The research represents a first approach to measure the utilization potential of ultrasonic pretreatment on six different substrates: fat, oil and grease (FOG), paper sludge, ground switch grass, ground hay, ground wheat straw, and cut wheat straw. Several laboratories techniques were applied to determine the influence of ultrasonication on biogas production and yield, biogas quality, and digestibility ratio. With the data, mathematical definitions of Net Energy Balance and Net Economy Balance were computed to draw a first justification or rejection of the use of this pretreatment technology for the specific substrates. Ultrasonic pretreatment has a significant effect on biogas production and yield as well as digestibility ratio (p-value < 0.0001) from the early stages of digestion until as far as 50 days of digestion. Ultrasonication and macro particle size management did not influence significantly the methane (CH4) content in the biogas (p-value = 0.1793). Also, the impact of ultrasonication on the substrate varies between all studied feedstock. Most of the ultrasonicated digestion cases studied provided a negative Net Energy and Economic Balance except for FOG where a certain window of utilization was found. In the context of an ultrasonication process retrofit upgrade, the technology looks to be more useful for substrates that are hard to digest when the retention time is, unfortunately, longer than common retention time. In the context of a new facility, a design that includes an understood ultrasonication technology has yet a small potential success depending on several variables. The ultrasonication technology for anaerobic digestion is hard to recommend due to its energy consumption that, in many cases, overshadows the energy surplus derived from its use. / MITACS

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The objective of this work is to optimize high-power low-frequency sonication (US) pretreatment of sludge, and especially to investigate for the first time possible improvements by higher pressure and audible frequency. After a preliminary examination of regular process conditions (sludge conditioning, sludge type, prior alkalization, temperature control, etc), effects of US parameters (power -PUS, intensity -IUS, specific energy input -ES, frequency -FS, etc.) and of hydrostatic pressure (Ph) were specifically looked into, separately and in combination, first under cooling at constant temperature (28°C), then under the progressive temperature rise provoked by sonication. First, it was confirmed that specific energy input (ES) plays a key role in sludge US disintegration (i.e. solubilisation of organic matter) and that temperature rise during adiabatic-like sonication is beneficial through additional effects of thermal hydrolysis and cavitation. At a given ES value, low FS (12 kHz vs. 20 kHz) and high PUS enhance soluble chemical oxygen demand (SCOD) due to more violent cavitation, while hydrostatic pressure gives rise to an optimum value due to its opposite effects on cavitation threshold and intensity. One major result is that optimal pressure depends on IUS (P¬US) as well as temperature profile, but not on ES, FS, nor sludge type. Setting the other parameters at the most favorable conditions expected, i.e. 12 kHz, 360 W , 28 gTS/L, and adiabatic conditions, final optimization was achieved by searching for this pressure optimum and examining sequential procedure to avoid too high temperature dampening cavitation intensity and damaging the transducer. Such conditions with sequential mode and Ph of 3.25 bar being selected succeeded in achieving very high SCOD, but only marginally improved subsequent methanization yield.

Sludge management is one of the most difficult and expensive problems in wastewater treatment plant operation. Consequently, &amp / #8216 / sludge minimization&amp / #8217 / concept arose to solve the excess sludge production by sludge pretreatment. Sludge pretreatment converts the waste sludge into a more bioavailable substrate for anaerobic digestion and leads to an enhanced degradation. The enhanced degradation results in more organic reduction and more biogas production. Therefore, sludge pretreatment is a means of improving sludge management in a treatment plant. Among pretreatment methods, acidic pretreatment has been subject of limited successful studies reported in the literature. On the contrary / ultrasonic pretreatment was reported as an effective pretreatment method. Main objective of this study was to investigate the effects of these two pretreatment methods and their combination in order to achieve a synergistic effect and improve the success of both pretreatment methods. Experimental investigation of pretreatment methods consists of preliminary studies for deciding the most appropriate pretreatment method. Anaerobic batch tests were conducted for optimization of the parameters of selected method. Finally, operation of semi-continuous anaerobic reactors was to investigate the effect of pretreatment on anaerobic digestion in details. Preliminary studies indicated that, more effective pretreatment method in terms of solubilization of organics is ultrasonic pretreatment. Fifteen minutes of sonication enhanced 50 mg/L initial soluble COD concentration up to a value of 2500 mg/L. Biochemical methane potential tests indicated that the increased soluble substrate improved anaerobic biodegradability concurrently. Finally, semi-continuous anaerobic reactors were used to investigate the efficiency of pretreatment under different operating conditions. Results indicate that at SRT 15 days and OLR 0.5 kg/m3d ultrasonic pretreatment improved the daily biogas production of anaerobic digester by 49% and methane percentage by 16% and 24% more volatile solids were removed after pretreatment. Moreover, even after pushing reactors into worse operating conditions such as shorter solids retention time (7.5 days) and low strength influent, pretreatment worked efficiently and improved the anaerobic digestion. Finally cost calculations were performed. Considering the gatherings from enhancement of biogas amount, higher methane percentage and smaller amounts of volatile solid disposal from a treatment plant / installation and operation costs of ultrasound were calculated. The payback period of the installation was found to be 4.7 years.

The aim of the present work was to study the effect of the ultrasonic pretreatment of cowpea bean pod biomass in the bio-oil production by pyrolysis. The biomass was pretreated during 0.5, 1.5, 03, 06, 08 and 12 hours with the addition of 20% (w/w) potassium phosphate. The biomass presented low oil and protein contents, 0.72% and 8.5%, respectively, and ash content of 4.38% for in natura biomass, being alkali and alkaline earth metals (K, Mg, Na, Ca) and phosphorus the main inorganic compounds. For the pretreated samples, the ash content was around 19.5% (w/w). The elemental analysis showed that the in natura biomass contained 42.01% of carbon, 5.89% of hydrogen, 1.36% of nitrogen and 37.48% of oxygen, presenting lower values for the treated biomass mainly due to the increase of inorganic content by the addition of potassium phosphate. The thermogravimetric curves profiles of the samples changed with different ultrasonic pretreatment times, presenting a decrease in temperature, where the highest mass loss rate occurs, compared to in natura biomass. The pyrolysis was carried out at 600 °C and N2 flow of 5mL min-1, yielding a 25.29% in bio-oil for the in natura biomass, while the samples submitted to pretreatment presented yield between 21 and 23%. The pretreated samples showed a decrease in the biochar yield and an increase in the biogas yield compared to the in natura sample. The chromatographic analysis of the bio-oils, showed that the ultrasonic pretreatment associated with K3PO4 caused a considerable increase in the phenolic compounds content, and the best pretreatment time, 1.5 h, showed 81.21 mg g-1, against 48.90 mg g-1 of phenolics in the bio-oil from in natura biomass. / O presente trabalho teve como objetivo estudar o efeito do pré-tratamento ultrassônico na obtenção de bio-óleo a partir da pirólise da biomassa de vagem de feijão caupi. A biomassa utilizada foi submetida a diferentes tempos de prétratamento (0,5, 1,5, 03, 06, 08 e 12 h) com a adição de K3PO4 à 20%. A caracterização da biomassa obteve baixos teores de óleo e proteínas, 0,72% e 8,5% respectivamente, apresentando teor de cinzas para a biomassa in natura de 4,38%, sendo os principais componentes inorgânicos os metais alcalinos e alcalinos terrosos (K, Mg, Na, Ca) e fósforo. Para as amostras pré-tratadas o teor de cinzas ficou em torno de 19,5%. Os valores da análise elementar para a biomassa in natura foram carbono (42,01%), hidrogênio (5,89%), nitrogênio (1,36%) e oxigênio (37,48%), apresentando valores menores para as biomassas pré-tratadas principalmente devido ao aumento do teor de inorgânicos pela adição do fosfato de potássio. As curvas termogravimétricas das amostras se diferenciaram quanto aos perfis de acordo com o tempo de pré-tratamento ultrassônico, com diminuição da temperatura onde ocorre maior taxa perda de massa em comparação à biomassa in natura. As pirólises foram realizadas à 600 °C e fluxo de N2 de 5mL min-1, obtendo rendimento de 25,29% em bio-óleo para a biomassa in natura, enquanto as amostras submetidas à pré-tratamento apresentaram menor rendimento, entre 21 e 23%. As amostras pré-tratadas apresentaram diminuição no rendimento de biocarvão e aumento do rendimento de biogás em comparação à amostra in natura. A partir da análise cromatográfica dos bio-óleos constatou-se que o pré-tratamento ultrassônico associado à K3PO4 provocou um aumento considerável no teor de compostos fenólicos, sendo que o melhor tempo de pré-tratamento, 1,5 h, apresentou 81,21 mg g-1, contra 48,90 mg g-1 de fenólicos no bio-óleo proveniente da biomassa in natura. / São Cristóvão, SE

L'objectif de ce travail est d'optimiser le prétraitement de boues par des ultrasons de puissance (US) à basses fréquences, et en particulier d‘étudier pour la première fois des améliorations possibles en modifiant la pression hydrostatique, et la fréquence jusqu’à l’audible. Après un examen préliminaire des conditions du procédé (conditionnement des boues, type de boues, alcalinisation préalable, contrôle de la température), les effets des paramètres ultrasonores (puissance, intensité, énergie spécifique, fréquence) et de la pression hydrostatique ont été spécifiquement étudiés, séparément et simultanément, d’abord à température constante (28°C), puis sans refroidissement. On a ainsi vérifié que l’énergie spécifique joue un rôle clé dans la désintégration des boues sous US (i.e. solubilisation de la matière organique) et que l'élévation de température pendant la sonication adiabatique est bénéfique grâce aux effets combinés d’hydrolyse thermique et de cavitation. Pour une énergie spécifique donnée, une faible fréquence (12 kHz contre 20 kHz) et une haute puissance améliorent la solubilisation de la matière organique grâce à une cavitation plus violente, tandis qu’on observe un optimum de pression hydrostatique en raison de ses effets opposés sur le seuil et l'intensité de la cavitation. Un résultat important est que la pression optimale dépend de l’intensité ultrasonore et du profil de température, mais pas de l’énergie spécifique, ni de la fréquence, ni du type de boues. Après avoir fixé les conditions les plus favorables (soit 12 kHz, 360 W, 28 gTS/L et conditions adiabatiques), l‘optimisation finale a fourni la pression de travail (3,25 bar) et les paramètres du mode séquentiel (US ON/OFF, permettant d‘éviter de hautes températures qui amortissement l‘intensité de la cavitation et peuvent endommager le transducteur). Ces conditions ont permis d‘atteindre un rendement d’extraction de la DCO très élevé, mais n’améliorent que faiblement le rendement ultérieur de méthanisation. / The objective of this work is to optimize high-power low-frequency sonication (US) pretreatment of sludge, and especially to investigate for the first time possible improvements by higher pressure and audible frequency. After a preliminary examination of regular process conditions (sludge conditioning, sludge type, prior alkalization, temperature control, etc.), effects of US parameters (power -PUS, intensity -IUS, specific energy input -ES, frequency -FS, etc.) and of hydrostatic pressure (Ph) were specifically looked into, separately and in combination, first under cooling at constant temperature (28°C), then under the progressive temperature rise provoked by sonication. First, it was confirmed that specific energy input (ES) plays a key role in sludge US disintegration (i.e. solubilisation of organic matter) and that temperature rise during adiabatic-like sonication is beneficial through additional effects of thermal hydrolysis and cavitation. At a given ES value, low FS (12 kHz vs. 20 kHz) and high PUS enhance soluble chemical oxygen demand (SCOD) due to more violent cavitation, while hydrostatic pressure gives rise to an optimum value due to its opposite effects on cavitation threshold and intensity. One major result is that optimal pressure depends on IUS (PUS) as well as temperature profile, but not on ES, FS, nor sludge type. Setting the other parameters at the most favorable conditions expected, i.e. 12 kHz, 360 W , 28 gTS/L, and adiabatic conditions, final optimization was achieved by searching for this pressure optimum and examining sequential procedure to avoid too high temperature dampening cavitation intensity and damaging the transducer. Such conditions with sequential mode and Ph of 3.25 bar being selected succeeded in achieving very high SCOD, but only marginally improved subsequent methanization yield.