This study was carried out to investigate performance of a Vacuum Rotating Membrane (VRM) type membrane bioreactor (MBR). During the study, the VRM plant was erected from scratch and operated in METU campus. The plant was composed of two tanks. First one was about 100 m3 and it was used for biological treatment / the second tank, about 30 m3, was used as filter chamber. The permeate flow rate was adjusted between 6 and 8.5 m3/h giving a hydraulic retention time (HRT) of 18 hours during the study. In the aeration tank, dissolved oxygen (DO) was adjusted to between 4 and 0.1 mg/L to see the effect of the dissolved oxygen concentration on the process. In the filter chamber, total of 540 m2 flat sheet membrane surface were used for the separation of the treated wastewater from the activated sludge. During the 140 days of operation, MLSS concentration increased from 2.5 g/L to 20 g/L. A 99.99% BOD removal and above 95% COD removal were achieved most of the time during the study. At the time when organic loading rate was between 0.35 and 0.1 kg COD/ kgVSS-day, sludge production was very low. Therefore, sludge retention time (SRT) was taken as infinite. The turbidity in the effluent was less than 1 NTU at all the time, and was below that of the tap water. In the aeration tank, 100% Total-N removal was observed when DO was 2 mg/L and MLSS was 8.36 mg/L on 80th day of operation. This indicates that simultaneous nitrification and denitrification was taking place at these conditions. Later, N-removal decreased when DO was deliberately decreased to 0.1 mg/L in the aeration tank to prevent nitrification / for treated wastewaters were intended to be used for irrigation. Since the pores of the membrane were 0.038 &amp / #956 / m, treated wastewaters were sterile with respect to bacteria

Radioisotopes of caesium (Cs) and strontium (Sr) have been distributed in the environment due to weapons testing, nuclear power production and accidents at nuclear facilities. Radiocaesium and radiostrontium are of major concern in the medium to long term following accidental releases as they have high energies, long half lives (137Cs≈30 years; 90Sr≈29 years) and their easy assimilation into biological systems due to their similarity to the biologically important elements potassium (K) and calcium (Ca), respectively. Radio-caesium and -strontium are transferred to humans primarily via plant root uptake, and therefore minimising this uptake has been the focus of a number of remediation strategies, such as ploughing and fertiliser application. Species or cultivar substitution, where a species/cultivar that has higher uptake is replaced by a species/cultivar that has lower uptake, has been proposed as an effective and socially acceptable remediation strategy for contaminated agricultural land, but not enough is known about its efficacy for it to be recommended internationally. The aim of this thesis is to evaluate the potential of species or cultivar substitution as a remediation strategy for contaminated agricultural areas. Chapter 2 consists of meta-analysis of the available data (115 experiments) on the inter-cultivar variation in Cs and Sr accumulation by 27 plant species. Chapter 3 includes experiments conducted in the laboratory (UK) and two experiments in the field (Ukraine) investigating inter-cultivar variation in radiocaesium and radiostrontium accumulation in Brassica oleracea, and whether consistently lower-accumulating cultivars could be identified. Chapter 4 details analysis of samples from grass breeding experiments in Aberystwyth and Edinburgh (UK) from four forage grass species; hybrid ryegrass (Lolium perenne L. x Lolium multiflorum Lam.), L. perenne, L.multiflorum and Festuca arundinacea Shreb., and investigates inter-species and inter-cultivar variation in uptake of stable Cs and Sr. Hybrid ryegrass cultivars that were lower-accumulating in Cs and/or Sr were also identified. Chapter 5 compares the stable Cs and Sr uptake in six L. perenne and two F. arundinacea cultivars grown in Aberystwyth and Narodychi (Ukraine). Chapter 6 compares the performance in terms of yield and forage quality (elemental concentrations, digestibility and water soluble carbohydrate content) of six hybrid ryegrass cultivars and ten F. arundinacea cultivars identified as consistently lower-accumulating in Cs and/or Sr against the performance of two commercial hybrid ryegrass cultivars. The mean inter-cultivar variation in Cs and Sr was 1.8-fold and 2.0-fold,respectively when 27 plant species were studied. Thirty-five-fold variation in radiocaesium and 23-fold variation in radiostrontium was found between c.70 Brassica oleracea cultivars. In two field experiments in Ukraine, five cultivars had consistently lower radiocaesium concentration ratios and two cultivars consistently lower radiostrontium concentration ratios. One cultivar had lower radiocaesium and radiostrontium concentration ratios. Festuca arundinacea cultivars had lower Cs and Sr concentration ratios than cultivars of hybrid ryegrass, L. perenne and L. multiflorum. Three out of 17 hybrid ryegrass cultivars had consistently lower Cs concentration ratios, two cultivars consistently lower Sr and one consistently lower Cs and Sr. Despite differences in soil properties and environmental conditions, F. arundinacea cultivars grown in Aberystwyth and Narodychi accumulated less stable and radioactive Cs and Sr than L. perenne cultivars. One L. perenne cultivar also accumulated less Cs and Sr at both sites. F. arundinacea cultivars accumulated less Cs and Sr than commercial hybrid ryegrass cultivars, but alsohad up to 59% lower yield and a reduction of up to 19% in K accumulation, up to 46% in Ca accumulation, up to 7% in dry matter digestibility and up to 17% in water soluble carbohydrate content. Selecting lower accumulating cultivars was found to reduce Cs and Sr accumulation less, but with a smaller yield penalty and a smaller reduction in digestibility and water soluble carbohydrate content. It is concluded that species and cultivar substitution could be an effective remediation strategy in contaminated agricultural land provided implications for yield and quality are considered.

The conversion of ocean wave energy has the potential to supply utility magnitudes of electrical generating capacity. It has been predicted that the UK has an annual, practical wave energy resource of 50 TWh which represents 12.5 % of the total electricity consumption. The lack of convergence in the design of wave energy converters, demonstrates that there is not yet a clearly superior concept and so the development of novel technologies is continuing. OWEL’s novel wave energy converter was intended to overcome some limitations of floating OWCs whilst retaining many of the beneficial synergies. The simplicity of the collector, no submerged moving parts and a uni-directional air turbine PTO are all advantages of the technology. A review of the previous development work concluded that little was known about the operating principle of the device and that its hydraulic design was not understood. Through the extensive small scale, physical modelling of three different device geometries, the conversion process was investigated to increase knowledge and inform the hydrodynamic design. Initial studies considered a simplified duct geometry and found that the suggestions from the previous development phases of the technology were inaccurate and so were discounted. The methodologies developed were used in subsequent testing and provided initial learning on which the future experiments were based. A multi-duct model was tested in a wave basin in order to investigate whether such a configuration would be suitable as a future commercial device. Energy conversion efficiencies exceeding 40 %, proved the potential of the configuration but the testing highlighted the many complexities of the platform that should be addressed before being further developed. A single duct was studied to evaluate and improve the design of a proposed marine demonstrator being developed consecutively with this research in a commercial project. Testing the sensitivity of performance to changes in the geometric design and naval architecture resulted in a configuration that maximised the conversion efficiency. Various numerical modelling options were considered to create a performance model. CFD was deemed to be the most suitable method to capture all of the relevant flow physics in the conversion process and to provide a useful design tool. A preliminary model was developed to demonstrate the applicability of the method and provide the foundation for further work. Annual, large scale energy productivity analysis for the optimised device predicted that a 42 m long, single duct would be able to generate 154 MWh/yr at Wave Hub. This was equivalent to a 124 % increase over the original baseline design. Predicted electricity generation for the EMEC site was comparable to the predictions for a competing technology. Although both predictions were relatively low, it was anticipated that these would increase as the designs mature.

A laboratory scale prototype mesh bioreactor (MeBR) for the two-stage anaerobic digestion (AD) of biodegradable municipal waste (BMW) was successfully designed and tested. The development involved a number of preliminary stages; creation and characterization of a synthetic BMW (SBMW), exploration of its single-stage AD characteristics under both methanogenic and hydrolytic conditions, and AD trials of a two-stage reactor system where SBMW was fed to a 1st stage hydraulic flush (HF)reactor and centrifuging was used as a method to produce liquid effluent which was fed to a 2nd stage anaerobic filter (AF) reactor. The single stage digestion of SBMW suffered from process instability at very low organic loading rates (OLR) of 2-2.5 gVSl-1d-1 whilst the two-stage HF/AF system was robust up to a maximum OLR of 7.5gVS/ld. The HF reactors became methanogenic due to the effect of effluent recycling. After this, two different prototypes designs of MeBR were built and tested in continuous two-stage AD trials (AF 2nd stage). The aim was to replace the centrifuging of the HF reactors with continuous mesh filtration whilst maintaining the stable and robust digestion process. The first design confirmed the ability to filter SBMW digestate through nylon meshes of pore size 30-140 >m at an OLR of 3.75 gVSl-1d-1. The mesh system operated similarly to the HF/AF system and efficient two-stage AD of the SBMW was shown. Problems with stirring thick digestate limited the OLR on both the mesh and HF systems. To address this limitation on OLR, a 2nd MeBR was designed which employed a rotating drum for low effort mixing and 100 >m nylon mesh sections on the drum surface for filtration. This reactor system operated stably at an OLR of up to 15 gVSl-1d-1 albeit with reduced specific methane production. Application of this type of system will be dependant on requirements for high plant throughput, system robustness and a compact process to make up for slightly lower methane production and waste stabilisation compared to single stage digestion.

The global demand of the volume of woody biomass (such as wood, logging residue, sawdust and so on) is huge and increased annually, due to its new application for the energy/fuel production during recent years. Pyrolysis is termed as a promising thermo-chemical technology to convert woody biomass to liquid, gas and solid fuels/chemicals. The better understanding of the pyrolysis mechanism of woody biomass is demanding considering the thermal performance of individual components (hemicellulose, cellulose and lignin) and their interactions. In order to develop the current understanding of the pyrolysis of the individual components (hemicellulose, cellulose and lignin) in woody biomass and fill the knowledge gap on their interactions under pyrolytic conditions, the on-line pyrolysis and off-line pyrolysis study of the model compounds of the components and their “synthesized biomass” samples has been extensively investigated employing TGA-FTIR and fast pyrolysis unit, in terms of the mass loss variation against temperature together with the on-line identification of the evolved volatiles by FTIR, yield of pyrolyzed products (gas, bio-oil and char) from the fast pyrolysis unit, variation of the compositions in bio-oil and gas products against the fluidized-bed-reactor temperature, the chemical pathways for the chemical structure change of the macromolecules and the cracking of the primary fragments, and the interactions among the chemical components. The proposed chemical pathways, indicating the possible competitive and/or consecutive relationship among the prominent compounds in bio-oil and gaseous product, give hints to improve the current kinetic scheme of the individual components. Notably, the vapor-phase interaction among the components in the fluidized-bed reactor is investigated in terms of the product yield and variation of the prominent compounds in bio-oil and gaseous product, but their interactions in solid/liquid phase are not involved.

The focus of this thesis is on the prediction of sound attenuation through a lined duct, based on a mathematical model. Ducts with a single section as well as multi-segmented sections are discussed. The duct of interest has a rectangular cross-section as normally used for ventilation purposes. The mean flow in a ventilation duct is very low and can be neglected. In this thesis, two-dimensional analytical models are developed for sound transmission in a series of different duct configurations. Two models of the lining behaviour are considered, either locally-reacting or bulk-reacting. The models are used first to obtain the transverse and axial wavenumbers of various modes of the duct. The required finite numbers of wavenumbers are tracked using Müller’s method. The wavenumbers are traced from a very low frequency to high frequency using small frequency steps. It is found that, for a duct with a bulk-reacting lining, the number of modes with a transverse wavenumber below a particular value may exceed the corresponding number of modes in a duct with a locally-reacting lining. These additional modes are termed lining modes. The number of lining modes depends on the lining thickness. Dispersion curves are presented for both types of lining. The transmission of sound through the duct is then calculated using the mode-matching technique. The mode-matching model allows analysis of multi-modal wave propagation in the duct. The model is first developed for an infinitely long rigid duct with a finite length of lined insert. The estimation from the locally reacting model, that is widely available in the literature, is compared with the estimation from the newly developed bulk-reacting model. Although the locally reacting model often overestimates the performance of a bulk-reacting lining it is found that this is not always the case, especially for a small lining thickness and at lower frequencies where the locally reacting model may under-estimate the performance. The analytical model is then extended to a multi-segmented lining where the lined section is uniformly segmented with rigid walled sections in a periodic manner. For a bulk-reacting lining, the segmented arrangement renders the lining more similar to the behaviour of a duct with a locally-reacting lining and improves the peak attenuation. Little improvement is found in the case of a multi-segmented locally-reacting lining. The effect of duct height, lining thickness and lining flow resistivity on sound attenuation is studied using the analytical model. Experiments are presented which validate the analytical model.

In this work, a new thermo-mechanical model is developed by improving on an existing one, applicable to large deep seated landslides and rockslides consisting of a coherent mass sliding on a thin clayey layer. The considered time window is that of catastrophic acceleration, starting at incipient failure and ending a few seconds later, when the acquired displacement and velocity are such that the sliding material begins to break up into pieces. The model accounts for temperature rise in the slip zone due to the heat produced by friction, leading to thermoplastic collapse of the soil skeleton and subsequent increase of pore water pressure. This in turn drastically decreases the resistance to motion and allows the overlying mass to move downslope ever more freely. The proposed model is implemented numerically and validated by back-analysing the two well-documented catastrophic landslide case histories of Vajont and Jiufengershan. The model is then employed to carry out a parametric study to systematically investigate the development of catastrophic failure in uniform slopes. It was found that the most influential parameters in promoting catastrophic collapse are (1) the static friction-softening rate a1, (2) the slope inclination β, (3) the soil permeability kw, (4) the dynamic residual friction angle rd φ and (5) the overburden thickness H. The most dangerous situation is when a1, β and H are very large and kw and rd φ are very low. Of the above, the ‘thermo-mechanical parameters’ kw and H deserve more attention as they have been introduced by the thermo-mechanical model and are not normally considered in standard stability analyses of uniform slopes. A second parametric study was performed to demonstrate that thermo-mechanical parameters alone can make a difference between a relatively non-catastrophic event and a catastrophic one. Hence, further insight into the design of landslide risk mitigation measures can be gained if, in addition to the standard site investigations, the permeability of the soil is measured and the depth of an existing or expected failure surface is measured or estimated respectively.

Food and energy security are two key environmental challenges currently faced by mankind. The principles behind organic farming are to promote environmental sustainability; however within the organic standards the use of renewable energy is only a suggested method with which to achieve this. If organic farmers can successfully utilise anaerobic digesters, they could contribute towards the provision of both food and energy security using one holistic system. Within this thesis, the suitability of anaerobic digesters on organic farms was explored using methods from ecological, sociological and environmental sciences. This enabled both the practical and theoretical issues behind the question of whether it is suitable for anaerobic digesters to be used on organic farms to be addressed. Field and laboratory experiments were used to compare the effects digestate and slurry had on earthworms, grass and weeds. Digestate and slurry had species dependent effects on earthworms during both LD50 / LT50 experiments and behavioural bioassays; Lumbricus terrestris survived longer in slurry and showed a behavioural preference towards slurry over digestate, whereas Eisenia fetida showed the opposite responses. Fertiliser application rates over 170 kg N ha-1 were found to be harmful to both species of earthworm. Suppressed germination effects were seen on thistles treated with digestate compared with no treatment (F0.56,19.66 =4.66, P < 0.01), whilst grass fertilised with digestate had a greater total mass than grass fertilised with slurry or left unfertilised (F2,27 =17.92, P < 0.001). Questionnaires and interviews were used to obtain a better understanding of the opinions farmers had about anaerobic digesters. Organic farmers believed renewable energy generation fitted well within organic principles, but using an anaerobic digester on an organic farm was less practical than on a conventional farm. This was due to multiple reasons including lack of information, poor associated finances, and that existing digesters are currently unsuitable for small organic farms. There was also support for anaerobic digesters to be on dairy farms- this was regardless of whether the farm was organic or conventional. Two case-study farms were used to assess the impact an anaerobic digester would have on the farms total GHG emissions. An anaerobic digester on the dairy farm was calculated to reduce GHG emissions by up to 24%, while for the mixed farm, the maximum reduction was by 20%. This was primarily due to the fact that the dairy farm benefitted from a higher volume of feedstock and proposed to use the biogas in a more energy efficient manner by producing electricity rather than vehicle fuel. Due to the high emissions associated with keeping livestock, both case studies needed to import additional feedstock if the farms were to achieve zero net GHG emissions. The answer to whether anaerobic digesters can be suitable for organic farms was judged on how well they complimented or conflicted with IFOAM’s definition of organic farming. Three main aspects of their definition were chosen and evidence from each chapter used to address the main question of the thesis. In conclusion, anaerobic digesters are theoretically suitable for use on organic farms, but are generally more practical for use on conventional farm systems. Across both farm systems the most suitable enterprises to adopt anaerobic digesters are dairy farms. This highlights the need for suitability of new systems to be assessed on a case-by-case scenario when trying to maximise positive impacts from new technologies.

No description available.

The search for alternative landfill operation and management strategies has triggered the development of the concept of a landfill as a bioreactor. The application of the concept requires the recirculation of liquids and hence a better understanding of fluid flow and transport processes that are strongly controlled by the physical structure of the media. It is generally accepted that as a result of the deposition in progressive layers, compaction and heterogeneity; solid waste develops a strong and anisotropic structure. Also, that due to their flat shape and orientation, materials such as plastics and textiles can influence flow behavior. The aim of this research was to provide a better understanding of the structure that develops when solid wastes are landfilled and the influence of this structure on fluid flow. The research included a characterization and description of specimens of raw household waste (MSW) and pretreated wastes (MBT) using PSD mathematical models, an study of the changes caused to particle size and shape by degradation processes, a study of the effect that flat shaped particles have on the fluid flow characteristics of a porous medium, and an investigation of the structure of a MSW specimen applying invasive and non-invasive radiographic techniques. The study revealed that the characteristics of particle size and shape differ between waste materials and also change with degradation. An MBT specimen that had gone a dual anaerobic aerobic treatment showed statistically insignificant changes in particle size and shape with degradation, whilst partially treated MBT and MSW specimens showed significant changes in the particle size and in the content of flat shaped materials. PSD models were successfully fitted to the different specimens investigated suggesting that analytical expressions can be incorporated into existing waste behavioural mathematical models to characterise the particle size. Flat shaped particles that comply to be at least 15 times larger than the matrix particles and constitute at least 7.3% by dry mass were found to reduce the hydraulic conductivity by a factor of more than 30%. The reduction factor is controlled by the relative content and size of the intrusive particles and it is always within one order of magnitude. The use of dye tracer visualization, thin sectioning and μCT techniques were pioneered during this research for the study of preferential flow and the structure in solid waste. This study evidenced that the presence of high content of inert coarse flat shaped materials in a specimen of MSW resulted in the development of a strongly layered structure, with large pores horizontally connected and that favoured preferential flow.