Browsing by Subject "Water quality"

Now showing 1 - 4 of 4
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    Open Access
    A comparison of rapid bioassessment protocols used in 2 regions with Mediterranean climates, the Iberian Peninsula and South Africa
    (2006) BONADA, NÚRIA; DALLAS, HELEN; RIERADEVALL, MARIA; PRAT, NARCÍS; DAY, JENNY
    Abstract. The ability of 2 Rapid Bioassessment Protocols (RBPs) to assess stream water quality was compared in 2 Mediterranean-climate regions. The most commonly used RBPs in South Africa (SAprotocol) and the Iberian Peninsula (IB-protocol) are both multihabitat, field-based methods that use macroinvertebrates. Both methods use preassigned sensitivity weightings to calculate metrics and biotic indices. The SA- and IB-protocols differ with respect to sampling equipment (mesh size: 1000 lm vs 250-300 lm, respectively), segregation of habitats (substrate vs flow-type), and sampling and sorting procedures (variable time and intensity). Sampling was undertaken at 6 sites in South Africa and 5 sites in the Iberian Peninsula. Forty-four and 51 macroinvertebrate families were recorded in South Africa and the Iberian Peninsula, respectively; 77.3% of South African families and 74.5% of Iberian Peninsula families were found using both protocols. Estimates of community similarity compared between the 2 protocols were .60% similar among sites in South Africa and .54% similar among sites in the Iberian Peninsula (Bray-Curtis similarity), and no significant differences were found between protocols (Multiresponse Permutation Procedure). Ordination based on Non-metric Multidimensional Scaling grouped macroinvertebrate samples on the basis of site rather than protocol. Biotic indices generated with the 2 protocols at each site did not differ. Thus, both RBPs produced equivalent results, and both were able to distinguish between biotic communities (mountain streams vs foothills) and detect water-quality impairment, regardless of differences in sampling equipment, segregation of habitats, and sampling and sorting procedures. Our results indicate that sampling a single habitat may be sufficient for assessing water quality, but a multihabitat approach to sampling is recommended where intrinsic variability of macroinvertebrate assemblages is high (e.g., in undisturbed sites in regions with Mediterranean climates). The RBP of choice should depend on whether the objective is routine biomonitoring of water quality or autecological or faunistic studies.
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    Open Access
    A determination of the effect of changing collector chain length under varying Water Quality
    (2025) Natalia Sinjani, Taonga Mchirwa; Corin, Kirsten; Manono, Malibongwe; Manenenzhe, Resoketswe
    The mineral processing industry needs to recycle process wastewater to decrease the detrimental effects of its discharge into the environment. This is of high importance in regions where water availability is restricted. Recycling process water leads to differences in water quality such as changes in pH, ionic strength (IS), and the concentration of total dissolved solids (TDS). The froth and pulp zones in the flotation cell work interactively to recover minerals and changes to water quality affect both zones. The factors affect the behavior of minerals and chemical reagents, impacting flotation performance. According to literature, collector behavior can be impacted differently by certain ions. An increase in the IS and TDS of water can result in a decrease in mineral recoveries and grades. This is due to gangue and ions that either coat or create precipitates that passivate mineral surfaces, preventing collector adsorption. However, it is also known ions are capable of activating valuable minerals and gangue. Anincrease in collector chain length leads to an increase in the strength of the collector due to an increase in hydrophobicity. However, this order of strength may be affected by pH and IS as these affect the collector adsorption. The selectivity of collectors increases with a decrease in the collector chain length. pH also affects the selectivity of collectors as an increase in pH results in a decrease in grade. However, the stability of collectors is independent of chain length. A high collector dosage may not imply an increase in flotation performance as there is a risk of over-dosage. This may result in other reagents being overpowered in the pulp, leading to decreases in grades and recoveries. The first objective of this study was to investigate the differences in flotation performance when collectors of different chain lengths are used in synthetic plant water with increasing ionic strength. The second objective was to determine the interactive effects between collector chain length, collector dosage, and ionic strength of synthetic plant water on flotation performance. To address the objectives, a two-phase factorial design of experiments was created, with Phase one utilising SEX and Phase two, SIBX. The factors selected for investigation were the collector chain length, dosage and the ionic strength of synthetic plant water. Batch f lotation on a Merensky ore was utilised to obtain copper and nickel grades and recoveries which illustrated flotation performance. Additionally, batch flotation was used to obtain the entrainment factors of the two collectors at the different ionic strengths of SPW. Zeta potential measurements on chalcopyrite were utilised to determine changes to the mineral surface potential when the factors were varied. Sedimentation tests on the tails samples of the batch flotation tests provided information on the behaviour of the fines, and UV/Vis spectroscopy determined the concentration of residual xanthates present after flotation. i The study found that the longer chained collector, SIBX, behaved atypically to what has been observed in other studies. It obtained lower solids and recoveries than SEX in water with low ionic strengths. Furthermore, under these conditions, SIBX achieved the highest copper and nickel grades. Interestingly, as the ionic strength of the water increased, the trend was reversed. The copper recoveries were independent of the changes made to all the factors, however, the nickel recoveries did show slight variations. Both an increase in the ionic strength and collector chain length resulted in a decrease in the entrainment factor. Additionally, an increase in the ionic strength resulted in a less negative zeta potential. It was determined that there were interactive effects among the factors that were varied and concluded the factor with the largest impact on the flotation response (i.e. solids and water recovery and the recovery and grades of copper and nickel) was the ionic strength of the water. These conclusions emphasise the importance of investigating the effects of recirculating water within the flotation process. The determination of the effects on flotation performance by different collectors under varying water quality will provide more knowledge into the optimisation of reagent usage in mineral processing in the presence of recycled water. Subsequently, this will provide plant operators with more control over the performance of the process as reagent control may compensate for changes in water quality.
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    Open Access
    Estimating minimum thresholds of natural vegetation for the integrated management and protection of water quality in South African catchments
    (2025) Locke, Kent; Winter, Kevin
    Despite multi-level commitments to Integrated Water Resources Management (IWRM), many of South Africa's water quality problems are attributable to the negative impacts of anthropogenic land use on water quality. Academics and policymakers have warned that unless action is taken to improve water resources management through the implementation of coordinated, proactive, and data-driven strategies, the country faces a water crisis that will have severe socio-ecological consequences. As natural vegetation acts as a sink, thus protecting water resources from diffuse pollution, the preservation of an adequate amount within catchment areas is important. However, among several pertinent questions, it is not clear (1) how much natural vegetation cover is required, (2) at which scale(s) this would be most effective, (3) how natural vegetation should be classified, and (4) whether the fragmentation of natural vegetation is a significant factor. To answer these questions, regression analysis was used to model relationships between water quality (measured using a composite pollution index) and metrics of natural vegetation (estimated from national land cover maps) at multiple scales across a sample of sub-catchments located within South Africa's Berg-Olifants, Breede-Gouritz, and Mzimvubu-Tsitsikamma Water Management Areas. Across this sample, a statistically significant, nonlinear, and inverse relationship was found between proportions of natural vegetation cover and pollution levels. This relationship was strongest (1) when natural vegetation was defined as an aggregation of indigenous woody vegetation, wetlands, and forestry plantations, and (2) when measured across the whole catchment and within a 200 m riparian buffer zone. At both scales, however, fragmentation was not found to be significant. The models further indicated that approximately 82 to 90% natural vegetation cover was necessary at these scales to keep pollution scores within acceptable levels. Additional nonlinear thresholds estimated using breakpoint analysis also suggested that if proportions of natural vegetation fall below 45% (across the whole catchment) and 60% (within a 200 m riparian buffer zone) a dramatic increase in pollution levels can be expected. The study has direct relevance for IWRM in so far as these results demonstrate (1) the critical importance of preserving areas of natural vegetation for water quality management and (2) the possibility of providing actors with quantifiable and context-specific management targets which can inform multistakeholder decision-making processes at appropriate spatial scales.
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    Open Access
    Public perception of drinking water safety in South Africa 2002-2009: a repeated cross-sectional study
    (BioMed Central Ltd, 2012) Wright, Jim; Yang, Hong; Rivett, Ulrike; Gundry, Stephen
    BACKGROUND:In low and middle income countries, public perceptions of drinking water safety are relevant to promotion of household water treatment and to household choices over drinking water sources. However, most studies of this topic have been cross-sectional and not considered temporal variation in drinking water safety perceptions. The objective of this study is to explore trends in perceived drinking water safety in South Africa and its association with disease outbreaks, water supply and household characteristics. METHODS: This repeated cross-sectional study draws on General Household Surveys from 2002-2009, a series of annual nationally representative surveys of South African households, which include a question about perceived drinking water safety. Trends in responses to this question were examined from 2002-2009 in relation to reported cholera cases. The relationship between perceived drinking water safety and organoleptic qualities of drinking water, supply characteristics, and socio-economic and demographic household characteristics was explored in 2002 and 2008 using hierarchical stepwise logistic regression. RESULTS: The results suggest that perceived drinking water safety has remained relatively stable over time in South Africa, once the expansion of improved supplies is controlled for. A large cholera outbreak in 2000-02 had no apparent effect on public perception of drinking water safety in 2002. Perceived drinking water safety is primarily related to water taste, odour, and clarity rather than socio-economic or demographic characteristics. CONCLUSION: This suggests that household perceptions of drinking water safety in South Africa follow similar patterns to those observed in studies in developed countries. The stability over time in public perception of drinking water safety is particularly surprising, given the large cholera outbreak that took place at the start of this period.