During ferrochrome (FeCr) production, three types of generic chromium (Cr) containing wastes are generated, i.e. slag, bag filter dust (BFD) and venturi sludge. The loss of these Cr units contributes significantly to the loss in revenue for FeCr producers. In this study, the liberation of Cr units was investigated utilising two case study waste materials, i.e. BFD from a semi-closed submerged arc furnace (SAF) operating on acid slag and the ultrafine fraction of slag (UFS) originating from a smelter operating with both open and closed SAFs on acid slag. A detailed material characterisation was conducted for both case study materials, which included particle size distribution, chemical composition, chemical surface composition and crystalline content. Cr liberation was achieved utilising two methods, i.e. aqueous ozonation and the advanced oxidation method. Various advanced oxidation processes could be applied. However, the advanced oxidation processes considered in this study was the use of gaseous ozone (O3) in combination with hydrogen peroxide (H2O2). Controlling parameters such as the influence of pH, ozonation contact time, waste material solid loading, gaseous O3 concentration and temperature on Cr liberation were investigated for the aqueous ozonation process. The influence of pH, volume H2O2 added and the method of H2O2 addition were considered for the advanced oxidation process. Results indicated that with aqueous ozonation, limited Cr liberation could be achieved. The maximum Cr liberation achieved was only 4.2% for BFD by varying the process controlling parameters. The Cr liberation for UFS was significantly lower than that of the BFD. The difference in the results for the two waste materials was attributed to the difference in characteristics of the materials. The Cr content in BFD was mostly related to chromite and/or altered chromite particles, while the Cr content of the UFS was mostly related to FeCr particles. It is possible that the Cr(III) present in the chromite and/or partially altered chromite might be more susceptible to oxidation to Cr(VI) than the metallic Cr(0) present in the FeCr. During ozonation, aqueous O3 spontaneously decomposes to form hydroxyl (OH•) radicals, which are very strong oxidants in water. The above-mentioned Cr liberation observed was related to the formation of the OH• radicals during the spontaneous decomposition of aqueous O3. This was indicated especially by enhanced Cr liberation at higher pH values, which was attributed to the acceleration of the spontaneous decomposition to OH• radicals at higher pH levels. The advanced oxidation method gave significantly higher Cr liberation results for both case study materials considered, achieving Cr liberations of more than 21%. The advance oxidation processes improve normal oxidation methods. In this study, the H2O2 used in combination with O3 enhanced the formation of the OH• radicals that are responsible for the oxidation of Cr. The Cr liberation levels achieved are possibly not high enough to be feasible for industrial purposes. However, a further investigation of the advanced oxidation process could optimise the process to yield even higher Cr liberation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

During ferrochrome (FeCr) production, three types of generic chromium (Cr) containing wastes are generated, i.e. slag, bag filter dust (BFD) and venturi sludge. The loss of these Cr units contributes significantly to the loss in revenue for FeCr producers. In this study, the liberation of Cr units was investigated utilising two case study waste materials, i.e. BFD from a semi-closed submerged arc furnace (SAF) operating on acid slag and the ultrafine fraction of slag (UFS) originating from a smelter operating with both open and closed SAFs on acid slag. A detailed material characterisation was conducted for both case study materials, which included particle size distribution, chemical composition, chemical surface composition and crystalline content. Cr liberation was achieved utilising two methods, i.e. aqueous ozonation and the advanced oxidation method. Various advanced oxidation processes could be applied. However, the advanced oxidation processes considered in this study was the use of gaseous ozone (O3) in combination with hydrogen peroxide (H2O2). Controlling parameters such as the influence of pH, ozonation contact time, waste material solid loading, gaseous O3 concentration and temperature on Cr liberation were investigated for the aqueous ozonation process. The influence of pH, volume H2O2 added and the method of H2O2 addition were considered for the advanced oxidation process. Results indicated that with aqueous ozonation, limited Cr liberation could be achieved. The maximum Cr liberation achieved was only 4.2% for BFD by varying the process controlling parameters. The Cr liberation for UFS was significantly lower than that of the BFD. The difference in the results for the two waste materials was attributed to the difference in characteristics of the materials. The Cr content in BFD was mostly related to chromite and/or altered chromite particles, while the Cr content of the UFS was mostly related to FeCr particles. It is possible that the Cr(III) present in the chromite and/or partially altered chromite might be more susceptible to oxidation to Cr(VI) than the metallic Cr(0) present in the FeCr. During ozonation, aqueous O3 spontaneously decomposes to form hydroxyl (OH•) radicals, which are very strong oxidants in water. The above-mentioned Cr liberation observed was related to the formation of the OH• radicals during the spontaneous decomposition of aqueous O3. This was indicated especially by enhanced Cr liberation at higher pH values, which was attributed to the acceleration of the spontaneous decomposition to OH• radicals at higher pH levels. The advanced oxidation method gave significantly higher Cr liberation results for both case study materials considered, achieving Cr liberations of more than 21%. The advance oxidation processes improve normal oxidation methods. In this study, the H2O2 used in combination with O3 enhanced the formation of the OH• radicals that are responsible for the oxidation of Cr. The Cr liberation levels achieved are possibly not high enough to be feasible for industrial purposes. However, a further investigation of the advanced oxidation process could optimise the process to yield even higher Cr liberation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

This research involved an investigation of the application and reaction mechanisms of UV/H₂O₂ for the simultaneous removal of regulated halogenated disinfection byproducts (DBPs) and odorous aldehydic algal byproducts in the presence of geosmin and 2-methylisoborneol, which are earthy-musty odorants that commonly occur in drinking water. UV/H₂O₂ is an expensive advanced oxidation process that is used to successfully control geosmin and 2-methylisoborneol. The aqueous oxidation of odorous aldehydes and halogenated DPBs were compared to that of the earthy-musty odorants and the changes to the sensory properties of the drinking water were examined. Geosmin, 2-methylisoborneol, heptadienal, decadienal, and nonadienal, hexanal, and the two most prevalent classes of DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs) were oxidized by UV photolysis alone and the UV/H₂O₂ process with 6 mg/L H₂O₂ and realistic ng/l to μg/L concentrations of the test compounds. The di-, and tri-brominated THMs and HAAs were substantially (80-99%) removed by direct UV photolysis mechanism at the same UV/H₂O₂ dose required for removing 95% of geosmin and 65% of 2-methylisoborneol with faster reaction rates for the more bromine substituted compounds. The C-Br bond cleavage is the first step of brominated HAAs degradation by UV photolysis, and followed by either of two second steps: reaction with oxygen producing peroxyl radical or interaction with water molecule causing O-H insertion/H-Br elimination. Trichloromethane and mono-, di-, and tri-chlorinated HAAs were not substantially removed under the same conditions used for the brominated compounds. The principal removal mechanism was by the reaction with hydroxyl radical for the UV/H₂O₂ process. The second order reaction rate constants were on the order of 10⁶ - 10⁸ M⁻¹ s⁻¹ with faster reaction rates for the less chlorine substituted compounds. Based on the reaction rates, hydrogen and halogen ion balance, and isotope effect, both hydrogen abstraction and electron transfer reaction were involved in the first steps of the chlorinated HAA degradation. Three odorous aldehydes - heptadienal, decadienal, and nonadienal - were removed faster than geosmin or 2-methylisoborneol, and direct UV photolysis was the principal reaction mechanism for the removal of these unsaturated aldehydes. Hexanal was poorly removed. In sensory tests, new odors such as sweet or chalky odors were produced while the concentration and initial odor intensity of these fishy/grassy-smelling aldehydes were reduced with increasing exposure time to UV/H₂O₂. Carbonyl compounds were detected as products of the UV photolysis of nonadienal. These carbonyls were not removed by further UV irradiation, which was thought to be partially related with production of new odors. The results indicate that the UV/H₂O₂ is effective to control both odorous compounds and brominated DBPs. This process can be seasonally applied to control both contaminants especially, in the warm summer when both odorants and DBPs have their higher concentrations. Removal of brominated DBPs can be a significant addition to water utilities that have difficulty in meeting regulatory levels for these highly toxic compounds. The result on the removal of odorous aldehydes indicate that new types of odors were produced from the oxidation of odorous aldehydes suggesting sensory test coupled with chemical analysis should be considered in designing oxidation process to control recalcitrant odorants. / Ph. D.

Submitted by JOSIANE SANTOS DE OLIVEIRA (josianeso) on 2017-05-25T11:43:55Z No. of bitstreams: 1 Alisson Schons_.pdf: 2733792 bytes, checksum: 704c4ce2631dfdbe7af1fc3c3e324404 (MD5) / Made available in DSpace on 2017-05-25T11:43:56Z (GMT). No. of bitstreams: 1 Alisson Schons_.pdf: 2733792 bytes, checksum: 704c4ce2631dfdbe7af1fc3c3e324404 (MD5) Previous issue date: 2016-02-24 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / UNISINOS - Universidade do Vale do Rio dos Sinos / O lixiviado de aterro sanitário tem se caracterizado pela alta concentração de matéria orgânica recalcitrante, nitrogênio amoniacal e compostos tóxicos. Compostos orgânicos recalcitrantes são raramente removidos por processos tradicionais de tratamentos de efluentes, o que dificulta o atendimento aos padrões de lançamento de efluentes. Da mesma forma, o descarte do esgoto doméstico gerado pelas comunidades precisa também de tratamentos prévios para não impactar o meio ambiente. Devido às características do esgoto doméstico, com baixas concentrações de matéria orgânica carbonácea e cor em relação ao lixiviado, vem permitindo que o tratamento combinado desses efluentes seja uma alternativa viável. Diante desse quadro, este trabalho visou à avaliação do tratamento combinado de esgoto doméstico da estação de tratamento de efluentes (ETE) da Unisinos e lixiviado bruto do aterro sanitário de São Leopoldo, utilizando ozônio (O3) como agente oxidante. Os efluentes foram tratados na unidade experimental composta por um reservatório com capacidade de até 500L e um reator cilíndrico de PVC com 250 mm de diâmetro e 2,20 m de altura, operando com fluxo ascencional, totalizando um volume de trabalho de 108 L e preenchido em 2/3 do seu volume total com Anel Pall de 1,5”. Realizaram-se três ensaios em bateladas, com duração de cinco horas e três ensaios com duração de duas horas, com diferentes produções de O3 de 8,9; 9,6 e 10,5 g de O3.h-1, aplicados à mistura de 2% de lixiviado de aterro sanitário (LAS) ao esgoto doméstico (2 L de LAS e 158 L de esgoto). Cada ensaio foi realizado em duplicata, sendo monitorados os seguintes parâmetros: Demanda Química de Oxigênio, Demanda Bioquímica de Oxigênio, Cor Aparente e Verdadeira, Turbidez, pH e calculada as taxas de utilização e de perda de O3. Os resultados evidenciaram que o tratamento por O3 pode ser uma alternativa de pré-tratamento de efluentes, obtendo remoções médias de DQO, DBO, CA, CV e Turbidez de até 46%, 51%, 86%, 86% e 81% respectivamente em cinco horas de ensaio e remoções médias de até 23%, 48%, 78%, 76% e 58% respectivamente em duas horas de ensaio. As maiores taxas de remoções foram alcançadas nos ensaios com maiores vazões de O2 e produções de O3 e nas duas primeiras horas de ensaio. Só foi possível o atendimento aos padrões de lançamentos de efluentes exigidos pela legislação vigente, nos ensaios com duração de cinco horas e com a maior produção de O3 e vazão de O2. O sistema de tratamento também contribuiu para uma melhora na biodegradabilidade do efluente se analisada a relação DBO/DQO e cor. Quanto as taxas de utilização e de perda de O3, verificou-se que a maior quantidade consumida de O3, ocorreu para os parâmetros indicativos de matéria orgânica e para os ensaios com a menor produção de O3. / Landfill leachate has been characterized by the high concentration of recalcitrant organic matter, ammoniacal nitrogen and toxic compounds. Recalcitrant organic compounds are rarely removed by traditional effluent treatment processes. In addition, the treatment of the leachate is colloquial to meet the discharge standards of the effluent. Likewise, the domestic sewage disposal generated by the communities also needs previous treatments to avoid impacts on the environment. Due to the characteristics of domestic sewage, with low concentrations of organic carbon in relation to the leachate, it has allowed the combined treatment of these effluents to be a viable alternative. In view of this situation, this work had the objective of evaluating the combined treatment of domestic sewage of (ETP) and the raw leachate of the San Leopoldo landfill using ozone (O3) as an oxidizing agent. Three batch trials were carried out with a scheduled duration of five hours and three trials lasting two hours, with different yields of O3 of 8.9, 9.6 and 10.5 g of O3.h-1, applied to the mixture Of 2% of landfill leachate) For domestic sewage (2L of LAS and 158L of sewage). Each assay was performed in duplicate and the following parameters were monitored: Oxygen Chemical Demand, Biochemical Oxygen Demand, Apparent and True Color, Turbidity, pH and calculated O3 utilization and loss rates. The results showed that the treatment with O3 can be an excellent alternative of pretreatment of effluents, obtaining average removals of COD, BOD, CA, CV and Turbidity of up to 46%, 51%, 86%, 86% and 81 % Respectively. Average test and removal hours of up to 23%, 48%, 78%, 76% and 58%, respectively, in two hours of testing. The highest removal rates were obtained in the tests with higher flows of O2 and yields of O3 and in the first two hours of the test. It was only possible to meet the effluent release standards required by current legislation, in trials with a duration of five hours and with the highest production of O3 and O2. The treatment system also contributed to an improvement in the biodegradability of the effluent if the BOD/COD ratio was analyzed. As for the rates of use and loss of O3, it was verified that the highest amount of O3 occurred for the parameters indicative of organic matter and for the tests with lower production of O3. The higher the O3 production, the higher the O3 loss and the greater oxidant loss may have been due to volatilization in the effluent accumulation reservoir, since there was no gas loss due to Off-gas and the method used Not Detected The residual ozone.

This PhD thesis investigated solid and liquid waste treatment systems for Sureclean, a waste Management company based in the North of Scotland. Sureclean receives a diverse range of waste streams and the increasing need for sustainable development as well as stringent environmental legislation motivated this research to develop an integrated waste treatment system. Waste characterisation was conducted using a range of analytical instrumentation to identify the TPH, COD, heavy metals content, TOC, and particle size of Sureclean waste streams. From there, four treatment systems were investigated utilising Sureclean waste streams: mechanical separation, chemical treatment, electro-coagulation and the advanced oxidation process. Laboratory and field trials were conducted using these different treatment techniques and the analysis was performed to verify the treatment results. The result of these trials led to the development of four modular waste treatment units, that form the outcome of this research: the Sureclean Water Treatment System (SWTS), a filtration based mechanical separation system was shown to reduce the TSS, BOD and TOC content of an oily wastewater; the Sureclean Sludge Separation System (SSSTS), a chemical-enhanced filtration based system was demonstrated to reduce 52.6 % of the sewage sludge volume; the Sureclean Electro-coagulation Water Treatment System (SEWTS), a system that agglomerates colloid particles and demulsifies oil removed 99.9 % of TPH from Sureclean interceptor effluent; and the Sureclean Advanced Water Treatment System (SAWTS), an advanced oxidation process which was demonstrated to reduce the TPH of a contaminated groundwater collected from an ex-gas work. The treated effluent could be discharged to Sureclean interceptor. The four treatment units developed in this research expanded Sureclean waste treatment capabilities and an integrated system was developed to treat different waste streams and to improve the treatment efficiency thus increasing the revenue and future waste stream options for Sureclean.

No processo UV/H2O2, oxidar o substrato a CO2 e água resulta em um elevado consumo de H2O2. Então, esse processo tem sido proposto como um pré-tratamento para reduzir a toxicidade a níveis seguros para o tratamento biológico posterior. Por essa razão, é necessário estudar o progresso da reação, pois a toxicidade de alguns intermediários formados durante a oxidação pode ser mais elevada que a do composto inicial. Neste trabalho, os experimentos foram realizados em um reator tubular fotoquímico, contendo em seu eixo uma lâmpada de vapor de mercúrio de baixa pressão, conectado a um tanque de recirculação. O processo UV/H 2O2 é aplicado no tratamento de água contendo fenol (50500mg C.L-1). Os resultados demonstraram que o principal produto da oxidação primária é o catecol, indicando que a hidroxilação ocorre predominantemente na posição orto. A abertura do anel aromático leva à formação de ácidos orgânicos, o que explica a diminuição do pH durante a reação. Foram identificados os seguintes ácidos: fórmico, oxálico, maleico e malônico. Na etapa seguinte desse trabalho, dois modelos cinéticos foram desenvolvidos. Os modelos foram baseados nas reações químicas e fotoquímicas iniciadas pelos radicais hidroxila gerados pela fotólise do peróxido de hidrogênio. Foram utilizados os valores encontrados na literatura para os parâmetros fotoquímicos e constantes cinéticas das reações fotoquímicas. Os resultados experimentais foram utilizados para estimar as constantes cinéticas das reações que envolvem os compostos aromáticos. No primeiro modelo foram contempladas todas as reações fotoquímicas envolvidas e, no segundo, apenas as consideradas mais significantes. Os resultados das simulações considerando os parâmetros ajustados mostraram uma melhor concordância com os dados experimentais para o primeiro modelo. As constantes cinéticas deste modelo para as reações nas quais o fenol é oxidado a catecol (k14) e hidroquinona (k15) foram 2,60x108L.mol-1.s-1 e 1,03x108L.mol-1.s-1, respectivamente. As constantes cinéticas para a oxidação do catecol (k17) e hidroquinona (k18) encontradas foram 1,41x108L.mol-1.s-1 e 2,02x108L.mol-1.s-1, respectivamente. Também foi observada elevada correlação entre as constantes k14 e k17 e entre k15 e k18. / In the UV/H2O2 process, the oxidation of the substrate to CO2 and water results in high H2O2 consumption. Due to this fact the process has been proposed as a pretreatment to reduce toxicity to safe levels prior to biological treatment. Thus, it is necessary to study the reaction progress because some intermediate compounds may be more toxic than the initial compound. In the present study experiments were carried out in a lab-scale tubular photochemical reactor with a low-pressure mercury vapor lamp placed in its axis, connected to a recirculation tank. The UV/H2O2 process was applied to the degradation of an aqueous solution containing phenol as a model pollutant (concentration range: 50-500mg.L-1). The experimental results indicated that orto-hydroxylation (catechol formation) was predominant. The cleavage of the aromatic ring resulted in the production of organic acids, which caused the pH decrease over the reaction time. The following acids were detected: formic, oxalic, maleic and malonic. The experimental results were used to estimate kinetic rate constants for the reactions involving aromatic compounds according to two kinetic models based on chemical and photochemical reactions, initiated by hydrogen peroxide photolysis to produce hydroxyl radical. Numerical values of chemical reaction rate constants and photochemical parameters were taken from literature. The first model considered all photochemical while the second model considered the most significant ones. The parameter fitting results showed better agreement with experimental values based on the first model. The resulting values for the rate constants according to this model were as follows: 2.60x108L.mol-1.s-1 for phenol oxidation to catechol, and 1.03x108L.mol-1.s-1 for phenol oxidation to hydroquinone by hydrogen peroxide. The reaction rate constants for the oxidation of catechol, and hydroquinone by hydrogen peroxide are 1.41x108L.mol-1.s-1 and 2.01x108L.mol-1.s-1, respectively. A high correlation was observed between constants k14 and k17, and between k15 and k18.

O efluente fenólico em estudo apresenta a relação DBO5/DQO (Demanda Bioquímica de Oxigênio/ Demanda Química de Oxigênio) igual a 0,15, ou seja caracteriza-se por ser um efluente não biodegradável. No tratamento inicial do efluente utilizou-se ozônio, na presença do sal de ferro II proveniente da solução de sulfato ferroso heptaidratado 0,82 mol. L-1 e do peróxido de hidrogênio , que possui a finalidade catalítica na formação dos radicais hidroxilas, com alto poder de oxidação da matéria orgânica. Nesta etapa foi estudado a união dos processos oxidativos O3/UV e Foto-Fenton, Foram tratados 3 L do efluente fenólico in natura em um reator fotocatalítico com lâmpada ultravioleta. Em todos os experimentos o pH e a temperatura do meio reacional foram controlados. Os experimentos foram executados segundo um planejamento de Taguchi L16, no qual a variável entrada de maior importância para a degradação da matéria orgânica foi o peróxido de hidrogênio. As variáveis respostas analisadas foram a concentração do Carbono Orgânico Total, Demanda Química de Oxigênio e Fenóis Totais. No planejamento de Taguchi L16 foram selecionadas as variáveis significativas para o processo de degradação do efluente fenólico, a fim de serem otimizadas através do Método de Superfície de Resposta (MSR Foto-Fenton e O3/UV). O método de otimização MSR Foto-Fenton foi eficiente na degradação do composto fenólico, sendo assim a melhor condição experimental da planilha de otimização foi a de número 10 e corresponde a uma redução de COT= 54,68%, DQO=78,73% e Fenois Totais= 98,1%. Os parâmetros controlados do processo para essa condição foram: pH=3, temperatura de 30 ºC, potência ultravioleta de 28 W e reagente Fenton (H2O2= 48,3g e Fe+2 =5,95g), que corresponde a relação mássica H2O2 /Fe+2 igual a 8. / The phenolic effluent in this study has the rate DBO5/DQO (Biochemical Oxygen Demand / Biochemical Oxygen Demand) equal to 0.15, which is characterized by an effluent to be non-biodegradable. In the initial treatment of phenol was used ozone in the presence of iron salt II from the solution of ferrous sulfate heptahydrate 0.82 mol. L-1 and hydrogen peroxide, which has the purpose in the catalytic formation of hydroxyl radicals with high oxidation power of organic matter. In this stage, was studied the union of the oxidative process O3/UV and Photo-Fenton. The effluent was treated about 3 L about in a photocatalytic reactor with UV lamp. In all experiments, the pH and temperature of the reaction medium were control. The experiments are being carried out to a Taguchi L16 design, in which the input variable of greatest importance to the degradation of organic matter was hydrogen peroxide. The response variable analyzed was given by the concentration of Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) and Total Phenols (FT). In planning Taguchi L16 significant variables were selected for the degradation process of phenolic wastewater in with purpose of to be optimized by Response Surface Method (RSM Photo-Fenton and O3/UV). The optimization method was efficient photo-Fenton degradation of phenolic compound, so the best experimental condition spreadsheet optimization was the number 10 and corresponds to a reduction of TOC = 54.68%, COD = 78,73% and Total Phenols= 98.1%. The controlled process parameters for this condition were: pH = 3, temperature of 30 ° C, power of 28 W ultraviolet and Fenton reagent (H2O2= 48,3g and Fe+2 = 5,95g), corresponding to mass ratio H2O2 / Fe +2 = 8.

O processo de adsorção por carvão ativado é uma técnica muito aplicada para tratamento de efluentes. Porém o tratamento que envolve adsorção não é um sistema completo, pois há a necessidade da destruição dos compostos que foram imobilizados na superfície do carvão. Frente a esse problema, métodos alternativos de regeneração de carvão ativado são investigados. Os processos Fenton e foto-Fenton são considerados tecnologias promissoras de tratamento de efluentes, e foram testados para regenerar o carvão ativado. Este trabalho objetiva estudar a adsorção de fenol em carvões ativados (CAs) e a consecutiva regeneração in-situ do carvão pela oxidação de (foto-) Fenton. Duas operações diferentes foram realizadas: 1) sistema de batelada, a fim de investigar a influência das concentrações de Fe2+ e H2O2; 2) adsorção contínua em leito fixo, seguido de circulação em batelada dos reagentes de Fenton pelo leito de CA saturado, para examinar a eficiência do processo real. Foram estudados dois tipos de carvão ativado: CA L27 (meso e microporoso) e CA S23 (somente microporoso). No reator de batelada as melhores condições encontradas para a mineralização do poluente no sistema Fenton homogêneo não são as melhores para a regeneração do CA: foi observada uma redução contínua da capacidade de adsorção do L27 após 3 oxidações, devido à redução tanto da massa do CA quanto da área superficial. Uma maior concentração de Fe2+ e menor concentração de H2O2 (2 vezes a estequiometria) levou a uma recuperação de 50% da capacidade de adsorção inicial em pelo menos 4 ciclos consecutivos para o L27, enquanto que cerca de 20% para o S23. No processo consecutivo de adsorção contínua/oxidação de Fenton em batelada, a eficiência de regeneração atinge de 30% a 40% para o L27 após dois ciclos independente da concentração da alimentação e menos de 10% para o S23. O processo foto-Fenton realizado para o L27 levou à quase completa mineralização e aumentou a recuperação da capacidade de adsorção do CA (56% após dois ciclos). / The adsorption process by active carbon is a technique applied extensively for wastewater treatment. However the tertiary treatment involving adsorption is not a complete system, since there is a need of destruction of the compounds that were immobilized on the carbon surface. In face of this problem, some alternative regeneration methods of active carbon are investigated. Fenton and photo-Fenton processes have been considered promising technologies for wastewater treatment and have been tested to regenerate the AC. The purposes of this study are the adsorption of phenol on activated carbons (ACs) and the consecutive in-situ regeneration of carbon by (photo-) Fenton oxidation. Two different operations have been carried out: 1) batch procedure in order to investigate the influence of Fe2+ and H2O2 concentrations; 2) continuous fixed bed adsorption, followed by a batch circulation of the Fentons reagent through the saturated AC bed, to examine the efficiency of the real process. Two different activated carbons have been also studied: a both micro- and mesoporous AC (L27) and an only microporous one (S23). In the batch reactor the best conditions found for pollutant mineralization in the homogeneous Fenton system are not the best for AC regeneration: a continuous reduction of adsorption capacity of L27 is observed after 3 oxidations, due to the decrease of both AC weight and surface area. Higher concentration of Fe2+ and lower concentration of H2O2 (2 times the stoechiometry) lead to a 50% recovery of the initial adsorption capacity during at least 4 consecutive cycles for L27, while about 20% for S23. In the consecutive continuous adsorption/batch Fenton oxidation process, the regeneration efficiency reaches 30% to 40% for L27 after two cycles whatever the feed concentration and less than 10% for S23. A photo- Fenton test performed on L27 shows almost complete mineralization (contrary to dark Fenton) and further improves recovery of AC adsorption capacity although not complete (56% after two cycles).

Water recycling by membrane treatment is widely accepted as a leading alternative water source. This separation process creates a concentrated stream (called concentrates), containing most of the pollutants in 10%-20% of the flow; and a treated water stream. As nitrogen is a major concern, environmental regulations have become more stringent, requiring additional treatment to meet effluent standards. Other concerns include organic contaminants and potential production of halogenated organics if disinfection of the reject was applied. One option to address the problem of dissolved organic nitrogen and carbon is advanced oxidation. This oxidation could lead to degradation of refractory organic materials, which are poorly removed in conventional treatment. This project aims to evaluate treatment extent and cost of alternatives for organic (particularly nitrogen) removal in reject water addressing the following research gaps: (i) identifying the key organic pollutants present in the concentrated stream, (ii) the effectiveness and optimisation of coagulation, ion exchange and advanced oxidation; (iii) apparent cost of the different treatment methods. The untreated reverse osmosis concentrates were collected from two treatment plants:- Luggage Point, and Bundamba, both near Brisbane, Queensland, Australia. The first contains more colourful of organics than the second plant. Stirred cell fractionation with ultrafiltration membranes was used to characterise the removed key pollutants, as it offers better accuracy and reproducibility compared to centrifugation fractionation. Fluorescence spectral was used to monitor and identify specific organic compounds. The largest fraction was smaller sized <1kDa. This is probably small humic substances and fulvic acids, as indicated by Excitation Emission Matrix (EEM) analysis. A smaller portion of soluble microbial products (SMPs) also contributes to the concentrates. Bundamba contains large non coloured organics including organic nitrogen with elevated ammonia-N. In contrast, Luggage Point has higher colour, inorganic carbon and conductivity with less ammonia-N. Advanced Oxidation Process (AOP) was the most effective treatment method (high removal of organics, e.g. 55% COD of initial), followed by magnetised ion exchange (MIEX) and coagulations. For UV/H2O2 AOP, the optimal operating condition 400mg.L-1 H2O2 and 3.1kWh.m-3 energy input resulted in organics removals up to 55% with complete decolourisation. The effective reduction was found in all size ranges, preferably in >1kDa. Low inorganic carbon and salinity in Bundamba may allow better overall oxidation rates. MIEX also performed better in Bundamba with organic removals up to 43% and 80% decolourisation at the optimum resin dose of 15mL.L-1. Removal was preferential in size range of >3kDa, with more proportional percentage for decolourisation. Similarly, ferric coagulation removed a wider size range of organics. Further, ferric achieved better organic removal in Luggage Point with up to 49%. At the same molar dose (1.5mM), ferric is superior to alum, especially in Bundamba where there were less hydrophobic compounds according to EEM. Alum is poor for treatment of high organics with less coloured water. MIEX with an operational cost (chemicals and power only) of $0.14-$0.20.m-3 treated water seemed to be the most effective treatment overall. The resin achieved better results with a slightly higher cost than coagulation, and had a lower environmental impact due to reduced sludge production. AOP offers better treatment, but at a higher cost ($0.47.m-3 treated). Combined alternatives may benefit the removal effectiveness. Furthermore, more specific identification of contaminants should be investigated separately to choose appropriate treatment for priority chemicals. Another issue is further investigation of costing, including capital, and full environmental impact of treatment.

ABSTRACT As far back as the early 1900?s when it was discovered that water could be a mode of transmitting diseases, chlorine was used to disinfect water. In the 1970?s, the formation of disinfection by-products (DBPs) from the reaction of chlorine with natural organic matter was discovered. Since then there have been various studies on alternative disinfectants that could inactivate microorganisms and at the same time form less or no disinfection by-products. More recently the ultraviolet (UV) irradiation has been used to both disinfect and remove organic contaminants in drinking water. Though the use of UV irradiation has been found to be very effective in the inactivation of microorganisms, it does not provide a residual effect to maintain the water?s microbial quality in the distribution system. Due to this, a secondary disinfectant such as chlorine has to be used to achieve microbial stability, suggesting that the formation of chlorination disinfection by-products would still occur but perhaps in different quantities and with different chemical species. In this research, the use of factorial experiments and single factor experiments were used to determine the effects of pH, alkalinity and UV-fluence (dose) on the formation of three classes of disinfection by-products; haloacetic acids (HAAs), haloacetonitriles (HANs) and trihalomethanes (THMs). These disinfection by-products were measured in water samples following post-UV chlorination and the UV treatment was either UV photolysis or UV/H₂O₂. From the factorial experiment results, treatment of synthetic water with UV/H₂O₂, an advanced oxidation process (AOP), produced fewer post-UV chlorination disinfection by-products (PCDBPs) than UV photolysis. For chlorinated PCDBPs, the percentage difference between UV photolysis and UV/H₂O₂ was 55, 65 and 38% for total HAAs (HAA₉), total HANs (THANs) and total THMs (TTHMs) respectively. The percentage difference between UV photolysis and UV/H₂O₂ for brominated PCDBPs was 41 and 42% for HAA9 and TTHMs respectively. Both the use of pH and alkalinity proved to be factors that were significant in affecting the yields of the PCDBPs studied. Increases in alkalinity were found to increase the formation of PCDBPs in the treatment of synthetic water with UV/H₂O₂. Alkalinity had the opposite effect for PCDBP formed under UV photolysis conditions. Increases in pH always decreased the formation of PCDBPs. In the single factor experiments, haloacetic acid concentrations were unaffected as alkalinity was increased but dichloroacetonitrile and chloroform increased in concentration under treatment conditions of UV photolysis followed by chlorination. The UV/H₂O₂ treatment resulted in a decrease in concentration of the PCDBPs. In the pH studies, water samples were subjected only to the UV/H₂O₂ treatments and a reduction in concentration of PCDBPs occurred between pH 7 and 9.