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Potable Water (potable + water)
Selected AbstractsPublic Provision for Urban Water: Getting Prices and Governance RightGOVERNANCE, Issue 4 2008EDUARDO ARARAL Public sector monopolies are often associated with inefficiencies and inability to meet rising demand. Scholars attribute this to fundamental problems associated with public provision: (1) a tradition of below-cost pricing due to populist pressures, (2) owner,regulator conflicts of interest, and (3) perverse organizational incentives arising from non-credible threat of bankruptcy, weak competition, rigidities, and agency and performance measurement problems. Many governments worldwide have shifted to private provision, but recent experience in urban water utilities in developing countries has shown their limitations because of weak regulatory regimes compounded by inherent problems of information, incentives, and commitment. This article examines the paradoxical case of the Phnom Penh Water Supply in Cambodia to illustrate how public provision of urban water can be substantially improved by getting prices and governance right. Findings have implications for the search for solutions to provide one billion people worldwide with better access to potable water. [source] Nanotechnologies: Tools for sustainability in a new wave of water treatment processesINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 4 2006Jean-Yves Bottero Abstract In the environmental technology industry alone, nanomaterials will enable new means of reducing the production of industrial wastes, using resources more sparingly, remediating industrial contamination, providing potable water, and improving the efficiency of energy production. This paper discusses three new kinds of nanotechnology materials that should be developed in the future: Membranes, oxidants, and adsorbents. Nanoscale control of membrane architecture may yield membranes of greater selectivity and lower cost in both water treatment and water fabrication. Fullerene-based oxidant nanomaterials such as C60 have a high electron affinity and reactivity, and are capable of producing reactive oxygen species such as singlet oxygen and superoxides. Fullerenes might be used in engineered systems to photocatalytically oxidize organic contaminants, or inhibit or inactivate microbes. The ability to tailor surfaces can help to increase adsorbing capacities or recognize specific contaminants. The potential environmental risks are that nanomaterials could interact with biota and that their toxicity adversely may affect ecosystems. As nanochemistry emerges as an important force behind new environmental technologies, we are also presented with the responsibility of considering the environmental implications of an emerging technology at its inception and taking every precaution to ensure that these technologies develop as tools of sustainability rather than becoming future liabilities. [source] Optimum matching parameters of an MPPT unit used for a PVG-powered water pumping system for maximum power transferINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2006Mehmet Akbaba Abstract Photovoltaic generator (PVG)-powered water pumping has the potential to bring potable water to millions of people in developing countries. However, due to the high initial cost of PVG units, sophisticated load matching is required between the water pumping system and PVG, in order to be able to extract maximum available power from an available PVG unit at all solar radiation levels. This requires an intermediate circuitry between the PVG unit and the motor driving the water pump, which is usually termed as maximum power point trackers (MPPT). This present paper therefore investigates the optimum matching parameters of a power conditioning circuit, which is composed of a double step-up dc,dc converter (DSUC). This MPTT circuit is used for interfacing a permanent magnet (PM) motor-driven water pumping system to a PVG for extracting maximum available power from PVG, hence maximizing the energy utilization efficiency and price,performance ratio of the whole system. It is shown that two key parameters of the DSUC, which are the duty cycle and chopping frequency, are dominating the performance of the whole system, and they are interrelated and load dependent. Therefore, optimum values of these parameters need to be determined. An example system is provided in which a complete modelling is presented in time domain and through numerical experiments it is demonstrated how the optimum values of these two key matching parameters can be determined for a given system. The MPPT circuit used in this investigation is suitable for optimum matching of all types of loads to PVG units, provided that an optimum frequency,duty cycle pair is determined for the choppers in DSUC for every 5% bands of solar radiation between 20 and 100%. Copyright © 2005 John Wiley & Sons, Ltd. [source] Application of laser scanning cytometry followed by epifluorescent and differential interference contrast microscopy for the detection and enumeration of Cryptosporidium and Giardia in raw and potable watersJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2002M.-R. De Roubin Aims: The main goal of this study was to validate a new laser scanning cytometry method (ChemScanRDI) that couples immunofluorescence detection with differential interference contrast (DIC) confirmation, against manual microscopic enumeration of Giardia and Cryptosporidium (oo)cysts. This study also assessed the basic performance of the new Association Française de Normalisation (AFNOR) NF T 90-455 method for Giardia and Cryptosporidium (oo)cyst enumeration with respect to (oo)cyst yield, linearity, repeatability, influence of turbidity and detection limit in raw and potable waters. Methods and Results: The new standard method relies on cartridge (Envirocheck) filtration, immunomagnetic separation purification, immunofluorescence staining and detection followed by DIC confirmation. The recovery was 30,50% for both parasites at seeding levels from 30 to 230 (oo)cysts. The method is linear from 0 to around 400 seeded (oo)cysts and the yield does not significantly vary for turbidity levels from 10 to 40 Formazin Nephelometric Units (FNU). The results were obtained using manual microscopic enumeration of the (oo)cysts. The ChemScanRDI yielded counts that were at least equivalent to those obtained using manual microscopy for both parasites in raw and potable water concentrates, for seeding levels of 10,300 or 10,100, respectively. The purification and labelling method proposed by the supplier of theChemScanRDI (Chemunex) reached very similar recoveries to the AFNOR protocol (70,86% in both cases). Conclusions: Laser scanning cytometry can be used as a more standardized alternative to manual enumeration as part of the new AFNOR standard method. Significance and Impact of the Study: By using laser scanning cytometry instead of manual microscopy, laboratories could circumvent the limitations of manual microscopy, namely: low sample throughput, operator subjectivity and operator fatigue. The study further supports the drive to incorporate laser scanning cytometry in the standard methods for Giardia and Cryptosporidium enumeration. [source] Influence of COD:N:P ratio on dark greywater treatment using a sequencing batch reactorJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2008Vijayaraghavan Krishnan Abstract The recycling of greywater is an integral part of a water management system owing to the scarcity of fresh water resources. This article explores the effectiveness of an aerobic sequencing batch reactor in treating nutrient-deficit and nutrient-spiked dark greywater for agricultural reuse. The dark greywater in the present investigation had a COD:N:P ratio of 100:1.82:0.76, while the preferred ratio for biological oxidation is 100:5:1 (COD, chemical oxygen demand). The aerobic oxidation of nutrient-deficit and nutrient-spiked dark greywater with a COD:N:P ratio of 100:2.5:0.5; 100:3.5:0.75 and 100:5:1 resulted in outlet COD values of 64; 35; 15 and 12 mg L,1, with a corresponding BOD5 value of 37; 22; 10 and 8 mg L,1 at 36 h hydraulic retention time (HRT). Hence treatment of nutrient-added dark greywater at a COD:N:P ratio 100:3.5:0.75 and 100:5:1 for 36 h HRT complied with the Malaysian discharge standards for agricultural activities. Treated greywater has the potential for consideration as a resource, since it can be used as a supplement or replacement for potable water in landscape irrigation and other agricultural activities in rural and urban areas. Moreover, the level of greywater treatment is dictated by the final water quality requirement. Copyright © 2008 Society of Chemical Industry [source] Chemical composition of new copper alloys for machining and its effect on their susceptibility to corrosion crackingMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2007B. Eremiá Zinc-containing copper alloys, the so-called ,,+,, brasses, are commonly used in contact with potable water. These materials are alloyed with lead to improve machinability. In wrought special brass alloys, reducing the content of this alloying element or replacing it with alternative alloying additions may give rise to a new type of machinable copper alloys which differ from the original alloys by their contents of other modifier elements such as Si (or possibly, Mg, Bi, and P). These alloys have a very low content of lead required for the break-up of chips during machining. Even though these types of brass exhibit a very good machinability, the effects of their chemical composition on the resistance of the alloy to corrosion cracking have not yet been given sufficient attention. This paper aims to present an assessment of three new types of machinable copper alloys regarding their susceptibility to stress corrosion cracking, in comparison to that of the lead-alloyed variety, in 0.05 M NaCl, NaNO2, and Na2SO4 solutions. The slow strain rate test has been used for this purpose, and its results were correlated with metallographic evaluation of the number and depth of the cracks observed on the test specimen surfaces on completion of the test. [source] Changes in the nutritional parameters of muscles of the common carp (Cyprinus carpio) and the silver carp (Hypophthalmichthys molitrix) following environmental exposure to cyanobacterial water bloomAQUACULTURE RESEARCH, Issue 2 2009Jan Mares Abstract The present study evaluated the effect of naturally developing cyanobacteria on the composition of muscles of two commercially important freshwater fish species. Fish were exposed to cyanobacterial biomass including Microcystis aeruginosa and Microcystis ichthyoblabe for 4 weeks. Then, they were transferred to dechlorinated potable water without any cyanobacteria for another 4-week period, thus modelling their preparation for consumers. Samples of muscles were collected every week during exposure and subsequent stay in dechlorinated potable water. The cyanobacterial water bloom of 3.9,6 × 105 cells mL,1 (133,383 ,g g,1 of total MC DW) induced statistically significant effects only in the content of fatty acids (P<0.05; P<0.01) in the common carp (Cyprinus carpio), while all studied parameters including the content of dry matter and fat (P<0.01), proteins (P<0.05), fatty acid composition (P<0.05; P<0.01) and some amino acids (P<0.05) were affected in the silver carp (Hypophthalmichthys molitrix). This study has shown that cyanobacteria in the environment of commercially produced fish may decrease the dietetic value of fish muscles. [source] Capitalized amenity value of urban wetlands: a hedonic property price approach to urban wetlands in Perth, Western Australia,AUSTRALIAN JOURNAL OF AGRICULTURAL & RESOURCE ECONOMICS, Issue 4 2009Sorada Tapsuwan Up to 60 per cent of potable water supplied to Perth, Western Australia, is extracted from the groundwater system that lies below the northern part of the metropolitan area. Many of the urban wetlands are groundwater-dependent and excessive groundwater extraction and climate change have resulted in a decline in water levels in the wetlands. In order to inform decisions on conserving existing urban wetlands, it is beneficial to be able to estimate the economic value of the urban wetlands. Applying the Hedonic Property Price approach to value urban wetlands, we found that distance to the nearest wetland and the number of wetlands within 1.5 km of a property significantly influence house sales price. For a property that is 943 m away from the nearest wetland, which is the average distance to the wetland in this study, reducing the wetland distance by 1 m will increase the property price by AU$42.40. Similarly, the existence of an additional wetland within 1.5 km of the property will increase the sales price by AU$6976. For a randomly selected wetland, assuming a 20 ha isolated circular wetland surrounded by uniform density housing, the total sales premium to surrounding properties was estimated to be around AU$140 million (AU$40 million and AU$230 million). [source] Application of laser scanning cytometry followed by epifluorescent and differential interference contrast microscopy for the detection and enumeration of Cryptosporidium and Giardia in raw and potable watersJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2002M.-R. De Roubin Aims: The main goal of this study was to validate a new laser scanning cytometry method (ChemScanRDI) that couples immunofluorescence detection with differential interference contrast (DIC) confirmation, against manual microscopic enumeration of Giardia and Cryptosporidium (oo)cysts. This study also assessed the basic performance of the new Association Française de Normalisation (AFNOR) NF T 90-455 method for Giardia and Cryptosporidium (oo)cyst enumeration with respect to (oo)cyst yield, linearity, repeatability, influence of turbidity and detection limit in raw and potable waters. Methods and Results: The new standard method relies on cartridge (Envirocheck) filtration, immunomagnetic separation purification, immunofluorescence staining and detection followed by DIC confirmation. The recovery was 30,50% for both parasites at seeding levels from 30 to 230 (oo)cysts. The method is linear from 0 to around 400 seeded (oo)cysts and the yield does not significantly vary for turbidity levels from 10 to 40 Formazin Nephelometric Units (FNU). The results were obtained using manual microscopic enumeration of the (oo)cysts. The ChemScanRDI yielded counts that were at least equivalent to those obtained using manual microscopy for both parasites in raw and potable water concentrates, for seeding levels of 10,300 or 10,100, respectively. The purification and labelling method proposed by the supplier of theChemScanRDI (Chemunex) reached very similar recoveries to the AFNOR protocol (70,86% in both cases). Conclusions: Laser scanning cytometry can be used as a more standardized alternative to manual enumeration as part of the new AFNOR standard method. Significance and Impact of the Study: By using laser scanning cytometry instead of manual microscopy, laboratories could circumvent the limitations of manual microscopy, namely: low sample throughput, operator subjectivity and operator fatigue. The study further supports the drive to incorporate laser scanning cytometry in the standard methods for Giardia and Cryptosporidium enumeration. [source] | ||||||||||