Scielo RSS <![CDATA[Water SA]]> vol. 39 num. 3 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Preface</b>: <b>Water footprint</b>]]> <![CDATA[<b>Assessing urban water sustainability in South Africa - not just performance measurement</b>]]> Urban water management - and the impacts that rapid population growth, industrialisation and climate change are having on it - is gaining increasing attention worldwide. In South Africa (SA), cities are under pressure to respond to not only the challenges of water availability and quality, but also to economic transformation and social division. New solutions for improving the sustainability of cities need to be found, including the development of tools to guide decision-makers. Several benchmarking initiatives have been implemented in the SA water sector - mostly in terms of performance measurement of specific water services for regulatory purposes - but none provide an integrated analysis to enable a deeper understanding of sustainability. The research described in this paper was thus focused on using a systems approach to create an understanding of, and measure the potential for, sustainability in a South African urban water context. This has been achieved through the development and evaluation of a composite index, the Sustainability Index for Integrated Urban Water Management (SIUWM). The first step involved compiling a vision of sustainability for the SA water sector, and expanding it into a sustainability framework to help identify suitable indicators for the assessment process, as well as those which link with existing measurement initiatives. Key performance indicator results from the Department of Water Affairs' Regulatory Performance Management System (RPMS) and the Blue Drop / Green Drop schemes were used as partial input to the SIUWM, and scores were computed for the nine member cities of the South African Cities Network (SACN). The SIUWM links the results from the regulatory systems with a broader sustainability assessment process to provide a more detailed analysis which can be used to establish goals and inform strategic processes to leverage support for improved water services. In this way, the connections that link the different aspects of urban water management can be used to generate a greater awareness of the underlying issues by key decision makers and thus guide appropriate action <![CDATA[<b>Greywater reuse for toilet flushing at a university academic and residential building</b>]]> Interest in water reuse is increasing all over the world and particularly in South Africa, because of its potential to supplement scarce freshwater resources in the face of increased demand and aridity. If water reuse is to be implemented, it must be done sustainably. This study: (i) describes the perceptions of beneficiaries before and after greywater reuse (GWR) implementation; (ii) determines the attributes of greywater that were important to beneficiaries when reusing greywater and their willingness to pay for these attributes; and (iii) undertakes an economic analysis of the implemented GWR systems. To this end, two GWR systems for toilet flushing were installed. The first was installed at a university academic building at the University of the Witwatersrand, Johannesburg, and the second at a university residence at the University of Johannesburg. Perceptions highlighted included respondents' preference to reuse greywater for toilet flushing rather than irrigation, and the greater preference for GWR for toilet flushing expressed for the university academic relative to the university residential building. In sequence, 'smell', 'colour' and 'greywater tariff' emerged as the attributes of greywater that were important to respondents. In terms of payback period, net present value and benefit-cost ratio, both systems generated a net loss and were economically unfeasible <![CDATA[<b>Water demand characteristics of shared water and sanitation facilities</b>: <b>Experiences from community ablution blocks in eThekwini Municipality, South Africa</b>]]> The provision of communal water and sanitation facilities has been mandated by the South African Government as an interim measure for informal settlement upgrading. These services form the first step in the upgrading process and are essential in meeting the basic needs of the community. The eThekwini municipality is rolling out community ablution blocks to informal settlements throughout their jurisdiction. This paper investigates the water demand characteristics of these community ablution blocks, and provides a detailed methodology for collecting the data, which provides the 15-minute peak and average water demand. The results from January to November 2012 indicate that the majority of the water supply (60%) is used for laundry purposes, which includes the water used in the laundry basins and from the tap for off-site consumption, while the water demand for toilet flushing accounts for 16% of the total water supply from each facility. The peak and average water demand can be used for future hydraulic modelling of these, and other, communal ablution facilities <![CDATA[<b>A comparison of charcoal- and slag-based constructed wetlands for acid mine drainage remediation</b>]]> Subsurface-flow constructed wetlands (CW) with charcoal- or slag-based bed matrices were investigated for their potential use in remediating acid mine drainage (AMD). A CW is effectively a reactor in which some components of the wastewater are broken down by the organisms occurring within the CW, whilst others may be degraded by physico-chemical processes or a combination thereof. Two 200 ℓ small-scale CWs were built at the University. Commercially available charcoal and <19 mm basic oxygen furnace (BOF) slag were used as the bed matrices and the units were planted with a variety of plants. The units were exposed to an artificial AMD. The results showed that the systems removed almost all soluble iron and more than 75% of the sulphate. Both CWs were able to increase the pH of the AMD <![CDATA[<b>Treatability of South African surface waters by activated carbon</b>]]> Natural organic matter (NOM) in water resources for drinking purposes can be removed by different methods, including activated carbon adsorption. Due to the variability of NOM in natural waters, both in terms of its nature and its concentration, a study was undertaken to investigate NOM removal for a wide range of South African surface waters, sampled at different periods, by the use of granular activated carbon (GAC). NOM removal was assessed by measuring the ultraviolet (UV) absorbance at 3 wavelengths, namely, 254 nm (UV254), 272 nm (UV272) and 300 nm (UV300). A comparison of data between the three wavelengths showed that any of the three wavelengths can be used to assess NOM removal by GAC, which is well described by the Freundlich equilibrium equation. A treatment target of 40% removal of initial UV254 absorbance was considered. It was observed that, although the GAC dosage was generally a function of the initial UV254 absorbance, differences existed between waters. This suggests that GAC usage rate is not only a function of the initial UV absorbance but also of the NOM composition, indicating a need for improved NOM characterisation. Comparison between the UV absorbance and dissolved organic carbon (DOC) data suggested that for some waters UV254 absorbance can be used as a rapid substitute for DOC. Finally, the high GAC dosage rates required for the target criterion revealed that the process is inadequate for use at the initial stage of raw water treatment; GAC adsorption should be used at later stages of drinking water treatment. <![CDATA[<b>The impact of physico-chemical water quality parameters on bacterial diversity in the Vaal River, South Africa</b>]]> This study aimed to identify bacterial community structures in the Vaal River using PCR-DGGE (polymerase chain reaction denaturing gradient gel electrophoresis) and high-throughput sequencing. The impact of physico-chemical characteristics on bacterial structures was investigated through multivariate analysis. Samples were collected from 4 sampling stations along the Upper Vaal River during winter (June 2009) and summer (December 2010). Physico-chemical analysis was conducted on-site. Additional physico-chemical data were obtained from statutory bodies. DNA was directly isolated from water samples and PCR amplified using universal bacterial primer pairs. PCR products were subjected to DGGE fingerprinting and high-throughput sequencing, followed by Shannon-Weaver diversity calculations, cluster analysis and multivariate analysis. Physico-chemical parameters did not exceed the prescribed South African water quality standards for domestic use, aquatic ecosystems, livestock watering and irrigation. DGGE banding patterns revealed similar bacterial community structures for 3 of the 4 sampling stations. PCA and RDA indicated that pH, water temperature and inorganic nutrient concentrations could be used to explain changes in bacterial community structures. High-throughput sequencing data showed that bacterial assemblages were dominated by common freshwater groups: Cyanobacteria, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Bacteroidetes and Actinobacteria. Other freshwater phyla such as Deltaproteobacteria, Epsilonbacteria, Acidobacteria, Verrucomicrobia, Firmicutes, Fusobacteria, Flavobacteria and Fibrobacteres were found in low proportions. This study provides an overview of the dominant bacterial groups in the Upper Vaal River and the impact of environmental changes on bacterial diversity <![CDATA[<b>Development and implementation of a rapid real-time polymerase chain reaction assay for the detection of toxigenic <i>Vibrio cholerae</i> in water</b>]]> Assays which use real-time polymerase chain reaction (PCR) technology can be developed for the rapid identification of genetic sequences carried by waterborne pathogens. Rand Water has established facilities within which a selection of PCR assays will be developed. This paper reports on the optimisation and validation of the first assay to be implemented. This assay facilitates the detection of the ctxA gene of toxigenic Vibrio cholerae (V. cholerae) strains. The assay also includes an internal process control in the form of an Escherichia coli (E. coli) strain carrying a single genomic copy of the gfp gene from Aequorea victoria. Establishment of the assay required the selection of suitable PCR primers and probes for both the ctxA and gfp genes. This was followed by an optimisation phase where ideal PCR cycling conditions and primer/probe concentrations were established. A validation phase established the performance parameters of the assay. Parameters assessed included: limit of detection, sensitivity, specificity, reproducibility and robustness. The validation was conducted using potable water, surface water and sewage effluent matrices. The process has resulted in the establishment of a robust assay for the detection of toxigenic V. cholerae strains within 24 hours after samples are received. <![CDATA[<b>Characterisation of wastewater for modelling of wastewater treatment plants receiving industrial effluent</b>]]> Bio-process modelling is increasingly used in design, modification and troubleshooting of wastewater treatment plants (WWTPs). Characterisation of the influent wastewater to a WWTP is an important part of developing such a model. The characterisation required for modelling is more detailed than that routinely employed for monitoring WWTP operation. Wastewater characteristics depend on the sources within the catchment served by a particular WWTP, and the presence of industrial effluents can cause the wastewater to be significantly different from purely domestic effluent. eThekwini's wastewater treatment system is one of those most affected by industrial effluents in South Africa. Where industrial pollutants cause particular problems, additional measurements, beyond those standardly applied in sewage treatment, are required. Since influent characteristics vary from one catchment to another, this paper presents and compares results of influent wastewater characterisation from three municipal WWTPs, two of which are operated by eThekwini Water Services, which receive a combination of industrial and domestic wastewater. The paper also presents efforts to fractionate the influent COD of another WWTP run by eThekwini municipality and receiving a complex mixture of industrial and domestic effluent. The influent characterisation involves the determination of the volumes and concentrations of the carbonaceous, nitrogenous and phosphorus fractions in the wastewater, as well as other constituents present in the wastewater. This paper focuses on the carbonaceous fraction in the wastewater. <![CDATA[<b>Monitoring drinking water quality in South Africa</b>: <b>Designing information systems for local needs</b>]]> In South Africa, the management and monitoring of drinking water quality is governed by policies and regulations based on international standards. Water Service Authorities, which are either municipalities or district municipalities, are required to submit information regarding water quality and the management thereof regularly to the national Blue Drop System (BDS). Since 2009, a trend has emerged in which urban municipalities have been shown to consistently improve their water quality management whilst some of the rural and under-resourced municipalities are falling behind. A major concern has been that rural municipalities are failing to report the required information and are not complying with some of the regulator's requirements that speak to the overall management of water quality monitoring rather than the actual water quality itself. This paper reflects on a case study undertaken in four rural municipalities in South Africa where a cellphone-based information system was implemented to collect information relevant to the municipality. The study was conducted by the Information for Community Oriented Municipal Services (iCOMMS) research team based at the Department of Civil Engineering at the University of Cape Town. The hypothesis for the research was that improved information flow within rural municipalities - from water supplies in outlying areas to the municipal government office - can improve the efficiency of existing monitoring, if the design, development and implementation of such a system are based on collecting appropriate and locally relevant information. Water service authorities at the four field sites managed the process of monitoring in very different ways due to limited resources as well as structural challenges within each government department. The variety of stakeholders involved in water quality monitoring programmes, and the alternative methods and processes used, challenges the current understanding of information system design as well as the notion of developing a single national information system. The decentralisation of national water quality monitoring to municipal level was assessed in this research, which concluded that the BDS was of limited usefulness to water quality monitoring in the rural municipalities partaking in this research. <![CDATA[<b>The development of a municipal water conservation and demand management strategy and business plan as required by the Water Services Act, South Africa</b>]]> The implementation of water conservation and water demand management (WC/WDM) at municipal level has been inadequate for many years, despite South Africa being one of the driest countries in the world. This could be attributed to a lack of planning, and not realising the consequences and potential benefits of water restrictions. Many South African municipalities do not have a WC/WDM strategy and business plan although many books, publications and software packages have been produced to assist water supply managers. Most of the existing strategies are also vague and of little value, and the municipalities do not have the necessary financial, technical and institutional capacity to support such a strategy. Municipalities often fail to realise that most WC/WDM activities will pay for themselves and that financial institutions will fund these projects if a proper business case could be compiled. Ironically municipalities have complained that they are unable to obtain funding while most financial institutions complain that they cannot find bankable projects because of the poor quality of the applications and strategies. This guideline provides a simple and pragmatic approach to the development of a WC/WDM strategy and business plan which will enable municipalities to plan, obtain funding, implement and ensure the overall sustainability of water resources in the municipality and the country as a whole. <![CDATA[<b>Charging for stormwater in South Africa</b>]]> The social, economic and environmental impacts of poor water quality on South Africa's urban aquatic systems are increasingly being highlighted by the media. Improving the water quality in these systems will require catchment-wide strategies, including the monitoring and management of point and non-point source pollution collected in stormwater. Significant costs may be incurred; however, international experience suggests that these are outweighed by the benefits. Municipalities across South Africa charge their citizens for potable water and sewerage. Stormwater management, however, is generally funded through municipal rates. Competition with other pressing needs frequently results in the stormwater departments being significantly under-funded - at times only receiving a tenth of what is required for water quantity management. Internationally, an increasing number of cities have introduced a direct charge for stormwater management in order to secure the funding required to manage stormwater and its associated water pollution, and to serve as a disincentive to polluting practices on the part of landowners. In order to ensure adequate funding for storm-water management in South Africa, municipalities need to consider charging for stormwater management either based on an Equivalent Residential Unit (ERU) or Residential Equivalent Factor (REF), combined with an appropriate discount scheme for on-site stormwater management. Preliminary indicative rates have been calculated for municipalities across South Africa using the Damage Avoidance Cost (DAC) approach. The results indicate that the amount that municipalities could and should charge varies widely, from ZAR30 (2010) to ZAR110 (2010) per residential unit per month, depending on climatic zone and level of treatment. <![CDATA[<b>Assessment of a chlorine dioxide proprietary product for water and wastewater disinfection</b>]]> Chlorine on its own is adequate for many, if not most, potable water pre-oxidation and disinfection systems at plants where the application is straightforward. Similarly, most wastewater plants can be disinfected by chlorine in one of its commer cially available forms. However, when more intense pre-oxidation is required or significant iron or manganese is present in a potable supply, the use of alternative disinfectants is often preferable. Similarly, when secondary problems are present in wastewater effluent, such as high ammonia, a stronger oxidant may be preferable. Hitherto, the use of stronger oxidants has been limited to large works due to the complexity of the operational processes required. Recently, the use of ozone has spread to smaller works as new developments in equipment have become available. However, chlorine dioxide has not been used in small works until now. This paper provides details regarding a product which is simply dissolved in water in tablet or granular form and generates chlorine dioxide on solution in water. The solution is stable over weeks or even months and can be used for disinfection and or pre-oxidation purposes. The chemical was assessed in a series of tests. The performance of the chlorine dioxide product was compared against sodium hypochlorite, for different water types. The reduction in microbial counts was monitored in a secondary effluent sample and a high-ammonia secondary effluent sample. The oxidation ability in a high iron and manganese water was also assessed. A cost assessment was carried out and compared to the use of sodium hypochlorite. Other factors such as safety ease of use, and storage requirements are discussed. <![CDATA[<b>A model to assess water tariffs as part of water demand management</b>]]> Water Conservation and Water Demand Management (WC/WDM) forms part of integrated water resource management and can be used as an economically viable alternative to the upgrade of infrastructure to balance supply and demand. In order to enable effective decision-making, a model was developed in this study to estimate expected water savings and the financial impact of a change in water tariff as a WC/WDM measure. This paper describes a model that was developed for municipalities to calculate the predicted change in water use and the associated income. The model takes into account variation in price elasticity per tariff block. The effectiveness of the model as a planning tool is illustrated through an appropriate example.