Scielo RSS <![CDATA[Water SA]]> http://www.scielo.org.za/rss.php?pid=1816-795020120005&lang=pt vol. 38 num. 5 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Using multivariate statistical analysis to assess changes in water chemistry in sections of the Vaal Dam catchment between 1991 and 2008</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500001&lng=pt&nrm=iso&tlng=pt Multivariate statistical analysis was used to investigate changes in water chemistry at 5 river sites in the Vaal Dam catchment, draining the Highveld grasslands. These grasslands receive more than 8 kg sulphur (S) ha-1-year-1 and 6 kg nitrogen (N) ha-1-year-1 via atmospheric deposition. It was hypothesised that between 1991 and 2008 concentrations of dissolved mineral salts, sulphate, nitrate and ammonium would increase as a result of the S and N deposition received. Significant spatial differences were found, by analysis of covariance, between sites within the catchment. Canonical correspondence analysis (CCA) showed that the environmental variables used in the analysis, discharge and month of sampling, explained a small proportion of the total variance in the data set - less than 10% at each site. However, the total data set variance, explained by the 4 hypothetical axes generated by the CCA was >93% for all 5 sites. Sulphate, nitrate-plus-nitrite, ammonium and phosphate concentrations increased at 1 site each, between 1991 and 2008. Over the same time frame, acid-neutralising capacity was decreased significantly at 1 of the 5 river sites. The concentrations of the ions analysed, with rare exception, were within the limits set by the national drinking water guidelines, between 1991 and 2008. Nitrogen and sulphur concentrations at the five selected river sites within the Vaal Dam catchment did not show a statistically significant increase between 1995 and 2008. <![CDATA[<b>The performance of plant species in removing nutrients from stormwater in biofiltration systems in Cape Town</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500002&lng=pt&nrm=iso&tlng=pt In 2009, the City of Cape Town (CoCT) adopted a stormwater policy which mandates that new and existing developments should reduce the concentration of phosphorus and suspended solids in stormwater runoff by 45% and 80%, respectively, but offered no explicit guidance about how these water quality targets might be achieved. This study aims to contribute to the limited knowledge that exists about the performance of local plant species to treat stormwater. A large nursery-based study was conducted to investigate the performance of 9 locally-occurring plant species to remove orthophosphate (PO4³), ammonia (NH3) and nitrate (NO3) found in urban stormwater. Synthetic stormwater was applied to each species as well as a control consisting only of soil (Malmesbury shale). The discharge was collected from a drainage pipe at the base of each of the 150 containers. The results show that all species (excluding Ficinia) reduced the average concentrations of PO4³ by 81% and NH3 by 90%. By contrast, NO3" was reduced by an average of 69% (excluding by Elegia and Phragmites) with 8 of the 9 species removing significantly more than the control. The species that performed well for all three nutrients include Agapanthus and turf grasses, Stenotaphrum and Pennisetum. The results of the study highlight three important factors in the design of biofilters: that a substantial proportion of nutrients can be captured or absorbed by plants; that the soil medium is an important factor in the removal of PO4"³ and NH3; and that plant choice is essential in the removal of NO3-. Future research should test plant species in both the laboratory and field settings, and should include additional contaminants such as household detergents, heavy metals and bacteria. <![CDATA[<b>Seasonal variations of water and sediment quality parameters in endorheic reed pans on the Mpumalanga Highveld</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500003&lng=pt&nrm=iso&tlng=pt The Mpumalanga Lakes District consists of approximately 320 pans, of which less than 3% are classified as reed pans. There is limited information available on reed pans and as a result they are at risk of various anthropogenic activities, for example mining and agriculture. Four reed pans were selected and assessed to determine seasonal trends of a variety of water and sediment quality parameters. The study took place over one seasonal cycle from 2008-2009; samples were collected seasonally to account for various hydrological extremes. Water samples were collected and their nutrient and chlorophyll a concentrations were determined, while various other water quality parameters were measured in situ. Sediment samples were analysed for physical and chemical properties, namely, grain size and organic carbon content. The seasonal changes in concentrations of As, Cr, Cu, Fe, Pb, Mn, Mo, Ni, Se, Sr, U and Zn were also analysed within the surface water and sediment. Increased nutrient concentrations within the water were evident during spring and summer at some of the sites, which influenced other water quality variables, e.g., dissolved oxygen and pH. Seasonal trends in metal concentrations were influenced by the prevailing environmental conditions (e.g., rainfall) experienced at the selected sites as well as physical and chemical properties (e.g., grain size and organic carbon content). This study showed distinct seasonal variability of water and sediment quality parameters in endorheic reed pans on the Mpumalanga Highveld. There is a need for further studies on all of the different types of pans in terms of their water and sediment quality. This type of information will allow for a sound and defensible scientific basis for the assessment of likely impacts (e.g., eutrophication), the evaluation of the significance of these impacts, and the design of remedial and preventative measures. <![CDATA[<b>Sorptive removal of ciprofloxacin hydrochloride from simulated wastewater using sawdust</b>: <b>Kinetic study and effect of pH</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500004&lng=pt&nrm=iso&tlng=pt The present work describes dynamic uptake of the antibiotic drug ciprofloxacin hydrochloride (CH), by using a cost-effective agricultural by-product - sawdust (SD). The sawdust was characterised by FTIR and SEM analysis. The sorbent particles were highly porous with average pore diameter of nearly 10 μm. The optimum pH and solid/liquid ratio for sorption of CH were found to be 5.8 and 2.0, respectively. The dynamic drug uptake data was applied to various kinetic models and their order of fitness was found to be pseudo second order > Elovich equation > power function model, as indicated by their regression values. The experimental equilibrium uptake values (q ) were in close agreement with those evaluated from the pseudo second order equation for initial sorbate concentrations of 10 and 20 mg-l-1 at 33°C. The drug uptake mechanism was found to be attractive non-electrostatic interactions, involving H-bonding interactions between H atoms and other electronegative species such as F, O and N of the drug molecule. The mechanism is discussed on the basis of pHpzc of sawdust and zwitterionic nature of drug CH. Mass transfer analysis was carried out using the drug uptake data obtained with sorbate concentrations of 10 and 20 mg-l-1. The used sorbent could be regenerated using 1.0 moll-1 HCl solution with a regeneration efficiency of nearly 85%. <![CDATA[<b>Aerobic biotransformation of 2, 4, 6-trichlorophenol by <i>Penicillium chrysogenum</i> in aqueous batch culture</b>: <b>degradation and residual phytotoxicity</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500005&lng=pt&nrm=iso&tlng=pt 2,4,6-trichlorophenol (TCP) is a toxic compound widespread in the environment, with numerous applications. There are many fungi capable of degrading it, although little attention has been paid to non wood-degrading species. Penicillium chrysogenum ERK1 was able to degrade 85% of TCP in batch cultures in the presence of sodium acetate. Degradation rate was fitted to a specific first-order kinetic and the growth rate was fitted to a Gompertz model. Hydroquinone and benzoquinone were identified as degradation intermediates. The phytotoxicity of the residues was reduced by half after fungal treatment. These results suggest that Penicillium chrysogenum can be applied successfully to biodegrade TCP. <![CDATA[<b>Photocatalytic degradation of geosmin</b>: <b>reaction pathway analysis</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500006&lng=pt&nrm=iso&tlng=pt The presence of geosmin in drinking water imparts a musty odour which leads to consumer complaints. Geosmin and other unwanted organics can be treated using photocatalysis. However, the intermediates formed during the photocatalytic degradation process and their degradation pathways have not previously been described. In this study, the degradation profile, as well as the intermediates formed during the photocatalytic degradation of geosmin was monitored in an effort to obtain a better understanding of the degradation kinetics and pathway. Photocatalytic degradation of geosmin in the presence of radical scavengers was shown to be inhibited, as evidenced by the reduction in reaction rate coefficient (k') from 0.055 to 0.038 min"¹. The hydroxyl radical reaction was thus shown to be the predominant process over direct photolysis by incident UV energy. Results from mass spectrum analysis of degradation intermediates indicate rapid fission of sp3l-sp3 (Cl-C) bonds resulting in ring opening of the cyclic geosmin structure. Bicyclic compounds that could be expected from dehydration and dehydrogenation of geosmin's ringed structure were not found among the detected intermediate products. Intermediates identified consisted of acyclic unsaturated alkenes, carbonyl compounds and some organic acids. Although the identified degradation products are not seen to be directly harmful, chlorine disinfection of water containing these compounds could produce potentially harmful halogenated hydrocarbons. <![CDATA[<b>Natural organic matter (NOM) in South African waters</b>: <b>NOM characterisation using combined assessment techniques</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500007&lng=pt&nrm=iso&tlng=pt In order to remove natural organic matter (NOM) from water in a water treatment train, the composition of the NOM in the source water must be taken into account, especially as it may not necessarily be uniform since the composition is dependent on the local environment. The main thrust of this study was to ascertain whether a cocktail of characterisation protocols could help to determine the nature, composition and character of NOM in South African waters. The characterisation of South African water sources was done by sampling 8 different water treatment plants located within the 5 major source water types in South Africa. The NOM composition of all of the samples was first studied by applying conventional techniques (UV, DOC, SUVA and bulk water parameters). NOM characterisation was then further conducted using advanced techniques (BDOC, PRAM and FEEM), which were aimed at developing rapid assessment protocols. The FEEM and UV results revealed that the samples consisted mainly of humic substances with a high UV-254 absorbance, while some samples had marine humic substances and non-humic substances. The sample's DOC results were within the range of 3.5 to 22.6 mgl-1 C, which was indicative of the extent of variation of NOM quantities in the regions where samples were obtained. The BDOC fraction of the NOM ranged between 12 and 66%, depending on the geographical location of the sampling site. A modified PRAM was utilised to characterise the changes in NOM polarity in the water treatment process. PRAM results also indicated that the NOM samples were mostly hydrophobic. The composition and character of the NOM was found to vary from one water treatment plant to another. Combining conventional and advanced techniques could be a powerful tool for NOM characterisation and for extracting detailed information on NOM character, which should inform its treatability. <![CDATA[<b>A new spectrophotometric method for determination of residual polydiallyldimethylammonium chloride flocculant in treated water based on a diazotization-coupled ion pair</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500008&lng=pt&nrm=iso&tlng=pt Polydiallyldimethylammonium chloride (polyDADMAC) is a water-soluble cationic polyelectrolyte used for water treatment. Its residues in treated water are contaminants as they react with chlorine to produce a carcinogenic compound. Commonly-used techniques for quantification of the polycation, such as colloidal and potentiometric titration as well as Ή NMR, have poor sensitivity and detection limits. This paper describes a more sensitive UV spectrophotometric method for quantitative determination of residual polyDADMAC in treated water, through formation of an ion pair with (4-hydroxy-1-napthylazo) benzene-sulphonic acid (dye). The ion pair, which is a colloidal solid material, was characterised by FTIR, 13C NMR and Ή NMR techniques. The colloid materials formed with different concentrations of polyDADMAC were dissolved in either N,N-dimethylformamide or 1,4-dioxane, followed by determination with UV spectrophotometry. The wavelength of maximum absorption (λ ) was found to be dependent on the solvent used, with 1,4-dioxane showing a better linear range of 0.1-1.8 mg-l-1 polyDADMAC. Varying the pH of the solutions had no significant effect on λ max. <![CDATA[<b>The distribution of inherent phosphorus in fifteen water treatment residues from South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500009&lng=pt&nrm=iso&tlng=pt Water treatment residues (WTR), the by-products of the production of potable water, are chemically benign, inorganic materials which are suitable for disposal by land application, though they are frequently reported to have high phosphorus (P) sorption capacities. An understanding of the distribution of inherent P in WTR is, however, required, if sorption-desorption processes are to be correctly interpreted. The aim of this investigation was to characterise the chemical properties relevant to P-sorption/desorption processes of 15 South African WTR and to determine the inherent distribution of P within the WTR using a chemical fractionation procedure. The pH, exchangeable Ca and organic carbon content ranged from 4.77 to 8.37, 238 to 8 980 mgkg-1 and 0.50 to 11.6 g100 g-1, respectively. Dithionate, oxalate and pyrophosphate extractable Al fractions ranged from 741 to 96 375, 1 980 to 82 947 and 130 to 37 200 mgkg-1, respectively, and dithionate, oxalate and pyrophosphate extractable Fe ranged from 441 to 15 288, 3 865 to 140 569 and 230 to 90 000 mgkg-1, respectively. Mechanisms of P-retention are residue specific, being dependent on the chemical properties of the WTR. Elevated Ca and amorphous Al and Fe concentrations did, nevertheless, suggest that all residues had the capacity to adsorb high amounts of P and to retain this P in forms unavailable for plant uptake. <![CDATA[<b>Point-of-use water purification using clay pot water filters and copper mesh</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500010&lng=pt&nrm=iso&tlng=pt Lack of clean water for use by rural communities in developing countries is of great concern globally. Contaminated water causes water-borne diseases such as diarrhoea, which often lead to deaths, children being the most vulnerable. Therefore, the need to intensify research on point-of-use (POU) water purification techniques cannot be overemphasized. In this work, clay pot water filters (CPWFs) were fabricated using terracotta clay and sawdust. The sawdust was ground and sieved using 300, 600 and 900 μιη sieves. The clay and sawdust were mixed in the ratios 1:1 and 1:2, by volume. Pots were then made, dried and fired in a furnace at 850ºC. Raw water collected from nearby rivers was filtered using the pots. The raw and filtered water samples were then tested for E. coli, total coliforms, total hardness, turbidity, electrical conductivity, cations and anions. The 600 μιη pot had the capacity to destroy E. coli completely from the raw water, whereas the 900 μm pot reduced it by 99.4%. The 600 μm and 900 μm pots could reduce the total coliform concentration by 99.3% and 98.3%, respectively. An attempt was also made to investigate the germicidal action of copper on the coliforms in raw water, with a view to utilising it in the CPWFs. Results showed that 10 g of copper, in the form of mesh made of thin wire of diameter 0.65 mm, had the capacity to completely eliminate E. coli, by immersing it in 300 ml of raw water for 5 h, and total coliforms, by immersing it for 10 h. Subsequently, copper was added to the CPWF by placing the mesh in the receptacle of the CPWF. Tests showed that copper could destroy any remaining E. coli in the filtered water, rendering the CPWF a completely viable POU technique for producing clean water. All other critical parameters such as total hardness, turbidity, electrical conductivity and ions in the filtered water were also within acceptable levels for drinking water quality. The filtration rate of the pot was also measured as a function of grain size of the sawdust and height of the water column in it. The filtration rate was found to increase with grain size and height in all of the pots. <![CDATA[<b>Field testing of polymeric mesh and ash-based ceramic membranes in a membrane bioreactor (MBR) for decentralised sewage treatment</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500011&lng=pt&nrm=iso&tlng=pt This paper presents the initial findings of field testing of 2 low-cost membrane filters, viz. 30 μm polymeric mesh and 2-6 μηι macroporous waste-ash based ceramic filter, in a submerged membrane bioreactor (MBR) employing batch anoxic and aerobic conditions. The influent was raw wastewater from a residential complex located near Delhi, India. The results indicated that the ceramic filter was able to operate for longer periods without cleaning; however, there is a limit to the transmembrane pressure it can withstand. The suspended solids retention was high with both filters (average of 96%). Moderate reduction in chemical oxygen demand (COD), total nitrogen (NH,+) and total phosphorus (PO,³) was achieved. The improvements in operation required in such systems are also underlined. <![CDATA[<b>Fluoride concentrations in groundwater and impact on human health in Siloam Village, Limpopo Province, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500012&lng=pt&nrm=iso&tlng=pt Monitoring of fluoride concentrations in groundwater, identification of sources, and monitoring of the impact of fluoride on human health was undertaken in Siloam Village, Limpopo Province, South Africa. Most of the inhabitants of Siloam Village rely on groundwater for domestic use due to inadequate pipe-borne water supply. A preliminary survey showing that some community members in Siloam Village have mottled teeth motivated the study. Temperature and pH were measured in the field while fluoride and calcium in groundwater were analysed in the laboratory. A survey was conducted to obtain information on the impact of fluoride on human health. 40% of the households and 1 primary school in Siloam Village were interviewed. Fluoride concentrations in groundwater samples were found to be higher than the Department of Water Affairs and World Health Organization recommended values for domestic use of 1 mg/t and 1.5 mg/l, respectively. The results of paired two-tailed t-tests showed significant differences between mean values of pH, temperature, calcium and fluoride concentrations for all paired comparisons between 3 sites, with the exception of comparisons between sites GW1 (community borehole) and GW2 (artesian spring). Alkaline pH, low calcium concentrations, high groundwater temperatures and semi-arid climatic conditions of the study area may cause elevated fluoride concentrations in groundwater, by increasing the solubility of fluoride-bearing formations (fluorite). A survey revealed that 87% of the households use groundwater while 85% of these have family members with mottled teeth. 50% of children between the ages of 11 and 14 in Siloam Primary School also have mottled teeth. There is thus evidence suggesting negative human health impacts of high fluoride concentrations in groundwater in Siloam Village. The majority of the community was found to be aware of the fluorides in groundwater and the health impacts thereof making interventions easy to promote. <![CDATA[<b>Assessment of <i>in-situ</i> abundance dynamics of enterobacteria and total heterotrophic aerobic bacteria in groundwater in the equatorial region of Central Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500013&lng=pt&nrm=iso&tlng=pt The main purpose of this investigation was to assess, in situ, the hourly abundance dynamics of enterobacteria and total heterotrophic aerobic bacteria (THAB), over a daily period, in 3 wells in Yaounde region, Cameroon. Sampling was done weekly, for 4 months. Water samples were collected in sterile glass bottles and incubated in situ for 2 h, 4 h, 6 h, 8 h, 10 h and 12 h. Isolation and enumeration of enterobacteria and THAB were performed on MacConkey agar (Bio-Rad) and standard agar (Bio-Rad) media, respectively, using the plate count method. Using a linear regression model, ln(number of CFUs) was plotted against time. The slope of each regression line was considered as the apparent increase or decrease in cell number. Concentrations of THAB and enterobacteria varied from 9.90 to 14.19 and 4.09 to 9.59 ln units-ml-1, respectively, in W1, from 9.90 to 14.25 and 3.00 to 5.39 ln units-ml-1 in W2, and from 9.90 to 14.00 and 6.55 to 11.51 ln units-ml-1 in W3. For the first 6-hour incubation period at all of the sampling points, the cell apparent growth rate (CAGR) varied from 0.023 to 0.262 h-1 for THAB and from 0.001 to 0.315 h-1 for enterobacteria; cell apparent inhibition rate (CAIR) varied from 0.015 to 0.615 h-1 for THAB and from 0.015 to 0.604 h-1 for enterobacteria. In the second 6-h incubation period, the CAGR varied from 0.010 to 0.822 h-1 for THAB and from 0.015 to 0.771 h-1 for enterobacteria; the CAIR varied from 0.015 to 0.260 h-1 for THAB and from 0.007 to 0.338 h-1 for enterobacteria. The values of physico-chemical parameters recorded before incubation displayed temporal and spatial variation over the sampling period. Bacterial abundance dynamics in some cases was significantly correlated to some of these abiotic factors. The abundance of the microorganisms decreased initially but later increased. <![CDATA[<b>Characteristics of local groundwater recharge cycles in South African semi-arid hard rock terrains</b>: <b>Rainfall-groundwater interaction</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500014&lng=pt&nrm=iso&tlng=pt The semi-arid and arid regions occupy almost two-thirds of South Africa and fall in the winter and summer rainfall zones of the sub-continent. The annual rainfall patterns can be regarded as intermittent with a significant spatial variability due to the unique winter/summer synoptic systems manifesting over Southern Africa. Summer rainfall events indicate that episodic wet periods, consisting of up to 8 consecutive days, may contain falls that contribute to almost 45% to 60% of the total annual rainfall of an area; associated with relatively higher rain rates (1.5 to 10 mmh-1). Hyetograph-hydrograph time-series data sets, however, indicate that episodic rainfall events are responsible for rapid, but sustainable groundwater recharge events. The recurrence rate of these events in the semi-arid and arid regions is still low and aquifer storage-recharge is therefore not an annual event. The recharge flow path through the unsaturated zone reservoir plays an important role in the underdrainage flow pattern, and subsequently the saturated flow regime. It resembles a simple L-shaped flow path driven by direct recharge mounding in the fractured hard rock terrain and indirect recharge to the surrounding sub-reservoirs. The lag-times between rainfall events and water table responses were found to be significantly short; a matter of a few hours to less than a few days. Evidence of multi-modal, time-related infiltration phases during the summer early and peak rainfall intervals, governed by the field capacity status of the unsaturated zone reservoir and the growth status of the local vegetation, were observed. A unique rainfall pattern in semi-arid and arid regions is required before a sustainable aquifer storage-recharge condition develops and such incidences could be a one-in-several-year (5 to 9) event. <![CDATA[<b>Vulnerability of wastewater infrastructure of coastal cities to sea level rise</b>: <b>a South African case study</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500015&lng=pt&nrm=iso&tlng=pt Sea-level rise is one of the consequences of global warming that has the potential to affect the infrastructure of coastal urban areas. In this context, it is important to perform vulnerability assessments in order to understand how this infrastructure may be at risk, and, if necessary, adapt and maintain functionality of infrastructure systems. This study investigates the vulnerability of the wastewater collection and disposal infrastructure (i.e. pipelines and manholes, pumping stations and wastewater treatment plants) to sea-level rise in eThekwini Municipality, South Africa. By using geographical information systems (GIS) and a multi-criteria analysis considering elevation, operational capacity and connectivity, a scale of vulnerability was established and the most vulnerable infrastructural elements were identified in the municipality. These should be prioritised for detailed monitoring and adaptive interventions in order to maintain the functionality of the wastewater system as sea level is predicted to rise. As such this study presents a model of how vulnerability of wastewater systems can be evaluated in coastal cities. <![CDATA[<b>A short-range weather prediction system for South Africa based on a multi-model approach</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500016&lng=pt&nrm=iso&tlng=pt The accurate prediction of rainfall events, in terms of their timing, location and rainfall depth, is important to a wide range of social and economic applications. At many operational weather prediction centres, as is also the case at the South African Weather Service, forecasters use deterministic model outputs as guidance to produce subjective probabilistic rainfall forecasts. The aim of this research was to determine the skill of a new objective multi-model, multi-institute probabilistic ensemble forecast system for South Africa. Such forecasts are obtained by combining the rainfall forecasts of 2 operational high-resolution regional atmospheric models in South Africa. The first model is the Unified Model (UM), which is operational at the South African Weather Service. The UM contributes 3 ensemble members, each with a different physics scheme, data assimilation techniques and horizontal resolution. The second model is the Conformal-Cubic Atmospheric Model (CCAM) which is operational at the Council for Scientific and Industrial Research, which in turn contributed 2 members to the ensemble system based on different horizontal resolutions. A single-model ensemble forecast, with each of the ensemble members having equal weights, was constructed for the UM and CCAM models, respectively. These UM and CCAM single-model ensemble predictions are then combined into a multi-model ensemble prediction, using simple un-weighted averaging. The probabilistic forecasts produced by the single-model system as well as the multi-model system have been tested against observed rainfall data over 3 austral summer 6-month periods from 2006/07 to 2008/09, using the Brier skill score, relative operating characteristics, and the reliability diagram. The forecast system was found to be more skilful than the persistence forecast. Moreover, the system outscores the forecast skill of the individual models. <![CDATA[<b>Rainy season characteristics of the Free State Province of South Africa with reference to rain-fed maize production</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500017&lng=pt&nrm=iso&tlng=pt The study assesses onset of rains, cessation of rains, duration of rainy season and seasonal rainfall at different probability levels. Daily rainfall data for 309 stations located in the Free State Province of South Africa were analysed from 1950 to 2008. The cumulative rainfall over 3 consecutive dekads (10-day periods) and cumulative rainfall over 1 dekad were used to determine onset of rains and cessation of rains respectively. Seasonal rainfall was determined as the accumulated rainfall from November to March. Rainbow statistical software was utilised to test for normality and determine probabilities at 20%, 50% and 80% risk levels. The other rainy season characteristics investigated were the probability of onset failure and probability of rainy season duration of less than 50, 100, 120 and 140 days. These rainy season indices were investigated in relation to maize production in the Free State. Rainfall behaviour during the growing period is one of the main limiting factors to rain-fed maize production, consequently influencing household food security. The results show that for onset of rains there is a large spatial variance over the Free State while cessation of rains shows small variance. There is also an east to west progression of onsets while the duration of the rainy season and seasonal rainfall also increased from west to east. Areas of low risk associated with rainy season characteristics are evident over the Thabo Mofutsanyane, eastern Motheo, eastern and northeastern Lejweleputswa and the Fezile Dabi districts, making these areas highly suitable for maize production. By contrast, high-risk areas are in the western and southern parts of the province and thus dryland maize production has low production potential in these areas. <![CDATA[<b>A socio-economic impact assessment of a project to identify and implement best management practices at the Zanyokwe Irrigation Scheme at farm level</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500018&lng=pt&nrm=iso&tlng=pt The main aim of this study was to assess the impact of the Best Management Practices (BMP) project on social and economic wellbeing at the Zanyokwe Irrigation Scheme (ZIS) in central Eastern Cape Province. The BMP project is a knowledge-based initiative aimed at introducing management practices in order to improve production and livelihoods in the study area. The study employed a survey to collect socio-economic data amongst farming households. The 2005 (pre-BMP project) baseline study based on the same respondents allowed for the tracking of changes after the implementation of the project. A socio-economic impact assessment (SEIA) framework was used to assess the impacts. The results showed the BMP project to have impacted on social and economic wellbeing of households. Skills introduced were in the areas of water management, agronomic practices, marketing and institutional arrangements. In 2007 more than half of farmers worked on their farms daily, an improvement on 2005, when none of the farmers reported working over weekends. The average time spent on the farms per day also increased from 4 (in 2005) to 7 h (in 2007). Agriculture's contribution to household income improved from 71% in 2005 to 81% in 2007 and reduced household poverty and food insecurity levels. The number of households earning incomes below the poverty line dropped from 61°% in 2005 to 38% in 2007. A marked increase was noted in winter land use, which was almost non-existent in 2005. The on-farm trials introduced by the BMP team improved the farmers': maize planting time, plant population density, fertiliser management, crop yield and participation in community activities. Seedling transplanting was preferred to direct maize seeding. Positive impacts on institutions were seen in the restructuring of the management system; improved marketing systems; institutional arrangements for managing water; and institutions for maintaining irrigation infrastructure. <![CDATA[<b>An evaluation of the Contractor Development Model of Working for Water</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500019&lng=pt&nrm=iso&tlng=pt The Working for Water programme of the South African Department of Environmental Affairs has as its major objective the eradication of invasive alien plant species. However, it also has a social development component, which aims at the promotion of small business and entrepreneurship development. This paper explores the socio-economic rationale of one component, the Contractor Development Model. It does so via an examination of the programme's assumptions, and the development of its impact theory. The study revealed a shortcoming in monitoring data for the programme, and a relative lack of assessment of the effectiveness of its activities. It is suggested that the selection criteria for contractors be reexamined, and that consideration be given to two additional elements that may strengthen the effectiveness of the training: mentoring and networking. <![CDATA[<b>Dairy farm borehole water quality in the greater Mangaung region of the Free State Province, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500020&lng=pt&nrm=iso&tlng=pt Most dairy farm effluent is discharged onto pastures and land by irrigation and poses a risk of enriching groundwater including borehole drinking water. Nitrate, coliforms and Escherichia coli (E. coli), in particular, may cause disease in humans and animals drinking contaminated water. The aim of this study was to obtain an understanding of the status of borehole drinking water quality, including physical, chemical and microbiological properties, on 75 dairy farms in the greater Mangaung region of the Free State, South Africa. Borehole drinking water samples were collected during autumn and spring of 2009 and the physical, chemical and microbiological parameters analysed and compared to the required standards prescribed by the South Africa National Standards (SANS) 241 of 2006. Most farms were compliant; however for combined nitrate and nitrite N, 37 of the farms exceeded the prescribed limit. Similarly, for total coliforms, 45, and for E. coli, 22 of the farms exceeded the acceptable limits. Nine of the farm boreholes were contaminated by N and E. coli. On two of the farms four of the chemical parameters exceeded the prescribed limits, including those for N; both farms were, however, compliant for E. coli. The results of this study suggest that further research on water and waste management on dairy farms in the Manguang region of the Free State should be conducted. <![CDATA[<b>Rapid <i>in vitro</i> tests to determine the toxicity of raw wastewater and treated sewage effluents</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500021&lng=pt&nrm=iso&tlng=pt Wastewater consists of a complex mixture of substances. During wastewater treatment these harmful substances can be eliminated or degraded. However, persistent compounds released with the treated sewage effluents enter the environment and pose a risk to animal and human life. To determine the potential risks involved, screening tests are needed to monitor wastewater for potential toxic contaminants. The aim of this study was to validate and use screening tests to determine the toxicity of raw wastewater and treated sewage effluents from 3 sewage treatment plants in the Western Cape, South Africa. Raw wastewater and treated sewage effluents were screened for cytotoxicity using lactate dehydrogenase (LDH) release from cells as biomarker, for neurotoxicity using acetylcholinesterase (AChE) inhibition and for genotoxicity using the Save Our Soul (SOS) test. Results showed no cytotoxicity for both raw wastewater and treated sewage effluents from all sewage treatment plants. Raw wastewater from all sewage treatment plants contained AChE inhibitors and sewage treatment processes were not effective at eliminating these AChE inhibitors. Raw wastewater from all sewage treatment plants tested positive for genotoxicity. Treated sewage effluents from all three sewage treatment plants displayed no genotoxicity indicating effective removal of genotoxins by all three sewage treatment plants investigated. <![CDATA[<b>Use of calcium sulphate dihydrate as an alternative to the conventional use of aluminium sulphate in the primary treatment of wastewater</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500022&lng=pt&nrm=iso&tlng=pt The application of calcium sulphate dihydrate (CaSO4'2H2O) as a coagulant-flocculant alternative to the conventional use of aluminium sulphate in the primary treatment of wastewater was evaluated using a jar test apparatus. Samples from the State Water Commission (CEA) in Queretaro, Mexico, were collected for the experiments. Turbidity and pH were measured before and after applying the calcium sulphate dihydrate (CaSO4'2H2O). Turbidity readings obtained for the doses of 4 g-f"¹ of aluminium sulphate varied from 3.91 to 3.87. The corresponding water pH was 3.90, giving the water an acidic character. Use of aluminium sulphate in the clarification of wastewater, thus, has financial and environmental implications due to the need to raise the pH of the treated water to 6.5-8.5, the recommended optimum interval for the physical-chemical-biological removal of pollutants. By contrast, calcium sulphate di-hydrate (CaSO(4)2H2O) (gypsum) doses of 1, 1.5 and 2 gt"¹ resulted in a pH of between 7.04 and 7.51 repeatedly. These findings suggest that the application of calcium sulphate di-hydrate (CaSO4'2H2O) as coagulant-flocculant, followed by the process of sedimentation, may be a suitable alternative for the clarification of wastewater. However, the turbidity reported for the same doses was 74.05, 80.5 and 74.5 NTU, respectively, well above the international standard of 5 NTU. The effect of gypsum on turbidity warrants further research. <![CDATA[<b>Isolation and identification of bacterial pollutants from the Berg and Plankenburg Rivers in the Western Cape, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500023&lng=pt&nrm=iso&tlng=pt Bacterial species present in the Berg and Plankenburg Rivers (Western Cape, South Africa) were isolated from water and biofilm samples and population shifts between sampling sites were phylogenetically identified. Deoxyribonucleic acid (DNA) extraction of representative isolates was performed and amplified using 2 different primer sets. Various Enterobacteriaceae species were present at all of the sites, confirming faecal contamination. Phylogenetic analyses also showed that, in general, Gram-negative micro-organisms dominated at all of the sites sampled in both the Berg and Plankenburg river systems. Pathogens and opportunistic pathogens, such as Pseudomonas aeruginosa, Staphylococcus sp., and Bacillus cereus, were isolated from the Berg River. Similarly, in the Plankenburg River system, Aeromonas sp., Acinetobacter sp., Stenotrophomonas sp. and Yersinia enterocolitica were also isolated. This raises major health concerns as human population densities along both rivers are high, thus resulting in increased human exposure to these organisms. <![CDATA[<b>Reduction of Langelier index of cooling water by electrolytic treatment with stainless steel electrode</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500024&lng=pt&nrm=iso&tlng=pt The efficiency of electrolytic treatment in reducing the Langelier saturation index (LSI) of the cooling water from a cooling tower of a textile industry was investigated. Sacrificial anodes were employed which prevent obnoxious chlorine generation. A series of batch experiments using stainless steel electrodes were conducted with 4 different current densities (5, 7, 10 and 15 A/m²) and 6 different electrolysis times (20, 30, 40, 50, 60 and 70 min). The use of 7 A/m² for 50 min electrolysis time yielded a satisfactory efficiency in reducing the LSI index from 2.57 to zero, indicating that the treated water was of sufficient quality to be reused in the cooling process. <![CDATA[<b>Guide to groundwater monitoring for the coal industry</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500025&lng=pt&nrm=iso&tlng=pt It is well established in literature that the environmental impacts associated with the coal industry are numerous. In respect of South Africa's groundwater resources the major impact of the coal industry is a reduction in groundwater quantity and quality. There is therefore a need to proactively prevent or minimise these potential impacts through long-term protection and improved water management practices. One such initiative is to implement monitoring programmes in various sectors of the coal industry for groundwater quality and quantity. Groundwater monitoring requires sophisticated interlinked stages which are often overlooked or not fully understood. Consequently a methodical approach must be undertaken in order to have an effective and economical groundwater monitoring system. This paper provides a comprehensive guide to the establishment of a groundwater monitoring programme for environmental practitioners in the coal industry. An inclusive 7-stage methodology is presented describing the different stages of establishing a groundwater monitoring programme, focusing on the 'why', 'how', and 'who' of groundwater monitoring. <![CDATA[<b>Funke N and Nienaber S (2012) Promoting uptake and use of conservation science in South Africa by government <i>(Water SA</i> 38 (1) 105-113)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502012000500026&lng=pt&nrm=iso&tlng=pt It is well established in literature that the environmental impacts associated with the coal industry are numerous. In respect of South Africa's groundwater resources the major impact of the coal industry is a reduction in groundwater quantity and quality. There is therefore a need to proactively prevent or minimise these potential impacts through long-term protection and improved water management practices. One such initiative is to implement monitoring programmes in various sectors of the coal industry for groundwater quality and quantity. Groundwater monitoring requires sophisticated interlinked stages which are often overlooked or not fully understood. Consequently a methodical approach must be undertaken in order to have an effective and economical groundwater monitoring system. This paper provides a comprehensive guide to the establishment of a groundwater monitoring programme for environmental practitioners in the coal industry. An inclusive 7-stage methodology is presented describing the different stages of establishing a groundwater monitoring programme, focusing on the 'why', 'how', and 'who' of groundwater monitoring.