Modern wastewater treatment provides great benefit to society by reducing the transmission of disease. In recent years computer simulation of whole plants has allowed for improved design and more economical consideration of alternatives. One new alternative for wastewater treatment is the pre-treatment of sludges, although this technology has not yet been adapted for computer simulation. This thesis describes research which was conducted to describe pre-treatments in terms appropriate for whole-plant computer models. Pre-treatment shows promise in terms of reducing sludge, a waste product the disposal of which can be costly depending on the applicable regulations. At the same time pre-treatment can improve the generation of biogas, which is readily converted to heat and/or electricity and can help to offset treatment energy requirements. Pre-treatments can be broadly categorized as physical, chemical, or thermal. For this study, ultrasound was selected as a model physical pre-treatment and ozone as a model chemical pre-treatment. The range of doses to be tested was obtained by reviewing earlier literature. Waste activated sludge was obtained from pilot reactors treating screened municipal wastewater. This sludge was subjected to a range of doses in batch reactors. Conventional laboratory analyses were used to determine the effects of pre-treatment on such parameters as chemical oxidant demand, solids, and various nitrogen fractions. As well, respirometry was utilized to estimate the biologically active and bioavailable fractions. A novel technique for analysis of respirometric data was developed, which consisted of fitting synthetic oxygen uptake rate curves to the measured data. Both ultrasound and ozone were observed to decrease the amount of active biomass present while increasing the amount of biodegradable material. The conversions between these fractions were modeled using simple functions of pre-treatment dose. For ultrasound, a conversion which exponentially decayed with respect to increasing ultrasound dose was used to relate these fractions. For ozone, the conversion from active biomass to slowly degradable material occurred more slowly than the conversion to rapidly degradable material; as such two conversions were modeled, each exponentially decaying with respect to dose but with different dose constants. The observed conversions were added to a whole-plant model and the implications of the models were considered for one simple wastewater treatment plant. Both pre-treatments showed a decrease in total sludge production and an increase in biogas production, as predicted by earlier research. Published full-scale results were not reported with sufficient detail to be replicated, and so a quantitative comparison was not possible.

Modern wastewater treatment provides great benefit to society by reducing the transmission of disease. In recent years computer simulation of whole plants has allowed for improved design and more economical consideration of alternatives. One new alternative for wastewater treatment is the pre-treatment of sludges, although this technology has not yet been adapted for computer simulation. This thesis describes research which was conducted to describe pre-treatments in terms appropriate for whole-plant computer models. Pre-treatment shows promise in terms of reducing sludge, a waste product the disposal of which can be costly depending on the applicable regulations. At the same time pre-treatment can improve the generation of biogas, which is readily converted to heat and/or electricity and can help to offset treatment energy requirements. Pre-treatments can be broadly categorized as physical, chemical, or thermal. For this study, ultrasound was selected as a model physical pre-treatment and ozone as a model chemical pre-treatment. The range of doses to be tested was obtained by reviewing earlier literature. Waste activated sludge was obtained from pilot reactors treating screened municipal wastewater. This sludge was subjected to a range of doses in batch reactors. Conventional laboratory analyses were used to determine the effects of pre-treatment on such parameters as chemical oxidant demand, solids, and various nitrogen fractions. As well, respirometry was utilized to estimate the biologically active and bioavailable fractions. A novel technique for analysis of respirometric data was developed, which consisted of fitting synthetic oxygen uptake rate curves to the measured data. Both ultrasound and ozone were observed to decrease the amount of active biomass present while increasing the amount of biodegradable material. The conversions between these fractions were modeled using simple functions of pre-treatment dose. For ultrasound, a conversion which exponentially decayed with respect to increasing ultrasound dose was used to relate these fractions. For ozone, the conversion from active biomass to slowly degradable material occurred more slowly than the conversion to rapidly degradable material; as such two conversions were modeled, each exponentially decaying with respect to dose but with different dose constants. The observed conversions were added to a whole-plant model and the implications of the models were considered for one simple wastewater treatment plant. Both pre-treatments showed a decrease in total sludge production and an increase in biogas production, as predicted by earlier research. Published full-scale results were not reported with sufficient detail to be replicated, and so a quantitative comparison was not possible.

Este trabalho investigou o efeito da temperatura nos sistemas aneróbios com células imobilizadas tendo como estudo de caso um sistema anaeróbio em duas fases. Inicialmente, foram realizados experimentos preliminares com um sistema em duas fases composto por Reator Acidogênico Horizontal Tubular (RAHT) seguido de Reator Anaeróbio Horizontal de Leito Fixo (RAHLF), nas temperaturas de 15ºC, 20ºC e 25ºC. Os resultados mostraram que o RAHT alcançou 48% de remoção de DQO e que a desvantagem da ausência de microrganismos consumidores de H2 no sistema praticamente não afetou a produção de ácido acético. Pôde-se observar que na faixa de temperatura estudada o RAHT não apresentou mudanças significativas em seu desempenho. Posteriormente foram realizados experimentos com cinco reatores metanogênicos do tipo RAHLF, alimentados com esgoto sintético simulando o efluente do RAHT, com velocidades de 10,4 cm/h, a 52,0 cm/h e temperatura de 15ºC a 35ºC. Os resultados permitiriam o desenvolvimento de um modelo empírico-estatístico para simulação do desempenho dos reatores, tendo como variáveis a velocidade superficial do líquido sobre as biopartículas e a temperatura de operação. Os resultados preditos pelo modelo demonstraram boa representatividade dos valores experimentais. Com isso, foi possível observar as influências da velocidade superficial (vs) e da temperatura, nas concentrações residuais de substrato (Sr) e nas constantes cinéticas aparentes de primeira ordem (K1app). Conclui-se então, que apesar do aumento de vs resultar em maiores valores de K1app, também foi observado aumento no valor de Sr indicando que existe um tempo de contato mínimo entre os microrganismos e o substrato. / The effects of temperature and superficial velocity in an anaerobic methanogenic immobilized cell rector of a two phase-system were investigated. Preliminarily, a Tubular Horizontal Acidogenic Reactor (THAR) followed by Horizontal-flow Anaerobic Immobilized Biomass (HAIB) composed the experimental system, operated at the temperatures of 15°C, 20°C and 25°C. COD removal efficiency of 48% was observed in the THAR. Likewise, the disadvantage of the absence of H2-consumer methanogenics microorganisms in the system almost did not affect the production of acetic acid. The temperature variation has not caused significant changes in the THAR performance. The next step was the development of experiments using five methanogenics HAIB reactors fed on synthetic wastewater simulating THAR effluent having superficial velocities from 10,4 cm/h to 52,0 cm/h and temperature from 15°C to 35°C. The results enabled the development of a statistical-empiric modeling to simulate the reactors performance using the liquid superficial velocities and the temperature operation as model variables. The model demonstrated a good agreement with the experimental values. The influence of the superficial velocities (vs) and temperature, in the substrate residual concentration (Sr) and in the first order (K1app) apparent kinetic constant was observed. Despite the K1app values have increased largely with vs, the Sr concentration also increased. These results permit to conclude that a minimum contact time between the microorganisms and the substrate may be necessary in such processes.

Este trabalho investigou o efeito da temperatura nos sistemas aneróbios com células imobilizadas tendo como estudo de caso um sistema anaeróbio em duas fases. Inicialmente, foram realizados experimentos preliminares com um sistema em duas fases composto por Reator Acidogênico Horizontal Tubular (RAHT) seguido de Reator Anaeróbio Horizontal de Leito Fixo (RAHLF), nas temperaturas de 15ºC, 20ºC e 25ºC. Os resultados mostraram que o RAHT alcançou 48% de remoção de DQO e que a desvantagem da ausência de microrganismos consumidores de H2 no sistema praticamente não afetou a produção de ácido acético. Pôde-se observar que na faixa de temperatura estudada o RAHT não apresentou mudanças significativas em seu desempenho. Posteriormente foram realizados experimentos com cinco reatores metanogênicos do tipo RAHLF, alimentados com esgoto sintético simulando o efluente do RAHT, com velocidades de 10,4 cm/h, a 52,0 cm/h e temperatura de 15ºC a 35ºC. Os resultados permitiriam o desenvolvimento de um modelo empírico-estatístico para simulação do desempenho dos reatores, tendo como variáveis a velocidade superficial do líquido sobre as biopartículas e a temperatura de operação. Os resultados preditos pelo modelo demonstraram boa representatividade dos valores experimentais. Com isso, foi possível observar as influências da velocidade superficial (vs) e da temperatura, nas concentrações residuais de substrato (Sr) e nas constantes cinéticas aparentes de primeira ordem (K1app). Conclui-se então, que apesar do aumento de vs resultar em maiores valores de K1app, também foi observado aumento no valor de Sr indicando que existe um tempo de contato mínimo entre os microrganismos e o substrato. / The effects of temperature and superficial velocity in an anaerobic methanogenic immobilized cell rector of a two phase-system were investigated. Preliminarily, a Tubular Horizontal Acidogenic Reactor (THAR) followed by Horizontal-flow Anaerobic Immobilized Biomass (HAIB) composed the experimental system, operated at the temperatures of 15°C, 20°C and 25°C. COD removal efficiency of 48% was observed in the THAR. Likewise, the disadvantage of the absence of H2-consumer methanogenics microorganisms in the system almost did not affect the production of acetic acid. The temperature variation has not caused significant changes in the THAR performance. The next step was the development of experiments using five methanogenics HAIB reactors fed on synthetic wastewater simulating THAR effluent having superficial velocities from 10,4 cm/h to 52,0 cm/h and temperature from 15°C to 35°C. The results enabled the development of a statistical-empiric modeling to simulate the reactors performance using the liquid superficial velocities and the temperature operation as model variables. The model demonstrated a good agreement with the experimental values. The influence of the superficial velocities (vs) and temperature, in the substrate residual concentration (Sr) and in the first order (K1app) apparent kinetic constant was observed. Despite the K1app values have increased largely with vs, the Sr concentration also increased. These results permit to conclude that a minimum contact time between the microorganisms and the substrate may be necessary in such processes.