Scielo RSS <![CDATA[Water SA]]> vol. 34 num. 2 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Trusting consumers: Involving communities in municipal water service decision making in Durban, South Africa</b>]]> The Constitution of 1996 sets out the government's responsibility to provide the public with the opportunity to be involved in government decisions that affect their lives (R Kasrils, Former Minister of Water Affairs and Forestry, 2001) Participation is a guiding principle of South Africa's post-apartheid water sector reforms. Yet studies indicate that substantive and effective participation has been difficult to achieve. In an effort to develop sustainable and creative dialogue with consumers, the University of KwaZulu-Natal in partnership with eThekwini Water and Sanitation (EWS) piloted the establishment of community-based focus groups in 3 different types of communities. The goals of the project were to build trust, generate social capital and widen the store of available methods for enhancing dialogue between service providers and consumers. This paper details the methods used. This pilot formed part of a larger strategy to develop and refine a methodology to be used in a municipality-wide research and engagement strategy involving a diverse selection of wards. At the time of publication, research in 6 wards and one similar study with people with disabilities were complete. <![CDATA[<b>A comparison of satellite hyperspectral and multispectral remote sensing imagery for improved classification and mapping of vegetation</b>]]> In recent years the use of remote sensing imagery to classify and map vegetation over different spatial scales has gained wide acceptance in the research community. Many national and regional datasets have been derived using remote sensing data. However, much of this research was undertaken using multispectral remote sensing datasets. With advances in remote sensing technologies, the use of hyperspectral sensors which produce data at a higher spectral resolution is being investigated. The aim of this study was to compare the classification of selected vegetation types using both hyperspectral and multispectral satellite remote sensing data. Several statistical classifiers including maximum likelihood, minimum distance, mahalanobis distance, spectral angular mapper and parallelepiped methods of classification were used. Classification using mahalanobis distance and maximum likelihood methods with an optimal set of hyperspectral and multispectral bands produced overall accuracies greater than 80%. <![CDATA[<b>The quality of environmental impact reports for projects with the potential of affecting wetlands in South Africa</b>]]> In South Africa certain development activities, which may have a substantial detrimental effect on the environment, require an environmental impact assessment (EIA), including projects with the potential of affecting wetlands. A key element of the EIA process is the submission of an environmental impact report (EIR) for review in order to determine whether the report is adequate and/or whether a greater quantity of information is required before the project can be authorised. The information available to decision-makers in the EIR is a major determinant in the outcome of wetland protection and/or destruction. The quality of 4 environmental impact reports of large projects with the potential of impacting on wetlands was assessed using an EIA report quality review checklist. It is concluded that the quality of the 4 reports was generally satisfactory but certain areas were found to be poorly performed, i.e. identification and evaluation of impacts to the potential detriment of the wetlands for which the EIAs were performed To improve the quality of the reports for projects with the potential of affecting wetlands it is recommended that a quality review checklist be used by EIA practitioners and authorities as an additional tool to the EIA regulations and the integrated environmental management series. This should assist in ensuring that key aspects are addressed before submission to the relevant authority, and will also contribute to establishing a baseline of EIR quality for evaluation of wetlands EIA practice under the new regulations promulgated in 2006. <![CDATA[<b>Physical and chemical characteristics of thermal springs in the Waterberg area in Limpopo Province, South Africa</b>]]> The Limpopo Province in South Africa is richly endowed with thermal springs. Some have been developed for recreational, tourism or other purposes, while a number remain completely undeveloped. If the full economic potential of springs can be realised in a sustainable manner, they could make a substantial contribution to the local or even regional economy. The optimal use of a thermal spring is largely dependent upon its physical and chemical characteristics. This article focuses on the temperature and chemical features of 8 selected thermal springs located in the southern (Waterberg) region of the Limpopo Province, namely Warmbaths, Loubad, Vischgat, Die Oog, Rhemardo, Lekkerrus, Libertas and Buffelshoek. All of these springs are of meteoric origin, with water temperatures ranging from 30°C to 52°C. The mineral composition of the thermal waters reflects the geological formations found at the depth of origin. Changes in land use that occurred over the past few decades have apparently had no impact on the physical and chemical properties of the thermal spring waters. This effect may, however, become evident at a later stage due to a time lag in the migration of contaminants. The fluoride concentration of water from seven of the eight springs (all except Loubad) does not conform to domestic water quality guidelines and makes the water unfit for human consumption. Unacceptably high values of mercury were detected at Libertas. It is recommended that strict monitoring of the concentration of fluoride and other potentially harmful elements should be mandatory whenever the thermal spring water is used for bottling, domestic or full-contact recreational purposes. <![CDATA[<b>Inter-basin water transfer effects on the invertebrates of the Mvuzane River: A test of the SASS rapid biomonitoring protocol to assess the impact of flow modification</b>]]> Effects of the transfer of water from the Thukela to the Mvuzane River were investigated using the SASS rapid bioassessment technique and more quantitative methods of guild composition and community analyses. Although the transfer was relatively small (< 1 m³/s) it completely dominated natural flows in the recipient system. SASS monitoring was found to be useful as a rapid, field-based assessment of water quality and can be used to act as a 'red flag' to problems in the future. However, it was not sensitive to changes in the community structure at different sites and was inefficient as a tool to investigate the wider ecological impacts of the transfer scheme, most notably those associated with flow modification. Changes in the invertebrate fauna were most easily explained in terms of the effect of increased flow velocities and volumes on taxa that were classified as 'swimmers' and 'skaters'. Impacts via disruption to trophic pathways cannot be discounted and will most certainly occur with prolonged water transfer. <![CDATA[<b>Towards revised physically based parameter estimation methods for the Pitman monthly rainfall-runoff model</b>]]> This paper presents a preliminary stage in the development of an alternative parameterisation procedure for the Pitman monthly rainfall runoff model which enjoys popular use in water resource assessment in Southern Africa. The estimation procedures are based on the premise that it is possible to use physical basin properties directly in the quantification of the soil moisture accounting, runoff, and recharge and infiltration parameters. The results for selected basins show that the revised parameters are at least as good as current regionalised sets or give satisfactory results in areas where no regionalised parameters exist. <![CDATA[<b>Optimisation of <i>Bacillus thuringiensis</i> var. <i>israelensis</i> (Vectobac<sup>®</sup>) applications for the blackfly control programme on the Orange River, South Africa</b>]]> The Orange River, South Africa's largest river, is a critical water resource for the country. In spite of the clear economic benefits of regulating river flows through a series of impoundments, one of the significant undesirable ecological consequences of this regulation has been the regular outbreaks of the pest blackfly species Simulium chutteri and S. damnosum s.l. (Diptera: Simuliidae). The current control programme, carried out by the South African National Department of Agriculture, uses regular applications, by helicopter, of the target-specific bacterial larvicide Bacillus thuringiensis var. israelensis. While cost-benefit analyses show significant benefits to the control programme, benefits could potentially be further increased through applying smaller volumes of larvicide in an optimised manner, which incorporates upstream residual amounts of pesticide through downstream carry. Using an optimisation technique applied in the West African Onchocerciasis Control Programme, to a 136 km stretch of the Orange River which includes 31 blackfly breeding sites, we demonstrate that 28.5% less larvicide could be used to potentially achieve the same control of blackfly. This translates into potential annual savings of between R540 000 and R1 800 000. A comparison of larvicide volumes estimated using traditional vs. optimised approaches at different discharges, illustrates that the savings on optimisation decline linearly with increasing flow volumes. Larvicide applications at the lowest discharge considered (40 m³∙s-1) showed the greatest benefits from optimisations, with benefits remaining but decreasing to a theoretical 30% up to median flows of 100 m³∙s-1. Given that almost 70% of flows in July are less than 100 m³∙s-1, we suggest that an optimised approach is appropriate for the Orange River Blackfly Control Programme, particularly for flow volumes of less than 100 m³∙s-1. We recommend that trials be undertaken over two reaches of the Orange River, one using the traditional approach, and another using the optimised approach, to test the efficacy of using optimised volumes of B.t.i. <![CDATA[<b>Prediction of groundwater levels from lake levels and climate data using ANN approach</b>]]> There are many environmental concerns relating to the quality and quantity of surface and groundwater. It is very important to estimate the quantity of water by using readily available climate data for managing water resources of the natural environment. As a case study an artificial neural network (ANN) methodology is developed for estimating the groundwater levels (upper Floridan aquifer levels) as a function of monthly averaged precipitation, evaporation, and measured levels of Magnolia and Brooklyn Lakes in north-central Florida. Groundwater and surface water are highly interactive in the region due to the characteristics of the geological structure, which consists of a sandy surficial aquifer, and a highly transmissive limestone-confined aquifer known as the Floridan aquifer system (FAS), which are separated by a leaky clayey confining unit. In a lake groundwater system that is typical of many karst lakes in Florida, a large part of the groundwater outflow occurs by means of vertical leakage through the underlying confining unit to a deeper highly transmissive upper Floridan aquifer. This provides a direct hydraulic connection between the lakes and the aquifer, which creates fast and dynamic surface water/groundwater interaction. Relationships among lake levels, groundwater levels, rainfall, and evapotranspiration were determined using ANN-based models and multiple-linear regression (MLR) and multiple-nonlinear regression (MNLR) models. All the models were fitted to the monthly data series and their performances were compared. ANN-based models performed better than MLR and MNLR models in predicting groundwater levels. <![CDATA[<b>Application of geographic weighted regression to establish flood-damage functions reflecting spatial variation</b>]]> Flood damage functions are necessary to ensure comprehensive flood-risk management. This study attempts to establish a residential flood-damage function through interviewing the residents living in the region where flood disasters occur frequently. Keelung River basin, near Taipei Metropolitan in Taiwan was selected as study area. Flood damages are related to the flood depths, which are the most commonly considered factor in previously published work. Ordinary least squares (OLS) regression was used to construct the flood-damage function at the beginning. Analytical results indicate that flood depth is the significant variable, but the spatial pattern of the residuals shows that residuals exhibit spatial autocorrelation. The Geographically Weighted Regression (GWR) Model was then applied to modify the traditional regression model, which cannot capture spatial variations, and to reduce the problem of spatial autocorrelation. The R-square value was found to increase from 0.15 to 0.24, and the spatial autocorrelation in the residuals was no longer evident. A modified OLS model with a dummy variable to capture the spatial autocorrelation pattern was also proposed for future applications. In conclusion, the residential flood damage is determined by flood depth and zone, and the GWR model not only captures the spatial variations of the affecting factors, but also helps to discover the independent variable to modify the traditional regression model. <![CDATA[<b>Optimisation procedure for pipe-sizing with break-repair and replacement economics</b>]]> The importance of incorporating break-repair costs and pipe-replacement costs in optimal design of a water distribution network is highlighted and demonstrated with a hypothetical network. Deterioration due to ageing of pipes requires expensive maintenance and causes inconvenience. The number of breaks generally increases exponentially with pipe age and small-diameter pipes are more likely to break than large-diameter pipes. After a certain age, it would be more cost-effective to replace the pipes than to repair them. The optimisation models which do not consider the maintenance costs tend to result in smaller pipe sizes. The proposed model incorporates both the repair cost and the replacement cost in addition to initial cost. The proposed model is demonstrated by applying it to a 2-loop network. Incorporating pipe-break and replacement economics into optimisation leads to slightly larger diameter pipes. The analysis also reveals that consideration of repair/replacement is essential if the pipe breaks cause high economic impact, the pipe-break growth rate increases fast and discount rate is low. For the example network considered, for a typical set of values, the cost benefit is as much as 12.92%. For cases with low breakage rates, incorporating repair/replacement has been found to make no practical difference. The results show that considering pipe break and pipe replacement in optimisation is important as this could save considerable amounts of money over the lifetime. <![CDATA[<b>An iterative optimisation procedure for the rehabilitation of water-supply pipe networks</b>]]> This paper presents an iterative method for the optimisation of the total costs for the rehabilitation of water-supply pipe networks with flow and pressure deficiency at the consumer nodes. The procedure is based on the exchange gradient concept of Granados for the economic design of pressurised networks. The substitution of pipe sections, relining and increase in pumping head are considered as being rehabilitation options. An initial solution is obtained for the deficient network by determining the required pumping head that would meet the pressure and discharge requirements at all the nodes. Subsequently, the pumping head is reduced in stages and for each reduction; the network of minimum cost is obtained by the substitution or relining of individual pipes in part or in full. The optimal solution is reached when the marginal annual cost of pipe rehabilitation exceeds the reduction in annual pumping costs. <![CDATA[<b>Batch and automated SVI measurements based on short-term temperature variations</b>]]> Effects of short-term temperature variations on the sludge volume index (SVI) are evaluated with batch and automated mixed liquor suspended solids (MLSS) settling tests. The test-cylinder environment and meteorological conditions have a direct influence on the MLSS sample temperature (Ts). A T change of 4.3°C over the 30 min settling test duration results in an inverse SVI change of 63.0 mℓ/g, at an average SVI decrease of 14.8 mℓ/g per 1°C T increase. T compensation or control during routine SVI tests is not common practice, partially due to a lack of temperature-controlled equipment and an absence of Ts-based MLSS settling models. A practical solution is found to reduce Ts variations experienced before and during batch MLSS settling tests. An automated MLSS settling meter is used to demonstrate a semi-continuous on-line method to determine SVI at the operational reactor temperature (T) of a full-scale plant. Basic and best-fit SVI models are obtained from the SVI data generated over diurnal periods, based on MLSS concentration and T fluctuations. These SVI models confirm the inverse dependence of SVI on temperature for the site-specific conditions. A diurnal T fluctuation of 1.8°C results in an SVI change of 26.6 mℓ/g, at an average -14.8 mℓ/g SVI change per 1°C Tr variation. <![CDATA[<b>Management of hydrogen sulphide generation at a Kraft mill effluent plant</b>]]> Communities surrounding an integrated Kraft mill noticed odours from the mill's effluent treatment plant. A project was therefore commissioned by the mill to proactively manage the odours from both the pulp-processing operations and the effluent treatment plant. This project formed part of a co-ordinated study that was implemented by the mill to limit emissions of the total reduced sulphur (TRS) components from the pulp mill operations. It was found that sulphate-reducing bacteria (SRB) converted the sulphates present in the effluent to hydrogen sulphide (H2S) by dissimilatory respiration. The combined use of a nitrate-releasing biomodifier (Bulab® 9518) and an anthraquinone sulphate-reduction inhibitor (Busperse® 2432) was effective in reducing both SRB activity and H2S levels. The average aqueous H2S levels (40 mg/ℓ) were reduced to between 92% and 99%. <![CDATA[<b>Nitrite effect on the phosphorus uptake activity of phosphate accumulating organisms (PAOs) in pilot-scale SBR and MBR reactors</b>]]> Batch tests were performed to investigate the nitrite effect on the P-uptake of biomass grown in pilot-scale SBR and MBR systems. The results showed that the nitrite has an inhibitory effect on the aerobic P-uptake of the SBR and the MBR biomasses. The degree of inhibition was observed to be 65 % and 37 % at 10 mg NO2-N/ℓ for the SBR and the MBR respectively. Both biomasses were found capable of using nitrite as electron acceptor as effectively as nitrate. Moreover, for the SBR biomass the anoxic P-uptake rate using nitrite was found even higher (60%) than the P-uptake rate with nitrate. From a modelling point of view, the current models require appropriate extensions to describe these various effects of nitrite. Hence, an extension of the ASM2d model has been provided. Prevention of nitrite build-up in full-scale EBPRs will eliminate the nitrite inhibition problem. Alternatively one can adopt a proactive approach in which the aerobic P-uptake phase is replaced with an anoxic P-uptake phase using only nitrite as electron acceptor. Such an approach offers considerable cost savings and enhanced nitrogen and phosphorus removal. This, however, requires further research for experimental validation and testing. <![CDATA[<b>Faecal coliforms, faecal enterococci, <i>Salmonella</i> Typhi and <i>Acanthamoeba</i> spp. UV inactivation in three different biological effluents</b>]]> Efficiency of UV-light to inactivate microbial indicators, Salmonella Typhi and Acanthamoeba spp. was studied in three different biological secondary effluents. Even though effluents differed in terms of their total suspended solids content, transmittance and particle size distribution, the UV-light dose required to fulfil WHO agricultural water reuse criteria was the same (30 mW-s/cm²), because the particle content with sizes >40 |xm was similar and very small. Using this dosage, 3 log of Salmonella Typhi and faecal enterococci were also inactivated. To avoid faecal coliform and Salmonella Typhi photoreactivation, the UV dose had to be doubled and in the process 2.5 log of Acanthamoeba spp. were also inactivated. This is interesting because its presence in wastewater, pathogenicity and resistance to conventional disinfection processes has been reported in the literature. Additionally, it was found that the faecal coliforms' inactivation rate constant was the lowest one of all the bacteria studied (Salmonella Typhi and faecal enterococci), suggesting the limitation of this indicator when several kinds of pathogens are present, as is the case in developing countries. <![CDATA[<b>Observations on daily rainfall events in the KwaZulu-Natal Drakensberg</b>]]> Five-minute rainfall data measured at different stations in the KwaZulu-Natal Drakensberg are presented and although the data are limited this paper is the first to analyse individual rainfall events in the area. The occurrence of rain days in the Drakensberg shows strong seasonality with most rain recorded during the summer months. Although the number of rain days as well as the number of rainfall events increases with an increase in altitude, the mean daily rainfall and mean rainfall generated from individual events is less on the escarpment than in the foothills. All stations show a high percentage of rain days with single rainfall events as well as a high proportion of rainfall received from events generating more than 10 mm, but the escarpment station receives less rainfall from these events than the stations in the foothills. It is known that rainfall in the Drakensberg is mostly generated from thunderstorms, and data presented here indicate that rainfall predominately occurs in the late afternoon/early evening when sufficient cooling has possibly taken place for condensation and cloud formation to occur. <![CDATA[<b>Non-rainfall moisture inputs in the Knersvlakte: Methodology and preliminary findings</b>]]> Dew, fog/mist and water vapour adsorption, the 3 vectors by which non-rainfall water can be added to soil water, may play a critical role in ecosystem function in arid zones. This paper explores a methodology for overcoming the challenges of measuring small daily inputs of non-rainfall water in the harsh environment of the Knersvlakte on the West Coast of South Africa. An automatic micro-lysimeter (MLS) - an experimental arrangement of a sensitive electro-mechanical load cell, suitable electronic amplification and signal conditioning, and a microcontroller was developed. A microcomputer was employed for overall system control and data logging. Initial field work took place between late September and November 2006 on Arizona Farm, 30 km north of Vanrhynsdorp. In March 2007, subsequent work began at the Ratelgat BIOTA observatory. Manual soil weight sampling corresponded well with theoretical dew maximums, with measured maximum and minimum dew/fog of 0.4 mm and 0.08 mm (±0.08 mm) (both in September 2006). Measurements from the first prototype MLS were marred by large (± 0.24 mm) error figures, signal dropout from the analog to digital converter, and insufficient range at the required resolution. The subsequent prototype (field tested in March 2007 and still in use) provides much smaller errors (± 0.05 mm). Calibration testing at Ratelgat indicates maximum overnight dew/fog contributions of 0.35 mm (±0.05 mm), which corresponds with theoretical calculations as well as field measurements in other arid zones. Maximum dew/fog derived soil water occurs between 07:00 and 09:15. Surprisingly, soil weight, as a consequence of dew/fog inputs, starts to increase shortly after 17:20. These are preliminary findings and longer term testing and validation are ongoing at present. The role of quartz pebbles and small succulent plants in the interception of non-rainfall water is still to be explored. <![CDATA[<b>Utility of EC 3M</b><b>™</b><b> Petrifilm</b><b>™</b><b> and sanitary surveys for source water assessment in Nyabushozi County, south-western Uganda</b>]]> The majority of people in developing nations rely on untreated or minimally treated surface and shallow groundwater sources which are prone to faecal contamination. This study evaluated the utility of EC 3M™ Petrifilm™ and sanitary inspection forms (SIFs) as tools to assess 47 water sources and identify hazards of contamination in two rural Ugandan villages (90% were surface sources). Water samples were cultured on EC 3M™ Petrifilm™, which are intended for the enumeration of E. coli and total coliforms following 24 h incubation at 37°C. Isolated bacteria were cultured on MacConkey agar and identified using standard biochemical tests, while selected isolates were verified by sequencing 16S rRNA genes. From 105 Petrifilms, 110 presumptive E. coli were isolated and identified to genus level. However, only 33 presumptive E. coli isolates from 14 water sources (representing 27 distinct strains as determined by PFGE) were confirmed E. coli. The other presumptive E. coli isolates were identified as Citrobacter, Enterobacter, Proteus, Salmonella and Yersinia species. SIFs used an adapted survey designed for urban water sources of Uganda. The form yielded an SIF score based on binary data and characterized potential sources of contamination. SIF scores alone offered little information to distinguish between contamination levels of surface water sources, but the information collected in the surveys could be used to identify ways to improve sources. The results of this study suggest that the use of sanitary surveys may assist in identifying potential pollution sources that may be targeted to protect water sources. Bacterial monitoring using EC 3M™ Petrifilms™ may be effective for the screening of relative levels of contamination of source waters, including surface sources. <![CDATA[<b>Evaluation of an integrated asset life-cycle management (ALCM) model and assessment of practices in the water utility sector</b>]]> The water utility sector in South Africa is presently facing numerous challenges. Amongst the most urgent and important priorities is ageing infrastructure, which has the potential to end in failures with detrimental impacts on local communities and the natural environment. Furthermore, to manage the majority of strategic assets in terms of total performance, i.e. environmental, financial, social and technical, is often difficult as a large portion of assets, such as buried pipelines, cannot be easily accessed. These issues highlight the need for a generic asset life-cycle management model for the water utility sector. Such an integrated model is introduced; it was evaluated in the largest water utility in South Africa. Although it was found to have relevance, practicability, applicability, and usability, the model still needs rigorous testing amongst other water utilities in South Africa, and in other countries. The perceptions of the water utility sector were also assessed in terms of the practices of the principles of integrated life-cycle asset management. The results indicate a fairly good understanding of the concept of asset life-cycle management, but allude to challenges with fully implementing all the principles when it comes to asset performance measurements; particular attention must be given to develop mechanisms to measure environmental and social aspects. Nevertheless, it is highlighted that for strategic assets, the practices and principles of ALCM have many benefits, including better maintenance management, infrastructural planning, risk management, and sustainable development.