146 research outputs found
Statistics for cell population identification and isolation.
No full text<p>Statistics for cell population identification and isolation.</p
Corrigendum to 'Hysteroscopy prior to a first IVF treatment cycle: the need for well-performed RCT' [Reproductive BioMedicine Online 29 (2014) 142-142]
No full textThe application of iron oxide based photocatalysts in chromium photoredox chemistry
No full textChromium(VI) is a reactive and highly toxic pollutant species which is present in certain industrial effluent streams as well as sea water and polluted ground water. Chromium(III), however, is relatively inert and less toxic. Conventional methods used to eliminate Cr(VI) from aqueous phase include its reduction to Cr(III) at acidic pH by reaction with strong reducing agents such as thiosulphate, FeSO4 and SO2, followed by precipitation as hydroxide in alkaline media. However, this procedure is not suitable for Cr(VI) elimination in dilute aqueous solutions. Thus, semiconductor photocatalysis has been studied as a possible alternative.
Photocatalysis is the process of using light to promote catalysis of reactions and normally involves the photoexcitation of a semiconductor catalyst. During photocatalysis, light of a wavelength corresponding to an energy greater than that of the band gap, Eg, of the material is incident on the catalyst, resulting in electrons being excited from the semiconductor valence band to its conduction band. These electrons can then reduce the Cr(VI) to Cr(III).
The semi-conductor used consists of nanoparticulate iron oxide embedded in a clay matrix. Clays are micro-crystalline layered minerals. This gives rise to interlayer spaces in which the iron oxide is ‘grown’. The clay structure restricts the growth of the iron oxide, resulting in nano-particulate sized semiconductor particles.
To monitor the changes in Cr(VI) concentration, a new, stable potentiometric method has been developed that involves the successful use of a gold electrode to measure Cr(VI) concentration, that has to date, not been reported elsewhere in literature. Results show that the nanocomposite does photo-reduce Cr(VI) to Cr(III) and does photo-oxidise ethanol. Modelling of the time dependence of the measured (photo-induced) potential has allowed for the extraction of key rate parameters for the Cr(VI) reduction process with a view to system optimisation
Evaluation of functional resilience in urban drainage and flood management systems using a global analysis approach
No full textEnhancing resilience in urban drainage systems (UDSs) requires new evaluation approaches that explicitly consider vital interactions between threats, system performance and resulting failure impacts during both normal and unexpected (exceptional) loading conditions. However, current reliability-based approaches only focus on prevention of functional (hydraulic) failures resulting from a specified design storm. In this study, the global resilience analysis (GRA) approach is further extended for evaluation of UDS performance when subject to a wide range of random functional failure scenarios (extreme rainfall) with varying magnitude, duration, and spatial distribution. The resulting loss of system functionality during the simulated failure scenarios is quantified using total flood volume and mean flood duration. System residual functionality for each considered rainfall block loading scenario is quantified using the functional resilience index. The developed approach has been successfully applied to test and characterise the functional resilience to extreme rainfall of an existing UDS in Kampala city, Uganda. The study concluded that: (1) UDS functional resilience is significantly influenced by both occurrence of short duration, high intensity rainfall events and spatial rainfall variation during extreme rainfall conditions and (2) future planning and design of resilience enhancement strategies should apply spatially distributed rainfall inputs to facilitate effective sizing of potential adaptation strategies.</p
Water management at BedZED - Some lessons
No full textThe Beddington zero fossil energy development (BedZED) in London, UK, is something of a modern icon in terms of assembling simultaneously on the same site new construction methods, the best of available ‘green’ technology and social engineering combined with new peri-urban lifestyles. The development also includes a number of ‘alternative’ water systems. As with many innovative and exploratory departures, however, not everything went according to plan. This paper describes the bold vision, highlights some of the issues and seeks to learn and disseminate lessons for the future, with special reference to the integrated water and wastewater services
Copula-based frequency analysis of overflow and flooding in urban drainage systems
No full textThe performance evaluation of urban drainage systems is essentially based on accurate characterisation of rainfall events, where a particular challenge is development of the joint distributions of dependent rainfall variables such as duration and depth. In this study, the copula method is used to separate the dependence structure of rainfall variables from their marginal distributions and the different impacts of dependence structure and marginal distributions on system performance are analysed. Three one-parameter Archimedean copulas, including Clayton, Gumbel, and Frank families, are fitted and compared for different combinations of marginal distributions that cannot be rejected by statistical tests. The fitted copulas are used, through the Monte Carlo simulation method, to generate synthetic rainfall events for system performance analysis in terms of sewer flooding and Combined Sewer Overflow (CSO) discharges. The copula method is demonstrated using an urban drainage system in the UK, and the cumulative probability distributions of maximum flood depth at critical nodes and CSO discharge volume are calculated. The results obtained in this study highlight the importance of taking into account the dependence structure of rainfall variables in the context of urban drainage system evaluation and also reveal the different impacts of dependence structure and marginal distributions on the probabilities of sewer flooding and CSO volume. © 2013 Elsevier B.V
Compliance with the Urban Waste Water Treatment Directive: European Union City Responses in Relation to Combined Sewer Overflow Discharges
No full textCompliance with the European Union Urban Waste Water Treatment Directive (‘the Directive’) is a pre-requisite for achieving the primary objective of the Water Framework Directive. 11 EU-27 Member States had to comply with certain requirements of the Directive by 2005. Figures released in 2009 revealed a lack of compliance for wastewater treatment, but 100% compliance for wastewater collection in 8 out of the 11 Member States. This high level of compliance has been facilitated by significant investment in collection and combined sewer overflow (CSO) discharge prevention approaches and technologies. For cities with population equivalent in excess of 1 million, the most common approach to resolving CSO issues was identified to be the addition of extra capacity. Within some cities the use of these approaches was complemented by the use of real-time control (RTC) and several cities combined both of these approaches with waste water treatment plant (WWTP) expansion and/or sewer separation. Two cities were identified as utilising source control techniques, alongside conventional approaches. Four projects utilised tunnels, in combination with WWTP expansion and RTC. It is apparent that there is not a ‘one size fits all’ intervention in dealing with problematic CSOs, when trying to comply with the Directiv
Frequency analysis of river water quality using integrated urban wastewater models
No full textIn recent years integrated models have been developed to simulate the entire urban wastewater system, including urban drainage systems, wastewater treatment plants, and receiving waterbodies. This paper uses such an integrated urban wastewater model to analyze the frequency of receiving water quality in an urban wastewater system with the aim of assessing the overall system performance during rainfall events. The receiving water quality is represented by two indicators: event mean dissolved oxygen (DO) concentration and event mean ammonium concentration. The compliance probability of the water quality indicators satisfying a specific threshold is used to represent the system performance, and is derived using the rainfall events from a series of 10 years' rainfall data. A strong correlation between the depth of each rainfall event and the associated volume of combined sewer overflow (CSO) discharges is revealed for the case study catchment, while there is a low correlation between the intensity/duration of the rainfall event and the volume of the CSO discharges. The frequency analysis results obtained suggest that the event mean DO and ammonium concentrations have very different characteristics in terms of compliance probabilities at two discharging points for CSO and wastewater treatment plant effluent, respectively. In general, the simulation results provide an understanding of the performance of the integrated urban wastewater system and can provide useful information to support water quality management
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