Scielo RSS <![CDATA[Water SA]]> http://www.scielo.org.za/rss.php?pid=1816-795020090005&lang=en vol. 35 num. 5 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Biological sulphate reduction with primary sewage sludge in an upflow anaerobic sludge bed (UASB) reactor</b><b> - </b><b>Part 1: Feasibility study</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500001&lng=en&nrm=iso&tlng=en This paper describes a novel system for the biological sulphate reduction (BSR) of acid mine drainage (AMD) using primary sewage sludge (PSS) as carbon source in an upflow anaerobic sludge bed (UASB) reactor configuration. A UASB reactor was operated at a temperature of 35ºC and it received PSS (1 875 mgCOD/ℓ) augmented with sulphate (1 500 mgSO4(2-)/ℓ). The experimental results indicate that high treatment efficiency was achieved at more than 90% sulphate reduction at a liquid hydraulic retention time (HRT) of 13.5 h. In this study, the effects of various operational parameters were also investigated. The effect of a biomass recycle stream from the top to the bottom of the sludge bed was found to initiate rapid BSR from the bottom of the bed. Profile tests showed that effective and immediate sulphate reduction was achieved as soon as the influent entered the reactor. From these results, it can be concluded that the UASB configuration using PSS as energy source would be a viable method for the BSR of AMD. <![CDATA[<b>Biological sulphate reduction with primary sewage sludge in an upflow anaerobic sludge bed (UASB) reactor</b><b> - </b><b>Part 2: Modification of simple wet chemistry analytical procedures to achieve COD and S mass balances</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500002&lng=en&nrm=iso&tlng=en The use of the conventional COD method to measure sulphide proved to be problematic due to the loss of hydrogen sulphide (H2S) during sample handling. For calibration of models based on mass balances, and operation of full-scale systems, it was imperative to develop simple wet chemistry analytical procedures for the accurate measurement of parameters like sulphide, COD, alkalinities and VFA in order to monitor BSR systems and achieve 100% COD and S mass balances. Three different analytical methods were investigated to minimise the loss of un-dissociated H2S. Method 1, which is the recommended Standard Methods COD test method, resulted in poor S mass balance (64-75%) due to loss of H2S during sample handling, mainly vacuum filtration. Method 2, in which 3 drops of 10 M NaOH are added immediately upon effluent sample collection to raise the pH to > 10 and converting un-dissociated H2S species into the HS- species resulted in minimal sulphide loss during sample vacuum filtration, dilution, mixing and standing. Method 3, in which a polyelectrolyte is added to the effluent sample to coagulate the organic particles with centrifugation for solid-liquid separation instead of vacuum filtration. Results from Method 3 showed an improvement in the S mass balance with respect to Method 1 - 91% against 75% without a long sample standing period and 88% against 65% with a long sample standing period. However, S mass balance with Method 3 was still relatively low when compared with Method 2 (86 to 91% against 92 to 95%). Therefore, Method 2 was the best simple wet chemistry analytical procedure to accurately measure S T (= H2S + HS-) and achieve close to 100% COD and S mass balances. The effects of S T loss were also investigated on the total and subsystem alkalinities as determined with the 5-pH point titration method. By testing standard solutions with known carbonate, acetate and sulphide species and upflow anaerobic sludge bed (UASB) reactor effluent samples, it was found that the total alkalinity concentration is not affected by H2S (and CO2) loss as the subsystem alkalinities re-speciate due to a change in pH; and to obtain accurate H2CO3* alk and volatile fatty acid (VFA) concentrations, accurate sulphide concentrations are required, i.e. those obtained from Method 2. <![CDATA[<b>Biological sulphate reduction with primary sewage sludge in an upflow anaerobic sludge bed (UASB) reactor</b><b> - </b><b>Part 3: Performance at 20°C and 35°C</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500003&lng=en&nrm=iso&tlng=en The performance of 2 biological sulphate reduction (BSR) upflow anaerobic sludge bed (UASB) reactors fed primary sewage sludge (PSS) and sulphate, one at 20ºC (R2) and one at 35ºC (R1) is described. To maintain the effluent sulphate concentration below 250 mgSO4(2-)/ℓ, the hydraulic retention time (HRT) and bed solids retention time (SRT or sludge age) both needed to be longer and the feed primary sewage sludge (PSS) COD to SO4(2-) ratio higher at 20ºC than at 35ºC, viz. 20.4 to 21.0 h, 24 d and 1.75 gCOD/gSO4(2-) at 20ºC and 16.4 to 17.0 h, 21 d and 1.75 gCOD/gSO4(2-) at 35ºC respectively. The longer HRT, SRT and higher feed PSS COD/ SO4(2-) ratio is a consequence of a slower PSS hydrolysis/acidogenesis rate at 20ºC resulting in a lower biodegradable particulate organics conversion to volatile fatty acids (VFA). Solid liquid separation in both systems was good yielding average particulate and soluble organic COD concentrations of (150 and 100 mgCOD/ℓ for R1; 138 and 96 mgCOD/ℓ for R2). The sulphate reduction was >90% in both systems. The UASB reactor R1 (at 35ºC) was also operated at an increased influent sulphate concentration (1 800 mgSO4(2-)/ℓ) to investigate the inhibition effect by un-dissociated hydrogen sulphide generated from the reduction of this high sulphate concentration. It was found that a high sulphate reduction (~ 92%) was maintained even at the relatively low HRT of 18.5 h. The COD and S mass balances above 95% were achieved over both systems indicating that the performance data obtained from them is reliable for developing and calibrating mathematical models. <![CDATA[<b>Biological sulphate reduction with primary sewage sludge in an upflow anaerobic sludge bed (UASB) reactor -Part 4</b>: <b>Bed settling characteristics</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500004&lng=en&nrm=iso&tlng=en The success of the UASB reactor depends largely on the settling properties and stability of the sludge bed which comprises the anaerobic active biomass. The solid-liquid separation behaviour of the sludge bed in 2 UASB reactors (R1 at 35ºC and R2 at 20ºC) fed with primary sewage sludge and sulphate was investigated because this appeared to be a retention time-defining feature of the system. Consequently, the settling rate of the various solids fractions in the sludge was measured in a settleometer to determine if bed expansion or sludge settleability was the capacity-limiting process. It was found that both sludges settled well and at an upflow velocity of up to 1.16 m/h 99% of the total sludge mass was retained. This upflow velocity was 9.1 and 13.7 times higher than the maximum operating upflow velocity of UASB reactors R1 (0.127 m/h) and R2 (0.085 m/h) respectively that caused system failure. Tests were also done to demonstrate the effect of upflow velocity (Vup) on the sludge bed expansion. Relative to the settled sludge volume at zero upflow, the R1 sludge expanded 1.8 times at a Vup of 0.127 m/h while R2 sludge expanded 2.0 times at a Vup 0.085 m/h. From the tests, R1 (35ºC) sludge had a better settleability and expanded less compared to R2 (20ºC) sludge for the same applied upflow velocity. Because in operating R1 and R2, the bed volume was kept constant, the mass of sludge removed from the system correspondingly increased as upflow increased and the bed expanded, causing a reduced sludge age and sludge bed mass to mediate the bioprocesses. It was concluded that the system failure was caused by bed expansion rather than by the sludge settleability. <![CDATA[<b>Analogous simulation of nutrient transformation processes in stream sediments</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500005&lng=en&nrm=iso&tlng=en The main transformation processes effected by the natural microbial consortium of upper Iskar River with predominant participation of sediment biofilm were simulated in the laboratory by the use of portable devices (chambers). The dynamics of real heterotrophic respiration, organic matter oxidation, denitrification and ammonification were analysed by oxygen depletion, reduction of chemical oxygen demand, nitrate uptake and ammonium accumulation, under the conditions prevailing during high and low flow periods. The experimental results showed fast oxygen consumption and high process rates - indicators for intensive respiration by a heterotrophic microbial consortium and good functioning of the ecosystem component studied. The nitrogen transformations occurred at slower rates but in mutual dynamic balance and their simultaneous realisation was due to precise, adaptive division in time and space. <![CDATA[<b>Evaluation of modifications to a physicochemical method for determination of readily biodegradable COD</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500006&lng=en&nrm=iso&tlng=en In the Mamais-Jenkins-Pitt method for determination of readily biodegradable COD (S S), 2 alternatives were proposed for the intermediate determination of soluble inert COD (S I). When a full-scale treatment plant exists, influent S I = effluent truly soluble COD. When there is no full-scale plant, then the truly soluble COD of the effluent of a 24 h fill-and-draw batch reactor treating the wastewater is taken as influent S I. In this study, both S I methods were statistically compared on 24 wastewater samples from 2 municipal wastewater treatment plants (WWTPs). While average S I obtained for the 2 methods was the same, individual samples usually had very different S I values. In fact, virtually no correlation was found between the 2 methods. Also, the S S values obtained using both S I alternatives were statistically compared. A good correlation was observed, in spite of the poor S I correlation - low, dispersed S I values did not seriously affect the correlation between both S S determinations. A method was proposed for determination of the limit of detection and the limit of quantification (LOQ) for both S S methods. The LOQ resulted in 28.6 mg/l and 32.6 mg/l, respectively, for the full-scale and the laboratory-scale alternatives. Some assumptions of the original laboratory-scale (LS) method could potentially be sources of error in S I determination. Two modifications to the laboratory-scale method were implemented in order to avoid these potential problems: Washing biomass with tap water, and correcting S I in the fill-and-draw reactor by the S I of the original biomass suspension. These method modifications were tested on wastewater samples from the mentioned WWTPs. The fundamentals and results of both modifications are discussed in this paper, as well as the imprecision associated with estimating influent S I from effluent CODsol in all studied methods, and its impact on S S determination. <![CDATA[<b>The influence of land use on water quality and diatom community structures in urban and agriculturally stressed rivers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500007&lng=en&nrm=iso&tlng=en Epilithic diatom communities offer a holistic and integrated approach for assessing water quality as they remain in one place for a number of months and reflect an ecological memory of water quality over a period of time. The objective of this study is to use diatom assemblages to distinguish between particular land types and associated water quality impacts that are linked to these land-use patterns. Water quality and diatom community data were collected from sites in the Crocodile and Magalies Rivers (Gauteng and North West Province, South Africa) associated with agricultural, urban and natural (reference) adjacent land use respectively. The data collected were subjected to multivariate statistical techniques to analyse spatial and temporal patterns in water quality (principal component analysis) and diatom community structures (non-metric multidimensional scaling) to elucidate hypothesised differences in community structure per land-use type. Five diatom response indices (Generic Diatom Index, Specific Pollution Sensitivity Index, Biological Diatom Index, Eutrophication/Pollution Index and Percentage Pollution Tolerant Valves) incorporated in the OMNIDIA software were implemented to assess the integrity of diatom communities per land-use type. Principle component ordination of water quality describes 56.6% of the variation in data observed, and indicates the separation of reference sites from test sites for low and high flow conditions combined. It was, however, not possible to distinguish between the agricultural and urban land-use sites using PCA based on water quality data. One-way ANOSIM showed a significant difference (p < 0.05) between reference groups, agricultural groups and urban groups, with no significant differences noted (p > 0.05) between groups made up of sites exhibiting the same land-use patterns. Diatom indices showed that agricultural sites were in a slightly more modified ecological state than urban sites overall. Based on the species similarity (SIMPER analyses), reference sites showed strong associations with Achnanthes minutissima, Gomphonema venusta and Cocconeis placentula var. euglypta, whilst urban sites were associated with Diatoma vulgaris, Navicula tripunctata and Amphora pediculus. Agriculture could be separated into high- and low-intensity practices based on species composition. Sites where high-intensity agriculture took place were dominated by motile species of the genus Nitzschia, and low-intensity agriculture was indicated by motile species of the genus Navicula. Urban sites contained a combination of species that were tolerant of spikes in water quality. <![CDATA[<b>Morphological abnormalities of diatom silica walls in relation to heavy metal contamination and artificial growth conditions</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500008&lng=en&nrm=iso&tlng=en Teratological forms of diatoms are non-adaptive phenotypic abnormalities caused by various environmental stresses. Heavy metal contamination and artificial growth conditions are the best known causes. In fact, the recording of abnormal cells in a diatom population or community can give both a temporal and quantitative indication of heavy metal contamination of water bodies. Moreover, long-term cultures generally present a high percentage of abnormal cells due to the scarcity of nutrients, presence of waste products and osmotic pressure. The aim of this paper is to classify and provide photographic documentation and descriptions of all known teratologies occurring in the most widespread freshwater diatom genera. <![CDATA[<b>Conveyance estimation in channels with emergent bank vegetation</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500009&lng=en&nrm=iso&tlng=en Emergent vegetation along the banks of a river channel influences its conveyance considerably. The total channel discharge can be estimated as the sum of the discharges of the vegetated and clear channel zones calculated separately. The vegetated zone discharge is often negligible, but can be estimated using established methods if necessary. The clear channel discharge can be estimated either through application of a resistance equation using a composite resistance coefficient, or by integration of the transverse distribution of the depth-averaged velocity. Recommendations are made for estimating the composite resistance coefficient, and the coefficient for the vegetation interface. An equation for the integrated velocity distribution is also presented, together with a procedure for its application. The methods reliably reproduce resistance coefficients and conveyances measured in laboratory channels. <![CDATA[<b>The simple modelling method for storm- and grey-water quality management applied to Alexandra settlement</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500010&lng=en&nrm=iso&tlng=en Discharges from informal settlements cause numerous adverse water quality impacts on urban areas and on receiving waters. These problems reflect local conditions with respect to economic development, level of environmental protection (including the associated infrastructure), institutional arrangements and public awareness. Development of comprehensive tools for selection of drainage management interventions, even at planning levels, is still at its early stages in South Africa. Municipalities in South Africa face many challenges in identifying, assessing and selecting the right interventions and/or strategies to address the impacts of land use on receiving waters. A spreadsheet-based model was developed in this study specifically to assist in identifying, selecting and evaluating interventions to manage storm- and grey-water quality. The model also consists of modules: to quantify water quality management objectives (load reduction targets) of pollutants of concern, to formulate implementation strategies by combining different mixes of interventions at different levels of implementation, and to cost and select the optimum management strategy. In the Alexandra settlement investigated, the identified interventions to achieve management objectives optimally consist of educational programmes, erosion and sediment control, street sweeping, removal of sanitation system overflows, impervious cover reduction, downspout disconnections, removal of illicit connections to storm drains, establishment of riparian buffers, use of rainwater tanks and exfiltration systems. <![CDATA[<b>Heavy daily-rainfall characteristics over the Gauteng Province</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500011&lng=en&nrm=iso&tlng=en Daily rainfall over the Gauteng Province, South Africa, was analysed for the summer months of October to March using 32-yr (1977 to 2009) daily rainfall data from about 70 South African Weather Service stations. The monthly and seasonal variation of heavy rainfall occurrences was also analysed. Three 24-h heavy rainfall classes are defined considering the area-average rainfall. A significant rainfall event is defined when the average rainfall exceeds 10 mm, a heavy rainfall event when the average rainfall exceeds 15 mm and a very heavy rainfall event when the average rainfall exceeds 25 mm. January months have the highest monthly average rainfall as well as the highest number of heavy and very heavy rainfall days. The month with the second-highest number of heavy and very heavy rainfall days is February followed by March and October. December has the second-highest monthly average rainfall and the most days with rain. However, it is also the month with the lowest number of heavy and very heavy rainfall days. The highest 24-h rainfall recorded at a single station during the 32-yr period was 300 mm in December 2006. However, rainfall exceeding 115 mm at a single rainfall station in the Gauteng Province is very rare and does not occur every year. January months receive these events more than any other month but this only transpires in approximately a third of years. The central and north-western parts of the Province experience the most events where the rainfall at a single station surpasses 75 and 115 mm. With regard to seasonal rainfall, the 1995/96 summer rainfall season had the highest seasonal rainfall during this 32-yr period followed by the 1999/2000 season. The 1995/96 season had above normal rainfall in both early and late summer but the 1999/2000 season was dry in early summer and very wet in late summer. Significantly high seasonal rainfall is associated with above-normal rainfall in late summer. <![CDATA[<b>Quantifying rainfall-runoff relationships on the Melkassa Hypo Calcic Regosol ecotope in Ethiopia</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500012&lng=en&nrm=iso&tlng=en Droughts, resulting in low crop yields, are common in the semi-arid areas of Ethiopia and adversely influence the well-being of many people. The introduction of any strategy that could increase yields would therefore be advantageous. The objective of this study was to attempt to assess the influence of in-field rainwater harvesting (IRWH), compared to conventional tillage, on increasing the amount of water available to a crop like maize on a semi-arid ecotope at Melkassa situated in the eastern part of the Rift Valley. To achieve the objective of the study rainfall-runoff measurements were made during 2003 and 2004 on 2 m x 2 m plots provided with a runoff measuring system and replicated 3 times for each treatment. There were 2 treatments: conventional tillage (CT) on which hand cultivation was practised in a way that simulated the normal local CT; and a flat surface simulating the no-till, undisturbed surface of the IRWH technique (NT). Rainfall-runoff measurements were made over 2 rainy seasons during which there were 25 storms with > 9 mm of rain. From the 25 storms, only the 2nd season storms (8 storms) had runoff measurements. These storms were used for calibration and validation of the Morin and Cluff (1980) runoff model (MC Model). Appropriate values for final infiltration rate (If), surface storage (s) and for the crusting parameter (γ) were found to be: 6 mm·h-1; 1.0 mm for NT and 6.0 mm for CT; 0.6 mm-1, respectively. The measured runoff (R) for the 2004 rainy season expressed as a fraction of the rainfall during the measuring period (P), i.e. R/P, gave values of 0.59 and 0.40 for the NT and CT treatments, respectively. There was a statistical difference between the runoff on the 2 treatments. Selected results from 7 years of field experiments with IRWH at Glen in South Africa were used together with measured maize yields and climate data over 16 seasons on the nearby Melkassa Experiment Station to estimate the yield benefits of IRWH compared to CT on the ecotope studied. The results ranged between 35 and 1 437 kg with a mean of 711 kg·ha-1 over the 16 years. At Melkassa this was an estimated yield increase ranging from 13% to 49%. The mean increase was 33%. <![CDATA[<b>Evaluation of potential changes in hydrologically relevant statistics of rainfall in Southern Africa under conditions of climate change</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500013&lng=en&nrm=iso&tlng=en Scenarios of present, intermediate and future climates for Southern Africa were analysed to evaluate potential changes in hydrologically relevant statistics of rainfall that could be observed this century as a result of climate change. These climate scenarios were developed in previous studies by applying empirical downscaling techniques to relatively coarse-scale climate scenarios simulated by general circulation models (GCMs) as part of the Intergovernmental Panel on Climate Change 3rd and 4th Assessment Reports (TAR and AR4, respectively). The regional climate scenarios were available at a daily time-step and for a spatial grid resolution of 0.25º over Southern Africa, comprising South Africa, Lesotho and Swaziland. In the study, the regional climate scenarios were related to the 1946 quaternary catchments in the region since the possible hydrological impacts of climate change will ultimately be assessed explicitly by applying the regional climate scenarios in a daily time-step hydrological model. The analysis of potential changes in hydrologically relevant rainfall statistics was qualitative in nature and focused on determining where convergence exists amongst the different climate models with respect to changes in rainfall, and what the likely hydrological implications would be for the region. According to all of the GCMs evaluated in the study, more rainfall is projected for the east of the region. The greater rainfall projected for the east would be in the form of more rain days and more days with bigger rainfalls. If these scenarios are correct, the combination of wetter antecedent conditions and larger rainfall events would result in more runoff being generated and this would have implications for, inter alia, filling of dams and water quality. According to all of the GCMs evaluated, less rainfall is projected along the west coast and the adjacent interior, with the possibility of a slight increase in inter-annual variability. If correct, this would result in a decrease in flows and an increase in flow variability, since changes in precipitation are amplified in the hydrological cycle. As convergence in climate-change scenarios becomes apparent, there is now an arguable basis for developing appropriate response strategies for incorporation into adaptation policy. Perhaps one of the greatest challenges in this regard is now to explore the issues of uncertainty and probability in order to develop a more rigorous basis to enable proactive responses. <![CDATA[<b>Is Groenvlei really fed by groundwater discharged from the Table Mountain Group (TMG) Aquifer?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500014&lng=en&nrm=iso&tlng=en Vankervelsvlei is a unique wetland located in the stabilised dunes east of Sedgefield. Groenvlei is one of a series of 5 brackish coastal lakes along the Southern Cape coast of South Africa, but is the only one disconnected from the sea. It has been hypothesised that discharge from the underlying Table Mountain Group Aquifer sustains Vankervelsvlei, which in turn discharges into Groenvlei. This paper critically reviews the conceptual model and information on which the hypothesis was based. It is argued that the conceptual model is flawed as it does not take account of topographical and geohydrological conditions prevalent in the area. Analysis of limited hydrochemical data did not explore other possible water sources, and the electrical conductivity characteristics used to confirm the link between the wetlands and the deeper secondary aquifer also apply to 56.3% of boreholes located in a variety of aquifer types across the Western Cape Province. No information is available that supports a link to the Table Mountain Group. Rather, it appears that Vankervelsvlei is sustained by direct rainfall and there is no hydraulic link between Vankervelsvlei and Groenvlei. <![CDATA[<b>Comparison of GRACE with <i>in situ</i> hydrological measurement data shows storage depletion in Hai River basin, Northern China</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500015&lng=en&nrm=iso&tlng=en Water storage change has implications not only for the hydrological cycle, but also for sustainable water resource management in especially semi-arid river basins. Satellite/remote sensing techniques have gained increasing application in monitoring basin and regional hydrological processes in recent decades. In this study, the latest version of GRACE (Gravity Recovery and Climate Experiment) is used to estimate total water storage change in the Hai River basin (HRB) of Northern China for the period January 2003 to December 2006. Time-series comparisons show a good agreement between the estimated storage change from the GRACE satellite data and in situ hydrological measurement data at especially the seasonal cycle with R = 0.82 and RMSE = 17.25 mm. The good agreement suggests that GRACE detects storage change in the 318 866 km² HRB study area. It also implies that the in situ hydrological measurements of soil moisture and groundwater sufficiently characterise storage change in the semi-arid river basin. Change in soil moisture storage is less than that in saturated storage, suggesting that storage depletion in the basin is mainly in the saturated zone. Both the GRACE and hydrological measurement data indicate storage loss in the range of 12.72 to 23.76 mm/yr - a phenomenon that has been detected in previous studies in the basin. GRACE hydrology data could therefore be handy in monitoring storage dynamics and water availability in the study area. As GRACE data are available for virtually every region of the world, their application in conjunction with hydrological models could improve hydrological studies. This may lead not only to water balance closures, but also to sustainable water resource management at basin to regional scale. <![CDATA[<b>Has monitoring failed the Olifants River, Mpumalanga?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500016&lng=en&nrm=iso&tlng=en Water quality monitoring in the Olifants River catchment, Mpumalanga, is evaluated using river water dissolved sulphate levels, one of the best indicators of pollution related to acid mine drainage. Assessment of long-term water quality records shows that monitoring has not been carried out systematically. In that it fails one of the most fundamental criteria of good environmental monitoring practices. At some monitoring stations sampling frequency has been scaled down from approximately weekly to monthly intervals over time, despite evidence for increasing and problematic levels of pollution. At the Loskop Dam dissolved sulphate levels have increased more than 7-fold since the 1970s evidently due to increasing levels of pollution within the Little Olifants River catchment. At 4 of the 7 long-term monitoring stations river water sulphate levels exceed the 100 mg/ℓ threshold value for aquatic ecosystem health most of the time for the duration of the record, and all of the time since about 2001. At these stations river water sulphate levels also exceed the 200 mg/ℓ threshold for human consumption 27 to 45% of the time, for the duration of the long-term record. These observations necessitate more frequent and improved monitoring, not evidently reduced efforts. A major concern is the location of a recently re-opened copper mine outside Phalaborwa, just upstream from the confluence of the Ga-Selati River and the Olifants River. Levels of copper sulphate, highly toxic to aquatic species, should be urgently investigated as a probable cause of recent fish and crocodile deaths in the Kruger National Park. In river systems subject to intensive mining activity, such as the Olifants River, toxic constituents such as copper, arsenic, chrome-VI, etc., currently not routinely measured by the Department of Water Affairs (DWA) need to be included in monitoring efforts as a matter of urgency. This will require drastic improvements in current water quality monitoring efforts, including the acquisition of modern analytical instrumentation. <![CDATA[<b>Who uses the fishery resources in South Africa's largest impoundment? Characterising subsistence and recreational fishing sectors on Lake Gariep</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500017&lng=en&nrm=iso&tlng=en The African Union's prioritisation of inland fisheries as an investment area for poverty alleviation and regional economic development will require the development of management plans. These should be based on sound knowledge of the social dynamics of the resource users. In South Africa the social dynamics of resource users of inland fisheries have never been assessed. The purpose of this study was to assess the human dimensions of the anglers utilising the fishery in Lake Gariep, South Africa's largest impoundment. The study was based on 357 first-time interviews conducted on the lakeshore between October 2006 and December 2007. Anglers were categorised as recreational (39%) or subsistence (61%) based on their residency, occupation, primary motivation for angling, mode of transport and gear use. Subsistence anglers were local (99%), residing within 10 km of the place where they were interviewed, while recreational anglers included both local resident and non-resident members. The racial composition of anglers was dependent on user group and differed significantly (p < 0.05) from the demographic composition of the regional population. Recreational anglers were predominantly White (> 60% of interviews) and Coloured (> 25%), while 84% of subsistence anglers were Coloured and 16% Black African. Most recreational anglers had permanent employment or were pensioners while <30% of subsistence anglers were permanently employed. Most recreational users (82%) accessed the lake with their own vehicle while subsistence anglers mainly walked (63%) or used a bicycle (28%). Recreational interviewees either consumed (59%), sold (11%), gave away (10%) or released (20%) some of their catch. Subsistence anglers either ate their catch (53%) and/or sold (41%) their catch. Within the subsistence sector no anglers released fish after capture or gave some of the catch away. We conclude that this inland fishery contributes to the livelihood of the rural poor who use the lake on a subsistence basis and that recreational-angler based tourism may contribute to increased income and employment opportunities through related service industries. <![CDATA[<b>Is there a role for traditional governance systems in South Africa's new water management regime?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500018&lng=en&nrm=iso&tlng=en The transition to democracy in South Africa in 1994 catalysed new forms of governance in all sectors of society including water resource management. This paper examines the extent to which traditional governance systems have been acknowledged and incorporated into these new water management institutions and approaches. The research focused on understanding the cultural, religious and customary practices and rules relevant to water resource management as well as the roles of traditional leaders in 2 water user associations in the Eastern Cape Province. Findings from the research reveal that both state governance systems and traditional governance systems are relevant to water resource management in the study areas. However, management is predominantly guided by state-driven strategies which are based on statutory legal systems. Yet, traditional governance systems, including customary laws and cultural and religious practices, have an important role to play in achieving the purposes of the water user associations. Failure to acknowledge and incorporate aspects of these traditional governance systems may undermine the ability of government to achieve the objectives of the National Water Act. <![CDATA[<b>A detailed analysis of evolution of water rights in South Africa</b>: <b>an account of three and a half centuries from 1652 AD to present</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500019&lng=en&nrm=iso&tlng=en This study reviews the changing scene of water rights in South Africa over the last three and a half centuries and concludes that they have come full circle, with some modifications, since the invoking of Dutch rule in the Cape in 1652 AD. The study stipulates that adoption of a modern rights structure is a welcome change and a progressive step taken by the democratic government; however, its success depends to a great extent on the institutional efficiency of the state which performs the role of trustee or custodian of the water resource. The responsibilities of trusteeship with respect to managing water rights or permits are met through a decentralised decision-making system. The management of water rights/permits thus depends on the administrative and judicial efficiency of organisations and government departments. Therein lurks the danger of corruption, bureaucratic inefficiency, and insecurity of permits, and hence enough potential to stifle the long-term incentives to invest in the water sector. <![CDATA[<b>Distribution and habitats of <i>Melanoides tuberculata </i>(Müller, 1774) and <i>M. victoriae </i>(Dohrn, 1865)(Mollusca: Prosobranchia: Thiaridae) in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500020&lng=en&nrm=iso&tlng=en An account is given of the geographical distribution and habitats of Melanoides tuberculata (Müller, 1774) and M. victoriae (Dohrn, 1865) as reflected by the samples on record in the database of the National Freshwater Snail Collection (NFSC) of South Africa. About 30 species of Melanoides occur in Africa of which only M. tuberculata is widespread. Melanoides tuberculata is also indigenous to India and the south-east Asian mainland to northern Australia and was widespread in the present-day Sahara during the late Pleistocene-Holocene, but M. victoriae seems to be restricted to Southern Africa. Details of the habitats on record for each species, as well as mean altitude and mean annual air temperature and rainfall for each locality, were processed to determine chi-square and effect-size values. An integrated decision-tree analysis indicated that temperature, altitude and type of substratum were the most important factors of those investigated that played a significant role in establishing the geographical distribution of these species in South Africa. In view of the fact that M. tuberculata can serve as intermediate host for a number of trematode species elsewhere in the world, it is recommended that the ability of the 2 local Melanoides species to act as intermediate hosts should be investigated. Due to the fact that the majority of sites from which these species were recovered were not since revisited, it is recommended that efforts should be made to update their geographical distribution and the results compared with the data in the database. The conservation status of these 2 species and the possible influence of global warming and climatic changes on their geographical distribution are briefly discussed. <![CDATA[<b>Nitrate-nitrogen removal with small-scale reverse osmosis, electrodialysis and ion-exchange units in rural areas</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500021&lng=en&nrm=iso&tlng=en The nitrate-nitrogen concentration in water supplied to clinics in Limpopo Province is too high to be fit for human consumption (35 to 75 mg/ℓ NO3-N). Therefore, small-scale technologies (reverse osmosis, ion-exchange and electrodialysis) were evaluated for nitrate-nitrogen removal to make the water potable (< 10 mg/ℓ NO3-N). It was found that the reverse osmosis process should function well for nitrate-nitrogen removal. Nitrate-nitrogen could be reduced from a concentration of 35 to 43 mg/ℓ in 1 case to a concentration of between 1.4 and 5.5 mg/ℓ in the treated water. In another case it could be reduced from 54 to 72 mg/ℓ to 12 to 17 mg/ℓ in the treated water. The water was also effectively desalinated. The ion-exchange process could also reduce the nitrate-nitrogen concentration to less than 10 mg/ℓ in the treated water. However, the water could not be efficiently desalinated and the process should function better when the level of total dissolved solids in the feed is not very high. The electrodialysis process should also function well for nitrate-nitrogen and salinity removal. However, the electrodialysis process is more complicated to operate. The reverse osmosis and ion-exchange processes are therefore suggested for nitrate-nitrogen removal at clinics. Capital costs for small-scale reverse osmosis and ion-exchange units are estimated at ZAR7 000 and ZAR10 000, respectively. Operational costs for reverse osmosis and ion-exchange are estimated at ZAR3.16/m³ and ZAR3.60/m³ of treated water, respectively. <![CDATA[<b>Cyclodextrin-ionic liquid polyurethanes for application in drinking water treatment</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500022&lng=en&nrm=iso&tlng=en The prevalence of toxic contaminants in water remains a huge challenge for water-supplying companies and municipalities. Both organic and inorganic (especially heavy metals) pollutants are often present in water distribution networks. The presence of these contaminants in drinking water poses a major risk to human health. Organic and inorganic pollutants often co-occur in drinking water networks. However, at present there is no water treatment intervention that simultaneously removes both organic and inorganic pollutants from water to desirable levels. In our laboratories, recent studies have shown that both functionalised and un-functionalised cyclodextrin (CD) polymers are capable of removing organic pollutants from water, with the functionalised CD polymers showing an enhanced absorption capability. Ionic liquids (ILs), on the other hand, have been reported to absorb heavy metals from aqueous media. In this paper, we report on the synthesis of several cyclodextrin-ionic liquid (CD-IL) polymers, a dual system capable of removing both organic and inorganic pollutants from water. This system has been tested and has proved to possess excellent capabilities for the removal of model pollutants such as p-nitrophenol (PNP), 2,4,6-trichlorophenol (TCP) and chromium (Cr6+) from aqueous media. <![CDATA[<b>Nitrosamines</b>: <b>a review on their prevalence as emerging pollutants and potential remediation options</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500023&lng=en&nrm=iso&tlng=en This review provides an overview of the current state of knowledge on the prevalence of nitrosamines in drinking water, especially nitrosodimethylamine (NDMA), and discusses published research on the detection, mechanisms of formation, and removal of nitrosamines. While the number of published reports in the South African context is very limited, this review also attempts to contextualise and report specifically on the challenges for South Africa. Besides direct industrial or human-derived contamination, nitrosodimethylamine can be formed through a chemical reaction between monochloroamine and an organic-based compound such as dimethylamine which is frequently detected in surface water. It has been suggested that chloramination of surface waters with a high concentration of dissolved organic carbon (DOC) could result in elevated NDMA formation. Growing evidence suggests that NDMA occurs more frequently and at higher concentrations in drinking water systems that practise chloramination compared to systems that use chlorination. <![CDATA[<b>Review of commonly used remote sensing and ground-based technologies to measure plant water stress</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500024&lng=en&nrm=iso&tlng=en This review provides an overview of the use of remote sensing data, the development of spectral reflectance indices for detecting plant water stress, and the usefulness of field measurements for ground-truthing purposes. Reliable measurements of plant water stress over large areas are often required for management applications in the fields of agriculture, forestry, conservation and land rehabilitation. The use of remote sensing technologies and spectral reflectance data for determining spatial patterns of plant water stress is widely described in the scientific literature. Airborne, space-borne and hand-held remote sensing technologies are commonly used to investigate the spectral responses of vegetation to plant stress. Earlier studies utilised multispectral sensors which commonly collect four to seven spectral bands in the visible and near-infrared region of the electromagnetic spectrum. Advances in sensor and image processor technology over the past 3 decades now allow for the simultaneous collection of several hundred narrow spectral bands resulting in more detailed hyperspectral data. The availability of hyperspectral data has led to the identification of several spectral indices that have been shown to be useful in identifying plant stress. Such studies have revealed strong linear relationships between plant pigment concentration and the visible (VIS) and near-infrared (NIR) reflectance, while plant water content has been linked to specific bands in the short-wave infrared (SWIR) region of the spectrum. Ground-truthing is essential to identifying useful reflectance information for detecting plant water stress, and four commonly used ground-based methods viz. predawn leaf water potential, leaf chlorophyll fluorescence, leaf pigment concentrations and leaf water content are reviewed for their, usefulness and practical application. <![CDATA[<b>Wetlands and invertebrate disease hosts</b>: <b>are we askin for trouble?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502009000500025&lng=en&nrm=iso&tlng=en Wetlands provide a range of benefits to society, and yet in South Africa wetlands continue to be affected by human activities. Considerable effort is now being directed towards rehabilitation of degraded wetlands and the construction of artificial systems to treat effluent and stormwater. At the same time, wetlands provide potential habitat for vectors or intermediate hosts (collectively referred to in this document as 'invertebrate disease hosts': IDHs), of parasites implicated in the transmission of such important diseases as malaria and schistosomiasis (bilharzia). The present review considers, for the 2 major IDHs (mosquitoes and schistosome-transmitting snails), the type of habitat required by the water-dependent life stage and the ways in which wetland degradation, rehabilitation and creation may affect the availability of suitable habitat. General practical measures for minimising pest species, particularly mosquitoes, are included. This review also highlights other issues that require research and testing in the South African context, including: the IDHs implicated in less well-known diseases (both of humans and animals) and the control of mosquitoes and schistosome-transmitting snails through biomanipulation. We conclude that in regions of the country where the diseases are prevalent there is the likelihood that wetland rehabilitation and creation could inadvertently encourage the IDHs responsible for transmitting malaria and schistosomiasis. Assessment of the potential risks and benefits of a proposed wetland modification needs to be undertaken in a holistic manner using an adaptive framework that recognises the critical need to balance human and environmental health. Possible ways of controlling IDHs both in an environmentally- and socio-friendly manner need to be investigated using a multi-disciplinary approach engaging invertebrate biologists, health care officials, wetland scientists and also sociologists and economists.