Pub Date : 2023-01-31DOI: 10.17159/wsa/2023.v49.i1.3985
Preyan Arumugam, Lungiswa Zuma, Susan Mercer, Lloyd Govender, Jonathan Pocock, Christopher J Brouckaert, Teddy Gounden
The design principles of decentralised wastewater treatment systems (DEWATS) make them a practical sanitation option for municipalities to adopt in fast-growing cities in South Africa. Since 2014, a demonstration-scale DEWATS with a modular design consisting of a settler, anaerobic baffled reactor (ABR), anaerobic filter (AF), vertical down-flow constructed wetland (VFCW) and horizontal flow constructed wetland (HFCW) has been in operation in eThekwini. A performance evaluation after the long-term operation was undertaken in 2019 by comparing the final effluent with national regulatory requirements. Despite limitations in characterising the raw wastewater, a comparison of the settler and final effluent quality indicated high (≥ 85%) removal efficiencies of total chemical oxygen demand (CODt), ammonium-N (NH4-N) and orthophosphate-P (PO4-P), 75% removal of total suspended solids (TSS) and 83.3% log10 removal of Escherichia coli. Lack of exogenous and endogenous carbon and high dissolved oxygen (DO) concentrations (> 0.5 mg‧L−1) inhibited denitrification in the HFCW, resulting in 12.5% of the effluent samples achieving compliance for nitrate-N (NO3-N). Moreover, mixed aggregate media and low residence times in the HFCW may have also contributed to poor NO3-N removal. During the COVID-19 lockdown, an unexpected shutdown and subsequent resumption of flow to the DEWATS indicated a 16-week recovery time based on achieving full nitrification in the HFCW. Although design modifications are necessary for the HFCW, the installation of urine diversion flushing toilets at the household will reduce the nutrient loading to the DEWATS and potentially achieve fully compliant effluent. Alternatively, the application of two-stage vertical flow constructed wetlands to improve denitrification should also be explored in the South African context. With an improved design, DEWATS has the potential to fill the gap in both urban and rural sanitation in South Africa, where waterborne sanitation is still desired but connections to conventional wastewater treatment works (WWTWs) are not possible.
分散式污水处理系统(DEWATS)的设计原则使其成为南非市政当局在快速发展的城市中采用的实用卫生选择。自2014年以来，由沉降器、厌氧折流板反应器(ABR)、厌氧过滤器(AF)、垂直下流人工湿地(VFCW)和水平流人工湿地(HFCW)组成的模块化设计的DEWATS示范规模已在埃德克尼省投入运行。2019年，通过将最终出水与国家监管要求进行比较，对长期运行后的性能进行了评估。尽管在原水表征方面存在局限性，但对沉淀池和最终出水水质的比较表明，总化学需氧量(CODt)、氨氮(NH4-N)和正磷酸盐(PO4-P)的去除率很高(≥85%)，总悬浮固体(TSS)去除率为75%，大肠杆菌去除率为83.3% log10。缺乏外源和内源碳以及高溶解氧(DO)浓度(> 0.5 mg·L−1)抑制了HFCW中的反硝化作用，导致12.5%的出水样品达到硝酸盐- n (NO3-N)的要求。此外，混合的骨料和较短的停留时间也可能导致NO3-N的去除效果较差。在COVID-19封锁期间，意外关闭和随后恢复到DEWATS的流量表明，在HFCW中实现完全硝化的基础上，需要16周的恢复时间。虽然污水处理厂的设计需要修改，但在家庭中安装尿液分流冲洗厕所将减少污水处理系统的营养负荷，并有可能达到完全合规的排放。另外，还应在南非的背景下探索应用两级垂直流人工湿地来改善反硝化。通过改进设计，DEWATS有可能填补南非城市和农村卫生设施的空白，在南非，人们仍然需要水基卫生设施，但无法与传统的污水处理厂(WWTWs)连接。
{"title":"The potential of decentralised wastewater treatment in urban and rural sanitation in South Africa: lessons learnt from a demonstration-scale DEWATS within the eThekwini Municipality","authors":"Preyan Arumugam, Lungiswa Zuma, Susan Mercer, Lloyd Govender, Jonathan Pocock, Christopher J Brouckaert, Teddy Gounden","doi":"10.17159/wsa/2023.v49.i1.3985","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i1.3985","url":null,"abstract":"The design principles of decentralised wastewater treatment systems (DEWATS) make them a practical sanitation option for municipalities to adopt in fast-growing cities in South Africa. Since 2014, a demonstration-scale DEWATS with a modular design consisting of a settler, anaerobic baffled reactor (ABR), anaerobic filter (AF), vertical down-flow constructed wetland (VFCW) and horizontal flow constructed wetland (HFCW) has been in operation in eThekwini. A performance evaluation after the long-term operation was undertaken in 2019 by comparing the final effluent with national regulatory requirements. Despite limitations in characterising the raw wastewater, a comparison of the settler and final effluent quality indicated high (≥ 85%) removal efficiencies of total chemical oxygen demand (CODt), ammonium-N (NH4-N) and orthophosphate-P (PO4-P), 75% removal of total suspended solids (TSS) and 83.3% log10 removal of Escherichia coli. Lack of exogenous and endogenous carbon and high dissolved oxygen (DO) concentrations (> 0.5 mg‧L−1) inhibited denitrification in the HFCW, resulting in 12.5% of the effluent samples achieving compliance for nitrate-N (NO3-N). Moreover, mixed aggregate media and low residence times in the HFCW may have also contributed to poor NO3-N removal. During the COVID-19 lockdown, an unexpected shutdown and subsequent resumption of flow to the DEWATS indicated a 16-week recovery time based on achieving full nitrification in the HFCW. Although design modifications are necessary for the HFCW, the installation of urine diversion flushing toilets at the household will reduce the nutrient loading to the DEWATS and potentially achieve fully compliant effluent. Alternatively, the application of two-stage vertical flow constructed wetlands to improve denitrification should also be explored in the South African context. With an improved design, DEWATS has the potential to fill the gap in both urban and rural sanitation in South Africa, where waterborne sanitation is still desired but connections to conventional wastewater treatment works (WWTWs) are not possible.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82229798","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 : 2023-01-31DOI: 10.17159/wsa/2023.v49.i1.3988
MS Mahlare, MN Lewu, FB Lewu, C Bester
Cyclopia, generally known as honeybush, and belonging to the Fabaceae family, originates from the Cape Floristic Region of the Eastern Cape and Western Cape provinces of South Africa. Currently, 6 honeybush species are commercially cultivated but, to date, there have been limited trials attempting to study their agronomic water demand. A pot trial was conducted where Cyclopia subternata plants were cultivated on different soil types (Stellenbosch granite, Stellenbosch shale and Stellenbosch clovelly) and subjected to three different water-deficit stress levels (well-watered, semi-stressed and stressed). Remarkably, irrigation treatments and soil types did not significantly affect the growth of the plants. However, the well-watered treatment consistently had higher yields compared to the other two treatments. The water-stressed (semi-stressed and stressed) treatments had lower relative water contents (RWC) with higher concentrations of proline, which signify water stress, compared to the control treatment. Higher proline and lower RWC contents found in this study are indications of water stress.
{"title":"Cyclopia subternata growth, yield, proline and relative water content in response to water deficit stress","authors":"MS Mahlare, MN Lewu, FB Lewu, C Bester","doi":"10.17159/wsa/2023.v49.i1.3988","DOIUrl":"https://doi.org/10.17159/wsa/2023.v49.i1.3988","url":null,"abstract":"Cyclopia, generally known as honeybush, and belonging to the Fabaceae family, originates from the Cape Floristic Region of the Eastern Cape and Western Cape provinces of South Africa. Currently, 6 honeybush species are commercially cultivated but, to date, there have been limited trials attempting to study their agronomic water demand. A pot trial was conducted where Cyclopia subternata plants were cultivated on different soil types (Stellenbosch granite, Stellenbosch shale and Stellenbosch clovelly) and subjected to three different water-deficit stress levels (well-watered, semi-stressed and stressed). Remarkably, irrigation treatments and soil types did not significantly affect the growth of the plants. However, the well-watered treatment consistently had higher yields compared to the other two treatments. The water-stressed (semi-stressed and stressed) treatments had lower relative water contents (RWC) with higher concentrations of proline, which signify water stress, compared to the control treatment. Higher proline and lower RWC contents found in this study are indications of water stress.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2023-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79172015","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 : 2022-10-26DOI: 10.17159/wsa/2022.v48.i4.3920
Oliver Masimba, W. Gumindoga, A. Mhizha, D. Rwasoka
This study focused on the Upper Manyame sub-catchment which covers an area of approximately 3 786 km2 and forms part of the Manyame catchment, one of the seven catchments of Zimbabwe. Manyame catchment has its source in Marondera town and drains into the Zambezi River downstream of the Kariba Dam and upstream of the Cahora Bassa Dam, in the northern part of the country. This study assessed potential climate change impacts on the streamflow and reservoir inflows in the Upper Manyame sub-catchment. Hydrologic simulations for future climate (2030s and 2060s) were carried out using statistically downscaled bias-corrected variables from the HadCM3 (HadCM3A2a and HadCM3B2a scenarios) and CanESM2 (RCP2.6 and RCP8.5) global circulation models. The HEC–HMS hydrological model was set up for two gauged micro-catchments and eight ungauged tributary micro-catchments. Model calibration for gauged micro-catchments of Upper Manyame over the period from 2000–2010 revealed satisfactory model performance of 4.3% (RVE) and 0.1 (bias) for Mukuvisi micro-catchment and 9.5% (RVE) and 0.15 (bias) for Marimba micro-catchment. Model simulations resulted in a projected decrease in streamflow by 7.4–26.4% for HadCM3. For CanESM2, simulations resulted in a projected decrease in streamflow by 2.5–34.7%. Reservoir inflows into Lake Chivero and Lake Manyame, the main water supply sources for Harare, will decrease by 10.5–18% for HadCM3 and by 8–33.6% for CanESM2.
{"title":"Impacts of climate change on streamflow and reservoir inflows in the Upper Manyame sub-catchment of Zimbabwe","authors":"Oliver Masimba, W. Gumindoga, A. Mhizha, D. Rwasoka","doi":"10.17159/wsa/2022.v48.i4.3920","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i4.3920","url":null,"abstract":"This study focused on the Upper Manyame sub-catchment which covers an area of approximately 3 786 km2 and forms part of the Manyame catchment, one of the seven catchments of Zimbabwe. Manyame catchment has its source in Marondera town and drains into the Zambezi River downstream of the Kariba Dam and upstream of the Cahora Bassa Dam, in the northern part of the country. This study assessed potential climate change impacts on the streamflow and reservoir inflows in the Upper Manyame sub-catchment. Hydrologic simulations for future climate (2030s and 2060s) were carried out using statistically downscaled bias-corrected variables from the HadCM3 (HadCM3A2a and HadCM3B2a scenarios) and CanESM2 (RCP2.6 and RCP8.5) global circulation models. The HEC–HMS hydrological model was set up for two gauged micro-catchments and eight ungauged tributary micro-catchments. Model calibration for gauged micro-catchments of Upper Manyame over the period from 2000–2010 revealed satisfactory model performance of 4.3% (RVE) and 0.1 (bias) for Mukuvisi micro-catchment and 9.5% (RVE) and 0.15 (bias) for Marimba micro-catchment. Model simulations resulted in a projected decrease in streamflow by 7.4–26.4% for HadCM3. For CanESM2, simulations resulted in a projected decrease in streamflow by 2.5–34.7%. Reservoir inflows into Lake Chivero and Lake Manyame, the main water supply sources for Harare, will decrease by 10.5–18% for HadCM3 and by 8–33.6% for CanESM2. \u0000 ","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73195762","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 : 2022-10-26DOI: 10.17159/wsa/2022.v48.i4.3955
Takalani Makhani, Olawumi O Sadare, Stephan Wagenaar, Kapil Moothi, Richard M Moutloali, Michael O Daramola
Oil exploration generates produced water that is characterized as hazardous and toxic waste. Produced water contains a mixture of various pollutants, including monoaromatic hydrocarbons BTEX (benzene, toluene, ethylbenzene, and xylene), compounds that are carcinogenic even in small concentrations. In this study, tannin iron complex (TA-FeIII), blended into polyethersulfone (PES) membrane was evaluated for the treatment of BTEX-containing wastewater. The membranes were fabricated using the non-solvent induced phase separation (NIPS) method and loading of the TA-FeIII complex on the membranes varied from 0–0.9 wt%. The fabricated membranes were characterized using various techniques such as scanning electron microscopy (SEM), water contact angle (WCA), Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM) to check the surface morphology, hydrophilicity, surface functionality and surface roughness of the fabricated membranes, respectively. The TA-FeIII modified membranes showed increased pure water flux from 100 (PES 0) to ∼150 (PES 0.9) L/(m2‧h) at 100 kPa. The performance of the fabricated membranes was tested using 70 mg/L synthetic BTEX solution. Overall BTEX rejection > 70% was achieved at increasing TA-FeIII loadings compared to BTEX rejection < 65% for the pure PES membrane. Rejection of the BTEX compounds was mainly through the size exclusion mechanism. These modified TA-FeIII/PES UF membranes proved to be effective in the treatment of BTEX-containing water, and also have the potential to be applied in oily wastewater treatment.
{"title":"Fabrication and performance evaluation of tannin iron complex (TA-FeIII/PES) UF membrane in treatment of BTEX wastewater","authors":"Takalani Makhani, Olawumi O Sadare, Stephan Wagenaar, Kapil Moothi, Richard M Moutloali, Michael O Daramola","doi":"10.17159/wsa/2022.v48.i4.3955","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i4.3955","url":null,"abstract":"Oil exploration generates produced water that is characterized as hazardous and toxic waste. Produced water contains a mixture of various pollutants, including monoaromatic hydrocarbons BTEX (benzene, toluene, ethylbenzene, and xylene), compounds that are carcinogenic even in small concentrations. In this study, tannin iron complex (TA-FeIII), blended into polyethersulfone (PES) membrane was evaluated for the treatment of BTEX-containing wastewater. The membranes were fabricated using the non-solvent induced phase separation (NIPS) method and loading of the TA-FeIII complex on the membranes varied from 0–0.9 wt%. The fabricated membranes were characterized using various techniques such as scanning electron microscopy (SEM), water contact angle (WCA), Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM) to check the surface morphology, hydrophilicity, surface functionality and surface roughness of the fabricated membranes, respectively. The TA-FeIII modified membranes showed increased pure water flux from 100 (PES 0) to ∼150 (PES 0.9) L/(m2‧h) at 100 kPa. The performance of the fabricated membranes was tested using 70 mg/L synthetic BTEX solution. Overall BTEX rejection > 70% was achieved at increasing TA-FeIII loadings compared to BTEX rejection < 65% for the pure PES membrane. Rejection of the BTEX compounds was mainly through the size exclusion mechanism. These modified TA-FeIII/PES UF membranes proved to be effective in the treatment of BTEX-containing water, and also have the potential to be applied in oily wastewater treatment. ","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86868912","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 : 2022-10-26DOI: 10.17159/wsa/2022.v48.i4.3941
F. Tshabuse, N. Buthelezi, AM Folami, L. Donnelly, FM Swalaha
Sewage treatment facilities aim to reduce biological contaminants such as pathogenic bacteria, fungi, protozoa, and viruses in wastewaters before discharging them to the receiving water bodies. However, several studies have shown the persistence of these contaminants throughout the sewage treatment process. In this study, the Vitek 2 compact system was used to detect the presence of Escherichia coli in three sewage treatment facilities located in the Pietermaritzburg urban area (South Africa), and its susceptibility to antimicrobial agents. E. coli has been recognized as an important Gram-negative rod-shaped human pathogen. The effluent and influent samples were analysed to determine the fate of E. coli and its susceptibility to 17 antimicrobial agents. The system identified the presence of drug-resistant E. coli in all of the tested samples, with the highest susceptibility being to ampicillin (33%) and trimethoprim/sulfamethoxazole (27%). The Vitek 2 compact system is a quick and powerful tool to identify antimicrobial-resistant bacteria in effluents and monitoring by this systemcan be used to prevent the outbreak of waterborne diseases.
{"title":"Rapid detection of drug-resistant Escherichia coli by Vitek 2 compact system","authors":"F. Tshabuse, N. Buthelezi, AM Folami, L. Donnelly, FM Swalaha","doi":"10.17159/wsa/2022.v48.i4.3941","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i4.3941","url":null,"abstract":"Sewage treatment facilities aim to reduce biological contaminants such as pathogenic bacteria, fungi, protozoa, and viruses in wastewaters before discharging them to the receiving water bodies. However, several studies have shown the persistence of these contaminants throughout the sewage treatment process. In this study, the Vitek 2 compact system was used to detect the presence of Escherichia coli in three sewage treatment facilities located in the Pietermaritzburg urban area (South Africa), and its susceptibility to antimicrobial agents. E. coli has been recognized as an important Gram-negative rod-shaped human pathogen. The effluent and influent samples were analysed to determine the fate of E. coli and its susceptibility to 17 antimicrobial agents. The system identified the presence of drug-resistant E. coli in all of the tested samples, with the highest susceptibility being to ampicillin (33%) and trimethoprim/sulfamethoxazole (27%). The Vitek 2 compact system is a quick and powerful tool to identify antimicrobial-resistant bacteria in effluents and monitoring by this systemcan be used to prevent the outbreak of waterborne diseases.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79743899","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 : 2022-10-26DOI: 10.17159/wsa/2022.v48.i4.3852
C. Ruiters, Joe Amadi-Echendu
South Africa has a serious backlog in investment for the development and management of water infrastructure. This study aimed to assess the investment measures, needs and priorities for water infrastructure (engineering realities) through the following objectives: (i) the measurement of water infrastructure investments which demonstrate the budgets required; (ii) understanding the current water infrastructure investment needs and priorities, including benefits and limitations; and (iii) the principles and characteristics for alternative and/or innovative measures, sources and/or models for water infrastructure investments and the envisaged effects. The range innovative of investment models for water infrastructure needs in South Africa are wide, i.e., 15 models were identified depending on the project type and overall transaction costs. The existing public provision model continues to characterise much of the water infrastructure investment in South Africa. The research determined investments in strategic water infrastructure systems over more than 20 years (1998/99–2019/20). The correlations between the three investment measures (as share of GDP) were generally negative and not significant, except for between GFCF(GG) + PPI and GFCFCE) + PPI, which was highly significant. Total water infrastructure investments constituted only 0.35–0.74% of GDP for the last ca. 20 years and 3.97–14.35% of total infrastructure investments. The results identified under-investment estimated at 54.023 billion ZAR for the medium-term expenditure framework (MTEF) period of 3 years.
{"title":"Investment models for the water infrastructure value chain in South Africa: investment measures, needs and priorities","authors":"C. Ruiters, Joe Amadi-Echendu","doi":"10.17159/wsa/2022.v48.i4.3852","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i4.3852","url":null,"abstract":"South Africa has a serious backlog in investment for the development and management of water infrastructure. This study aimed to assess the investment measures, needs and priorities for water infrastructure (engineering realities) through the following objectives: (i) the measurement of water infrastructure investments which demonstrate the budgets required; (ii) understanding the current water infrastructure investment needs and priorities, including benefits and limitations; and (iii) the principles and characteristics for alternative and/or innovative measures, sources and/or models for water infrastructure investments and the envisaged effects. The range innovative of investment models for water infrastructure needs in South Africa are wide, i.e., 15 models were identified depending on the project type and overall transaction costs. The existing public provision model continues to characterise much of the water infrastructure investment in South Africa. The research determined investments in strategic water infrastructure systems over more than 20 years (1998/99–2019/20). The correlations between the three investment measures (as share of GDP) were generally negative and not significant, except for between GFCF(GG) + PPI and GFCFCE) + PPI, which was highly significant. Total water infrastructure investments constituted only 0.35–0.74% of GDP for the last ca. 20 years and 3.97–14.35% of total infrastructure investments. The results identified under-investment estimated at 54.023 billion ZAR for the medium-term expenditure framework (MTEF) period of 3 years.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81175613","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 : 2022-10-26DOI: 10.17159/wsa/2022.v48.i4.3971
C. O. Ataguba, Isobel Brink
Langmuir and Freundlich isotherm adsorption models were used to predict iron and lead removal from automobile workshop stormwater runoff. Combined low-cost filter systems consisting of granular activated carbon–rice husk (GAC–RH) and river gravel–granular activated carbon (GR–GAC) were used in this study. The effects of adsorbent dosage and contact time on the adsorption capacity of the adsorbents, as well as the removal efficiencies of the adsorbent systems, were also investigated. The results for the Langmuir model generally showed favourable adsorption processes., with all RL values < 1 (in the range 0.358–0.518). The Langmuir model gave better predictions for iron and lead removal, with high R2 values (in the range 0.842–0.969), while the root mean square error (RMSE) values ranged from 0.002 to 2.366. The Freundlich model parameters indicated chemisorption processes with all n values < 1 (in the range 0.1296–0.4675). R2 values were in the range of 0.634–0.916 while RMSE values ranged from 0.002 to 0.1765. Additionally, the removal efficiencies for iron and lead using GAC–RH filter system (54% and 48%, respectively) were found to be higher than those obtained using GR–GAC filter system (35% and 25%, respectively). The adsorption capacities of the adsorbents decreased with increased dosages of the adsorbent, with optimum adsorbent dosage of 0.5 g and equilibrium contact time of 80 min for the combined filter adsorbents. Further research towards modifying adsorbents for removal of oil and grease from polluted automobile workshop stormwater runoff are warranted.
{"title":"Application of isotherm models to combined filter systems for the prediction of iron and lead removal from automobile workshop stormwater runoff","authors":"C. O. Ataguba, Isobel Brink","doi":"10.17159/wsa/2022.v48.i4.3971","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i4.3971","url":null,"abstract":"Langmuir and Freundlich isotherm adsorption models were used to predict iron and lead removal from automobile workshop stormwater runoff. Combined low-cost filter systems consisting of granular activated carbon–rice husk (GAC–RH) and river gravel–granular activated carbon (GR–GAC) were used in this study. The effects of adsorbent dosage and contact time on the adsorption capacity of the adsorbents, as well as the removal efficiencies of the adsorbent systems, were also investigated. The results for the Langmuir model generally showed favourable adsorption processes., with all RL values < 1 (in the range 0.358–0.518). The Langmuir model gave better predictions for iron and lead removal, with high R2 values (in the range 0.842–0.969), while the root mean square error (RMSE) values ranged from 0.002 to 2.366. The Freundlich model parameters indicated chemisorption processes with all n values < 1 (in the range 0.1296–0.4675). R2 values were in the range of 0.634–0.916 while RMSE values ranged from 0.002 to 0.1765. Additionally, the removal efficiencies for iron and lead using GAC–RH filter system (54% and 48%, respectively) were found to be higher than those obtained using GR–GAC filter system (35% and 25%, respectively). The adsorption capacities of the adsorbents decreased with increased dosages of the adsorbent, with optimum adsorbent dosage of 0.5 g and equilibrium contact time of 80 min for the combined filter adsorbents. Further research towards modifying adsorbents for removal of oil and grease from polluted automobile workshop stormwater runoff are warranted.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84914815","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 : 2022-10-26DOI: 10.17159/wsa/2022.v48.i4.3960
SM Marr, DCH Retief, JR Sara, WJ Luus-Powell
Historical data (July 1998 – June 2018) for the middle Olifants River, Limpopo River system, were compiled to evaluate the dynamics of selected water physico-chemical parameters with river discharge. The concentration of most water quality parameters increased over time. However, these concentrations are rapidly decreased, or reset, by the rapid filling, or spilling, of Loskop and/or Flag Boshielo Dams during a high-flow event. The flow-duration curves for stations below impoundments in the middle catchment on the Olifants River are typical of highly regulated rivers, although releases from Flag Boshielo Dam were more consistent through the 20 years. No outflow from Loskop Dam was recorded for 5.4% of the 20 years. The load-duration curves for gauging weirs on the Olifants and Elands rivers immediately upstream of Flag Boshielo Dam showed that the ‘tolerable’ concentrations were exceeded for total dissolved solids at the 60th and 20th percentiles of the flow, respectively. In addition, records for electrical conductivity, sodium, chloride, and alkalinity frequently exceeded the ‘tolerable’ concentrations at these sites. The results for Loskop and Flag Boshielo dams are generally lower than the tolerable concentrations for the parameters evaluated. Management of the flow regulation of the Olifants River should be aimed at meeting the water quality stipulations for all users in the agricultural, domestic, industrial, and recreational sectors.
{"title":"Flow patterns and chemical loads in the middle Olifants River, Limpopo River System, South Africa","authors":"SM Marr, DCH Retief, JR Sara, WJ Luus-Powell","doi":"10.17159/wsa/2022.v48.i4.3960","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i4.3960","url":null,"abstract":"Historical data (July 1998 – June 2018) for the middle Olifants River, Limpopo River system, were compiled to evaluate the dynamics of selected water physico-chemical parameters with river discharge. The concentration of most water quality parameters increased over time. However, these concentrations are rapidly decreased, or reset, by the rapid filling, or spilling, of Loskop and/or Flag Boshielo Dams during a high-flow event. The flow-duration curves for stations below impoundments in the middle catchment on the Olifants River are typical of highly regulated rivers, although releases from Flag Boshielo Dam were more consistent through the 20 years. No outflow from Loskop Dam was recorded for 5.4% of the 20 years. The load-duration curves for gauging weirs on the Olifants and Elands rivers immediately upstream of Flag Boshielo Dam showed that the ‘tolerable’ concentrations were exceeded for total dissolved solids at the 60th and 20th percentiles of the flow, respectively. In addition, records for electrical conductivity, sodium, chloride, and alkalinity frequently exceeded the ‘tolerable’ concentrations at these sites. The results for Loskop and Flag Boshielo dams are generally lower than the tolerable concentrations for the parameters evaluated. Management of the flow regulation of the Olifants River should be aimed at meeting the water quality stipulations for all users in the agricultural, domestic, industrial, and recreational sectors.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85008460","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 : 2022-10-26DOI: 10.17159/wsa/2022.v48.i4.3991
M. Jury
The climate of KwaZulu-Natal, South Africa, is evaluated for historical and projected trends in the period 1950–2100. This region lies next to the warm Indian Ocean and experiences an alternating airflow imposed by subtropical easterly and mid-latitude westerly wind belts. Multi-year wet spells have diminished since 2001 and potential evaporation deficits have spread from the Tugela Valley. Although coastal vegetation is greening and sea temperatures in the Agulhas Current are warming (>0.02‧yr−1), there are fewer rain days and less cloud cover. Tropical winds across southern Africa have turned toward Madagascar, re-directing moisture and convection away from KwaZulu-Natal in recent decades. Long-range coupled model projections of monthly rainfall display weak trends over the 21st century (−0.01 mm‧day−1‧yr−1) which are overshadowed by multi-year fluctuations (r2 = 0.04). In contrast, drying trends in potential evaporation are significant (r2 = 0.41). Forecasts of seasonal dry spells could mitigate climate change impacts in south-eastern Africa.
{"title":"Historical and projected climatic trends in KwaZulu-Natal: 1950–2100","authors":"M. Jury","doi":"10.17159/wsa/2022.v48.i4.3991","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i4.3991","url":null,"abstract":"The climate of KwaZulu-Natal, South Africa, is evaluated for historical and projected trends in the period 1950–2100. This region lies next to the warm Indian Ocean and experiences an alternating airflow imposed by subtropical easterly and mid-latitude westerly wind belts. Multi-year wet spells have diminished since 2001 and potential evaporation deficits have spread from the Tugela Valley. Although coastal vegetation is greening and sea temperatures in the Agulhas Current are warming (>0.02‧yr−1), there are fewer rain days and less cloud cover. Tropical winds across southern Africa have turned toward Madagascar, re-directing moisture and convection away from KwaZulu-Natal in recent decades. Long-range coupled model projections of monthly rainfall display weak trends over the 21st century (−0.01 mm‧day−1‧yr−1) which are overshadowed by multi-year fluctuations (r2 = 0.04). In contrast, drying trends in potential evaporation are significant (r2 = 0.41). Forecasts of seasonal dry spells could mitigate climate change impacts in south-eastern Africa.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84016441","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 : 2022-10-26DOI: 10.17159/wsa/2022.v48.i4.3951
S. Sengupta, S. Patra, R. Poddar, K. Bhattacharyya
A proper protocol of efficient irrigation and nutrient management for ginger is a necessity for boosting the productivity and quality of the crop in high-intensity cultivated lands. For this, a field experiment for 3 consecutive years was conducted in an Inceptisol of India to optimize irrigation schedule and nutrient management for augmenting rhizome yield and crop water productivity (CWP) of ginger. The trial was laid out in a split plot design with 12 treatment combinations consisting of 4 levels of irrigation schedules viz., rainfed (I1) and a ratio of 0.6 (I2), 0.9 (I3) and 1.2 (I4) of irrigation water to cumulative pan evaporation (IW/CPE) and 3 levels of nutrient management: 100% recommended dose of fertilizer (RDF) through inorganic (N1), 75% RDF (inorganic) + 25% RDF through vermicompost (VC) (N2) and 50% RDF (inorganic) + 50% RDF through VC (N3). Mean maximum growth and yield components, quality parameters, green rhizome yield (12.63 Mg‧ha−1) and highest nutrient uptake were obtained with I4N2, which was statistically on par with I3N2. The treatment combination I1N2 exhibited maximum CWP. Well-managed irrigation and nutrient scheduling is key to improving ginger production and its marketability for better financial returns.
{"title":"Improving the growth, yield, and quality of ginger (Zingiber officinale Rosc.) through irrigation and nutrient management: a study from an Inceptisol of India","authors":"S. Sengupta, S. Patra, R. Poddar, K. Bhattacharyya","doi":"10.17159/wsa/2022.v48.i4.3951","DOIUrl":"https://doi.org/10.17159/wsa/2022.v48.i4.3951","url":null,"abstract":"A proper protocol of efficient irrigation and nutrient management for ginger is a necessity for boosting the productivity and quality of the crop in high-intensity cultivated lands. For this, a field experiment for 3 consecutive years was conducted in an Inceptisol of India to optimize irrigation schedule and nutrient management for augmenting rhizome yield and crop water productivity (CWP) of ginger. The trial was laid out in a split plot design with 12 treatment combinations consisting of 4 levels of irrigation schedules viz., rainfed (I1) and a ratio of 0.6 (I2), 0.9 (I3) and 1.2 (I4) of irrigation water to cumulative pan evaporation (IW/CPE) and 3 levels of nutrient management: 100% recommended dose of fertilizer (RDF) through inorganic (N1), 75% RDF (inorganic) + 25% RDF through vermicompost (VC) (N2) and 50% RDF (inorganic) + 50% RDF through VC (N3). Mean maximum growth and yield components, quality parameters, green rhizome yield (12.63 Mg‧ha−1) and highest nutrient uptake were obtained with I4N2, which was statistically on par with I3N2. The treatment combination I1N2 exhibited maximum CWP. Well-managed irrigation and nutrient scheduling is key to improving ginger production and its marketability for better financial returns.","PeriodicalId":23623,"journal":{"name":"Water SA","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83576958","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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