Scielo RSS <![CDATA[Water SA]]> vol. 42 num. 3 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>DRIFT-ARID: A method for assessing environmental water requirements (EWRs) for non-perennial rivers</b>]]> Environmental water requirement (EWR) assessment methods, for ascertaining how much water should be retained in rivers to sustain ecological functioning and desired levels of biodiversity, have mostly been developed for perennial rivers. Despite non-perennial rivers comprising about 30-50% of the world's freshwater systems, data on their hydrology, biota and ecological functioning are sparse. Current EWR assessments require hydrological and other data that may not be available for such rivers and some adaptation in the methods used seems necessary. DRIFT is an EWR method for perennial (or near-perennial) rivers that has been developed in South Africa over the past two decades and is now widely applied nationally and internationally. When applied to the semi-permanent Mokolo River, challenges particular to, or accentuated by, non-perennial rivers included the reliable simulation of hydrological data, the extent of acceptable extrapolation of data, difficulties in predicting surface-water connectivity along the river, and the location and resilience of pools, as well as whether it was possible to identify a reference (natural) condition. DRIFT-ARID, reported on here, is an adaptation of the DRIFT approach to begin addressing these and other issues. It consists of 11 phases containing 9 activities. <![CDATA[<b>DRIFT-ARID: Application of a method for environmental water requirements (EWRs) in a non-perennial river (Mokolo River) in South Africa</b>]]> Methods developed to determine the amount of water required (EWR) to sustain ecosystem services in non-perennial rivers need a different approach to those used in perennial rivers. Current EWR methods were mostly developed for use in perennial rivers. Non-perennial rivers differ from perennial ones in terms of variability in flow, periods of no-flow and related habitat availability. A DRIFT-ARID method (an adaptation of the Downstream Response to Imposed Flow Transformation (DRIFT) method) was developed, tested and adjusted, using the semi-permanent Mokolo River. Field data from five study sites was collected from April to May 2010 by a multidisciplinary team. The results were used in a DRIFT-ARID Decision Support System (DSS) to determine the impact of five chosen development scenarios in the Mokolo River Catchment. An integrated groundwater-surface water MIKE-SHE hydrological model was used to simulate the hydrology of the chosen scenarios. Specific non-perennial river indicators such as onset of dry phase were identified and included in the DRIFT-ARID DSS. DRIFT-ARID has the potential to be used in non-perennial rivers and, once set up, can provide results for future scenarios. The method now needs to be tested on other non-perennial river types, especially episodic rivers where data are scarce or non-existent. <![CDATA[<b>MIKE-SHE integrated groundwater and surface water model used to simulate scenario hydrology for input to DRIFT-ARID: The Mokolo River case study</b>]]> A fully integrated, physically-based MIKE SHE/MIKE11 model was developed for the Mokolo River basin flow system to simulate key hydraulic and hydrologic indicator inputs to the Downstream Response to Imposed Flow Transformation for Arid Rivers (DRIFT-ARID) decision support system (DSS). The DRIFT-ARID tool is used in this study to define environmental water requirements (EWR) for non-perennial river flow systems in South Africa to facilitate ecosystem-based management of water resources as required by the National Water Act (Act No. 36 of 1998). Fifty years of distributed daily climate data (1950 to 2000) were used to calibrate the model against decades of daily discharge data at various gauges, measurements of Mokolo Dam stage levels, and one-time groundwater level measurements at hundreds of wells throughout the basin. Though the calibrated model captures much of the seasonal and post-event stream discharge response characteristics, lack of sub-daily climate and stream discharge data limits the ability to calibrate the model to event-level system response (i.e. peak flows). In addition, lack of basic subsurface hydrogeologic characterisation and transient groundwater level data limits the ability to calibrate the groundwater flow model, and therefore baseflow response, to a high level. Despite these limitations, the calibrated model was used to simulate changes in hydrologic and hydraulic indicators at five study sites within the basin for five 50-year land-use change scenarios, including a present-day (with dam), natural conditions (no development/irrigation), and conversion of present-day irrigation to game farm, mine/city expansion, and a combination of the last two. Challenges and recommendations for simulating the range of non-perennial systems are presented. <![CDATA[<b>Abiotic water quality control on mangrove distribution in estuarine river channels assessed by a novel boat-mounted electromagnetic-induction technique</b>]]> Due to climate change impacts and the resulting sea-level rise, saline waters have been found further inland in tropical riverine estuaries such as the Godineau wetland, Trinidad. The saline water intrusion could constrain mangrove vegetation distribution. We investigated the surface water quality of two river channels (2 km and 6 km), emanating from a tropical wetland and from forest/agriculture at high-tide, respectively. Using a novel boat-mounted geophysical approach, spatially exhaustive river/estuarine salinity data was collected. Water quality parameters - salinity, pH and dissolved oxygen (DO) - were compared with vegetation surveyed along the course of the rivers to determine relationships between plant zonation and water quality. Our findings showed similar trends for salinity and apparent electrical conductivity, which were higher in the 2 km channel (27.10 to 31.80 dS/m) than in the 6 km channel (17.80 to 27.10 dS/m), while pH and DO levels were lower in the 2 km channel than in the 6 km channel due to higher levels of decomposition in the stagnant shorter channel. Red mangrove (Rhizophora mangle) was found in areas with little oxygen, high salinities and high acidity, making it more adaptable to conditions resulting from saline intrusion. Therefore, to replace the mangrove that has been lost due to die-off, the red mangrove maybe used in viable restoration efforts for the protection of inland areas from floods, as well as to provide ecosystem goods and services. <![CDATA[<b>A colorimetric probe for the detection of Ni<sup>2+</sup> in water based on Ag-Cu alloy nanoparticles hosted in electrospun nanofibres</b>]]> A Ni²+ based colorimetric probe based on glutathione-stabilized silver/copper nanoparticles (GSH-Ag-Cu alloy NPs) in an electrospun polymer matrix is reported. Glutathione-Ag-Cu alloy NPs were characterized by ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The freshly synthesized GSH-Ag-Cu alloy NPs in a polymer matrix were black in colour due to an intense surface plasmon absorption band at 424 nm. However the electrospun nanocomposite fibres were green in colour and in the presence of Ni²+ the green GSH-Ag-Cu alloy NP fibres were discoloured. The sensitivity of the GSH-Ag-Cu alloy NPs towards other representative transition, alkali and alkali earth metal ions was negligible. The effect of the concentration of Ni²+ on the nanocomposite fibres was evaluated and the 'eye-ball' limit of detection was found to be 5.8 μg/mL. <![CDATA[<b>Occurrence of cyanobacteria genera in the Vaal Dam: Implications for potable water production</b>]]> The occurrence of cyanobacteria genera in the Vaal Dam was analysed and the factors that influence its dominance in the particular reservoir were also investigated. The study was motivated by the effects of the secondary metabolites of cyanobacteria genera on potable water production. Cyanobacteria genera have been found to be potentially toxic and capable of producing taste and odour secondary metabolites such as geosmin. Historical data from the Department of Water and Sanitation on percentage composition of cyanobacteria genera in the Vaal Dam, were collected for the 2006, 2007, 2011 and 2012 years. The concentrations of NO2-N and NO3-N and total phosphorus as well as water temperature data were collected from the same sampling point for the study period. This data, together with weather data, was statistically analysed for trends and relatedness between variables. It was found that Microcystis and Anabaena were the dominant cyanobacteria genera in Vaal Dam and they were jointly dominant over other phytoplankton genera during February and March. It was also found that the dominance of cyanobacteria genera significantly correlated with air and water temperature and concentration of NO2-N and NO3-N. It was concluded that the dominance of Microcystis and Anabaena genera among the cyanobacteria genera has significant implications for potable water production as the genera are associated with taste and odour metabolites and toxins. It was recommended that depth profiling be employed in order to identify an abstraction depth in the multilevel intake of the reservoir with relatively low levels of cyanobacteria cells. This would assist in minimising taste and odour events in potable water production. <![CDATA[<b>An analysis of the challenges for groundwater governance during shale gas development in South Africa</b>]]> As a prelude to potential development of South Africa's shale gas resources, it is critical to develop and implement effective groundwater governance arrangements. Existing policies and plans were analysed to determine whether critical gaps or barriers exist that could potentially lead to impacts on groundwater systems. Ten high-priority governance challenges were identified: (a) defining relevant metrics for baseline groundwater quality and availability; (b) developing guidelines for shale gas resource licensing, exploration, drilling, extraction, production, and completion; (c) defining and enforcing compliance monitoring systems; (d) dealing punitively with non-compliant operators; (e) mitigating and managing risks to prevent impairment of groundwater resources; (f) implementing a goal-based regulatory framework; g) enforcing strict chemical disclosure requirements; (h) coordinating across government departments and regulatory bodies meaningfully and productively; (i) implementing a framework for subsidiarity and support to local water management; and (j) providing an incentive framework that supports strong groundwater management and environmental protection. To overcome these challenges, it is recommended that a decentralised, polycentric, bottom-up approach involving multiple institutions is developed to adaptively manage shale gas development. This transition from the current rigid regulatory structure can foster cooperation and collaboration among key stakeholders. The use of a pro-active groundwater governance structure that can accommodate current, near-term, and long-term shale gas development is important for ensuring that future energy development in South Africa incorporates the influence of other simultaneous stressors such as climate (e.g. drought), land-use changes, population growth, industry, and competing demands for water. <![CDATA[<b>An assessment of perceptions, sources and uses of water among six African communities in the North West Province of South Africa</b>]]> The aim of this study was to assess perceptions, sources and uses of water among African residents of six different impoverished communities in the North West Province (NWP) of South Africa. A sequential exploratory mixed-methods design was used. Twenty-five purposively selected community members took part in the qualitative phase of the study, and during the quantitative phase a sample of 1 000 participants was proportionately and systematically selected from the six communities. The qualitative results were used to develop a structured questionnaire to quantify and verify the initial findings. The quantitative findings revealed that the majority of participants (72.4%) regard their water quality as average, and believe that water should be conserved and used sparingly (97.2%) and be provided free of charge (90.5%). Results also revealed that residents mostly obtain their water from local government (municipal) sources (76.5%), and that they mostly use water for drinking (98%), cooking (98.8%), flushing toilets (95.9%), washing themselves (bathing) (98.4%), their hands (99%), clothes (99.1%), and personal property (99.3%), as well as to water their gardens and domestic plants (93.2%). Finally, it was found that most people (83%) store their water in a fridge inside their homes. The results of the study have direct practical implications for water management and for the development and implementation of water-related interventions and projects in the NWP. <![CDATA[<b>Catalytic wet peroxide oxidation of formic acid in wastewater with naturally-occurring iron ore</b>]]> The catalytic wet oxidation of formic acid, using hydrogen peroxide as the oxidizing agent over naturally-occurring iron ore, was explored. Firstly, the decomposition of hydrogen peroxide to its hydroxyl radicals (HO- and HOO-) over naturally-occurring iron ore was investigated. The reaction was monitored by ATR FTIR by following the disappearance of the O-H peak of H2O2 at 2 860 cm-1. Decomposition occurred according to the Fenton mechanism and resulted in observed first-order rate constants one order of magnitude faster than that without the catalyst. Turnover frequencies (TOF) of 1.97-8.85 x 10-9 s-1 were obtained for the decomposition of H2O2. The wet oxidation of formic acid using hydrogen peroxide as the oxidizing agent over naturally-occurring iron ore reaction was also monitored by ATR FTIR, following the disappearance of the carbonyl stretching frequency of formic acid at 1 727 cm-1. Experiments were performed at different hydrogen peroxide (2, 4, 6 and 8M) and formic acid (1.26, 2.52, 6.3 and 12.6 M) concentrations as well as with varying amounts of naturally-occurring iron ore catalyst, at pH = 2. Elevated hydrogen peroxide and formic acid concentrations led to increased observed first-order kinetics, as high as k obs= 21.75 x 10(4) min¹ with a TOF = 1.73 x 10-8 - 1.12 x 10-6 s-1. <![CDATA[<b>Monetary value of the impacts of filamentous green algae on commercial agriculture: Results from two geographically different case studies</b>]]> This paper presents estimates of the monetary value of the impact of eutrophication (algae) on commercial agriculture in two different catchments in South Africa. A production function approach is applied to estimate the monetary value of the impact of filamentous green algae on commercial agriculture in the Dwars River, Western Cape and the Loskop irrigation area, Groblersdal, in South Africa. The main emphasis was on the impacts of algal growth on farm profitability, which relied on detailed information on the impact, and the extent of the impact, of algae on farming practice. The paper presents the study areas, methodological approach, surveyed pollution impacts and the calculated monetary value of the impacts of such pollution. A short conclusion discusses some potential applications of the results. Initial results point towards a value of R1 887 per hectare per year for the Dwars River area and R2 890 per hectare per year for the Loskop irrigation area. The information can not only be used to compare different eutrophication mitigation strategies within the study areas and, to a lesser extent, similar areas outside these areas, but can also inform a process focusing on assessing the market potential for tradable pollution permits as a mitigation practice to manage water pollution in both catchments. <![CDATA[<b>Water security in South Africa: Perceptions on public expectations and municipal obligations, governance and water re-use</b>]]> South Africa is a water-scarce country with increasing pressure on its water resources. Urgent interventions are needed to protect water security within this rapidly developing country. This paper reports on an interdisciplinary Water Security Colloquium, convened by the South African Young Academy of Science in 2014. A selected group of water professionals from academia, civil society and local government was brought together to discuss water security under three focus themes: 'public expectations and municipal obligations', 'water security and governance: challenges and advances', and 'water re-use: health and infrastructural considerations'. Participant perceptions were generated using a focus group methodology, combined with participatory data collection methods. Under each theme, inputs were categorised as 'challenges', 'gaps in knowledge', and 'solutions/recommendations' and these inputs were thereafter ranked in order of importance via a 'voting' process. Major challenges perceived included a lack of both skills and political will in government, a need to restore citizen trust in government intention and capability to deliver water-related services, and a failure to up-scale existing water re-use technology. Participants identified understanding of the process and implications of the Green and Blue Drop Programmes, knowledge transfer to the public, and the role of educators as major knowledge gaps. The top suggestions proposed included creating public awareness around and buy-in to initiatives to improve water security, accessible and user-friendly conversion of research results to implementation, and ensuring an active role for educators in creating awareness around water security. In view of the concerns identified, participants suggested as potential solutions: improving government and public understanding around water issues, incentivising water re-use and conservation, introducing rising block tariffs and improving human capacity development in the water sector. Developing the ecological infrastructure that protects both quantity and quality of water and building strong partnerships among all stakeholders were also recognised as key. <![CDATA[<b>Evaluation of an inverse distance weighting method for patching daily and dekadal rainfall over the Free State Province, South Africa</b>]]> Climate data recorded by national meteorological agencies is either incomplete or faulty for some periods due to a number of reasons. Multi-functional utilization of climate data in complete form necessitates the filling of these gaps. In this study an inverse distance weighting (IDW) method was used to estimate rainfall utilizing neighbouring station data in the Free State Province of South Africa. Six weather stations evenly distributed across the province, and with data for 1950 to 2008, were used to evaluate this patching IDW approach at daily and dekadal time steps. Coefficient of determination (r²), mean absolute error (MAE) and mean bias error (MBE) were the statistics used in the assessment. Firstly, the study conducted a sensitivity analysis of the IDW exponent (p) which showed that the best results are obtained when p is either 2 or 2.5. The estimated values at all six stations were highly correlated with the measured rainfall data with an overall r² value exceeding 0.70 for both daily and dekadal estimates. MAE showed low miscalculations with values with an average of 1 mm per day and 4.4 mm per dekad. MBE was very low for both daily and dekadal evaluations but the disaggregated data showed underestimation of the IDW mostly for daily rainfall exceeding 10 mm. Thus, IDW methodology proved to be an acceptable approach for estimating both daily and dekadal rainfall in the Free State Province. <![CDATA[<b>Evaluating sulphate removal and identifying the bacterial community present in acid mine drainage treated with synthetic domestic wastewater sludge</b>]]> Domestic wastewater sludge can serve as a carbon source in the passive biotic treatment of acid mine drainage (AMD) in microbial bioreactors to create anaerobic conditions for the removal of sulphate, chemical oxygen demand (COD) and pH neutralization. A synthetic medium simulating domestic wastewater sludge was used in AMD treatment in a ratio of 1:1 AMD: synthetic domestic wastewater sludge (SDWWS). Sulphate and COD removal were determined at different incubation temperatures and with and without a biofilm in the bioreactors. Sulphate and COD were removed by 60.8% and 96% within 26 d, after which a plateau was reached. Bacterial community analyses using next generation sequencing showed that Chlorobium spp. dominated at a relative percentage of 36% followed by Magnetospirillum spp. and Ornithobacterium spp. The effect of a resident biofilm in the bioreactors showed dominance of Chlorobium spp. at a relative percentage of 62% and removal of sulphates and COD at 96% and 58%, respectively, after 26 d. Incubation at 17-19°C reduced sulphates by only 10% and COD by 12% after 17 d, after which a plateau was reached. Magnetospirillum spp. was the dominate organism at the end of this trial. <![CDATA[<b>The use of exogenous microbial species to enhance the performance of a hybrid fixed-film bioreactor treating coal gasification wastewater to meet discharge requirements</b>]]> The objective of this study was to determine whether inoculating a hybrid fixed-film bioreactor with exogenous bacterial and diatoma species would increase the removal of chemical oxygen demand, nitrogenous compounds and suspended solids from a real-time coal gasification wastewater to meet environmental discharge requirements specified for petrochemical refineries. The COD removal increased by 25% (45% to 70%) at a relatively high inoculum dosage (370 gm-3) and unit treatment cost (12.21 €-m-3). The molar ratio of monovalent cations to divalent cations (M/D >2) affected nitrification, settling of solids and dewatering of the sludge. The use of a low-charge cationic flocculant decreased the suspended solids in the effluent by 70% (180 mg-L-1 to 54 mg-L-1) and increased the sludge dewatering rate by 88% (61 s-L-g-1 to 154 s-L-g-1) at a unit treatment cost of 2.5 €-t-1 dry solids. Organic compounds not removed by the indigenous and exogenous microbial species included benzoic acids (aromatic carboxylic acids), 2-butenoic acid (short-chain unsaturated carboxylic acid), I(2H)-isoquinolinone (heterocyclic amine), hydantoins (highly polar heterocyclic compounds), long-chain hydrocarbon length (carbon length > C15) and squalene. These organic compounds can thus be classified as poorly degradable or nonbiodegradable which contributed to the 30% COD not removed by the H-FFBR. The use of exogenous microbial species improved the quality of CGWW; however, not sufficiently to meet discharge requirements. The cost of such treatment to meet discharge requirements would be unsustainable. Alternative technologies need to be investigated for reusing or recycling the CGWW rather than discharging. <![CDATA[<b>Contextual investigation of factors affecting sludge accumulation rates in lined pit latrines within Kampala slum areas, Uganda</b>]]> Pit latrines in slums areas of Uganda fill up faster than might be expected from some estimates owing to inappropriate use and failure to consider critical factors affecting sludge accumulation rates at the planning, design and construction stages. This study sought to investigate factors affecting filling rates of lined pit latrines in slum areas of Kampala with the goal of contributing to accurate planning, design, construction, emptying and overall maintenance. Fifty-five pit latrines were selected from the five divisions of Kampala city using stratified random sampling. Data collected included: number of users, frequency of emptying, years taken since last emptying, type of non-faecal materials deposited, cross-sectional dimensions of the pit, rate of sludge degradation and geo-physical factors of pit location. Methods used were: field surveys, questionnaires and key informant interviews plus on-site depth measurement. Mass loss tests to investigate the rate of sludge degradation were carried out in the laboratory at moisture content levels similar to those in pit latrines. Sludge accumulation rates were calculated using volume of sludge in the pit, number of users and time taken since last emptying. Statistical analyses included correlation and one-way ANOVA. Results revealed that number of users and type of material deposited in the pit latrines, especially non-faecal matter, had a significant (p < 0.05) effect on sludge accumulation rate. Public pit latrines with a higher number of users had lower sludge accumulation rates and this was attributed to greater degradation taking place and greater restriction on entry of non-faecal matter. The rate of sludge degradation was higher at 90-100% than 80-90% moisture content, due to better degradation conditions. Tighter restrictions on non-faecal material deposition into pit latrines are recommended to reduce filling rates of pit latrines in slum areas. <![CDATA[<b>Congener profiles of polychlorinated biphenyls and the effect on marine mussels at an outfall site, Port Elizabeth, South Africa</b>]]> This study investigated the effect of freshwater as a point source of PCBs contributing to a marine outfall region. Inflowing and outflowing water from the North End Lake, Port Elizabeth, was collected to determine the contamination levels of polychlorinated biphenyls (PCBs). Mussels at the outflow to the sea were also sampled. The samples were analysed by an internal standard method for 6 indicator PCB congeners using gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring (SIM) mode. The total PCB concentrations in the water (dissolved plus particulate phases) ranged from 0.180 to 0.355 ng-L-1 and from 20.84 to 31.34 ng-g-1 wet weight (ww) in mussels. Lighter PCB congeners exhibited highest concentrations in the water samples while heavier PCBs were dominant in mussels. PCB-52 was the most abundant in the water samples while PCB-153 was abundant in mussels. To protect human health from the possible effects of eating fish and shellfish contaminated with PCBs, the Environmental Protection Agency regulates that the level of PCBs in water be no greater than 0.17 ng-L-1 of water. The levels of PCBs in water from the North End Lake were found to be high (0.180 - 0.355 ng-L-1) compared to the levels recommended by EPA.