title: Towards identification of floc compounds in water using multi-frequency fluorescence lifetime analysis

authors: Dissanayake, S.A.D. Asanka Nilakshi

subjects: Fluorescence lifetime

abstract: UV disinfection is commonly used in water treatment to inactivate pathogens such as Cryptosporidium and viruses to prevent diseases such as cryptosporidiosis and norovirus in communities. Disinfection typically follows water treatment steps, such as coagulation, flocculation, clarification, and filtration. However, particles in water, for example, flocs 0.1 to 100 μm in diameter, made from humic and inorganic substances present in the water, surrounding a Cryptosporidium oocyst or virus, can protect the pathogens from UV exposure. Although water treatment steps prior to disinfection remove 99% of the particulates, particles can still be present in the 1000s to 10,000’s per litre after filtration. While the chances of a floc particle carrying a virus or oocyst are typically low, in some regions, particularly during calving in the dairy industry, oocyst concentrations in the water might be high due to cryptosporidiosis in calves. Therefore, it is useful to test the properties of the floc compound for UV penetration to determine whether the disinfection method is appropriate.

In this thesis, a technique that uses multi-frequency analysis to measure the fluorescence lifetime of a fluorophore to provide information on particle composition
is presented. Frequency-domain fluorescence fluorometry was used to determine the fluorescence lifetime. This was achieved using an experimental setup that used a laser diode operating at 100 mW and modulated at 10–60 MHz to excite the fluorophores, optical elements to focus and filter the light, and detectors to collect the fluorescence emission signal via a storage oscilloscope. The signals were then processed using a MATLAB program to determine the fluorescence lifetime. 

Fluorescence lifetime measurements were challenged by the chemical and physical behaviour of the fluorophore and the adsorption of the fluorophore to the floc particles. Therefore, standard measurements such as turbidity, pH, particle size, and fluorescence were used to understand the absorption/adsorption of fluorescein to flocs. Fluorescence was observed at the 260–490 nm excitation wavelengths, with fluorescence emissions at approximately 510 nm. The particle size and turbidity measurements showed that fluorescein acted as a flocculant, with the particle size increasing with increasing fluorescein concentration. Fluorescence intensity measurements from a standard fluorescence spectrophotometer were used to calculate fluorescein adsorption on humic acid and kaolin to generate adsorption isotherms. Fluorescein was bonded to kaolin 10 times more than to humic acid. Adequate flocculation required a pH of 6.5 to produce reasonably flocculated particles in the sample. Surface charge analysis showed that the use of buffer to control pH required more alum to neutralise the surface charge of humic acid and kaolin.

Multi frequency measurements and subsequent analysis showed that the fluorescence lifetime and contamination ratio were 4.2 ± 0.3 ns and 0.09 ± 0.05 for fluorescein. The fluorescence lifetime of fluorescein was compatible with the results of previous studies using different techniques. The samples with floc particles had a larger excitation light contamination ratio than those without particles; therefore, the contamination ratio could be used as a measure of particle contamination in the samples. The fluorescence lifetime of fluorescein did not change when fluorescein was attached to humic acid particles, but increased by 0.6 ns for kaolin floc particles.

text: Towards identification of floc compounds in water using multi-frequency fluorescence lifetime analysis UV disinfection is commonly used in water treatment to inactivate pathogens such as Cryptosporidium and viruses to prevent diseases such as cryptosporidiosis and norovirus in communities. Disinfection typically follows water treatment steps, such as coagulation, flocculation, clarification, and filtration. However, particles in water, for example, flocs 0.1 to 100 μm in diameter, made from humic and inorganic substances present in the water, surrounding a Cryptosporidium oocyst or virus, can protect the pathogens from UV exposure. Although water treatment steps prior to disinfection remove 99% of the particulates, particles can still be present in the 1000s to 10,000’s per litre after filtration. While the chances of a floc particle carrying a virus or oocyst are typically low, in some regions, particularly during calving in the dairy industry, oocyst concentrations in the water might be high due to cryptosporidiosis in calves. Therefore, it is useful to test the properties of the floc compound for UV penetration to determine whether the disinfection method is appropriate.

In this thesis, a technique that uses multi-frequency analysis to measure the fluorescence lifetime of a fluorophore to provide information on particle composition
is presented. Frequency-domain fluorescence fluorometry was used to determine the fluorescence lifetime. This was achieved using an experimental setup that used a laser diode operating at 100 mW and modulated at 10–60 MHz to excite the fluorophores, optical elements to focus and filter the light, and detectors to collect the fluorescence emission signal via a storage oscilloscope. The signals were then processed using a MATLAB program to determine the fluorescence lifetime. 

Fluorescence lifetime measurements were challenged by the chemical and physical behaviour of the fluorophore and the adsorption of the fluorophore to the floc particles. Therefore, standard measurements such as turbidity, pH, particle size, and fluorescence were used to understand the absorption/adsorption of fluorescein to flocs. Fluorescence was observed at the 260–490 nm excitation wavelengths, with fluorescence emissions at approximately 510 nm. The particle size and turbidity measurements showed that fluorescein acted as a flocculant, with the particle size increasing with increasing fluorescein concentration. Fluorescence intensity measurements from a standard fluorescence spectrophotometer were used to calculate fluorescein adsorption on humic acid and kaolin to generate adsorption isotherms. Fluorescein was bonded to kaolin 10 times more than to humic acid. Adequate flocculation required a pH of 6.5 to produce reasonably flocculated particles in the sample. Surface charge analysis showed that the use of buffer to control pH required more alum to neutralise the surface charge of humic acid and kaolin.

Multi frequency measurements and subsequent analysis showed that the fluorescence lifetime and contamination ratio were 4.2 ± 0.3 ns and 0.09 ± 0.05 for fluorescein. The fluorescence lifetime of fluorescein was compatible with the results of previous studies using different techniques. The samples with floc particles had a larger excitation light contamination ratio than those without particles; therefore, the contamination ratio could be used as a measure of particle contamination in the samples. The fluorescence lifetime of fluorescein did not change when fluorescein was attached to humic acid particles, but increased by 0.6 ns for kaolin floc particles.

year: 2025

title: An Investigation of the Integration of Science, Mathematics and Technology within a Technological Design Context

authors: Mathew Thomas, Tiju

abstract: This research focused on studying the integration of science, mathematics and technology in a technological design context. The daily classroom practices of a teacher and 19 of his students (aged 15-16) in a technology class were analysed with a focus on the knowledge and skills used while designing individualised projects (street luge gravity-powered vehicle) with a view to identifying the integration of cross-disciplinary knowledge. This research is aligned with the elements of both interpretive and critical theory paradigms. The focus of the interpretive paradigm rests on how students construct meaning from their personal experiences and their world view. Critical theory is used to create a platform for integration by understanding the current practices and phenomena in a technology classroom to develop strategies that could be implemented in other classrooms to create an integrative learning environment.

text: An Investigation of the Integration of Science, Mathematics and Technology within a Technological Design Context This research focused on studying the integration of science, mathematics and technology in a technological design context. The daily classroom practices of a teacher and 19 of his students (aged 15-16) in a technology class were analysed with a focus on the knowledge and skills used while designing individualised projects (street luge gravity-powered vehicle) with a view to identifying the integration of cross-disciplinary knowledge. This research is aligned with the elements of both interpretive and critical theory paradigms. The focus of the interpretive paradigm rests on how students construct meaning from their personal experiences and their world view. Critical theory is used to create a platform for integration by understanding the current practices and phenomena in a technology classroom to develop strategies that could be implemented in other classrooms to create an integrative learning environment.

year: 2017

title: Te pā harakeke: Educational success and kōhanga reo

authors: McMillan, Hoana

subjects: kōhanga reo

abstract: Exploring the meaning of educational success in an indigenous context is a challenging task.  Success has come to be promoted as narrow forms of academic success.  However, “academic success” does not adequately take into account the knowledge, values, and beliefs of Indigenous peoples that stem from their unique ways of living and being in the world.  Indigenous language immersion settings, such as kōhanga reo (Māori immersion “language nests” for children from birth to six years old in Aotearoa New Zealand), have emerged in response to the desires of Indigenous peoples to retain their knowledge, language, and culture. 

This study contributes to the debate about the nature of educational success by examining multi-generational whānau (family) views of educational success in kōhanga reo. It also explores the contributions of kōhanga reo to the educational success of whānau. The study explored the lived experiences and views of educational success across five whānau spanning three generations: kaumātua (the grandparent generation who helped to set up kōhanga reo), mātua (the parent generation and first graduates of kōhanga reo), and mokopuna (children of the mātua and grandchildren of the kaumātua generations). Data for the kaumātua and mātua generations was collected through the Māori cultural practice of wānanga, and the Mosaic approach was used with mokopuna to provide a number of tools for them to express their views of educational success. The data gathered was then represented as multi-generational pūrākau (a Māori form of storying) to ensure the narratives relating to educational success remained intact and culturally valid.

The findings of this research show the meaning of educational success for the three generations in kōhanga reo was associated with Mana Reo (the power of language), Mana Tangata (the power of people), and Mana Whenua (the power of the land). In addition, kōhanga reo has championed the educational success of the multi-generational whānau by providing strong support for the Māori language, whānau transformations, and wellbeing. The influence of kōhanga reo has led to many outcomes showcasing the educational success of mokopuna and whānau who are learning, using, sharing, and protecting te reo Māori. All three generations value whanaungatanga and manaakitanga, and actively look for opportunities that lead to positive outcomes in their homes, schools, and wider communities.

There are many implications for whānau, kōhanga reo, Te Kōhanga Reo National Trust, the education sector, and policy makers. Foremost is reaffirming the message that identity, language, and culture matters in discussions relating to educational success. With each generation, whānau are unlocking new dimensions of, and pathways to, educational success linked to Mana Reo, Mana Tangata, and Mana Whenua. The kōhanga reo model, as a unique indigenous model, plays an important role in unlocking pathways to educational success now and in the future through its unwavering commitment to the cultural socialisation of whānau.

text: Te pā harakeke: Educational success and kōhanga reo Exploring the meaning of educational success in an indigenous context is a challenging task.  Success has come to be promoted as narrow forms of academic success.  However, “academic success” does not adequately take into account the knowledge, values, and beliefs of Indigenous peoples that stem from their unique ways of living and being in the world.  Indigenous language immersion settings, such as kōhanga reo (Māori immersion “language nests” for children from birth to six years old in Aotearoa New Zealand), have emerged in response to the desires of Indigenous peoples to retain their knowledge, language, and culture. 

This study contributes to the debate about the nature of educational success by examining multi-generational whānau (family) views of educational success in kōhanga reo. It also explores the contributions of kōhanga reo to the educational success of whānau. The study explored the lived experiences and views of educational success across five whānau spanning three generations: kaumātua (the grandparent generation who helped to set up kōhanga reo), mātua (the parent generation and first graduates of kōhanga reo), and mokopuna (children of the mātua and grandchildren of the kaumātua generations). Data for the kaumātua and mātua generations was collected through the Māori cultural practice of wānanga, and the Mosaic approach was used with mokopuna to provide a number of tools for them to express their views of educational success. The data gathered was then represented as multi-generational pūrākau (a Māori form of storying) to ensure the narratives relating to educational success remained intact and culturally valid.

The findings of this research show the meaning of educational success for the three generations in kōhanga reo was associated with Mana Reo (the power of language), Mana Tangata (the power of people), and Mana Whenua (the power of the land). In addition, kōhanga reo has championed the educational success of the multi-generational whānau by providing strong support for the Māori language, whānau transformations, and wellbeing. The influence of kōhanga reo has led to many outcomes showcasing the educational success of mokopuna and whānau who are learning, using, sharing, and protecting te reo Māori. All three generations value whanaungatanga and manaakitanga, and actively look for opportunities that lead to positive outcomes in their homes, schools, and wider communities.

There are many implications for whānau, kōhanga reo, Te Kōhanga Reo National Trust, the education sector, and policy makers. Foremost is reaffirming the message that identity, language, and culture matters in discussions relating to educational success. With each generation, whānau are unlocking new dimensions of, and pathways to, educational success linked to Mana Reo, Mana Tangata, and Mana Whenua. The kōhanga reo model, as a unique indigenous model, plays an important role in unlocking pathways to educational success now and in the future through its unwavering commitment to the cultural socialisation of whānau.

year: 2024