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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Effectiveness of Engineered and Natural Wastewater Treatment Processes for the Removal of Trace Organics in Water Reuse

Cheng, Long, Cheng, Long January 2017 (has links)
Due to their potential health impact on human beings and ecosystems, persistent trace organic compounds (TOrCs) have aroused concern from both the public and professionals. In particular, the discharge of pharmaceuticals, endocrine disrupters, disinfection byproducts and other TOrCs from wastewater treatment plants into the environment is an area of extensive current research. This work studies the fate and treatments of TOrCs, with emphases on advanced oxidation processes (AOPs). This work presents predicted removal efficiencies of a variety of engineered and natural processes for 55 frequently encountered TOrCs in treated wastewater, based on previously reported data and using existing predictive models. Correlations between physicochemical and biological properties of TOrCs and treatment performance were explored. Removal of TOrCs in all processes investigated in this study was found to be sensitive to matrix effects. Heuristic guidelines for selection of sequenced treatment processes for TOrCs management were established. A field reconnaissance of natural process of TOrCs was conducted by analyzing the occurrence and fate of a suite of TOrCs, as well as estrogenic activity in water and sediments in the Santa Cruz River, an effluent-dependent stream in Tucson, Arizona. Some TOrCs, including contributors to estrogenic activity, were rapidly attenuated with distance of travel in the river. TOrCs that have low biodegradability and low octanolwater partitioning coefficients were less removed. Results of independent experiments indicated potential indirect photodegradation of estrogenic compound by reactive species generated from photolysis of effluent organic matter. Utilizing advanced oxidation processes (AOPs) as tertiary water and wastewater treatment is an option to prevent discharge of TOrCs into the environment. Compared to conventional AOPs, the ability of generating hydroxyl radicals (•OH) without additional doses of hydrogen peroxide (H2O2) or ozone makes ultraviolet (UV) photolysis of ferric hydroxo complexes a novel AOP, especially in acidic environments. A Fe(III)/UV254 kinetic model, which combines Fenton-like mechanism, and photolyses of Fe3+, FeOH2+ and H2O2 was proposed and experimentally validated to predict Fenton-like and H2O2 direct UV254 photolysis scenarios, individually. Nevertheless, the model underestimated the ferrous ion development during Fe(III)/UV254 photolysis, perhaps due to the overprediction of the oxidation of Fe2+ by •OH. The UV/H2O2 AOP was also studied in this work. A predictive kinetic model was developed to evaluate process efficiency of oxidation of p-cresol by UV/H2O2 photolysis based on a complete reaction mechanism, including reactions of intermediates with •OH. Results of this study highlight the significance of consideration of radical scavenging effects by the byproducts from oxidation of organic matter in model prediction performance.
2

Adsorção de fósforo em substrato natural visando o desenvolvimento de tecnologia verde para o tratamento terciário de efluentes

Vieira, Bruna January 2016 (has links)
Orientadora: Profa. Dra. Lúcia Helena Gomes Coelho / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Ciência e Tecnologia Ambiental, 2016. / Considerando a situação atual dos recursos hídricos, cuja qualidade vem sendo comprometida pela poluição causada, principalmente, pelo descarte inadequado de efluentes não tratados ou ineficientemente tratados, evidencia-se a necessidade de se criar técnicas e processos que permitam tratar o efluente de modo eficiente, de forma mais econômica e sustentável, cujos resíduos finais sejam de mais fácil disposição ou reutilização, visando a minimização dos impactos ambientais do despejo de efluentes e dos processos de tratamento de águas em si. O presente trabalho avaliou o potencial da utilização de conchas de moluscos (Venerupis pulastra) como substrato natural na remoção de fósforo inorgânico dissolvido (ortofosfato) em meio aquoso com vistas ao desenvolvimento de tecnologia de tratamento terciário de efluentes de baixo custo e baixo impacto ambiental. Foram realizados ensaios em batelada que consistiram da adição de 0,5 g a 2,0 g do substrato natural (previamente preparado) em 15 mL de solução de concentração conhecida de fósforo (0,5 mg L-1) sob agitação em mesa agitadora por períodos de tempo estabelecidos. Foi avaliada a influência dos parâmetros: tempo de detenção hidráulica substrato/solução, pH da solução, quantidade de substrato, granulometria do substrato e velocidade de rotação da mesa agitadora orbital na eficiência de remoção de ortofosfato em amostras sintéticas de concentração conhecida. Todos os parâmetros foram variados no sistema utilizando abordagem univariada e multivariada. Para os testes com abordagem univariada, os resultados de eficiência de remoção de fósforo variaram de 14% a 68%, evidenciando o potencial de adsorção do substrato e a importância dos parâmetros estudados no desempenho do processo. Com a análise destes dados, foi possível fazer um melhor delineamento dos parâmetros e níveis dos parâmetros a serem utilizados nas análises com abordagem multivariada. Os resultados de eficiência de remoção para as análises com abordagem multivariada alcançaram valores entre 50% e 98%, apontando que as condições utilizadas nesta etapa do experimento (parâmetros e níveis) mostraram-se muito mais favoráveis ao processo de adsorção de fósforo pelo substrato. Os testes realizados com materiais de diferentes conchas (lotes e espécies diferentes) apontaram resultados semelhantes nas três amostras estudadas, mantendo eficiência acima de 96%. Por fim, foram realizados ensaios aplicando a técnica em duas diferentes amostras de efluentes provenientes de tratamento secundário (que possui como objetivo a remoção de matéria orgânica do efluente), sendo eles: biorreator de membranas submersas (BRM), com concentração inicial de fósforo (Ci) de 3,9 mg L-1) e lagoas de estabilização (Ci = 0,5 mg L-1). Obteve-se 91% de eficiência de remoção de fósforo para a amostra do BRM e 86% de eficiência de remoção para a amostra de lagoas de estabilização. Verificou-se eficiência elevada para remoção de fósforo nestas amostras, entretanto, com resultados abaixo dos encontrados em amostras sintéticas na mesma condição, apontando possíveis interferências das substâncias existentes na matriz do efluente no processo de adsorção. / Considering the current situation of water resources, whose quality has been compromised by pollution caused mainly by improper disposal of untreated effluents or ineffectively treated, highlights the need to create techniques and processes able to treat effluent, in an efficiently, economically and sustainably way, and its final waste able to be easier disposal or reuse, in order to minimize the environmental impact of the discharge of effluents and water treatment process itself. This present research proposes to evaluate the potential of shellfish shell (Venerupis pulastra) as a natural substrate in the removal of inorganic phosphorus (orthophosphate) from water, aiming the development of a low-cost and environmentally friendly tertiary wastewater treatment technology. The first step was the acquisition and preparation of the shellfish shell substrate. After that, laboratory tests were conducted batchwise, using 15ml of aqueous solutions containing 0.5mg/L of phosphorus with addition of the natural substrate (varying mass from 0.5g to 2g) under shaken for a set time. It was evaluated the influence of the parameters: contact time with the substrate and the solution, pH of the solution, amount of substrate mass, the substrate particle size and the rotational speed of the orbital shaker in the efficiency of orthophosphate removal from the synthetic sample of known concentration. All parameters were varied in the system using univariate and multivariate (design of experiments - DOE) approach. For the univariate approach tests, the phosphorus removal efficiency results ranged from 14% to 68%, showing the adsorption of the substrate potential and the importance of the parameters studied on the process performance. The results provided by univariate approach were used to organize a more specific delineation of the parameters and levels to be used in the analysis with multivariate approach. The removal efficiency results for analysis varying parameters with multivariate approach reached values between 50% and 98%, showing that the conditions used in the design of experiment (parameters and levels) proved to be more favorable to the phosphorus adsorption process. The tests with different materials (different lots and species of shellfish) showed similar results in the three samples studied, maintaining the removal efficiency of orthophosphate above 96%. Finally it was held experiments with two samples of effluents from different secondary treatment systems. The efficiency results for removal were 91% for the effluent from the bioreactor of submerged membranes (BRM) and 86% for effluent from secondary treatment from stabilization lagoons. There was high efficiency for removing phosphorus in these samples, however, with results below those found in synthetic samples in the same condition, pointing out possible interference of substances in the effluent matrix in the adsorption process.

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