Scielo RSS <![CDATA[Water SA]]> vol. 35 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>How to manage the cumulative flood safety of catchment dams</b>]]> Dam safety is a significant issue being taken seriously worldwide. However, in Australia, although much attention is being devoted to the medium- to large-scale dams, minimal attention is being paid to the serious potential problems associated with smaller dams, particularly the potential cumulative safety threats they pose in catchments. This paper establishes the significance of this problem and reviews various Australian policies, including consideration of evidence from past research, to identify the potentially more effective policies with respect to smaller dams/cumulative safety assurance. New 'case studies' research that recently tested the effectiveness and coverage of the "strong" dam-safety policy of New South Wales (NSW) is then reported. The case studies comprised 2 samples of 10 hazardous private reservoirs investigated for spillway adequacy in line with state-of-the-art practice: one sample comprised dams supervised under the NSW policy, while the other sample comprised only non-supervised dams. The case studies show the potential effectiveness of strong policy, but also the importance of registering all dams and the need for some form of supervision of even small dams due to either their individual or cumulative hazard potential. The State of Tasmania provides a 'model' on how this can be best achieved in line with international best-practice, and this recently became the focus of a comprehensive study. This study involved strategic consideration and assessment of policy responses to the varying issues associated with small-dam safety and practical feedback from key policy actors. The results of this study are also reported here to provide guidance to any other jurisdiction world-wide needing to manage numerous small dams posing cumulative safety threats in catchments. <![CDATA[<b>Inactivation of high concentration of pathogens in land-applied food industry sludge</b>]]> In Mexico, as in other developing countries, the most important pollution and management problems of food-processing sludge are the high levels of pathogen microorganisms within the sludge and the lack of sites for its disposal. The aims of this study were to evaluate the effect of calcium oxide in the inactivation of pathogenic microorganisms and the subsequent use of the resulting product in an agricultural application at various agronomic rates. Stabilisation tests were done in a hermetically closed fibreglass reactor with 1.5 ℓ capacity, using physicochemical sludge with concentrations of 4, 8 and 12% of total solids (TS) and contact times of 30, 60 and 90 min. At the end of each treatment, the raw and treated sludge quality was evaluated. Recommended doses for Class A biosolids production were 20, 10 and 8% m/m of CaO for 4, 8 and 12% of TS respectively with a minimum contact time of 90 min. The land-application test was done using sludge with 8% TS treated with a quicklime dose of 10% m/m. Nitrogen-based Agronomic Rates (AR) of 0, 1, 5, 10 and 15 were evaluated in the cultivation and production of chayote (Sechium edule). The results with 5 AR showed an estimated total production of 70 kg of the vegetable species over a period of 90 d, which is higher than that reported for the same crop grown without biosolids application. <![CDATA[<b>Operation and monitoring guidelines and the development of a screening tool for irrigating with coal mine water in Mpumalanga Province, South Africa</b>]]> It is predicted that vast volumes of impacted mine water will be produced by mining activities in the Mpumalanga coalfields of South Africa. Irrigation provides for a novel approach to the utilisation and disposal of mine water, under the correct conditions. The significance of these findings lies in the versatility of this irrigation. Communities which often have very few other resources can utilise mine water to generate livelihoods. Research over a period of more than 10 years has shown that this water can be used successfully for the irrigation of a range of crops. The potential environmental impact of this excess water is of great concern in a water-scarce country like South Africa. There is, however, continuing concern from the local regulators regarding the long-term impact that large-scale mine-water irrigation may have on groundwater quality and quantity. Detailed research has been undertaken over the past number of years on both undisturbed soils and in coal-mining spoils. These sites range from sandy soils to very clayey soils. The results indicate that many of the soils have considerable attenuation capacities and that over the period of irrigation, a large proportion of the salts are contained in the upper portions of the unsaturated zones below each irrigation pivot. The volumes and quality of water leaching through to the aquifers have been quantified at each site. From these data mixing ratios were calculated in order to determine the effect of the irrigation water on the underlying aquifers. One of the outcomes from this study was to define the conditions under which mine-water irrigation can be implemented and the associated operational and monitoring guidelines that should be followed. These have been based on the findings from this study, the fundamental considerations of mine-water irrigation, the regulatory environment and, as far as possible, the practical implementation of mine-water irrigation as part of optimal mine-water management. In an attempt to standardise decision-making regarding mine-water irrigation, the criteria, data, rules and fundamentals discussed have been combined in a user-friendly tool, called GIMI (Groundwater Impacts from Minewater Irrigation). This tool should assist in the practical implementation of mine-water irrigation as part of optimal mine-water management. <![CDATA[<b>Knowledge uptake by technical professionals and decision-makers for developmental water services. Part 1</b>: <b>methodology, knowledge and context</b>]]> While significant knowledge appears to be available on developmental water services (a term for service provision, to meet developmental objectives, with an emphasis on poor communities, in which a range of factors other than purely technical factors are addressed), there appears to be insufficient uptake of this knowledge (meaning the acquisition, comprehension and application in context) by technical professionals and decision-makers responsible for service provision, as evidenced by persistent service delivery backlogs and poor sustainability. This investigation developed and documented an exploratory methodology based primarily on in-depth interviews and a literature review which enabled the collection of evidence and development of a 'first pass' typology of knowledge, context and individual competencies with respect to developmental water services. This paper addresses the aspects of knowledge and context. Individual competencies are addressed in the companion paper (Part 2). With respect to knowledge, the investigation found that while there is a lot of information readily available in the sector on the provision of water services to meet developmental objectives, what appears to be weak or missing is information on how to apply this information in context. With respect to context, the investigation established a simple preliminary framework which described the combination of political and technical disciplines in a unified approach, and the translation of this into the bureaucracy. On the evidence of the in-depth interviews, the contextual aspects of developmental water services, described by the above framework - and, in particular, the workings of the bureaucracy - would appear to constitute the major challenge facing high-level technical professionals and decision-makers in the provision and sustainability of water services. More generally, the investigation established that for effective provision of water services within a developmental context, there is a close relationship between the three components of knowledge, context and individual competencies; and that it is difficult to address any one of the three components without reference to the other two. <![CDATA[<b>Knowledge uptake by technical professionals and decision-makers for developmental water services. Part 2</b>: <b>individual competencies</b>]]> While significant knowledge appears to be available on developmental water services (a term for service provision, to meet developmental objectives, with an emphasis on poor communities, in which a range of factors other than purely technical factors are addressed), there appears to be insufficient uptake of this knowledge (meaning the acquisition, comprehension and application in context) by technical professionals and decision-makers responsible for service provision, as evidenced by persistent service delivery backlogs and poor sustainability. This investigation developed and documented an exploratory methodology based primarily on in-depth interviews and a literature review which enabled the collection of evidence and development of a 'first pass' typology of knowledge, context and individual competencies with respect to developmental water services. This paper addresses individual competencies. The aspects of knowledge and context, as well as the overall methodology, are addressed in the companion paper (Part 1). International literature reports a comprehensive list of competencies required by individuals working in the provision of water services. The interviewees participating in the research corroborated the list of the competencies found in the literature. The key individual competencies were classified as methodical competencies and social competencies or competencies of personage and presented in tabular form. In the South African context numeracy, knowledgeable analysis, adaptation to change and various communication competencies as well as an ability to make sound judgments were considered particularly important and given more significance by the interviewees than ascribed in the international literature. More generally, the investigation established that for effective provision of water services within a developmental context, there is a close relationship between the 3 components of knowledge, context and individual competencies; and that it is difficult to address any one of the 3 components without reference to the other two. <![CDATA[<b>The impact of water scarcity on economic development initiatives</b>]]> South Africa's unallocated water resources have dwindled to precariously low levels. Furthermore, it is generally recognised by the authorities and specialists alike that it is likely that water demand will outstrip water supply within the next decade. Macro-economically and strategically speaking, the question therefore is how to make best use of the country's available water resources? We ask this question since South Africa is a country classified as having chronic water shortages, a condition exacerbated by climate change and the presence of invasive alien plant species. In this paper we address the question of sectoral water allocation by applying a macro-economic comparative static Computable General Equilibrium (CGE) Model using an integrated database comprising South Africa's Social Accounting Matrix (SAM) and sectoral water use balances. We refer to AsgiSA, the South African Government's Accelerated and Shared Growth Initiative for South Africa, and conclude that introducing the proposed programmes in a business-as-usual and water-intensive manner will strengthen the current growth in the demand for water. This will bring forward, or accelerate, the need for introducing water rationing among sectors. The importance of this conclusion cannot be emphasised enough. Water is essential, and recognised in as much in the preamble to the National Water Act of 1998, with regards to livelihoods, health and from a socio-economic development perspective since there are no substitutes for it. While water rationing is imminent, the reality thereof has not yet led to a rethink of macro-economic policies. This delayed effect can create a degree of comfort and ill-founded complacency leading to non-action, whereas there is an urgent need for proactive measures towards water conservation. <![CDATA[<b>Optimal dimensioning model of water distribution systems</b>]]> This study is aimed at developing a pipe-sizing model for a water distribution system. The optimal solution minimises the system's total cost, which comprises the hydraulic network capital cost, plus the capitalised cost of pumping energy. The developed model, called Lenhsnet, may also be used for economical design when expanding existing hydraulic networks. The methodology developed includes an iterative dynamic calculation process as well as a hydraulic simulation model. The performance of the method is tested against 4 benchmark examples in the literature. The results obtained show the feasibility of this model, presenting it as a viable alternative for water distribution systems. The method is easily used, once it is performed under EPANET2 software interface. <![CDATA[<b>Projected future runoff of the Breede River under climate change</b>]]> The Breede River is the largest river in the Western Cape Province of South Africa, and as such, is a key resource for a variety of activities within the region. It is this significance of the river that prompted a study into the impact of climate change on future runoff in the river and hence, the potential impacts a projected change in catchment runoff may have on the future use of the river. Due to the complexities of the catchment only specialised hydrological models can capture the system dynamics of the river adequately. This limitation prompted the use of an alternative approach (self-organising maps (SOMs)) to hydrological modelling and, at the same time, performed an assessment of the appropriateness of this alternative approach for use in such applications. SOMs are a powerful tool in synoptic climatology as they can be used to objectively classify a large number of daily synoptic states into a predetermined number of groups. Each archetypal synoptic pattern is linked to an observed associated runoff in the catchment. With an assessment of the change in frequency of each atmospheric state from control to future comes an assessment of the change in frequency of the associated runoff from control to future. The end result of this is a quantified assessment of the projected change in both high-frequency runoff events and in the projected change in mean annual runoff (MAR) in the catchment from the present to the future under 3 climate models. Not only does this information assist in the process of long-term policy decisions made in relation to water-transfer schemes, but it also allows for an assessment of the future ecological sustainability of the catchment. This is achieved by assessing the projected future level of flow at each runoff gauging station against the current benchmark for ecological sustainability. <![CDATA[<b>Horizontal subsurface flow constructed wetlands for mitigation of ametryn-contaminated water</b>]]> The feasibility of using constructed wetlands (CWs) for the mitigation of pesticide runoff has been studied in the last decade. However, a lack of related data was verified when subsurface flow constructed wetlands (SSF CWs) are considered for this purpose. In the present work, SSF CWs were submitted to continuous ametryn addition and evaluated during an 11-week period, with the aim of determining the feasibility of these systems for mitigation of contaminated water. Ametryn was not added to one CW cell in order to provide a control for the experiments. Monitoring of treatment performance was executed by standard water quality parameters, ametryn chromatography quantification and macrophyte (Typha latifolia L.) nutritional and agronomic property analysis. Results indicated that 39% of the total initially added amount of ametryn was removed, transferred or transformed. Herbicide metabolism and mineralisation were carried out by chemical and biological mechanisms. No statistic differences were observed in nutritional contents found in the T. latifolia crops of the CWs after the experimental period. Moreover, the biomass production (one valuable source of renewable energy) was equal to 3.3 t·ha-1 (dry matter) in wetland cells. It was concluded that constructed wetland systems are capable of mitigating water contaminated with ametryn, acting as buffer filters between the emission sources and the downstream superficial water bodies. <![CDATA[<b>Simulation of a wastewater treatment plant receiving industrial effluents</b>]]> A process model simulating the Mariannridge Wastewater Treatment Plant, located in the eThekwini Municipality, has been developed in the WEST (Worldwide Engine for Simulation, Training and Automation) modelling environment, based on the IWA Activated Sludge Model No. 3 (ASM3). The treatment plant receives a high proportion of industrial effluents. The development of the model involves the characterisation of the influent wastewater and determining model parameters (kinetic and stoichiometric coefficients) by undertaking batch respirometric tests on the wastewater and activated sludge, flocculation filtration and simulation of the batch respirometric experiment. To account for equipment-specific factors, the simulation model was calibrated against plant data covering a year's operation. The model is intended to be used as part of a system to evaluate the ability of a receiving wastewater treatment works to adequately treat a particular industrial effluent before granting a permit for it to be discharged to sewer. <![CDATA[<b>Recent blooms of the dinoflagellate <i>Ceratium</i> in Albert Falls Dam (KZN)</b>: <b>history, causes, spatial features and impacts on a reservoir ecosystem and its zooplankton</b>]]> A lake-wide bloom of the dinoflagellate Ceratium hirundinella, discovered in Albert Falls Dam in October 2006, exposed a significant ecological change indicative of reduced water quality in this historically mesotrophic reservoir. The spatial distribution of the bloom was examined synoptically in October 2006 and January 2007; these surveys revealed generally higher dinoflagellate densities in inshore reaches of the lake, and especially in the discharge plume of the inflowing Mgeni River. Ceratium totally dominated the phytoplankton assemblage, accounting almost completely for coincident chlorophyll levels, which generally increased with depth to generate a 'deep' chlorophyll maximum. Vertical oxygen profiles during the bloom differed substantially from corresponding profiles during non-bloom conditions historically typical in this reservoir. Direct count data and ordination analysis using non-metric multidimensional scaling exposed marked changes in zooplankton community structure compared to seasonally congruent non-bloom conditions in other years. Changes included the effective replacement of Moina by Bosmina, substantial reductions in Daphnia and Ceriodaphnia, and smaller but definite increases in abundance especially of calanoid copepods, as well as cyclopoid copepods and of Chaoborus, although not all of these differences were apparent in both survey months. These compositional changes are attributable to intrinsic differences in feeding biology among taxa and their associated susceptibility to the altered food environment, which was commensurate with Ceratium's emergence. In addition, chydorid cladocerans appeared as a new (but spatially restricted) eutrophic bio-indicator component of the zooplankton, and the species diversity of cyclopoid copepods was enriched. The historical incidence of Ceratium in the lake since 1995 coincided with low NO3-N:TP values (used here as an N:P ratio proxy), particularly of inflow waters, and with broadly coincident values in the open lake. Ceratium was present but sparse in 1995, at average N:P ratios around 5.5. It disappeared in 1996 when the ratio increased radically to >10, and reappeared in 2004 after an erratic decline of the ratio to < 5 in the lake. The decline in N:P ratio of inflow waters since 1996 was clearly associated with a consistent rise in TP levels in inflows, most plausibly attributable to inputs of (Howick) wastewater treatment (WWT) plant origin. The appearance of Ceratium blooms is accordingly related to progressive elevations in mean annual P concentrations in inflows from ~40 mg/ℓ in 1995 to 120 µg/ℓ in 2007 (broadly mirrored in annual TP loadings), suggesting that improved operational efficiency (and capacity) of the WWT plant offers a plausible prospect for mitigation and reversal. <![CDATA[<b>Comparison of microbial contamination at various sites along the Plankenburg</b>: <b>and Diep Rivers, Western Cape , South Africa</b>]]> This study was aimed at investigating and comparing the microbial contamination levels at various sites in the Plankenburg and Diep Rivers in the Western Cape, South Africa. Sampling of sites along the Plankenburg River started in June 2004 and continued for a period of 1 year until June 2005. Sampling of the Diep River sites started in March 2005 and continued for a period of 9 months until November 2005. Faecal coliform (FC) and E. coli (EC) counts were determined by means of the most probable number (MPN) technique, the number of culturable cells were determined using the heterotrophic plate count (HPC) technique and total microbial counts were evaluated by Flow cytometric analysis (FCM). The highest microbial counts for the Plankenburg River were observed at Site B where the highest MPN, FC, E. coli and total FCM counts of 9.2 x 10(6) (Week 14), 3.5 x 10(6) (Week 39) and 3.5 x 10(6) micro-organisms/100 mℓ (Week 39) and 2.1 x 10(8) micro-organisms/mℓ (Weeks 1 and 39) respectively, were recorded. The highest HPC recorded for the Plankenburg River was 7.9 x 10(6) micro-organisms/100 mℓ (Week 44, Site A). Site B is situated close to an informal settlement where waste effluents from stormwater drainage pipes enter the river system. In addition, other possible contamination sources included agricultural (Site A) and industrial (Site C) areas bordering the Plankenburg River. The highest total MPN, FC and E. coli counts in the Diep River were 5.4 x 10(6) (Week 23) and 1.6 x 10(6) micro-organisms/100 mℓ (FC and E. coli, respectively (both in Week 23)), recorded at Site B. The highest HPC and total FCM counts of 1.7 x 10(7) micro-organisms/100 mℓ (Week 14) and 2.5 x 10(9) micro-organisms/mℓ (Week 23), respectively, were also recorded at Site B. This site was identified as the most contaminated site along the Diep River and served as an accumulation point for waste effluents from the residential and industrial areas, which included paint and machine manufacturers. Other sources situated along the Diep River included storage and maintenance facilities for steel containers, a wastewater treatment plant and an oil-refinery. Most of the bacterial counts obtained for the Plankenburg and Diep Rivers exceeded the accepted maximum limit for river water for most of the sampling period. <![CDATA[<b>An overview of cyanobacterial research and management in South Africa post-2000</b>]]> The quality of South Africa's water resources is becoming increasingly impaired by eutrophication, to the extent that regional crises now prevail. Thirty-five percent of the total storage is eutrophic to hypertrophic - including grossly-enriched reservoirs that far exceed the globally-accepted definition of hypertrophy. Failing infrastructure contributes to the problem of polluted urban runoff which comprises a significant fraction of flows to inland reservoirs, particularly in the landlocked, economic heartland of the country. In the period post-2000, a number of developments have underpinned the provision of a research and management infrastructure that ensures that South African water resource management structures are capable of dealing with cyanobacterial problems. This paper details the progress and achievements that have been made during this period. <![CDATA[<b>Survey of disinfection efficiency of small drinking water treatment plants</b>: <b>challenges facing small water treatment plants in South Africa</b>]]> A survey involving 181 water treatment plants across 7 provinces of South Africa: Mpumalanga, Limpopo, North West, Free State, KwaZulu-Natal, Eastern Cape and Western Cape was undertaken to identify the challenges facing small water treatment plants (SWTPs) in South Africa . Information gathered included ownership and design capacity of the plants, water sources, and various methods of disinfection, equipment currently employed and performance of the treatment plants. In general, the majority (over 80%) of the SWTPs surveyed in the designated provinces were owned by the district municipalities. The designed capacities of these plants varied between 1 and 60 Mℓ/d; the smallest capacity was 100 m³/d and the largest 120 Mℓ/d. The small water treatment plants abstracted their raw water from either surface or groundwater or a combination of both water sources with greater preponderance for surface water sources (over 86%). Water treatment practices were noted to be the conventional types mainly coagulation, flocculation, sedimentation, filtration and disinfection. Two types of coagulants namely polyelectrolyte (66%) and alum (18%) were commonly used by the water treatment plants across the provinces studied. Rapid gravity filtration, pressure filter and slow sand filtration systems accounted for 60%, 23% and 9% of the filtration systems across the provinces, respectively. The predominant types of disinfectants employed were chlorine gas (69%) followed by sodium (15%) and calcium (14%) hypochlorite. Over 50% of the various SWTPs did not comply with the SANS 241 Class I (< 1 NTU) and Class II (1 to 5 NTU) recommended turbidity values. The recommended target range of 0.3 to 0.6 mg/ℓ free chlorine residual concentrations at the point of use was not always met by 40% of the plants. Seventy percent of the SWTPs complied with the SANS 241 criteria of microbiological safety of drinking water vis-à-vis total and faecal coliforms. Operational problems affecting the efficiency of small water treatment plants included: inability to appropriately determine the flow rate, chemical dosage and turbidity, lack of chlorine residual at the point of use and lack of water quality monitoring. To produce safe drinking water, appropriate operational practices must be implemented in all small water treatment plants. <![CDATA[<b>Heterotrophic plate count vs. <i>in situ </i>bacterial 16S rRNA gene amplicon profiles from drinking water reveal completely different communities with distinct spatial and temporal allocations in a distribution net</b>]]> Heterotrophic plate count using ISO 6222 agar (HPC) vs. in situ bacterial (DF) community structure from corresponding samples of a drinking water distribution system were investigated by 16S rRNA gene-based polymerase chain reaction denaturing gradient gel electrophoresis (PCR DGGE) profiling. The investigation regime covered 10 different sampling locations and 2 points in time (t1, t2). In order to ensure accurate and reproducible 16S rRNA gene profile analysis, rigorous methodical evaluation and standardisation procedures were undertaken (DGGE optimisation, replication of PCR, multiple-lane standardisation, representative sampling volume determination, application of multiple similarity coefficients). The reproducibility level of the profile analysis was determined to be > 90% similarity. Two completely different communities were revealed from HPC vs. DF as indicated by DGGE analysis and sequencing. HPC populations could be identified as ubiquitously occurring cultivable copiotrophic microbes, whilst most DF sequences could be allocated to sequences from microorganisms found in oligotrophic aquatic environments. Spatial- and temporal-based 16S rRNA gene amplicon profile analysis from recovered communities further revealed contrasting results. As proven by Jackknife simulations, DF profiles remarkably corresponded to sampling time, whereas HPC profiles revealed spatial associations within the distribution system. Recovered data demonstrate that cultivation based HPC vs. direct cell-based investigations can result in completely different results if used for monitoring purposes in distribution systems. <![CDATA[<b>Evaluation of the CDC safe water-storage intervention to improve the microbiological quality of point-of-use drinking water in rural communities in South Africa</b>]]> The use of different concentrations of sodium hypochlorite solutions (placebo; 1% and 3.5% sodium hypochlorite solutions) and 2 water-storage containers (traditional plastic container and the improved CDC safe water-storage container) as interventions in 2 rural communities using different water sources (improved vs. unimproved) was evaluated over a period of 4 months. Standard methods were used to determine the presence of indicator organisms (total coliforms, faecal coliforms, Escherichia coli, faecal enterococci, Clostridium perfringens, male-specific F-RNA and somatic coliphages) in the water samples. The results indicated that the 1% and the 3.5% sodium hypochlorite solutions effectively reduced the numbers of indicator microorganisms to undetectable counts in both types of water-storage containers. However, no statistical differences were seen between the 2 types of water-storage containers in the numbers of indicator microorganisms present in the stored water with the addition of a placebo sodium hypochlorite solution. Compliance of households with the use of the sodium hypochlorite intervention ranged between 60% and 100%. A household questionnaire survey indicated an urgent need for education concerning the risk of waterborne diseases, the proper use of safe household water-storage devices and water treatment processes and improvement of hygiene and sanitation practices in these rural households. <![CDATA[<b>Fish assemblage patterns as a tool to aid conservation in the Olifants River catchment (East), South Africa</b>]]> South Africa has committed to address freshwater conservation at the catchment scale, using a combination of landscape-level and species-level features as surrogates of freshwater biodiversity. To support this work, we examined fishes in the Olifants River catchment, where multiple anthropogenic pressures affect streams. Patterns in fish assemblage data across 88 sites were analysed and related to landscape environmental variables using statistical techniques of multivariate ordination, cluster analysis, and regression tree analysis. We identified 6 distinct fish assemblage types, which were separated by altitude and human influence, primarily dry-land cropping and dams. In the upper reaches of the catchment, we identified a faunal shift from Barbus neefi, which occurred in less impacted sites, to B. anoplus and Tilapia sparrmanii, which were favored in cropland and mixed cropland/urban settings, respectively. The fish assemblage of the middle section of the catchment was not unique, but supported one species, Chiloglanis pretoriae, that could be considered a focal species for conservation. The low altitude, high-runoff section of the catchment supported the most species. However, species richness increased in association with dams, through the addition of species that are more tolerant of flow and physicochemical modifications. Thus, species richness may not be an optimal conservation target for this system. Rather, a series of indicators will be necessary to track and measure conservation success in the Olifants catchment.