Bioclogging can be defined as the reduction of hydraulic conductivity and porosity of a saturated porous medium due to microbial growth. Wastewater disposals, artificial groundwater recharge, in-situ bioremediation of contaminated aquifers, construction of water reservoirs, or secondary oil recovery are all affected by this process. The potential for soil and groundwater contamination may increase by the rapid movement of the solutes through soil due to the presence of preferential flow which resulted in increasing bypassing of soil matrix and increasing pore water velocities. On the other hand the presence of preferential flow could affect the clean-up process of the contaminated land by extending the remedial time. The reason behind that is the relatively quick contaminant clean-up in the high permeable zones compared to the slow contaminant clean-up in the low permeable layers. Therefore, this study aims to investigate the bioclogging process in porous media and the factors that can affect this process, also to understand how all aspects of flow are affected by the clogging process, and finally to investigate the potential of biological growth to control direction and location of subsurface hydraulic flow to overcome the problems of preferential flow. The bioclogging process was investigated through a series of sand column experiments in homogeneous and heterogeneous porous media. Six sand fractions ranging from 63-1180 μm were selected as a porous media. Two bacterial strains (P. putida mt-2 and B. indica) were used in this study. Different analytical methods such as loss on ignition and the total number of cells were used to analyse the soil samples. iv The outcomes of this study showed that the growth of bacteria in porous media can reduce the heterogeneity of the porous media, thereby reducing the impact of the preferential flow which could affect the clean-up process of the contaminated land. Pore throat model with the incorporation of different bioclogging models such as the biofilm or plugs (Vandevivere et al., 1995), micro-colony (Okubo and Matsumoto, 1979), and macroscopic (Clement et al., 1996) models were applied to evaluate the results of the experimental work in heterogeneous porous media. The changes in hydraulic conductivity and the porosity of porous media were modelled by assuming that the bioclogging occurs in the small pores which connect the large pores of the porous media. Generally amongst the three bioclogging models, the current study showed that the measured values of the hydraulic conductivity relatively coincide with the predicted values obtained by using Vandevivere et al. (1995) model. Nevertheless, the predicted values of the hydraulic conductivity coincided to some extent with the measured values of the hydraulic conductivity for the large sand fractions. This corresponds with the findings of several previous studies which also confirmed that bioclogging models can only predict the change of the hydraulic conductivity for the large sand fractions. The failure of these models could be related to the assumptions made by each model, which could be less appropriate in fine-textured materials than they are in coarse textured ones. The second possible reason for the disparities between observations and model predictions is related to the assumption made in some of these models that the microorganisms which are responsible for clogging form biofilms of constant thickness which uniformly coated the surface of soil particles.

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.

Amine functionalised silica adsorbents are promising materials for post combustion carbon capture. They exhibit high CO2 equilibrium adsorption capacities and selectively adsorb CO2 in the presence of water. A practical method of regenerating these materials in fossil fuel power stations is to utilise steam regeneration. There is a lack of understanding of the long term stability of amine functionalised silica in the presence of steam. This thesis explored the deactivation mechanism of impregnated and covalently tethered amine adsorbents under steam regeneration and humid adsorption conditions. The adsorbents were characterised using organic analysis and nitrogen sorption before and after aging. The effect of steam regeneration aging led to a significant decrease in the CO2 adsorption uptakes of the adsorbents. Impregnated amine adsorbents were deactivated by leaching of the impregnated amine component from the largest pores of the support. Steam aging also led to diminished amine accessibility caused by amine polymer agglomerating within pores below 8 nm. To address this issue of instability in the presence of steam amine impregnated silica adsorbents were post functionalised with organosilanes. Under certain conditions this silane functionalisation was shown to selectivity occur at the exterior and pore mouths of the adsorbent. The presence of silane coatings preserved the CO2 adsorption capacities of the adsorbents after aging. A compromise exists between adsorbent stability and CO2 uptake behaviour as silane functionalisation led to a reduction in the CO2 uptake capacity. Post functionalisation of amine impregnated silica with hydrophobic silanes limits the intrusion of water within the pores of the adsorbent. This reduction in water intrusion limits the rate of solubilisation of the amine polymer, thus preventing leaching. The impregnation of amine polymers onto porous silica supports typically leads to agglomerations and significant pore blocking. This limits the rate of adsorption and uptake capacity of the adsorbents. The introduction of aminesurfactant mixtures into the adsorbent was found to increase accessibility of the adsorption sites leading to enhanced rates of adsorption and CO2 equilibrium uptakes. The addition of surfactants also yielded a reduction in the regeneration requirements of the adsorbents, by the formation of favourable thin films of amine within the pores of the adsorbent.

The objective of this study is to promote photocatalytic wastewater treatment by proposing a reactor design that employs a catalyst-coated, rotating, corrugated drum to increase the surface area, induce agitation and promote reactant and photon transfer to the surface. Corrugation profiles with surface areas ranging from 405 cm2 to 3650 cm2 were considered---the addition of corrugations improved the phenol degradation rate by up to 200%. Based on an analysis of rotational speed and initial pollutant concentration, the reaction was found to be limited by the kinetics at 20 ppm and 40 ppm, but limited by phenol transfer to the reaction sites at 5 ppm. Finally, Langmuir-Hinshelwood kinetics was applicable with an average phenol adsorption coefficient of 0.120 L/mg and an increasing overall reaction rate constant with surface area. Further studies are necessary for the industrial use of such a reactor design including treatment of wastewater with varying characteristics, reactor design scaling and the applicability of this design for solar-activated applications.

Dissolved organic carbon (DOC) is a complex, yet major component of leachate and groundwater contamination derived from municipal solid waste burial. Here I use a new analytical technique for the analysis of 13C in specific compounds of DOC in leachate from the Trail Road Landfill (TRL) site, Ottawa, Ontario, in order to better characterize its biogeochemical and isotopic evolution during degradation; to determine methanogenesis pathways; and to identify characteristic tracers for recognizing potential of the leachate impact on the surrounding groundwater. This new operational system measures chromatographically-separated DOC compounds, and DOC compounds separated by DAX-8-resin, with a total inorganic/organic carbon analyzer (TCA) interfaced with a Thermo-Finnigan DeltaPlus continuous-flow isotope ratio mass spectrometer (CF-IRMS). At the TRL site, with capacity of 8.8 million cubic meters and a footprint of approximately 65 hectares, waste emplacement has been undertaken in four stages since the 1980s. Samples were collected in 2003 through 2005 from the leachate pumping station (LPS), which drains the areas of youngest waste, from monitoring well M32, situated at the base of the earliest stage and from leachate from waste up to 28 years old, and from several nested multilevel monitoring wells situated in the periphery of the landfill site. The following results were obtained based on isotope analysis of leachate, of landfill gases, of various leachate DOC components, and of contaminated groundwater. Leachate as a source of contamination has been characterized at different parts of the landfill as follows: (1) Elevated DOC and enriched 13CDOC values in old leachate from the older landfill (M32) (4770 mgl-1 and -21.6 ‰) in comparison with that of the younger leachate (LPS) (197 mgl-1 and -25.7 ‰) shows a fundamentally different biodegradation pathway and more advanced microbial processes in the degradation of dissolved organic mater (DOM) in the older part of the landfill. This resulted in the accumulation of simple fatty acids (acetate and propionate concentration of 1008 mgl-1 and 608 mgl-1, respectively) at the older part of the landfill with more enriched 13C values of acetic acid (-12.0 ‰) in comparison to that of young leachate at LPS (-16.9 ‰). (2) Deuterium excess provides a robust indicator of overall methane production, showing greater CH4 production in the younger parts of landfill than the older parts. The CO2 reduction pathway (alpha13C CO2-CH4=1.06) dominants at the younger landfill, however, acetate fermentation is the more favored CH4 production pathway at the older landfill. This can be confirmed with the less enriched 13CDIC (8.5 ‰) and a lower value for 2H excess (9.8 ‰) at M32. (3) The higher ratio of humic/fulvic acids (HA/FA) in young leachate compared to the old leachate (0.18 and 0.05 for LPS and M32, respectively) is due to high concentrations of FA (4482 mgl-1, 73% of the total DOC) and low concentrations of HA (21 mgl-1, 0.3% of the total DOC) in old M32 leachate. Less aromatic carbon in M32 (3% and 5% for POC and HA, respectively) in comparison with that of young leachate from the LPS (10% and 28% for POC and HA, respectively), estimated from 13C-NMR spectra, is perhaps due to degradation of HA and transforming of aromatic carbon to low molecule weight dissolved organic carbon (LMW-DOC), which is consistent with the high concentration of acetic acid (AA) in this older leachate. Although the elevated concentrations of leachate indicator parameters (like Cl and DOC) indicate that both shallow and deep aquifers have been contaminated at the TRL site, assessing the impact of landfill leachate on local groundwaters using geochemical parameters is often confounded by naturally elevated concentrations of these indicators. Here, environmental isotopes are used to provide a constraint in this assessment for leachate derived from the TRL site. The carbon geochemistry of different carbon pools (DIC, DOC, CH4, CH3COOH, humic substances (HS), particulate organic carbon (POC), particulate inorganic carbon (PIC)) and delta13C were used to recognize leachate impact on the surrounding groundwater. (Abstract shortened by UMI.)

The biodegradation of municipal solid waste (MSW) was investigated in simulated bioreactor landfills under aerobic and anaerobic conditions. The bioreactors were operated to determine the amount of leachate recirculation and municipal wastewater sludge addition to optimize waste degradation. The leachate generated was recycled over 47 and 63 weeks for aerobic and anaerobic bioreactors, respectively. Leachate samples were collected on a weekly basis and analyzed for pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3-N), total phosporus, and metals. The temperature of the MSW in the bioreactors was measured on a daily basis. In addition, the generation of biogas was monitored in the anaerobic bioreactors during the operating period. The leachate generated was recirculated at the rates of 285 to 855 mL/kg of MSW.d (5 to 15 L/wk) and sludge was added at the rates of 28.5 to 85.5 mL/kg of MSW.d (0.5 to 1.5 L/wk). Within 27 and 39 weeks enhanced MSW degradation in the aerobic and anaerobic bioreactors were observed at a leachate recirculation rate of 855 mL/kg of MSW.d and sludge addition rate of 85.5 mL/kg of MSW.d. During this period, the COD concentration in the leachate dropped from 38,000 mg/L for aerobic and 47,000 mg/L for anaerobic to approximately 1000 mg/L. This is an indication that the aerobic biodegradation is 1.5-fold faster compared to the biodegradation under anaerobic operation. A reduction in the leachate recirculation and sludge addition rate to 285 and 28.5 mL/kg of MSW.d respectively, increased the waste stabilization period up to 45 and 63 weeks for aerobic and anaerobic bioreactors, respectively. The statistical empirical models based on two levels factorial design were used to describe the effects of leachate recirculation, sludge addition and their combination on biodegradation of the waste. For both aerobic and anaerobic bioreactors the values of estimate parameter beta1 were higher compared to beta2 and beta12. This indicated that the effect of leachate recirculation was much stronger compared to the effect of sludge addition and their combination on biodegradation of the waste. A statistic procedure, F-test and ANOVA-test were used to determine whether or not there is a significant difference between the aerobic and anaerobic biodegradation. The result of the paired F-test show that F calculation was 270.85 and F critical was 160 at a 95% confidence level. This confirms that there was a significant difference between the aerobic and anaerobic biodegradation. In addition, the ANOVA test show that effect of air flow addition on the MSW biodegradation was very significant. The results of these tests indicated that the addition of air affected positively the biological activities and consequently enhanced the MSW biodegradation process. A fuzzy logic model, describing the dynamics of the biodegradation and stabilization process during the experiment, was developed to simulate the effect of leachate recirculation and sludge addition on MSW biodegradation in landfills. The model was based on the COD concentration of the leachate, temperature of the MSW in the bioreactors, and biogas production from anaerobic bioreactors. Subsequently, the model was evaluated by comparing the simulation with the experimental results. The model shows that the higher rate of leachate recirculation and sludge addition, the faster biodegradation of MSW. In addition, the model could be used to predict the rate of MSW biodegradation under various operating conditions.

The discharge of a landfill leachate to a receiving water body can cause a serious pollution problem. One component of leachate that can have a severe impact on a receiving water body is ammonia and its oxidized form, nitrate. This study investigated the biological treatibility of a high ammonia leachate, with specific regard to nitriification and denitrification. A continuous-feed, single sludge denitrification system with recycle was used. Leachate ammonia concentrations of up to 288 mg/L-N were reduced to less than 1 mg/L. The ammonia was removed by nitrification and bacterial uptake. About 25% of the incoming ammonia was taken up by the bacteria in the anoxic reactor; the rest was subsequently nitrified in the aerobic reactor. The nitrates produced in the aerobic reactor were recycled back to the anoxic reactor to undergo denitrification. Glucose was added directly to the anoxic reactor to aid denitrification. The degree of denitrification was dependent on the glucose loading to the anoxic reactor; however, 100% denitrification was achieved on several occasions. The influent leachate COD removal was 20%; however after the addition of glucose to the system, a mean COD removal of 74% was obtained. Of the COD removed across the system, 85% was used in the anoxic reactor for denitrification, and the remaining 15% was used by the heterotrophs in the aerobic reactor. The four metals monitored regularly, zinc, manganese, nickel and iron were removed by the biomass, but not to the same extent During the latter part of the study, the system was first spiked with manganese, and then - zinc, to try and induce an inhibitory effect on the nitrification process. The manganese had no detectable effect on the system. However, total zinc (>95% soluble) levels of between 14.9 and 17.6 mg/L caused substantial inhibition of the nitrification process, resulting in approximately 70 mg/L ammonia in the effluent (feed = 216 mg/L). This inhibition was also evident from the lower percent nitrification values and the unit nitrification rates. This high influent zinc concentration also caused deflocculation, resulting in the loss of significant quantities of biomass with the effluent. The high zinc concentrations also inhibited the denitrifiers, resulting in a decrease in the ammonia uptake, as well as an increase in the COD (used)/Nitrate+Nitrite (NOT) (reduced) ratios in the anoxic reactor. The zinc levels were then lowered to allow the system to return to normal; after this state had been reached, the influent total zinc (>95% soluble) levels were again increased up to 19.5 mg/L. This concentration of zinc did not result in any ammonia appearing in the effluent; thus, it is possible that the bacteria had acclimatized to these high influent zinc concentrations. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1906 (first author), and Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Civil and Sanitary Engineering, 1906 (second author). / by Norman P. Gerhard and Charles F. Breitzke. / B.S.

No description available.