Introdução: Os efeitos da radiação ultravioleta sobre o sistema imunológico humano são altamente complexos e alteram alguns componentes da resposta imunológica. Objetivo: O objetivo deste estudo foi avaliar os efeitos clínicos, histopatológicos e imunológicos da radiação solar em pescadores do sexo masculino com mais de dez anos de atividade ininterrupta. Métodos: Um estudo prospectivo, transversal, observacional e analítico, foi realizado para determinar as lesões dermatológicas diagnosticadas pelo exame físico, comparando grupos, para a análise de marcadores imunológicos na pele e no sangue, assim como alterações histológicas na pele. Este estudo foi realizado numa comunidade de pescadores, no Pina, no estado de Pernambuco, Brasil. Dezenove pescadores, com tempo médio de profissão de 29,0 ± 10,3 anos, foram incluídos no estudo. As variáveis desta amostra foram: idade, sexo, tipo da pele (segundo classificação de Fitzpatrick) estado civil, grau de instrução, número de filhos, tipo e tempo de atividade profissional, índice de massa corpórea, exposição diária à radiação solar e qualquer tipo de doença atual ou prévia (nos 12 meses anteriores à coleta de dados). As variáveis dermatológicas foram quaisquer alterações em pele, mucosa e anexos. Para comparar a subpopulação de linfócitos no sangue, foram empregados 10 indivíduos não pescadores, vivendo na mesma região e exercendo profissão ao abrigo do sol. As idades médias igualaram-se a 42,5 ± 16,1 anos. Os marcadores imunológicos da pele foram determinados por imuno-histoquímica e os do sangue, por citômetro de fluxo. O teste de Mann-Whitney, para a hipótese de igualdade, entre os grupos expostos e não expostos ao sol, foi usado. O teste de Fisher foi empregado para análise de independência dos grupos e o teste de Wilcoxon, para comparação dos achados imunológicos e histopatológicos em pele exposta e coberta, todos em igual nível de significância (0,05). Resultados: Comparando pele exposta à coberta, elastose (73,7% contra 23,1%, respectivamente; p=0,03), vasos ectásicos dérmicos (78,9% contra 31,6%, respectivamente; p=0,012) e número de células nos segmentos da epiderme entre os cones (5,8 ± 1,08 contra 5,2 ± 0,42; p=0,029) foram significantemente mais freqüentes na pele exposta. Também os marcadores CD45RO+, CD68+ e mastócitos (p=0,040, p<0,001 e p=0,001) foram estatisticamente significantes na pele exposta. O aumento de CD3CD8CD45RO+ no sangue periférico foi mais freqüente em pescadores do que em não pescadores (p=0,016). Conclusões: O efeito barreira à penetração da radiação solar, representado por elastose, aumento do número de células nas camadas entre os cones, aumento de melanócitos e da vasculatura dérmica, representada pela ectasia, sugere a existência de um efeito de tolerância ao dano da radiação solar, o qual provavelmente inibe a instalação da imunodepressão. Esse efeito é reforçado pelo aumento do CD3CD8CD45RO+ e pelo aumento da expressão da linhagem CD28+, capaz de proteger as células CD4+ da apoptose induzida pelo CD95 (Faz). SUMMARY Introduction: The ultraviolet radiation effects on the human immunological system are highly complex, disturbing some components of immune response. Objective: The objective of this study was to evaluate the clinical, histopathological and immunological effects from solar radiation in male fishermen with more than 10 years of uninterrupted activity. Methods: A prospective, transversal, observational and analytical study was done observing the dermatological lesions diagnosed by a physical exam, comparing groups, for the analysis of immunologic markers on the skin and in the blood, as well as histological alterations on the skin. This study was developed at a fishing community in Pina, in the state of Pernambuco, Brazil. Nineteen fishermen with an average professional working time of 29,0 ± 10,3 years were included in this study. The variable of this sample was: age, sex, skin type (according to Fitzpatrick classification), civilian status, degree of instruction, number of children, type and time of professional activity, body mass index, daily sun radiation exposure and any kind of current or past (12 months prior of the collection of data) illness. The dermatological variable was any alterations on the skin, mucosa and annexes. In order to compare the lymphocytes subpopulation in the blood, we used 10 non fishermen living in the same region with an indoor profession. The average ages ranged 42,5 ± 11,6 years. The immunological markers of the skin were determined by immune-histochemistry and those of blood, by flow cytometer. The Mann-Whitney test had been used, for equality hypothesis, between the sun-exposed and non-exposed group. The Fisher test was used for independence group analyzing and Wilcoxon test, as a comparison between the immunological and histopathological findings on exposed and non-exposed skin, all in equal level of significance (0,05). Results: Comparing exposed and non-exposed skin, elastosis (73,7% against 23,1% respectively; p = 0,03) dermis ectasic vases (78,9% against 31,6% respectively; p=0,012) and number of cells in epidermis segments between cones(5,8 ± 1,08 against 5,2 ± 0,42; p=0,029) were significantly more frequent in the exposed skin. Also, the CD45RO+, Cd68+ markers and mastocytes (p=0,040, p<0,001 and p=0,001) had been significantly statistic on exposed skin. The increase of CD3CD8CD45RO+, in peripheral blood, was more frequent in fishermen than the non fishermen workers (p=0,016) Conclusions: The barrier effect to the penetration of the solar radiation established by elastosis, the increase of cellular number of cell layers between the cones, increase of melanocytes and increase of dermal vasculature, represented for the ectasy, suggests the existence of a tolerance effect to sun radiation damage, which probably inhibits the installation of immunodepression. This effect is endorsed by the increasing of CD3CD8CD45RO+ and increase in trend of CD28+ expression, capable to protect Cd4+ cells apoptosis induced from CD95 (Fas). / Introduction: The ultraviolet radiation effects on the human immunological system are highly complex, disturbing some components of immune response. Objective: The objective of this study was to evaluate the clinical, histopathological and immunological effects from solar radiation in male fishermen with more than 10 years of uninterrupted activity. Methods: A prospective, transversal, observational and analytical study was done observing the dermatological lesions diagnosed by a physical exam, comparing groups, for the analysis of immunologic markers on the skin and in the blood, as well as histological alterations on the skin. This study was developed at a fishing community in Pina, in the state of Pernambuco, Brazil. Nineteen fishermen with an average professional working time of 29,0 ± 10,3 years were included in this study. The variable of this sample was: age, sex, skin type (according to Fitzpatrick classification), civilian status, degree of instruction, number of children, type and time of professional activity, body mass index, daily sun radiation exposure and any kind of current or past (12 months prior of the collection of data) illness. The dermatological variable was any alterations on the skin, mucosa and annexes. In order to compare the lymphocytes subpopulation in the blood, we used 10 non fishermen living in the same region with an indoor profession. The average ages ranged 42,5 ± 11,6 years. The immunological markers of the skin were determined by immune-histochemistry and those of blood, by flow cytometer. The Mann-Whitney test had been used, for equality hypothesis, between the sun-exposed and non-exposed group. The Fisher test was used for independence group analyzing and Wilcoxon test, as a comparison between the immunological and histopathological findings on exposed and non-exposed skin, all in equal level of significance (0,05). Results: Comparing exposed and non-exposed skin, elastosis (73,7% against 23,1% respectively; p = 0,03) dermis ectasic vases (78,9% against 31,6% respectively; p=0,012) and number of cells in epidermis segments between cones(5,8 ± 1,08 against 5,2 ± 0,42; p=0,029) were significantly more frequent in the exposed skin. Also, the CD45RO+, Cd68+ markers and mastocytes (p=0,040, p<0,001 and p=0,001) had been significantly statistic on exposed skin. The increase of CD3CD8CD45RO+, in peripheral blood, was more frequent in fishermen than the non fishermen workers (p=0,016) Conclusions: The barrier effect to the penetration of the solar radiation established by elastosis, the increase of cellular number of cell layers between the cones, increase of melanocytes and increase of dermal vasculature, represented for the ectasy, suggests the existence of a tolerance effect to sun radiation damage, which probably inhibits the installation of immunodepression. This effect is endorsed by the increasing of CD3CD8CD45RO+ and increase in trend of CD28+ expression, capable to protect Cd4+ cells apoptosis induced from CD95 (Fas).

Introdução: Os efeitos da radiação ultravioleta sobre o sistema imunológico humano são altamente complexos e alteram alguns componentes da resposta imunológica. Objetivo: O objetivo deste estudo foi avaliar os efeitos clínicos, histopatológicos e imunológicos da radiação solar em pescadores do sexo masculino com mais de dez anos de atividade ininterrupta. Métodos: Um estudo prospectivo, transversal, observacional e analítico, foi realizado para determinar as lesões dermatológicas diagnosticadas pelo exame físico, comparando grupos, para a análise de marcadores imunológicos na pele e no sangue, assim como alterações histológicas na pele. Este estudo foi realizado numa comunidade de pescadores, no Pina, no estado de Pernambuco, Brasil. Dezenove pescadores, com tempo médio de profissão de 29,0 ± 10,3 anos, foram incluídos no estudo. As variáveis desta amostra foram: idade, sexo, tipo da pele (segundo classificação de Fitzpatrick) estado civil, grau de instrução, número de filhos, tipo e tempo de atividade profissional, índice de massa corpórea, exposição diária à radiação solar e qualquer tipo de doença atual ou prévia (nos 12 meses anteriores à coleta de dados). As variáveis dermatológicas foram quaisquer alterações em pele, mucosa e anexos. Para comparar a subpopulação de linfócitos no sangue, foram empregados 10 indivíduos não pescadores, vivendo na mesma região e exercendo profissão ao abrigo do sol. As idades médias igualaram-se a 42,5 ± 16,1 anos. Os marcadores imunológicos da pele foram determinados por imuno-histoquímica e os do sangue, por citômetro de fluxo. O teste de Mann-Whitney, para a hipótese de igualdade, entre os grupos expostos e não expostos ao sol, foi usado. O teste de Fisher foi empregado para análise de independência dos grupos e o teste de Wilcoxon, para comparação dos achados imunológicos e histopatológicos em pele exposta e coberta, todos em igual nível de significância (0,05). Resultados: Comparando pele exposta à coberta, elastose (73,7% contra 23,1%, respectivamente; p=0,03), vasos ectásicos dérmicos (78,9% contra 31,6%, respectivamente; p=0,012) e número de células nos segmentos da epiderme entre os cones (5,8 ± 1,08 contra 5,2 ± 0,42; p=0,029) foram significantemente mais freqüentes na pele exposta. Também os marcadores CD45RO+, CD68+ e mastócitos (p=0,040, p<0,001 e p=0,001) foram estatisticamente significantes na pele exposta. O aumento de CD3CD8CD45RO+ no sangue periférico foi mais freqüente em pescadores do que em não pescadores (p=0,016). Conclusões: O efeito barreira à penetração da radiação solar, representado por elastose, aumento do número de células nas camadas entre os cones, aumento de melanócitos e da vasculatura dérmica, representada pela ectasia, sugere a existência de um efeito de tolerância ao dano da radiação solar, o qual provavelmente inibe a instalação da imunodepressão. Esse efeito é reforçado pelo aumento do CD3CD8CD45RO+ e pelo aumento da expressão da linhagem CD28+, capaz de proteger as células CD4+ da apoptose induzida pelo CD95 (Faz). SUMMARY Introduction: The ultraviolet radiation effects on the human immunological system are highly complex, disturbing some components of immune response. Objective: The objective of this study was to evaluate the clinical, histopathological and immunological effects from solar radiation in male fishermen with more than 10 years of uninterrupted activity. Methods: A prospective, transversal, observational and analytical study was done observing the dermatological lesions diagnosed by a physical exam, comparing groups, for the analysis of immunologic markers on the skin and in the blood, as well as histological alterations on the skin. This study was developed at a fishing community in Pina, in the state of Pernambuco, Brazil. Nineteen fishermen with an average professional working time of 29,0 ± 10,3 years were included in this study. The variable of this sample was: age, sex, skin type (according to Fitzpatrick classification), civilian status, degree of instruction, number of children, type and time of professional activity, body mass index, daily sun radiation exposure and any kind of current or past (12 months prior of the collection of data) illness. The dermatological variable was any alterations on the skin, mucosa and annexes. In order to compare the lymphocytes subpopulation in the blood, we used 10 non fishermen living in the same region with an indoor profession. The average ages ranged 42,5 ± 11,6 years. The immunological markers of the skin were determined by immune-histochemistry and those of blood, by flow cytometer. The Mann-Whitney test had been used, for equality hypothesis, between the sun-exposed and non-exposed group. The Fisher test was used for independence group analyzing and Wilcoxon test, as a comparison between the immunological and histopathological findings on exposed and non-exposed skin, all in equal level of significance (0,05). Results: Comparing exposed and non-exposed skin, elastosis (73,7% against 23,1% respectively; p = 0,03) dermis ectasic vases (78,9% against 31,6% respectively; p=0,012) and number of cells in epidermis segments between cones(5,8 ± 1,08 against 5,2 ± 0,42; p=0,029) were significantly more frequent in the exposed skin. Also, the CD45RO+, Cd68+ markers and mastocytes (p=0,040, p<0,001 and p=0,001) had been significantly statistic on exposed skin. The increase of CD3CD8CD45RO+, in peripheral blood, was more frequent in fishermen than the non fishermen workers (p=0,016) Conclusions: The barrier effect to the penetration of the solar radiation established by elastosis, the increase of cellular number of cell layers between the cones, increase of melanocytes and increase of dermal vasculature, represented for the ectasy, suggests the existence of a tolerance effect to sun radiation damage, which probably inhibits the installation of immunodepression. This effect is endorsed by the increasing of CD3CD8CD45RO+ and increase in trend of CD28+ expression, capable to protect Cd4+ cells apoptosis induced from CD95 (Fas). / Introduction: The ultraviolet radiation effects on the human immunological system are highly complex, disturbing some components of immune response. Objective: The objective of this study was to evaluate the clinical, histopathological and immunological effects from solar radiation in male fishermen with more than 10 years of uninterrupted activity. Methods: A prospective, transversal, observational and analytical study was done observing the dermatological lesions diagnosed by a physical exam, comparing groups, for the analysis of immunologic markers on the skin and in the blood, as well as histological alterations on the skin. This study was developed at a fishing community in Pina, in the state of Pernambuco, Brazil. Nineteen fishermen with an average professional working time of 29,0 ± 10,3 years were included in this study. The variable of this sample was: age, sex, skin type (according to Fitzpatrick classification), civilian status, degree of instruction, number of children, type and time of professional activity, body mass index, daily sun radiation exposure and any kind of current or past (12 months prior of the collection of data) illness. The dermatological variable was any alterations on the skin, mucosa and annexes. In order to compare the lymphocytes subpopulation in the blood, we used 10 non fishermen living in the same region with an indoor profession. The average ages ranged 42,5 ± 11,6 years. The immunological markers of the skin were determined by immune-histochemistry and those of blood, by flow cytometer. The Mann-Whitney test had been used, for equality hypothesis, between the sun-exposed and non-exposed group. The Fisher test was used for independence group analyzing and Wilcoxon test, as a comparison between the immunological and histopathological findings on exposed and non-exposed skin, all in equal level of significance (0,05). Results: Comparing exposed and non-exposed skin, elastosis (73,7% against 23,1% respectively; p = 0,03) dermis ectasic vases (78,9% against 31,6% respectively; p=0,012) and number of cells in epidermis segments between cones(5,8 ± 1,08 against 5,2 ± 0,42; p=0,029) were significantly more frequent in the exposed skin. Also, the CD45RO+, Cd68+ markers and mastocytes (p=0,040, p<0,001 and p=0,001) had been significantly statistic on exposed skin. The increase of CD3CD8CD45RO+, in peripheral blood, was more frequent in fishermen than the non fishermen workers (p=0,016) Conclusions: The barrier effect to the penetration of the solar radiation established by elastosis, the increase of cellular number of cell layers between the cones, increase of melanocytes and increase of dermal vasculature, represented for the ectasy, suggests the existence of a tolerance effect to sun radiation damage, which probably inhibits the installation of immunodepression. This effect is endorsed by the increasing of CD3CD8CD45RO+ and increase in trend of CD28+ expression, capable to protect Cd4+ cells apoptosis induced from CD95 (Fas).

Irradiation with ultraviolet (UV) light is used for the disinfection of bacterial contaminants in the production of potable water, and in the treatment of selected wastewaters. However, efficacy of UV disinfection is limited by the combined effect of suspended solids concentration and UV absorbance. Limited published UV disinfection data are available that account for the combined effects of UV dose, suspended solids concentration and UV absorbance. This present lack of a rigorous quantitative understanding of the kinetics of UV disinfection limits process optimisation and wider application of UV treatment. The development and validation of an adequate model to describe UV disinfection kinetics presented in this thesis can therefore be justified by an increased confidence of reliability of design for UV disinfection. Using the published data of Nguyen (1999), four established model forms were assessed to account for the combined effect of suspended solids and/or soluble UV absorbing compounds, and UV dose on the efficacy of disinfection. The four model forms were: a log-linear form, Davey Linear-Arrhenius (DL-A), Square-Root (or Ratkowsky- Belehradek) and a general nth order Polynomial (nOP) form that was limited to a third order. Criteria for assessment of an adequate predictive model were established including: accuracy of predicted against observed values, percent variance accounted for (%V), and; appraisal of residuals. The DL-A model was shown to best fit the data for UV disinfection of Escherichia coli (ATCC 25922); followed by the nOP, log-linear and Square-Root forms. However, the DL-A form must be used in conjunction with a first-order chemical reaction equation, and was shown to predict poorly at high experimental values of UV dose (> 40,000 μWs cm-2). The DL-A model was not amenable to extrapolation beyond the observed UV dose range. To overcome the shortcomings of the Davey Linear-Arrhenius model synthesis of two new, non-linear model forms was undertaken. The two models were a modified exponentially damped polynomial (EDPm) and a form based on the Weibull probability distribution. The EDPm model has three terms: a rate coefficient (k), a damping coefficient (λ), and; a breakpoint dose ([dose]B). The rate coefficient governs the initial rate of disinfection prior to the onset of tailing, whilst the breakpoint is the UV dose that indicates the onset of tailing. The damping coefficient controls curvature in the survivor curve. The Weibull model has just two terms: a dimensionless scale parameter (β0), and; a shape parameter (β1). The scale parameter represents the level of disinfection in the tail of the survivor curve (as log10 N/N0), whilst the shape parameter governs the degree of curvature of the survivor data. Each model was assessed against the independent and published UV disinfection data of Nelson (2000) for treatment of faecal coliforms in a range of waste stabilisation pond effluents. Both models were found to be well suited to account for tailing in these UV disinfection data. Overall, the EDPm model gave a better fit to the data than the Weibull model form. To rigorously validate the suitability of the new EDPm and Weibull models a series of experimental trials were designed and carried out in a small-scale pilot UV disinfection unit. These trials included data determined specifically at low values of UV dose (<10,000 μWs cm-2) to fill the gap in the experimental data of Nguyen (1999). The experimental trials were carried out using a commercially available, UV disinfection unit (LC5TM from Ultraviolet Technology of Australasia Pty Ltd). Purified water contaminated with Escherichia coli (ATCC 25922) with a range of feed water flow rates (1 to 4 L min-1) was used. E. coli was selected because it is found in sewage, or water contaminated with faecal material, and is used as an indicator for the presence of enteric pathogens. E. coli should not be present in potable water. The hydrodynamics of water flow within the disinfection unit were established using digital video photography of dye trace studies with Methylene Blue. Nominal UV dose (2,700 to 44,200 μWs cm-2) was controlled by manipulating the flow rate of feed water through the UV disinfection unit (i.e. residence time), or by varying the exposed length of the control volume of the disinfection unit. The transmittance of the feed water (at 254 nm) was adjusted by the addition of either a soluble UV absorbing agent (International RoastTM instant coffee powder; 0.001 to 0.07 g L-1), or by addition of suspended matter as diatomaceous earth (Celite 503TM; 0.1 to 0.7 g L-1, with a median particle size of 23 μm). The absorbing agent (instant coffee), when in a comparable concentration, was found to produce a greater reduction in water transmission than the suspended material (Celite 503TM). It therefore contributed to a greater reduction in the initial rate of disinfection. Neither agent was found to produce a systematic reduction in the observed efficacy of disinfection however. Experimental results highlight that in the absence of soluble absorbing agents, or suspended solids, the initial rate of disinfection is higher when fewer viable bacteria are initially present. Both the new EDPm and Weibull forms gave a good fit to the experimental data. The EDPm better fitted the data on the basis of residual sum-of-squares (0.03 to 2.13 for EDPm cf. 0.16 to 4.37 for the Weibull form). These models are both of a form suitable for practical use in modelling UV disinfection data. Results of this research highlight the impact of water quality, as influenced by the combined effect of UV dose, suspended solids concentration and UV absorbance, on small-scale UV disinfection for potable water production. Importantly, results show that the concentration of soluble UV absorbing agents and suspended solids are not in themselves sufficient criteria on which to base assessment of efficacy of UV disinfection / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1342403 / Thesis (M.Eng.Sc.) - University of Adelaide, School of Chemical Engineering, 2008

Irradiation with ultraviolet (UV) light is used for the disinfection of bacterial contaminants in the production of potable water, and in the treatment of selected wastewaters. However, efficacy of UV disinfection is limited by the combined effect of suspended solids concentration and UV absorbance. Limited published UV disinfection data are available that account for the combined effects of UV dose, suspended solids concentration and UV absorbance. This present lack of a rigorous quantitative understanding of the kinetics of UV disinfection limits process optimisation and wider application of UV treatment. The development and validation of an adequate model to describe UV disinfection kinetics presented in this thesis can therefore be justified by an increased confidence of reliability of design for UV disinfection. Using the published data of Nguyen (1999), four established model forms were assessed to account for the combined effect of suspended solids and/or soluble UV absorbing compounds, and UV dose on the efficacy of disinfection. The four model forms were: a log-linear form, Davey Linear-Arrhenius (DL-A), Square-Root (or Ratkowsky- Belehradek) and a general nth order Polynomial (nOP) form that was limited to a third order. Criteria for assessment of an adequate predictive model were established including: accuracy of predicted against observed values, percent variance accounted for (%V), and; appraisal of residuals. The DL-A model was shown to best fit the data for UV disinfection of Escherichia coli (ATCC 25922); followed by the nOP, log-linear and Square-Root forms. However, the DL-A form must be used in conjunction with a first-order chemical reaction equation, and was shown to predict poorly at high experimental values of UV dose (> 40,000 μWs cm-2). The DL-A model was not amenable to extrapolation beyond the observed UV dose range. To overcome the shortcomings of the Davey Linear-Arrhenius model synthesis of two new, non-linear model forms was undertaken. The two models were a modified exponentially damped polynomial (EDPm) and a form based on the Weibull probability distribution. The EDPm model has three terms: a rate coefficient (k), a damping coefficient (λ), and; a breakpoint dose ([dose]B). The rate coefficient governs the initial rate of disinfection prior to the onset of tailing, whilst the breakpoint is the UV dose that indicates the onset of tailing. The damping coefficient controls curvature in the survivor curve. The Weibull model has just two terms: a dimensionless scale parameter (β0), and; a shape parameter (β1). The scale parameter represents the level of disinfection in the tail of the survivor curve (as log10 N/N0), whilst the shape parameter governs the degree of curvature of the survivor data. Each model was assessed against the independent and published UV disinfection data of Nelson (2000) for treatment of faecal coliforms in a range of waste stabilisation pond effluents. Both models were found to be well suited to account for tailing in these UV disinfection data. Overall, the EDPm model gave a better fit to the data than the Weibull model form. To rigorously validate the suitability of the new EDPm and Weibull models a series of experimental trials were designed and carried out in a small-scale pilot UV disinfection unit. These trials included data determined specifically at low values of UV dose (<10,000 μWs cm-2) to fill the gap in the experimental data of Nguyen (1999). The experimental trials were carried out using a commercially available, UV disinfection unit (LC5TM from Ultraviolet Technology of Australasia Pty Ltd). Purified water contaminated with Escherichia coli (ATCC 25922) with a range of feed water flow rates (1 to 4 L min-1) was used. E. coli was selected because it is found in sewage, or water contaminated with faecal material, and is used as an indicator for the presence of enteric pathogens. E. coli should not be present in potable water. The hydrodynamics of water flow within the disinfection unit were established using digital video photography of dye trace studies with Methylene Blue. Nominal UV dose (2,700 to 44,200 μWs cm-2) was controlled by manipulating the flow rate of feed water through the UV disinfection unit (i.e. residence time), or by varying the exposed length of the control volume of the disinfection unit. The transmittance of the feed water (at 254 nm) was adjusted by the addition of either a soluble UV absorbing agent (International RoastTM instant coffee powder; 0.001 to 0.07 g L-1), or by addition of suspended matter as diatomaceous earth (Celite 503TM; 0.1 to 0.7 g L-1, with a median particle size of 23 μm). The absorbing agent (instant coffee), when in a comparable concentration, was found to produce a greater reduction in water transmission than the suspended material (Celite 503TM). It therefore contributed to a greater reduction in the initial rate of disinfection. Neither agent was found to produce a systematic reduction in the observed efficacy of disinfection however. Experimental results highlight that in the absence of soluble absorbing agents, or suspended solids, the initial rate of disinfection is higher when fewer viable bacteria are initially present. Both the new EDPm and Weibull forms gave a good fit to the experimental data. The EDPm better fitted the data on the basis of residual sum-of-squares (0.03 to 2.13 for EDPm cf. 0.16 to 4.37 for the Weibull form). These models are both of a form suitable for practical use in modelling UV disinfection data. Results of this research highlight the impact of water quality, as influenced by the combined effect of UV dose, suspended solids concentration and UV absorbance, on small-scale UV disinfection for potable water production. Importantly, results show that the concentration of soluble UV absorbing agents and suspended solids are not in themselves sufficient criteria on which to base assessment of efficacy of UV disinfection / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1342403 / Thesis (M.Eng.Sc.) - University of Adelaide, School of Chemical Engineering, 2008

Irradiation with ultraviolet (UV) light is used for the disinfection of bacterial contaminants in the production of potable water, and in the treatment of selected wastewaters. However, efficacy of UV disinfection is limited by the combined effect of suspended solids concentration and UV absorbance. Limited published UV disinfection data are available that account for the combined effects of UV dose, suspended solids concentration and UV absorbance. This present lack of a rigorous quantitative understanding of the kinetics of UV disinfection limits process optimisation and wider application of UV treatment. The development and validation of an adequate model to describe UV disinfection kinetics presented in this thesis can therefore be justified by an increased confidence of reliability of design for UV disinfection. Using the published data of Nguyen (1999), four established model forms were assessed to account for the combined effect of suspended solids and/or soluble UV absorbing compounds, and UV dose on the efficacy of disinfection. The four model forms were: a log-linear form, Davey Linear-Arrhenius (DL-A), Square-Root (or Ratkowsky- Belehradek) and a general nth order Polynomial (nOP) form that was limited to a third order. Criteria for assessment of an adequate predictive model were established including: accuracy of predicted against observed values, percent variance accounted for (%V), and; appraisal of residuals. The DL-A model was shown to best fit the data for UV disinfection of Escherichia coli (ATCC 25922); followed by the nOP, log-linear and Square-Root forms. However, the DL-A form must be used in conjunction with a first-order chemical reaction equation, and was shown to predict poorly at high experimental values of UV dose (> 40,000 μWs cm-2). The DL-A model was not amenable to extrapolation beyond the observed UV dose range. To overcome the shortcomings of the Davey Linear-Arrhenius model synthesis of two new, non-linear model forms was undertaken. The two models were a modified exponentially damped polynomial (EDPm) and a form based on the Weibull probability distribution. The EDPm model has three terms: a rate coefficient (k), a damping coefficient (λ), and; a breakpoint dose ([dose]B). The rate coefficient governs the initial rate of disinfection prior to the onset of tailing, whilst the breakpoint is the UV dose that indicates the onset of tailing. The damping coefficient controls curvature in the survivor curve. The Weibull model has just two terms: a dimensionless scale parameter (β0), and; a shape parameter (β1). The scale parameter represents the level of disinfection in the tail of the survivor curve (as log10 N/N0), whilst the shape parameter governs the degree of curvature of the survivor data. Each model was assessed against the independent and published UV disinfection data of Nelson (2000) for treatment of faecal coliforms in a range of waste stabilisation pond effluents. Both models were found to be well suited to account for tailing in these UV disinfection data. Overall, the EDPm model gave a better fit to the data than the Weibull model form. To rigorously validate the suitability of the new EDPm and Weibull models a series of experimental trials were designed and carried out in a small-scale pilot UV disinfection unit. These trials included data determined specifically at low values of UV dose (<10,000 μWs cm-2) to fill the gap in the experimental data of Nguyen (1999). The experimental trials were carried out using a commercially available, UV disinfection unit (LC5TM from Ultraviolet Technology of Australasia Pty Ltd). Purified water contaminated with Escherichia coli (ATCC 25922) with a range of feed water flow rates (1 to 4 L min-1) was used. E. coli was selected because it is found in sewage, or water contaminated with faecal material, and is used as an indicator for the presence of enteric pathogens. E. coli should not be present in potable water. The hydrodynamics of water flow within the disinfection unit were established using digital video photography of dye trace studies with Methylene Blue. Nominal UV dose (2,700 to 44,200 μWs cm-2) was controlled by manipulating the flow rate of feed water through the UV disinfection unit (i.e. residence time), or by varying the exposed length of the control volume of the disinfection unit. The transmittance of the feed water (at 254 nm) was adjusted by the addition of either a soluble UV absorbing agent (International RoastTM instant coffee powder; 0.001 to 0.07 g L-1), or by addition of suspended matter as diatomaceous earth (Celite 503TM; 0.1 to 0.7 g L-1, with a median particle size of 23 μm). The absorbing agent (instant coffee), when in a comparable concentration, was found to produce a greater reduction in water transmission than the suspended material (Celite 503TM). It therefore contributed to a greater reduction in the initial rate of disinfection. Neither agent was found to produce a systematic reduction in the observed efficacy of disinfection however. Experimental results highlight that in the absence of soluble absorbing agents, or suspended solids, the initial rate of disinfection is higher when fewer viable bacteria are initially present. Both the new EDPm and Weibull forms gave a good fit to the experimental data. The EDPm better fitted the data on the basis of residual sum-of-squares (0.03 to 2.13 for EDPm cf. 0.16 to 4.37 for the Weibull form). These models are both of a form suitable for practical use in modelling UV disinfection data. Results of this research highlight the impact of water quality, as influenced by the combined effect of UV dose, suspended solids concentration and UV absorbance, on small-scale UV disinfection for potable water production. Importantly, results show that the concentration of soluble UV absorbing agents and suspended solids are not in themselves sufficient criteria on which to base assessment of efficacy of UV disinfection / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1342403 / Thesis (M.Eng.Sc.) - University of Adelaide, School of Chemical Engineering, 2008