Academic literature on the topic 'Dissolved Air Flotation DAF'

This research evaluated dissolved air flotation (DAF) as a separation method for algae and phosphorus from municipal wastewater at the City of Logan, Utah Wastewater Reclamation Facility. DAF uses the supersaturation of air to raise suspended algae and other particles to the surface, where they can be easily removed. DAF, in conjunction with chemical coagulants and flocculants, can approach 95% algae and phosphorus removal. The algae removed using the DAF process will be used in the production of biofuels and bioplastics. A pilot DAF unit was used to determine the optimum alum dose for total phosphorus (TP) and algae removal. In addition, a bench-scale jar test unit was used to study the effects of various alum and polymer doses on removal efficiencies at different times of the day. An optimal alum dose was found to be 30 mg/L based on results from both the pilot and bench-scale units. No advantage to adding polymer was found. Algae removal efficiencies on the pilot DAF ranged from 68-70%, and the effluent algae concentration was reduced to 10 mg/L. Approximately 65% of the total phosphorus was removed, from 1.1 to 0.4 mg/L, which is low enough to meet regulations anticipated to be promulgated by the state of Utah. Using the assumption that the molar weight of algae is 3,550 g/mole, the molar ratio of Al/TSS was found to be 30.1 and the molar ratio of Al/TP was found to be 7.5. Extracellular polymeric substances (EPS) excreted by algal cells act as a natural flocculant and may allow for chemical usage to be minimized. Autoflocculation and bioflocculation, natural processes caused by EPS production and an increased pH level, were not observed to be a significant factor. The chemical dosing rates provide the City of Logan with basic operational parameters for a full-scale (15 million gallons per day) DAF plant, providing an effluent phosphorus level below 0.5 mg/L. The alum will cost $1,118 per day, with a daily electrical cost of approximately $149. This full-scale DAF plant would harvest 1,563 kg of algal biomass per day, with a cost per kilogram of algae at $0.81.

<p>The purpose of this diploma work was to investigate the problem of insufficient fibre recovery in the dissolved air flotation-cell at the new thermomechanical pulping-line at Braviken Paper Mill. An investigation of the effect of process parameters on the removal efficiency in the micro-flotation process was undertaken.</p><p>The experiments were carried out for two setups at the Noss pilot plant with a small-scale flotation unit. Factorial design helped plan the experiments and four factors were controlled; temperature, fibre-size distribution, water quality and feed concentration. Three samples, feed, overflow and filtrate, were taken from each experiment and concentration measurements were made. The results were analyzed using the software MODDE.</p><p>The results from showed an influence from the fibre-size distribution. To see if the fibre-size distribution really had an effect on the results, follow-up experiments were carried out. These experiments showed no influence from temperature, fibre-size distribution or water quality. This concludes that none of those three factors influenced the results significantly.</p><p>Additional experiments were done to examine the influence from concentration and fibre-size distribution on the flotation efficiency and these showed an influence from the feed concentration. When increasing the feed concentration the efficiency of the flotation process decreased.</p>

The dissolved air flotation (DAF) has been used in drinking water treatment for its excellent algae and natural organic matter (NOM) removal. DAF drinking water treatability test are often conducted in a DAF jar test apparatus. Although, DAF jar test studies showed that they were able to predict NOM removals at full-scale facilities well, they have not always been successful in predicting the turbidity removals. One possible reason of the DAF jar test inaccuracy results could be associated to the small jar diameter, which may create wall effects. Therefore, the first two objectives of this research are: a) to develop and test a new, larger diameter and larger volume batch bench-scale dissolved air flotation system (LB-DAF) to better simulate turbidity removals in drinking water applications; b) to confirm these results by comparing the LB-DAF and full-scale DAF turbidity removals for two other source waters. The raw water characteristics of the three plants were quite different and the testing was performed at different times of the year. The development/optimization of the LB-DAF evaluated the impact of different variables (i.e., mixing intensity, water depth/tank diameter ratio, impeller shape, saturator pressure and recycle ratio). The results showed that the LB-DAF predicted well the full-scale DAF turbidity removals at three water treatment plants, and these predictions were better than those of DAF jar tests. For the LB-DAF design and operational variables evaluated had a limited impact on the turbidity removals. The LB-DAF predicted well DAF full-scale turbidity removals regardless of water temperature. This is an indication of the robustness of the DAF system. Ballasted sedimentation (BS) is a compact coagulation/flocculation and sedimentation process combination that has become very popular because it is very compact and because it can handle large variations in raw water turbidity and NOM. The literature survey did not initially identify studies on the BS treatment of algal impacted waters, for which DAF is considered particularly suitable. Thus, the third main objective of this dissertation was to compare the efficiency of BS with that conventional gravity settling (CGS), and that of DAF for the treatment of an algal impacted water via jar tests. These comparisons were performed at the Belleville Water Treatment Plant using Bay of Quinte water, one of the most eutrophic zones of Lake Ontario. Unfortunately, a change of weather prior to the testing resulted in raw water samples with relatively low concentrations of algae and cyanobacteria. The testing showed that DAF and BS had very similar NOM, cyanobacteria/algae (chlorophyll a and phycocyanin) removals.; however, the BS required microsand addition, polymer addition and a slightly higher alum dose. Only for turbidity removal the DAF was somewhat superior. It is suggested that these comparison experiments be repeated with waters that are more impacted by algae and cyanobacteria.

Environmental Engineering<br>M.S.Env.E.<br>Pulp and paper mills are one of the top consumers of water related to industrial manufacturing, which ultimately leads to a large volume of heavily contaminated wastewater. This discharged effluent can have a harmful effect on the receiving aquatic environment and cause further ramifications downstream. Thus, a technically feasible and cost effective treatment solution for safe release from the mill is essential. Dissolved air flotation (DAF) has many applications and involves the formation of air microbubbles triggered by a drop to atmospheric pressure. When introduced into the wastewater, these microbubbles attach to the floc particles present and float to the surface. Another water treatment technology is ozone, a powerful oxidant, and has been widely used in water and wastewater treatment over recent decades, including color reduction in pulp and paper mill wastewater treatment. This thesis studied the effect pre-ozonation has on the DAF process in treating pulp and paper mill secondary effluent. Wastewaters from three mills with different initial water quality parameters were used, especially chemical oxygen demand (COD), turbidity, and color. The most suitable coagulant and coagulant aid, aluminum chlorohydrate and cationic polymer NS 4700P respectively, were selected, and an effective bench-scale experimental procedure was established. Pre-ozonation did not reduce the need for coagulant due to little change in the overall COD, color, or turbidity removal. However, ozonation did reduce color before coagulation, and the ultimate target removal of COD to 90 ppm was met with the conditions chosen.<br>Temple University--Theses

A flotação por ar dissolvido (FAD) é um método de separação de fases bastante utilizado em sistemas de tratamento de efluentes industriais. Nos últimos 20 anos, numerosos avanços têm contribuído para uma maior eficiência deste processo. Entre estes, podem-se citar os avanços nos métodos para a saturação de ar na água. Atualmente tem-se realizado estudos com a utilização de bombas multifásicas em substituição às unidades de saturação tradicionais, com vistas a se buscar maior simplicidade e facilidade operacional, aliados à menor necessidade de manutenção periódica da unidade de saturação. Desta forma, o presente trabalho teve como objetivo avaliar o desempenho de uma bomba multifásica na geração de microbolhas de ar no processo de flotação por ar dissolvido para o tratamento de efluente de indústria têxtil. O projeto foi dividido nas seguintes etapas: Etapa I - com o emprego do Flotateste, foram determinadas as dosagens adequadas de coagulante e polímero para o tratamento do despejo líquido industrial em estudo; Etapa II - utilizando-se uma unidade piloto de flotação por ar dissolvido montada nas instalações de uma indústria têxtil, avaliou-se a influência das condições de operação (taxa de aplicação superficial, razão de recirculação, pressão de saturação e quantidade de ar fornecida) na eficiência do sistema constituído pela bomba multifásica. Considerando a taxa de aplicação superficial empregada neste estudo, a qual foi mantida em faixa estreita de valor (TASclar em torno de 128,6 ± 10 m/d), verificou-se que os maiores valores de eficiência de remoção dos parâmetros monitorados foram obtidos nos ensaios realizados com razão de recirculação igual a 30% associados ao fornecimento de ar de 13%. Nos ensaios onde se realizou a avaliação da concentração de ar presente na recirculação pressurizada, as concentrações de ar efetivamente fornecidas (fração dissolvida e não dissolvida) pelo sistema constituído pela bomba multifásica, foram superiores às concentrações máximas teóricas de ar dissolvido calculadas a partir da Lei de Henry. O valor da relação A/S que forneceu os melhores resultados situou-se em torno de 0,015 g ar/g sólidos. Desta forma, sugere-se tal valor como subsídio ao projeto de sistema de flotação constituído pela tecnologia em estudo nesta pesquisa.<br>The dissolved air flotation is a method for solid/liquid separation that is used in the industries to treat the wastewater. In the last 20 years, several advances have been added to increase the process\' efficiency. For example, there are the advances in the air saturation methods. Nowadays, studies have been carried out with the use of multiphase pumps instead of conventional saturator units. This way, the aim of this research was to evaluate the performance of a multiphase pump in the air microbubble generation for dissolved air flotation process that is applied to treat the effluent of textile industry. The research was performed in two stages: i) on laboratory scale (Flotatest), where the adequate dosages of coagulant and flocculation aid were carried out; ii) in a pilot unit, where studies were conducted aiming at the evaluation of operational conditions in the system\'s efficiency. In the pilot unit (hydraulic surface loading equal to 128,6 ± 10m/d) , it was verified that the best results in terms of removal efficiency of monitored parameters were obtained for the essays performed with recirculation ratio equal to 30%, air supply of 13% and A/S ratio equal to 0.015 g air/g solids. The air concentrations supplied (dissolved fraction and non-dissolved fraction) by the system were higher than the maximum theoretical concentration of dissolved air (Henry\'s law).

A presente pesquisa teve por objetivo a investigação da influência do tamanho de partículas floculadas na eficiência da clarificação de águas para abastecimento por flotação por ar dissolvido (FAD) com o emprego de método e equipamento para a aquisição e análise de imagens especialmente desenvolvidos, tendo em vista à caracterização da distribuição de tamanho de flocos e microbolhas de ar, bem como, o estudo dos aglomerados bolhas-floco (em termos de número de microbolhas de ar aderidas e velocidade ascensional) presentes no processo de flotação e comparação dos dados experimentais àqueles obtidos em simulação com o emprego do modelo matemático proposto por Reali (1991). Os ensaios foram realizados com água sintética (turbidez de 7,5±0,2 NTU; cor aparente de 38±1 uC; alcalinidade de 29,8±0,6 mg\'CA\'CO IND.3\'/L; condutividade de 59,3±0,8 \'mü\'S/cm; UV254nm de 0,128±0,004 \'CM POT.-1\'), a qual foi coagulada com a aplicação de 1,9 mg/L de \'AL POT. 3+\' (pH de 6,6±0,05) e divididos em duas Fases: Fase 1 - ensaios preliminares realizados em escala de laboratório, com o emprego do flotateste; Fase 2 - ensaios realizados em unidade piloto de flotação. Os resultados alcançados demonstraram que: i) a distribuição de tamanho de partículas floculadas influenciou diretamente a clarificação por flotação da água em estudo, sendo que as melhores condições de floculação foram aquelas que conduziram à formação, em sua maioria, de partículas floculadas com diâmetro médio de Feret acima de 300 \'mü\'m; ii) os menores valores residuais dos parâmetros analisados na água em estudo foram alcançados com o emprego do tempo de floculação de 17 min, entretanto a FAD foi capaz de operar também com boa eficiência com a utilização de tempo de floculação de 10 min; iii) o método e equipamento desenvolvidos nesta pesquisa para a aquisição e análise de imagens demonstraram constituir importantes ferramentas para a obtenção das distribuições de tamanho de flocos e microbolhas de ar, bem como, para a determinação do número de microbolhas de ar aderidas às superfícies dos flocos e da velocidade ascensional dos aglomerados bolhas-floco gerados no processo de flotação; iv) mesmo com as diversas simplificações adotadas no desenvolvimento do modelo matemático analisado e considerando as condições experimentais utilizadas nesta pesquisa, foi possível verificar para a água em estudo e para as condições operacionais empregadas nesta pesquisa, que a modelação matemática proposta por Reali (1991) foi capaz de fornecer subsídios para uma adequada estimativa do número de microbolhas de ar aderidas aos flocos, bem como, das velocidades ascensionais dos aglomerados bolhas-floco.<br>The goal of this research was to investigate the flocculated particles size distribution influence on the dissolved air flotation (DAF) efficiency. Special image acquisition method and equipment were used to characterize the flocculated particles and air microbubbles size distribution, as well as, the clusters (in terms of microbubbles number adhered and rise velocity) in the contact zone outlet of the DAF unit. Besides that, the experimental results were compared with those obtained from the DAF modeling proposed by Reali (1991). The trials were carried out with synthetic water (temperature of 26.0 ± 0.5oC; turbidity of 7.5±0.2 NTU; apparent color of 38±1 CU; alkalinity of 29.8±0.6 mg\'CA\'\'CO IND.3\'/L; conductivity of 59.3±0.8 \'mü\'S/cm; UV254nm of 0.128±0.004 \'CM POT.-1\'), that it was coagulated by applying 1.9 mg/L of \'AL POT.3+\' (22.5 mg/L alum). The trials were divided into two phases: Phase 1 - preliminary tests carried out in laboratory facilities (flotatest); Phase 2 - tests carried out in pilot facilities (DAF pilot unit). The results showed that: i) the flocculation conditions interfered directly on the efficiency of DAF process, and the best flocculation conditions were those that conducted to formation of flocculated particles size with Feret mean diameter above 300 \'mü\'m; ii) the best results were obtained applying flocculation time of 17 min, however, DAF was also capable of operating with a satisfactory efficiency when applying flocculation time of 10 min; iii) the special image acquisition method and equipment developed in this research proved to be a important tool to characterize the flocculated particles and air microbubbles size distribution, as well as, the number of air microbubbles adhered to the flocs surface and the clusters rise velocity; iv) the DAF modeling developed by Reali (1991) provided a reliable prediction of the microbubbles number adhered to the flocs surface, as well as, the clusters rise velocity.

A flotação por ar dissolvido (FAD) é reconhecida atualmente como técnica eficiente para a etapa de clarificação em sistemas de tratamento de água para abastecimento. Diversos estudos vêm sendo realizados para aprimoramento dessa técnica e das características físicas das unidades FAD. Seguindo essa tendência, o presente trabalho teve como objetivo estudar os efeitos da velocidade na entrada da zona de contato (\'V IND.EZC\') na eficiência de clarificação de unidades retangulares FAD. Para o presente estudo foi utilizada água sintética preparada através da adição de 1,0 mg/L de ácido húmico e 8,5 mg/L de caulinita, a qual foi coagulada com sulfato de alumínio. A pesquisa foi dividida em duas fases: FASE I - com o emprego do Flotateste foram determinadas as dosagens adequadas de coagulante, o pH adequado de coagulação com a medição do potencial zeta das partículas (PZ), o gradiente médio de velocidade para floculação e o tempo médio para floculação para o tratamento da água sintética em estudo; FASE II - utilizando unidade FAD em escala piloto foram realizados ensaios para diferentes variações na altura da entrada da zona de contato (he) da câmara de flotação de forma a se obter diferentes valores de \'V IND.EZC\'. Nesta fase foram investigadas duas diferentes condições de coagulação as quais forneceram bons resultados por flotação: 1ª condição, aplicação de 42,5 mg/L de \'AL IND.2\'(\'SO IND.4\')IND.3\' e pH de 6,35 \'+ OU -\' 0,05 na qual resultou em PZ positivo em torno de +10 mV e para 2ª condição, aplicação de 22,5 mg/L de \'AL IND.2\'(\'SO IND.4\')IND.3\' e pH de 6,40 \'+ OU -\' 0,05 na qual resultou em PZ próximo de 0 mV. Os ensaios foram monitorados e comparados entre si os valores residuais de turbidez e cor aparente. Em todos os ensaios as taxas de aplicação superficial foram mantidas em faixas estreitas de verificando-se que os melhores resultados residuais dos parâmetros monitorados foram obtidos para a 1ª condição de estudo com valores de 0,66 NTU de turbidez e cor aparente igual a 2 uC (eficiências de 90,5 e 93,9% respectivamente). Os resultados demonstraram que para a faixa de valores de \'V IND.EZC\' entre 62,2 e 12.432,4 m/h pouca influência desse parâmetro foi observada na eficiência do processo de clarificação por flotação para ambas as condições de coagulação investigadas. Entretanto, a faixa de valores de \'V IND.EZC\' entre 124,3 e 180,2 m/h forneceram as melhores condições de flotação. Portanto, sugere-se tal faixa de valores como subsídio ao projeto de sistemas de flotação constituído pelas características apresentadas nesta pesquisa.<br>Dissolved air flotation (DAF) is currently recognized as an efficient technique for water clarification in water treatment systems. Several studies have been conducted to improve this technique and the physical characteristics of DAF units in order to constantly improve their performance. Following this trend, the aim of this research was to evaluate the effects of the velocity in the contact zone entrance on the clarification efficiency of rectangular DAF units. A DAF pilot plant fed with synthetic water prepared by adding 1.0 mg/L of humic acid and 8.5 mg/L of kaolin, and coagulated with aluminum sulfate was used. The research was divided into two phases: I) by using a laboratory scale DAF unit (Flotatest) the optimal coagulation, flocculation, and flotation conditions for the synthetic water previously described were investigated; and II) by using a DAF pilot unit tests were performed for different variations in the height of the contact zone entrance (he) of the flotation chamber to obtain different values of velocity in the contact zone entrance. In this phase two different conditions of coagulation were investigated yielding good results: 1st condition: application of 42.5 mg/L of \'AL IND.2\'(\'SO IND.4\')IND.3\' and pH 6.35 \'+ OR -\' 0.05, which resulted in zeta potential of positive particles around +10 mV, and 2nd condition: application of 22.5 mg/L \'AL IND.2\'(\'SO IND.4\')IND.3\' and pH 6.40 \'+ OR -\' 0.05, which resulted in zeta potential of particles near zero. The tests were monitored and the residual values of turbidity and apparent color were compared. In all experiments, the hydraulic surface loadings were kept in narrow bands of values (in the contact zone equal to 180 \'+ OR -\' 4 m/h and in the clarification zone, equal to 184 \'+ OR -\' 4 m/d). It was verified that the best residual results of the parameters monitored were obtained for the 1st condition with 0.66 NTU turbidity and apparent color equal to 2 uC (efficiencies of 90.5 and 93.9%, respectively). The results showed that for the range of values of velocity in the contact zone entrance between 62.2 and 12432.4 m/h little influence of this parameter was observed on the clarification efficiency process by flotation for both coagulation conditions investigated. However, as the range of values between 124.3 and 180.2 m/h provided the best flotation conditions, such a range should be adopted for the designs of rectangular DAF units.

O reator de FAD deve propiciar condições adequadas para contato entre as micro-bolhas e os flocos formados no pré-tratamento e também condições para que o conjunto floco/bolha possa ser direcionado ao topo do reator, e assim ser removido. O projeto de pesquisa visou estudar condições hidrodinâmicas proporcionadas pela variação da Velocidade Cross-Flow (VCF) e assim verificar a influência na eficiência de uma estação piloto de flotação por ar dissolvido. A VCF é importante parâmetro para concepção de unidades de FAD e é função da vazão de entrada no tanque de flotação e da área entre o nível d\'água no tanque de flotação e o anteparo que separa a zona de contato da zona de separação. A velocidade cross-flow constitui um parâmetro de grande importância para projetos de unidades de flotação. Nesta região de transição entre a zona de contato e a zona de separação, ocorre a passagem do conjunto floco/bolha, e turbulência excessiva pode causar o rompimento do conjunto e assim comprometer a eficiência da flotação. Além disso, o padrão de escoamento observado na zona de separação dos flotadores, onde ocorre a separação dos aglomerados \"flocos + bolhas\", depende fortemente do valor médio da velocidade cross-flow, conforme comentado por Lundh et al. (2000 e 2002) e por Reali e Patrizzi (2007). Daí a necessidade de se investigar mais profundamente a influência da VCF na eficiência da clarificação por flotação. O projeto de pesquisa foi dividido em duas etapas. Para realização das etapas foi estudado um tipo de água preparada em laboratório, através da adição de substância húmica e caulinita, para obtenção de cor aparente e turbidez, respectivamente. A água estudada possui cor aparente e turbidez moderada (1 mg/L de substância húmica e 8,5 mg/L de caulinita) resultando em valores de turbidez por volta de 7 NTU e cor aparente por volta de 40 UH. A etapa 1 consistiu na determinação do par, pH de coagulação e dosagem de coagulante (sulfato de alumínio), gradiente médio de floculação e tempo médio de floculação adequado para a água de estudo. Para realização da etapa 1 foi utilizado equipamento de flotação de bancada de regime de batelada (Flotateste), que se encontra nas dependências do Laboratório de Tratamento Avançado e Reuso de Águas - LATAR/SHS/EESC/USP. Foram mantidos fixos os seguintes parâmetros: \'T IND.MR\', \'G IND.MR\', \'T IND.F\', \'G IND.F\', \'P IND.SAT\', \'T IND.REC\', \'V IND.FLOT\'. Conforme preconizado por Reali et al (2007), foi variada a dosagem de coagulante. Após determinado o melhor par pH e dosagem de coagulante foram realizados ensaios visando determinar o melhor \'G IND.F\' e \'T IND.F\' para a água em estudo. Para a água de estudo foram escolhidas duas condições de potencial Zeta, determinados na etapa 1 do projeto de pesquisa. A primeira condição o potencial Zeta permaneceria com valor próximo de 0 mV e na segunda condição o potencial Zeta seria positivo, por volta de +12 mV. A etapa 2 consistiu em variar a velocidade cross-flow, através da variação da altura do vertedor de saída da água flotada de uma unidade piloto de flotação, de forma a se obter diferentes valores de VCF (mantendo-se constantes os valores de tempo de contato e taxa de aplicação superficial na zona de contato), para dois valores de Taxas de Aplicação Superficial (TAS) (7,67 m/h e 15 m/h) na zona de separação e os dois valores de potencial Zeta (PZ), e com isto avaliar a sua influencia na eficiência de remoção de sólidos suspensos totais, cor e turbidez da instalação piloto retangular de FAD.<br>The reactor DAF should provide adequate conditions for contact between the micro-bubbles and the flakes formed in the pretreatment conditions and also for the aggregate flocs/bubble can be directed to the top of the reactor, and thus be removed. The research project aimed at studying hydrodynamic conditions provided by the variation of Cross-Flow Velocity (VCF) and thus checks the influence on the efficiency of a pilot plant of dissolved air flotation. The VCF is an important parameter to design units of DAF and is a function of input flow in the flotation tank and the area between the water level in the flotation tank and the bulkhead that separates the contact zone of the zone of separation. The cross-flow velocity is a parameter of great importance to projects of flotation units. In this region of the transition zone between the contact zone and the separation zone, occurs the passage of the aggregate flocs/bubble, and excessive turbulence can cause disruption of the aggregate and thereby harm the flotation efficiency. Moreover, the pattern of flow observed in the flotation separation zone, which occurs the separation of aggregates \"flakes + bubbles\", depends strongly on the average value of cross-flow velocity as described by Lundh et al. (2000 and 2002) and Reali and Patrizzi (2007). Hence the needs to investigate further the influence of VCF on the clarification efficiency by flotation. The research project was divided into two steps. To perform the steps has been studied a type of water prepared in the laboratory, through the addition of humic substances and kaolin, to obtain apparent color and turbidity, respectively. The study water has moderate turbidity and apparent color (1 mg/L of humic substance and 8.5 mg/L of kaolin) resulting in turbidity values around 7 NTU and color apparent by 40 HU. Step 1 consisted in the determination of the pair, coagulation pH and coagulant dosage (aluminum sulfate), flocculation gradient and time flocculation suitable for the study water. For the implementation of step 1 was used bench batch flotation system equipment (Flotatest), located on the Laboratory for Advanced Treatment and Reuse Water - LATAR / SHS / EESC / USP. Were kept fixed the following parameters: \'T IND.MR\', \'G IND.MR\', \'T IND.F\', \'G IND.F\', \'P IND.SAT\', \'T IND.REC\', \'V IND.FLOT\'. As predicted by Reali et al (2007), was varied the dosage of coagulant. After determined the best pair of coagulant dosage and pH coagulation the tests were performed to determine the best \'G IND.F\' and \'T IND.F\' for the study water. For the study water were chosen two conditions of Zeta potential values, determined in the step 1 of the research project, where the first condition the Zeta potential value kept near 0 mV and the second condition kept a positive value of Zeta potential, around +12 mV. The step 2 consisted of varying the cross-flow velocity, by varying the height of the outlet weir of the clarified water of the flotation pilot plant to obtain different values of VCF (keeping constant the values of time contact and application rate on the contact zone) for two values of superficial application rates (7.67 m/h and 15 m/h) in the zone of separation and the two values of Zeta potential (PZ) and then was availed the influence on removal efficiency of total suspended solids, colour and turbidity of the rectangular pilot plant of DAF.

Abstract Oily wastewaters are heterogeneous, containing various types of oils, surfactants from detergents, metals etc. Oily wastewaters are produced from a wide range of industries such as metalworking, petroleum refineries, the petrochemical industry, transportation as well as the textile and food industries. Oily wastewaters, especially those containing stable oil-in-water emulsions, require advanced treatment as conventional treatment methods have their limitations to meet ever-stricter environmental regulations. Ultrafiltration is a widely accepted and commonly used treatment method for oily wastewaters. The first aim of this thesis was to increase knowledge concerning the performance of an industrial-scaled ultrafiltration-based process treating concentrated real oily wastewaters. The demand for a more effective pre-treatment method for ultrafiltration to enhance performance and decrease fouling of membrane was observed. The second aim of the thesis was to investigate the suitability and efficiency of different methods for treating concentrated model oil-in-water emulsions and real oily wastewaters. The treatment methods studied were electrocoagulation (electrolytic dissolution of anodic metal), conventional coagulation-flocculation followed by either sedimentation or dissolved air flotation, and dissolved air flotation utilising cationic air bubbles. Electrocoagulation was discovered to be a promising treatment method for various types of oil-in-water emulsions. Dissolved air flotation with cationic modified air bubbles was proven to be an efficient method with even higher treatment results with smaller chemical doses when compared to conventional coagulation-flocculation followed by dissolved air flotation. The biodegradation of various components is an important measure of their impact on the environment in case of spillage. The third aim of the thesis was to explore the biodegradability of different types of oils and surfactants in solution conditions and soils. It was discovered that the biodegradation of light fuel oil continued during a three-month time period, reaching a biodegradation degree of over 60% in mineral-rich soil. For surfactants, their distinct effect on the biodegradation of organic material in soil was observed, and it masked the biodegradation of the surfactants themselves<br>Tiivistelmä Öljyiset jätevedet ovat heterogeenisiä, sisältäen mm. erityyppisiä öljyjä, metalleja ja pesuaineiden pinta-aktiivisia aineita. Öljyisiä jätevesiä muodostuu laajalti eri teollisuuksista, kuten metallintyöstöstä, öljyn jalostuksesta, petrokemian teollisuudesta, ruoka- ja tekstiiliteollisuudesta sekä liikenteestä. Öljyiset jätevedet, varsinkin stabiileja öljyemulsioita sisältävät, vaativat tehokkaan käsittelymenetelmän, jotta ympäristölainsäädännön ja luvituksen ehdot täyttyvät. Ultrasuodatus on yleisesti käytössä oleva öljyisten jätevesien käsittelymenetelmä. Tämän väitöstyön ensimmäinen tavoite oli lisätä tietoutta teollisen mittakaavan konsentroituneiden öljyisten jätevesien ultrasuodatusprosessien tehokkuudesta. Prosessien strategisista kohdista kerättyjen öljyisten jätevesien karakterisointitulosten perusteella havaittiin, että ennen ultrasuodatusta tarvitaan tehokas esikäsittelyvaihe prosessin tehostamiseksi ja ultrasuodattimen tukkeutumisen vähentämiseksi. Täten toinen väitöstyön tavoite oli selvittää eri menetelmien soveltuvuutta ja tehokkuutta konsentroituneiden malliaineina käytettyjen öljyemulsioiden ja öljyisten jätevesien käsittelyssä. Tutkitut käsittelymenetelmät olivat elektrokoagulaatio (sähkökemiallinen flokkaavien metalli-ionien liuottaminen anodilta), koagulaatio-flokkulaatio ja laskeutus/korkeapaineflotaatio sekä korkeapaineflotaatiomenetelmä, joka hyödyntää kationisia ilmakuplia. Elektrokoagulaation todettiin olevan erittäin tehokas käsittelymenetelmä, jolla saavutettiin korkeat puhdistustulokset erityyppisille öljyemulsioille. Korkeapaineflotaatiolla, joka hyödyntää kationisia ilmakuplia, saavutettiin hyvät puhdistustulokset jopa pienemmillä kemikaalimäärillä verrattuna perinteiseen koagulaatio-flokkulaatioon ja korkepaineflotaation. Erilaisten komponenttien biohajoavuus on tärkeä suure arvioitaessa niiden ympäristövaikutuksia. Väitöstyön kolmas tavoite oli selvittää erilaisten öljyjen ja pinta-aktiivisten aineiden biohajoavuutta erilaisissa liuosolosuhteissa ja maa-aineksissa. Tärkeimmät biohajoavuustutkimustulokset olivat, että kevyt polttoöljy saavutti kolmen kuukauden mittauksen aikana yli 60 % biohajoavuusasteen mineraalirikkaassa maa-aineksessa. Pinta-aktiivisten aineiden havaittiin lisäävän huomattavasti maan orgaanisen aineksen biohajoamista, ja tämä vaikeutti itse pinta-aktiivisten aineiden biohajoamisen arviointia