The emission and dispersal of bioaerosols from commercial composting facilities has become an issue of increasing concern over the past decade, as historical evidence links bioaerosol exposure to negative human health impacts. As a result, recommended concentrations and risk assessment limits were imposed in 2001. However, more recent research has suggested that these limits may be exceeded under certain circumstances. For example, underestimation of bioaerosol concentrations may occur through „snapshot‟ sampling, and the use of methods that may reduce culturability of bioaerosols. This study aimed to address several gaps in knowledge, including quantification of bioaerosol concentrations downwind from sites, analysis of the effect that operational and environmental influences have on emission and downwind concentrations, and investigation of methods for the enumeration of non-culturable bioaerosols. The concentrations of bioaerosols upwind, on-site and downwind from two open-air green waste windrow composting facilities were enumerated in extensive detail, producing the first detailed and validated database of bioaerosol concentrations at green-waste composting facilities. The effects of composting processing activities, season, and meteorological conditions on concentrations were also investigated utilising this dataset. Results from these studies suggested that bioaerosols are able to disperse in elevated concentrations to distances beyond the 250 m risk assessment limit. Downwind peaks in concentration were directly linked to compost processing activities on-site, with the risk of sensitive receptor exposure to bioaerosols during non-operational hours minimal. Further, it was found that patterns in downwind concentrations of bioaerosols are likely to be governed by buoyancy effects, as a second peak in concentrations was found at 100-150m downwind. This finding was further supported through the use of a novel direct counting method. Finally, molecular methods allowed the composition of bioaerosols emitted from composting to be determined and showed that composting significantly alters the aerobiotic community at distances downwind. The methods investigated provide the potential for detailed, continuous measurements of bioaerosols, alongside identification of potentially pathogenic microorganisms, and could ultimately lead to source apportionment of bioaerosols.

This PhD research project is primarily an investigation of the gaseous pollutant emissions arising from concurrent combustion of biomass and municipal solid wastes materials, using a fluidized bed combustor. Of the wide range of biomass energy resources available, dried distillers’ grains with solubles and wheat straw were chosen as two example agricultural by-products of the human food supply chain. To consider an integrated waste management programme, a residual waste resource from a materials recycling facility was identified as a waste materials source that could be utilized after materials recycling was performed (which is a higher priority activity with respect to energy recovery). Cont/d.

Phosphorus is removed from wastewater streams to prevent the ecologically harmful effects of eutrophication in receiving natural systems. Current chemical and biological techniques for removing phosphorus from wastewater are not able to practicably achieve the new discharge limit expected under the Water Framework Directive of 0.1 mg phosphorus L- 1 . In addition, they do not represent an economically viable route for the recovery and reuse of the phosphorus they remove. Cont/d.

Concerns over possible waterborne disease forced drinking water supply companies in England and Wales to adopt microfiltration and ultrafiltration technologies rapidly. MF and UF membrane plants are designed to produce water of a consistent quality regardless of throughput and fluctuations in the feedwater quality. To operate well they need to maintain flux and balance the rate of fouling, and chemical cleaning performance is critical to this. Giant steps have been taken into characterizing the foulants scientifically in the last few years while cleaning is reactive and ad hoc. This thesis explores the basis for a corresponding cleaning science for the technology to develop quantitively. Cleaning performance was defined in terms of a response to combinations of explanatory variables in a materials limited cleaning envelope. The study focused on applying variations of cleanant concentration, applied temperature and soak times to a variety of membranes fouled with different waters and regimes. An experimental design was developed and applied consistently to a number of different sampled sites; allowing an optimised recovery from the polynomial expressions for each treatment, through factorial analysis of the data. The size and variety of the data set analysed allowed comparison and quantification of the different deviations from optimal cleaning response. This effect was seen to vary temporally and with operating regime and the methods usefulness as a practical tool in the membrane plant lifecycle was considered. Cost evaluation of the variation in cleaning response showed that sub-optimal cleaning costs and energy use may be significant and the thesis also illustrated how module geometry affects initial cake deposition and thus cleanability. By demonstrating the potential for cleaning factor analysis, the potential for a combined heuristic and predictive cleaning control science is possible, but will need new strategies to manage technology change.

The influence of swirler design parameters namely, vane shape (flat or curved), vane outlet angle, aspect ratio and space-to-chord ratio (number of vanes), on the pressure drop-mass flow characteristics and the size and turbulence characteristics of the downstream recirculation region has been determined experimentally. A five-hole spherical pressure probe and hot-wire anemometry have been used for the investigation. A technique for simple and reasonably accurate interpretation of the signals from the hot-wire anemometer has been formulated. Its performance has been tested at first in round jets for which experimental turbulence data are already available for comparison purposes. The method has been applied subsequently to swirling flows issuing from the swirlers; the mean and turbulence characteristics of the flow fields have been determined in this way. In addition to these, the turbulent viscosities μrr, μrz, μrθ and μθθ have been calculated. Also, detailed accounts of the previous experimental work on swirling flows and of some finite difference procedures for the computation of weakly and strongly swirling flows have been given. It has been shown that the hot-wire formulation developed provides a simple, economic and efficient procedure for the measurement of the turbulence quantities in swirling flows. The results have shown that curved vane type swirlers operate more efficiently than flat vane types such that a larger recirculation region and a stronger shear zone are induced at a lower pressure drop. The pressure drop through both the flat and curved vane type swirlers increases with increasing vane angle, decreasing aspect ratio and decreasing space-to-chord ratio. The size of the downstream recirculation region, the reverse mass flow and the decay rates of the axial and swirl velocities increase with increasing vane angle and decreasing aspect ratio in the case of curved vane type swirlers. The effect of the space-to-chord ratio has not been found very significant in the cases of I6 and I2 vanes for the vane angle of 60° and the aspect ratio 0.4. Higher turbulence and stronger shear zones can be obtained in swirling flows with increasing vane angle, decreasing aspect ratio and decreasing space-to-chord ratios. Turbulence is anisotropic in strongly swirling jets issuing from vane type swirlers. The most dominant stresses are in turn ww, uw, and uu; all the other stresses are smaller. In parallel to the anisotropy in the stresses, the turbulent viscosities are also anisotropic; the turbulent viscosity μθθ has shown domination among the four viscosities which have been calculated. μrr values have shown too much scatter. For these reasons, curved vane type swirlers should prove much more efficient than flat vane types in the application to combustion process.

The application of advanced technologies employing combustion/co-firing of coal and biomass is seen as a promising approach to minimising the environmental impact and reducing CO2 emissions of heat/power production. The existing uncertainties in the combustion behaviour of such fuel mixes and the release of alkali metals with other elements during the combustion (or co-firing) of many bio-fuels are some of the main issues that are hindering its application. The potential presence of high levels of alkali chlorides and low levels of sulfates in the deposits formed on heat exchanger can cause enhanced corrosion and/or limit the heat transfer between the hot combustion gases and the water/steam system within the process plant. This work has investigated the detailed gas compositions and deposition characteristics of the combusted gas streams produced from fossil and biomass fuels pure and/or blend in a pilot-scale combustors (PF and FBC) at Cranfield University. Combustion gas analysis were obtained on-line by a high resolution multi-component Fourier Transform Infra-Red (FTIR) gas analyser and deposits samples were collected from the flue gas using air-cooled probes with surface temperatures of about 500, 600, 700 o C and analysed using SEM-EDX and XRD techniques. Fuels included several biomass fuels (cereal co-product (CCP) straw, miscanthus (pulverised), oil seed rape straw (against stored pellets), miscanthus (pellets), willow, fast pyrolysis bio-oil) and two commercially-used coals (El-cerrejon and Daw Mill). The results of the experimental studies have been compared with thermodynamic equilibrium predictions. High combustion efficiency was maintained throughout the range of fuel mixes. The SO2 and HCl levels were low in pure biomass combustion and increased as the biomass fraction of the fuel decreased when co-fired with these coals. However, the NOx output remained stable except for Miscanthus:Daw Mill mixtures and OSR stored pellet combustion. The deposition flux was highest on the coolest probes for each fuel. The lowest deposition fluxes were found for the combustion of either fast pyrolysis bio-oil or coppiced willow. There is evidence of significant differences deposition fluxes between El-cerrejon coal and Daw Mill coal mixed with CCP and/or miscanthus. The presence of chlorine was identified in deposits produced from combustion of pure biomass or high biomass mixes. The lowest levels found here in fast pyrolysis bio-oil combustion and only detected at higher shares (≥ 80 %) of biomass co-fired with Daw Mill coal, whereas, mixed biomass with El-cerrejon coal produced Cl in deposits at a low % biomass share. The application of thermodynamic equilibrium modelling has been found to be useful tool for providing a qualitative understanding of elements present and/or control by hot gas in modern combustion processes.

The inevitable growth of air traffic resulting from the increasing demands on utilization of the aircraft for various purposes has introduced public awareness and concern about the contribution of air traffic towards climate change. The increase of aircraft emissions enhancing the greenhouse effect and decreasing the air quality in general, is no longer considered sustainable and steps are being taken towards the mitigation of this problem. Although a significant research activity takes place in the development of new technologies, the most readily available solution to this problem is seen in applying changes to aircraft operational rules and procedures and in optimizing the flight paths using the aircraft currently in service. The helicopter, although comprising a significantly smaller portion of the aircraft market in comparison with the fixed-winged aircraft, is experiencing the same concerns with respect to the amount of gaseous emissions produced. The helicopter plays a specific and irreplaceable role in the air transportation and it is often being used for purposes where the environmental concerns are secondary (such as during medical rescue operations or during police missions). It is however being increasingly employed for non-urgent operations, such as executive business travel or for the transportation of personnel to and from oil rigs. In all cases, the most readily available solution (and also perhaps the least costly) to lowering the gaseous emissions is to evaluate the helicopter engine performance along a given flight path using a computer program in order to investigate the effect on fuel burn and gaseous emissions. Cont/d.

No description available.

Decision support systems (DSS) have been widely advocated as key tools for the integrated management of water resources, which emerged as a critical need for addressing the various technical, economic, social, environmental and politicoinstitutional challenges facing the management of water resources. This thesis aims at developing a framework for assessing the validity of DSS in application to water resources management, more particularly reviewing Multi-Criteria Analysis (MCA) and Cost-Benefit Analysis (CBA) as a basis for decision-making. This is critical at times of increasing demand for tools such as DSS, and therefore the increasing importance of overcoming a major DSS limitation, which is validity. The proposed framework consists of two complementary approaches: (1) assessing intra-model validity (MCA), an approach which consists of studying the level of confidence in the comprehensiveness of management options (MO) and basic indicators (BI), analysing uncertainty in the performance values and weights assigned to BI, undertaking a sensitivity analysis of MO ranking to BI performance values and weights, and, based on results, generating as well as evaluating strategy alternatives; (2) assessing DSS inter-model validity, an approach which consists of comparing models (MCA and CBA). The application of the framework to the Sustainable Management of the West Bank Aquifer (SUSMAQ) generates results very much consistent with literature findings: importance of sensitivity analysis as a practical alternative to uncertainty analysis, sensitivity of MO ranking to BI performance values more than to BI weights, importance of accounting for indirect benefits and for the choice of discount rate in CBA, complementarity if not equivalence of MCA and CBA, etc. Although the aim of the thesis is methodological, the application uses validity assessment results to test various strategies for the management of water resources in the West Bank, as an illustrative example only.

A study was undertaken on the Bowden Close (BCl) Passive mine water Treatment System (PTS). BCl consists of two parallel working Reducing and Alkalinity Producing Systems (RAPS, reactive substrate = limestone, compost, manure) that are followed by a polishing wetland. Thereafter, the water is discharged into a local burn. The main purpose of the PTS is to decrease metal concentrations (Fe (≤177mgL-1), Al (≤85mgL-1), Zn (≤2.8mgL-1), Mn (≤20.5mgL-1)) and increase alkalinity (≥0mg L-1 CaCO3 eq) and pH (≥3.2) in two coal mine drainages. The aim of this study was to assess the treatment performance and the dominant (bio)geochemical processes promoting metal removal and alkalinity generation, particularly in the RAPS. Over nearly six years of operation, BCl performed well with regards to the removal of iron (-84%) and aluminium (-87%) and the generation of alkalinity (+74%). Zinc (-51%), manganese (-23%) and sulfate (-29%) were partially removed. The effluent pH was raised to ~6.9. However, a long-term decrease in alkalinity generation has been observed, which could threaten the treatment performance over the short term and might eventually lead to metal remobilization. Against expectations, Bacterial Sulfate Reduction (BSR) is not a driving process in the removal of the main contaminant, iron. Only ~5% of iron was removed as di-sulfide mineral (i.e. pyrite). Rather, removal processes such as observed in aerobic treatment systems predominate (i.e. retention in (hydr)oxides). It is suggested, that the reoxidation of hydrogen sulfide by Fe(III)hydroxides is limiting the generation of mineral sulfides. Carbon isotope ratios of total dissolved inorganic carbon indicate that anaerobic microbial respiration, including BSR, has considerable influence on the generation of alkalinity. Two mass balances suggest, that more than 52% of bicarbonate generated by the RAPS derives from the oxidation of organic matter, thereby safeguarding the limestone in the reactive substrate and increasing the overall lifetime of the RAPS. Analyses of sulfur and oxygen isotope ratios of dissolved sulfate and sulfide, together with solid phase sulfur and water isotopes suggested: i) mine waters are of meteoric origin, ii) and have one single sulfate sulfur source (potentially oxidation of coal derived iron sulfide), iii) sulfide oxidation in the mine waters is dominated by anaerobic oxidation, iv) in both RAPS, BSR is occurring year round, v) sulfate concentrations might be limiting BSR in RAPS 1 during the summer months and vi) pyrite seemed to form via the hydrogen sulfide pathway without solid phase iron mono-sulfide intermediate. Overall, sulfur and oxygen isotope fractionation suggest that BSR kinetics are slow and bi-directional. Detailed studies, including the microbial ecology in the RAPS are proposed to enhance understanding about the functioning of the system. Key words: coal mine drainage, microbial sulfate reduction, alkalinity generation, isotopes