Historically, air and water have been considered common property resources and, therefore, over utilized as waste receptors. Dairy waste is a leading environmental concern in the North Bosque River watershed in Texas. Changing societal attitudes are forcing dairies and policymakers to balance environmental concerns with farm profitability. Dairies are entering a realm filled with technologies to combat waste concerns. Anaerobic digester technology may play a role in helping dairies balance profit and the environment. Digesters capture methane from livestock waste and transform it into electricity which can be sold to utilities or used on-farm. Because a digester facility is confined, air and water pollution can be reduced. Technological advancement and institutional factor changes allowing the sale of on-farm produced electricity and green power requirements have increased the economic feasibility of digesters. The study of the economic implications of anaerobic digesters for Texas dairies provides producers and policymakers with information to make good decisions concerning adoption and subsidization of this technology. At the beginning of this study, no digesters were operating in Texas. Dairies operating digesters in four states, therefore, were interviewed on-site to provide necessary data. The expected net present value, E(NPV), of a plug-flow digester is negative with and without selling electricity, indicating it should not be constructed based strictly on its financial contribution. At the current electricity-selling price, digesters are less economically feasible than current waste management strategies, lagoons, even after considering potential environmental penalties. However, selling electricity and capturing by-product heat for cost savings makes the digester's E(NPV) less negative than lagoons. The E(NPV) of a covered lagoon digester is positive. This indicates digesters are a potentially feasible waste management strategy. For plug-flow digesters to show a positive E(NPV), the selling price needs to be approximately 82.38% higher than the current price. The breakeven selling price is 12% higher than the current price. Below the breakeven price, lagoons have a larger E(NPV) than plug-flow digesters, therefore making lagoons the preferred waste management strategy. Results suggest changes in rules and technology efficiency make digesters economically competitive with current waste management systems.

Anaerobic digester (AD) technology is a form of renewable energy that’s economic feasibility assessment is required site by site. This thesis presents a freely available workbook to determine the financial feasibility of a farm-based AD and to demonstrate its use for the Ontario livestock sector. To assess the profitability of ADs for farmers in Ontario with uncertainty included the theory of real options is used. Investment in an AD is financially feasible only for the largest dairy farms in Ontario under current electricity prices, which are approximately six times greater than the wholesale price. Shifting to a duel fuel continuous system would improve returns, as would the availability of additional substrate material in the form of solid grease waste. The real options approach shows that even higher net returns are necessary, than indicated by more traditional approaches, in order for AD investments to be feasible for Ontario livestock farmers.

This thesis is comprised of two phases; the first phase concerns the effect of arsenic on the denitrification process in the presence of naturally-produced volatile fatty acids (VFAs); while the second phase evaluates the arsenic removal efficiency of New Zealand Iron Sand (NZIS) by adsorption. To accomplish the first phase of the study, VFAs were first produced naturally in an acid-phase anaerobic digester by using commercially-available soy flour. Secondly, a denitrifying biomass was cultivated in a sequencing batch reactor (SBR) using domestic wastewater as a feed solution. Finally, a series of biological denitrification batch tests were conducted in the presence of different concentrations of arsenic and nitrate. As mentioned, the VFAs were generated from an anaerobic digester using 40 g/L soy solution as a synthetic feed. The digester was operated at a solids retention time (SRT) and hydraulic retention time (HRT) of 10 days. The pH of the digester was measured to be 4.7 to 4.9 while the mean temperature was 31 ± 4 °C; however, both these parameters were not controlled. In the effluent of the digester, a mean VFA concentration of 5,997 ± 538 mg/L as acetic acid was achieved with acid speciation results of acetic (33 %), propionic (29 %), butyric (21 %), iso-valeric (5%) and n-valeric acid (12 %). The specific VFA production rate was estimated to be 0.028 mg VFA as acetic acid/mg VSS per day. The effluent sCOD was measured to be 14,800 mg/L (27.9 % of the total COD), as compared to 9,450 mg/L (16.8 % of total COD) in the influent of the digester. Thus, the COD solubilization increased by 11.1 % during digestion yielding a specific COD solubilization rate of 0.025 mg sCOD/mg VSS per day. The extent of the digestion process converting the substrate from particulate to soluble form was also evaluated via the specific TOC solubilization rate (0.008 mg TOC/mg VSS per day), and VSS reduction percentage (17.7 ± 1.8 %). A denitrifying biomass was developed successfully in an SBR fed with domestic sewage (100 % denitrification was achieved for the influent concentration of sCOD = 285 ± 45 mg/L and NH₄⁺-N = 32.5 ± 3.5 mg/L). A mean mixed liquor suspended solids (MLSS) of 3,007 ± 724 mg/L and a mean SRT of 20.7 ± 4.4 days were measured during the period of the research. The settleability of the SBR sludge was excellent evidenced by a low sludge volume index (SVI) measured to be between 50-120 mL/g (with a mean value of 87 ± 33 mL/g) resulting in a very low effluent solids concentration (in many cases less than 20 mg/L). Several preliminary tests were conducted to estimate the right dosage of VFAs (digester effluent), nitrates and arsenic to be added and to confirm the occurrence of denitrification in an appropriate time frame of 4-6 h. From these tests, an optimum C/N ratio was observed to be somewhere between 2 to 4, somewhat higher than all the theoretical C/N ratios required for a complete denitrification using the four major VFAs identified in the digester effluent. During the denitrification batch tests, it was also observed that some NO₃⁻- N was removed instantaneously by reacting with As (III) (As₂O₃); while an increase in alkalinity of around 5.60 mg as CaCO₃ produced per mg NO₃⁻- N reduction was also observed. This latter number was very close to the theoretical value of alkalinity production (i.e. 5.41 mg as CaCO₃ per mg NO₃⁻- N). The effect of arsenic on the denitrification process was evaluated by observing the specific denitrification rate in series of denitrification batch tests (with different concentrations of arsenic). Results from the denitrification batch tests showed that there was a clear effect for both As (III) and As (V) on denitrification. In particular, the specific denitrification rate fell from 0.37 to 0.01 g NO₃⁻- N /g VSS per day as the concentration of As (III) increased from 0 to 50 mg/L. In contrast, there was comparatively less effect for As (V); i.e. only a 37 % decrease in the specific denitrification rate (from 0.34 g NO₃⁻- N /g VSS per day to 0.23 g NO₃⁻- N /g VSS per day) when the initial arsenic concentration increased from 0 to a very high level of 2,000 mg/L. The effects of both the As (III) and As (V) forms of inorganic arsenic on the denitrification rate were further quantified by constructing exponential equation models. It was suspected that the effect of As (III) on denitrification was more substantial than the effect of As (V) because of the former’s toxicity to microbes. Finally, the fate of arsenic was tracked by examining bacterial uptake. During the normal denitrification batch tests (i.e. designed for evaluation of the effect of arsenic on denitrification), no significant arsenic removal was observed. However, additional batch tests with a comparatively low concentration of biomass revealed that the denitrifying biomass removed 1.35 µg As (III) /g dry biomass and 2.10 µg As (V) /g dry biomass. In the second phase of this research, a series of arsenic adsorption batch tests as well as a column test were performed to examine the arsenic (As (III) and As (V)) removal efficiency of NZIS from an arsenic-contaminated water. The kinetics and isotherms for adsorption were analysed in addition to studying the effect of pH during the batch tests. Breakthrough characteristics for both As (III) and As (V) were studied to appraise the effectiveness of NZIS treating an arsenic contaminated water. Batch tests were performed with different concentrations of arsenic as well as at different pH conditions. A maximum adsorption of As (III) of approximately 90 % occurred at a pH of 7.5, while the As (V) adsorption reached its maximum value of 97.6 % at a very low pH value of 3. Both Langmuir and Freundlich Models were tested and found to fit with R² values of more than 0.92 in all cases. From the Langmuir adsorption model, the maximum adsorption capacity of NZIS for As (III) was estimated to be 1,250 µg/g, significantly higher (about three times) than for As (V) of 500 µg/g. In column tests, arsenic-contaminated water with total As concentration of 400 µg/L (in either form of As) were treated and a pore volume (PV) of 700 and 300 yielded a total arsenic level less than the WHO guideline value of 10 µg/L for As (III) and As (V) respectively; while, the breakthrough occurred after a throughput of approximately 3,000 PV of As (III) and 2,700 PV of As (V) with an average flow rate of approximately 1.0 mL/min.

No description available.

This thesis examines how the non-Newtonian characteristics of liquid hog manure affect the flow conditions within a steady-flow anaerobic digester. There are three main parts to this thesis. In the first part of this thesis, the physical properties of liquid hog manure and their variation with temperature and solids concentration are experimentally determined. Naturally¬¬-settled manure sampled from an outdoor storage lagoon is studied, and density, viscosity, and particle size distribution are measured. Hog manure with total solids concentrations of less than 3.6% exhibits Newtonian behaviour; manure between 3.6% and 6.5% total solids is pseudoplastic, and fits the power law; manure with more than 6.5% total solids exhibits non-Newtonian and time-dependent characteristics. The second part of this thesis investigates the flow of Newtonian and non-Newtonian fluids—represented by tap water and xanthan gum solution, respectively—within four lab-scale reactor geometries, using residence time distribution (RTD) experiments. The effect of reactor geometry, flow rate, and fluid viscosity are evaluated. In the third part of this thesis, flow conditions within lab-scale and pilot-scale anaerobic digester reactors are simulated using three-dimensional modeling techniques. The RTDs of lab-scale reactors as predicted by the 3D numerical models compare well to the experimental results. The 3D models are also validated using data from particle image velocimetry (PIV) experiments. Finally, the viscous properties of liquid hog manure at 3% and 8% total solids are incorporated into the models, and the results are evaluated.

This thesis examines how the non-Newtonian characteristics of liquid hog manure affect the flow conditions within a steady-flow anaerobic digester. There are three main parts to this thesis. In the first part of this thesis, the physical properties of liquid hog manure and their variation with temperature and solids concentration are experimentally determined. Naturally¬¬-settled manure sampled from an outdoor storage lagoon is studied, and density, viscosity, and particle size distribution are measured. Hog manure with total solids concentrations of less than 3.6% exhibits Newtonian behaviour; manure between 3.6% and 6.5% total solids is pseudoplastic, and fits the power law; manure with more than 6.5% total solids exhibits non-Newtonian and time-dependent characteristics. The second part of this thesis investigates the flow of Newtonian and non-Newtonian fluids—represented by tap water and xanthan gum solution, respectively—within four lab-scale reactor geometries, using residence time distribution (RTD) experiments. The effect of reactor geometry, flow rate, and fluid viscosity are evaluated. In the third part of this thesis, flow conditions within lab-scale and pilot-scale anaerobic digester reactors are simulated using three-dimensional modeling techniques. The RTDs of lab-scale reactors as predicted by the 3D numerical models compare well to the experimental results. The 3D models are also validated using data from particle image velocimetry (PIV) experiments. Finally, the viscous properties of liquid hog manure at 3% and 8% total solids are incorporated into the models, and the results are evaluated.

La digestion anaérobie est une succession d’étapes de dégradation de la matière organique, par l’intermédiaire de microorganismes, opérée industriellement dans des digesteurs en béton. Des métabolites microbiens (acides gras volatils (AGV), NH4+, CO2) produits au cours du processus de digestion attaquent la matrice cimentaire du béton. Afin d’assurer un développement pérenne de la filière de méthanisation, il est donc nécessaire de comprendre d’abord tous ces phénomènes d’altération pour ensuite proposer des solutions durables pour les matériaux de construction des digesteurs. Les objectifs de la thèse visaient à identifier et quantifier les agents agressifs pour le béton présents dans les milieux de la méthanisation, puis à comprendre leurs rôles dans les mécanismes d’altération des matrices cimentaires. Enfin, l’action de ces milieux a pu être comparée sur un panel de matériaux cimentaires réalisées à partir de différents liants : ciment Portland ordinaire, ciment de haut-fourneau, ciment d’aluminate de calcium et liant alcali activé. Dans des digesteurs de laboratoire, les concentrations maximales des agents chimiques agressifs mesurées pendant la digestion anaérobie d’un biodéchet modèle étaient de 3000 mg.L-1 d’AGV, de 800 mg.L-1 de NH4+, et de 140 mg.L-1 de CO2 dissous. La prolifération de microorganismes capables de métaboliser ces composés chimiques agressifs a été observée à la surface des matériaux cimentaires exposés dans le biodéchet au cours de sa digestion. La zone dégradée des matériaux cimentaires exposés est partiellement décalcifiée, vraisemblablement du fait de l’action des AGV et de l’ammonium NH4+, et carbonatée en raison de la présence de CO2 dissous. Des essais in situ, c’est à dire en conditions réelles, réalisées sur une plateforme expérimentale de méthanisation, ont permis de confirmer les phénomènes d’altération observés en laboratoire. En termes de durabilité, le ciment alumineux présente la meilleure résistance face aux attaques biochimiques lorsqu’on le compare au ciment ordinaire ou aux ciments composés de laitier de haut-fourneau au sein de systèmes de méthanisation en laboratoire ou in situ. / Anaerobic digestion consists in the degradation of organic matter by the successive actions of microorganisms, industrially operated in digesters made of concrete. Microbial metabolites (volatile fatty acids (VFA), NH4+, CO2) produced during this process attack the cementitious matrix of the concrete. To ensure the development of this new industrial field, it appears essential to understand first the alteration phenomena, then to propose durable solutions for digesters’ construction materials. The thesis’ objectives were first to identify and to quantify the aggressive agents for concrete in anaerobic digestion media, then to understand their impacts on the cementitious materials’ alteration mechanisms. Finally, the impacts of those media were compared on different cement pastes made of : ordinary Portland cement, blast furnace slag cement, calcium aluminate cement or alkali activated materials. During laboratory tests, the maximal concentration in aggressive agents measured during the digestion of a synthetic biowaste were 3 000 mg.L-1 of VFA, 800 mg.L-1 of NH4+, and 140 mg.L-1 of dissolved CO2. The colonization of the microorganisms able to produce the aggressive agents has been observed on the cementitious materials’ surfaces exposed to the biowaste during digestion. The external degraded layers of the exposed cementitious materials are partially decalcified, most likely regarding to the action of the VFA and the NH4+. Carbonation has also been detected caused by the dissolved CO2. In situ experiments, in real conditions, achieved in an experimental anaerobic digestion platform, confirmed the alteration phenomena distinguished in the laboratory tests. In terms of durability, calcium aluminate cement present the best performances against the biochemical attacks compared to ordinary cement or blast furnace slag cement in laboratory or in situ anaerobic digestion systems.

Around three-quarters of Bangladeshis (total population 164 million) live in rural areas: only 25% of these households have access to grid electricity with non-reliable supply despite the country’s successful rural electrification program, kerosene is the predominant source for lighting, and woody biomass is virtually the only option available for cooking. Aside from this energy service challenges the rural population also struggles with unsafe drinking water in terms of widespread arsenic contamination of well water. Access to electricity, clean cooking gas, and safe drinking water services are genuine needs of the rural poor and are essential to improving welfare. These needs can be addressed individually or using an integrated approach. Anaerobic digesters are now a proven technology and remain economically promising in the rural setting, where connection to the public electric and gas grids are not available/either not cost effective or feasible, and where energy and water scarcity are severe. As the technologies continue to improve, and as energy and safe water becomes scarce and fossil fuel energy prices rise, renewable energy based services and technological integration becomes more viable techno-economically. In these circumstances, the integration of biogas digester with power generation and water purification unit is an innovative concept that could be applied in remote areas of Bangladesh.   This work presents a new concept for integrated polygeneration and analyzes the techno-economic performance of the scheme for meeting the demand of electricity, cooking energy and safe drinking water of 30 households in a rural village of Bangladesh. This study considers a holistic approach towards tackling both of these issues via integrated renewable energy-based polygeneration employed at the community level. The polygeneration unit under consideration provides electricity via cow dung-fed digester, which in turn is coupled to a gas engine. Excess digester gas is employed for cooking, while waste heat from the process drives a membrane distillation unit for water purification. The specific technologies chosen for the key energy conversion steps are as follows: plug-flow digester; internal combustion engine; and air-gap membrane distillation. The technical features, energy consumption, and potential of renewable energy use in driving the main integrated processes are reviewed and analyzed in this thesis. This study also examines one approach by investigating the application of suitable membrane technologies, specifically air gap membrane distillation (AGMD), as a promising method for small-scale, low cost deployment.    Experimental results show that the tested AGMD prototype is capable of achieving high separation efficiency, as all product water samples showed arsenic levels below accepted limits. Mass flows and energy balance, life cycle cost (levelized cost) of producing electricity, cooking gas and safe drinking water as well as the payback period of such a polygeneration system were studied. The results indicate that this polygeneration system is much more competitive and promising than other available technologies when attempting to solve the energy and arsenic-related problems in Bangladesh. One of the main encouraging issues of this integrated system is the levelized cost of the three major services: cooking gas (0.015 USD/kWh), electricity (0.042 USD/kWh–an orders of magnitude lower than comparable photovoltaic or wind systems) and safe drinking water (0.003 USD/liter). Additionally, the payback period is between 2.6 to 4 years. / <p>QC 20150516</p>

Biogas, a gaseous mixture produced during decomposition of organic matter, is a renewable, easily generated and common byproduct of anaerobic digestion at wastewater treatment plants (WWTP), landfills and agricultural operations. There is growing interest in researching and utilizing the energy potential associated with its combustion. Siloxanes, a family of volatile organic silicon compounds, pose large impediments to biogas usage due to the formation and precipitation of silicon dioxide within combustion devices. Removal of siloxanes prior to combustion is therefore a growing endeavor. Research was performed to synthesize a representative gas stream produced from anaerobic digesters within WWTP. Methane, carbon dioxide and hydrogen sulfide were combined with humidity and gaseous siloxane in levels characteristically seen exiting anaerobic digesters. A methanol impinger train was utilized to sample the biogas composite. Gas chromatography-mass spectrometry (GC-MS) was used to determine gas-phase siloxane concentrations in the gas stream effluent for the purposes of confirming the generation of a consistent and reproducible biogas stream. / Master of Science

No description available.