The assessment of room air movements, in all but elementary cases, relies on investigations using either full-size mock-ups or scaled models. Temperature considerations severly limit the maximum geometric scale factor. A solution is offered by which accurate predictions of the air flows in full-size air-conditioned rooms may be obtained from observations. made with small models if certain criteria are satisfied. The maximum geometric scale-factor can be increased to 8.5, while limiting the maximum working temperature in the model to 100°C, by replacing the convective currents with wall jets of a similar velocity profile, volume flow, momentumfl ux and heat content. A further improvement may be achieved if the scale-factor adopted for the jet nozzle is smaller than the geometric scale-factor. This approach can lead to scale-factors exceeding 11.8. Theoretical studies have shown the replacement of convective currents by plane jets is feasible. In the course of the study, detailed investigations of areas important for the aimsof the project but where there is a dearth of relevant information, were undertaken. To test the validity of predictions and to establish necessary empirical factors, a range of measurements of convective currents and their replacement jets were'carried out. The results showed that a virtual identity of maximump rofile velocity, momentumfl ux and volume flow at the replacement cross-section could be achieved. Based on measured empirical factors, a simple procedure, valid for the majority of practical applications, by which replacement jets can be calculated directly from convective surface parameters is given. Thus, the aim of this study, namely the worthwhile use of a small model which can be constructed cheaply, has been achieved.

The research described in this thesis is part of a wider EU-LIFE project, the WaterRenew project. The WaterRenew concept can be described as the recovery of nutrients from wastewater which can lead to eutrophication of surface waters, by irrigation of short rotation coppice in order to fertilise them. Such systems have been proven to function properly as nutrient removal systems when studied for N removal and have already been successfully and commercially implemented in different countries. However, the factors potentially preventing them from operating sustainably have not been identified nor their upper limits quantified with confidence. A WaterRenew system can indeed be looked at as a unit composed with three main compartments; soil, soil water and plant. Therefore, the sustainability of such a system will be compromised if at least one of these compartments is changed irreversibly. The limits can be hydrological with constant runoff or drainage being induced. They can also be chemical with inadequate amounts of nutrients removed from the effluent applied or irreversible accumulation of nutrients in soil. Finally, these limits can be physiological with the trees’ health being irreversibly compromised. Moreover, the relevance and effectiveness of such a system under UK conditions has not been established yet. In this context, a field trial was set up at Cranfield University sewage treatment works where the secondary treated effluent was irrigated on to Salix viminalis, Populus trichocarpa and Eucalyptus gunnii trees planted at a density of 13,060 trees.ha-1, on a chalky clayey soil, in order to maintain soil water content at field capacity. To tackle more specifically P fate processes understanding, an independent P leaching soil column experiment was also set up. With the latter settings, it was possible to apply high volumes of effluent (3625 mm for willow, 2895 mm for poplar and 3345 mm for eucalyptus for the 2 years of irrigation) and high amounts of nutrients (1023 kg-N.ha-1 and 134 kg-P.ha-1 for willow, 834 kg- N.ha-1 and 108 kg-P.ha-1 for poplar and 946 kg-N.ha-1 and 127 kg-P.ha-1for eucalyptus for the 2 years of irrigation). It was found that irrigation with effluent increased significantly tree yields so that they were within the range reported in the literature for willow and eucalyptus but slightly lower for poplar. The trees uptook between 20 % and 50 % of the total amounts of N and P applied with eucalyptus uptaking more nutrients than willow, which in turn took up more than poplar. Then, it was found that irrigation did not have any significant effect on N and P in soil and the amounts applied remained very low compared to the existing nutrients soil pools. However, irrigation did have a significant effect on increasing K and Na in soil. Na increased enough to induce a significant increase in soil SAR but soil remained neither saline nor alkali. The trees had a smaller impact on soil chemistry. Finally, it was found also that irrigation did not have any significant effect on N and P in soil water with no P detectable in any of the soil water and groundwater samples during the whole experiment. Irrigation did, however, increase significantly K and Na concentrations in soil water and for K also in groundwater. From the point of view of nutrients removal, although a tree effect was measurable, it was not as important as the functions of the soil. Thus, when a WaterRenew system is maintained under a hydrological constraint, with the soil moisture kept at field capacity, it was still possible to apply high volumes of effluent, even on a clayey soil. In addition, the consequent high amounts of nutrients applied were efficiently retained between tree uptakes and mainly soil organic and inorganic nutrients’ pools. Indeed, the amounts of nutrients lost by drainage remained low (<10 % of the total amounts applied) for N and P and groundwater was efficiently protected from pollution on this site. On P dynamic processes understanding, it was found that P leaching patterns depend highly on soil moisture and to a lesser extent on the amount of P applied. When soil is saturated, P will start leaching even when applied at a very low concentration. A model, the WR_MODEL, was developed which integrates the observations, measurements and understanding of Cranfield University sewage treatment work field trial and soil column experiment into a model. The purpose of WR_model is to help the design and implementation of a WaterRenew system in any location as long as climatic and soil data are available. The model default values are for England and Wales climatic and soil data.

Rain gardens refer to planted shallow depressions widely adopted in urban areas to integrate vegetation and soil to mitigate the increasing urban stormwater issues, and are also perfect spots to adopt taxonomically diverse plantings to provide habitat values and aesthetics. However, few studies to date have successfully reflected the horticultural aspects and planting potential in rain gardens. This PhD is divided into three separate studies, which aim to characterise the success of a range of potential plants with different traits and different geographical origins in typical rain garden conditions and to access the relative hydrologic performance of different vegetation types to make informed planting decision, as well as to investigate the establishment of low-input in-situ sown vegetation in rain gardens. The first study tested a range of potential native and non-native forbs and grasses in simulated rain garden cyclic flooding and extended drought. Results confirmed existing expectations with respect to which plants would be best suited to the bottoms, slopes and margins of periodically-inundated rain gardens. In the second study, experimental rain gardens planted with taxonomically diverse plantings composed of forb-rich perennials, mown grasses and bare soils were tested with artificial rainfall. The forb-rich perennial mixes featuring greater species richness and structural diversity consistently provided the best hydrologic performances, and can therefore be recommended for use in rain gardens. In the third study, in-situ sown forb-rich plantings were created in practical rain gardens with the involvement of two low-impact weed control measures including the use of felt mats and mulching. Mulching shows significant effectiveness on weed control, whereas no valid conclusion could be drawn on the effectiveness of felt mats due to the contamination of the potentially weedy compost mulching. The ‘dry-wet’ moisture gradient in rain garden depression was determined to significantly influence the establishment of sown plantings.

The aims of this research project were to assist in understanding hydrate formation, stability, and scientific aspects of CO2 storage as a liquid and CO2 hydrate. These have been addressed by two investigatory pathways: hydrate stability modelling and hydrate formation within sediments (in synthetic CO2 hydrates and natural methane hydrates). Developed computer models predict large regions offshore Western Europe with the potential to store considerable volumes of CO2 as a hydrate. Laboratory experiments have also shown CO2 hydrate to form rapidly and relatively easily in sandy sediments, cementing the sediment grains. In water-rich environments hydrate appears to create pore-filling cement impeding further CO2 flow to underlying sediments, which may aid trapping of an underlying liquid store. Fortunate acquisition of natural hydrate cores from Cascadia Margin also allowed investigation of natural methane hydrate formation; revealing a number of well-preserved methane hydrate morphologies, and complex brine filled pore networks within the hydrate, resulting from different rates of growth. Results highlight a number of research areas, which need addressing through further investigations. However, these preliminary investigations support CO2 storage as a hydrate as a potential feasible storage method, and this method should be pursued further as an emissions reducing mitigation strategy.

Modelling the mechanical behaviour of engineering phenomena has occupied the attention of researchers since Karl Terzaghi's pioneering work on settlement due to consolidation in 1925. Soil improvement methods using vertical drains in combination with pre-loading were used for soil stabilization at the San Francisco- Oakland Bay Bridge in 1926. Over the next decades, other drain methods, including prefabricated and pack drains, were developed and used for practical purposes. In the mid-1990s, vacuum-induced consolidation became a reliable technology, thanks to a rethinking of theoretical principles that led to the Menard vacuum system. The Menard system was used successfully, for the first time in South Korea, for construction of the Kimhae sewage treatment plant. The drain method is based on Terzaghi's one-dimensional consolidation theory and Barron's vertical drain. Even when using finite element simulation, numerical solution for consolidation problems involves averaging material properties such as elastic modulus, Poisson's ratio, and coefficients of permeability. But the results are too unreliable to use for practical purposes. Classical mechanics alone do not provide sufficient information on the global motion equation of fluid in a porous media. A new approach is presented in this paper to the problem of continuum modelling of vacuum-induced consolidation due to pumpage. This finite element continuum model uses the interior boundary condition instead of installed vacuum tube as a line, with changing pore pressures at the installed material being treated as boundary conditions of the interior part. An innovative linear equation solution method for separate fixed boundary conditions is presented. The efficacy of this model for field construction is shown by comparing results with the results obtained from field measurements at the Jangyoo sewage plant. Because the properties of material are not exact in their natural states, the results of the calculated finite modelling are similar but not a mirror image of field measurements. Whereas conventional one-dimensional calculation uses only one point, the finite element continuum model shows displacements and pore pressures for a whole section. Once the exact material properties have been determined, the model can be applied effectively to field analyses, predicting settlements due to pumpage and facilitating decision making about when pumpage should start and stop. The finite continuum model for consolidation due to pumpage can be applied to other soil improvement methods, such as prefabricated and pack vertical drain, with some modification.

No description available.

No description available.

The worldwide yeast extract business is large and may increase with the interest in natural products and nutrients. The wastes from the yeast extract industry have traditionally been used as animal food or soil injection for agricultural benefit. This process is now being challenged and is experiencing increasing costs therefore alternative options for disposal routes are being considered. The poor biodegradability of activated sludge cell walls is well known and it has been suggested that the rigid, double layered yeast cells will be even more recalcitrant. Previous work reviewed in the thesis, had indicated yeast cell walls are some of the most refractory natural microbes in comparison, for example with activated sludge. The thesis revisits the issue of solids hydrolysis and in particular with a waste containing yeast cell walls as model solids. The literature review discusses previous work on the treatment of yeast containing wastes, including reactor designs and potential pre-treatments. It covers the work done on the fundamental characteristics of solids which might affect biodegradation rates, e.g. particle size, cross linking, rigidity and viscosity. Laboratory experiments were conducted and the results analysed from batch biodegradability testing and continuous simulation trials comparing anaerobic reactors. These were CSTR, Filters and UASB the latter noted for its vulnerability to solids. Laboratory work is also reported on the potential for ultrasonic, thermal and acclimatization to improve degradation rates. Utilisation of ultrasonic pre-treatment at 20,000 KHz, increased soluble organic carbon from between 14 to 120% dependant upon power and exposure time period. The results also showed that continuous recycle at low power produced the best results with increased gas yield and organic conversion from a lower solids retention. Results are also reported from onsite pilot trials using a 25m3 UAF digester and an analysis of previously unreported full scale yeast processing plants in the UK. These results confirmed that solids (cell) degradation rates were low. In conclusion the thesis suggests the degradability of the yeast cells are linked to their unique cell walls. Anaerobic digestion does give organic conversion albeit with long HRT's. The use of ultrasonics as a pre-treatment process enhances this conversion and improves gas yield.

The transport of solids in "horizontal" above ground drainage pipes was the subject of an investigation aimed at establishing a method for the design of deposit free drainage systems. Tests were based on the measurement of solid velocity in a discharge pipe of variable gradient, the solid being a maternity pad either with or without three paper towels. A test rig capable of supporting discharge pipes of various materials, enabling the incorporation of bends and junctions, was employed and an instrumentation method for measuring solid velocity, depth of flow and rate of flow was developed. Results showed that solid velocity in straight discharge pipes can be characterized by three separate zones of flow, the second zone being the most fundamental, with solid velocity defined by an equation of the form V = (C1-C2)*Sqrt(L/G), where C1 and C2 are empirical coefficients, L is the distance travelled from the w.c. discharge and G is the pipe gradient. The limits of the flow zones can be defined by values of Sqrt(L/G), the larger limit defining the maximum length of deposit free discharge pipe at any gradient. The effect of pipe fittings on the velocity of the solid can be represented by a sharp velocity reduction followed by a gradual velocity regain and may be ignored as long as the pipe fitting is positioned approximately 5 metres before the end of the second flow zone conditions, as defined by a value of Sqrt(L/G), thus allowing sufficient length for the velocity to regain its straight pipe characteristic value. A design method is presented, based on the experimental data collected, which in its present form can be applied to check for the possible deposition of Solids within the "horizontal" discharge pipe system, either due to traversing excessive lengths of horizontal pipework or as a result of bend or junction positioning.

Nonylphenol ethoxylates (NPEO) are commercially available non-ionic surfactants that, along with the parent nonylphenol (NP), are considered to be possible endocrine disrupters. NP and NPEO are resistant to conventional aerobic biological water treatment systems. Alternatives to this technology are sought to remove these and other bio-resistant compounds from wastewaters. Composites of the photocatalyst, TiOi, and activated carbon (AC) adsorbents have been prepared, characterised and applied as adsorbents and photocatalysts in removal of phenols and NPEO from aqueous solution. Two methods were utilised to prepare of TiO2/C composites. AC was coated with TiO2 derived from the hydrolysis of Ti(OPr')4, and with Degussa P25 using a polyvinyl alcohol binder that was subsequently carbonised in an inert atmosphere. The TiO2/C composites were characterised by nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible reflectance spectroscopy and scanning electron microscopy. The AC and TiO2/C adsorption capacity for phenol was observed to be affected by the surface area and surface chemistry of the adsorbent, as well as the pH of solution. The NPEO adsorption capacity and rate of adsorption was found to be dependant on the pore size distribution of the adsorbent. The effect of surface chemistry and solution pH was minimal. The selectivity of the adsorbent in the adsorption of NPEO was studied using HPLC. The rate of photooxidation of phenol was found to be first-order and greatest under basic conditions. This is attributed to changes in the electronic structure of the TiO2 under these conditions that increases the rate of reduction of molecular oxygen, often considered to be the rate limiting step. Photodegradation of NPEO led to the aggregation and sedimentation of TiOz particles. HPLC and GC-MS analysis identified photomineralisation intermediates and the mechanism of photodegradation of NPEO is discussed.