Scielo RSS <![CDATA[Water SA]]> vol. 39 num. 2 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Comparison of neutron scattering and DFM capacitance instruments in measuring soil water evaporation</b>]]> Soil water evaporation is an important parameter that needs to be accurately measured for the design of water-efficient agricultural systems. With this study, the abilities of the DFM capacitance probes and a neutron water meter (NWM) to measure evaporation from the soil surface were compared. Measured evaporation was compared to the control values measured with mini-lysimeters. Calibration of DFM capacitance probes and the NWM was done in the laboratory using the topsoil of a Bainsvlei soil form. Field measurements of soil water content were done on the same Bainsvlei soil. Calibration results indicated a good correspondence (r² = 0.99) between the measured values and known volumetric soil water contents. There was no significant difference (p = 95%) between the DFM evaporation measurements and the control, whereas the NWM and control differed significantly. It was concluded that the DFM capacitance probe is a better tool than the NWM in measuring evaporation from the topsoil surface. <![CDATA[<b>Growth, phenological and yield responses of a bambara groundnut <i>(Vigna subterránea</i> L. Verdc) landrace to imposed water stress</b>: <b>II. Rain shelter conditions</b>]]> Bambara groundnut is a protein-rich legume, with food-security potential. Effects of irrigation levels and seed coat colour on growth, development, yield and water-use efficiency of local bambara groundnut landrace selections were evaluated under a rain shelter. Emergence was slow, although variation was indicated between landraces. Limited water availability was shown to lower stomatal conductance, although chlorophyll content index was shown to be unaffected. Additionally, growth indices of plant height, leaf number and leaf area index were shown to be lower in response to decreasing water availability. Furthermore, landraces generally flowered and matured earlier while also demonstrating higher water-use efficiency at lower water availability. Seed yield was lower under limited water availability resulting from lower pod mass and pod number. Drought tolerance in bambara groundnut landraces was achieved by reduced canopy size, early flowering and maturity, and maintaining high water use efficiency under stress. 'Brown' and 'Red' landraces responded to water stress better than the 'Light-brown' landrace, suggesting an effect of seed colour on possible drought tolerance. <![CDATA[<b>Salinity of irrigation water in the Philippi farming area of the Cape Flats, Cape Town, South Africa</b>]]> This paper explores the nature, source and spatial variation of the salinity of water used for irrigation in a coastal urban farming area in Cape Town, South Africa, where water from the Cape Flats aquifer is drawn into storage ponds and used for crop irrigation. Water samples were collected in summer and winter from selected sites across the study area and were analysed for salinity as well as for concentrations of major and minor ions. Each site consists of one borehole and one pond. Isotope analysis was done for the summer samples so as to assess effects of evaporation on water quality and salinity. Descriptive statistics were used to compare the variation in range of concentration of specific ions with the recommended ranges set by the South African Department of Water Affairs and Forestry (DWAF) and the Food and Agriculture Organisation (FAO). Geographical information system (GIS) analysis was used to describe the spatial distribution of salinity across the study area, and hydro-geochemical analysis was used to assess the possibility of seawater intrusion into the aquifer system and to characterise groundwater in the study area. The results of the research showed that the concentrations of chloride, nitrate, potassium and sodium exceeded the target maximum limit according to DWAF and FAO guidelines. Groundwater and pond water were also observed to be brackish in most parts of the research area in terms of total dissolved salts content, and fresh water was only found in the middle section of the research area. It is concluded that the accumulation of salts in groundwater and soil in the study area is mainly due to the agricultural activities and partially due to the natural movement of water through the geological formation of the Cape Flats region. These findings permit the formulation of a conceptual model of the occurrence of the salinization process, which implies that the groundwater and pond water in the study area are generally suitable for irrigation purposes, but need to be used with caution as the vegetables grown are classified as sensitive and moderately sensitive to salt according to DWAF guidelines for irrigation water quality (1996). The research paves a way for possible quantitative simulation of salt mass balance in future. <![CDATA[<b>Predicted impacts of land use change on groundwater recharge of the upper Berg catchment, South Africa</b>]]> Land use change is a major factor influencing catchment hydrology and groundwater resources. In South Africa, the management of scarce water resources is a big concern. The study area, the upper Berg catchment, Western Cape, South Africa, contains strategic water resources. The catchment has undergone many changes in recent years, not least of all the construction of a dam on the upper reach. To reduce water loss due to evapotranspiration, non-native hill slope vegetation upstream of the Berg River Dam was cut down. It was hypothesised that recharge has been increased due to this change in vegetation. The objectives of this study were to determine land use changes in upper Berg catchment using multi-temporal Landsat images from 1984, 1992, 2002, and 2008, and to predict the impact of these land use changes on groundwater recharge. For the simulation of groundwater recharge the distributed hydrological model WetSpa was used. Forest plantations lost 72% (18.8 km²) of their areal extent between 1984 and 2008, due to deforestation as part of a plan to implement the ecological Reserve as required by national water policy; the area of barren land increased by 15.7 km² in the same period. The high increase in precipitation, especially in the period of 2005-2009, combined with the change in land use in the study area resulted in a highly increased (278%) predicted mean groundwater recharge. Simulated groundwater recharge shows strong spatial differences for each evaluated year. The effect of the rapid clearing of non-native hill slope vegetation upstream of the Berg River Dam for the land use scenario of 2008 was tested to check if clearing is an important factor in the increase of groundwater recharge. Hence, we simulated the whole time-series from 1984-2004 (21 years) with the land use map from 2008 instead of the land use maps for 1984, 1992 and 2002. A systematic increase of about 8% per year for the 21-year period, due to the change in land use from the different years to that of 2008, is predicted , which confirms that the clearing of the non-native hill slope vegetation is of considerable importance for the increase in groundwater recharge. <![CDATA[<b>Application of the rainfall infiltration breakthrough (RIB) model for groundwater recharge estimation in west coastal South Africa</b>]]> Recharge estimation in arid and semi-arid areas is very challenging. The chloride mass balance method applied in western South Africa fails to provide reliable recharge estimates near coastal areas. A relationship between rainfall events and water level fluctuations (WLF) on a monthly basis was proposed in the rainfall infiltration breakthrough (RIB) model for the purpose of groundwater recharge estimation. In this paper, the physical meaning of parameters in the CRD and previous RIB models is clarified, and the RIB model is reviewed with the algorithm improved to accommodate various time scales, namely, daily, monthly and annual scales. Recharge estimates on a daily and monthly basis using the revised RIB approach in 2 study areas, one in a sandy alluvial aquifer (Riverlands) and the other in the Table Mountain Group (TMG) shallow unconfined aquifer (Oudebosch), are presented, followed by sensitivity analysis. Correlation analysis between rainfall and observed WLF data at daily scale and monthly scale, together with recharge estimates obtained from other methods, demonstrates that the RIB results using monthly data are more realistic than those for daily data, when using long time series. Scenarios using the data from Oudebosch with different rainfall and groundwater abstraction inputs are simulated to explore individual effects on water levels as well as recharge rate estimated on a daily basis. The sensitivity analysis showed that the recharge rate by the RIB model is specifically sensitive to the parameter of specific yield; therefore, the accurate representative specific yield of the aquifer needs to be selected with caution. The RIB model demonstrated in these two cases can be used to estimate groundwater recharge with sufficiently long time series of groundwater level and rainfall available in similar regions. In summary, the RIB model is best suited for shallow unconfined aquifers with relatively lower transmissiv-ity; the utility of the RIB model for application in different climatic areas under different hydrogeological conditions needs to be further explored. <![CDATA[<b>An assessment of the impact of different land use activities on water quality in the upper Olifants River catchment</b>]]> Routine sampling of water quality was conducted at sites along a longitudinal gradient from upstream to downstream in the Olifants River to determine spatial trends in nutrient and metal concentrations and to relate these trends to changes in land use activities in the catchment. In addition, once-off sampling was conducted at a number of sites located downstream of current mining, abandoned mining, agriculture, wastewater treatment works (WWTWs) and industry. Nutrient concentrations were relatively high and a number of sites within the catchment had average N:P ratios that were indicative of eutrophic to hypertrophic conditions. Routine and once-off sampling indicated that wastewater treatment works contribute high nutrient loads to the system. Trend analysis of Department of Water Affairs (DWA) data indicated significant positive trends in ortho-phosphate at 12 of 14 stations in the catchment. An increase in sulphate concentrations from upstream to downstream indicates that mining activities have a progressively greater impact on water quality with increasing distance downstream. While dissolved metal concentrations frequently exceeded chronic and acute effect aquatic ecosystem health guidelines (particularly aluminium, copper and zinc), there was no observable trend from upstream to downstream. Once-off sampling showed high variability in water quality parameters downstream of current mining activities, and some sites showed higher metal concentrations in comparison to other land use activities. However, the contribution of current mining activities to metals is low in comparison to the contribution from abandoned mines. Hydrological data showed that acidic rivers contribute proportionally higher flow volumes in comparison to neutral rivers during the drier winter months, which may significantly impact on the lower stretches of the upper Olifants River and into Loskop Dam. A prolonged drought period will most likely result in severe impacts to the lower reaches of the Olifants River and to Loskop Dam. Improved management and maintenance of wastewater treatment works and rehabilitation and/or treatment of abandoned mines and associated acid mine drainage are crucial. Proper rehabilitation of current mining activities is essential to avoid or minimise acid mine drainage related impacts in the future. <![CDATA[<b>Neutralisation treatment of AMD at affordable cost</b>]]> Acid mine drainage (AMD) has for many years been a major environmental challenge associated with the mining industry, especially in the Eastern, Central and Western mining basins of Gauteng. The aims of this article are to: (i) demonstrate the suitability of the sequencing batch reactor (SBR) system for both neutralisation of free acid and removal of iron(II), often the main component in AMD, using limestone, the cheapest alkali, followed by lime treatment for removal of heavy metals, and partial sulphate removal through gypsum crystallisation; (ii) compare the alkali cost of the alternative SBR system where limestone and lime are used for treatment, with conventional lime treatment, and (iii) present the capital cost of the SBR system. The conclusions of this study are that: (i) precipitated calcium carbonate can be used for complete removal of iron(II) in an SBR system within 90 min reaction time; (ii) lime can be used for complete removal of heavy metals after pre-treatment with precipitated calcium carbonate; (iii) the alkali cost for treatment of AMD from the Western Basin will amount to R2.80/m³ in the case of limestone/lime treatment compared to R5.83/m³ if only lime is used; (iv) the alkali cost for treatment of 85 Mℓ/d acid mine water from both the Western and Central Basins will amount to R60 m./a in the case of limestone/lime treatment compared to R136.9 m./a if only lime is used; and (v) the capital cost for the SBR system amounts to R3.5 m. per Mℓ/d. <![CDATA[<b>Assessment of locally available reactive materials for use in permeable reactive barriers (PRBs) in remediating acid mine drainage</b>]]> The management and treatment of contaminated mine water is one of the most urgent problems facing the South African mining industry. The cost advantage of permeable reactive barriers (PRBs) has seen their increased application as means of passively treating mine drainage. A PRB is built by placing a reactive material in the path of polluted groundwater. As the contaminant moves through the material, reactions occur that transform it into an environmentally acceptable form. Batch tests were carried out on limestone, dolomite, fly ash, concrete and wood chips to find a reactive material and/or reactive mixture, for use in a PRB, which can neutralise acidity, remove metals and is locally abundant. Batch tests involved the leaching of the materials in deionised water to determine the leachable component of each reactive material and the pH that each material could achieve in deionised water. The materials were also tested in acidic water (pH 5.54) to determine the effectiveness of each reactive material in removing contaminants. In terms of the ability to increase the pH, the top-performing reactive materials were limestone and fly ash as they both achieved a pH above 11. Limestone, concrete, fly ash and dolomite successfully removed at least 99% of the iron (Fe) from the mine water. Limestone and fly ash removed at least 99% of manganese (Mn) and magnesium (Mg) from the mine water. While the other reactive materials were ineffective in removing sulphate (SO4(2-)), limestone and fly ash, respectively, removed 72% and 99.9 % of SO4(2-) from the mine water. The study of 3 reactive material mixtures, namely: (i) limestone-wood chips-concrete, (ii) limestone-fly ash, and (iii) fly ash-concrete, showed that all 3 systems were effective in removing heavy metals present in the mine water. All of the mixtures increased the pH to above 11, increased the alkalinity and decreased Fe, Mn, and Mg concentrations to below the prevailing South African discharge criteria of wastewater into a water resource. Reactive Mixtures 2 and 3 successfully removed 99% of SO4(2-) within 14 days. This study found that the most suitable reactive material for remediating acid mine groundwater was fly ash because it was able to neutralise acidity and remove Fe, Mn, and Mg and SO4(2-). <![CDATA[<b>Functionalisation of cross-linked polyethylenimine for the removal of As from mining wastewater</b>]]> Cross-linked polyethylenimine (CPEI) was phosphonated by reaction with phosphorous acid and formaldehyde. The functionalised polymer was used as an adsorbent for the removal of arsenic as an oxo-anion. The binding affinity of the synthesised polymer to abstract As from synthetic solutions and wastewater samples was assessed, as well as its ability to be regenerated for re-use. The PCPEI demonstrated an elevated loading capacity, removing up to 88% of As. The kinetic rates were modelled using pseudo first-order and pseudo second-order equations. The pseudo second-order equation was found to explain the adsorption kinetics most effectively, implying chemisorption. The Langmuir and Freundlich isotherms were used to interpret the adsorption of As onto PCPEI. The Freundlich isotherm was found to best fit and describe the experimental data. The thermodynamic study of the adsorption process indicated high activation energies (55.91 kJ mol-1) which confirms chemisorption as a mechanism of interaction between As and PCPEI. <![CDATA[<b>Sources of manganese in the residue from a water treatment plant</b>]]> Disposal of water treatment residue (WTR), the by-product from the production of potable water, has traditionally been to landfill. The shortage of suitable landfill sites has led to the proposal that WTR be applied to land. Such disposal is only possible if the WTR contains no toxic elements that may contaminate soil, water or vegetation. Previous studies have shown that most WTRs in South Africa contain a high concentration of Mn, which was assumed to be from the drinking water treatment chemicals. This study investigated this assumption at one water treatment plant (WTP) in KwaZulu-Natal. Chemical analysis of drinking water treatment chemicals and a mass balance for Mn at the WTP showed that the main source of Mn was brown lime (added during the treatment process), although the raw water also added appreciable amounts of Mn to the WTR due to the volume of water treated. The concentration of Mn in the organic polymers, bentonite, ferric chloride, ferric sulphate and alum was negligible or very low. It is unlikely that the cost increase associated with changing from brown lime to white lime could be justified, given that the environmental impact of Mn is unclear and is generally not considered to be a problem internationally. Different ecosystems will respond differently to Mn loading and deriving a single, national, maximum permissible level for Mn within a WTR to permit land application is thus difficult and inappropriate. <![CDATA[<b><i>Arthrospira</i></b><b> (Spirulina) in tannery wastewaters Part 1</b>: <b>The microbial ecology of tannery waste stabilisation ponds and the management of noxious odour emissions using microalgal capping</b>]]> We investigated the problem of noxious gas and odour emissions in zero-discharge evaporative tannery waste stabilisation ponds. These have been little-studied systems although they present one of few options for the management of tannery wastewaters in highly water-stressed areas. A three-year study of the microbial ecology of an evaporative waste stabilisation ponding cascade was undertaken and a descriptive account of the biology and the physico-chemical parameters related to odiferous gas release is reported. Large populations of Arthrospira (Spirulina) dominated the latter facultative ponds in the cascade where odour emission was substantially reduced compared to initial anaerobic ponds. Photosynthetic productivity maxima of up to 9 000 mg-m-2-day-1 carbon fixation were measured in bloom conditions. Arthrospira production was associated with an oxygenated, alkaline layer established on the surface of facultative ponds (0.35 m in depth) in which oxidation of sulphide and ammonia, and the trapping of other odour-causing compounds was observed. An attempt was made to achieve comparable odour control in the anaerobic ponds by capping with recirculated microalgae-enriched effluent from facultative ponds. While this was shown to be effective in establishing an Arthrospira-dominant surface layer and an associated control of odour emissions in anaerobic ponds, large recirculation volumes (2:1) were required to maintain the Arthrospira population. Elevated salinity of recirculated facultative pond waters also negatively impacted the evaporative function in the low-salinity initial ponds in the cascade. An alternative method of Arthrospira capping was investigated which involved the construction of a free-standing high rate pond alongside the waste stabilisation pond system, and using a controlled feed of raw tannery effluent for optimising the cultivation of Arthrospira biomass. High biomass productivity was achieved in this unit (12.87 g-m-2-day-1), using a low feed to effluent loading volume ratio (0.21:1) and subsequent capping of anaerobic ponds from this source achieved odour control comparable to facultative ponds. This study has shown that management of the odour problem in waste stabilisation ponds is possible and that leather production using the zero-discharge evaporative disposal operation may be compatible with a level of both environmental and social acceptability of these systems. Odour problems, alone, should thus not constrain tanning as one of the few industrial agricultural activities available in rural economies. <![CDATA[<b><i>Arthrospira</i></b><b> (Spirulina) in tannery wastewaters. Part 2</b>: <b>Evaluation of tannery wastewater as production media for the mass culture of <i>Arthrospira</i> biomass</b>]]> Mass blooms of Arthrospira (Spirulina) have been reported in waste stabilisation ponds treating tannery wastewaters and have been linked to a reduction in odour emissions in these systems. However, these blooms are unstable and unreliable, forming and disappearing in an apparently unpredictable manner, and they have remained poorly understood. Controlled production of Arthrospira biomass in this medium could not only be used to enable a more predictable control of odour in these systems (as detailed in Part 1 of this report), but could also provide a biomass product with external value. Techno-economic studies of microalgal biomass production have identified the cost of growth media formulation as a critical driver in the profitability of the algal biotechnology enterprise. Apart from the potential feed value of Arthrospira biomass as a product, the renewed interest in, and possibly marginal economics of, biofuels production from the microalgae has refocused attention on the possible advantages of wastewater use as low-cost production media. Part 2 of this study reports the investigation of factors regulating Arthrospira growth in the tannery wastewater medium and thus requiring active control in order to optimise biomass production. It was shown that Arthrospira growth in this high-protein, low-carbonate medium is under ammonia control, rather than nutrient limitation, as may previously have been thought. It was also shown that an effective mass culture strategy in this medium would require a maximum effluent loading rate that operates as a function of the optimised ammonia removal rate. Growth optima were demonstrated for ammonia and bicarbonate levels of 20 mg-ℓ-1 and 12-17 g-ℓ-1, respectively, and inhibition of growth was demonstrated at ammonia levels above 60 mg-ℓ-1. Both autotrophic and mixotrophic growth of Arthrospira was observed and organic uptake may contribute to a stimulation of biomass production compared to growth in defined inorganic media. Heavy metal accumulation may present a toxicity hazard where biomass is targeted for use in animal feed rations. A heavy metals removal step was investigated involving the passage of the tannery effluent through an anaerobic sulphide-generating compartment in a primary pond, prior to its use in Arthrospira production. An acceptable Arthrospira feed-grade biomass was produced in this way. These results indicate potential cost-benefit advantages in the use of tannery effluent-based growth media for Arthrospira biomass production, and waste nutrient recovery may mitigate negative energy yield problems where the bio-mass is further processed in biofuels manufacture. <![CDATA[<b>Sustainable nitrification in fluidised bed reactor with immobilised sludge pellets</b>]]> Sustainable immobilised microbial pellets were developed with water-borne polyurethane (WPU) material together with powdered activated carbon (PAC) and activated sludge as microbial inoculums for nitrification or partial nitrification. The nitrification performance and the influencing factors were studied with lab-scale aerobic fluidised bed reactors (FBR) under various temperature conditions. During the start-up period, quickly increasing the influent ammonium concentration from 40 to 320 mg N-ℓ-1 led to a stable nitrification performance with high nitrite accumulation (>80%). Characterisation of the FBR performance indicated that the desired partial nitrification could be achieved at pH 7.8-8.5, dissolved oxygen (DO) 3-5 mg-ℓ-1 and temperature between 24 and 29°C. Addition of organic carbon (glucose) improved the ammonium removal but decreased the nitrite accumulation ratio significantly. TOC concentration above 800 mg-ℓ-1 was not able to cause the inhibition of the heterotrophs over the nitrifiers. PCR-DGGE results indicated the presence of Nitrosomonas (ammonia-oxidising bacteria) and Nitrobacter (nitrite-oxidising bacteria) in the immobilised pellets. <![CDATA[<b>Real-time PCR quantitative assessment of hepatitis A virus, rotaviruses and enteroviruses in the Tyume River located in the Eastern Cape Province, South Africa</b>]]> We applied real-time RT-PCR (reverse transcription-polymerase chain reaction) to assess the incidence of hepatitis A virus, rotaviruses and enteroviruses in the Tyume River, an important water resource in the impoverished Eastern Cape Province of South Africa. Detection of noroviruses was done using conventional semi-nested RT-PCR. Water samples were collected once monthly from 6 sampling sites over a 12-month period starting in August 2010 and ending in July 2011. Hepatitis A virus was detected in 13% of the samples in concentrations ranging between 1.67x10³ genome copies/ℓ and 1.64x10(4) genome copies/ℓ while rotaviruses were detected in 4% of the samples with concentrations ranging from 9x10' genome copies/l to 5.64X10³ genome copies/ℓ. Enteroviruses were not detected in any of the samples, while noroviruses were detected in 4% of the samples. All hepatitis A and rotaviruses positive samples were from the upstream sections of Tyume River while noroviruses were detected in samples from downstream sections only. Statistical analysis showed that occurrence of the viruses in Tyume River was sporadic. Risk analysis showed that hepatitis A virus posed greater risk than rotaviruses for both recreational and domestic water uses. Because of the low infectious dose of enteric viruses, the detection of even low concentrations of hepatitis A virus, rotaviruses and noroviruses in surface water poses a significant risk to public health. <![CDATA[<b>User perceptions of urine diversion dehydration toilets</b>: <b>Experiences from a cross-sectional study in eThekwini Municipality</b>]]> The current environmental challenges that most middle- and low-income countries have been experiencing has led to new environmentally sustainable and economically viable sanitation solutions, such as waterless systems with source separation of human waste. We conducted a cross-sectional study in eThekwini municipality to explore the post-implementation challenges of urine diversion dehydration toilets (UDDTs) after a decade of installation and the adaptive processes necessary to increase the sustained use of the toilets. A structured questionnaire was administered to 17 499 households in 65 rural and per-urban areas of eThekwini using mobile phone technology. Results report low levels of satisfaction with the facilities as well as an association between perceived smell in the toilets and malfunctioning of the pedestal, and low use of UDDTs when a pit latrine is present in the dwelling perimeter. Conclusions relate to the importance of educational and promotional activities that stress the economic return derived from reusing urine and excreta in agricultural activities. <![CDATA[<b>Funding models for financing water infrastructure in South Africa: Framework and critical analysis of alternatives</b>]]> The Government of South Africa has been the main provider of public infrastructure, particularly in the water sector. Government administration and institutional structures continue to shape and influence infrastructure investment. The South African constitutional system imposes unique complexities and constraints on infrastructure investment. The country experiences a serious backlog in water infrastructure investment for the development and management of water resources and water services. In 2011, this under-investment was estimated at more than R600 billion (600 x 10(9) ZAR: South African Rand). The national Government traditionally had a pivotal role in shaping water infrastructure investment. Government needs to find a solution to this backlog by putting in place new institutional structures and funding models for effective strategies leading to prompt water infrastructure provision. The research identified several funding models for financing water infrastructure development projects. The existing public provision model continues to characterise much of the publicly-provided water infrastructure in South Africa. These models see Government planning, installing and financing infrastructure with pricing at marginal costs or on a loss-making basis, with returns recovered through the taxation system. Nowadays, water infrastructure provision is split between fully-public and mixed ownership by water entities. Public-private partnerships (PPPs) in the water sector are not yet a reality. <![CDATA[<b>A comparative study of marriage in honey bees optimisation (MBO) algorithm in multi-reservoir system optimisation</b>]]> Contemporary reservoir systems often require operators to meet a variety of goals and objectives; these in turn frequently complicate water management decision-making. In addition, many reservoir objectives have non-linear relationships and are therefore difficult to implement using traditional optimisation techniques. A practical application of the marriage in honey bees optimisation (MBO) algorithm is being utilised for Karkheh multi-reservoir system, south-western Iran, where supplying irrigation water for agricultural areas and maintaining a minimum in-stream flow for environmental purposes is desired. Optimal monthly reservoir release information by MBO is highlighted and the results compared to those of other evolutionary algorithms, such as the genetic algorithm (GA), ant colony optimisation for continuous domains (ACO R) particle swarm optimisation (PSO) and elitist-mutation particle swarm optimisation (EMPSO). The results indicate the superiority of MBO over the algorithms tested. <![CDATA[<b>An inorganic water chemistry dataset (1972-2011) of rivers, dams and lakes in South Africa</b>]]> A national dataset of inorganic chemical data of surface waters (rivers, lakes, and dams) in South Africa is presented and made freely available. The dataset comprises more than 500 000 complete water analyses from 1972 up to 2011, collected from more than 2 000 sample monitoring stations in South Africa. The dataset includes the major ion chemical composition and numerous calculated variables that can, amongst others, be used to determine accuracy of the analysis. The methods described here have potential for improving quality control measures in water chemistry laboratories by detecting anomalous samples. The processed data are available in Excel spreadsheets and can be downloaded from the website of the Centre for Water Science and Management based at the North-West University (