Scielo RSS <![CDATA[Water SA]]> vol. 45 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Mathematical modelling and analysis of the flocculation process in low retention time hydraulic flocculators</b>]]> This article aims to advance the understanding of particle interactions in low retention time flocculators and proposes a new flocculation model that appropriately considers the influence of retention time in flocculation processes. This consideration is important for units with flocculation time lower than 1 min, as seen in helically coiled tube flocculators (HCTFs), whose retention time is significantly lower than conventional flocculation units (about 30 min). With this, it was possible to obtain a more adherent model, reducing deviations between results obtained by physical modelling (using HCTFs, 48 tests) and those obtained with the proposed model, when compared with results obtained using the flocculation models commonly used for this purpose. The decreasing-rising behaviour presented by experimental data for process efficiency versus retention time, not verified in the benchmark models, was satisfactorily addressed by the proposed model. Furthermore, maximum and average absolute percentage deviations obtained using the model proposed in this study were less than or equal to the results obtained with the benchmark models and less for experimental uncertainty (10%). The results obtained indicate that this model can be a useful tool to support the rational design of low retention time units, including applications for the water industry and water recycling systems. <![CDATA[<b>Influence of litter source on soil splash rates and organic carbon loss in different soil horizons</b>]]> Organic litter stabilizes soil particles against the raindrop splash effect. To date, limited research has critically examined the effects of litter quality on soil aggregate detachment and soil organic carbon loss by raindrop splash impact. A study was conducted to determine the effects of different litter sources on quantity of splashed sediments and soil organic carbon (SOC) loss under simulated rainstorm patterns. Soils from seven sieved (< 0.25 mm) horizons mixed with either high-quality Vachellia karroo leaf (C/N = 23.8) and/or low-quality Zea mays stover litter (C/N = 37.4) were incubated in a laboratory for 30 weeks. Splashed sediments and SOC were measured at 1, 3, 8, 14, 23 and 30 weeks of incubation for each soil at 360 mm/h simulated rainfall intensity applied as either single 8-min rainstorm (SR) or 4 × 2-min intermittent rainstorms (IR) separated by a 72-h drying period. Organic litter significantly (P < 0.05) reduced the splashed sediments up to 8 and 14 weeks under IR and SR storms, respectively, and thereafter gradually lost its stabilizing effect on soil aggregates. In order to maintain low quantities of splashed sediments, fresh litter has to be re-applied after this stage. Generally, 13% and 25% more sediments were splashed under IR than SR at 1, 3 and 30, and 8, 14 and 23 weeks after incubation, respectively. Litter quality effect on splash sediments varied across soil horizons but were the same within a soil horizon. Soil horizons with more clay than sand particles had lower quantities of sediments. The SOC loss was influenced by the initial SOC content and primary particle size distribution. Rainstorm pattern and initial SOC content were the main factors that influenced SOC loss. However, more rainstorm patterns should be investigated for these soils. <![CDATA[<b>Activated biomass of the green microalga <i>Chlamydomonas</i> <i>variabilis</i> as an efficient biosorbent to remove methylene blue dye from aqueous solutions</b>]]> The raw and activated biomass of a green microalga, Chlamydomonas variabilis, were investigated as adsorbents for the removal of methylene blue (MB) dye from aqueous solutions. Chlamydomonas variabilis was isolated and cultivated to obtain a sufficient algal biomass. The collected biomass was first oven-dried and then activated by H2SO4. The results obtained showed that the optimum adsorption of MB occurred over 30 min of contact time at pH 7 and an biosorbent dose of 1.5 and 1.0 g·L−¹ of dried biomass and activated biosorbent, respectively. Point of zero charge (pHpzc) was recorded at pH 6.8 and 6.9 for dried and activated biomass, respectively. The activated biomass was a more effective biosorbent than was the dried biomass: At a MB concentration of 82.4 mg·L−¹, the minimum removal was greater than 98% using 1 g·L−¹ activated biomass with a maximum adsorption capacity (q max) of 115 mg·g−¹, whereas at a MB concentration of 56.4 mg·L−¹, the maximum removal did not exceed 80.8% using 1.5 g·L−¹ raw biomass with a q max of 18.3 mg·g−¹. Furthermore, the Freundlich and Langmuir isotherm models of adsorption showed a better model fit when using activated biomass than when using raw biomass, with the former yielding R² values greater than 0.9. The kinetic data suggest that the adsorption of MB follows the pseudo-second-order equation better than the pseudo-first-order one. This study demonstrates that the activated biomass of Chlamydomonas variabilis can be used as an effective biosorbent for the treatment of dye-containing wastewater streams. <![CDATA[<b>Performance evaluation and optimization studies of border irrigation system for wheat in the Indian Punjab</b>]]> Surface irrigation methods are the most widely practiced worldwide for irrigation of row crops. The major problem with these methods is low irrigation efficiency, mainly due to poor design. In the Punjab, border irrigation is used to irrigate wheat crops grown over 90% of the cultivated area. The evaluation of existing border systems using a surface irrigation model showed that the irrigation conditions, comprising of inflow rate, border dimensions, and cut-off time, were diverse in tubewell and canal irrigated areas. The study also examined the feasibility of optimizing border dimensions taking into consideration the existing irrigation conditions for achieving more than 60% application efficiency as compared to the 30-40% achieved under present field conditions. In the case of a border length of 60 m, it was recommended to increase border width in the range of 10-45 m and 20-60 m for different flow rates of 10, 20 and 30 L/s in light and medium soils, respectively. For higher flow rates, a border length ranging from 120-150 m was found to be optimum. For a border length of 150 m, it was recommended to keep a border width ranging from 4-38 m and 8-65 m in light soils and medium soils, respectively, for flow rates of 10, 20, 30 and 60 L/s. Optimizing border dimensions is a practical way to achieve efficient and judicious use of water resources. <![CDATA[<b>Optimising intra-seasonal irrigation water allocation: Comparison between mixed integer nonlinear programming and differential evolution</b>]]> Optimising crop planning in conjunction with intra-seasonal water allocation necessitates the use of daily water budget calculations to determine the timing and amount of irrigation events, which complicates the solution of the problem to global optimality. The main objective of this research was to compare the intra-seasonal water allocation of a mixed integer nonlinear programming (MINLP) model with that of differential evolution (DE), to allocate a limited amount of water while considering irrigable area and the irrigation schedule that will maximise the total gross margin. Results show that both solution procedures adhere to economic theory of water allocation under limited water supply. The conclusion is that the MINLP model most likely achieved very near global optimality as the solutions of the two models were very close to each other. DE holds promise to solve more complex models involving risk and multiple crops. <![CDATA[<b>Untreated wastewater as a source of carbapenem-resistant bacteria to the riverine ecosystem</b>]]> Bacteriological pollution, especially that including clinically important bacteria, of the aquatic environment caused by anthropogenic pressure attracts much attention with regard to public health. Reports to date have not addressed the concentration of emerging carbapenem-resistant bacteria (CRB) in riverine ecosystems, and the source of this pollution is hard to track. We examined the impact of discharge of untreated wastewaters on the bacterial population in the riverine ecosystem, with emphasis on clinically important CRB using a small river in Croatia as a model. River sediments were analysed mineralogically and geochemically. Cultivation of CRB was performed at 37 and 42°C to distinguish the presumably environmental intrinsically resistant (CRB37) from the presumably clinically important acquired resistance (CRB42) species. The significantly positive correlation of CRB42 with CRB37 and total heterotrophs, but not with intestinal enterococci, suggests that entry of CRB42 in riverine ecosystem is not necessarily connected to faecal pollution. The numbers and prevalence of CRB42 are rather dependent on the type of pollution, and is connected to the discharge of wastewaters from different human and animal healthcare centres. Emerging hospital pathogens Acinetobacter baumannii and Klebsiella pneumoniae were exclusively isolated among CRB42 from river water after the discharge of wastewater of a general hospital. The CRB42, once discharged into the riverine ecosystem, behaves as part of the indigenous bacterial population, and could be spread through the natural water bodies or accumulate in river sediments. This implies the need for disinfection of hospital wastewater prior to its discharge into the natural environment in order to avoid the consequent public-health threat. The anthropogenic impact evidenced as bacteriological changes is accompanied by an increase in heavy metal concentrations in river sediments. <![CDATA[<b>Assessing the energy and carbon footprints of exploiting and treating brackish groundwater in Cape Town</b>]]> South Africa has been facing significant challenges in meeting demands in its water and energy sectors in recent years and planning for both sectors has mostly been done separately. The City of Cape Town has started to supplement its dwindling conventional freshwater supplies with groundwater, wastewater and seawater, in light of the drought that commenced in 2015. The Cape Flats Aquifer in Cape Town represents an important resource whose yield could be increased to 85 000 m³/day through artificial stormwater recharge in the Zeekoe Catchment alone. The abstraction and treatment of this water would require significant amounts of energy and thus this paper explores the links between energy usage in the water sector and its carbon footprint. The three alternatives investigated were 'centralised', 'desalination' and 'decentralised' approaches. The former two are centralised treatment mechanisms to produce potable water utilising existing and new treatment infrastructure, respectively, and the latter proposed minimal treatment for non-potable end-users. The energy intensities of the alternatives were evaluated by identifying energy-intensive components and carrying out a preliminary design of the networks and the required treatment mechanisms. South Africa's future potential electricity mixes were used to conceptualise the significance of the associated energy demand. The centralised approach's energy intensity was found to be the lowest of the three, ranging from 1.16 to 1.57 MJ/m³, while those of the decentralised and desalination approaches ranged from 3.57 to 7.31 MJ/m³ and 7.41 to 9.62 MJ/m³, respectively. The Western Cape Water Supply System has an installed capacity of 47.6 MW which could potentially increase by at least 2.7%, 5.7% and 12.3% through the centralised, decentralised and desalination options, respectively. This paper contributes to a growing knowledge on the water-energy nexus in South Africa. <![CDATA[<b>Preparedness or repeated short-term relief aid? Building drought resilience through early warning in southern Africa</b>]]> Southern Africa is highly vulnerable to drought because of its dependence on climate-sensitive sectors of agriculture, hydro-energy and fisheries. Recurring droughts continue to impact rural livelihoods and degrade the environment. Drought severity in southern Africa is exacerbated by poor levels of preparedness and low adaptive capacity. Whilst weather extremes and hazards are inevitable, the preparedness to manage such hazards determines their impact and whether they become disasters. Southern Africa is often caught unprepared by drought as existing early warning systems lack the drought forecasting component, which often results in reactionary interventions as opposed to well-planned and proactive response mechanisms. This study assesses the spatio-temporal changes of rainfall and aridity in southern Africa through an analysis of long-term precipitation and evaporation trends from 1960 to 2007. Stakeholder consultation was conducted in Madagascar, Malawi, Zambia and Zimbabwe during the peak of the 2015/16 drought, focusing on overall drought impacts, current water resource availability, existing early warning systems, adaptation mechanisms and institutional capacity to mitigate and manage droughts as part of overall disaster risk reduction strategies. Average rainfall has decreased by 26% in the region between 1960 and 2007, and aridity has increased by 11% between 1980 and 2007. The absence of drought forecasting and lack of institutional capacity to mitigate drought impede regional drought risk reduction initiatives. Existing multi-hazard early warning systems in the region focus on flooding and drought monitoring and assessment. Drought forecasting is often not given due consideration, yet it is a key component of early warning and resilience building. We propose a regional drought early warning framework, emphasising the importance of both monitoring and forecasting as being integral to a drought early warning system and building resilience to drought. <![CDATA[<b>Deterioration in the water quality of an urbanised estuary with recommendations for improvement</b>]]> Water quality characteristics of the heavily urbanised and industrialised Swartkops River and Estuary in the Eastern Cape have been the focus of several studies since the 1970s. Overloaded and poorly maintained wastewater treatment works (WWTWs), polluted stormwater runoff and solid waste have all contributed to the deterioration in the water quality of the river and estuary. The objective of this study was to determine the current water quality status of the Swartkops Estuary, by investigating spatial and temporal variability in physico-chemical parameters and phytoplankton biomass and where possible relate this to historical water quality data. The present study found evidence suggesting that water is not flushed as efficiently from the upper reaches of the estuary as was previously recorded. Reduced vertical mixing results in strong stratification and persistent eutrophic conditions with phytoplankton blooms (> 20 µg chl a·L−¹), extending from the middle reaches to the tidal head of the estuary. The Motherwell Canal was and still is a major source of nitrogen (particularly ammonium) to the estuary, but the Swartkops River is the primary source of phosphorus with excessive inputs from the cumulative effect of three WWTWs upstream. An analysis of historical water quality data in the Swartkops Estuary (1995 to 2013) shows that all recorded dissolved inorganic phosphorus measurements were classified as hypertrophic (> 0.1 mg P·L−¹), whereas 41% of dissolved inorganic nitrogen measurements were either mesotrophic or eutrophic. If nutrient removal methods at the three WWTWs were improved and urban runoff into the Motherwell Canal better managed, it is likely that persistent phytoplankton blooms and health risks associated with eutrophication could be reduced. <![CDATA[<b>Foliar nitrogen dynamics of an invasive legume compared to native non-legumes in fynbos riparian zones varying in water availability</b>]]> The legume Acacia mearnsii invades South Africa's fynbos riparian zones and may alter the nitrogen (N) dynamics and supply in these areas that typically support few native N fixers. Nitrogen uptake by A. mearnsii may also be influenced by water availability, potentially affecting riparian-specific performance and impact estimations. We expected to find functional differences between the invasive legume and the two co-occurring but non-leguminous native species Brabejum stellatifolium and Metrosideros angustifolia. We also wanted to examine whether in-situ water availability affected N source or uptake in the invasive species. We found A. mearnsii was indeed functioning differently from non-N-fixing native species, and had considerably higher foliar %N. Interestingly, 15N abundance and uptake were associated with site hydrology, meaning water availability should be scrutinised when assuming N-fixing in A. mearnsii using δ15N. Nonetheless, higher water availability to A. mearnsii in fynbos riparian ecosystems did increase foliar N uptake. This has implications for prioritizing clearing of sites with increased nutrient deposition, such as dense stands in relatively moist riparian zones. <![CDATA[<b>Water use of selected grain legumes in response to varying irrigation regimes</b>]]> Grain legumes have potential to contribute to food and nutritional security in water-scarce areas. Information on their yield, water use and water productivity (WP) would be useful for their promotion. The aim of the study was to make a comparative assessment of adaptation, yield, water use and WP of an African indigenous grain legume (bambara groundnut) and two major grain legumes (dry bean and groundnut) under rainfed, deficit and optimum irrigation conditions. Field trials were conducted during the 2015/16 and 2016/17 summer seasons in KwaZulu-Natal, South Africa, using a split-plot design arranged in completely randomised blocks with three replications. Data collected included stomatal conductance, leaf area index, timing of key phenological stages and yield. Water use was calculated as a residual of the soil water balance. Water productivity was obtained as the quotient of grain yield and water use. Crops adapted to limited soil water availability through stomatal regulation and reduction in canopy size and duration. Yield, yield components and WP varied significantly (P < 0.05) among crop species. During 2015/16, groundnut had the highest yield and WP (10 540 kg·ha−1 and 0.99 kg·m−3, respectively). During 2016/17, the highest yield and WP were observed in dry bean, 2 911 kg·ha−1 and 0.75 kg·m−3, respectively. For both seasons, dry bean had the lowest water use (143-268 mm) across all water treatments. Dry bean and groundnut out-performed bambara groundnut with respect to yield, harvest index and WP. For any promotion of bambara groundnut as an alternative crop, there is need for crop improvement to improve yield and WP. <![CDATA[<b>Modelling the unsaturated hydraulic conductivity of a sandy loam soil using Gaussian process regression</b>]]> Unsaturated soil hydraulic conductivity is a main parameter in agricultural and environmental studies, necessary for predicting and managing water and solute transport in soils. This parameter is difficult to measure in agricultural fields; thus, a simple and practical estimation method would be preferable, and quantitative methods (analytical and numerical) to predict the field parameters should be developed. Field experiments were conducted to collect water quality data to model the unsaturated hydraulic conductivity of a sandy loam soil. A mini disk infiltrometer (MDI) was used to measure soil infiltration rate. Input variables included electrical conductivity and the sodium adsorption ratio of irrigation water. Suction rate (pressure head), soil bulk density, and soil moisture content acted as inputs, with unsaturated soil hydraulic conductivity as output. The performance of Gaussian process regression (GPR) was analysed, with multiple linear regression (LR) and multi-layer perceptron (MLP) models used for comparison. Three performance criteria were compared: correlation coefficient (r), root mean square error (RMSE), and mean absolute error (MAE). The simulations employed the Waikato environment for knowledge analysis (WEKA) open source tool. The results indicate that the GPR with Pearson VII function-based universal kernel (PUK kernel), cache size 250007, Omega 1.0 and Sigma 1.0 performs better than other kernels when evaluating test split data, with a correlation coefficient of 0.9646. The RMSEs for GPR (PUK kernel), MLP, and LR were 1.16 × 10−04, 1.87 × 10−04, and 2.22 × 10−04 cm·s−¹, respectively. Predictive data mining algorithms (DMA) enable an estimate of unknown values based on patterns in a database. Therefore, the present methodology can be put to use in predictive tools to manage water and solute transport in soils, as the GPR model provides much greater accuracy than the LR and MLP models in predicting the unsaturated hydraulic conductivity of a sandy loam soil. <![CDATA[<b>Synthesis and characterisation of ultrafiltration membranes functionalised with C18 as a modifier for adsorption capabilities of polyaromatic hydrocarbons</b>]]> The disposal of wastewater containing polyaromatic hydrocarbons (PAHs) has been observed to be a very costly process, hence mitigation for many industrial plants continues to be a challenge. The purpose of this study was to examine the potential use of C18 as a modifier in membrane technology; thus, C18 was incorporated into poly (vinylidene fluoride) (PVDF) membranes. According to the specific composition ratios, the phase inversion process was used for dispersion of the C18 into PVDF, which was subsequently dispersed in 1-methyl-2-pyrrolidone (NMP). The resulting membranes were characterised with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The mechanical properties of the membranes were analysed using dynamic mechanical analysis (DMA), whereas the thermal behaviour was studied with a thermogravimetric analyser (TGA). Furthermore, the functionality of the synthesised membrane was further evaluated by its adsorption potentials using high performance liquid chromatography equipped with an ultraviolet detector. The SEM micrographs showed successful incorporation of the C18 within the polymeric membrane (PVDF) backbone. The TGA showed that the thermal decomposition of the synthesised membranes was observed at 495 and 610°C for PVDF bare and PVDF/C18, respectively. In addition, the HPLC results obtained indicated that the C18 modified membrane was more effective in adsorbing PAHs when compared to the bare PVDF membrane. The salient features of this study therefore suggest that C18 could be used as a potential modifier for the development of PVDF membranes. <![CDATA[<b>Model test and numerical investigation of the effect of the impervious layer's slope on seepage characteristics under hydraulic structures</b>]]> Although the impervious layer under a hydraulic structure is rarely flat, the effect of the impervious layer's slope, under the hydraulic structure, on seepage characteristics has not been studied to date. Therefore, this study investigated the effect of the downhill and uphill impervious layer's slope (downhill/uphill foundation slopes) on the uplift pressure, seepage discharge and exit gradient under hydraulic structures. In order to reach this goal, a numerical model has been developed in which the general equation of fluid flow in non-uniform; anisotropic soil is solved by the finite volume method on a structured grid. The model validation was performed using the measured data from experimental tests. The results of the model validation indicated that the model calculates the seepage discharge and uplift pressure with a maximum error of less than 3.79% and 3.25%, respectively. The results also indicated that by increasing the downhill foundation slope (DFS) the uplift force decreases, but the exit gradient and seepage discharge increase. Moreover, by increasing the uphill foundation slope (UFS), the uplift force increases but the exit gradient and seepage discharge decrease. In addition, the results demonstrate that by increasing the length of the cut-off wall the effect of the DFS on decreasing and UFS on increasing the uplift pressure force becomes more severe. However, the effect of the DFS on increasing the seepage discharge and UFS on decreasing the seepage discharge becomes milder as the length of the cut-off wall increases. By increasing the DFS, from zero to −15%, the exit gradient increases 19.75% and 14.4% for 1 m and 6 m cut-off lengths, respectively. <![CDATA[<b>The use of epilithic diatoms grown on artificial substrata to indicate water quality changes in the lower reaches of the St Lucia Estuary, South Africa</b>]]> In shallow estuaries, artificial substrates provide a means of assessing the response of the diatom community to water chemistry. The shallow St Lucia Estuary was historically connected to the Mfolozi River at the mouth. This connection was severed during the early 1950s due to sediment input from the agriculturally impacted Mfolozi River. A connection has recently been re-established and the potential impact of dissolved inorganic nutrients from the Mfolozi River needs to be determined, as it may alter the ecological integrity of the St Lucia Estuary which forms part of a UNESCO World Heritage Site. This study found that the epilithic algal biomass and diatom species composition grown on glass slides were good indicators of nutrient enrichment in the estuary. Over a 28-day study period an above-average rainfall event resulted in an increase of nutrient-enriched freshwater flow into the estuary. No significant biomass differences were recorded in either the natural phytoplankton or microphytobenthos communities because of high variability. By contrast, the epilithic algal biomass accumulation on the glass slides was highest following the freshwater input. Statistical analyses indicated that the accumulation of the epilithic community on the glass slides was mostly affected by DIN and salinity. Diversity index scores for both the natural phytoplankton and microphytobenthos were variable, while the epilithic diatom index scores consistently declined from Day 7 (H' = 1.2) to Day 28 (H' = 0.7). These data indicate that epilithic algae grown on glass slides can be used as an effective monitoring tool to detect nutrient-induced changes as a supplementary method in this highly variable estuary. <![CDATA[<b>Design norms for soil and water conservation structures in the sugar industry of South Africa</b>]]> This paper contains a critical review of the norms employed in the design of soil and water conservation structures in the South African sugar industry and highlights research needs in order to update them. Sugarcane in South Africa is grown on wide-ranging soils, sometimes in non-ideal climates and on steep topographies where soils are vulnerable to erosion. A consequence of unsustainable soil loss is reduction in field production capacity. Sugarcane fields are protected against erosion through, inter alia, the use of engineered waterways, contour banks and spill-over roads. The South African Sugarcane Research Institute (SASRI), previously known as the South African Sugar Experiment Station (SASEX), developed a nomograph to easily compute the maximum width of field panels based on soil type, tillage method, replant method, surface structures to control runoff, surface cover and slope. This was followed by guidelines and norms for the design of soil and water conservation structures. However, the nomograph was developed based on an acceptable soil loss of 20 t·ha−1·yr−1, yet soil formation rates in South Africa range between 0.25 and 0.38 t·ha−1·yr−1. Comparisons between design norms in the National Soil Conservation Manual and norms used in the sugar industry clearly show discrepancies that need to be investigated. The design of soil conservation structures includes the design of both contour bank spacing and hydraulic capacity. The sustainable soil loss method is recommended in the design of contour spacing and it determines contour spacing based on evaluation of site-specific sheet and rill erosion potential of the planned contour spacing while the hydraulic design employs Manning's equation. Considering that increases in both design rainfall and design floods are anticipated in South Africa, it is necessary to incorporate these projections in the design of soil and water conservation structures. Many soil loss models exist, of which empirical models are the most robust and provide stable performances. The majority of empirical models are lumped models which estimate average annual soil loss. The Modified Universal Soil Loss Equation (MUSLE) estimates event-based erosion and, given that the majority of soil erosion occurs during a few extreme events annually, the design norms should be updated using the MUSLE. <![CDATA[<b>Microfibre pollution hotspots in river sediments adjacent to South Africa's coastline</b>]]> River sediment samples collected in the lower reaches of catchments along South Africa's coastline have microfibre levels ranging from 0 to 567 fibres/dm³. This range is similar to those of sandy beach sediments along the coast. Much higher microfibre levels are observed in KwaZulu-Natal and the Wild Coast region, compared to the Cape South Coast. There is a significant positive relationship between river sediment microfibre levels, and the percentage of households in the catchment area that do not have access to piped water. The implication is that rural communities that rely on rivers as their primary or only source of water, including for directly washing clothes in, may be significantly contributing to microfibre pollution of freshwater aquatic ecosystems. If microfibre pollution is found to have ecosystem or human health implications such as chemical toxicity or fibre-induced mesothelioma, this will be detrimental to river biota and these communities. <![CDATA[<b>Water SA Reviewers 2018</b>]]> River sediment samples collected in the lower reaches of catchments along South Africa's coastline have microfibre levels ranging from 0 to 567 fibres/dm³. This range is similar to those of sandy beach sediments along the coast. Much higher microfibre levels are observed in KwaZulu-Natal and the Wild Coast region, compared to the Cape South Coast. There is a significant positive relationship between river sediment microfibre levels, and the percentage of households in the catchment area that do not have access to piped water. The implication is that rural communities that rely on rivers as their primary or only source of water, including for directly washing clothes in, may be significantly contributing to microfibre pollution of freshwater aquatic ecosystems. If microfibre pollution is found to have ecosystem or human health implications such as chemical toxicity or fibre-induced mesothelioma, this will be detrimental to river biota and these communities.