Pub Date : 2023-10-27DOI: 10.17159/wsa/2023.v49.i4.4002
None JK Turpie, None GK Letley
The City of Cape Town experienced a serious drought between 2016 and 2018 which led to severe water shortages and concerns for the environment. This study took advantage of a period of unprecedented levels of awareness about water security in order to investigate households’ willingness to pay (WTP) for reliable water supply and their WTP to avoid environmental damages in securing this supply. Increasing the supply of water from dams and groundwater will ultimately impact on aquatic ecosystems, but alternatives are more expensive. We surveyed 248 households from 105 suburbs and used contingent valuation methods to investigate WTP for both secure and less damaging or ‘greener’ ways of supplying water. Depending on income level, households were willing to pay 63–127% more for their normal levels of consumption in order to have security of supply, and a further 35–68% more to ensure its environmental sustainability. Based on the relationship between WTP for 7 income categories, the overall WTP for secure water supply under non-drought conditions amounted to some 2.8 billion ZAR/year, which is about 90% higher than pre-drought revenues. Aggregate WTP for securing this supply using options that ensured the protection of the region’s rivers and estuaries was 3.3 billion ZAR. These results have an important bearing on water investment and pricing decisions over the longer term.
{"title":"Cape Town residents’ willingness to pay for a secure and ‘green’ water supply","authors":"None JK Turpie, None GK Letley","doi":"10.17159/wsa/2023.v49.i4.4002","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.4002","url":null,"abstract":"The City of Cape Town experienced a serious drought between 2016 and 2018 which led to severe water shortages and concerns for the environment. This study took advantage of a period of unprecedented levels of awareness about water security in order to investigate households’ willingness to pay (WTP) for reliable water supply and their WTP to avoid environmental damages in securing this supply. Increasing the supply of water from dams and groundwater will ultimately impact on aquatic ecosystems, but alternatives are more expensive. We surveyed 248 households from 105 suburbs and used contingent valuation methods to investigate WTP for both secure and less damaging or ‘greener’ ways of supplying water. Depending on income level, households were willing to pay 63–127% more for their normal levels of consumption in order to have security of supply, and a further 35–68% more to ensure its environmental sustainability. Based on the relationship between WTP for 7 income categories, the overall WTP for secure water supply under non-drought conditions amounted to some 2.8 billion ZAR/year, which is about 90% higher than pre-drought revenues. Aggregate WTP for securing this supply using options that ensured the protection of the region’s rivers and estuaries was 3.3 billion ZAR. These results have an important bearing on water investment and pricing decisions over the longer term.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"120 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136312499","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 : 2023-10-27DOI: 10.17159/wsa/2023.v49.i4.4036
None Hilary Takawira, None Joshua Mbanga
Wastewater treatment plants (WWTPs) have been identified as point sources of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARG). Due to variations in antibiotic use and prescribing patterns in different countries, it is imperative to establish the presence of ARB and ARGs in water environments on a country-by-country basis. This study investigated the occurrence of 11 antibiotic-resistance genes (QNRB, DFR14, CTX-M, KPC, Sul1, QNRA, Sul2, ERMB, ERMA, SHV, NDM), and antibiotic-resistant Escherichia coli in a WWTP and its associated river water in Harare, Zimbabwe. 24 water samples were collected across 3 sites: upstream and downstream of the WWTP; final effluent of the WWTP. The samples were collected weekly for 8 weeks. Pure cultures of the E. coli isolates were obtained by membrane filtration (0.45 µm) and repeated streaking on Tryptone Bile X-glucuronide followed by biochemical tests (indole test; citrate test; motility, indole, and ornithine). Antibiotic resistance profiling was done for 12 antibiotics using the disc diffusion method. Total genomic DNA was extracted from the 21 water samples and the occurrence of 11 antibiotic-resistant genes investigated using conventional PCR. 86 E. coli isolates were obtained from the sampled sites: 28 from the upstream site, 26 from the WWTP effluent, and 32 from the downstream site. The results from chi-squared analysis showed a significant association (p < 0.05) between the sampling site and the percentage of antibiotic-resistant E. coli for all 12 antibiotics investigated. The percentage of E. coli isolates resistant to the tested antibiotics varied from 29% (ertapenem) to 80.2% (ciprofloxacin). 81 (94.2%) E. coli isolates were resistant to antibiotics from ≥3 classes. Eight (8/11, 72.7%) ARGs were detected in the WWTP effluent and river water samples. Results indicate that the investigated WWTP and associated river water are reservoirs of ARGs and antibiotic-resistant E. coli, which is a public health concern.
污水处理厂(WWTPs)已被确定为耐药细菌(ARB)和耐药基因(ARG)的点源。由于不同国家的抗生素使用和处方模式存在差异，必须在各国的基础上确定水环境中是否存在ARB和ARGs。本研究对津巴布韦哈拉雷某污水处理厂及其相关河水中11个耐药基因(QNRB、DFR14、CTX-M、KPC、Sul1、QNRA、Sul2、ERMB、ERMA、SHV、NDM)和耐药大肠杆菌的发生情况进行了调查。污水处理厂的最终排出物。每周采集样本，连续8周。通过膜过滤(0.45µm)获得大肠杆菌分离物的纯培养物，并在Tryptone Bile X-glucuronide上反复染色，然后进行生化试验(吲哚试验;柠檬酸测试;运动性、吲哚和鸟氨酸)。采用圆盘扩散法对12种抗生素进行耐药性分析。从21份水样中提取总基因组DNA，并采用常规PCR方法调查11个耐药基因的发生情况。从采样地点分离出86株大肠杆菌:28株来自上游地点，26株来自污水处理厂排放物，32株来自下游地点。卡方分析结果显示显著相关(p <对所有12种抗生素的耐药大肠杆菌百分比与采样点之间的差异为0.05)。大肠杆菌分离株对所测抗生素耐药的百分比从29%(厄他培南)到80.2%(环丙沙星)不等。81株(94.2%)大肠杆菌对≥3类抗生素耐药。污水处理厂出水和河流水样共检出8种ARGs(8/11, 72.7%)。结果表明，所调查的污水处理厂及其相关河水是ARGs和耐药大肠杆菌的宿主，是一个公共卫生问题。
{"title":"Occurrence of multidrug-resistant Escherichia coli and antibiotic resistance genes in a wastewater treatment plant and its associated river water in Harare, Zimbabwe","authors":"None Hilary Takawira, None Joshua Mbanga","doi":"10.17159/wsa/2023.v49.i4.4036","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.4036","url":null,"abstract":"Wastewater treatment plants (WWTPs) have been identified as point sources of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARG). Due to variations in antibiotic use and prescribing patterns in different countries, it is imperative to establish the presence of ARB and ARGs in water environments on a country-by-country basis. This study investigated the occurrence of 11 antibiotic-resistance genes (QNRB, DFR14, CTX-M, KPC, Sul1, QNRA, Sul2, ERMB, ERMA, SHV, NDM), and antibiotic-resistant Escherichia coli in a WWTP and its associated river water in Harare, Zimbabwe. 24 water samples were collected across 3 sites: upstream and downstream of the WWTP; final effluent of the WWTP. The samples were collected weekly for 8 weeks. Pure cultures of the E. coli isolates were obtained by membrane filtration (0.45 µm) and repeated streaking on Tryptone Bile X-glucuronide followed by biochemical tests (indole test; citrate test; motility, indole, and ornithine). Antibiotic resistance profiling was done for 12 antibiotics using the disc diffusion method. Total genomic DNA was extracted from the 21 water samples and the occurrence of 11 antibiotic-resistant genes investigated using conventional PCR. 86 E. coli isolates were obtained from the sampled sites: 28 from the upstream site, 26 from the WWTP effluent, and 32 from the downstream site. The results from chi-squared analysis showed a significant association (p < 0.05) between the sampling site and the percentage of antibiotic-resistant E. coli for all 12 antibiotics investigated. The percentage of E. coli isolates resistant to the tested antibiotics varied from 29% (ertapenem) to 80.2% (ciprofloxacin). 81 (94.2%) E. coli isolates were resistant to antibiotics from ≥3 classes. Eight (8/11, 72.7%) ARGs were detected in the WWTP effluent and river water samples. Results indicate that the investigated WWTP and associated river water are reservoirs of ARGs and antibiotic-resistant E. coli, which is a public health concern.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"24 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136311739","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 : 2023-10-27DOI: 10.17159/wsa/2023.v49.i4.3998
None Annelie Swanepoel, None Hein du Preez, None Henk Bouwman
Due to the worldwide increasing prevalence of microplastics in the aquatic environment, this study aimed to perform a screening of the source and drinking water of South Africa’s largest bulk drinking water supplier to determine the extent to which microplastics occur in the water. Source water samples, samples immediately after treatment, and samples in the distribution network (Johannesburg, Mabopane, Garankua and Pelindaba) were analysed. Microplastics concentrations in the source water ranged from 0.24 to 1.47 particles/L, immediately after treatment from 0.56 to 0.9 particles/L, and in the distribution network from 0.26 to 0.88 particles/L. Most of the microplastics found in the water were classified as ‘fragments’ and a few as ‘fibres’. The control sample (indicating contamination during sample preparation and analysis) showed 0.34 particles/L, which was higher than some of the samples taken, indicating very low microplastics concentrations in these samples. Little evidence was found that the drinking water treatment processes reduced the number of microplastics from the source to the final treated water. No evidence could be found that the pipes in the distribution network contribute to microplastics in the tap water. The most frequently found polymer in the samples was rubber. Based on mass, however, as a function of particle size and polymer density, ethylene-vinyl-acetate (a polymer commonly used as foam in sporting equipment and flip-flops) comprised 54% of the microplastics and polyethylene (standard and chlorinated) 25%.
{"title":"A baseline study on the prevalence of microplastics in South African drinking water: from source to distribution","authors":"None Annelie Swanepoel, None Hein du Preez, None Henk Bouwman","doi":"10.17159/wsa/2023.v49.i4.3998","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.3998","url":null,"abstract":"Due to the worldwide increasing prevalence of microplastics in the aquatic environment, this study aimed to perform a screening of the source and drinking water of South Africa’s largest bulk drinking water supplier to determine the extent to which microplastics occur in the water. Source water samples, samples immediately after treatment, and samples in the distribution network (Johannesburg, Mabopane, Garankua and Pelindaba) were analysed. Microplastics concentrations in the source water ranged from 0.24 to 1.47 particles/L, immediately after treatment from 0.56 to 0.9 particles/L, and in the distribution network from 0.26 to 0.88 particles/L. Most of the microplastics found in the water were classified as ‘fragments’ and a few as ‘fibres’. The control sample (indicating contamination during sample preparation and analysis) showed 0.34 particles/L, which was higher than some of the samples taken, indicating very low microplastics concentrations in these samples. Little evidence was found that the drinking water treatment processes reduced the number of microplastics from the source to the final treated water. No evidence could be found that the pipes in the distribution network contribute to microplastics in the tap water. The most frequently found polymer in the samples was rubber. Based on mass, however, as a function of particle size and polymer density, ethylene-vinyl-acetate (a polymer commonly used as foam in sporting equipment and flip-flops) comprised 54% of the microplastics and polyethylene (standard and chlorinated) 25%.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"126 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136311740","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}
Water availability in the root zone directly affects the yield and quality of tomatoes yet in most cases in sub-Saharan Africa water is either expensive or scarce. It is therefore important to establish and utilise suitable irrigation strategies in order to produce the crop in a sustainable way. In this study the effect of conventional and deficit irrigation treatments on yield, fruit quality and water use efficiency (WUE) were determined. Four trials were conducted at the University of Zimbabwe Farm from 2014-2017 with four treatments per trial: T1 = 100%, T2 = 80%, T3 = 60%, and T4 = 50% of crop water requirements (ETc). Treatments had equal number of plants per trial with an in-row plant spacing of 0.3 m and 0.5 m between adjacent rows. ETc was determined daily for each treatment and the corresponding volume applied through one drip emitter per plant. Fruits from each treatment were gathered while ripening and the total yield obtained. WUE was calculated by dividing the total fresh yield by total irrigation water applied. Maximum yield was obtained where 100% ETc was applied, with no significant difference between yield of plants at 80% and 60% ETc, except in 2016. Yield decreased with 50% ETc in 2014, 2015, and 2017 with no significant difference in yield between 60% and 50% ETc treatments in 2016. The 2015 season recorded the highest yield when compared to other trials showing that we can save 40% of water resulting in high WUE with minimum loss in yield. Deficit irrigation reduced fruit water but increased fruit soluble solids (°brix), vitamin C and fruit acid concentrations. Firmness was best when 60% ETc was applied. These results show that deficit irrigation is feasible for crop water management options for the production of high-quality field-grown tomatoes without major yield reductions.
{"title":"The effects of deficit irrigation on water use efficiency, yield and quality of drip-irrigated tomatoes grown under field conditions in Zimbabwe","authors":"None Godfrey Muroyiwa, None Emmanuel Mashonjowa, None Teddious Mhizha, None Maud Muchuweti","doi":"10.17159/wsa/2023.v49.i4.3935","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.3935","url":null,"abstract":"Water availability in the root zone directly affects the yield and quality of tomatoes yet in most cases in sub-Saharan Africa water is either expensive or scarce. It is therefore important to establish and utilise suitable irrigation strategies in order to produce the crop in a sustainable way. In this study the effect of conventional and deficit irrigation treatments on yield, fruit quality and water use efficiency (WUE) were determined. Four trials were conducted at the University of Zimbabwe Farm from 2014-2017 with four treatments per trial: T1 = 100%, T2 = 80%, T3 = 60%, and T4 = 50% of crop water requirements (ETc). Treatments had equal number of plants per trial with an in-row plant spacing of 0.3 m and 0.5 m between adjacent rows. ETc was determined daily for each treatment and the corresponding volume applied through one drip emitter per plant. Fruits from each treatment were gathered while ripening and the total yield obtained. WUE was calculated by dividing the total fresh yield by total irrigation water applied. Maximum yield was obtained where 100% ETc was applied, with no significant difference between yield of plants at 80% and 60% ETc, except in 2016. Yield decreased with 50% ETc in 2014, 2015, and 2017 with no significant difference in yield between 60% and 50% ETc treatments in 2016. The 2015 season recorded the highest yield when compared to other trials showing that we can save 40% of water resulting in high WUE with minimum loss in yield. Deficit irrigation reduced fruit water but increased fruit soluble solids (°brix), vitamin C and fruit acid concentrations. Firmness was best when 60% ETc was applied. These results show that deficit irrigation is feasible for crop water management options for the production of high-quality field-grown tomatoes without major yield reductions.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"84 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136317457","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 : 2023-10-27DOI: 10.17159/wsa/2023.v49.i4.4019
None Vernon Nagan, None Mohammed Seyam, None Taher Abunama
The Mgeni System is recognised as the main source of water supply for the Durban and Pietermaritzburg region in South Africa. This area is regarded as the primary economic hub of KwaZulu-Natal Province, and this brings about a high level of demographic pressure, with potential water supply problems in the future. This study investigates the water resource situation in the Mgeni System and evaluates future supply and demand accounting based on the (Water Evaluation and Planning) WEAP software. WEAP was used to analyse the study area for the period 2009–2050 to assess the impacts of various scenarios on future water supply shortfalls. Four scenarios were used, which take into account changing population growth rates and extended dry climates. The study found that the catchment is relatively sensitive to changes in population growth and extended dry climates, and this will alter the water availability significantly, causing a water supply deficit. In response to the projected future water demands, one technique to overcome the unmet demand is by introducing water conservation and demand management (WC/DM) strategies to reduce the water losses and shortfall encountered. By implementing adequate measures, water losses can be reduced, preventing water scarcity and giving decision makers time to provide further solutions to water supply problems.
Mgeni系统被认为是南非德班和彼得马里茨堡地区的主要供水来源。该地区被认为是夸祖鲁-纳塔尔省的主要经济中心，这带来了高度的人口压力，未来可能出现供水问题。本研究对Mgeni系统的水资源状况进行了调查，并基于(water Evaluation and Planning) WEAP软件对未来供需核算进行了评估。WEAP用于分析研究区在2009-2050年期间的情况，以评估不同情景对未来供水短缺的影响。考虑到人口增长率的变化和干旱气候的延长，研究人员使用了四种情景。该研究发现，该流域对人口增长和长期干旱气候的变化相对敏感，这将显著改变水的可用性，导致供水短缺。为了应对预计的未来水需求，克服未满足需求的一种技术是采用节水和需求管理(WC/DM)战略，以减少所遇到的水损失和短缺。通过实施适当的措施，可以减少水的损失，防止缺水，并使决策者有时间为供水问题提供进一步的解决办法。
{"title":"Assessment of long-term water demand for the Mgeni system using Water Evaluation and Planning (WEAP) model considering demographics and extended dry climate periods","authors":"None Vernon Nagan, None Mohammed Seyam, None Taher Abunama","doi":"10.17159/wsa/2023.v49.i4.4019","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.4019","url":null,"abstract":"The Mgeni System is recognised as the main source of water supply for the Durban and Pietermaritzburg region in South Africa. This area is regarded as the primary economic hub of KwaZulu-Natal Province, and this brings about a high level of demographic pressure, with potential water supply problems in the future. This study investigates the water resource situation in the Mgeni System and evaluates future supply and demand accounting based on the (Water Evaluation and Planning) WEAP software. WEAP was used to analyse the study area for the period 2009–2050 to assess the impacts of various scenarios on future water supply shortfalls. Four scenarios were used, which take into account changing population growth rates and extended dry climates. The study found that the catchment is relatively sensitive to changes in population growth and extended dry climates, and this will alter the water availability significantly, causing a water supply deficit. In response to the projected future water demands, one technique to overcome the unmet demand is by introducing water conservation and demand management (WC/DM) strategies to reduce the water losses and shortfall encountered. By implementing adequate measures, water losses can be reduced, preventing water scarcity and giving decision makers time to provide further solutions to water supply problems.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"219 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136317135","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 : 2023-10-27DOI: 10.17159/wsa/2023.v49.i4.4009
None Majid Khan, None M Faizan, None Mohamed A Antar, None Atia E Khalifa
An experimental investigation of a small-scale air-heated humidification–dehumidification (HDH) desalination system with bubble-column humidification and dehumidification units was conducted. The study addressed the performance of the multistage air-heated bubble-column HDH system, which has limited coverage in the literature, by operating two bubble-column humidifiers in series for the air humidification process with air reheating. The effect of operating parameters such as airflow rate, air temperature, and saline water levels in both humidifiers on the performance metrics of the system were investigated. The product distillate rate, energy consumption, gain output ratio (GOR), and specific energy consumption (SEC) are the main indicators of performance for the proposed desalination system. Response surface methodology (RSM) was applied to the current system using the design of experiment (DoE) for the prediction of variables that greatlyaffect productivity and energy input. The airflow rate, air temperature, and water level of the second humidifier have a favourable effect on the distillate rate and GOR of the system. In contrast, the effect of the water level inside the first humidifier is insignificant. Furthermore, the RSM optimization approach was used to obtain the optimum distillate productivity. An optimized distillate rate of 0.45 L/h and a GOR of 0.4 are achieved at 1.5 SCFM (standard cubic feet per minute) of airflow rate, and 6.5 cm of water level in the second humidifier with 140°C air inlet temperature. The numerical optimization reveals the optimal operating parameters, that correspond to maximum distillate production of 0.3 L/h with minimum input energy of 0.71 kW, to be 139°C air temperature, 1.13 SCFM of airflow rate, 6.5 cm and 3 cm water levels of second and first humidifier, respectively.
{"title":"Experimental study on optimum performance of two-stage air-heated bubble-column humidification–dehumidification system","authors":"None Majid Khan, None M Faizan, None Mohamed A Antar, None Atia E Khalifa","doi":"10.17159/wsa/2023.v49.i4.4009","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.4009","url":null,"abstract":"An experimental investigation of a small-scale air-heated humidification–dehumidification (HDH) desalination system with bubble-column humidification and dehumidification units was conducted. The study addressed the performance of the multistage air-heated bubble-column HDH system, which has limited coverage in the literature, by operating two bubble-column humidifiers in series for the air humidification process with air reheating. The effect of operating parameters such as airflow rate, air temperature, and saline water levels in both humidifiers on the performance metrics of the system were investigated. The product distillate rate, energy consumption, gain output ratio (GOR), and specific energy consumption (SEC) are the main indicators of performance for the proposed desalination system. Response surface methodology (RSM) was applied to the current system using the design of experiment (DoE) for the prediction of variables that greatlyaffect productivity and energy input. The airflow rate, air temperature, and water level of the second humidifier have a favourable effect on the distillate rate and GOR of the system. In contrast, the effect of the water level inside the first humidifier is insignificant. Furthermore, the RSM optimization approach was used to obtain the optimum distillate productivity. An optimized distillate rate of 0.45 L/h and a GOR of 0.4 are achieved at 1.5 SCFM (standard cubic feet per minute) of airflow rate, and 6.5 cm of water level in the second humidifier with 140°C air inlet temperature. The numerical optimization reveals the optimal operating parameters, that correspond to maximum distillate production of 0.3 L/h with minimum input energy of 0.71 kW, to be 139°C air temperature, 1.13 SCFM of airflow rate, 6.5 cm and 3 cm water levels of second and first humidifier, respectively.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136311738","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 : 2023-10-27DOI: 10.17159/wsa/2023.v49.i4.4032
None Yunhao Bai, None Tinglin Huang, None Pengcheng Yang
A shift in reservoir stratification and mixing significantly affects the water column ecosystem, which in turn leads to changes in phytoplankton abundance and community structure. To explore the effects of stratification and mixing on the phytoplankton community structure of a diversion reservoir, a 1-year survey was divided into a stratification period in 2020, a mixing period in 2020, and a stratification period in 2021, and redundancy analysis (RDA), variance partitioning analysis (VPA) and Pearson correlation analysis were used to analyse the key drivers affecting the phytoplankton functional groups, using Xikeng Reservoir as a case study. During the study period, 8 phyla, 69 genera and 9 major functional groups were observed in this reservoir. The dominant functional groups varied significantly, being X1 in the stratified period in 2020; P and D in the mixing period in 2020; and D, X1, and M in the stratified period in 2021. The phytoplankton diversity index was greater in the mixing period than in the stratification period, in agreement with the results of the aquatic ecological status evaluation (Q index, higher in the mixing period than in the stratification period). However, phytoplankton diversity of Xikeng Reservoir was of limited value in assessing the degree of water pollution, so should be considered in combination with the Q index. Water temperature (WT), mixing depth (Zmix), nitrogen–phosphorus ratio (N/P), and total nitrogen (TN) were important drivers of phytoplankton functional group dynamics in different periods. The study provides a valuable reference for assessing the relationship between environmental factors and phytoplankton communities, as well as for the evaluation and conservation of aquatic ecosystems in southern China's water diversion reservoirs.
{"title":"Effect of water stratification and mixing on phytoplankton functional groups: a case study of Xikeng Reservoir, China","authors":"None Yunhao Bai, None Tinglin Huang, None Pengcheng Yang","doi":"10.17159/wsa/2023.v49.i4.4032","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.4032","url":null,"abstract":"A shift in reservoir stratification and mixing significantly affects the water column ecosystem, which in turn leads to changes in phytoplankton abundance and community structure. To explore the effects of stratification and mixing on the phytoplankton community structure of a diversion reservoir, a 1-year survey was divided into a stratification period in 2020, a mixing period in 2020, and a stratification period in 2021, and redundancy analysis (RDA), variance partitioning analysis (VPA) and Pearson correlation analysis were used to analyse the key drivers affecting the phytoplankton functional groups, using Xikeng Reservoir as a case study. During the study period, 8 phyla, 69 genera and 9 major functional groups were observed in this reservoir. The dominant functional groups varied significantly, being X1 in the stratified period in 2020; P and D in the mixing period in 2020; and D, X1, and M in the stratified period in 2021. The phytoplankton diversity index was greater in the mixing period than in the stratification period, in agreement with the results of the aquatic ecological status evaluation (Q index, higher in the mixing period than in the stratification period). However, phytoplankton diversity of Xikeng Reservoir was of limited value in assessing the degree of water pollution, so should be considered in combination with the Q index. Water temperature (WT), mixing depth (Zmix), nitrogen–phosphorus ratio (N/P), and total nitrogen (TN) were important drivers of phytoplankton functional group dynamics in different periods. The study provides a valuable reference for assessing the relationship between environmental factors and phytoplankton communities, as well as for the evaluation and conservation of aquatic ecosystems in southern China's water diversion reservoirs.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"148 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136311741","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 : 2023-10-27DOI: 10.17159/wsa/2023.v49.i4.4029
None Bruna de Lemos Novo, None Fernanda Arruda Nogueira Gomes da Silva, None Luiz Carlos Bertolino, None Lidia Yokoyama
The present study aimed to propose a new cause of odorous compounds release, i.e., the presence of antibiotics in water bodies and its toxicity to cyanobacteria, known to be the main producer of geosmin (GEO) and 2-methylisoborneol (2-MIB). Therefore, a literature review was carried out regarding the problems caused by antibiotics in aquatic environment, including cyanobacterial blooms and GEO and 2-MIB release. In addition, a bibliometric analysis was performed using the VOSviewer software based on the results obtained from the Web of Science (WOS) database. This review aims to build a scientific understanding of the problem, presenting interesting points that converge with the proposed association. It is worth mentioning that no work has been found in the literature that has proposed this relationship. Thus, based on the bibliographic survey, observations and information acquired in recent years about cyanobacterial blooms and environmental contamination by pharmaceutical drugs, one of the main causes of an earthy and musty flavour and odour in a drinking water supply is the toxicity imposed by the presence of antibiotics in aquatic environments on cyanobacteria.
本研究旨在提出一种新的恶臭化合物释放的原因，即水体中抗生素的存在及其对蓝藻的毒性，蓝藻是土臭素(GEO)和2-甲基异冰片醇(2-MIB)的主要产生者。因此，我们对抗生素在水生环境中引起的问题，包括蓝藻华和GEO和2-MIB的释放进行了文献综述。此外，基于Web of Science (WOS)数据库的结果，使用VOSviewer软件进行文献计量学分析。这篇综述的目的是建立对这个问题的科学理解，提出与所提出的关联一致的有趣的观点。值得一提的是，在文献中没有发现提出这种关系的工作。因此，基于书目调查，观察和信息近年来获得的关于蓝藻华和环境污染的药物，在饮用水供应的泥土和发霉的味道和气味的主要原因之一是在水生环境中抗生素的存在对蓝藻施加的毒性。
{"title":"Antibiotics in water bodies, cyanobacterial toxicity and odorous compounds release: a review","authors":"None Bruna de Lemos Novo, None Fernanda Arruda Nogueira Gomes da Silva, None Luiz Carlos Bertolino, None Lidia Yokoyama","doi":"10.17159/wsa/2023.v49.i4.4029","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.4029","url":null,"abstract":"The present study aimed to propose a new cause of odorous compounds release, i.e., the presence of antibiotics in water bodies and its toxicity to cyanobacteria, known to be the main producer of geosmin (GEO) and 2-methylisoborneol (2-MIB). Therefore, a literature review was carried out regarding the problems caused by antibiotics in aquatic environment, including cyanobacterial blooms and GEO and 2-MIB release. In addition, a bibliometric analysis was performed using the VOSviewer software based on the results obtained from the Web of Science (WOS) database. This review aims to build a scientific understanding of the problem, presenting interesting points that converge with the proposed association. It is worth mentioning that no work has been found in the literature that has proposed this relationship. Thus, based on the bibliographic survey, observations and information acquired in recent years about cyanobacterial blooms and environmental contamination by pharmaceutical drugs, one of the main causes of an earthy and musty flavour and odour in a drinking water supply is the toxicity imposed by the presence of antibiotics in aquatic environments on cyanobacteria.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"218 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136317501","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 : 2023-10-27DOI: 10.17159/wsa/2023.v49.i4.4031
None Moline Chauruka, None Annelieke Duker, None Pooja Prasad, None Pieter Van der Zaag
In Zimbabwe, farmer-led irrigation is far more widespread than planners and policy makers realise. Along the Shashani sand river, in the arid to semi-arid lands of south-western Zimbabwe, diverse farmer-initiated irrigation ventures exist. This qualitative case study focuses on bucket irrigation, in which very small vegetable fields of up to 450 m2 are fenced by tree branches, and irrigated with water from scoop holes in sandy river beds. Farmers initiate and operate their fields with no external assistance. This study presents the benefits of bucket irrigation as an often-overlooked form of farmer-led irrigation development. Through this qualitative and strongly observational study, 26 bucket irrigation farmers and 4 non-irrigators were interviewed using semi-structured interviews where farmers’ perceptions and experiences were captured. We investigate what drives and sustains bucket irrigation, its significance to rural livelihoods under harsh economic and climatic conditions, and the barriers towards scaling this type of farmer-led irrigation development. The results show that drivers for bucket irrigation stem from economic hardship and are gendered. Women are motivated to irrigate mainly by the need to produce vegetables for household consumption, whereas men pursue irrigation due to a lack of employment. Bucket irrigators experience enhanced food security, and have more secure income, contributing to improved wellbeing. Furthermore, despite the desire to scale, the farm size is mainly constrained by fencing and energy for transporting water, which is a result of a persistent lack of financial capital to invest in irrigation technologies. We conclude that bucket irrigation acts as an important livelihood strategy, and that it significantly enhances farmers’ resilience to economic and climatic shocks. Bucket irrigation should not be overlooked in policies that advocate scaling of irrigation. Bucket irrigators have the potential to expand and benefit significantly if supported with innovative financial mechanisms that enable investments in the required technology and knowledge.
{"title":"Endogenous irrigation in arid Zimbabwe: farmer perceptions of livelihood benefits and barriers to scaling","authors":"None Moline Chauruka, None Annelieke Duker, None Pooja Prasad, None Pieter Van der Zaag","doi":"10.17159/wsa/2023.v49.i4.4031","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.4031","url":null,"abstract":"In Zimbabwe, farmer-led irrigation is far more widespread than planners and policy makers realise. Along the Shashani sand river, in the arid to semi-arid lands of south-western Zimbabwe, diverse farmer-initiated irrigation ventures exist. This qualitative case study focuses on bucket irrigation, in which very small vegetable fields of up to 450 m2 are fenced by tree branches, and irrigated with water from scoop holes in sandy river beds. Farmers initiate and operate their fields with no external assistance. This study presents the benefits of bucket irrigation as an often-overlooked form of farmer-led irrigation development. Through this qualitative and strongly observational study, 26 bucket irrigation farmers and 4 non-irrigators were interviewed using semi-structured interviews where farmers’ perceptions and experiences were captured. We investigate what drives and sustains bucket irrigation, its significance to rural livelihoods under harsh economic and climatic conditions, and the barriers towards scaling this type of farmer-led irrigation development. The results show that drivers for bucket irrigation stem from economic hardship and are gendered. Women are motivated to irrigate mainly by the need to produce vegetables for household consumption, whereas men pursue irrigation due to a lack of employment. Bucket irrigators experience enhanced food security, and have more secure income, contributing to improved wellbeing. Furthermore, despite the desire to scale, the farm size is mainly constrained by fencing and energy for transporting water, which is a result of a persistent lack of financial capital to invest in irrigation technologies. We conclude that bucket irrigation acts as an important livelihood strategy, and that it significantly enhances farmers’ resilience to economic and climatic shocks. Bucket irrigation should not be overlooked in policies that advocate scaling of irrigation. Bucket irrigators have the potential to expand and benefit significantly if supported with innovative financial mechanisms that enable investments in the required technology and knowledge.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"5 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136312498","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 : 2023-10-27DOI: 10.17159/wsa/2023.v49.i4.4027
None Wallyson Ribeiro dos Santos, None Priscila Pereira, None Lucrécio Fábio dos Santos, None Geronimo Virginio Tagliaferro, None Daniela HP Guimarães
The use of microalgae cultures to process effluents from industries, leachates, and tanneries, among others, quantified by the reduction of metallic materials in the medium and the reduction of chemical oxygen demand (COD), helps reduce the environmental impact caused by human development. In addition, with the growth of the culture, it is possible to produce a significant amount of chlorophyll, a carotenoid of high value in the cosmetics and food industries that are used as a natural pigment. In this context, this work presents a study conducted to verify the bioremediation and chlorophyll production potential of the cultivation of the microalgae Chlorella minutíssima, using the Taguchi method. The microalgae Chlorella minutissima has given good results in the bioremediation of leachate, as a mean reduction of 33% in COD was obtained, as well as a 92% reduction in the toxic components. In addition, statistical analysis revealed that the four process factors were significant factors for chlorophyll a, chlorophyll b and carotenoid productivity (p < 0.05). Finally, it was observed that the maximum chlorophyll a (111.9 ± 0.8 mg‧L−1‧d−1), chlorophyll b (66.1 ± 1.7 mg‧L−1‧d−1), and carotenoid (31.9 ± 0.03 mg‧L−1‧d−1) values obtained occurred in Experiment 8, which is closer to the ideal conditions identified by statistical analysis, revealing the effectiveness of the use of the Taguchi method for the design of experiments.
{"title":"Effects of leachate concentration, carbon dioxide and aeration flow rate on chlorophyll and carotenoid productivity and bioremediation potential of the microalga Chlorella minutissima","authors":"None Wallyson Ribeiro dos Santos, None Priscila Pereira, None Lucrécio Fábio dos Santos, None Geronimo Virginio Tagliaferro, None Daniela HP Guimarães","doi":"10.17159/wsa/2023.v49.i4.4027","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i4.4027","url":null,"abstract":"The use of microalgae cultures to process effluents from industries, leachates, and tanneries, among others, quantified by the reduction of metallic materials in the medium and the reduction of chemical oxygen demand (COD), helps reduce the environmental impact caused by human development. In addition, with the growth of the culture, it is possible to produce a significant amount of chlorophyll, a carotenoid of high value in the cosmetics and food industries that are used as a natural pigment. In this context, this work presents a study conducted to verify the bioremediation and chlorophyll production potential of the cultivation of the microalgae Chlorella minutíssima, using the Taguchi method. The microalgae Chlorella minutissima has given good results in the bioremediation of leachate, as a mean reduction of 33% in COD was obtained, as well as a 92% reduction in the toxic components. In addition, statistical analysis revealed that the four process factors were significant factors for chlorophyll a, chlorophyll b and carotenoid productivity (p < 0.05). Finally, it was observed that the maximum chlorophyll a (111.9 ± 0.8 mg‧L−1‧d−1), chlorophyll b (66.1 ± 1.7 mg‧L−1‧d−1), and carotenoid (31.9 ± 0.03 mg‧L−1‧d−1) values obtained occurred in Experiment 8, which is closer to the ideal conditions identified by statistical analysis, revealing the effectiveness of the use of the Taguchi method for the design of experiments.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136311737","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}
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