Scielo RSS <![CDATA[Water SA]]> vol. 46 num. 1 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Integrated management of multiple water sources for multiple uses: rural communities in Limpopo Province, South Africa</b>]]> This study fills a knowledge gap about low-income rural communities' holistic management of multiple water resources to meet their multiple needs through multiple- or single-use infrastructure. Six low-income rural villages in Limpopo Province were selected with a diversity in: service levels, surface and groundwater resources, public infrastructure (designed for either domestic uses or irrigation but multiple use in reality) and self-supply (people's individual or communal investments in infrastructure). Focusing on water-dependent livelihoods and water provision to homesteads, distant fields and other sites of use, three policy-relevant patterns were identified. First, most households have two or more sources of water to their homesteads as a vital buffer to irregular supplies and droughts. Second, infrastructure to homesteads is normally for domestic uses, livestock and, for many households, irrigation for consumption and sale. Public infrastructure to irrigate distant fields is multiple use. Exceptionally, self-supply point sources to distant fields are single use. Water bodies to other sites of use are normally multiple use. As for large-scale infrastructure, multiple-use infrastructure is cost-effective and water-efficient. Third, in four of the six villages people's self-supply is a more important water source to homesteads than public infrastructure. In all villages, water provided through self-supply is shared. Self-supply improves access to water faster, more cost-effectively and more sustainably than public services do. In line with international debates, self-supply is there to stay and can be supported as a cost-effective and sustainable complementary mode of service delivery. A last potential policy implication regards community-driven planning, design and construction of water infrastructure according to people's priorities. This may sustainably harness the above-mentioned advantages and, moreover, communities' ability to manage complex multiple sources, uses and multiple-use infrastructure, whether public or self-supply, as a matter of daily life. <![CDATA[<b>A conceptual index for benchmarking intermittent water supply in a water distribution system zone</b>]]> Various challenges, such as limited freshwater resources, climate change impacts, rapid population growth, urbanisation and underinvestment in water supply infrastructure, have led to intermittent water supply (IWS) in potable water distribution systems. Earlier research has confirmed that IWS negatively impacts the consumers, the infrastructure and the water supply authorities. Water supply authorities need tools to help understand IWS and the associated implications. A new indexing framework involving the causes and impacts associated with IWS is presented in this paper. In addition, a novel approach allows for quantification of the severity of IWS based on knowledge of a few readily available inputs. The severity quantification is based on two ratios: the intermittency ratio is a temporal measurement, accounting for supply duration; the connection ratio describes spatial aspects, using the number of service connections affected. The indexing framework and quantification tool could lead to improved understanding of IWS and could assist water supply authorities faced with IWS to make informed decisions. Improved planning of remedial actions to mitigate or avoid risks associated with IWS is aided. The tools presented in this paper could be used as basis for future development of a key performance indicator. <![CDATA[<b>Baseline adjustment methodology in a shared water savings contract under serious drought conditions</b>]]> Baselines are often employed in shared water saving contracts for estimating water savings after some type of intervention by the water service company. An adjustment to the baseline may become necessary under certain conditions. Earlier work has described a number of relatively complex methods for baseline determination and adjustment, but application in regions faced with relatively limited data becomes problematic. If the adjustment were determined before finalising the contractual matters, it would be possible to gather the required data in order to determine the adjustment. However, in cases where no adjustment was fixed prior to the contract, a method is required to determine an adjustment mid-contract based on whatever data are available at the time. This paper presents a methodology for baseline adjustment in an existing shared water savings contract and explains how adjustment could be determined mid-contract, under conditions of limited data. The adjustment compensates for expected reduced water consumption due to external influences induced by serious water restrictions, typically introduced during periods of drought. The fundamental principle underpinning the baseline adjustment methodology presented in this paper involved segregating real water losses from the actual consumption of end-users, preferably by analysing the minimum night flow. In the absence of recorded night flows, an alternative procedure involving the minimum monthly consumption pre- and post-baseline was employed. The baseline adjustment method was subsequently applied in a South African case study, reported on separately. This technique is helpful because adjustments could be determined without adding unnecessary complexity or cost, and provides a means to resolve disputes in cases where unexpected savings occur mid-contract. <![CDATA[<b>Baseline adjustment methodology in a shared water savings contract during severe water restrictions - a case study in the Western Cape, South Africa</b>]]> A novel method for baseline adjustment in a shared water savings contract under serious drought conditions was presented in a companion paper. The newly developed baseline adjustment method was subsequently applied to a case study, as discussed in this manuscript. The case study involved application of the method to 24 relatively complex sites, spread over the Western Cape Province in South Africa. The sites included, for example, military bases, naval dockyards, an airforce base, prison facilities, large multi-storey blocks of flats and administrative office buildings. Baseline adjustment became essential mid-contract during the serious water restrictions in Cape Town at the time. The restrictions were linked to the 'Day Zero' scenario in 2018 when water supply would potentially run out, and resulted in water savings at baseline sites that were ascribed to external factors. The study incorporated a comprehensive review of the approved baseline reports with site visits to 12 of the properties. The baseline adjustment method provided a robust means to obtain adjustments for sites with relatively limited data. The minimum data requirement was a record of monthly water consumption per site. The adjustments varied between 0% and 64% of the original baseline value for the different sites in the study sample. The relatively higher adjustments were linked to sites where outdoor irrigation and pool water use was prevalent during the baseline-setting period, but was banned during the drought. Zero adjustments were found for sites with exceptionally high leakage flows that had subsequently been repaired; leaks dwarfed actual use in these cases. The results for all 24 sites were accepted by the contracting parties as being reasonable and fair. <![CDATA[<b>Numerical investigation of leakage behaviour in long radius elbows</b>]]> This paper focuses on the relationship between leakage opening areas and pressure heads for 90° long radius elbows under elastic limits using finite element analysis (SAP 2000). The results indicate that leakage opening areas grow linearly as the system pressure increases and the relation is described by the pressure-area slope (M). A sensitivity study was performed to show the effect of various parameters on M, as well as the leakage exponent (N). It was found that elbow internal diameter has the largest influence on the pressure-area slope, followed by the modulus of elasticity and finally elbow wall thickness. The longitudinal stress and Poisson's ratio have a negligible effect on M. Furthermore, leak quantity is related to the pressure raised to a power ranging from 0.495 to 0.592. Regression analysis was used to derive an empirical equation to predict the pressure-area slope of round holes within elbows with different properties. <![CDATA[<b>Private sector impact investment in water purification infrastructure in South Africa: a qualitative analysis of opportunities and barriers</b>]]> Impact investing is gaining substantial traction globally and in sub-Saharan Africa. In contrast to conventional investors, impact investors not only seek financial returns, but also measurable, positive social and environmental impact. A growing number of impact investments have been observed in the region in recent years, particularly in water purification infrastructure. This study sought to identify the primary barriers and opportunities that impact investors face in this sector. Semi-structured personal interviews were conducted with 20 experts in the South African impact-investment value chain and water provision system. Participants identified more barriers than opportunities and were mainly concerned about the lack of lifecycle support, the possibility of political interference and low financial return expectations. Interviewees did, however, acknowledge the potential influence that these investments have on local communities and economies. Experts were of the opinion that the best opportunities are found in decentralised water purification infrastructure, especially where it involves innovation at a convergence of sectors. As the public funding gap in South Africa is likely to grow in future, innovative deal structures and government support will become even more important. <![CDATA[<b>Evaluating the environmental and social net-worth of controlling alien plant invasions in the Inkomati catchment, South Africa</b>]]> The present study attempted to bridge some gaps in the existing literature evaluating the net economic worth of South Africa's Working for Water (WfW) programme for eradicating invasive alien plant species (IAPS). Specifically, the study employed the social benefit-cost analysis (BCA) methodology to assess the impact of accounting for the opportunity cost of invested capital funds and treating labour as a social benefit on the social worthiness of the WfW programme in the Inkomati catchment. The study also used improved measures of the value of other ecosystem services, particularly the carbon sequestration values. Results of the social BCA provided strong empirical evidence in support of the continuation of IAPS eradication activities, as economically and socially worthwhile investment of the country's resources. The programme generates higher net worth under lower rates of discounting future values. This confirms the importance of the water-saving benefits, which continue theoretically for ever, at zero cost to the society, as all direct and indirect financial costs cease upon completion of the eradication operations. The social net worth of the IAPS eradication programme obviously increases when expenditure on labour wages was considered a social benefit rather than a direct financial cost, even under strict project funding scenarios that require funding through private capital markets, i.e., paying commercial rates of interest. However, more strategic planning for the control of IAPS is critically important given their high cost. Challenges facing the sustainability of IAPS eradication programmes in the study area and South Africa include: raising sufficient funding from private and public sources, and introducing incentive systems to encourage higher collaboration and participation of private landowners in the currently primarily publicly driven IAPS eradication efforts. The study also suggests a number of policy and technological reforms to address the said challenges. <![CDATA[<b>National Wetland Map 5</b>: <b>An improved spatial extent and representation of inland aquatic and estuarine ecosystems in South Africa</b>]]> The improved representation of freshwater and estuarine ecosystems and associated data was a key component of the 2018 National Biodiversity Assessment, and is an essential step in enhancing defensible land use planning and decision making. This paper reports on the enhancement of the National Wetland Map (NWM) version 5 for South Africa and other data layers associated with the South African Inventory of Inland Aquatic Ecosystems. Detail is provided on (i) the extent of wetlands mapped in NWM5, compared to previous versions of the NWMs; (ii) the improved extent of inland wetlands mapped in focus areas in NWM5 relative to NWM4; (iii) the type of cover associated with the wetlands (inundated, vegetated or arid); (iv) the ecotone between rivers and estuaries; and (v) level of confidence for the inland wetlands in terms of how well the extent and hydrogeomorphic units were captured for each sub-quaternary catchment of South Africa. A total of 4 596 509 ha (3.8% of South Africa) of inland aquatic ecosystems and artificial wetlands have now been mapped, with NWM5 delineating 23% more inland wetlands (2 650 509 ha or 2.2% of SA) compared with NWM4. The estuarine functional zone, which encapsulates all estuarine processes, and associated habitats and biota, was refined for 290 systems totalling 200 739 ha, with the addition of 42 micro-estuaries totalling 340 ha. Nearly 600 000 ha (0.5% of SA) of artificial wetlands were mapped in SA. Inland wetlands are predominantly palustrine (55%), with some arid (34%) and a few inundated systems (11%). Ecotones between rivers and estuaries, ecotones where biota and processes continuously vary from freshwater to estuarine, formed a small fraction (<1.5%) of river total extent (164 018 km). Most inland wetlands (~70%) had a low confidence ranking for designation of extent and typing, because they were not mapped by a wetland specialist and not verified in the field. Future improvements of the map should be focused on catchment-based improvements, particularly in strategic water-source areas, areas of high development pressure and those with low confidence designation. <![CDATA[<b>Occurrence of PAHs in water samples of the Diep River, South Africa</b>]]> Occurrence of polycyclic aromatic hydrocarbons (PAHs) in freshwater may aggravate the water crisis currently being experienced in the Western Cape Province of South Africa. However, there is dearth of data on the levels of PAHs, which is necessary for effective assessment of water quality as well as remediation strategies. This study therefore assessed levels of PAHs in the Diep River freshwater system of Western Cape Province, South Africa. A liquid-liquid extraction solid-phase extraction gas chromatography flame ionisation detection (LLE-SPEGC- FID) method was developed to simultaneously determine the 16 United States Environmental Protection Agency (USEPA) listed priority PAHs in water samples. The SPE-GC-FID method allowed an acceptable linearity (R2 > 0.999) within the calibration range of 1 to 50 μg/mL. Instrument detection limits ranged between 0.02 and 0.04 μg/mL and instrument quantification limits between 0.06 and 0.13 μg/mL. Recovery study results were also acceptable (83.69-96.44%) except for naphthalene, which had recovery of 60.05% in spiked water matrix. The seasonal averages of individual PAH detected at the studied sites ranged between not detected (nd) and 72.38 ± 9.58 μg/L in water samples. <![CDATA[<b>The potential use of plant species within a Renosterveld landscape for the phytoremediation of glyphosate and fertiliser</b>]]> In South Africa, fertiliser and herbicide pollutants resulting from agricultural practices indirectly lead to the degradation of surface freshwater and groundwater quality. Nitrogen and phosphorus, and glyphosate, derived from agricultural fertiliser and herbicide applications, respectively, contribute to watercourse toxicity. Adjacent to many of the surface freshwater systems are some of South Africa's most productive agricultural lands, where natural ecosystems are converted to croplands, resulting in the degradation of natural vegetation and deterioration of freshwater quality. The critically endangered status of some Renosterveld vegetation types is the product of agricultural expansion, nutrient loading through fertilisation and the spraying of herbicides. A buffer of Renosterveld vegetation along river corridors may contribute to the remediation of agricultural pollutants prior to entering watercourses. The utilisation of wetland plants occurring within Renosterveld for agricultural pollutant extraction can increase river corridor biodiversity, creating indigenous refuges and facilitating habitat connectivity. A laboratory phytoremediation system was designed and constructed to investigate the pollutant-removal potential of indigenous species occurring in Renosterveld vegetation (amongst other areas), compared with commonly used invasive alien plants (IAP) in floating wetland designs. Five pollutant parameters - ammonia, nitrate, orthophosphate and two glyphosate concentrations - reflect environmental stresses on 14 wetland species naturally occurring within Renosterveld vegetation. Effluent analyses indicated significant removal efficiencies for the indigenous vegetation across both fertiliser and herbicide pollutants, with the two most effective species identified as Phragmites australis and Cyperus textilis, with 95.87% and 96.42% removal, respectively. All wetland species displayed greater pollutant removal than the unvegetated soil control and when compared to an IAP and palmiet assemblage, indicated similar pollutant-removal efficiencies, justifying their use as an acceptable alternative. <![CDATA[<b>Ecological contribution of Fenton process for generation of a ready-to-reuse dyeing and finishing effluent</b>]]> In this study, real wastewater from a dyeing factory and previously treated by biological processes was decolorized by Fenton oxidation. Direct and reactive dyebaths and the related auxiliaries constituted the polluted effluents. A synthetic wastewater was also prepared in the same way in order to compare degradation performance. The study was performed with a systematic approach, searching optimum values of H2O2 and FeSO4 concentrations, pH, temperature and the chemical structure of each tested dye. Depollution results showed that the oxidation behaviour of synthetic and real wastewaters was very similar, especially during the first stage where the breaking of chromophore groups allowed fast colour removal. However, it was found that higher ratios of [H2O2]/[FeSO4] must be engaged in the case of real wastewaters. Results also showed that the catalytic oxidation yielded a fast and complete depollution at [H2O2]/[FeSO4] = 70, pH 3 and temperature 40°C. For experiments with direct dye, colour and COD removals were, respectively, 90% and 87% in the case of real wastewater. Reactive real wastewater showed non-stable oxidation evolution due to the hydrolysed dyestuff and this led to 83% and 45% decolourization and COD removal, respectively. Better depollution results were noted for the synthetic wastewater experiments. This finding was related to the non-stable composition of the real wastewater and the unknown chemical and physical interferences between its compounds. After sedimentation, reuse of the treated wastewater for new dyeing experiments was also investigated. For this purpose, the whole process was run under complete recycling mode and the previously treated effluent was re-used as fresh dyebath. Results in terms of colour depth and fastness showed that dyeing performances were very similar, and an important opportunity is offered by reusing wastewater treated by Fenton oxidation process. <![CDATA[<b>Synthesis of PES and PES/chitosan membranes for synthetic acid mine drainage treatment</b>]]> In this study, chitosan was synthesised from chitin and used to modify polyethersulphone (PES) membrane prepared by the phase inversion method. PES membrane was blended with various concentrations of chitosan to produce PES/0.5 wt% chitosan, PES/0.75 wt% chitosan and PES/1 wt% chitosan membranes. The membranes were tested for metal and sulphate removal from acid mine drainage (AMD). The fabricated membranes were characterised using scanning electron microscopy (SEM), contact angle analyser, Fourier transform infrared (FTIR), porosity determination and pure water flux measurements. Separation performance was conducted on a dead-end filtration cell and metal ions were determined by atomic absorption spectroscopy (AAS), and ultraviolet and visible (UV-vis) spectrophotometry was used for sulphates. Pure water flux of the pristine PES membrane increased from 102 L∙m−²∙h−¹ to 107 L∙m−²∙h−¹ and 133 L∙m−²∙h−¹ for PES/0.5 wt% and PES/0.75 wt%, respectively. Further addition of chitosan to 1 wt% created a dense structure on the membrane surface, thereby reducing the flux to 120 L∙m−²∙h−¹. The rejection of cations and sulphate ions significantly improved for chitosan-modified membranes due to the creation of adsorptive and/or repulsive sites on the chitosan biopolymer as a result of amine group protonation. The results reveal that chitosan has potential to improve performance of PES membranes as a hydrophilic agent during AMD treatment. <![CDATA[<b>Feasibility and potential of separate anaerobic digestion of municipal sewage sludge fractions</b>]]> Feasibility of the separate anaerobic stabilization of primary (PS) and secondary (SS) sludge fractions produced in municipal wastewater treatment plants (WWTP) was studied at volatile loading rates (VLR) of 0.57-2.05 and 0.27-0.57 kg VS/(m³∙d) for PS and SS, respectively, corresponding to 16-30 and 14-28 d of hydraulic retention time (HRT). Laboratory-scale semi-continuous anaerobic reactors were operated at 35°C. The operational performance and quality of the final stabilized sludge were monitored. PS and SS showed opposite thickening abilities exhibiting a need for direct feeding of PS to the digesters. Biodegradability was obtained as 52(±1) and 40(±5)% volatile solid (VS) removal for PS and SS, respectively. Optimum VLR was determined according to the highest methane yield (specific methane production), VS reduction and dewaterability of the stabilised sludge. An inhibitory effect was observed at higher VLRs in PS digestion inducing a gradual reduction in the methane yield and daily production. High oil and grease content was subject to a substantial reduction in PS digestion showing a dependency on HRT. Conversely, a considerable degree of augmentation took place in the stabilised SS with no correlation to HRT at values lower than 30 d. Efficient reduction in the oil and grease content improved dewaterability in stabilised PS whereas high oil and grease content prevented an improvement for stabilised SS. Major benefits were obtained as lower HRT and high stability with higher methane production and fertilizing (N and P content) characteristics for digestion performance and stabilized SS, whereas direct feeding and higher HRT for PS digestion were determined as beneficial. <![CDATA[<b>Investigating the fate of natural organic matter at a drinking water treatment plant in South Africa using optical spectroscopy and chemometric analysis</b>]]> The removal dynamics of biodegradable dissolved organic carbon (BDOC) and natural organic matter (NOM) polarity fractions at a water treatment plant (WTP) in South Africa was studied using UV-Vis absorbance, fluorescence excitation-emission matrix, and two-dimensional synchronous fluorescence spectroscopy (SFS). This study gave insights into the transformation of NOM due to treatment processes. The objectives of the study were: (i) to use chemometric analysis and two-dimensional SFS correlations to investigate the evolution of NOM arising from treatment processes, and (ii) to access the chemical profile dynamics of polarity and BDOC fractions throughout the treatment train. The UV254 absorbance, which indicates aromaticity, reduced by 45% along the WTP. Gaussian fitting of UV-Vis data showed a decreasing trend in intensity and number of bands along the treatment process. The removal efficiency of NOM components followed the order: humic-like (HL) > tyrosine-like (TYL) > fulvic-like (FL) > tryptophan-like (TPL) > microbial-like (MBL). At the source, the relative distribution of the hydrophobic (HPO), hydrophilic (HPI), and transphilic (TPI) fractions was 45%, 31%, and 24%, respectively. The HPI was recalcitrant to treatment, and the TYL component of the HPI fraction was conjectured to be a disinfection byproduct limiting reagent. The HL and FL components of the BDOC fraction were the major substrates for bacterial growth. According to two-dimensional-SFS correlation, TYL, TPL, and MBL varied concurrently across the treatment stages. Used for the first time in South Africa, the robustness of a multi-dimensional approach of optical methods coupled with chemometric tools for the assessment of the fate of NOM along the treatment processes was revealed by this study. <![CDATA[<b>Impact of irrigation strategies on maize (<i>Zea mays</i> L.) production in the savannah region of northern Togo (West Africa)</b>]]> In northern Togo where rainfed maize is one of the major crops grown, agriculture is subject to frequent yield losses due to erratic rainfall. To ensure food availability and improve agricultural productivity, it is necessary to produce maize during the dry season under irrigation. A sound application of full and deficit irrigation requires a thorough understanding of the crop parameters and yield response to water. Thus, this study investigated the effect of full and deficit irrigation on maize plant above-ground biomass, leaf area index, canopy cover, plant height, and grain yield. A field experiment was carried out from December 2017 to April 2018 in northern Togo at the agronomic research institute. Full irrigation (FI), 80% FI, and 60% FI treatments were applied. The results showed that in the late-season stage, the differences in biomass between FI and 60% FI were significant (p < 0.05). On average, FI had the greatest grain yield (2 200.4 kg/ha), while the lowest grain yield was recorded under 60% FI (1 068.3 kg/ha). The grain yield differences between FI and 60% FI were significant. Nevertheless, the grain yield differences between FI and 80% FI were not significant (p &gt; 0.05). 80% FI had water use efficiency (WUE) (0.22 kg/m³) similar to that of FI (0.21 kg/m³), on average. The results of this study illustrate that deficit irrigation must be carefully managed since slight differences in the application volumes affect the biomass and yield of maize significantly. Under a moderate level of deficit irrigation (vegetative and reproductive growth stages) the biomass and the grain yield of maize are reduced. However, a moderate level of deficit irrigation during the vegetative growth stage could result in similar values of WUE to that of FI. <![CDATA[<b>Evaluating the suitability of fyke nets for small-scale fisheries in the Free State Province of South Africa</b>]]> South Africa is under increasing pressure to develop small-scale fisheries in inland waters. To inform appropriate development of this sector in the Free State Province, the catch rate of double-ended fyke nets was evaluated using survey data from 20 impoundments sampled during the 2013/2014 summer season. Fyke nets were set over night and the total sample effort was 114 fyke net nights. Overall catch per unit effort (CPUE) was 16.8 ± 28.3 kg·net−¹·night−¹ and catch composition was dependent on impoundment, but generally comprised of a mixture of common carp Cyprinus carpio, African sharptooth catfish Clarias gariepinus, smallmouth yellowfish Labeobarbus aeneus, Orange River mudfish Labeo capensis and moggel Labeo umbratus. The influence of temperature and the potential benefits of baiting the nets were subsequently evaluated through monthly sampling in the hyper-eutrophic Krugersdrift Dam and at the oligotrophic Gariep Dam. Baiting did not significantly influence CPUE, which was significantly higher at Krugersdrift Dam (19.97 ± 23.22 kg·net−¹·night−¹) than at Gariep Dam (5.02 ± 6.05 kg·net−¹·night−¹). Increasing temperature had a positive effect on CPUE at Krugersdrift Dam but not at Gariep Dam. Species composition also differed between impoundments and, as a result, we conclude that seasonal catch rates and species compositions will need to be evaluated prior to implementation of fyke net fisheries in specific localities.