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The following EngD thesis presents research on the potential for short term deployment of carbon dioxide utilisation technologies within the context of the European steel industry, in collaboration with Tata Steel Europe. The aim of the project was to identify options for short term utilisation of CO2 directly from steelmaking process exhausts and then evaluate them in terms of their technical feasibility, CO2 reduction potential and economic sustainability. An initial review of steel production processes and CDU routes resulted in the selection of two potentially promising processes for further investigation; production of precipitated calcium carbonate (PCC) from steelmaking wastes, and combined biomass production and steelmaking wastewater remediation using microalgae. Each technology was investigated experimentally to determine its technical feasibility, and then via a techno-economic evaluation in order to estimate the scale of potential CO2 mitigation and economic viability. Although both technologies were deemed to be technically feasible, when techno-economic evaluations were performed it became clear that neither technology is likely to be able to achieve significant CO2 emissions reductions (reduction is limited to less than 1% of typical integrated site emissions). Despite this, economic estimates for a scaled up PCC production process were promising; a moderate payback on capital expenditure of around 5.51 years was estimated under baseline conditions, with a significant additional revenue potential if the process were credited under the European Union Emissions Trading Scheme. In contrast, the microalgae based process was found to be highly uneconomical when using technology which is currently available at a commercial scale, and the CO2 mitigation potential was determined to be limited by the indirect CO2 emissions from very high electricity demands as the process is scaled up.

A global legacy of radioactively contaminated land exists as a result of nuclear fuel cycle operations. Demonstration of the safe management of the UK nuclear legacy, including contaminated land, is important whilst the long term fate of legacy waste remains uncertain and the UK is moves towards new nuclear power. One aspect of nuclear contaminated land research focuses on the immobilisation of intermediate and long lived radionuclides that are mobile in groundwater and are migrating in the environment. At Sellafield nuclear facility, UK, strontium-90 and technetium-99 are found as co-contaminants in groundwater alongside the most abundant non radioactive contaminant, nitrate. Their differing radiochemical behaviour and the presence of nitrate presents a challenge for remediation strategies. Bioremediation has the potential for in-situ immobilization of 99Tc via reduction from mobile Tc(VII) to less mobile Tc(IV) concurrent with Fe(III) reduction. In this project bioreduction processes were investigated in sediment microcosms and model systems under variable pH and nitrate conditions and using microorganisms representative of the Sellafield site. Sediment bioreduction occurred via stimulation of the natural microbial community. Denitrification resulted a delay in the onset of metal reduction followed by a raised pH. At the mildly acidic pH of the natural sediments, a nitrate concentration of 100 mM caused bioreduction to stall. However, at pH 7, reduction of 100 mM nitrate resulted in a final pH > 9 and alkaline Fe(III) reduction. In bioreduced sediments, the microbial ecology was dominated by nitrate reducing microorganisms and Fe(III) reducing enrichment cultures were necessary to identify relevant alkaline Fe(III) reducing bacteria. Enrichment cultures isolated a novel alkali tolerant Fe(III) reducing Serratia sp. with a growth range of pH 4 to 9. Increased pH resulting from denitrification decreased the mobility of Sr2+ via increased sorption to mineral surfaces. X-ray absorption spectroscopy confirmed Sr2+ incorporation into carbonate mineral phases above pH 8.5. Model systems showed reductive removal of 99Tc from solution by an Fe(II) bearing mineral assemblage at both pH 7 and 9. In contrast Sr2+ remained in solution at pH 7 and precipitated as SrCO3 at pH > 8.5. This study for the first time demonstrates the effects of high nitrate on pH in Sellafield type sediments, alkaline Fe(III) reduction by a Serratia sp, the incorporation behaviour of Sr2+ during sediment bioreduction and the behaviour of Sr2+ and 99Tc in novel Fe(II) mineral bearing model systems. These findings improve the understanding of radionuclide migration at contaminated sites and inform possible engineered bioremediation scenarios.

With a rising demand for nanomaterials and their continual increase in production, the release of nanoparticles (NPs) into the environment is inevitable (Petosa et al., 2010). Problematically, NPs can have a wide range of toxic effects, which are exacerbated by their size (at least one dimension smaller than 100 nm)(Engineering., 2004). Detrimental effects include brain, intestinal and respiratory injury, delayed embryonic development, DNA damage which ultimately lead to increased mortality (Trouiller et al., 2009), (Handy et al., 2008). Natural and manufactured NPs also have the ability to bind and transport chemical pollutants, thus enhancing their toxicity (Moore, 2006). While an array of techniques are available for in situ remediation of numerous groundwater contaminants, there are currently none for in situ remediation of nanoparticles. This fundamental technology gap means we are poorly prepared to deal with nanoparticle pollution events. The aim of this PhD was to develop mechanisms to immobilise and remove nanoparticles from water and waste water in order to prevent the transport of nanoparticles to sites where they have the potential to cause harm. Experiments conducted demonstrate the potential of microbially mediated mineral formation to immobilise nanoparticles from water. The ureolytic bacteria Sporosarcina pasteurii was used to induce calcium carbonate precipitation in batch and column experiments. Nanoparticle immobilisation was tested as a function of nanoparticle size and surface charge. The results demonstrate the successful immobilisation of negatively charged nanoparticles (both large and small, 150 and 35 nm respectively), while failing to remove positively charged nanoparticles from solution. In order to capture positively charged nanoparticles a second mineral, struvite, was tested. The precipitation of struvite successfully immobilised positively charged nanoparticles. However, in comparison to the calcite precipitation experiments the removal of positively charged nanoparticles was found to be pH and ionic strength dependant. Finally, the ability of Bacillus subtilis, a common groundwater bacterium and wastewater treatment biofilm to adsorb and remove nanoparticles from solution was examined. Here both biosorbent materials were highly efficient at removing positively charged nanoparticles from solution whilst negatively charged nanoparticles remained in suspension. The research presented here demonstrates that microbially induced mineral precipitation may be used as a tool to immobilise nanoparticles from contaminated groundwater. In addition, bacteria and wastewater treatment biofilm were found to be highly efficient biosorbents of positively charged nanoparticles. These findings hold implications for the fate and transport of nanoparticles through environmental systems and wastewater treatment plants.

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Carbon Capture and Storage (CCS) is a legitimate technology option that should be part of a balanced portfolio of mitigation technologies available Post-Kyoto Protocol framework after Paris 2015 and beyond the 2020s or the cost achieving 2 degrees Celsius stabilisation scenario will significantly increase. Oxy-fuel combustion as a CCS technology option increases fuel flexibility. Additionally, oxy-biomass as a bio-energy with CCS (BECCS) technology can achieve negative carbon dioxide (CO2) emissions in sustainable biomass systems. Also, oxygen (O2) production in an air separation unit (ASU) gives potential for extra operational flexibility and energy storage. In this work, new designs of 20 litre spherical (R-20) and 30 litre non-spherical (R-30) ignition chambers have been built at the University of Edinburgh to carry-out dust ignition experiments with different ignition energies for evaluating pulverised fuel ignitability as a function of primary recycle (PR) O2 content for oxy-fuel PF milling safety. A set of coals and biomasses being used (at the time of submitting this work) in the utility pulverised fuel boilers in the UK have been employed. Coal and biomass dusts were ignited in air and oxy-fuel mixtures up to 30 % v/v O2 balance mixture CO2 where peak pressures (Pmax) from ignition were recorded. Pressure ratios (Pmax/Pinitial) were determined the key parameter for positive ignition identification with a value above 2.5 to be considered positive. Particle size effects in coal and biomass ignition were evaluated. Results on biomass were more variable than with coals, requiring a stronger ignition source (5,000 J) mainly due to larger particle sizes. Finer biomass particles behaved similarly to air ignition in 25 % v/v O2 in CO2. Larger particles of biomass did not ignite at all for most cases even reaching 30 % v/v O2 in CO2. A reference coal used, El Cerrejon, behaved as expected with 30 % v/v O2 balance CO2 matching air case; particles between 75-53 microns had lower ignitability than finer below 53 microns but were critical in devolatilisation. Most fuels did not ignite in 21 % v/v in CO2 below 200 g/m3 concentrations. The use of adequate ignition energy strength is needed for the PF mill safety case, with 5,000 J energy required for the biomasses tested. An indication of potential ignition chamber volume and geometry effect has also been observed when comparing results from R-20 and R-30 ignition chambers. Important implications include that oxy-biomass PR with 21 % v/v O2 content would give improved pulverised fuel (PF) milling safety when compared to air firing but reduced ignitability and a 25 % v/v O2 balance CO2 atmosphere would approach to oxy-biomass ignition behaviour in air in mills.

Due to increasing awareness of potential Cr toxicity, there is a pressing need to establish sensitive and robust Cr fractionation and speciation methodologies that will be enable separation of the two redox Cr species (CrIII and CrVI) from different environmental phases and their quantification. The intention of this work was to assess the behaviour of Cr species, especially CrVI, in soils and the factors controlling Cr solubility, fractionation, redox transformation rates and uptake by plants. The analysis methods relied on alkaline extraction in TMAH, liquid chromatography (LC) to separate the chromium species and inductively couple plasma mass spectrometry (ICP-MS) for quantification of chromium. The interference of 40Ar12C+ background peak at mass 52 was reduced by using the CCT-KED facility of the ICP-MS. A solution of 50 mM TRIS buffer, 40 mM NH4NO3, 10-5 M ammonium-EDTA at pH 7.0 was used as the chromatographic eluent. The method developed is suitable for determining CrVI in soil, following alkaline extraction in TMAH, but not for CrIII due to poor recovery, redox transformation and strong binding of CrIII with humic acid despite attempts to preserve the trivalent species using EDTA and heating. The extraction method was applied to assessing Cr speciation and fractionation in a wide range of soil ecosystems collected from urban sites in Wolverhampton, Nottingham, London and a historical sewage sludge disposal farm in Nottinghamshire. To predict soil CrVI content the use of TMAH-extractable Cr (CrTMAH) was better (R=0.911) compared to total soil Cr content (Crtotal; R=0.554). The same analytical approaches were also applied to the development of a method to determine isotopically exchangeable CrVI in soils. This employed isotopically enriched 50CrVI as a ‘spike’ isotope added to soils suspended in varying concentrations of TMAH in an attempt to resolve a consistent fraction of isotopically exchangeable, or ‘labile’, CrVIO42- in soil. It was apparent that, because of the slow exchange kinetics of CrVI in soils, it was difficult to determine a consistent isotopically exchangeable fraction. Nevertheless, the investigation did suggest a refinement of the simple TMAH extraction protocol could enable direct determination of labile soil CrVI. The kinetics of CrVI interaction with a geocolloid (humic acid) was assessed and humic acid was found capable of both reducing CrVI and binding with the resulting CrIII species. Finally, Cr uptake by maize grown on a historical sewage sludge disposal farm was assessed with several approaches to finding a correlation between Cr in soil and Cr uptake by plants. The concentration of CrVI in soil, and its solubility, could be reasonably well predicted from Crtotal or CrTMAH and soil properties. However, restricted uptake of CrVI by the maize plants, and probably reduction of CrVI to CrIII in the root system, made it impossible to predict Cr transfer to shoots or the speciation of the Cr in maize shoots. Overall, due mainly to the apparent ability of the maize plants to control uptake and speciation of CrVI, the produce was considered safe to be consumed by ruminants as regards CrVI content.

This thesis describes a study of the distribution and behaviour of natural and manmade radionuclides in the intertidal environment of south west Scotland. This work is particularly concerned with transport processes affecting radionuclides and with the application of radionuclides as tracers of natural environmental processes. Results are presented for study sites at Ardmore Bay in the Clyde Sea Area and Skyreburn Bay, Wigtown Martyr's Stake and Netherclifton in the Solway Firth with the radionuclides investigated being 134Cs, 137Cs, 210Pb, 238Pu, 239. 240Pu 241 Am, 238U, 232Th and 230Th. The study confirms and extends an existing model for particle associated Sellafield waste radionuclide transport to the intertidal areas of the Solway Firth and the work, moreover, establishes that the same supply mechanism operates in the floodplain, or merse, areas of the Solway Firth. Inventories of the order of 10e5, 10e4 and 10e4 Bq m -2 are derived for 137Cs, 241Am and 239,240 Pu respectively in the merse sediments, indicating inventories for these nuclides of the order of 7, 1 and 1 TBq in the total area of the merse deposits of the Solway Firth. A description is provided of a study of uranium movement through the Solway floodplain silts in the vicinity of a uranium mineralization vein and it is established that uranium migration for distances of up to 55m can be observed with continuous removal from solution during transport by uptake by iron/manganese oxides and organic materials. The removal process is characterised by a 10m halving distance. The radionuclide data are considered in the context of tracer studies of various environmental processes including large scale sediment movement in the Irish Sea, local sediment movement in particular bays and, at individual sites, mixing and accumulating processes.