Pub Date : 2022-04-27DOI: 10.17159/wsa/2022.v48.i2.3908
Zakaria A Mohamed, Saad Alamri, Mohamed Hashem
The present study determines the endotoxin removal efficiency of drinking water treatment plants (DWTPs) in Egypt, as examples of conventional treatment methods used in developing countries. The total endotoxin in source water (Nile River) of these DWTPs ranged from 57 to 187 EU∙mL−1, depending on the location of treatment plants. Coagulation/ flocculation/sedimentation (C/F/S) after chlorine pre-oxidation removed bound endotoxins by 76.1–85.5%, but caused cell lysis and increased free endotoxins by 28.2–33.3% of those detected in raw waters. Rapid sand filtration had not significant effect on free endotoxins, but reduced bound endotoxins by 23–33.3%. Final chlorine disinfection also reduced bound endotoxins to levels around 1 EU/mL, accompanied by an increase in free endotoxins (37–112 EU∙mL−1) in finished waters. Simultaneously, final chlorine disinfection removed all heterotrophic bacteria, with low cyanobacterial cell numbers (348–2 450 cells∙mL−1) detected in finished waters. Overall, conventional treatment processes at these DWTPs could removal substantial amounts of bound endotoxins and bacterial cells, but increase free endotoxins through cell lysis induced by pre-oxidation and final chlorine disinfection. The study suggests that conventional processes at DWTPs should be optimized and upgraded to improve their performance in endotoxin removal and ensure safe distribution of treated water to consumers.
{"title":"Endotoxin removal efficiency in conventional drinking water treatment plants, a case study in Egypt","authors":"Zakaria A Mohamed, Saad Alamri, Mohamed Hashem","doi":"10.17159/wsa/2022.v48.i2.3908","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i2.3908","url":null,"abstract":"The present study determines the endotoxin removal efficiency of drinking water treatment plants (DWTPs) in Egypt, as examples of conventional treatment methods used in developing countries. The total endotoxin in source water (Nile River) of these DWTPs ranged from 57 to 187 EU∙mL−1, depending on the location of treatment plants. Coagulation/ flocculation/sedimentation (C/F/S) after chlorine pre-oxidation removed bound endotoxins by 76.1–85.5%, but caused cell lysis and increased free endotoxins by 28.2–33.3% of those detected in raw waters. Rapid sand filtration had not significant effect on free endotoxins, but reduced bound endotoxins by 23–33.3%. Final chlorine disinfection also reduced bound endotoxins to levels around 1 EU/mL, accompanied by an increase in free endotoxins (37–112 EU∙mL−1) in finished waters. Simultaneously, final chlorine disinfection removed all heterotrophic bacteria, with low cyanobacterial cell numbers (348–2 450 cells∙mL−1) detected in finished waters. Overall, conventional treatment processes at these DWTPs could removal substantial amounts of bound endotoxins and bacterial cells, but increase free endotoxins through cell lysis induced by pre-oxidation and final chlorine disinfection. The study suggests that conventional processes at DWTPs should be optimized and upgraded to improve their performance in endotoxin removal and ensure safe distribution of treated water to consumers.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"11 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84264443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-27DOI: 10.17159/wsa/2022.v48.i2.3848.1
D van der Spuy, JA du Plessis
Statistical flood frequency analyses of observed flow data are applied to develop regional empirical and deterministic design flood estimation methods, particularly for application in cases where no, or insufficient, streamflow data are available. The soundness of the statistical approach, in the estimation of flood peak frequencies, depends on the availability of long records with good-quality observed flow data. With flood frequency methods currently under review in South Africa, a sound statistical approach is considered essential. This paper reviews the statistical flood frequency approach in South Africa, which includes an appraisal of the capability of the most commonly used probability distributions in South Africa to properly cope with the challenges encountered in a flood frequency analysis, based on extended experience in flood hydrology. All the distributions tend to perform poorly when lower probability frequency events are estimated, especially where outliers are present in the dataset. Research needs are identified to improve flood peak frequency estimation techniques, and practical pointers are suggested for the interim, in anticipation of updated methods. The importance of a visual interpretation of the data is highlighted to minimise the risk of not selecting the most appropriate distribution.
{"title":"Flood frequency analysis – Part 1: Review of the statistical approach in South Africa","authors":"D van der Spuy, JA du Plessis","doi":"10.17159/wsa/2022.v48.i2.3848.1","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i2.3848.1","url":null,"abstract":"Statistical flood frequency analyses of observed flow data are applied to develop regional empirical and deterministic design flood estimation methods, particularly for application in cases where no, or insufficient, streamflow data are available. The soundness of the statistical approach, in the estimation of flood peak frequencies, depends on the availability of long records with good-quality observed flow data. With flood frequency methods currently under review in South Africa, a sound statistical approach is considered essential. This paper reviews the statistical flood frequency approach in South Africa, which includes an appraisal of the capability of the most commonly used probability distributions in South Africa to properly cope with the challenges encountered in a flood frequency analysis, based on extended experience in flood hydrology. All the distributions tend to perform poorly when lower probability frequency events are estimated, especially where outliers are present in the dataset. Research needs are identified to improve flood peak frequency estimation techniques, and practical pointers are suggested for the interim, in anticipation of updated methods. The importance of a visual interpretation of the data is highlighted to minimise the risk of not selecting the most appropriate distribution.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"60 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80489917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-27DOI: 10.17159/wsa/2022.v48.i2.3903
Ezekiel A Adetoro, Samson O Ojoawo, AM Salman
The adsorption of eight selected potentially toxic metal ions from actual mining wastewater obtained from Igbeti, Nigeria, was established using activated carbon chemically prepared from Carica papaya stem with zinc chloride (CPSAC-ZnCl2) as activating agent. Characterization of the prepared CPSAC-ZnCl2 sample for surface morphology and functional groups was done by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. An atomic absorption spectrophotometer (AAS) was utilized for characterization of the selected metals in the mining wastewater. Batch adsorption and desorption studies were conducted on removal of the metals from the sample using CPSAC-ZnCl2. The data obtained were fitted to isotherm (Freundlich and Langmuir); kinetic (pseudo-second-order and intra-particle diffusion) and thermodynamic (standard enthalpy change – ΔH°, entropy change – ΔS° and free energy change – ΔG°) models. These were considered under two error functions (sum of absolute errors – SAE, coefficient of determination – R2) of linear and non-linear regression analyses. The SEM micrograph revealed that the CPSAC-ZnCl2 sample was 2.0–50.0 nm with FTIR spectra absorption peaks ranging from 746.2 to 3 987.0 cm-1. The initial concentrations of selected metals in the wastewater varied from 5.7 to 756.5 mg/L. The adsorbent dosage, agitation rate, contact time, pH and temperature for optimum condition of CPSAC-ZnCl2 were 0.6 g, 150.0 r/min, 60 min, pH of 7.0 and 30°C, respectively. The selected metals’ adsorption onto CPSAC-ZnCl2 followed Freundlich and Langmuir isotherm models pseudo-second-order kinetics with intra-particle diffusion mechanism. The ΔH°, ΔS° and ΔG° for the processes were 134.5, 64.5 and 22 012.0 kJ/mol, respectively. The adsorbent achieved an adsorption efficiency of above 95.0%, and is thus recommended for industrial application in remediating potentially toxic metals from wastewater.
{"title":"Adsorption and desorption studies of Carica papaya stem activated with zinc chloride for mining wastewater treatment","authors":"Ezekiel A Adetoro, Samson O Ojoawo, AM Salman","doi":"10.17159/wsa/2022.v48.i2.3903","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i2.3903","url":null,"abstract":"The adsorption of eight selected potentially toxic metal ions from actual mining wastewater obtained from Igbeti, Nigeria, was established using activated carbon chemically prepared from Carica papaya stem with zinc chloride (CPSAC-ZnCl2) as activating agent. Characterization of the prepared CPSAC-ZnCl2 sample for surface morphology and functional groups was done by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. An atomic absorption spectrophotometer (AAS) was utilized for characterization of the selected metals in the mining wastewater. Batch adsorption and desorption studies were conducted on removal of the metals from the sample using CPSAC-ZnCl2. The data obtained were fitted to isotherm (Freundlich and Langmuir); kinetic (pseudo-second-order and intra-particle diffusion) and thermodynamic (standard enthalpy change – ΔH°, entropy change – ΔS° and free energy change – ΔG°) models. These were considered under two error functions (sum of absolute errors – SAE, coefficient of determination – R2) of linear and non-linear regression analyses. The SEM micrograph revealed that the CPSAC-ZnCl2 sample was 2.0–50.0 nm with FTIR spectra absorption peaks ranging from 746.2 to 3 987.0 cm-1. The initial concentrations of selected metals in the wastewater varied from 5.7 to 756.5 mg/L. The adsorbent dosage, agitation rate, contact time, pH and temperature for optimum condition of CPSAC-ZnCl2 were 0.6 g, 150.0 r/min, 60 min, pH of 7.0 and 30°C, respectively. The selected metals’ adsorption onto CPSAC-ZnCl2 followed Freundlich and Langmuir isotherm models pseudo-second-order kinetics with intra-particle diffusion mechanism. The ΔH°, ΔS° and ΔG° for the processes were 134.5, 64.5 and 22 012.0 kJ/mol, respectively. The adsorbent achieved an adsorption efficiency of above 95.0%, and is thus recommended for industrial application in remediating potentially toxic metals from wastewater. \u0000 ","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"28 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84424307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-27DOI: 10.17159/wsa/2022.v48.i2.3923
Mafaniso Hara
Small-scale fisheries play a significant role in livelihoods and food and nutrition security for millions of people around the world. However, these benefits are under threat, especially in developing countries such as in Africa, as a result of poor governance. The historical developmentalist and welfarist approach to management of small-scale fisheries in developing countries, dating back from colonial era, has resulted in problems of open-access regimes that usually lead to over-capitalisation, geographic spread of landing sites that makes it difficult to organise fishers for management activities, inadequate management capacity and poor funding of the sector. These lead to over-exploitation and degradation of fish resources, thereby negatively impacting the current and long-term benefits for small-scale fishing communities and society at large. Most countries that start off with such problematic fisheries management regimes and set on this path find it very difficult to reform the regimes. This article argues that South Africa needs to draw lessons from the mistakes of other (developing) countries in terms of the type of fisheries management regime governing small-scale fisheries, as it sets up and creates a new inland small-scale fisheries sector. Such ‘path dependence’ can set a country on courses of action and decisions that are extremely difficult to reverse and extricate a country from. There is no doubt of the need for more equitable distribution of access rights and benefits to inland fisheries for communities that had been excluded and marginalised under colonialism and apartheid. However, this has to been done without endangering the fish resources and in effect the very sustainable social-economic benefits that such reforms intend to achieve.
{"title":"Establishing an economically and biologically sustainable and viable inland fisheries sector in South Africa – pitfalls of ‘path dependence’","authors":"Mafaniso Hara","doi":"10.17159/wsa/2022.v48.i2.3923","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i2.3923","url":null,"abstract":"Small-scale fisheries play a significant role in livelihoods and food and nutrition security for millions of people around the world. However, these benefits are under threat, especially in developing countries such as in Africa, as a result of poor governance. The historical developmentalist and welfarist approach to management of small-scale fisheries in developing countries, dating back from colonial era, has resulted in problems of open-access regimes that usually lead to over-capitalisation, geographic spread of landing sites that makes it difficult to organise fishers for management activities, inadequate management capacity and poor funding of the sector. These lead to over-exploitation and degradation of fish resources, thereby negatively impacting the current and long-term benefits for small-scale fishing communities and society at large. Most countries that start off with such problematic fisheries management regimes and set on this path find it very difficult to reform the regimes. This article argues that South Africa needs to draw lessons from the mistakes of other (developing) countries in terms of the type of fisheries management regime governing small-scale fisheries, as it sets up and creates a new inland small-scale fisheries sector. Such ‘path dependence’ can set a country on courses of action and decisions that are extremely difficult to reverse and extricate a country from. There is no doubt of the need for more equitable distribution of access rights and benefits to inland fisheries for communities that had been excluded and marginalised under colonialism and apartheid. However, this has to been done without endangering the fish resources and in effect the very sustainable social-economic benefits that such reforms intend to achieve.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"13 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84320407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-27DOI: 10.17159/wsa/2022.v48.i2.3848.2
D van der Spuy, JA du Plessis
The original plotting position concept was suggested more than a century ago. Since then, many alternative plotting position approaches have been developed. Despite a general lack of agreement around which plotting position is theoretically ‘correct’ and the ‘best’ to use, all plotting positions fail to adequately address outliers and data of similar magnitude. Hydrologists generally fail to acknowledge that the plotting position primarily offers an informative display of data, against which distributions can be compared, rather than an absolute measure of probability. This paper does not intend to challenge any of the many lengthy theoretical mathematical arguments, utilised to ‘prove’ why one plotting position is superior to the others. These theoretical arguments may very well be valid for a ‘population’ of flood peaks – the reality, however, is that hydrologists are confronted with the challenge of analysing very limited ‘samples’ of the population. Consequently, the plotting position issue demands a more pragmatic approach, rather than a purely theoretical approach. This paper illustrates various problems with existing plotting position techniques in use and offers an alternative approach and a more sensible plotting position technique, using Z-scores and referred to as the Z-set PP, against which distributions can be checked. The study further illustrates how effectively the Z‑set PP deals with outliers and its robustness with various record lengths. Although derived from a study of flood peak data obtained from South African flow-gauging sites, it is deemed that it will be universally applicable.
{"title":"Flood frequency analysis – Part 2: Development of a modified plotting position","authors":"D van der Spuy, JA du Plessis","doi":"10.17159/wsa/2022.v48.i2.3848.2","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i2.3848.2","url":null,"abstract":"The original plotting position concept was suggested more than a century ago. Since then, many alternative plotting position approaches have been developed. Despite a general lack of agreement around which plotting position is theoretically ‘correct’ and the ‘best’ to use, all plotting positions fail to adequately address outliers and data of similar magnitude. Hydrologists generally fail to acknowledge that the plotting position primarily offers an informative display of data, against which distributions can be compared, rather than an absolute measure of probability. This paper does not intend to challenge any of the many lengthy theoretical mathematical arguments, utilised to ‘prove’ why one plotting position is superior to the others. These theoretical arguments may very well be valid for a ‘population’ of flood peaks – the reality, however, is that hydrologists are confronted with the challenge of analysing very limited ‘samples’ of the population. Consequently, the plotting position issue demands a more pragmatic approach, rather than a purely theoretical approach. This paper illustrates various problems with existing plotting position techniques in use and offers an alternative approach and a more sensible plotting position technique, using Z-scores and referred to as the Z-set PP, against which distributions can be checked. The study further illustrates how effectively the Z‑set PP deals with outliers and its robustness with various record lengths. Although derived from a study of flood peak data obtained from South African flow-gauging sites, it is deemed that it will be universally applicable.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"38 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85493744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-27DOI: 10.17159/wsa/2022.v48.i2.3918
Heidi Steffen, Caylin Bosch, Gideon Wolfaardt, Alfred Botha
South Africa’s rivers are frequently used by communities lacking proper sanitation infrastructure for domestic purposes; however, these surface waters may pose a health risk to immunocompromised individuals due to the presence of opportunistic pathogenic fungi in the polluted water. Although only a few studies have focused on the presence of clinically relevant fungal species in South African rivers, many known opportunistic pathogenic species were found to be predominant in these waters. Furthermore, strong evidence exists that increased numbers of clinically relevant species may be observed in future due to fungi acquiring thermotolerance in response to the global increase in temperature. Thermotolerance is a major factor contributing to pathogenesis in fungi, due to the generally low tolerance of most fungi toward mammalian body temperatures. It is therefore contended that combinatorial effects of water pollution and rising environmental temperatures could lead to an increase in the incidence of mycoses in South Africa. This is especially concerning since a relatively large population of immunocompromised individuals, represented mostly by HIV-infected people, resides in the country.
{"title":"Rising environmental temperatures and polluted surface waters: the prelude to the rise of mycoses in South Africa","authors":"Heidi Steffen, Caylin Bosch, Gideon Wolfaardt, Alfred Botha","doi":"10.17159/wsa/2022.v48.i2.3918","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i2.3918","url":null,"abstract":"South Africa’s rivers are frequently used by communities lacking proper sanitation infrastructure for domestic purposes; however, these surface waters may pose a health risk to immunocompromised individuals due to the presence of opportunistic pathogenic fungi in the polluted water. Although only a few studies have focused on the presence of clinically relevant fungal species in South African rivers, many known opportunistic pathogenic species were found to be predominant in these waters. Furthermore, strong evidence exists that increased numbers of clinically relevant species may be observed in future due to fungi acquiring thermotolerance in response to the global increase in temperature. Thermotolerance is a major factor contributing to pathogenesis in fungi, due to the generally low tolerance of most fungi toward mammalian body temperatures. It is therefore contended that combinatorial effects of water pollution and rising environmental temperatures could lead to an increase in the incidence of mycoses in South Africa. This is especially concerning since a relatively large population of immunocompromised individuals, represented mostly by HIV-infected people, resides in the country.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"25 8 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82695692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-25DOI: 10.17159/wsa/2022.v48.i2.3917
HE Jacobs, ML Crouch, A Ilemobade, JL du Plessis
Per capita water use is commonly employed in single-parameter models to estimate water demand, especially in regions where model input parameters are limited. Research has confirmed that the serviced population and household size positively correlate with water consumption, but the per capita consumption of household members decreases with increased household size. A central issue driving this study was the lack of an up-to-date per capita household water use guideline in the South African context. This study followed a process of explicit reasoning and inference, informed by an extensive knowledge review, stakeholder input and interrogation of relevant data, to develop a novel per capita water use estimation tool. Five main parameters were included, namely: (i) level of water service provided, (ii) usage scenario, (iii) household size (people per household), (iv) geographic region, and (v) regional property value. A Microsoft Excel–based tool was developed and is supplied online as supplementary material with this publication. The litres per capita per day tool (LCD-tool) allows for robust per capita water use estimates, as a function of the above five input parameters. The Microsoft Excel LCD-tool provides benchmarks for different South African conditions, described by context-specific service levels. The planning and management of water supply and distribution systems could benefit from the findings of this study.
{"title":"Per capita water consumption for benchmarked South African service levels derived by means of explicit reasoning","authors":"HE Jacobs, ML Crouch, A Ilemobade, JL du Plessis","doi":"10.17159/wsa/2022.v48.i2.3917","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i2.3917","url":null,"abstract":"Per capita water use is commonly employed in single-parameter models to estimate water demand, especially in regions where model input parameters are limited. Research has confirmed that the serviced population and household size positively correlate with water consumption, but the per capita consumption of household members decreases with increased household size. A central issue driving this study was the lack of an up-to-date per capita household water use guideline in the South African context. This study followed a process of explicit reasoning and inference, informed by an extensive knowledge review, stakeholder input and interrogation of relevant data, to develop a novel per capita water use estimation tool. Five main parameters were included, namely: (i) level of water service provided, (ii) usage scenario, (iii) household size (people per household), (iv) geographic region, and (v) regional property value. A Microsoft Excel–based tool was developed and is supplied online as supplementary material with this publication. The litres per capita per day tool (LCD-tool) allows for robust per capita water use estimates, as a function of the above five input parameters. The Microsoft Excel LCD-tool provides benchmarks for different South African conditions, described by context-specific service levels. The planning and management of water supply and distribution systems could benefit from the findings of this study.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"23 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87185142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-26DOI: 10.17159/wsa/2022.v48.i1.3891
Sesethu Fikileni, Piotr Wolski
Hydrological forecasting becomes an important tool in water resources management in forecasting the future state of the water resources in a catchment. The need for a reliable seasonal hydrologic forecast is significant and is becoming even more urgent under future climate conditions, as the assimilation of seasonal forecast information in decision making becomes part of the short and long-term climate change adaptation strategies in a range of contexts, such as energy supply, water supply and management, rural-urban, agriculture, infrastructure and disaster preparedness and relief. This work deals with the framework for implementation of the Pitman-WR2012 model in a hydrological forecasting mode. The Pitman-WR2012 model was forced with 10-member ensemble seasonal climate forecast from Climate Forecast Systems v.2 (CFSv2), which is downscaled using the principal components regression (PCR) approach. The generated seasonal hydrological forecast focused on the summer season, in particular on the Dec–Jan–Feb (DJF) period, which is the rainy season in the studied catchment (Kraai River catchment in the Eastern Cape Province of South Africa). The hydrological forecast issued at the end of November showed skill in December and February (assessed through Receiver Operating Characteristic (ROC) and Ranked Probability Skill Score (RPSS)), with poorer skill in January. Importantly, the skill of streamflow forecast was better than that of rainfall forecast, which likely results from the influence of the initial conditions of the hydrological model. In conclusion Pitman-WR2012 model performed realistically when implemented in seasonal hydrological forecasts mode, and it is important that in that mode the model is run with near-real-time rainfall data in order to maximize forecast skill arising from initial conditions.
水文预报是水资源管理中预测流域未来水资源状况的重要工具。对可靠的季节性水文预报的需求是巨大的，而且在未来气候条件下变得更加迫切，因为在决策过程中吸收季节性预报信息已成为能源供应、供水和管理、城乡、农业、基础设施以及备灾和救灾等一系列情况下的短期和长期气候变化适应战略的一部分。这项工作涉及在水文预报模式中实施Pitman-WR2012模型的框架。Pitman-WR2012模式是用来自气候预报系统v.2的10元集合季节气候预报进行强迫的(CFSv2)，使用主成分回归(PCR)方法进行了缩减。生成的季节性水文预报侧重于夏季，特别是12月至1月至2月(DJF)期间，这是所研究的集水区(南非东开普省的Kraai河集水区)的雨季。11月底发布的水文预报在12月和2月(通过Receiver Operating Characteristic (ROC)和rank Probability skill Score (RPSS)评估)表现出较好的技能，1月的技能较差。重要的是，流量预报的技巧要优于降雨预报，这可能是由于水文模型初始条件的影响。总之，Pitman-WR2012模型在季节性水文预报模式下的表现是真实的，在该模式下，为了最大限度地提高初始条件引起的预报技能，重要的是使用近实时降雨数据运行模型。
{"title":"Framework for implementation of the Pitman-WR2012 model in seasonal hydrological forecasting: a case study of Kraai River, South Africa","authors":"Sesethu Fikileni, Piotr Wolski","doi":"10.17159/wsa/2022.v48.i1.3891","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i1.3891","url":null,"abstract":"Hydrological forecasting becomes an important tool in water resources management in forecasting the future state of the water resources in a catchment. The need for a reliable seasonal hydrologic forecast is significant and is becoming even more urgent under future climate conditions, as the assimilation of seasonal forecast information in decision making becomes part of the short and long-term climate change adaptation strategies in a range of contexts, such as energy supply, water supply and management, rural-urban, agriculture, infrastructure and disaster preparedness and relief. This work deals with the framework for implementation of the Pitman-WR2012 model in a hydrological forecasting mode. The Pitman-WR2012 model was forced with 10-member ensemble seasonal climate forecast from Climate Forecast Systems v.2 (CFSv2), which is downscaled using the principal components regression (PCR) approach. The generated seasonal hydrological forecast focused on the summer season, in particular on the Dec–Jan–Feb (DJF) period, which is the rainy season in the studied catchment (Kraai River catchment in the Eastern Cape Province of South Africa). The hydrological forecast issued at the end of November showed skill in December and February (assessed through Receiver Operating Characteristic (ROC) and Ranked Probability Skill Score (RPSS)), with poorer skill in January. Importantly, the skill of streamflow forecast was better than that of rainfall forecast, which likely results from the influence of the initial conditions of the hydrological model. In conclusion Pitman-WR2012 model performed realistically when implemented in seasonal hydrological forecasts mode, and it is important that in that mode the model is run with near-real-time rainfall data in order to maximize forecast skill arising from initial conditions.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"13 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87197141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-26DOI: 10.17159/wsa/2022.v48.i1.3910
Moustafa S Darweesh
In this study, finite element analysis (SAP2000 program) was used to investigate the relationship between the pressure and leakage area in 90° pipe elbows with longitudinal, spiral, and circumferential cracks. The results show that leakage areas expand linearly as the internal pressure increases and its inclination is called the pressure–area slope (m). A sensitivity study was conducted to recognize the influence of different parameters (inside diameter, wall thickness, modulus of elasticity, longitudinal stress, Poisson’s ratio, and finally crack orientation) on both m and leakage exponent (N). The results reveal that the elasticity modulus has the dominant impact on m, followed by elbow wall thickness, and then elbow inside-diameter. The Poisson’s ratio and the longitudinal stress have an insignificant influence on m. Moreover, the slope m varies more in the longitudinal and spiral cracks than the circumferential cracks. The amount of leakage through the different cracks is a function of the internal pressure raised to an exponent ranging from 0.5 to 1.01. An attempt was made to find empirical equations to express the pressure–area slope as a function of elbow properties and crack orientation. The study’s findings were checked against numerical and experimental results and good correlations were obtained.
{"title":"Predicting the head leakage behaviour of cracks in pipe elbows","authors":"Moustafa S Darweesh","doi":"10.17159/wsa/2022.v48.i1.3910","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i1.3910","url":null,"abstract":"In this study, finite element analysis (SAP2000 program) was used to investigate the relationship between the pressure and leakage area in 90° pipe elbows with longitudinal, spiral, and circumferential cracks. The results show that leakage areas expand linearly as the internal pressure increases and its inclination is called the pressure–area slope (m). A sensitivity study was conducted to recognize the influence of different parameters (inside diameter, wall thickness, modulus of elasticity, longitudinal stress, Poisson’s ratio, and finally crack orientation) on both m and leakage exponent (N). The results reveal that the elasticity modulus has the dominant impact on m, followed by elbow wall thickness, and then elbow inside-diameter. The Poisson’s ratio and the longitudinal stress have an insignificant influence on m. Moreover, the slope m varies more in the longitudinal and spiral cracks than the circumferential cracks. The amount of leakage through the different cracks is a function of the internal pressure raised to an exponent ranging from 0.5 to 1.01. An attempt was made to find empirical equations to express the pressure–area slope as a function of elbow properties and crack orientation. The study’s findings were checked against numerical and experimental results and good correlations were obtained.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"24 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77837966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-26DOI: 10.17159/wsa/2022.v48.i1.3926
C. O. Ataguba, I. Brink
Oil and grease (O&G) removal efficiencies using 4 automobile stormwater treatment systems were investigated and compared. The treatment systems used were: low-cost granular activated carbon–rice husk (GAC–RH) filter system, river gravel–granular activated carbon (GR–GAC) filter system, rice husk only (RH) filter system and the conventional PVC O&G trap (COT). Sampling of automobile stormwater from the five selected automobile workshops was carried out using the manual grab sampling methods. The treatment involved filtration using the low-cost technologies and O&G separation from stormwater. GAC–RH exhibited the highest O&G removal with an average removal efficiency of 43.2% from all the automobile workshops, followed by RH with an average removal efficiency of 31%. O&G removal using GR–GAC and COT resulted in average removal efficiencies of 28.6% and 26.8%, respectively. Further studies need to be carried out to optimize the GAC and RH low-cost filter materials for the purpose of achieving the USEPA and Nigerian effluent standards of 0.1 mg/L, since all the treatment systems produced effluents with minimum concentrations ranging between 0.8 mg/L and 3.6 mg/L.
{"title":"A comparison of oil and grease removal from automobile workshop stormwater runoff using gravel, granular activated carbon, rice husk and conventional oil and grease (O&G) trap","authors":"C. O. Ataguba, I. Brink","doi":"10.17159/wsa/2022.v48.i1.3926","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i1.3926","url":null,"abstract":"Oil and grease (O&G) removal efficiencies using 4 automobile stormwater treatment systems were investigated and compared. The treatment systems used were: low-cost granular activated carbon–rice husk (GAC–RH) filter system, river gravel–granular activated carbon (GR–GAC) filter system, rice husk only (RH) filter system and the conventional PVC O&G trap (COT). Sampling of automobile stormwater from the five selected automobile workshops was carried out using the manual grab sampling methods. The treatment involved filtration using the low-cost technologies and O&G separation from stormwater. GAC–RH exhibited the highest O&G removal with an average removal efficiency of 43.2% from all the automobile workshops, followed by RH with an average removal efficiency of 31%. O&G removal using GR–GAC and COT resulted in average removal efficiencies of 28.6% and 26.8%, respectively. Further studies need to be carried out to optimize the GAC and RH low-cost filter materials for the purpose of achieving the USEPA and Nigerian effluent standards of 0.1 mg/L, since all the treatment systems produced effluents with minimum concentrations ranging between 0.8 mg/L and 3.6 mg/L.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"16 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89497947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：