Biomedical subjects

R M Ashley

Publications and source records attributed to R M Ashley.

11 recordsLinked to original sources

PubMed2006

Implementation impediments to institutionalising the practice of sustainable urban water management.

It is now well accepted that there are significant challenges to realising the widespread and self-sustaining implementation of sustainable urban water management. It is argued that these challenges are entrenched within the broader socio-political framework, yet often unsuccessfully addressed within the more narrow scope of improving technical knowledge and design capacity. This hypothesis is investigated through a comparative analysis of three independent research projects investigating different dimensions of the water cycle, including stormwater management in Australia and sanitary waste management and implementation of innovative technologies in the U.K. The analysis reveals significant and common socio-political impediments to improved practice. It was evident that the administrative regime, including implementing professionals and institutions, appears to be largely driven by an implicit expectation that there is a technical solution to solve water management issues. This is in contrast to addressing the issues through broader strategies such as political leadership, institutional reform and social change. It is recognised that this technocratic culture is inadvertently underpinned by the need to demonstrate implementation success within short-term political cycles that conflict with both urban renewal and ecological cycles. Addressing this dilemma demands dedicated socio-technical research programs to enable the much needed shift towards a more sustainable regime.

Cities↗

PubMed2005

The influence of biodegradability of sewer solids for the management of CSOs.

The re-suspension of sediments in combined sewers and the associated pollutants into the bulk water during wet weather flows can cause pollutants to be carried further downstream to receiving waters or discharged via Combined Sewer Overflows (CSO). A typical pollutograph shows the trend of released bulk pollutants with time but does not consider information on the biodegradability of these pollutants. A new prediction methodology based on Oxygen Utilisation Rate (respirometric method) and Erosionmeter (laboratory device replicating in-sewer erosion) experiments is proposed which is able to predict the trends in biodegradability during in-sewer sediment erosion in wet weather conditions. The proposed new prediction methodology is also based on COD fractionation techniques.

Biodegradation, Environmental↗

PubMed2005

Improved formulations for rapid erosion of diverse solids in combined sewers.

For more than a decade, research carried out in Scotland has investigated the movement of sediment in sewers and the associated pollutant release. Pollution by discharges from combined sewer overflows can adversely affect watercourses, particularly those in urban areas. Solids and dissolved contaminants, many derived from in-sewer deposits during a storm event, can be especially significant. This phenomenon can occur during events known as 'foul flushes'. In combined sewers these typically occur in the initial period of storm flows, when the concentration of suspended sediments and other pollutants is significantly higher than at other times. It has become apparent that much of the suspended load originates from solids eroded from the bed. The 'near bed solids' which are re-entrained into the flow, together with solids eroded from the bulk bed, account for large changes in the suspended sediment concentration under time varying flow conditions. This paper describes some of the methods employed to investigate the solids eroding in combined sewers during peak flow events. The work examined the potential for sediment re-suspension under high flow conditions both in the laboratory and in the field.

Conservation of Natural Resources↗

PubMed2005

Flooding in the future--predicting climate change, risks and responses in urban areas.

Engineering infrastructure is provided at high cost and is expected to have a useful operational life of decades. However, it is clear that the future is uncertain. Traditional approaches to designing and operating urban storm drainage assets have relied on past performance of natural systems and the ability to extrapolate this performance, together with that of the assets across the usable lifetime. Whether or not climate change is going to significantly alter future weather patterns in Europe, it is clear that it is now incumbent on designers and operators of storm drainage systems to prepare for greater uncertainty in the effectiveness of storm drainage systems. A recent U.K. Government study considered the potential effects of climate and socio-economic change in the U.K. in terms of four future scenarios and what the implications are for the performance of existing storm drainage facilities. In this paper the modelling that was undertaken to try to quantify the changes in risk, together with the effectiveness of responses in managing that risk, are described. It shows that flood risks may increase by a factor of almost 30 times and that traditional engineering measures alone are unlikely to be able to provide protection.

Cities↗

PubMed2004

The acoustic attenuation and hydraulic roughness in a large section sewer pipe with periodical obstacles.

The acoustic attenuation, relative sound pressure levels and the equivalent Nikuradse wall roughness under variable flow conditions in a 600 mm concrete sewer pipe are experimentally investigated. The values of the acoustic attenuation are obtained in the case of airborne sound propagation in the dry pipe. A range of values of the equivalent wall roughness is artificially generated by deploying a periodical array of engineering bricks. A novel method of rapid evaluation of the acoustic attenuation is proposed. The method relies upon sound reflections from the adjacent manholes. The results demonstrate that the acoustic attenuation depends strongly on the value of the equivalent wall roughness. This work can pave the way to the efficient methodology for the in-situ, physical evaluation of the equivalent hydraulic roughness of new and existing sewer networks.

Acoustics↗

PubMed2003

Sewer sediment transport studies using an environmentally controlled annular flume.

This paper provides an overview and some preliminary results of a collaborative project recently completed at WL Delft Hydraulics. It describes tests in an annular flume, in which sediment deposits were formed under carefully controlled and monitored environmental conditions. The deposits were then subjected to a series of time steps in which the rotational speed of the flume's top and bottom plates was increased, progressively increasing the bed shear stress. The sediment deposits were formed using three different types of sediment. An artificial organic sediment, together with a uniformly sized sand were selected as surrogate sewer sediments. The deposits in the remaining experiments were real in-sewer sediments, from catchments in the UK (Dundee) and The Netherlands (Loenen). During the erosion test, total and volatile suspended solids concentration, particle size distribution of the eroded sediment, and COD and DO levels were recorded. The bed surface topography was also measured so that the influence of the deposit formation condition on bedforms could also be examined. Where bed consolidation times were least 24 hours a biologically active surficial layer was observed to develop at the sediment/water interface. The initial deposit conditions (temperature and deposit duration) were both found to have a significant impact on the subsequent erosion of the deposit.

Environmental Monitoring↗

PubMed2003

The utilisation of engineered invert traps in the management of near bed solids in sewer networks.

Large existing sewers are considerable assets which wastewater utilities will require to operate for the foreseeable future to maintain health and the quality of life in cities. Despite their existence for more than a century there is surprisingly little guidance available to manage these systems to minimise problems associated with in-sewer solids. A joint study has been undertaken in the UK, to refine and utilise new knowledge gained from field data, laboratory results and Computational Fluid Dynamics (CFD) simulations to devise cost beneficial engineering tools for the application of small invert traps to localise the deposition of sediments in sewers at accessible points for collection. New guidance has been produced for trap siting and this has been linked to a risk-cost-effectiveness assessment procedure to enable system operators to approach in-sewer sediment management pro-actively rather than reactively as currently happens.

Cities↗

PubMed2003

Life cycle analysis and sewer solids.

The search for sustainable ways of living has necessitated a new look at the way in which water services are provided. The new paradigm includes whole-system perspectives for each of the primary criteria groups: social, environmental and economic. Whilst Life Cycle Analysis (LCA) techniques have been used successfully for products, they are much less used to assess processes. Nonetheless there is much to learn from the use of LCA for a much wider range of applications. An application is described whereby LCA has been used to determine energy, mass flows and environmental impacts for a number of sewer-related options for handling sewer solids, using the SimaPro software. This work has been part of a wider study to provide enhanced decision support systems for water utilities.

Conservation of Natural Resources↗

PubMed2002

The effect of extended in-sewer storage on wastewater treatment plant performance.

A project funded by UKWIR is under way in the UK to develop a relatively simple methodology whereby the effects of the introduction of extended in-sewer storage at CSOs on downstream sewerage and treatment can be assessed. Recent legislation (UK and European) has compelled many sewer system operators to introduce systems which increase in-sewer retention times, and also retain more flow and load within sewer networks. The project has reviewed existing knowledge about the interaction between in-sewer flow and treatment plants, together with available models. The study is utilising a "benchmark" of 3 configurations of treatment plant and dynamic simulation using the WRc STOAT software, with minor modifications to ensure that effects on odour generation and nutrient removal processes are adequately modelled. As no existing sewer flow quality model can represent the range of conditions possible in sewer networks, a combined application of the Hydroworks model and a new model developed at Aalborg University is being used for this part of the study.

Benchmarking↗

PubMed2002

The impact of the controlled emptying of in-sewer storage on wastewater treatment plant performance.

The use of in-sewer storage is generally considered to be an effective means of minimising the effects of intermittent discharges into receiving watercourses during combined flows. Despite this, very little information is available about the consequential effects these flows may have on recipient wastewater treatment plant performance. Typical problems may include biomass washout (hydraulic), and reduced biological reactor performance due to dilute loading (biological). A study is described where detailed analysis was carried out to ascertain the consequential effects of prolonged dilute loading on an activated sludge wastewater treatment plant in Perth, Scotland. Consideration was given to likely storage volumes which may have been utilised in the catchment to resolve local problems. A comprehensive analysis of resulting treatment plant performance was carried out for variations in flow and various wet weather loadings. It is concluded that storage may cause little or no benefit with respect to ammonia total emissions due to reduced treatment of dry weather flows subsequent to the prolonged combined loading period. This was exacerbated by the long regeneration times of nitrifying bacteria. However, an overall benefit with respect to BOD total emissions would always be expected, as appropriately sized storage would retain the first foul flush at the CSOs, thereby compensating the increased emissions from the downstream wastewater treatment plant.

Ammonia↗

PubMed2002

Managing sewer solids for the reduction of foul flush effects--Forfar WTP.

In times of high sewer flow, conditions can exist which enable previously deposited material to be re-entrained back into the body of the flow column. Pulses of this highly polluted flow have been recorded in many instances at the recently constructed wastewater treatment plant (WTP) in Forfar, Scotland. Investigations have been undertaken to characterise the incoming flows and to suggest remedial measures to manage the quality fluctuations. Initial visits to the works and incoming pipes indicated a high degree of sediment deposition in the two inlet pipes. Analyses were carried out and consequently, changes to the hydraulic regime were made. Measurements of sediment level, sediment quality, wall slime and bulk water quality were monitored in the period following the remedial works to observe any improvements. Dramatic alterations in each of the determinands measured were recorded. Analyses were then undertaken to determine long term sediment behaviour and to assess the future usefulness of existing upstream sediment traps. It was concluded that with proper maintenance of the traps, the new hydraulic regime is sufficient to prevent further significant build up of sediment deposits and reduce impacts on the WTP. Further investigations made by North of Scotland Water Authority highlighted trade inputs to the system which may also have contributed to the now managed foul flush problem.

Facility Design and Construction↗