Ramsar Wetland of International Importance, now on the Montreux Record. Since being in operation it has had a major influence on surface water quality along the wetland area. The plant was constructed to mitigate the anticipated decant of AMD water from the abandoned Grootvlei Mine into the Blesbokspruit Wetland. Making use of the BACI (Before-After-Control-Impact) design, this study compares surface water quality of the Blesbokspruit upstream (control site) and downstream (impact site) of the treatment plant for 3-year periods before and after it came into operation. Quarterly water quality data (aluminium, ammonia, chloride, conductivity, dissolved oxygen, fluoride, iron, magnesium, manganese, nitrate, pH, phosphate, sodium and sulphate) from 2013–2019 were used for 5 historical Rand Water monitoring sites along the Blesbokspruit. The current HDS treatment process has negatively influenced conductivity, chloride, magnesium, sodium and sulphate levels downstream. Since the commissioning of the treatment plant, the levels of these parameters have increased significantly.&nbsp; Notably, conductivity and sulphate have reached the management range defined as ‘unacceptable’ within the framework set out by the Blesbokspruit Forum (which is less stringent than the national guidelines for aquatic ecosystems), with potential impacts on salinization of the Vaal Barrage downstream. However, the significant reduction of iron, ammonia and phosphate concentrations downstream of the plant may be a combined beneficial effect of dilution by increased discharge from the plant and the wetland removing these contaminants. These results highlight the need for further research into possible secondary treatment and desalinisation mechanisms and the potential ecological and downstream water supply implications of increasing salinity within the area.</p> 2021-03-08T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204526 River water quality management using a fuzzy optimization model and the NSFWQI Index 2021-03-10T07:49:42+00:00 Mohammad Kazem Ghorbani hamidifar@shirazu.ac.ir Abbas Afshar hamidifar@shirazu.ac.ir Hossein Hamidifar hamidifar@shirazu.ac.ir <p>In this study, a novel multiple-pollutant waste load allocation (WLA) model for a river system is presented based on the National Sanitation Foundation Water Quality Index (NSFWQI). This study aims to determine the value of the quality index as the objective function integrated into the fuzzy set theory so that it could decrease the uncertainties associated with water quality goals as well as specify the river's water quality status rapidly. The simulation-optimization (S-O) approach is used for solving the proposed model. The QUAL2K model is used for simulating water quality in different parts of the river system and ant colony optimization (ACO) algorithm is applied as an optimizer of the model. The model performance was examined on a hypothetical river system with a length of 30 km and 17 checkpoints. The results show that for a given number of both the simulator model runs and the artificial ants, the maximum objective function will be obtained when the regulatory parameter of the ACO algorithm (i.e., <em>q</em><sub>0</sub>) is considered equal to 0.6 and 0.7 (instead of 0.8 and 0.9). Also, the results do not depend on the exponent of the membership function (i.e., <em>γ</em>). Furthermore, the proposed methodology can find optimum solutions in a shorter time.</p> 2021-03-08T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204527 Poly- and perfluorinated substances in environmental water from the Hartbeespoort and Roodeplaat Dams, South Africa 2021-03-10T07:50:12+00:00 B. Batayi OkonkwoOJ@tut.ac.za O.J. Okonkwo OkonkwoOJ@tut.ac.za A.P. Daso OkonkwoOJ@tut.ac.za <p>Concentrations of poly- and perfluorinated substances (PFASs) were determined in Hartbeespoort and Roodeplaat Dams, South Africa. Water samples were collected from the dams in February–March, and May–June, representing southern hemisphere summer and winter seasons, respectively. Solid phase extraction (SPE) was used to extract the analytes from the water samples and liquid chromatography-tandem mass spectrometry (LC-MS/MS) used for analysis. The mean PFAS concentrations detected ranged from 1.38–346.32 ng∙L<sup>-1</sup> and 2.31–262.29 ng∙L<sup>-1</sup> in the Hartbeespoort Dam and Roodeplaat Dam, respectively. Perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS) and perfluoroheptanoic acid (PFHpA) were the most dominant PFASs detected. The PFAS concentrations detected were higher in summer than in winter, but the difference between seasons was not statistically significant (<em>p </em>= 1). Furthermore, the concentrations of short-chain PFASs were higher than the longer chains. Overall, the PFAS concentrations in the present study are comparable to those reported in other parts of South Africa, and also Ghana, higher than the concentrations reported in Uganda, Singapore, and Vietnam, and lower than those in Germany, Japan and China. The measured concentrations of PFOA and PFOS raise concerns of human exposure to these chemicals since they are above the USEPA advisory limit. This suggests that communities living within the vicinity of the dams are most likely to be exposed to these chemicals.</p> 2021-03-08T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204539 Modelling potential climate change impacts on sediment yield in the Tsitsa River catchment, South Africa 2021-03-10T07:50:22+00:00 Simone Norah Theron PretoriusS@arc.agric.za Harold Louw Weepener PretoriusS@arc.agric.za Jacobus Johannes Le Roux PretoriusS@arc.agric.za Christina Johanna Engelbrecht PretoriusS@arc.agric.za <p>The effects of climate change on water resources could be numerous and widespread, affecting water quality and water security across the globe. Variations in rainfall erosivity and temporal patterns, along with changes in biomass and land use, are some of the impacts climate change is projected to have on soil erosion. Sedimentation of watercourses and reservoirs, especially in water-stressed regions such as sub-Saharan Africa, may hamper climate change resilience. Modelling sediment yield under various climate change scenarios is vital to develop mitigation strategies which offset the negative effects of erosion and ensure infrastructure remains sustainable under future climate change. This study investigated the relative change in sediment yield with projected climate change using the Soil and Water Assessment Tool (SWAT) for a rural catchment in South Africa for the period 2015–2100. Data from six downscaled Coupled Global Climate Models (CGCM) were divided into three shorter time periods, namely, 2015–2034, 2045–2064 and 2081–2100. Results were then compared with a control scenario using observed data for the period 2002–2017. The results show that, if left unmanaged, climate change will likely lead to greater sediment yield, of up to 10% more per annum. Peak sediment yield will also increase almost three-fold throughout the century. The study shows that projected climate change will have multiple negative effects on soil erosion and emphasised the need for changes in climate to be considered when embarking on water resource developments.</p> 2021-03-08T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204547 Spatial and temporal analysis of the mid-summer dry spells for the summer rainfall region of South Africa 2021-03-10T07:53:13+00:00 M.G. Mengistu Michael.Mengistu@weathersa.co.za C. Olivier Michael.Mengistu@weathersa.co.za J.O. Botai Michael.Mengistu@weathersa.co.za A.M. Adeola Michael.Mengistu@weathersa.co.za S. Daniel Michael.Mengistu@weathersa.co.za <p>South Africa is frequently subjected to severe droughts and dry spells during the rainy season. As such, rainfall is one of the most significant factors limiting dryland crop production in South Africa. The mid-summer period is particularly important for agriculture since a lack of rain during this period negatively affects crop yields. Dry spell frequency analyses are used to investigate the impacts of sub-seasonal rainfall variability on crop yield, since seasonal rainfall totals alone do not explain the relationship between rainfall and crop yields. This study investigated the spatial and temporal occurrences of the mid-summer dry spells based on magnitude, length and time of occurrence in the major maize growing areas of the summer rainfall region of South Africa. Three thresholds of 5 mm, 10 mm, and 15 mm total rainfall for a pentad were used for the analysis of dry spells. &nbsp;Dry spell analysis showed that dry pentads occur during mid-summer with differing intensity, duration and frequency across the summer rainfall region. Annual frequency of dry pentads for the mid-summer period ranged between 0 and 4 pentads for the 5 mm threshold and 1 to 7 for the 10 mm and 15 mm thresholds. &nbsp;The non-parametric Mann-Kendall trend analysis of the dry pentads indicates that there is no significant trend in the frequency of dry spells at a 95% confidence level. The initial and conditional probabilities of getting a dry spell using the Markov chain model also showed that there is a 32% to 80% probability that a single pentad will be dry using the 15 mm threshold. There is a 5% to 48% probability of experiencing two consecutive dry pentads and 1% to 29% probability of getting three consecutive dry pentads. The duration and intensity of dry spells, as well as the Markov chain probabilities, showed a decrease in dry spells from west to east of the maize-growing areas of the summer rainfall region of South Africa.</p> 2021-03-09T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204548 Field calibration of DFM capacitance probes for continuous soil moisture monitoring 2021-03-10T07:53:15+00:00 L. Myeni lindomyeni@gmail.com M.E. Moeletsi lindomyeni@gmail.com A.D. Clulow lindomyeni@gmail.com <p>This study was undertaken to derive textural and lumped site-specific calibration equations for Dirk Friedhelm Mercker (DFM) capacitance probes and evaluate the accuracy levels of the developed calibration equations for continuous soil moisture monitoring in three selected soil types. At each site, 9 probes (3 per plot) were installed in 2 m<sup>2 </sup>plots, for continuous soil moisture measurements at 5 different depths (viz. 10, 20, 30, 40 and 60 cm) under dry, moist and wet field conditions. Textural site-specific calibration equations were derived by grouping the same soil textural classes of each site regardless of soil depth, while lumped site-specific calibration equations were derived by grouping all datasets from each site, regardless of soil depth and textural classes. Sensor readings were plotted against gravimetrically measured volumetric soil moisture (<em>θ<sub>v</sub></em>) for different textural classes as a reference. The coefficient of determination (<em>r<sup>2</sup></em>) was used to select the best fit of the regression function. The developed calibration equations were evaluated using an independent dataset. The results indicated that all developed textural and lumped site-specific calibration equations were linear functions, with <em>r<sup>2</sup></em> values ranging from 0.96 to 0.99. Relationships between the measured and estimated <em>θ<sub>v</sub></em> from calibration equations were reasonable at all sites, with <em>r<sup>2</sup></em> values greater than 0.91 and root mean square error (RMSE) values ranging from 0.010 to 0.020 m<sup>3</sup>∙m<sup>-3</sup>. The results also indicated that textural site-specific calibration equations (RMSE &lt; 0.018 m<sup>3</sup>∙m<sup>-3</sup>) should be given preference over lumped site-specific calibrations (RMSE &lt; 0.020 m<sup>3</sup>∙m<sup>-3</sup>) to attain more accurate <em>θ<sub>v</sub></em> measurements. The findings of this study suggest that once DFM capacitance probes are calibrated per site, they can be reliably used for accurate in-situ soil moisture measurements. The developed calibration equations can be applied with caution in other sites with similar soil types to attained reliable in-situ soil moisture measurements.</p> 2021-03-09T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204549 Relationships between agronomic and environmental phosphorus analyses of selected soils 2021-03-10T07:53:17+00:00 M.M. Nthejane vanhuyssteencw@ufs.ac.za C.C. du Preez vanhuyssteencw@ufs.ac.za C.W. van Huyssteen vanhuyssteencw@ufs.ac.za <p>Phosphorus (P) is an essential nutrient in crop production and is therefore typically applied as phosphatic fertilisers.&nbsp; This can induce soil P concentrations that may contribute to freshwater eutrophication.&nbsp; Soil P tests developed from a water pollution protection perspective are unlike those developed for agronomic purposes and are also not easily adapted to routine analyses.&nbsp; The aim with this study was therefore to establish whether the values of P extracted from a range of soils by various agronomic and environmental P determination methods are related or not.&nbsp; Topsoil samples were collected from virgin soils in central South Africa and treated with KH<sub>2</sub>PO<sub>4</sub> to induce different P concentrations and then incubated for 3 months, while subjected to various wetting and drying cycles.&nbsp; The samples were then analysed for P using the extractants of Bray 1, citric acid, ISFEI, Olsen, and Truog, commonly employed to establish the agronomic P status of soils.&nbsp; Environmental P status was determined with calcium chloride (CaCl<sub>2</sub>) and ammonium oxalate (DPS<sub>ox</sub>) extractants.&nbsp; Generally good relationships were found between CaCl<sub>2</sub> and ISFEI (<em>R</em><sup>2</sup> = 0.72), between DPS<sub>ox</sub> and Truog (<em>R</em><sup>2</sup> = 0.79), and between DPS<sub>ox</sub> and citric acid (<em>R</em><sup>2</sup> = 0.82).&nbsp; Agronomic P soil tests therefore have the potential to be used in regulating application of phosphatic fertilisers to ensure optimum crop yields, while simultaneously limiting freshwater pollution.&nbsp; Further field studies are, however, recommended to determine threshold values from an environmental point of view.</p> 2021-03-09T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204551 The impact of sludge return liquors on South African wastewater treatment plants 2021-03-10T07:53:19+00:00 Olivier Nsengiyuma david.ikumi@uct.ac.za Yuva Coothen david.ikumi@uct.ac.za David Ikumi david.ikumi@uct.ac.za Kirshen Naidoo david.ikumi@uct.ac.za <p>There have been three considerable shifts, in the past 20 years, in the conventional design and modelling of wastewater treatment plants (WWTPs): (i) single unit process to plant-wide modelling, (ii) consideration of WWTPs as water and resource recovery facilities (WRRFs), and (iii) the need to simplify WWTP models to allow their intake by new stakeholders (i.e. plant operators, designers and decision-makers) who use these models for evaluation of WWTP optimisation strategies. The latter shift has prompted the debate about model complexity versus the required modelling purpose among modellers. In addition to the aforementioned shifts, there has been limited research on the impact of sludge recycling dewatering liquor on the overall plant performance, especially in the context of South African WWTPs. A simplified full-scale steady-state WWTP simulation tool was developed, based on principles of sound mass-balance stoichiometry and rate-limiting kinetics. This tool enables the user to analyse the impact of recycling the DWL on the plant performance through different scenarios. The strategic scenarios evaluated included the implementation of two side-stream treatment processes (STPs), namely BABE and struvite precipitation. The evaluation of various strategies was done using the benchmark simulation model (BSM) task group plant performance indices (i.e. effluent quality and operational cost indices, EQI and OCI, respectively) incorporated into the simplified steady-state full-scale models. The integration of STP in the WWTP layout results in better EQI and OCI. The composition of the DWL affects the choice of the STP to be used, i.e., for DWL from an AD treating WAS that is not P-rich the recommended side-stream treatment operation would be the BABE process rather than struvite precipitation.</p> 2021-03-09T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204552 Effect of reactor characteristics on the seasonal effectiveness of solar disinfection: a factorial study 2021-03-10T07:53:22+00:00 Ekene Jude Nwankwo ekene.nwankwo@unn.edu.ng Jonah Chukwuemeka Agunwamba ekene.nwankwo@unn.edu.ng <p>Solar disinfection (SODIS) involves exposing water stored in transparent polyethylene terephthalate (PET) containers to the sun for about 6 h of strong sunlight, after which the water is rendered safe for consumption. This study investigated the seasonal effect of reactor characteristics on the inactivation kinetics/constant of faecal coliforms by conducting a 2<sup>3</sup> factorial experiment, involving two levels of PET bottle size, PET bottle thickness, and PET bottle rear surface, uniquely combined to form 8 SODIS reactors/experimental units. The faecal coliform population of hourly samples taken from the 8 SODIS reactors showed that the inactivation kinetics/constant depends on the irradiation energy and maximum water temperature as dictated by the reactor characteristics. The average rate constant of the reflective reactors (1.37 ± 0.43 h<sup>-1</sup>) was significantly better (<em>p</em> &lt; 0.001) than the absorptive reactors (1.17 ± 0.59 h<sup>-1</sup>) between June and October. The average rate constant of the small PET bottles (1.73 ± 0.65 h<sup>-1</sup>) is significantly higher (<em>p</em> &lt; 0.002) than the large PET bottles (1.46 ± 0.51 h<sup>-1</sup>) from December to May; while the average rate constant of the light PET bottles (1.58 ± 0.64 h<sup>-1</sup>) is significantly better (<em>p</em> &lt; 0.001) than the thick PET bottles (1.41 ± 0.52 h<sup>-1</sup>) year-round. Analyses of results confirmed a two-way interaction effect between PET bottle size and PET bottle thickness and between PET bottle rear surface and PET bottle thickness for periods with average radiation intensity of&nbsp; 450–500 W∙m<sup>−2</sup>. Although container size and thickness were the most significant factors, combining light PET bottles with absorptive rear-surface could extend the applicability of SODIS to regions that fall short of the recommended radiation intensity threshold of 500 W∙m<sup>−2</sup> for 5 h.</p> 2021-03-09T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204553 Relationship between water quality and physical conditions of domestic storage tanks supplied by a water utility in a rapidly growing city 2021-03-10T07:53:25+00:00 E.W. Makoko enoch.makoko@nwsc.co.ug E. Wozei enoch.makoko@nwsc.co.ug L. Birungi enoch.makoko@nwsc.co.ug <p>Domestic water storage tanks are commonly used in urban centres of developing countries such as Uganda to enable reliable access to water. However, little work has been done on the conditions of domestic water storage tanks since it is assumed that water received meets the required standards and guidelines for drinking water. In 2015, over 80% of the water quality complaints raised by water utility customers in Kampala were about water from storage tanks. In this study we assessed water quality in, and conditions of, domestic storage tanks, for customers supplied by a water utility from March–August 2017 in Kampala, Uganda. Longitudinal assessment of 372 storage tanks in 6 sampled wards involved a minimum of 6 samples collected from each site in both wet and dry months of 2017. A set of guiding questions was used to establish tank conditions, with a ‘yes’ or ‘no’ response and a range of ‘low’ to ‘critical’ risk ratings. The study showed that there were three main types of storage tanks: plastic (88%), concrete (7%), and metal (5%). Of these tanks, 84% were elevated, 41% were less than 5 years old, 69% were not cleaned annually, and 88% were covered. There was a statistically significant relationship (<em>p</em> &lt; 0.05) between tank physical conditions and quality of stored water. Wards with unplanned and industrial settlements had the highest number of tanks with contaminated water. The study therefore revealed that the physical conditions and management of domestic water storage tanks have an effect on water quality. This is important information for a water utility as it means that it is not enough to supply safe water if the quality may deteriorate upon storage at the consumer premises. A routine inspection checklist and consumer guidelines for domestic storage tank management are proposed.</p> 2021-03-09T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/wsa/article/view/204555 Water quality assessment using a portable UV optical absorbance nitrate sensor with a scintillator and smartphone camera 2021-03-10T07:53:27+00:00 J.M.D.F.P. Ingles mjbooysen@sun.ac.za T.M. Louw mjbooysen@sun.ac.za M.J. Booysen mjbooysen@sun.ac.za <p>Nitrate contamination of water sources is a global environmental concern. A major source of pollution is agricultural runoff, which can contain decomposed organic matter, fertilizer, and animal or human waste. Nitrate adversely affects the stability of water systems such as dams and rivers and thus also public health. Regulation is essential but difficult to implement, given that measuring nitrates is laborious, and normally done using chemical assays in laboratories. We present a novel portable nitrate sensor that uses a smartphone camera fitted with low-cost optics. The sensor uses ultraviolet absorbance analysis to detect nitrates in water samples and quantify the concentration. The sensor’s absorptivity when a bandpass filter was used was 0<em>.</em>0681 L∙mg<sup>−1</sup>∙cm<sup>−1</sup> compared to 0<em>.</em>0934 L∙mg<sup>−1</sup>∙cm<sup>−1 </sup>measured with a spectrophotometer in a laboratory. Measurements by the sensor of the concentration of nitrates in two environmental samples differed from those taken by the spectrophotometer by 19% and 7%. The sensor achieved a nitrate concentration measurement resolution of 0<em>.</em>2 mg∙L<sup>−1</sup>, and a detection range of 0–5 mg∙L<sup>−1</sup>, with higher concentrations requiring dilution to quantify. Our tests showed that the smartphone-based nitrate sensor is sufficiently accurate to be used as an inexpensive instrument for nitrate analysis in the field.</p> 2021-03-09T00:00:00+00:00 Copyright (c)