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Abstract: Hydrogen can be a renewable energy source to replace conventional fossil fuels. Compared to current hydrogen production processes by consuming fossil fuels, biological hydrogen production has the advantage of being environmentally friendly because of the use of renewable and low value biological materials. Some hyperthermophiles, such as Thermotoga species, are capable of producing hydrogen during growth. In this study, Thermotoga maritima, Thermotoga neapolitana DSM 4359 and DSM 5068, were used to investigate their potential in converting selected sugars (glucose and xylose) and complex carbon sources (cellulose, starch, xylan and agricultural residues, such as barley straw, corn stover, soybean straw, wheat straw and corn husk) to hydrogen. In addition, factors which influenced growth and hydrogen production were studied, and optimal conditions for hydrogen production were obtained. All three Thermotoga species could grow in the presence of mono sugars (glucose, xylose) and complex carbohydrates (starch, xylan, milled corn husk). They all could produce hydrogen in the presence of micro-molar level of oxygen without addition of any reducing agents in the growth medium. Compared to the slight inhibition caused by L-lactate accumulation during the growth, gradual pH decreases were the main reasons to inhibit both growth and hydrogen production of T. neapolitana species. Increasing the initial pH of the growth medium to 8.5 and stabilizing the pH by 50 mM Triz buffer resulted in higher growth and hydrogen production of T. neapolitana strains. Adjusting the medium pH at early stationary phase also increased the hydrogen production, and fewer enhancements to the growth. The pH control methods also resulted in higher conversion efficiency (converting glucose to H2) of T. neapolitana strains from 2.2 to 3.6 (H2/glucose), which was approximately 90% of the theoretical efficiency (4 moles H2 produced from 1 mole glucose). The expression of hydrogenases of T. neapolitana strains could also be increased by the pH control methods. Thermotoga species could grow and produce hydrogen using agricultural residues, such as corn husk, achieving 60% growth and hydrogen production as compared to that iii from glucose. With pH control methods, hydrogen production by T. neapolitana strains from corn husk was higher than that from glucose without pH control. These results indicated that the pH was the main factor to affect both hydrogen production and growth of T. neapolitana species, and optimal conditions for hydrogen production could be achieved by using pH control methods. Selected agricultural residues could be utilized for biological hydrogen production by Thermotoga species with minimum pre-treatment, and the pH control methods could result in a higher hydrogen production compared to that from glucose. Further studies on the continuous growth and hydrogenases of Thermotoga species are needed for better understanding of the hydrogen production mechanisms.

Maintaining the pH of a fluid or a solution at a specific value is a concern in many industrial processes, wastewater management, and food and pharmaceutical production. Given the importance of controlling pH in many processes, the objective of this thesis is to study and compare the effectiveness of some controller algorithms to control the pH of a process. In this study, the performance of three controller algorithms, namely PID, fractional PID and LA controllers, is evaluated for the control of a simple neutralization process using conventional controller performance metrics. Performance metrics used are the response time, the Integral of the Time weighted Absolute Error (ITAE), the Integral of the Squared Error (ISE), and the Integral of the Squares of the changes (ΔU) in the manipulated variable (ISDU). The three controllers were therefore tuned to minimize one or a combination of the controller performance metrics. Results show that PID, fractional PID and LA controllers implemented and tested in this research are all worthy controllers for maintaining pH of the neutralization process. Simulation results show that the three controllers can be used with confidence to cope with the high nonlinearity of a pH neutralization process provided that the process is properly designed. The relative small gain in performance obtained with the fractional PID controller, compared to a linear PID controller, suggests that it is not worth resorting to a fractional PID controller given its complexity and higher computation effort. Results show that PID and LA controllers are easy to implement with short response time and low ITAE and ISDU performance metrics.

This investigation tested simulated saline lake environments as mineralization sites for sequestering anthropogenic CO2. Four unique saline lakes were simulated in the laboratory. Two sets of experiments were conducted by diffusing CO2(g) through each simulated lake over 30 days. The first set tested the carbonate system response to elevated CO2(g). The second set of experiments replicated the same process but used ammonium hydroxide to elevate pH. Water samples were collected daily to test for cation loss via mineralization. Rapid mineralization occurred with the pH enhancer and cation activity was greatly reduced by as much as 38,000 mg/L Ca due to precipitation. This resulted in a mass of 100,000 mg/L of CO2 being sequestered via Ca and Mg-carbonate mineralization. With proper geochemical conditions, saline lake environments can therefore potentially serve a purpose in sequestering CO2(g).

Neuro-Fuzzy systems are the systems that neural networks (NN) are incorporated in fuzzy systems, which can use knowledge automatically by learning algorithms of NNs. They can be viewed as a mixture of local experts. Adaptive Neuro-Fuzzy inference system (ANFIS) is one of the examples of Neuro Fuzzy systems in which a fuzzy system is implemented in the framework of adaptive networks. ANFIS constructs an input-output mapping based both on human knowledge (in the form of fuzzy rules) and on generated input-output data pairs. Effective control for distillation systems, which are one of the important unit operations for chemical industries, can be easily designed with the known composition values. Online measurements of the compositions can be done using direct composition analyzers. However, online composition measurement is not feasible, since, these analyzers, like gas chromatographs, involve large measurement delays. As an alternative, compositions can be estimated from temperature measurements. Thus, an online estimator that utilizes temperature measurements can be used to infer the produced compositions. In this study, ANFIS estimators are designed to infer the top and bottom product compositions in a continuous distillation column and to infer the reflux drum compositions in a batch distillation column from the measurable tray temperatures. Designed estimator performances are further compared with the other types of estimators such as NN and Extended Kalman Filter (EKF). In this study, ANFIS performance is also investigated in the adaptive Neuro-Fuzzy control of a pH system. ANFIS is used in specialized learning algorithm as a controller. Simple ANFIS structure is designed and implemented in adaptive closed loop control scheme. The performance of ANFIS controller is also compared with that of NN for the case under study.

abstract: Microbial fuel cells(MFC) use micro-organisms called anode-respiring bacteria(ARB) to convert chemical energy into electrical energy. This process can not only treat wastewater but can also produce useful byproduct hydrogen peroxide(H2O2). Process variables like anode potential and pH play important role in the MFC operation and the focus of this dissertation are pH and potential control problems. Most of the adaptive pH control solutions use signal-based-norms as cost functions, but their strong dependency on excitation signal properties makes them sensitive to noise, disturbances, and modeling errors. System-based-norm( H-infinity) cost functions provide a viable alternative for the adaptation as they are less susceptible to the signal properties. Two variants of adaptive pH control algorithms that use approximate H-infinity frequency loop-shaping (FLS) cost metrics are proposed in this dissertation. A pH neutralization process with high retention time is studied using lab scale experiments and the experimental setup is used as a basis to develop a first-principles model. The analysis of such a model shows that only the gain of the process varies significantly with operating conditions and with buffering capacity. Consequently, the adaptation of the controller gain (single parameter) is sufficient to compensate for the variation in process gain and the focus of the proposed algorithms is the adaptation of the PI controller gain. Computer simulations and lab-scale experiments are used to study tracking, disturbance rejection and adaptation performance of these algorithms under different excitation conditions. Results show the proposed algorithm produces optimum that is less dependent on the excitation as compared to a commonly used L2 cost function based algorithm and tracks set-points reasonably well under practical conditions. The proposed direct pH control algorithm is integrated with the combined activated sludge anaerobic digestion model (CASADM) of an MFC and it is shown pH control improves its performance. Analytical grade potentiostats are commonly used in MFC potential control, but, their high cost (>$6000) and large size, make them nonviable for the field usage. This dissertation proposes an alternate low-cost($200) portable potentiostat solution. This potentiostat is tested using a ferricyanide reactor and results show it produces performance close to an analytical grade potentiostat. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

Flotation is an important and versatile mineral processing technique that is used to separate hydrophobic materials from hydrophilic. This technique makes it possible to mine complex ores that otherwise would have been regarded as uneconomic and non-beneficial. In this case flotation is used to separate copper from the unwanted gangue. The addition of lime is used to control the pH level in the flotation’s pulp, which governs the selectivity of the process, i.e. which minerals are recovered. Currently, fluctuating concentration grades of the produced metals have been observed in Boliden Aitik. Therefore, Boliden proposes a new control strategy which aims to maintain a constant ratio between the added lime and the incoming ore flow, but at the same time ensuring that the pH level is maintained within allowed limits. The aim of this thesis is to develop a model that captures the most essential dynamics of a process stage where lime is added, and then evaluate the suggested control strategy by studying suitable control structures. A linear model describing the system dynamics in a specific operating region is obtained by conducting step response experiments on the process. The model is then used to obtain a model describing the disturbances of the process, thereby yielding a complete model that describes the most important dynamics. The most promising control structure utilizes the concept of selective control, where a ratio controller is allowed to maintain a constant ratio as long as the pH level is within allowed boundaries. The pH level is maintained within the boundaries with upper and lower bound pH controllers that utilize the concept of an equivalent control objective (known as the strong acid equivalent) in order to achieve satisfying pH control. The results show that the control structure is able to maintain a constant ratio, and also ensure that the pH level is kept within the allowed limits. A cascade inspired pH ratio controller is also studied and evaluated. The results show that this pH ratio controller is only able to maintain a constant ratio as long as the incoming ore flow is constant. However, the outcomes also suggest that the concentration grades are either sensitive to variations in the ratio between added reagent and incoming ore flow, or that there is something else that causes them to vary.

This study evaluated four lactic streptococcal pairs which had been used routinely in cheese plants to determine (1) if strain growth interactions would produce stimulated growth and acid production; (2) final percent strain ratios and generation times after 1/1 initial inocula volumes and (3) whether final strain ratios could be controlled through adjustment of initial inocula volumes. Strains were propagated in fortified and unmodified whey substrate under pH control at 27C for 12 hours. Cell number and acid activity were evaluated on single and paired strains. Phage typing was used to determine generation times and the percent of each strain in a pair. Cell number increase was found in two of the four pairs grown in the unmodified whey substrate but in only one of the four pairs grown in the fortified medium. Acid production increase was observed in one pair when grown in the unmodified whey substrate, and in one other pair when grown in the fortified medium. Final strain percent ratios of the two of the four pairs (with initial inocula of a 1/1, v/v, ratio), demonstrated unbalanced growth, with one strain accounting for 76 to 92% of the final flora. Generation times of the dominant strain varied significantly with incocula ratios. Increasing the inocula volume ratio of the dominated strain of one pair from 1/1 to 19/1 dropped the final percent of the dominant strain from an average value of 83 to 66%. The dominant organism of this pair increased its doubling time when the inocula ratio was varied from 3/1 to 19/1 (dominated/dominant).

R-phenylacetylcarbinol (PAC) is used as a precursor for production of ephedrine and pseudoephedrine, which are anti-asthmatics and nasal decongestants. PAC is produced from benzaldehyde and pyruvate mediated by pyruvate decarboxylase (PDC). A strain of Rhizopus javanicus was evaluated for its production of PDC. The morphology of R. javanicus was influenced by the degree of aeration/agitation. A relatively high specific PDC activity (328 U decarboxylase g-1 mycelium) was achieved when aeration/agitation were reduced significantly in the latter stages of cultivation. The stability of partially purified PDC and crude extract from R. javanicus were evaluated by examining the enzyme deactivation kinetic in various conditions. R. javanicus PDC was less stable than Candida utilis PDC currently used in our group. A kinetic model for the deactivation of partially purified PDC extracted from C. utilis by benzaldehyde (0?00 mM) in 2.5 M MOPS buffer has been developed. An initial lag period prior to deactivation was found to occur, with first order dependencies of PDC deactivation on exposure time and on benzaldehyde concentration. A mathematical model for the enzymatic biotransformation of PAC and its associated by-products has been developed using a schematic method devised by King and Altman (1956) for deriving the rate equations. The rate equations for substrates, product and by-products have been derived from the patterns for yeast PDC and combined with a deactivation model for PDC from C. utilis. Initial rate and biotransformation studies were applied to refine and validate a mathematical model for PAC production. The rate of PAC formation was directly proportional to the enzyme activity level up to 5.0 U carboligase ml-1. Michaelis-Menten kinetics were determined for the effect of pyruvate concentration on the reaction rate. The effect of benzaldehyde on the rate of PAC production followed the sigmoidal shape of the Monod-Wyman-Changeux (MWC) model. The biotransformation model, which also included a term for PDC inactivation by benzaldehyde, was used to determine the overall rate constants for the formation of PAC, acetaldehyde and acetoin. Implementation of digital pH control for PAC production in a well-stirred organic-aqueous two-phase biotransformation system with 20 mM MOPS and 2.5 M dipropylene glycol (DPG) in aqueous phase resulted in similar level of PAC production [1.01 M (151 g l-1) in an organic phase and 115 mM (17.2 g l-1) in an aqueous phase after 47 h] to the system with a more expensive 2.5 M MOPS buffer.

A typical wastewater effluent of a chemical process can contain several strong acids/bases, weak acids/bases as well as their salts. They must be neutralized before being discharged to the environment in order to protect aquatic life and human welfare. However, neutralization process is highly non&ndash / linear and has time&ndash / varying characteristics. Therefore, the control of pH is a challenging problem where advanced control strategies are often considered. In this study, the aim is to design a pH control system that will be capable of controlling the pH-value of a plant waste-water effluent stream having unknown acids with unknown concentrations using an on&ndash / line identification procedure. A Model Predictive Controller, MPC, and a Fuzzy Logic Controller, FLC, are designed and used in a laboratory scale pH neutralization system. The characteristic of the upstream flow is obtained by a small identification reactor which has ten times faster dynamics and which is working parallel to actual neutralization tank. In the control strategy, steady&ndash / state titration curve of the process stream is obtained using the data collected in terms of pH value from the response of the identification reactor to a pulse input in base flow rate and using the simulated response of the identification reactor for the same input. After obtaining the steady&ndash / state titration curve, it is used in the design of a Proportional&ndash / Integral, PI, and of an Adaptive Model Predictive Controller, AMPC. On the other hand, identification reactor is not used in the FLC scheme. The performances of the designed controllers are tested mainly for disturbance rejection, set&ndash / point tracking and robustness issues theoretically and experimentally. The superiority of the FLC is verified.