CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / O tratamento de esgoto à fundamental para a manutenÃÃo da qualidade dos corpos dâÃgua. O presente trabalho investigou os aspectos tÃcnicos e operacionais da estaÃÃo de tratamento de esgoto (ETE) por lodos ativados com aeraÃÃo prolongada do Campus do Pici, situada na Universidade Federal do Cearà e propÃs medidas corretivas para compatibilizar as eficiÃncias reais com as de projeto. Por meio da anÃlise dos parÃmetros fÃsicos, quÃmicos e biolÃgicos de qualidade de Ãgua no afluente e efluente avaliou-se a eficiÃncia real da ETE, sendo que os principais parÃmetros operacionais foram avaliados no tratamento preliminar, tanque de aeraÃÃo e decantador secundÃrio. De posse dos dados coletados, compararam-se os dados de eficiÃncia com os valores citados na literatura para a tecnologia de lodos ativados por aeraÃÃo prolongada, assim como os valores obtidos na avaliaÃÃo operacional da ETE. Adicionalmente, foram verificados quais parÃmetros atendiam aos limites da Portaria no 154 da SuperintendÃncia Estadual de Meio ambiente do Cearà (Semace). Constatou-se que a ETE està submetida à sobrecarga hidrÃulica, comprometendo desta forma a eficiÃncia de remoÃÃo de matÃria orgÃnica e patogÃnicos, alÃm da baixa remoÃÃo de nutrientes, que faz com que o efluente nÃo atenda aos limites da supracitada portaria para amÃnia e fÃsforo. Como principal intervenÃÃo na ETE, recomendou-se a construÃÃo de mÃdulos complementares para distribuiÃÃo da vazÃo afluente de forma a sanar o problema de sobrecarga hidrÃulica, alÃm da possibilidade de inclusÃo de tratamento em nÃvel terciÃrio para o problema dos nutrientes. Sà apÃs a realizaÃÃo desta intervenÃÃo, poderÃo ser propostas medidas para a otimizaÃÃo da ETE e adequaÃÃo do efluente a todos os padrÃes de lanÃamento estabelecidos e avaliados na presente investigaÃÃo. / Wastewater treatment is very important to maintain the quality of water bodies. The present work evaluated the technical and operational aspects of an activated sludge Wastewater Treatment Plant (WTP), classified as prolonged aeration, located at the âCampus do Piciâ of the Federal University of CearÃ, and propose some interventions to make compatible real and design efficiencies. The physical-chemical and biological water analysis of influent and effluent allowed to monitor the real WTP efficiency. Some operational parameters were assessed in the preliminary treatment, aeration tank and secondary settler. After the monitoring time, the real organic matter, nutrients and pathogens removal efficiencies were compared to values reported in literature for the activated sludge system in extended aeration, as well as for the operational parameters. Additionally, it was verified which parameters were below the limits reported in the regulation (Portaria no 154 of Secretaria de Meio ambiente do CearÃ, Semace). It was concluded that the WTP was hydraulically overloaded, which is compromising the organic matter and pathogens removal, beside the low nutrients efficiency. Because of this, the WTP effluent is not accomplishing the regulation limits for ammonium and phosphorous. As a major intervention, we suggest the construction of other modules to distribute the inflow, with the aim of decrease the hydraulic overload problem, beside the possibility of including a tertiary treatment to decrease the nutrients concentrations. Only after these improvements we can think of ways to optimize the WTP to achieve the design efficiencies and effluent limits.

O estudo teve por finalidade a redução do lodo gerado nos sistema aeróbios mediante recirculação do lodo em excesso, após passar por uma desintegração com ultra-som, ao tanque de aeração de cada reator. Foram utilizados dois reatores seqüenciais aeróbios (A e B) operando em sistema de batelada e com idades do lodo diferentes: 12 e 8 dias respectivamente, e com ciclos de doze horas. Os reatores foram operados em duas etapas. Na etapa inicial, chamada controle, os reatores foram operados por 130 dias sem reciclo do lodo, para se poder avaliar o comportamento e fazer futuras comparações com a etapa posterior, denominada teste. Na etapa controle foram analisados o comportamento da DQO, dos sólidos e dos nutrientes além de serem realizados testes com o ultra-som para a escolha do tempo de exposição e volume de amostra.. O reator A apresentou uma boa remoção de DQO (90,9%), entretanto não apresentou nitrificação completa, chegando apenas na transformação de nitrogênio orgânico a amoniacal. Já a remoção de fósforo foi da ordem de 60%. O reator B também apresentou uma boa remoção de DQO (87,7%) e houve formação de nitrato, embora não completa, e a remoção de fósforo se situou em 57%. Na etapa teste, que durou aproximadamente 90 dias, os reatores foram operados com retorno total do lodo após desintegração com ultra-som. Houve um aumento na DQO afluente devido ao retorno do lodo desintegrado, bem como um aumento nos teores de nitrogênio e fósforo. Houve também um aumento na concentração de sólidos dos reatores, sendo o reator A que apresentou um maior acréscimo. Ambos reatores apresentaram uma mesma eficiência na remoção de DQO (92,0% para o reator A, e 91% para o reator B) se comparado com a etapa controle. Com relação aos nutrientes os reatores apresentaram sensível melhora na nitrificação. O reator A apresentou uma quase completa redução no nitrogênio orgânico, embora não tenha chegado a nitrificação completa. O reator B apresentou uma remoção completa do nitrogênio orgânico. Com relação ao fósforo, a etapa teste apresentou um decréscimo na sua remoção (42% para o reator A e 44% para o reator B). As análises indicaram que a desintegração do lodo e seu retorno ao tanque de aeração não causaram problemas no funcionamento dos reatores, houve uma melhora na nitrificação e não houve uma sensível redução na remoção de fósforo. Comparando com o problema de transporte, tratamento e disposição final de lodo, o estudo de redução de lodos é uma grande alternativa e que merece mais estudos. / The study aims to reduce the sludge generation in aerobic systems by recirculation of the excess sludge after disintegration with a ultrasound set. Two aerobic sequential batch reactors (A and B) were utilized operating with two different sludge ages: 12 and 8 days respectively. The reactors were operated in two stages. In the first stage, called control, the reactors were operated for 130 days, without total sludge recirculation, to promote an assessment and compare with the next stage, called test. In the control stage the behavior of COD, solids and nutrients were analyzed, and tests with ultrasound were performed. The reactor A presented a good COD removal, but not a good nitrification, and a phosphorus removal of 60%. The reactor B presented a good COD removal and a good nitrification, but not complete, and a phosphorus removal of 57%. The test stage the reactors were operated for 90 days, with sludge recirculation after disintegration by ultrasound. There was an increase in influent COD, nitrogen and phosphorus because of sludge recirculation. There was an increase in MLVSS, but reactor A presented a greater increase. Both reactors presented good results in COD removal comparing with control stage. The reactors present a good improvement in nitrification, but not good phosphorus removal regarding to control stage. The analysis showed that sludge disintegration and recirculation to aeration tank not caused any problem in the behavior of the reactors. Comparing to transport, treatment and final disposal problems, the study of sludge reduction is a great alternative that deserves attention.

Advanced wastewater treatment plants must meet permit requirements for organics, solids, nutrients and indicator bacteria, while striving to do so in a cost effective manner. This requires meeting day-to-day fluctuations in climate, influent flows and pollutant loads as well as equipment availability with appropriate and effective process control measures. A study was carried out to assess performance and process control strategies at the Falkenburg Road Advanced Wastewater Treatment Plant in Hillsborough County, Florida. Three main areas for control of the wastewater treatment process are aeration, return and waste sludge flows, and addition of chemicals. The Falkenburg AWWTP uses oxidation ditches where both nitrification and denitrification take place simultaneously in a low dissolved oxygen, extended aeration environment. Anaerobic selectors before the oxidation ditches help control the growth of filamentous organisms and may also initiate biological phosphorus removal. The addition of aluminum sulfate for chemical phosphorus removal ensures phosphorus permit limits are met. Wasting is conducted by maintaining a desired mixed liquor suspended solids (MLSS) concentration in the oxidation ditches. For this study, activated sludge modeling was used to construct and calibrate a model of the plant. This required historical data to be collected and compiled, and supplemental sampling to be carried out. Kinetic parameters were adjusted in the model to achieve simultaneous nitrification-denitrification. A sensitivity analysis found maximum specific growth rates of nitrifying organisms and several half saturation constants to be influential to the model. Simulations were run with the calibrated model to observe relationships between sludge age, MLSS concentrations, influent loading, and effluent nitrogen concentrations. Although the case-study treatment plant is meeting discharge permit limits, there are several recommendations for improving operation performance and efficiency. Controlling wasting based on a target MLSS concentration causes wide swings in the sludge age of the system. Mixed liquor suspended solids concentration is a response variable to changes in sludge age and influent substrate. Chemical addition for phosphorus removal should also be optimized for cost savings. Finally, automation of aeration control using online analyzers will tighten control and reduce energy usage.

<p>Biogas, a mixture of methane and carbon dioxide, is produced in the anaerobic digestion of sewage sludge. After anaerobic digestion, the digested sludge is often allowed to degas for one or two days. This gas is seldom utilised, but if the degassing could be accelerated, utilisation would be easier. Ultrasound can be used as a pretreatment method for waste activated sludge. It has a disintegrating effect on the sludge and causes lysis of bacteria in the sludge. It also speeds up the hydrolysis; the limiting step of anaerobic digestion of waste activated sludge. Ultrasound can be used to degas waterbased liquids. Ultrasonic degassing of sewage sludge has not been examined previously. The present study aims to investigate the effect of ultrasound on waste activated sludge as well as the potential of ultrasound to speed up the degassing of digested sludge. A semi-continuous, lab-scale digestion experiment was performed with four reactors: two receiving untreated sludge and two receiving treated sludge. The effect of the sonicator was 420 W and the treatment time was 6 min, which corresponds to an energy input of 8.4 kWh/m³. Total solids (TS) of the waste activated sludge was ~3.5 %. The ultrasonic treatment caused an increase in gas production of 13 %. There was no difference in methane content. The concentration of filterable chemical oxygen demand (fCOD) increased 375 %, or from 2.8 % to 11 % of total COD. In terms of energy loss/gain the increase in gas production resulted in a loss of 2.7 kWh/m³, i.e. more energy is needed to treat the sludge than the potential energy of the increased gas production. However, if the sludge is thickened to a TS >5 %, a net energy gain should be reached. The effect of ultrasound on the degassing of digested sludge was examined in three barrels. The degassing was measured with and without circulation as well as with ultrasonic treatment. The digested sludge had a gas emission rate of 115 L/(m³ day). No direct burst of gas occurred due to ultrasonic treatment. Over two days more gas was emitted from the barrel equipped with ultrasound, probably due to an induced post-digestion. Thus, ultrasonic pretreatment of waste activated sludge increases the biogas yield. It is inconclusive, whether ultrasonic treatment of digested sludge effects the degassing or not.</p>

In this thesis, the application of molecular microbiology methods to understand wastewater treatment bio-reactions is described. Two different wastewater treatment systems were chosen for the experimental work. Firstly; the activated sludge processes at two different facilities in Sweden (Västerås and Eskilstuna) were investigated and compared in a context where low temperatures can affect the efficiency of the nitrogen removal performance in terms of nitrification. Initially, fluorescence in situ hybridization (FISH) was utilised in order to quantify some of the species involved in ammonia and nitrite oxidation at Västerås, providing information on how the different communities react to decreasing temperatures. Then, the polymerase chain reaction (PCR), cloning-sequencing method was employed in order to study the composition of the ammonia oxidizing bacteria (AOB) community at the same two wastewater treatment plants (WWTPs). Secondly; the potential use of constructed wetlands for the treatment of winery wastewater was studied. High ethanol concentration artificial wastewater with and without inorganic nutrients (nitrates and phosphates) was fed in a set of pilot-scale constructed wetlands. Pollutant removal performance and enzyme activity tests were carried out. Additionally, the bacterial community structure was investigated by means of denaturing gradient gel electrophoresis (DGGE). In the first set of studies it was shown that the AOB population which plays a major role in nitrifying reactors presented a seasonal shift and a higher diversity at Västerås during winter time, while the nitrification performance maintained stable levels and the ammonia removal efficiency increased. Thus, the higher ammonia removal efficiency at Västerås could be related to the diversity of the AOB population composition. Lastly, when constructed wetlands were in focus, the differential effects of ethanol and nutrients over the chemical oxygen demand (COD) removal performance were proven. In fact, the addition of nutrients on one of the experimental wetlands increased the COD (ethanol) removal and supported the maintenance of a bacterial population similar to the control wetland (no ethanol added). In conclusion, both studies proved a strong relationship between process performance (pollution removal) and the dynamics of the bacterial communities involved.

This thesis concerns modeling and control of bilinear systems (BLS). BLS are linear but not jointly linear in state and control. In the first part of the thesis, a background to BLS and their applications to modeling and control is given. The second part, and likewise the principal theme of this thesis, is dedicated to theoretical aspects of identification, modeling and control of mainly BLS, but also linear systems. In the last part of the thesis, applications of bilinear and linear modeling and control to the activated sludge process (ASP) are given.

Anaerobic digestion of excess biological wastewater treatment sludge (WAS) from pulp mills has the potential to reduce disposal costs and to generate energy through biogas production. The organic matter in WAS is highly structured, which normally hinders biogas production. This study investigated three methods of pretreating WAS from two different pulp mills before anaerobic digestion to improve biogas yield and production rate. The three pretreatment methods tested were: i) thermal pretreatment at 170oC, ii) caustic pretreatment at 140oC and pH 12, and iii) sonication at 20 kHz and 1 W/mL. Thermal pretreatment proved to be the most effective, increasing biogas yield by 280% and 50% and increasing production rates 300-fold and 10-fold for the two samples, respectively. Caustic pretreatment showed similar results, but resulted in the formation of soluble non-biodegradable compounds. Sonication was the least effective pretreatment and did not substantially increase biogas yield, but increased biogas production rate.

Anaerobic digestion of excess biological wastewater treatment sludge (WAS) from pulp mills has the potential to reduce disposal costs and to generate energy through biogas production. The organic matter in WAS is highly structured, which normally hinders biogas production. This study investigated three methods of pretreating WAS from two different pulp mills before anaerobic digestion to improve biogas yield and production rate. The three pretreatment methods tested were: i) thermal pretreatment at 170oC, ii) caustic pretreatment at 140oC and pH 12, and iii) sonication at 20 kHz and 1 W/mL. Thermal pretreatment proved to be the most effective, increasing biogas yield by 280% and 50% and increasing production rates 300-fold and 10-fold for the two samples, respectively. Caustic pretreatment showed similar results, but resulted in the formation of soluble non-biodegradable compounds. Sonication was the least effective pretreatment and did not substantially increase biogas yield, but increased biogas production rate.

The effectiveness of partial ozonation of return activated sludge for enhancing denitrification and waste sludge minimization were examined. A pair of nitrifying sequencing batch reactors was operated in either aerobic or alternating anoxic/aerobic conditions, with one control and one ozonated reactor in each set. The amount of solids decreased with the ozone dose. Biomass in the anoxic/aerobic reactor was easier to destroy than in the aerobic one, generating approximately twice as much soluble chemical oxygen demand (COD) by cell lysis. Increased COD favoured production of extracellular polymers in ozonated reactors, enhancing flocculation and improving settling. Floc stability was also strengthened in prolonged operation in alternating treatment, resulting in declined solids destruction. Dewaterability was better in alternating reactors than in aerobic ones indicating that incorporation of an anoxic zone for biological nutrient removal leads to improvement in sludge dewatering. The negative impact of ozonation on dewaterability was minimal in terms of the long-term operation. Ozone successively destroyed indicator estrogenic compounds, contributing to total estrogen removal from wastewater. Denitrification rate improved up to 60% due to additional carbon released by ozonation. Nitrification rates deteriorated much more in the aerobic than in the alternating reactor, possibly as a result of competition created by growth of heterotrophs receiving the additional COD. Overall, ozonation provided the expected benefits and had less negative impacts on processes in the alternating treatment, although after prolonged operation, benefits could become less significant. The alternating anoxic/aerobic reactor achieved twice the nitrification rates of its aerobic counterpart. Higher removal rates of estrogens were associated with higher nitrification rates, supporting the contention that the nitrifying biomass was responsible for their removal. The alternating treatment offered the better estrogen biodegradation. Microbial populations in both reactors were examined with fluorescent in situ hybridization. Dominance of rapid nitrifiers like Nitrosomonas and Nitrobacter (79.5%) in the alternating reactor, compared to a dominance of slower nitrifiers like Nitrosospira and Nitrospira (78.2%) in the aerobic reactor were found. The findings are important to design engineers, as reactors are typically designed based on nitrifiers’ growth rate determined in strictly aerobic conditions. / October 2008

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.