Scielo RSS <![CDATA[Water SA]]> vol. 36 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Using satellite-based rainfall data to support the implementation of environmental water requirements in South Africa</b>]]> The methods currently available in South Africa to implement environmental flows are based on real-time rainfall-runoff models (which require accurate inputs of rainfall data) or the use of flow gauges. Both methods are useful but have limitations which must be fully understood. The main limitation of the latter approach is that there are few gauges that measure natural flow conditions in the country, and installing a new gauge can only provide information on the variability of flow characteristics after a very long period. The main limitation of utilising real-time rainfall-runoff models is that many of the rainfall stations that provided data in the past have recently closed down, while it is difficult to obtain real-time data from those that remain. The use of satellite data offers an effective and economical substitute to rain-gauge data for calculating areal rainfall estimates in sparsely-gauged regions. This study presents some examples of the use of real-time rainfall-runoff models with simple correction procedures to raw satellite rainfall estimates, which are available in near real-time from National Oceanic and Atmospheric Administration's Climate Prediction Center (NOAA CPC). The correction factors were established using existing historical rain-gauge based spatial data, over the period during which they coincide with the satellite data. The corrected satellite rainfall data were used as inputs into a pre-calibrated Pitman monthly hydrologic model which simulates natural stream flows. The results from pilot case studies demonstrate the usefulness of satellite rainfall data in hydrological modelling which supports the implementation of environmental water requirements. <![CDATA[<b>Options for meeting the ecological Reserve for a raised Clanwilliam Dam</b>]]> A recent evaluation of the potential raising of Clanwilliam Dam included an assessment of whether the operation of the dam would meet the flow quality and quantity requirements for the protection of the downstream river and its estuary, taking Olifants/Doring River basin-level considerations into account. The implications of meeting the ecological Reserve of the Olifants River downstream of Clanwilliam Dam to Bulshoek Weir, downstream of Bulshoek Weir to the confluence with the Doring River, and at the estuary, were assessed in terms of the impact on system yield. Some adjustments were made to the ecological Reserve to maximise the yield from a raised Clanwilliam Dam, in return for protection of the vitally important Doring River. Irrigation releases from Clanwilliam Dam were also restructured so that they met the ecological Reserve requirement for small floods of short duration to promote spawning in Clanwilliam yellowfish (Labeobarbus capensis). The assessments presented demonstrate that small adjustments in the requirements that form the ecological Reserve can greatly enhance the possibility, and reduce the costs, of successful implementation. <![CDATA[<b>Challenges in using fish communities for assessing the ecological integrity of non-perennial rivers</b>]]> Environmental Water Assessments (EWAs) aim to protect the ecological integrity of rivers amidst increasing anthropogenic pressures on freshwater resources, and fish communities are the ecosystem component most commonly included. The Fish Response Assessment Index (FRAI) was developed to assess the integrity of fish communities in South African rivers and is commonly applied in EWA studies. This paper reports on the suitability of the FRAI for the non-perennial Seekoei River and discusses some of the challenges faced. Our relatively long and thorough study on the Seekoei River confirmed the concerns that earlier, snapshot, fish integrity assessments in the Orange River system raised: that the existing fish indices are not ideally suited for these rivers with their naturally low species richness and hardy, generalist fish communities. Other difficulties with the use of a score-based method include prediction of the expected species, calculation of a frequency of occurrence rating, selection of the right sampling times for comparative purposes, loss of habitats and sampling points under different flow conditions, and problems experienced when using accumulated data to try to correct for a situation of having too few sampling points. At this stage a more generalised approach is suggested for the Seekoei River, and ultimately other similar non-perennial systems. This could include a number of community characteristics, such as abundance, species richness, species diversity and evenness, recruitment, fish health and the presence/absence of exotic species. <![CDATA[<b>The use of liver histopathology, lipid peroxidation and acetylcholinesterase assays as biomarkers of contaminant-induced stress in the Cape stumpnose, <i>Rhabdosargus holubi </i>(Teleostei: Sparidae), from selected South African estuaries</b>]]> Three biomarkers of contaminant-induced stress (liver histopathology, the lipid peroxidation (LPx) assay and the acetylcholinesterase (AChE) assay) were adapted for application to the estuarine-dependent marine fish Rhabdosargus holubi (Steindachner, 1881). Specimens of R. holubi were collected using a seine net from 3 temporarily open/closed estuaries in the Eastern Cape, South Africa, each impacted by different anthropogenic activities. The East Kleinemonde estuary has a housing settlement on the banks in the lower reaches and some agriculture in its catchment. The Old Woman's estuary has a golf course adjacent to its lower and middle reaches and is crossed by a national road in its upper reaches. The Mtana estuary is virtually pristine, with limited cattle grazing occurring along the banks of the estuary and some subsistence agriculture in the catchment. According to the biomarker results from this study, R. holubi from the East Kleinemonde were in good health, as reflected by low LPx and high AChE levels. The liver histopathology did, however, suggest possible previous exposure to stress (increased melanomacrophage centres, increased perivascular connective tissue and severe vacuolation). Overall, liver histopathology results did not differ significantly between estuaries. Fish from the Old Womans recorded significantly inhibited AChE and increased LPx, while fish from the Mtana exhibited significantly increased LPx only, suggesting possible exposure to anticholinesterase contaminants in the former estuary and some form of oxidative stress in the latter. Although water samples were collected from each of the 3 estuaries and analysed for polychlorinated biphenyls, organochlorines, organophosphorous pesticides and pyrethroids, none of these chemicals were detected. As pesticide residues in water are highly variable, both temporally and spatially, future studies should focus on measuring tissue burdens of organisms in order to identify the contaminant stressor. This study has shown that while chemical analyses of water provide a 'snap-shot' of water quality at the time of sampling, biomonitoring can integrate past exposures to stress and is thus useful for identifying potential situations of concern that require further detailed investigation. <![CDATA[<b>Comparison of conventional culture and real-time quantitative PCR using SYBR Green for detection of <i>Legionella pneumophila</i> in water samples</b>]]> The genus Legionella comprises more than 40 species and 64 serogroups with approximately half of those species associated with human diseases. Legionella pneumophila Serogroup 1 is the most common pathogenic species and is responsible for up to 80% of legionellosis cases in the world. Legionella levels in water are assessed routinely by culture on a selective medium, but its slow growth is a serious drawback, given that at least 10 days are required to obtain results. In an attempt to provide a simple screening method for Legionella pneumophila in water systems samples a real time PCR assay using SYBR Green was developed. A total of 50 samples from cooling towers and hot tap water systems were analysed by DNA amplification using 2 pairs of primers targeting the mip and dot genes. Legionella pneumophila Serogroup 1 (NCTC12821) was used as a reference strain and to evaluate real-time PCR performance. The assays were successful with both primer sets; good and similar amplification efficiencies were achieved. In addition, high sensitivity was obtained; the method proved to allow for the detection of fewer than 10 gene copies per reaction. Results of real-time PCR were compared to conventional analysis based on culture. Although no strong correlation was observed between both methods and consequently real-time PCR could not substitute for the reference method, it represents a powerful screening tool. The inexpensive, sensitive and rapid real-time PCR based in SYBR Green method is of interest in monitoring Legionella pneumophila contamination, especially in environmental samples, and should be economical for large-scale routine tests. <![CDATA[<b>The abundance of <i>Cryptosporidium </i>and <i>Giardia</i> spp. in treated effluents produced by four wastewater treatment plants in the Gauteng Province of South Africa</b>]]> This study aimed at assessing the effectiveness of 4 wastewater treatment plants of the Gauteng Province, namely Zeekoegat, Baviaanspoort, Rayton and Refilwe Water Care Works (WCW), in the removal of Cryptosporidium and Giardia (oo)cysts. Wastewater influent and treated effluent samples were taken weekly between January and April 2008. Cryptosporidium and Giardia (oo)cysts were detected by immunofluorescence and immunomagnetic separation, according to a modified US EPA 1623 method. Effluent samples were subjected to a molecular study for the identification of Cryptosporidium parvum Genotype I and Giardia lamblia Assemblage A. The 18S rRNA gene for restriction digests was therefore used to characterise these (oo)cysts. Cryptosporidium oocysts were repeatedly detected in effluent samples collected from all wastewater treatments at lower concentration (range <1 to 40 oocysts/L) levels than Giardia cysts (range <1 to 175 cysts/ℓ). The mean removal efficiencies of Cryptosporidium and Giardia at the 4 wastewater treatment plants ranged from 67.40% to 98.26% and from 86.81% to 99.96%, respectively. For all effluent samples, except Zeekoegat WCW, 29% and 41% contained oocysts of Cryptosporidium parvum Genotype I and cysts of Giardia lamblia Assemblage A, respectively. Both C. Parvum and G. lamblia are human pathogens. This stresses the potential risk of discharging these parasites into receiving water bodies. <![CDATA[<b>Synthesis of silver impregnated carbon nanotubes and cyclodextrin polyurethanes for the disinfection of water</b>]]> Silver impregnated carbon nanotubes and cyclodextrin polymers were synthesised by first functionalising carbon nanotubes in a mixture of nitric and sulphuric acid before impregnating them with silver nanoparticles. The silver impregnated functionalised carbon nanotubes were then polymerised with β cyclodextrin using hexamethylene diisocyanate as the linker. The polymers were characterised using various techniques. The polymers were then tested for their ability to destroy bacteria in water and were found to reduce bacterial cell counts in water spiked with E. coli (ATCC 25925) to as low as zero cfu/mℓ. Furthermore, the polymers could absorb 58% of para-nitrophenol from water spiked with this organic compound, which is a known pollutant in water. <![CDATA[<b>The effect of conditioning with NaCl, KCl and HCl on the performance of natural clinoptilolite's removal efficiency of Cu<sup>2+</sup> and Co<sup>2+</sup> from Co/Cu synthetic solutions</b>]]> Southern African clinoptilolite's capability as an ion-exchanger with respect to Cu2+ and Co2+ was investigated in order to consider its viability in the removal of metal cations from aqueous solutions. The effect of chemical conditioning was investigated using sodium chloride (NaCl), hydrochloric acid (HCl) and potassium chloride (KCl). The most efficient activating or conditioning reagent was found to be HCl at 0.02 M concentration, followed by KCl at 0.04 M and then NaCl at 0.04 M. The worst performing clinoptilolite was the original form under the conditions described in this study and it thus served as a control. The HCl-conditioned clinoptilolite was the most efficient in metal removal (79% Co2+ and 73% Cu2+) followed by the NaCl-conditioned form (69% Co2+ and 54% Cu2+), while the KCl-conditioned form adsorbed 54% and 73% of Co2+ and Cu2+, respectively. The column method was used for the cation-exchange processes with synthetic solutions of 0.0020 M, 0.0698 M and 0.2000 M of Co2+ and Cu2+ concentrations which were measured using atomic absorption spectroscopy (AAS). <![CDATA[<b>The effect of silica concentration on the biosorption of Cu<sup>2+ </sup>and Co<sup>2+ </sup>from aqueous solutions mediated by strains of <i>Bacillus</i></b>]]> Bacillus strains were isolated from a mine tailings dump in Nigel town, south-east of Johannesburg. These were then grown at 37(±0.5)ºC in a trace element-agitated liquid media. The effects of pH, contact time, initial ion concentration and the presence of co-cations were studied to ascertain the optimal conditions for biosorption to take place. Test solutions contained 0.002 M, 0.07 M and 0.2 M of either copper or cobalt ions. The Bacillus strains removed the copper and cobalt more efficiently from solutions of low concentration (0.002 M and 0.07 M) than from solutions of high concentration (0.2 M) over a 48 h period. Maximum biosorption was obtained at pH 6.5 and 5.5 for copper and cobalt solutions, respectively. The presence of silica led to an initial increase in both copper and cobalt biosorption, though higher concentrations of silica resulted in a decrease in metal uptake by Bacillus strains. <![CDATA[<b>Optimising the allocation of groundwater carrying capacity in a data-scarce region</b>]]> Traditional analysis approaches to water resource carrying capacity cannot be directly applied to data-deficient regions where water resources have been exploited excessively. Gross domestic products (GDPs) also cannot be used directly as objective functions of regional benefits. New objective functions should be established by analysing limited available data and mining useful implied information. Based on the principle of water resource supply-demand balance, a new evaluation criterion of regional benefits is presented using the non-linear regression analysis approach. An analysis model of groundwater carrying capacity was then established and is solved with the Lagrange multiplier method. A case study of groundwater resource carrying capacity in 2010 and 2015 in the Yaoba Oasis irrigation district, Alxa Left Prefecture, Inner Mongolia Autonomous Region, China, was performed. Results demonstrate that the model has the ability of evaluating and determining the groundwater resource carrying capacity in this overloaded and data-scarce region. The carrying capacity level of groundwater in this irrigation district is rather low and the development potential is limited. In order to reduce the exploitation of groundwater resources and achieve the sustainable development of the oasis in future, a system of agricultural water-saving irrigation must be set up to reduce the irrigation quotas and the irrigation water requirement. The arable areas should be reduced and the living standards of local people should also be raised. The results obtained from these applications have proved that the analysis model presented in this study is a new and promising method which can be employed in data-scarce and overloaded regions. <![CDATA[<b>A conceptual model for the development and management of the Cape Flats aquifer, South Africa</b>]]> This paper provides an integrated approach to the analysis of the geological, hydrological and hydrogeological characteristics of the Cape Flats: a coastal plain sand formed within the mountains of the Cape Town metropolitan area. The study is mainly based on evaluation of available data, on surface water and groundwater, rainfall and selected springs, to describe the Cape Flats aquifer. Qualitative analysis has shown that both surface water and groundwater of the investigated area are of good quality; whereas sources of contamination indicated are restricted to certain parts of the area. Interpretation of hydrogeological data and aquifer parameters revealed that the Cape Flats aquifer has good storage characteristics to support its development for water supply, although the generally unconfined conditions render it highly susceptible to pollution from the surface. From the analysis of long-term climate data in Cape Town, it is evident that fluctuation exists in the pattern of rainfall; this rainfall pattern has implications for recharge and water management issues in the city. Therefore, a conceptual hydrogeological model was developed to elucidate groundwater flow and recharge mechanisms in the Cape Flats. <![CDATA[<b>Framework for local government to implement integrated water resource management linked to water service delivery</b>]]> The Water Services Act (No. 8 of 1997) of South Africa states that water service delivery is the responsibility of local government as Water Services Authorities. The principal legal responsibility is to complete a Water Services Development Plan (WSDP) every 5 years with annual review. The WSDP encapsulates all the responsibilities and tasks required in water service delivery. However, it does not spell out local government's role in water resource protection or its responsibilities as far as integrated water resource management is concerned. It is well known in South Africa that there is a challenging level of inadequate capacity in technical and administrative skills in local government to adequately fulfil water service delivery. This paper highlights the consequences of this incapacity for municipalities and their difficulties in fulfilling their responsibilities as service providers. A framework is provided within which improvements can be brought about, with guidance on how to engage in the practice of integrated water resource management (IWRM) in the context of the legal framework for water services. The additional tasks and changes required to practise IWRM are set in the context of the WSDP. The framework provides a guide for a municipality to first accomplish an adequate WSDP, and then to gradually implement IWRM. A discussion on the skills needed to accomplish, firstly, a comprehensive WSDP, and secondly, IWRM, is included. <![CDATA[<b>Water network rehabilitation</b>: <b>a group decision-making approach</b>]]> Rehabilitation of water networks is a complex problem which may require a range of different water management actions, involving groups or institutions having differing objectives, responsibilities and interests, and requiring collaboration for conflict resolution. Group decision making can play a vital role in situations where multiple actors are involved, each having their own private perceptions of the context and the decision problem to be tackled. This paper proposes a group decisionmaking model based on an analysis of individual rankings, with the aim of choosing an appropriate alternative which is the best compromise of the points of view of the actors involved in the decision problem. An application with 4 influence groups was conducted based on the proposed method. <![CDATA[<b>Flux flow and cleaning enhancement in a spiral membrane element, using continuous infrasonic backpulsing</b>]]> The effect of backpulsing, into the permeate space of a 2.5 inch spiral wrap membrane, on the prevention of fouling (flux enhancement) was investigated experimentally. These experiments were performed using a 500 mg·<img src="/img/revistas/wsa/v36n4/a15exp01.gif">-1 dextrin solution and a 100 000 MCWO polypropylene membrane, with a feed pressure of 100 kPa and a cross-flow rate of 1 000 <img src="/img/revistas/wsa/v36n4/a15exp01.gif">·h-1. Experimental results showed that a backpulse with a duration of about 170 ms, a repeat frequency of 1 s and differential peak pulse pressure, measured at the outlet of the permeate space, of 38 kPa gave the best results for the parameters used in the current experiments. In this case the saturation flux with backpulsing was 82% of the clean water value and 3.9 times the saturation flux obtained with no backpulsing. <![CDATA[<b>Optimisation of the membrane-assisted passive sampler and its comparison with solid phase extraction technique</b>]]> A novel membrane-assisted passive sampler was further optimised in the laboratory. It was then compared to the solid phase extraction technique in terms of the extraction efficiency, enrichment factor, detection limit and selectivity in wastewater. The passive sampler was exposed to 3 <img src="/img/revistas/wsa/v36n4/a15exp01.gif"> wastewater samples under laboratory conditions for 3 days. Five hundred millilitres of wastewater was extracted with C18 cartridges. The extraction efficiency of the passive sampler ranged from 4 to 10% while in solid phase extraction it was 40 to 67% for the 3 chlorophenols. In both cases, extraction efficiency was highest for 2,4-dichlorophenol. The low extraction efficiency in the passive sampler supports the idea that it is not an exhaustive extraction technique and does not disturb the chemical equilibrium of the sample. It therefore measures the bioavailable fraction of the compound and can be used for equilibrium sampling and extraction. The obtained enrichment factors from the passive sampler were 89 and 295 for 2-chlorophenol and 2,4-dichlorophenol, respectively. From solid phase extraction, enrichment factors of 102, 113 and 167 were obtained for 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol, respectively. The enrichment factor (~2.5) and sampling rates (~28 µ<img src="/img/revistas/wsa/v36n4/a15exp01.gif">·h-1) were both low for 4-chlorophenol in wastewater from passive sampler extraction. The calculated sampling rates were found to be 2 604 µ<img src="/img/revistas/wsa/v36n4/a15exp01.gif">·h-1 for 2-chlorophenol, 1 074 µ<img src="/img/revistas/wsa/v36n4/a15exp01.gif">·h-1 for 4-chlorophenol and 5 089 µ<img src="/img/revistas/wsa/v36n4/a15exp01.gif">·h-1 for 2,4-dichlorophenol in spiked deionised water. In wastewater, the sampling rates were found to be 1 544 µ<img src="/img/revistas/wsa/v36n4/a15exp01.gif">·h-1 for 2-chlorophenol, 28 µ<img src="/img/revistas/wsa/v36n4/a15exp01.gif">·h-1 for 4-chlorophenol and 5 106 µ<img src="/img/revistas/wsa/v36n4/a15exp01.gif">·h-1 for 2,4-dichlorophenol. The passive sampler was found to be superior in its selectivity towards the target compounds compared to solid phase extraction technique with C18 sorbent. Chromatograms from solid phase extraction of wastewater contained high peaks of unidentified, potentially interfering compounds, especially in the early part of the chromatogram. In contrast, chromatograms from the passive sampler extraction were very clean. The detection limits of the passive sampler were comparable with that of solid phase extraction and were around 1.5 µg·<img src="/img/revistas/wsa/v36n4/a15exp01.gif">-1 except for 4-chlorophenol that was high in wastewater (~100 µg·<img src="/img/revistas/wsa/v36n4/a15exp01.gif">-1). <![CDATA[<b>Effect of altitude on erosive characteristics of concurrent rainfall events in the northern KwaZulu-Natal Drakensberg</b>]]> High-resolution rainfall data from two stations in the northern KwaZulu-Natal Drakensberg provide insight into the effect of altitude on individual rainfall event characteristics. The effect of altitude on the duration and erosivity (rainfall intensity and kinetic energy) of concurrent rainfall on the escarpment and in the foothills is analysed using 5-min interval data for the calendar year 2003. A cumulative total of 229 rainfall events, measured at the Royal Natal National Park station (1 392 m a.m.s.l.) and a temporary station on the escarpment at Sentinel Peak (3 165 m a.m.s.l.), were considered, of which 79 rainfall events were found to fall concurrently at the two stations. The data indicate that the concurrent events generate rainfall for longer on the escarpment, but that the amount of rain produced as well as the intensity at which it falls is less than that in the foothills, both in summer and winter. The escarpment appears to limit erosivity, with only 11 events meeting the set criteria for erosivity in the foothills but failing to meet the same criteria on the escarpment. This decrease in erosivity contrasts with previous models for the Drakensberg that demonstrate higher erosivity in the upper reaches, but concurs with studies in mountainous regions elsewhere which found that erosivity decreases with altitude. It is tentatively suggested that the difference in rainfall characteristics could be related to the sources of precipitation and the manner in which the escarpment zone affects the formation and distribution of rainfall. The paper also highlights the need for further research into the association between rainfall structure and synoptic conditions and the effect that the escarpment has on modifying large-scale rainproducing systems in the KwaZulu-Natal Drakensberg.