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  Subjects -> WATER RESOURCES (Total: 160 journals)
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Water SA
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  This is an Open Access Journal Open Access journal
ISSN (Print) 0378-4738 - ISSN (Online) 1816-7950
Published by SciELO Homepage  [672 journals]
  • How local communities access, utilise and evaluate inland fisheries, and
           their influence on fishery conservation status in northern Zimbabwe

    • Abstract: The conservation status of inland fishery resources is vulnerable worldwide, and this threatens the livelihoods of fishing-dependent communities. This case study aimed to: (i) establish the use and perception of fisheries and ecosystem services by locals, (ii) undertake a monetary valuation of the fisheries, (iii) determine the potential threats to the fisheries, and (iv) examine the social drivers and barriers for citizen science involvement. Lastly, (v) we evaluated how the above factors affected the conservation of fisheries at Mushumbi Pools, Zimbabwe. A cross-sectional survey of 69 households was conducted. Results of the study showed that locals utilised 17 fish species for social, economic, cultural and religious purposes. Locals attach high intrinsic socio-economic value to the fisheries resources and wetland ecosystem services provided by the Mushumbi Pools. Despite the sustained income from fisheries, the local market in Mushumbi Pools is actually undervaluing fisheries resources, as the fish prices in the area are very low compared to standard market prices countrywide. A larger proportion of the respondents (65%) cited poor land-tilling practices, heavy application of agropesticides and use of unsustainable fish harvesting methods as the main threats to fish diversity in Mushumbi Pools. Relaxed fishing concessions for women and children in specific fishing zones were key drivers for community participation in fisheries conservation. However, strict enforcement of fishing bans in breeding and nursery zones and restricted access to some parts of the Mushumbi Pools were the main barriers for local involvement in the conservation of fisheries resources. Without the fishing community's participation there is no guaranteed sustainability of the fishery resources in the pools. Legitimising community access, ensuring fair valuation and utility rights is a key driver for successful management of inland fisheries resources in Sub-Saharan Africa.
  • Public perception of water re-use: building trust in alternative water
           sources in Malmesbury, South Africa

    • Abstract: The recent drought in the Western Cape Province in South Africa has been marked as the worst since 1904. The drought impacted severely on the availability of bulk water supply in many parts of the Western Cape Province, particularly the Cape Town Metro and surrounding districts. In order to alleviate water scarcity, wastewater recycling (water reuse) has been identified to have the potential to augment water supplies in the province. This paper argues that although water recycling has the potential to contribute towards alleviating water scarcity, studies have shown that public perceptions greatly influence the outcome of any water recycling scheme. The study collected data using face-to-face interviews, focus group discussions, and the application of the Story with a Gap participatory exercise. One of the key findings is that residents have to trust the municipal competencies and systems, and this can be achieved through meaningful engagement between the municipality and residents. We argue that rolling out a water reuse scheme by starting with affluent areas increases the likelihood of acceptance among low-income communities.
  • Recovery of enteroviruses and poliovirus in Harare sewage using the
           bag-mediated filtration system at the introduction of the inactivated
           polio vaccine in Zimbabwe

    • Abstract: Environmental surveillance is a sensitive method for detecting circulating virus in the absence of clinical cases and is important for monitoring progress for poliovirus (PV) eradication. This study used the bag-mediated filtration system (BMFS) to determine PV and enterovirus (EV) prevalence in sewage at the transition from oral polio vaccine type 2 (OPV2) use to inactivated polio vaccine (IPV) use in Zimbabwe, and examined the correlation between environmental surveillance results and vaccination coverage of OPV. A total of 18 BMFS samples from 6 sampling sites were analysed for the presence of EV and PV via direct RT-qPCR, direct ITD (intratypic differentiation), and the WHO algorithm. EV prevalence in Harare wastewater was 88.9% (16/18) using direct RT-PCR, 61.1% (11/18) using direct ITD, and 77.8% (14/18) using the WHO algorithm. Of the 18 samples analysed using the WHO algorithm, 10 samples (55.6%) were positive for Sabin-like PV type 3 (SL3). Of these 10 samples, 2 were also positive for non-polio enteroviruses (NPEV), resulting in a total of 6 (33.3%) samples positive for NPEV and 4 negative. The sensitivity of isolation in detecting EVs in sewage was 92.9% when comparing direct RT-qPCR results to the WHO algorithm. Using direct ITD, two high-density, low-income sampling sites were negative for SL3 and one low-density, high-income sampling point was negative for SL3 using the WHO algorithm. There was a strong association between relative EV concentration and the number of OPV3 vaccine recipients (r = 0.8590; p = 0.0284) in sampled areas. This study demonstrated the ability of BMFS to detect PVs circulating in Harare wastewater at the beginning of the OPV-IPV switch and can be used to monitor potential reintroduction of wild PV or vaccine-derived PVs from endemic areas.
  • Yeast supplementation alleviates the negative effects of greywater
           irrigation on lettuce and maize

    • Abstract: Water scarcity has led to increased use of wastewater, particularly greywater, for crop irrigation. This study investigated whether the addition of yeast can alleviate the potential negative effects of greywater use on lettuce (Lactuca sativa L.) and maize (Zea mays L.). Seeds and seedlings were treated with 4 concentrations (0.005; 0.01; 0.015 and 0.020 g·mL−¹) of yeast-treated tapwater (YTW) and greywater (YGW). Tapwater (TW) and greywater (GW) without yeast served as controls. In general, an increase in yeast concentration compromised seed germination in Petri dishes, but improved germination in soil. Tapwater was more effective than GW in promoting germination and growth in both species. Lower concentrations of yeast generally increased germination capacity in both species compared to the controls. Total biomass, number of leaves, chlorophyll content, leaf area, photosynthetic rate and maximum quantum yield of photosystem II (Fv/Fm) were significantly higher in yeast treatments in both species, compared with the controls. Biomass accumulation, total leaf area, chlorophyll content and photosynthesis were higher in YGW than controls and YTW. Differences in biomass allocation between treatments may be due to changes in soil moisture, pH and electrical conductivity of the soil caused by yeast supplementation. This study showed that plants treated with YGW performed better than those treated with YTW and without yeast. Yeast supplementation of greywater could increase water recycling and provide a cheap bio-fertilizer to home growers, whilst significantly improving yield in both species. This innovative approach may enhance water and food security of subsistence farmers in rural areas.
  • Improving water use efficiency and biomass in maize, foxtail millet and
           bitter vetch by wick irrigation

    • Abstract: Water is one of the most important environmental factors in agriculture. Drought annually damages agricultural products. This loss can be reduced by some strategies. Pot and field experiments were conducted to assess the effect of wick irrigation on growth, yield and water use efficiency of maize, foxtail millet, and bitter vetch. Irrigation treatments included wick and surface irrigation (control) methods. Results of the pot experiment showed that wick irrigation had higher total fresh weight, total dry weight, and water use efficiency as compared to surface irrigation in both foxtail millet and bitter vetch. In foxtail millet, wick irrigation also had higher leaf to stem ratio, plant height, leaf relative water content and leaf area compared to surface irrigation. Results of the field experiment showed that wick irrigation increased specific leaf weight, water use efficiency, stem diameter, leaf fresh weight, total fresh weight, leaf dry weight, total dry weight, and leaf to stem ratio, but had similar fresh and dry stem weight and plant height compared to surface irrigation in maize. It is likely that the reduction in surface evaporation, reduced water consumption, and increased dry matter resulted in increased water use efficiency in wick irrigation. Overall, wick irrigation had higher water use efficiency, biomass, and plant growth compared to surface irrigation in maize, foxtail millet and bitter vetch.
  • Evaluation of nitrate redistribution in surface and subsurface drip
           irrigation systems

    • Abstract: Nitrogen compounds added to the soil may convert to nitrate and cause contamination. The distribution and uniformity of soil nitrate in surface vs. subsurface drip irrigation systems were compared in a physical model consisting of a transparent glass box (1.20 x 0.5 x 1 m) and sandy loam soil, and considering emitter installation depths of 0 and 30 cm, discharge rates of Q1 = 2, Q2 = 4, Q3 = 8 L/h, and fertilizer levels of S1 = 125, S2 = 250, S3 = 375 mg/L. Irrigation continued for 6 h and nitrate and moisture sampling was performed for 68 h after the initiation of water front advance. The result showed that doubling the discharge caused the wetted area to triple in size in the subsurface drip irrigation system whereas it only doubled in size in the surface drip irrigation system. Thus in the subsurface system, when increasing the fertilizer level, the nitrate spread out extensively and therefore its concentration was greatly reduced. Also, by increasing discharge, the difference in soil nitrate concentration between the two systems increases because of increasing non-uniformity of nitrate distribution in the surface system, such that by increasing the fertilizer concentration form 125 to 375 mg/L, the difference in nitrate concentration increases from 22% to 500% (for Q1 = 2 L/h), 43% to 352% (for Q2 = 4 L/h), and 14% to 166% (for Q3 = 8 L/h). Thus the subsurface drip irrigation system has a more uniform trend of nitrate distribution than the surface drip irrigation system. Also, treatment with maximum flow and fertilizer level will create the most optimal nitrate concentration in the soil.
  • Seasonal and interannual variability of residence time and total
           phosphorus in a small hypereutrophic lake in the Brazilian northeast

    • Abstract: This study evaluates the residence time (RT) and total phosphorus (TP) in a small hypereutrophic lake in the city of Fortaleza, Brazil. The results indicate that RT predicted by a complete-mix model is very similar (R² = 0.83) to that simulated with a 2-D hydrodynamic model (CE-QUAL-W2). Simple power-laws were fitted to describe RT and TP concentration at the lake inlet as functions of lake inflow, yielding correlations of R² = 0.84 and 0.70, respectively. The combination of these correlations with a complete-mix approach provided a comprehensive model that predicted TP values measured at the lake outlet reasonably well (R² = 0.60). In addition, a direct empirical correlation between simulated TP concentration and precipitation was also obtained. The simulations indicate a nearly periodic behaviour of RT and TP, with the seasonal variations being much higher than the interannual ones. Finally, an application of the model showed that a reduction of 99% of the input TP load was required to reach 100% compliance with the required water quality standards; this could be achieved by connecting the residences to the sewage network. The methodology proposed in this research can be easily applied to other lakes in the Brazilian northeast and extended to other tropical regions around the globe.
  • Comparison of classic and chemometric methods used for phosphate removal
           from fresh human urine under optimum conditions

    • Abstract: Human urine constitutes 1% of domestic wastewater and can be used to recover nitrogen and phosphorus when collected separately at source. Sustainable nutrient (nitrogen, phosphate, potassium) cycling requires the recovery of these valuable resources from human urine. As nitrogen and phosphorus are valuable nutrients needed for plant growth, these components of urine are an excellent fertilizer. Phosphorus can be applied in natural fertilizers and in addition the pollution load of wastewater treatment plants is reduced. Different nutrient removal and recovery methods from urine have been studied at lab scale, but none so far has reached technological competence and none has been extended to practical use. The focus of this study was to evaluate electrocoagulation as a process for the removal of phosphate from fresh human urine using iron plate electrodes. The effect of pH and current density on phosphate removal was investigated. While determining the optimum conditions for removal, classical and chemometric methods were compared. Using the central composite design (CCD), optimum conditions were determined with only 13 experiments, and time and labour savings were achieved compared to the classical method. Initial pH values and current density were controlled within the range of pH 5-9 and current density 12-40 mA/cm². From the obtained results, it was found that optimal initial current density is 40 mA/cm² for both methods, and optimal pH is 7 for the classical method and 6.24 for CCD, which is the natural pH of human urine. Realization of phosphate removal using optimum conditions discovered with CCD, provides savings on experimental effort, time, chemicals and energy consumption, and will contribute to resource recovery, reduction of wastewater load and sustainable fertilizer production.
  • Optimization, characterization and adsorption properties of natural
           calcite for toxic As(III) removal from aqueous solutions

    • Abstract: The potential of natural (N) and magnetized (M) forms of different rocks (calcite and dolomite) and clays (bentonite, kaolinite, and hematite) were evaluated for the removal of As(III) from aqueous solutions, in order to optimize and scrutinize the most suitable adsorbent. The order observed for efficiency of As(III) removal was N-calcite > N-dolomite > M-calcite > M-dolomite > N-bentonite > M-bentonite > M-kaolinite > N-kaolinite > M-hematite > N-hematite. On the basis of this analysis, natural calcite was further selected for in-depth analysis of various adsorption parameters such as time, pH, temperature, dosage, and concentration of As(III) ions. An excellent adsorption capacity of 19.05 mg·g-1 was displayed by calcite for As(III), which was significantly higher than that previously reported for other studies. The characterization of adsorbent calcite was performed by various analytical techniques: XRD, XRF, FTIR, SEM-EDS, TG/DTA and PZC. The kinetic investigation revealed that the adsorbent successfully removed over 98% of As(III) from aqueous solution after 160 minutes of equilibration time. The adsorption data was well fitted to the Freundlich isotherm model and fairly described by the pseudo-second-order mechanism. The mean energy of adsorption (E) determined from the Dubinin-Radushkevich (D-R) model was less than 8 kJ·mol-1, which indicates a physical adsorption process. The calculated thermodynamic parameters revealed that the adsorption of As(III) by calcite is endothermic, favourable and spontaneous.
  • Removal of Pb2+ ions from synthetic wastewater using functionalized
           multi-walled carbon nanotubes decorated with green synthesized iron
           oxide-gold nanocomposite

    • Abstract: Purification of wastewater before it is discharged into the aquatic environment is important in order to prevent pollution of clean water. This study investigated the applicability of functionalized multi-walled carbon nanotubes (MWCNTs) decorated with gold-iron oxide nanoparticles for the adsorptive removal of Pb2+ from synthetic wastewater. CNTs were commercially obtained and functionalized with a mixture of H2SO4/HNO3 acids. The CNTs were coated with gold-iron oxide nanoparticles, to enhance the adsorption of heavy metals. The gold-iron oxide nanoparticles were synthesized by reacting green tea leaf extract with iron chloride (FeCl2) and gold (III) chloride (HAuCl4) precursors. The composite was cross-linked using N, N-dimethylformadide (DMF). The adsorbents were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to assess their surface morphology, Fourier transform infrared (FTIR) spectroscopy to identify the functional groups present, X-ray diffraction (XRD) to ascertain the crystallographic structure of the green adsorbent and Raman spectroscopy to determine the sample purity. SEM results showed highly agglomerated and polydispersed nanoparticles, owing to the presence of phytochemicals in the tea extract and magnetic interaction between the individual particles indicating the successful synthesis of Au/Fe3O4 adsorbent. Furthermore, an increase in the amount of Pb2+ removed per unit mass (q e) of adsorbent from 1.233 to 7.266 mg·g-1 at 298 K was observed. A high sorption capacity was noticed for MWCNT-Au/Fe3O4 as compared to the MWCNT-COOH. The Pb2+ removal percentage increased from 50% to 78% with an increase in MWCNT-Au/Fe3O4 dosage from 0.02 g to 0.1 g. Adsorption isotherm data fitted well to the Freundlich and Langmuir isotherm models for MWCNT-COOH and MWCNT-Au/Fe3O4 adsorbents and the rate of Pb(II) adsorption by MWCNT-Au/Fe3O4 encountered an increase with increasing solution temperature and followed the pseudo-second-order model. The synthesized MWCNT-Au/Fe3O4 has good potential in removing heavy metals from wastewater.
  • Experimental investigation of the discharge coefficient of labyrinth weirs
           with asymmetric cycles

    • Abstract: This study investigated the discharge coefficient in asymmetric rectangular labyrinth weirs. A dimensional analysis was carried out which showed that the discharge coefficient is a function of dimensionless parameters, such as the ratio of asymmetric widths of left and right cycles (wL/wR), the ratio of the total hydraulic head to the weir height (Ht/P), and the weir length ratio (B/w avg). The experimental results for the discharge coefficient were found to decline as wL/wR increased or B/w avg decreased. For wL/wR = 1.19, the ratio B/w avg = 2.76 improves the discharge coefficient by nearly 12.7% compared to B/w avg = 3.1. For wL/wR = 1.42, the ratio B/w avg = 2.76 improves the discharge coefficient by nearly 34.2% compared to B/w avg = 3.1. For wL/wR = 1.70, the ratio B/w avg = 2.76 improves the discharge coefficient by nearly 30% compared to B/w avg = 3.1.
  • Assessment of multiple precipitation interpolation methods and uncertainty
           analysis of hydrological models in Chaohe River basin, China

    • Abstract: Precipitation interpolation is widely used to generate continuous rainfall surfaces for hydrological simulations. However, increasing the precision of values at the unknown points generated by different spatial interpolation methods is challenging. This study used the Chaohe River Basin, which is an important source of Beijing's drinking water, as a research area to comprehensively evaluate several precipitation interpolation methods (Thiessen polygon, inverse distance weighting, ordinary kriging and ANUSPLIN) for inputs in hydrological simulations. This research showed that the precipitation time-series surface generated using the ANUSPLIN interpolation method had higher accuracy and reliability. Using this precipitation input to drive the hydrological models, we explored the parameter uncertainties of four typical hydrological models (GR4J, IHACRES, Sacramento and MIKE SHE) based on the multi-objective generalized likelihood uncertainty estimation (GLUE) method. The GLUE method was used to study the parameter sensitivity and uncertainty of the model. Results showed that the ANUSPLIN precipitation interpolation surface combined with the Sacramento model performed best. The multi-objective GLUE method had obvious advantages in parameter uncertainty analysis in hydrological models. Simultaneously exploring the convex line and point density distributions of the behavioural parameters with multi-objective functions determined their distribution and sensitivity more effectively.
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