Scielo RSS <![CDATA[Water SA]]> http://www.scielo.org.za/rss.php?pid=1816-795020200002&lang=en vol. 46 num. 2 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Estimating evapotranspiration in a semi-arid catchment: A comparison of hydrological modelling and remote-sensing approaches</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200001&lng=en&nrm=iso&tlng=en Reliable spatial data of evapotranspiration (ET) in support of water resources management are limited. ET is a major component of the water balance, in many regions, and therefore it is critical that it be accurately quantified. To identify a product that accurately estimates spatially distributed ET for application in data-scarce regions, an inter-model comparison was conducted between the MOD16 ET dataset and the ET calculated with the calibrated and validated JAMS/J2000 hydrological model in the Sandspruit catchment (South Africa). Annual JAMS-ET and MOD16-ET data were generally consistent. Monthly JAMS-ET and MOD16-ET dynamics are influenced by the response of vegetation to precipitation as well as the atmospheric evaporative demand. The maximum correlation coefficient between JAMS-ET and MOD16-ET was 0.82 and it was evident at Lag 0, showing that both ET estimates are in phase when evaluated at the basin scale. The maximum correlation coefficients between the ET estimators and precipitation were 0.67 and 0.70 for JAMS-ET and MOD16-ET, respectively, and this was evident at Lag 2 (1 lag is 1 month) for both methods. This suggests that there is a 2-month delay in the maximum response of ET to precipitation. The models did not exhibit significant dependence on the seasonal distribution of precipitation. The complementary use of hydrological modelling and satellite-derived data may be greatly advantageous to water resources management, e.g., water allocation studies, ecological reserve determinations and vegetation water use studies. The results of the inter-model comparison also provide motivation for the use of the MOD16 ET dataset to estimate ET in data-scarce regions. Additionally, this study provides evidence for the potential use of validated satellite-based ET data as inputs in hydrological models. This may facilitate a more realistic representation of the catchment hydrological processes. <![CDATA[<b>Calibration of a modelling approach for sediment yield in a wattle plantation, KwaZulu-Natal, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200002&lng=en&nrm=iso&tlng=en Hydrological modelling is an appropriate approach to investigate the effect of interactions of climate, land-use and soil on the water-use of natural or managed ecosystems, in particular where spatial heterogeneity exists. The Soil and Water Assessment Tool (SWAT) model has evolved into one of the most widely used catchment-scale hydrological models, which has been extensively used to better understand hydrological processes. In this paper, the SWAT model was adopted to simulate a wattle plantation in KwaZulu-Natal, South Africa. User-defined vegetation growth, soil and management input parameters were constructed for the study area based on site measurements. These parameters were subsequently modified using the Sequential Uncertainty Fitting (SUFI-2) analysis routine to calibrate the model. The calibrated model captured seasonal trends in the observed sediment and streamflow data. The compilation of spatially explicit sediment output provides a useful approach to manage catchments by identifying high erosion-risk areas. The SWAT model, using site-specific input parameters, provides a platform for subsequent hydrological and sediment modelling in South Africa. <![CDATA[<b>Verification of runoff volume, peak discharge and sediment yield simulated using the ACRU model for bare fallow and sugarcane fields</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200003&lng=en&nrm=iso&tlng=en The Agricultural Catchments Research Unit (ACRU) model is a daily time step physical-conceptual agrohydrological model with various applications, design hydrology being one of them. Model verification is a measure of model performance and streamflow, soil water content and sediment yield simulated by the ACRU model have been extensively verified against observed data in southern Africa and internationally. The primary objective of this study was to verify simulated runoff volume, peak discharge and sediment yield against observed data from small catchments, under both bare fallow conditions and sugarcane production, which were located at La Mercy in South Africa. The study area comprised 4 research catchments, 101, 102, 103 and 104, monitored both under bare fallow conditions and sugarcane production, with different management practices per catchment. Observed data comprised: daily rainfall, maximum and minimum temperature, A-pan evaporation and runoff for the period 1978-1995, and peak discharge and sediment yield for the period 1984-1995. The data were checked for errors and and inconsistent records excluded from analysis. Runoff volume, peak discharge and sediment yield were simulated with the ACRU model and verified against the respective observed data. In general, the correlations between observed and simulated daily runoff volumes and peak discharge were acceptable (i.e. slopes of regression lines close to unity, R² > 0.6 and the Nash-Sutcliffe coefficient of efficiency close to unity). Similarly, the correlation between observed and simulated sediment yield was also good. From the results obtained, it is concluded that the ACRU model is suitable for the simulation of runoff volume, peak discharge and sediment yield from catchments under both bare fallow and sugarcane land cover in South Africa. <![CDATA[<b>Effect of Moistube and subsurface drip irrigation on cowpea <i>(Vigna unguiculata </i>(I.) Walp) production in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200004&lng=en&nrm=iso&tlng=en Moistube irrigation (MTI) is a new subsurface irrigation technology where the water emits from a semipermeable membrane at a slow rate depending on applied pressure and soil water potential. There is lack of information on how various crops respond to MTI. This study determined growth, yield and water use efficiency (WUE) of cowpea (Vigna unguiculata (L.) Walp) under varying water regimes under MTI and subsurface drip irrigation (SDI), using field and glasshouse experiments in summer and winter of 2018, respectively. A split-plot design arranged in randomized complete blocks, replicated 3 times, with SDI as the control experiment was used. The main plot was irrigation type while the sub-plots were the water regimes. The water treatments consisted of full irrigation (100% of crop water requirement (ETc)), and deficit irrigation (DI) of 70% ETc and 40% ETc. Water deficit had a significant effect (p < 0.05) on time to flowering; plants under 40% ETc flowered 14 days earlier than plants at 100% ETc. There were significant (p < 0.05) differences in yield components. Grain yields were 1 280 kg-ha-1, 2 401 kg-ha-1 and 3 189 kg-ha-1 for 40% ETc, 70% ETc and 100% ETc, respectively, but no significant (p &gt; 0.05) differences were recorded between SDI and MTI. However, at 40% ETc, SDI had 15% higher yield than MTI. Biomass varied significantly (p < 0.05) with irrigation type and water treatment. Grain WUE varied significantly (p < 0.05) among the water regimes. The highest WUE was achieved under SDI at 70% ETc but was not significantly different from that under MTI at 70% ETc. In conclusion, performance of cowpea was similar under the two irrigation systems under moderate DI but was better for SDI under severe DI with respect to biomass and WUE for the summer trial. Moderate DI improved the grain WUE while all the DI conditions improved the biomass WUE. <![CDATA[<b>Effect of intercropping madumbe <i>[Colocasia esculenta) </i>and rice <i>(Oryza sativa L.) </i>on yield and land productivity under different irrigation water management techniques with effluent water</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200005&lng=en&nrm=iso&tlng=en The need for the optimal use of land, without a yield penalty, in urban and peri-urban (UP) settlements is vital. This study investigated the effect of intercropping madumbe and rice with respect to yield and land productivity when irrigated with anaerobic baffled reactor (ABR) effluent under different irrigation water management techniques. It was hypothesized that intercropping under different irrigation water management techniques has no effect on the yield and land productivity. Field trials were conducted in the 2017 and 2018 cropping seasons with ABR effluent (without fertilizer) at the Newlands Mashu Experimental Site, Newlands East, Durban, South Africa. A randomized complete block design with 3 replications; cropping treatments of sole madumbe, sole rice and madumbe + rice (intercrop) and irrigation treatments of alternate wetting and drying (AWD), continuous flood irrigation (CFI) and wetting without flooding (WWF) was used. Growth and yield parameters at harvest were determined. Thereafter, land equivalent ratio (LER) was calculated to evaluate the productivity of the intercrop. The effect of intercropping was significant (P < 0.05) on the total number of irrigation events and total water use. There was a significant reduction (P < 0.05) in plant heights of both madumbe and rice at intercrop. However, the effect on plant height for treatment CFI was positive but not significant (P &gt; 0.05) for both seasons. A significant (P < 0.05) reduction also occurred in the number of madumbe leaves/plant, and panicles/plant and tillers/plant for rice. Intercropping significantly reduced (P < 0.05) madumbe corm and rice grain yield over the two seasons relative to sole cropping. LER showed that intercropping madumbe with rice was not more productive (LER < 1) than sole cropping of madumbe. It was concluded that over the two-season period, intercropping madumbe and rice do not yield appreciably under any of the three irrigation management techniques applied and the study hypothesis is thus rejected. <![CDATA[<b>Using sap flow data to assess variations in water use and water status of apple orchards of varying age groups in the Western Cape Province of South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200006&lng=en&nrm=iso&tlng=en No accurate quantitative information currently exists on how water use of apple (Malus domestica) orchards varies from planting to full-bearing age, leading to poor irrigation and water allocation decision making. This study sought to address this knowledge gap by investigating how the water use and tree water status vary with canopy cover, cultivar, and climatic conditions in 12 orchards growing in prime apple-producing regions in South Africa. The orchards were planted to the Golden Delicious/Golden Delicious Reinders cultivars which are widely planted in South Africa and the Cripps' Pink/Cripps' Red/Rosy Glow which are high-value late-season cultivars. The performance of two transpiration reduction coefficients, one based on sap flow (Ksf) and the other based on soil water depletion (Ks) (FAO approach) were evaluated against the midday stem water potential (MSWP) in all the orchards. While canopy cover had a clear effect on the whole-tree sap flow rates, there were no significant differences in the transpiration per unit leaf area among the cultivars. The daily average sap flux density under unstressed conditions was highest (~284 cm³-cm-2) in the medium canopy cover orchards (30-44% fractional cover), followed by the mature orchards (~226 cm³-cm-2), and was lowest in the young orchards (~137 cm³-cm-2). Canopy cover rather than growing season length had a greater effect on seasonal total water use. Peak daily orchard transpiration ranged from 1.7 mm for young Golden Delicious Reinders trees to 5.0 mm in mature Golden Delicious trees that were maintained with large canopies to reduce sunburn damage to the fruit. For the red cultivars, the peak daily transpiration ranged from 2.0 to 3.9 mm, and the mature trees were maintained with less dense canopies to facilitate the development of the red fruit colour. The less dense canopies on the red cultivars had water-saving benefits since the seasonal total transpiration was lower relative to the Golden Delicious cultivar. The sap flow derived stress coefficient was strongly correlated to the MSWP (R² ~ 0.60-0.97) in all the orchards while Ks was not able to detect plant stress due to over-irrigation. <![CDATA[<b>Ensuring access to water for food production by emerging farmers in South Africa: What are the missing ingredients?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200007&lng=en&nrm=iso&tlng=en One of the key components essential to the productivity of small-scale farmers who secured farms through the land redistribution programme in South Africa is access to reliable sources of water for irrigation. In this study, we deployed a stakeholder-oriented qualitative research methodology to understand the extent to which land reform farming schemes in Bela-Bela and Greater Sekhukhune have been able to access water and use it to enhance their agricultural production. We were keen to identify and articulate the water-related challenges and missing ingredients for successful agricultural production on the new farming schemes. The study found that access to water for irrigated agriculture is not guaranteed for most of the emerging farmers and they do not have the finance needed to invest in sustainable water supply systems for irrigation. As a result, the majority of the farmers in our study sample have not been able to realize any meaningful agricultural production, with their farming schemes being either underutilized or not functioning at all. Other key challenges include lack of finance, high costs of electricity, and lack of farming knowledge among the emerging farmers. The paper concludes that there is need for key actors in the development sector to provide more substantive post-land transfer support and ensure better access to water for the emerging farmers. This will enhance the farmers' chances of realizing more meaningful agricultural production while improving their livelihoods. <![CDATA[<b>Determinants of farmer awareness of water governance across gender dimensions in smallholder irrigation schemes in KwaZulu-Natal Province, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200008&lng=en&nrm=iso&tlng=en Water is a vital resource for irrigated agricultural production. Its availability and accessibility are critical for alleviating poverty and achieving food security in rural households. However, smallholder irrigated agriculture in South Africa faces limited water supply emanating from scheme governance problems, with weak institutional arrangements that fail to equitably and effectively govern water resources. South African water policy has been transforming over the years. However, statutory laws remain unknown in smallholder irrigation schemes. This study sought to assess farmer awareness of water governance and identify the determinants of farmer awareness of water governance dimensions across gender dimensions in Mooi River, Tugela Ferry, and Ndumo irrigation schemes. The study employed principal component analysis to generate water governance indices, that is, formal institutions, the existence and effectiveness of scheme constitutions, scheme committees and enforcement of informal rules in the scheme. The ordinary least square regression technique was then used to identify factors determining farmer awareness of formal and informal water institutions in the three irrigation schemes. The findings suggest that formal water institutions are unknown and factors such as household characteristics, scheme location, stakeholder participation and involvement in scheme decision-making processes significantly influence awareness of governance. Therefore, there is a need to raise farmer awareness of formal water institutions and to strengthen the informal institutions which are functional, recognised and in line with irrigation management transfer. <![CDATA[<b>Failed intentions? Meeting the water needs of people living with HIV in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200009&lng=en&nrm=iso&tlng=en Researchers, activists, practitioners and policy-makers have grappled with the challenge of providing people living with HIV (PLHIV) with an adequate amount of safe water. Comprising 13% of the overall population of South Africa in 2018, 7.52 million PLHIV need water for drinking and taking medication; preparing food; and personal hygiene and cleaning to minimise infections. This article examines the responses of the different stakeholders to this challenge and their impact on the water and health policy process. It finds that activists were able to emphasise the dimensions of the challenge; practitioners worked to implement provision more effectively within existing policy frameworks; and a range of stakeholders made a thoughtful and promising policy proposal for direct action, which the Department of Water and Sanitation ultimately failed to embrace. This article is based on an extensive review of academic research and publications by development agencies on HIV and water as well as engagement with policies and documents in the South African water sector related to water services delivery for PLHIV. While the widespread provision of antiretrovirals from 2004 has changed the context, the above findings are significant in understanding and reviewing the impact of various stakeholders on the water and health policy process. They raise questions regarding the effectiveness of NGO advocacy, the means of delivering improved services to specific populations, and the ability of a range of stakeholders to inform the policy approaches of government departments. <![CDATA[<b>Garden footprint area and water use of gated communities in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200010&lng=en&nrm=iso&tlng=en Gated community homes in South Africa are popular amongst property buyers in urban environments such as cities and metropoles due to the increased security and lifestyle improvements offered. Garden design and layout requirements are prescribed in architectural guidelines compiled by the homeowners associations of these communities. Garden footprint area in gated community homes is of importance to researchers and planners, because of the influence on water use. This study used a quantitative approach to evaluate the spatial data of garden footprint area as a percentage of total plot area for 1 813 gated community homes in different regions of South Africa. The research reviewed how garden footprint area is prescribed and how it is applied in gated community homes. The impact of garden footprint area on water use was also analysed. The results were compared to relevant information lifted from specific architectural design guidelines developed for each gated community. Data from 11 gated communities were analysed and the average garden footprint area was found to be 36% of the total plot area. Gated community homes with a garden area smaller than 100 m² were found to have limited influence on monthly water consumption, while the water use of gated community homes with a larger garden footprint area increased proportionally with garden footprint area. The seasonal fluctuation of water use is illustrative of garden irrigation and other outdoor water use. The results provided useful input for incorporation in outdoor water use modelling of gated community homes. <![CDATA[<b>Toxicity testing: ecological relevance and relative efficacy and costs of toxicity tests in the South African context</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200011&lng=en&nrm=iso&tlng=en The Direct Estimation of Ecological Effect Potential (DEEEP) is a suite of toxicological methods that was compiled to facilitate management of effluent discharges. DEEEP used a range of tests to assess different endpoints and test taxa from differing trophic levels. It was used at pilot scale but never adopted in South Africa formally. The use of toxicological testing in managing effluent discharge has been somewhat ad-hoc since. This study examined a range of tests for undertaking toxicological assessments of effluent from the perspectives of ecological realism, test tractability, and cost of testing. The assays assessed include some from DEEEP, some using South African test taxa, and some using commercial toxicity test kits. Results indicate that, in terms of returned endpoints, no clear difference between tests using immobilized and cultured or wild-collected test taxa was present. Culture maintenance was found to be a significant contributor to test costs where cultured test taxa were used (although culture costs are implicit in test kit costs too). Costing analysis looked at scenarios where equipment could be shared and reused, and how these contribute to laboratory costs. The research leads on to suggestions for testing implementation in laboratories while maximizing ecological realism and minimizing costs. <![CDATA[<b>Challenges and shortcomings in current South African industrial wastewater quality characterisation</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200012&lng=en&nrm=iso&tlng=en Previous research in South Africa has identified gaps in wastewater quality characterisation and remediation. Wastewater quality indicators need to be known in order to reuse, recycle, and/or recover resources, but are poorly reported for wastewater streams. Formal and relational approaches were used to access wastewater quality information. Relational approaches included building relationships with industry partners through telephone calls, emails and meetings, while formal approaches included requests for public documents and legal applications using the Promotion of Access to Information Act. Published data were another source of information. The following industries were identified as major wastewater generating industries: pulp and paper, fish processing, power generation, mining and petroleum. Seven parameters were commonly used to indicate quality: pH, volume, electrical conductivity, nitrogen, sulphate, sodium and chemical oxygen demand. Calcium was not measured, even though discharge limits are required in environmental licenses. The accessed wastewater quality data ranged from qualitative to quantitative. The number of parameters used varied within and between industries. Although wastewater information is non-confidential, in practice it is not readily available. There are opportunities to improve wastewater management and resource recovery; however, this needs to happen in an environment of trust and transparency. This is currently lacking between industry, government, and research bodies. <![CDATA[<b>Occurrence of antibiotics and antiretroviral drugs in source-separated urine, groundwater, surface water and wastewater in the peri-urban area of Chunga in Lusaka, Zambia</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200013&lng=en&nrm=iso&tlng=en Recently, there has been an increased interest in bridging the knowledge gap in the occurrence and fate of pharmaceuticals in African urban water cycles. In this study, the occurrence of 7 antibiotics and 3 antiretrovirals in source-separated urine, groundwater, wastewater and surface water of the peri-urban area of Chunga in Lusaka, Zambia, was studied. In groundwater, the pharmaceuticals were only sporadically present with 4 antibiotics and 1 antiretroviral detected. The concentration of the antibiotics ranged from below limit of quantification (<LOQ) to 880 ng/L, with sulfamethoxazole having the highest detection frequency of 42.3%. In the surface water, a comparatively high concentration of pharmaceuticals was measured with concentrations ranging from <LOQ-11 800 ng/L to <LOQ-49 700 ng/L for antibiotics and antiretroviral drugs, respectively. Similarly, the concentration of antibiotics in wastewater treatment plant (WWTP) influent and effluent waters ranged from 100-33 300 ng/L and 80-30 040 ng/L, respectively. The concentration of the antiretrovirals was also relatively high in the wastewater and ranged from 680-118 970 ng/L and 1 720-55 760 ng/L in the influent and effluent, respectively. The concentration of the target analytes in source-separated urine were several orders of magnitude higher than in wastewater. Sulfamethoxazole, trimethoprim and lamivudine had the highest concentrations, of 7 740 ug/L, 12 800 ug/L and 10 010 ug/L, respectively. The high concentration detected in source-separated urine calls for precautionary measures to be undertaken when such urine is to be used as a fertilizer. However, urine source separation has a major advantage of pooling a significant proportion of excreted pharmaceuticals into small manageable volumes which can be effectively treated, minimizing environmental contamination. The high concentrations of antibiotics and antiretroviral drugs measured in this study necessitate creation of effective barriers to mitigate the possible environmental and human health risks. <![CDATA[<b>Determination of Cd, Mn and Ni accumulated in fruits, vegetables and soil in the Thohoyandou town area, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200014&lng=en&nrm=iso&tlng=en The accumulation of heavy metals such as Cd, Mn and Ni was investigated in seven different vegetables, fruits and soil samples from Thohoyandou, Limpopo Province, South Africa. Heavy metals were quantified using graphite furnace atomic absorption spectrometry. Concentrations of heavy metals in fruits and vegetables were in the range of 0.23-2.94 mg-kg-' for Cd, 11.72-50.16 mg-kg-' for Mn and 5.73 - 44.11 mg-kg-' for Ni on a dry weight basis. Analysis of soils from where fruits and vegetables were sampled showed that Cd in the soil was in the range of 0.08-1.07 mg-kg-1, Mn levels were 204.99-249.13 mg-kg-1 and Ni levels were 48.47-88.23 mg-kg-1. Cd was below the instrument detection limit for soils on which onions and bananas were grown. Vegetables showed different accumulation abilities, with leafy vegetables being the highest accumulators of heavy metals. The obtained results showed that concentrations of Cd in fruits, vegetables and soils exceeded the recommended maximum acceptable levels proposed by FAO/WHO and, hence, may pose a health risk to consumers. Ni concentrations in bananas, onion, beetroot, spinach and Chinese cabbage exceeded recommended standards by FAO/WHO. <![CDATA[<b>Heterogeneous photocatalytic degradation of anthraquinone dye Reactive Blue 19: optimization, comparison between processes and identification of intermediate products</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200015&lng=en&nrm=iso&tlng=en Treatment of textile wastewater using heterogeneous photocatalysis began in the the last decade and attracted the attention of researchers due to its versatile application. The variety of applications of TiO2 as a photocatalyst was due toits numerous positive properties, such as low operating temperature, biologically inert nature, low energy consumption, water insolubility, availability and photoactivity, low toxicity, high chemical stability, suitable flat band potential, narrow bandgap and the fact that it is environmentally benign. Heterogeneous UV-TiO2 photocatalysis is capable of removing organic pollutants from textile wastewater; this has been widely studied, with the technology also having been commercialized in many developing countries. Decolorization of anthraquinone dye Reactive Blue 19 (RB 19) by heterogeneous advanced oxidation processes TiO2/UV/H2O2, TiO2/UV/KBrO3 and TiO2/UV/(NH4)2S2O8 was studied under different conditions and in the presence of electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3) and ammonium persulphate ((NH4)2S2O8). Decolorization was very fast for all three processes, and complete dye decolorization was achieved in 10 min. The effect of various ions (Cl-, SO4(2-) and HCO3-) on RB 19 decolorization was also studied. The optimal condition for the decolorization of the dye were determined to be: TiO2 concentration 1 g-dm-3, electron acceptor concentration 30.0 mmol-dm-3, dye concentration 50.0 mg-dm-3, UV intensity 1 950 uW-cm-2, at temperature 25 ± 0.5°C. In addition, experiments were performed and compared in three different matrices. In the surface water and dyebath effluent water, the removal efficiency for RB 19 was lower than that achieved in the deionized water because of the interference of complex constituents in the surface water and effluent. LC-MS analysis was carried out and the detected intermediates were compared with the previously published data for anthraquinone dyes. <![CDATA[<b>Evaluation of bio-coagulants for colour removal from dye synthetic wastewater: characterization, adsorption kinetics, and modelling approach</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200016&lng=en&nrm=iso&tlng=en Dye usage for industrial applications has been on the increase and these activities generate large amounts of dye-constituted wastewater that should be treated before environmental discharge or reuse. Various studies have shown the application of natural organic polymer (NOP) coagulants in dye removal from industrial wastewater. In this research, the coagulation performances of Vigna unguiculata (VU) and Telfairia occidentalis (TO) for colour removal from crystal Ponceau 6R dye synthetic wastewater was studied. The proximate compositions, structure, and surface morphologies of the coagulants were investigated using standard methods, i.e. Fourier-Transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). Colour removal was evaluated through the time-dependent decrease in particle concentration and thus growth of flocs. Effects of the process parameters, including pH, coagulant dosage, dye concentration (DC), settling time, and temperature were preliminarily tested and the best range experimentally determined. The optimal operating conditions established were pH 2, 800 mg-L-1 coagulant dosage, 100 mg-L-1 dye concentration, 300 min, and 303 K. The order of greatest removal was VUC > TOC with optimum efficiency of 93.5% and 90.7%, respectively. The values of K and a obtained for VUC and TOC were 8.09 x 10-4 L-mg-1-min-1, 1.7 and 9.89 x 10(4) L-mg-1-min-1, 1.6, respectively. Coagulation time, Tag, calculated and deduced from the particle distribution plot, showed a rapid coagulation process. Coagulation-adsorption kinetics indicated agreement with the pseudo-second-order model deducing that chemisorption is the rate-controlling step. It further indicates that particle adsorption on the polymer surfaces occurred mostly as a mono-molecular layer and according to the chemisorption mechanism. Cross-validation showed good prediction of the experimental data. The selected coagulants have the potential for application as efficient coagulants while also showing significant adsorption characteristics. The application of kinetics and modelling in separation processes involving particle transfer is especially required in wastewater treatment. <![CDATA[<b>Application of response surface methodology for simultaneous removal of major cations from seawater using metal oxide nanostructures</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200017&lng=en&nrm=iso&tlng=en The objectives of this study were to assess the suitability of metal oxide nanomaterials for removal of major cations Na+, K+, Ca²+ and Mg²+ from seawater. The as-synthesised nanomaterials were characterized using different techniques, such as XRD, TEM, and BET. The simultaneous removal of Na+, K+, Ca²+ and Mg²+ ion from aqueous solutions by a-Fe2O3 and SiO2/Nb2O5/Fe2O3 nanostructures was studied using batch method. The influence of different experimental parameters (such as initial metal ion concentrations, mass of adsorbent, sample pH and contact time) that affect the simultaneous removal of metal ions was studied using response surface methodology (RSM) based on small central composite design (SCCD). Under optimised conditions, the highest percentage removal was 75%, 92%, 93% and 85% for Na+, K+, Ca²+ and Mg²+, respectively. <![CDATA[<b>Biosorption of phenol by modified dead leaves of <i>Posidonia oceânica </i>immobilized in calcium alginate beads: Optimal experimental parameters using central composite design</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200018&lng=en&nrm=iso&tlng=en This study reports the biosorption of phenol using dead leaves of Posidonia oceanica (PO), an endemic seagrass in the Mediterranean Sea. The PO dead leaves were pre-treated with sulfuric acid and carbonized at 500°C for 2 h to increase their adsorptive capacity. Leaves were then immobilized in calcium alginate beads to address problems that arise when free particulate biosorbents are used. Response surface methodology (RSM) based on central composite design (CCD) was carried out to optimize key variables, viz., initial phenol concentration (100-500 mg/L), biosorbent dosage (0.05-0.1 g/50 mL), and alginate beads to solution ratio (1/10-2/10). The effect of the operating variables on phenol biosorption capacity was studied in a batch system and a mathematical model showing the influence of each variable and their interactions was obtained. The predicted second-order quadratic model for the response variable was significant (p < 0.01). Further, an adjusted squared correlation coefficient, R² (adj) of 97.7% indicated a satisfactory fit of the model. The results of CCD showed maximum biosorption capacity of about 127 mg/g at 500 mg/L initial phenol concentration, 1 g/L biosorbent dosage, and at 1.85/10 composite beads to solution ratio. This work demonstrates the suitability of using PO dead leaves as an effective low-cost biosorbent for the removal of phenol. <![CDATA[<b>ERRATUM:<b>Water quality in non-perennial rivers [Water SA 45 (3) 487-500]</b></b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200019&lng=en&nrm=iso&tlng=en This study reports the biosorption of phenol using dead leaves of Posidonia oceanica (PO), an endemic seagrass in the Mediterranean Sea. The PO dead leaves were pre-treated with sulfuric acid and carbonized at 500°C for 2 h to increase their adsorptive capacity. Leaves were then immobilized in calcium alginate beads to address problems that arise when free particulate biosorbents are used. Response surface methodology (RSM) based on central composite design (CCD) was carried out to optimize key variables, viz., initial phenol concentration (100-500 mg/L), biosorbent dosage (0.05-0.1 g/50 mL), and alginate beads to solution ratio (1/10-2/10). The effect of the operating variables on phenol biosorption capacity was studied in a batch system and a mathematical model showing the influence of each variable and their interactions was obtained. The predicted second-order quadratic model for the response variable was significant (p < 0.01). Further, an adjusted squared correlation coefficient, R² (adj) of 97.7% indicated a satisfactory fit of the model. The results of CCD showed maximum biosorption capacity of about 127 mg/g at 500 mg/L initial phenol concentration, 1 g/L biosorbent dosage, and at 1.85/10 composite beads to solution ratio. This work demonstrates the suitability of using PO dead leaves as an effective low-cost biosorbent for the removal of phenol. <![CDATA[<b>ERRATUM: Policy implementation considerations for basic services: A South African urban sanitation case [Water SA 45 (4) 536-546]</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200020&lng=en&nrm=iso&tlng=en This study reports the biosorption of phenol using dead leaves of Posidonia oceanica (PO), an endemic seagrass in the Mediterranean Sea. The PO dead leaves were pre-treated with sulfuric acid and carbonized at 500°C for 2 h to increase their adsorptive capacity. Leaves were then immobilized in calcium alginate beads to address problems that arise when free particulate biosorbents are used. Response surface methodology (RSM) based on central composite design (CCD) was carried out to optimize key variables, viz., initial phenol concentration (100-500 mg/L), biosorbent dosage (0.05-0.1 g/50 mL), and alginate beads to solution ratio (1/10-2/10). The effect of the operating variables on phenol biosorption capacity was studied in a batch system and a mathematical model showing the influence of each variable and their interactions was obtained. The predicted second-order quadratic model for the response variable was significant (p < 0.01). Further, an adjusted squared correlation coefficient, R² (adj) of 97.7% indicated a satisfactory fit of the model. The results of CCD showed maximum biosorption capacity of about 127 mg/g at 500 mg/L initial phenol concentration, 1 g/L biosorbent dosage, and at 1.85/10 composite beads to solution ratio. This work demonstrates the suitability of using PO dead leaves as an effective low-cost biosorbent for the removal of phenol. <![CDATA[<b>ERRATUM: Laboratory method design for investigating the phytoremediation of polluted water [Water SA 45 (4) 608-615]</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1816-79502020000200021&lng=en&nrm=iso&tlng=en This study reports the biosorption of phenol using dead leaves of Posidonia oceanica (PO), an endemic seagrass in the Mediterranean Sea. The PO dead leaves were pre-treated with sulfuric acid and carbonized at 500°C for 2 h to increase their adsorptive capacity. Leaves were then immobilized in calcium alginate beads to address problems that arise when free particulate biosorbents are used. Response surface methodology (RSM) based on central composite design (CCD) was carried out to optimize key variables, viz., initial phenol concentration (100-500 mg/L), biosorbent dosage (0.05-0.1 g/50 mL), and alginate beads to solution ratio (1/10-2/10). The effect of the operating variables on phenol biosorption capacity was studied in a batch system and a mathematical model showing the influence of each variable and their interactions was obtained. The predicted second-order quadratic model for the response variable was significant (p < 0.01). Further, an adjusted squared correlation coefficient, R² (adj) of 97.7% indicated a satisfactory fit of the model. The results of CCD showed maximum biosorption capacity of about 127 mg/g at 500 mg/L initial phenol concentration, 1 g/L biosorbent dosage, and at 1.85/10 composite beads to solution ratio. This work demonstrates the suitability of using PO dead leaves as an effective low-cost biosorbent for the removal of phenol.