| 1. |
- Bakyayita Kizito, Grace, et al.
(författare)
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Kinetic studies of Cd (II) and Pb (II) ions biosorption from aqueous media using untreated and chemically treated biosorbents
- 2014
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Ingår i: Water Science and Technology. - : IWA Publishing. - 1606-9749 .- 1607-0798 .- 0273-1223 .- 1996-9732. ; 69:11, s. 2230-2236
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Tidskriftsartikel (refereegranskat)abstract
- Untreated and chemically treated Albizia coriaria, Erythrina abyssinica and Musa spp were studied in batch for uptake of Cd2+ and Pb2+ ions at pH 2.0–9.0 and agitation time; 30–390 min. Optimum biosorption conditions were; pH 4 for Pb2+ ions and pH 5 for Cd2+ ions, contact time was 3.5 hours at 24 ± 1 °C for 10 mg/L biosorbent dosage and initial metal ions concentration of 20 mg/L. Chemical treatment had a 10–17% biosorption efficiency enhancement for Cd2+ ions and a 1.6–2.3% reduction effect for Pb2+ ions. The sorption capacities for Cd2+ and Pb2+ ions for treated biosorbents were between 1.760–1.738 mg g−1 compared to 1.415–1.539 mg g−1 for untreated materials. The pseudo second order model suitably fitted the Cd2+ and Pb2+ ions biosorption data with regression coefficients (R2) between 0.9784–0.9999. Fitting of the Ho model to the experimental data showed that the biosorption mechanism for both metal ions studied was mainly a chemisorption process. Therefore, treated A. coriaria, E. abyssinica and Musa spp were potential biosorbents for remediation of Cd2+ ions and the untreated materials suitable for removing Pb2+ ions from contaminated aqueous media.
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| 2. |
- Bodlund, Ida, et al.
(författare)
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Screening of coagulant proteins from plant material in southern India
- 2013
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Ingår i: Water Science and Technology. - : IWA Publishing. - 1606-9749 .- 1607-0798. ; 13:6, s. 1478-1485
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Tidskriftsartikel (refereegranskat)abstract
- Access to fresh water is limited due to the growing population and to provide safe drinking water is a global challenge. In this initial study, about a hundred different samples were screened for coagulation activity. Amongst the plants tested were fruits and vegetable pulps, leaves and seeds (like jackfruit, tamarind, papaya, orange, watermelon, pineapple, cucumber, green gram, peas, black gram, cluster bean rice, maize, chili, cabbage, mustard, cauliflower, beetroot and carrot). The crude extracts were prepared in water and salt solution in order to extract the coagulant protein and compare the coagulation activity. Among the tested samples, only a few seed extracts showed coagulation activity. The seed extracts of mustard and cabbage showed coagulation activity in both water and salt extracts and were comparable to that of Moringa seed extract. The salt extracts showed higher activity compared to that of water extract in most of the samples tested. The coagulation activity was stable after incubation at 95 WC for 5 hours implying heat resistance. A protein profile analysis showed major protein bands with a molecular weight around 6.5 and 9 kDa. In this preliminary study, mustard and cabbage seed extracts were promising in terms of coagulation and heat resistance, so could be an alternative to Moringa seed for water treatment and should be investigated further.
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| 3. |
- Danish, Muhammad, et al.
(författare)
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Effect of solution matrix and pH in Z-nZVI-catalyzed percarbonate system on the generation of reactive oxygen species and degradation of 1,1,1-trichloroethane
- 2017
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Ingår i: Water Science and Technology. - London, UK : IWA PUBLISHING. - 1606-9749 .- 1607-0798. ; 17:6, s. 1568-1578
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Tidskriftsartikel (refereegranskat)abstract
- This study primarily focuses on evaluating the effects of solution matrix and pH for the generation of reactive oxygen species (ROSs) in a Z-nZVI-catalyzed sodium percarbonate (SPC) system to degrade 1,1,1-trichloroethane (1,1,1-TCA) in the absence and presence of a reducing agent (RA), i.e. hydroxylamine. Degradation of 1,1,1-TCA was 49.5% and 95% in the absence and presence of RA. Probe tests confirmed the generation of major hydroxyl radicals (OH center dot) and minor superoxide species (O-2(-center dot)), and scavenger tests verified the key role of OH center dot and less of O-2(-center dot) radicals. Degradation of 1,1,1-TCA decreased significantly in the presence of Cl- and HCO3-, while NO3- and SO42- had negligible effects in the absence of RA. Addition of RA significantly enhanced 1,1,1-TCA degradation by generating more OH center dot and O-2(-center dot) radicals in the presence of anions. Degradation of 1,1,1-TCA increased in the acidic range (1-5), while an inhibitive trend from neutral to basic (7-9) was observed. In contrast, a significant increase in 1,1,1-TCA degradation was observed with the addition of RA at all pH values (1-9). In conclusion, the anions and pH significantly influenced the generation and intensity of ROSs and 1,1,1-TCA was effectively degraded in the Z-nZVI-catalyzed SPC system in the presence of RA.
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| 4. |
- Fife-Schaw, C., et al.
(författare)
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Consumer trust and confidence: Some recent ideas in the literature
- 2008
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Ingår i: Water Science and Technology: Water Supply. - : IWA Publishing. - 1606-9749. ; 8:1, s. 43-48
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper reflects on two recent debates in the consumer literature on trust that have implications for consumer relations in the water industry. The first concerns an important yet seldom made distinction between trust and confidence. The second concerns when and how trust is related to acceptance of, for example, new tariffs or new technologies, and it challenges the conventional view that trust is usually a precursor of acceptance. New conceptual models addressing these debates are described and their implications for future water-related consumer research are discussed as are potential implications for industry relationships with consumers. © IWA Publishing 2008.
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| 5. |
- Garcia, Indiana, et al.
(författare)
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Removal of nitrogen and carbon organic matter by chitosan and aluminium sulphate
- 2012
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Ingår i: Water Science and Technology. - : IWA Publishing. - 1606-9749 .- 1607-0798. ; 12:1, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- River and lake waters were separated into four fractions to study the removal of nitrogen and carbon organic matter using chitosan (CH) and aluminium sulphate (AS). The fractions were very hydrophobic acid, slightly hydrophobic acid, charged hydrophilic acid and neutral hydrophilic. The results showed that the whole and fractionated water from both sources have a markedly hydrophobic character. However, lake water had a lower NOM concentration than river water. The ratio of dissolved organic carbon and dissolved organic nitrogen (DOC/DON) and dissolved inorganic nitrogen to total dissolved nitrogen (DIN/TDN) were higher in the hydrophobic fraction from both sources. Similarly DOC, colour and ultraviolet absorbance at 254 nm (UV254) also presented higher values in the same fraction. Chitosan achieved the better results in the removal of NOM from Boaco water, whole and fractionated, whereas aluminium sulphate achieved better removal from Juigalpa water. DON and DIN were removed by aluminium to about 30%. The DOC/DON and DIN/TDN ratios decreased with both coagulants in whole waters from both sources. The hydrophobic fraction contributed most to the formation of trihalomethanes, slightly hydrophobic acid being the biggest contributor. Lake water led to less THM formation than river water.
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| 6. |
- García, Indiana, et al.
(författare)
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Use of GAC after enhanced coagulation for the removal of natural organic matter from water for purification
- 2009
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Ingår i: Water Science and Technology. - : IWA Publishing. - 1606-9749 .- 1607-0798. ; 9:2, s. 173-180
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Tidskriftsartikel (refereegranskat)abstract
- Filtration with granular activated carbon (GAC) after an enhanced coagulation (EC) process was evaluated in order to determine the effectiveness of GAC in the reduction of natural organic matter (NOM), which should result in much lower formation of trihalomethane in the disinfection step. The results show that a combination of EC and GAC considerably reduces the organic matter content, which is mainly fulvic acid. This type of organic matter is removed with high coagulant dosages which neutralize their high anionic charge. A further reduction of NOM is achieved due the adsorption of NOM by GAC. As a result, the average trihalomethane (THM) concentration was only 14.5±5 mg L-1. Enhanced coagulation alone decreased the NOM concentration by 50%, but the remaining NOM reacted in the chlorination step and a higher average THM concentration was found (38±23 mg L-1). An average THM concentration of 73.8±41.2 mg L-1 was found at the drinking water plant of Boaco when conventional treatment was used. This THM concentration sometimes exceeds the maximum contaminant level of 80 mg L-1 established by the United States Environmental Protection Agency (USEPA), but not the Nicaraguan threshold of 460 mg L-1.
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| 7. |
- Govindarajan, Venkatesh, 1972-, et al.
(författare)
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Environmental impact analysis of chemicals and energy consumption in wastewater treatment plants : Case study of Oslo, Norway
- 2011
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Ingår i: Water Science and Technology. - : IWA Publishing. - 1606-9749 .- 1607-0798 .- 0273-1223 .- 1996-9732. ; 63:5, s. 1081-1031
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Tidskriftsartikel (refereegranskat)abstract
- Wastewater treatment plants, while performing the important function of treating wastewater to meet the prescribed discharge standards, consume energy and a variety of chemicals. This paper analyses the consumption of energy and chemicals by wastewater treatment plants in Oslo over eight years, and their potential environmental impacts. Global warming and acidification were the dominant impacts for chemicals and energy, respectively. Avoided impacts due to usable by-products – sludge, ammonium nitrate and biogas – play a key role in shrinking the environmental footprint of the wastewater plants. The scope for decreasing this footprint by streamlining energy and chemicals consumption is limited, however, considering that over 70% of the impact is accounted for by the eutrophication potential (thanks to the nitrogen and phosphorus which is discharged to the sink) of the treated effluent wastewater.
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| 8. |
- Hristov, Jordan, et al.
(författare)
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Virtual water and input–output framework: an alternative method for assessing trade and water consumption in FYR Macedonia
- 2015
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Ingår i: Water Science and Technology: Water Supply. - : IWA Publishing. - 1606-9749 .- 1607-0798. ; 15, s. 317-326
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Tidskriftsartikel (refereegranskat)abstract
- This study analyzed direct and indirect relationships in water consumption by Macedonian economic sectors using virtual water in an input–output framework. Macedonia was found to be characterized by intensive water consumption, with some sectors having a significant virtual water content in their products. Virtual water multipliers were used to analyze the trade balance and determine whether national commercial trade strategies are in line with Heckscher–Ohlin (HO) theory. It was found that Macedonia trade strategies in terms of virtual water were generally in line with HO theory. However, as a consequence of significant exports and high virtual water content in vegetables, fruit, grapes and sheep and goat products within the agriculture sector and in food and basic metal products in the manufacturing sector, the region was a net exporter of virtual water, losing about 124 million m3of water at 2005 level or 18% of total water consumption. Reducing exports of the most water-intensive products with significant net positive exports would result in substantial water savings of 42% of total water consumption. The results presented here can help policy makers in promoting production specializations that are more environmentally sustainable or in redesigning existing water pricing policies at national level to encourage rational use of water.
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| 9. |
- Hägg, K., et al.
(författare)
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Ultrafiltration membranes in managed aquifer recharge systems
- 2020
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Ingår i: Water Science and Technology: Water Supply. - : IWA Publishing. - 1606-9749. ; 20:4, s. 1534-1545
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Tidskriftsartikel (refereegranskat)abstract
- The natural organic matter (NOM) and color content of surface waters are increasingly becoming an issue for artificial groundwater recharge plants. Water from Lake Bolmen, in southern Sweden, had in 2017 an annual average NOM and color content of 8.6 mg/L total organic carbon (TOC) and 57 mg Pt/L respectively, and values ranging from 7.8 to 9.6 mg/L TOC and 50-70 mg Pt/L. Since water from Lake Bolmen will be used at Vomb Water Works, an artificial groundwater recharge plant, the high NOM-content of Lake Bolmen must be reduced prior to aquifer recharge. From experiences of full-scale operations of chemical flocculation, lamella sedimentation and rapid sand filtration using ferric chloride, three different pre-treatment methods were proposed; conventional precipitation, stand-alone direct precipitation before ultrafiltration (UF), and conventional precipitation with ultrafiltration after lamella sedimentation. In this study, a hollow fiber membrane (MWCO of 150 kDa) was used in different configurations during a 15 months pilot trial. The results showed the possibility to reduce NOM equal to conventional precipitation when a stable net-flux of 40 and 70 L/(m2·h) was used for direct precipitation before UF and conventional precipitation with UF, respectively. This paper presents these treatment methods and evaluates their viability as full-scale treatment steps.
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| 10. |
- Kalibbala, Herbert, et al.
(författare)
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The impact of Moringa Oleifera as a coagulant aid on the removal of trihalomethane (THM) precursors and iron from drinking water
- 2009
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Ingår i: Water Science and Technology. - : IWA Publishing. - 1606-9749 .- 1607-0798. ; 9:6, s. 707-714
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Tidskriftsartikel (refereegranskat)abstract
- Chlorine is used as a disinfectant and an oxidant in drinking water treatment to protect the public health from pathogenic microorganisms. However, if applied to raw water with humic materials, it leads to the formation of halogenated organic compounds that are a potentially serious environmental and health problem. This renders pre-chlorination of raw waters to oxidise iron inappropriate. Coagulation, the principal treatment process for removal of THM precursors, is therefore essential for chlorination by-product control. In this study, the impact of pre-chlorination and the performance of Moringa oleifera as a coagulant aid at Masaka waterworks were assessed. An average increase of trihalomethanes of over 4,000% at aeration and pre-chlorination stage was observed at the plant. From the jar tests, alum with Moringa oleifera reduced dissolved organic concentration by 47.1%. The treated water after sedimentation tasted salty but after filtration and chlorination, the salty taste disappeared. Residual iron values of 1.38 mg/L and 3.05 mg/L were achieved with MOC-SC as coagulant aid and alum alone respectively. The jar test results indicated that use of alum with Moringa oleifera as coagulant aid is promising as a first stage in the treatment train for waters with humic materials and high content of iron
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