Scielo RSS <![CDATA[Water SA]]> vol. 36 num. 5 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Soil as indicator of hillslope hydrological behaviour in the Weatherley catchment, Eastern Cape, South Africa</b>]]> There is an interactive relationship between soil and hydrology. Identifying and interpreting soil properties active in this relationship can enhance our understanding of the hydrological behaviour of soils and the hillslopes in which they occur. This study was conducted in the Weatherley research catchment, South Africa, where a hillslope in the upper part of the catchment was selected for detailed study. Soil properties and their spatial distribution in the hillslope were interpreted and related to their predicted hydrological response. From these interpretations a conceptual model of hillslope hydrological behaviour was developed. Vertical drainage was considered to be dominant in the upper areas of the hillslope as indicated by the presence of freely-drained apedal soils. These soils recharge the mid- and lower slope. Soils showing clear indications of interflow (A/B and soil/bedrock interface) dominate on the midslope. The valley bottom is covered by gleyed soils which is an indication of long periods of saturation. These saturated conditions favour overland flow due to saturation impairing infiltration. The conceptual model was then evaluated using hydrometric measurements in the form of tensiometers and streamflow hydrographs. Results confirm the reliability of the model and accentuate the contribution that soil science can make to the science of hydrology. <![CDATA[<b>Soil</b>: <b>water relationships in the Weatherley catchment, South Africa</b>]]> Soil water content is influenced by soil and terrain factors, but studies on the predictive value of diagnostic horizon type for the degree and duration of wetness seem to be lacking. The aim of this paper is therefore to describe selected hydropedological soil-water relationships for important soils and diagnostic horizons in the Weatherley catchment. Daily soil water content was determined for 3 horizons in 28 profiles of the Weatherley catchment. These data were used to calculate annual duration of water saturation above 0.7 of porosity (AD ), which was correlated against other soil properties. Significant correlations (α = 0.05) were obtained between average degree of water saturation per profile and slope (R² = 0.24), coarse sand content (R² = 0.22), medium sand content (R² = 0.23), fine silt content (R² = 0.19), and clay content (R² = 0.38). AD per diagnostic horizon ranged from 21 to 29 d•yr-1 for the red apedal B, yellow brown apedal B, and neocutanic B horizons; 103 d•yr-1 for the orthic A horizons; and from 239 to 357 d•yr-1 for the soft plinthic B, unspecified material with signs of wetness, E, and G horizons. A regression equation to predict AD from diagnostic horizon type (DH), clay to sand ratio (Cl:Sa), and underlying horizon type (DH ) gave: AD = -26.31 + 41.64 ln(Cl:Sa) + 35.43 DH + 13.73 DH (R² = 0.78).Results presented here emphasise the value of soil classification in the prediction of duration of water saturation. <![CDATA[<b>Investigation of potential water quality and quantity impacts associated with mining of the shallow Waterberg coal reserves, west of the Daarby Fault, Limpopo Province, South Africa</b>]]> From South African and international experience, it is known that coal mining has a pronounced impact on surface and groundwater quality and quantity. The influx of water may be as low as 1% of rainfall for underground mines to as much as 20% for opencast mines. Such differences may influence the quantity and quality of surface water and groundwater resources at the local scale and further afield. The Waterberg coal reserves represent the only area with proven coal reserves which are still available for development in South Africa. These reserves are targeted for large-scale mining in the near future, and are situated in a relatively dry part of South Africa. In view of the low rainfall and limited surface water resources, the necessary level of safeguard measures to ensure the quantity and quality of existing water resources is unclear. Experience from other areas cannot necessarily be extrapolated directly. A scoping level study was performed to consolidate the existing information on the geohydrology and pre-mining water quantity and quality of water resources associated with the Waterberg coal reserves. New data regarding water quality and acid-base potential for the different geological areas (through field investigations) and geology and mining methods were obtained. Findings showed a significant likely impact on groundwater resources, with a potential for generation of acid mine drainage, although low transmissivities will in all probability prevent decant after back-filling is complete. <![CDATA[<b>Comparative assessment of widespread irrigation with low quality mine-water in undisturbed and rehabilitated mine-lands in the upper Olifants using the ACRU2000 model</b>]]> The ACRU agrohydrological model, in the form of ACRU2000 and its salinity module, ACRUSalinity, was employed in catchment-scale assessment of widespread irrigation with low quality mine-water in undisturbed (un-mined) and rehabilitated soils in the Upper Olifants basin of South Africa. The study area comprised a small catchment of 4.7 km² located in a coal-mine environment, known as the Tweefontein Pan catchment. The catchment drained to a surface reservoir (Tweefontein Reservoir) of maximum capacity and surface area 4 000 Ml and 1.5 km², respectively. The catchment was instrumented to measure hydrodynamic responses and simulated as a hydrological system. Consideration was given to runoff, groundwater storage, evapotranspiration, baseflow, interception, irrigation water supply and rainfall, thereby accounting for all the dominant hydrological components of the system. Three scenarios were simulated using the available records for 5 years (1999 to 2004). The first was a baseline scenario representing the prevailing condition in the study area and the other 2 scenarios represented widespread irrigation with the mine-water on undisturbed and rehabilitated soils. In simulating the widespread irrigation on rehabilitated soils, a distinction was made between a rehabilitated irrigated area before and after the re-establishment of the equilibrium water table. Comparison of the results from the simulated scenarios indicated that a greater undisturbed area (max of 160 ha) than rehabilitated area (max of 120 ha) could be irrigated with mine-water from the Tweefontein Reservoir. Irrigation on rehabilitated soils depleted the water in the reservoir more rapidly than irrigation on undisturbed soils, due to lower runoff and higher ingress to groundwater in rehabilitated areas. <![CDATA[<b>Estimating the recreational value of freshwater inflows into the Klein and Kwelera estuaries</b>: <b>an application of the zonal travel cost method</b>]]> This study estimates the change in aggregate consumer surplus associated with increased freshwater supply into two South African estuaries, namely, the Klein and the Kwelera. The estimation entailed the application of a contingent behaviour, single-site Clawson-Knetsch travel cost model. The value estimates derived reflect the benefit of improved freshwater supplies into the estuaries in question over the status quo. In a survey, a questionnaire was administered face-to-face to 240 households at the Klein Estuary and 231 households at the Kwelera Estuary during the period between December 2005 and April 2006. It was deduced that in 2006 the marginal recreational value of freshwater inflow into the Klein Estuary was 5.7 cents/m³ (ZAR0.057/m³) and into the Kwelera Estuary 1.1 cents/m³ (ZAR0.011/m³). <![CDATA[<b>Multi-criteria decision making for water resource management</b>: <b>a case study of the Gediz River basin, Turkey</b>]]> In this study, a water resource management model that facilitates indicator-based decisions, with respect to environmental, social and economic dimensions in a multiple criteria perspective, is developed for the Gediz River Basin in Turkey. The basic input of the proposed model is the quantity of surface water that is mainly allocated to irrigation purposes. The model has been applied under 3 different hydro-meteorological scenarios that reflect baseline as well as better and worse conditions of water supply and demand, not only to reach a comprehensive assessment of the water budget in the Gediz Basin, but also to evaluate the impacts of proposed management alternatives under different conditions. The Water Evaluation and Planning (WEAP) software is used as a simulation and evaluation tool to assess the performance of possible management alternatives; performance is measured by 9 indicators representing economic, social and environmental sustainability. The study has delineated the best management alternative on the basis of 3 different multi-criteria decision making (MCDM) methods, including simple additive weighting (SAW), compromise programming (CP) and technique for order preference by similarity to ideal solution (TOPSIS). Each method is also applied with 7 different sets of criteria weights that represent objective judgements as well as subjective preferences of decision makers. The results of the study indicate that the decision on the best alternative is basically independent of the MCDM method used, but slightly sensitive to the weights assigned to the criteria as well as the data used in the analyses. <![CDATA[<b>Non-statutory barriers and incentives to stakeholder participation in reducing water pollution</b>: <b>a South African case study</b>]]> A study was conducted in the Baynespruit, a small, highly-polluted, urban catchment in Pietermaritzburg, South Africa with 2 objectives: firstly, to develop an understanding of the views of stakeholders regarding the pollution problem and the relative importance of components of the problem; secondly, to identify and investigate non-statutory barriers and incentives to participation in multi-stakeholder processes aimed at integrated catchment management to create a healthy Baynespruit. The research methods embraced a number of different qualitative techniques, including a review of print media coverage, semi-structured interviews conducted with a cross-section of stakeholders, as well as participant and direct observation. The study identified the stakeholder groupings along with a number of non-statutory barriers and incentives to their participation in integrated activities to reduce pollution. These barriers and incentives were classed as economic, situational, developmental and socio-cultural in nature. For local residents, building a network of contacts and partnerships could address many of the economic, developmental and socio-cultural barriers they were found to face. Barriers to industry participation in pollution reduction were found to include problems such as a lack of consequences for polluting, and the feeling that it was 'not their problem'. Powerful economic and situational incentives, such as pressure from corporate customers and the public, seem to remain largely unexploited by stakeholders opposing pollution. A lack of resources in the form of time, staff and equipment, as well as unsuccessful past experiences which have created a reluctance to prosecute or release information, were found to be the major impediments preventing staff at government agencies and parastatals from motivating other stakeholders to participate. <![CDATA[<b>Assessing users' experience of shared sanitation facilities</b>: <b>a case study of community ablution blocks in Durban, South Africa</b>]]> Despite significant financial investment, the effective implementation and sustained use of water and sanitation (WATSAN) technologies remains a chimera, with one billion people using unimproved water facilities and two and a half billion not benefitting from adequate sanitation. The poor success rate of WATSAN interventions results from a predominance of supply-driven approaches which lack recipients' inputs into planning and implementation to ensure that technologies are fully absorbed and adapted to users' needs. In the academic literature, users' feedback and experiences of technologies in the post-implementation phase have received scarce attention. The purpose of this study is to investigate users' experience of sanitation technologies in the early post-implementation phase, when opportunities for remedial intervention are still available. Fieldwork comprising semi-structured interviews was undertaken with users and potential recipients of three community ablution blocks (CABs) in informal settlements around Durban. Results suggest that non-technical aspects such as affordability or cleanliness of the facilities can affect acceptance among the investigated communities. User training is positively associated with higher levels of facility maintenance as well as satisfaction with its functionality. A comparison between users and potential recipients of CABs shows that perceived health benefits, attitudes in case of problems, and trust are affected by use of the facilities. Conclusions relate to how early post-implementation assessments of users' experience could enhance the process of acceptance and management of the technology, thereby increasing progress towards achievement of the related Millenium Development Goals. <![CDATA[<b>How much water is enough? Domestic metered water consumption and free basic water volumes</b>: <b>the case of Eastwood, Pietermaritzburg</b>]]> This article is based on an in-depth case study of urban water services to poor households in the community of Eastwood, Pietermaritzburg, in the province of KwaZulu-Natal, South Africa, for the period 2005-2007. The article adopts a mixedmethodological approach. Despite government progress in delivering water infrastructure post-1994, ability to pay for the service limited access. The free basic water policy, initiated by national Government in 2001, sought to provide all citizens, but particularly the poor, with a basic supply of free water. The concessions were envisaged to improve public health, gender and equity, affordability, and as an instrument of post-apartheid redress and poverty alleviation. Once free basic water (FBW) was declared a new imperative for local government the debate on exactly how much was enough, why 6 kl was chosen, the structure of the offering and broader state intentions opened up. This article positions the FBW offering within the prevailing international discourse on 'need' calculation. Through the exploration of actual water consumption patterns of urban poor households, the ideological assumptions and 'scientific' calculations underpinning this discourse were found to have ignored the fluidness of use as well as the value of water beyond mere physiological need. In this regard, access to FBW was conditioned on a small household size and further predicated the modification of normal water activities and lifestyle and carried a disproportionate social cost. The free basic volume of 6 kl was found to have no resonance with actual water volumes consumed by the majority of Eastwood households. <![CDATA[<b>Abundance of pathogenic bacteria and viral indicators in chlorinated effluents produced by four wastewater treatment plants in the Gauteng Province, South Africa</b>]]> The failure of South African wastewater treatment plants to produce effluents of a high microbiological quality is a matter of great concern in terms of the pollution of water resources. This study aimed at assessing the effectiveness of 4 wastewater treatment plants in the Gauteng Province, namely the Zeekoegat, Baviaanspoort, Rayton and Refilwe Water Care Works (WCW), in the removal of pathogenic bacteria and viral indicators. Also taken into consideration were free chlorine concentrations and turbidity levels, which were measured using standard methods. Conventional methods and/or polymerase chain reaction (PCR) techniques were used to detect and identify pathogenic bacteria and coliphages. The turbidity ranged from 2.39 to 62.40 NTU and the concentrations of free chlorine ranged from 0.03 to1.60 mg-t"¹ for all plants. Despite high free chlorine residual concentrations in treated effluents, the survival and occurrence of Escherichia coli, Salmonella typhimurium and Vibrio cholerae were significantly higher at Baviaanspoort (100%, 88.2% and 35.3%), Refilwe (87.5%, 59.4% and 21.9%) and Rayton (75%, 38.2% and 9.4%) compared to Zeekoegat, which only showed the survival of E. coli, at a much lower occurrence rate of 8.8%. Somatic and F-RNA coliphages were removed at 15.57 % and 13.96% for Baviaanspoort, 11.62% and 22.42% for Refilwe, 25% and 32.10% for Rayton, and 40.41% and 52.57% for Zeekoegat WCW. Significant correlations were found between pathogenic bacteria and coliphages at all plants (r = 0.765 for Baviaanspoort, r = 0.904 for Zeekoegat, r = 0.680 for Refilwe, r = 0.796 or the Rayton WCW, p < 0.01). A combination of sedimentation, rapid sand filtration and chlorination processes was found to be a major prerequisite for the reduction of turbidity levels and viral indicators and the successful removal of pathogenic bacteria in the Zeekoegat WCW. This study therefore suggests an upgrading of the wastwater treatment plants by including processes such as rapid sand filtration and UV disinfection, which have proved to be effective in the removal and inactivation of pathogenic bacteria and viruses. <![CDATA[<b>A survey of Vibrio cholerae O1 and O139 in estuarine waters and sediments of Beira, Mozambique</b>]]> This study determined whether the estuarine and freshwater environment in Beira, Mozambique, serves as a reservoir of Vibrio cholerae Ol and O139. Ninety-nine estuarine water samples were collected at 6 sites in Beira. An additional 54 samples were collected from rural areas around Beira which included 3 freshwater lake samples, 15 river, 5 pond, and 4 estuarine water samples, and an equivalent number of sediment samples, collected from the same sites as the water sam ples. In addition, fish scales from 5 ocean fish and 1 deep sea water sample were also collected. The samples were analysed for the presence of V. cholerae O1 and O139 using culture methods, the direct fluorescent antibody (DFA) method and polymerase chain reaction (PCR) using a single-primer pair for the ompW gene and a semi-nested PCR selecting for the ctxA gene, encoding subunit A of cholera toxin. DFA results showed 37 V. cholerae O1- and 6 O139-positive samples. Vibrio cholerae O1 and O139 were observed on the scales of 4 of the 5 fish. The findings of the study provided in situ evidence for V. cholerae O1 and O139, predominantly as viable but non-culturable cells in the aquatic environment of Beira. This is the first record of the presence of V. cholerae O139 in the estuarine environment on the coast of Africa. <![CDATA[<b>Bioaccumulation of non-essential trace metals in tissues and organs of <i>Clarias gariepinus</i> (sharptooth catfish) from the Vaal River system</b>: <b>strontium, aluminium, lead and nickel</b>]]> This is the first paper reporting on results obtained in a metal bioaccumulation study in the Vaal River system. It discusses concentrations of four non-essential elements (strontium, aluminium, lead and nickel) in water, sediment and various fish tissues. A second paper will report on concentration levels of the remaining five essential trace metals (chrome, copper, iron, manganese and zinc) studied. While heavy metals did accumulate in C. gariepinus tissues, no clear trends emerged with regard to differences between localities (Vaal Dam and Vaal River Barrage) or surveys. The highest non-essential element metal concentrations were generally recorded in gill (filaments and arches), followed by muscle, liver and lastly skin. This general trend appears to be in agreement with trends observed by other workers and reported in the literature. Variability in tissue metal concentrations in C. gariepinus within locality and seasons observed in this study is also reflected in results from available literature. This accentuates the importance of factors that influence the concentrations and bioavailability of trace metals. <![CDATA[<b>The defouling of membranes using polymer beads containing magnetic micro particles</b>]]> Polymer membranes provide a good method of obtaining potable water but, as membranes always foul during water purification, the flux drops with time. Methods of physical cleaning of the polymer membranes, which do not require the plant to be shut down for lengthy periods, are very attractive and also do not generate any waste fluids. This paper reports on an investigation into the possibility of obtaining flux enhancement during the filtration process, as well as the cleaning of membranes, using magnetic polymer beads moving under the influence of an AC magnetic field. Methods, procedures and results for cleaning membranes using magnetic beads, at zero trans-membrane pressure, are described. <![CDATA[<b>Sonochemical degradation of the antibiotic cephalexin in aqueous solution</b>]]> The degradation of cephalexin in aqueous solution under ultrasound irradiation was investigated. Biodegradability of the solution was evaluated by the BOD5/COD ratio, which was raised from zero to 0.36 after ultrasound treatment, indicating that the ultrasound irradiation process is a successful pre-treatment step to improve the biodegradability of cephalexin solution. The influences of ultrasound power and pH value on the degradation of cephalexin were studied. It was found that the optimal ultrasound power for cephalexin degradation in the system was 200 W and the rate of cephalexin degradation was maximal in the pH range of 6.5 to 8.5. The degradation kinetics of cephalexin in aqueous solution under various operational conditions was also investigated. It was found that the degradation of cephalexin follows a pseudo-first order kinetics. <![CDATA[<b>Functionalised natural zeolite and its potential for treating drinking water containing excess amount of nitrate</b>]]> An excess level of nitrate in drinking water is responsible for methemoglobinemia, or 'blue baby' disease. Consequently, management of nitrate in drinking water is universally of public health interest. In this study, clinoptilolite functionalised with cationic surfactant hexadecyltrimethyl ammonium (HDTMA) was used for the removal of nitrate from drinking water. The effects of surfactant loading, adsorbent dosage, pH, coexisting ions, temperature and environmental water quality on the adsorption of nitrate were investigated. It was found that adsorption was optimum when the initial concentration of the functionalising surfactant was 3 000 mg·l-1. An increase in adsorbent dosage raised the percentage removal of nitrate. The valency of the coexisting anion had a major effect on nitrate removal, with the presence of phosphate (a trivalent anion) leading to the lowest removal ability. Temperature and pH had negligible effects on adsorbent performance. Environmental water samples (natural groundwater samples from Limpopo Province, South Africa) were tested and it was found that the World Health Organisation (WHO) regulatory compliance can be achieved even when the initial concentration of nitrate exceeds 300 mg·l-1. Equilibrium data was modelled using the Freundlich and Langmuir isotherms and the data conformed well to the Freundlich isotherm, indicating the heterogeneous nature of the active sites. Kinetically, nitrate adsorption was best described by the pseudo-second rate equation. <![CDATA[<b>The fundamental mechanism of aqueous contaminant removal by metallic iron</b>]]> Contaminant co-precipitation with continuously generated and transformed iron corrosion products has received relatively little attention in comparison to other possible removal mechanisms (adsorption, oxidation, precipitation) in Fe0/H2O systems at near neutral pH values. A primary reason for this is that the use of elemental iron (Fe0) in environmental remediation is based on the thermodynamic-founded premise that reducible contaminants are potentially reduced while Fe0 is oxidised. However, co-precipitation portends to be of fundamental importance for the process of contaminant removal in Fe0/H2O systems, as the successful removal of bacteria, viruses and non reducible organic (e.g. methylene blue, triazoles) and inorganic (e.g. Zn) compounds has been reported. This later consideration has led to a search for the reasons why the importance of co-precipitation has almost been overlooked for more than a decade. Three major reasons have been identified: the improper consideration of the huge literature of iron corrosion by pioneer works, yielding to propagation of misconceptions in the iron technology literature; the improper consideration of available results from other branches of environmental science (e.g. CO2 corrosion, electrocoagulation using Fe0 electrodes, Fe or Mn geochemistry); and the use of inappropriate experimental procedures (in particular, mixing operations). The present paper demonstrates that contaminant co-precipitation with iron corrosion products is the fundamental mechanism of contaminant removal in Fe0/H2O systems. Therefore, the 'iron technology' as a whole is to be revisited as the 'know-why' of contaminant removal is yet to be properly addressed. <![CDATA[<b>Endocrine disrupting chemicals (phenol and phthalates) in the South African environment</b>: <b>a need for more monitoring</b>]]> There has been increasing concern about the impacts of exposure to chemical compounds with endocrine disrupting activities in the environment, especially aquatic environments, to wildlife and humans. South Africa is known to have used and abused most chemicals listed by developed and developing countries as endocrine-disrupting chemicals. Endocrinedisrupting chemicals have been reported in water, sediment and serum, as well as in fish tissue samples, at a level that could trigger endocrine disruption in humans and wildlife. Although some monitoring has been reported, particularly in water systems within the country, information on EDCs in other environmental matrices is scanty. The water systems monitored so far are very few. The strongest economy in Africa, and an emerging world economy depending on agriculture, mining, manufacturing and industry, needs to focus more on monitoring and to strengthen government organs and institutions to monitor and ensure environmental safety. <![CDATA[<b>Winde (2010) Uranium pollution of the Wonderfonteinspruit, 1997-2008</b>]]> There has been increasing concern about the impacts of exposure to chemical compounds with endocrine disrupting activities in the environment, especially aquatic environments, to wildlife and humans. South Africa is known to have used and abused most chemicals listed by developed and developing countries as endocrine-disrupting chemicals. Endocrinedisrupting chemicals have been reported in water, sediment and serum, as well as in fish tissue samples, at a level that could trigger endocrine disruption in humans and wildlife. Although some monitoring has been reported, particularly in water systems within the country, information on EDCs in other environmental matrices is scanty. The water systems monitored so far are very few. The strongest economy in Africa, and an emerging world economy depending on agriculture, mining, manufacturing and industry, needs to focus more on monitoring and to strengthen government organs and institutions to monitor and ensure environmental safety.