title: Target separation of arsenic from contaminated raw water

authors: Aremu, James Oyediji

subjects: arsenic

abstract: Arsenic is known to be one of the most toxic and carcinogenic elements known to have affected millions of people worldwide. Arsenic in surface and groundwater originates from both natural and anthropogenic sources. Prolonged exposure to arsenic can lead to skin disease, cancer, diabetes and cardiovascular disease. This thesis investigates target separation of arsenic from contaminated water using the adsorption and coagulation/flocculation/dissolved air flotation (C/F/DAF) processes. 
DMI-65, a silica based catalytic media was used as an adsorbent to investigate As (III) and As (V) removal from a contaminated drinking water. Batch adsorption studies were conducted at different pH (5, 6, 7 and 8.5) to determine adsorption kinetics. Equilibrium was achieved after 6 hours of contact time and experimental data were best fitted to the pseudo second-order kinetic model for As (III) and As (V). The adsorption data were best fitted to Langmuir isotherm models and the maximum adsorption capacity of DMI-65 for As (III) and As (V) were estimated to be 0.318 mg/g and 0.237 mg/g respectively. Thermodynamics studies revealed that adsorption capacity and arsenic removal percentage using DMI-65 increased with increase in temperature. The adsorption process can be attributed to physisorption as a result of Van der Waals interaction at the surface of the adsorbent. Regeneration and reusability of a media is an important economic factor. DMI-65 was able to demonstrate its ability to regenerate after several cycles using sodium hydroxide (NaOH) and performed well over a wide pH range. The maximum removal efficiency for As (III) was 96.55 % at pH 5 and 90.40 % for As (V) at pH 8.5. 
A continuous adsorption study was conducted in a fixed-bed column to remove arsenic from the Waikato River using DMI-65. The dynamic adsorption capacity and breakthrough time was well predicted by Thomas and Yoon-Nelson models. The maximum adsorption capacity was found to be 11.96 mg/g using DMI-65 as adsorbent for initial concentration, flowrate and pH of ~ 13.00 – 20.00 µg/L, 20 mL/min and 5, respectively. Results obtained showed that DMI-65 is effective in removing arsenic from contaminated drinking water. It is also effective in reducing turbidity but fouling of the adsorption column is a major drawback and leads to increased pressure drop in the fixed-bed column. 
Competing ions in the form of organic anions such as nitrate (NO₃⁻), silicate (SiO₄⁴⁻), sulfate (SO₄²⁻), bicarbonate (CO₃²⁻) and phosphate (H₂PO₄⁻) are known to interfere with arsenic removal in natural waters. This interference is also influenced by the pH of the solution and anionic concentration. The study was conducted at pH levels (5 – 9) and anionic concentration strength (1, 5 and 10 mM). The most significant interference with the removal of As (V) by polyaluminium chloride (PAC) occurred in the presence of phosphate at pH 6 with a removal rate of 5.52 % at 10 mM phosphate concentration. Overall, the major impact of the competing anions on As (V) removal followed the following order of H₂PO₄⁻ > CO₃²⁻ > NO₃⁻ > SO₄²⁻.
Target separation of arsenic from other contaminants was investigated in a two-stage C/F/DAF process. The results of this study indicated that increase in flotation time (10 – 30 minutes) and saturation pressure (2 – 4 bar) did not result in any significant increase in arsenic removal efficiency. Turbidity removal efficiency was poor at pH 5 and 6 despite recording higher arsenic removal efficiency. The first stage DAF process showed that 88.10 % of arsenic and 3.44 % turbidity removal efficiency was achieved using 9.4 mg/L of PAC at pH 6. Increasing the pH of the remaining solution to 8 in the second-stage DAF process resulted in 83.55 % arsenic removal and 64.08 % turbidity removal after adding 0.47 mg/L PAC. These findings showed that the amount of arsenic leaving the water treatment plant (WTP) to the wastewater treatment plant (WWTP) can be reduced from the current 0.942 kg/day to 0.16 kg/day. This represents an overall reduction of 83.01 % in the amount of arsenic that would have end up in the biosolids thereby making it unfit for agricultural purposes. This result showed that arsenic can successfully be separated from other contaminants in a two-stage C/F/DAF process by change in pH from 6 to 8 and under optimised operating conditions.

text: Target separation of arsenic from contaminated raw water Arsenic is known to be one of the most toxic and carcinogenic elements known to have affected millions of people worldwide. Arsenic in surface and groundwater originates from both natural and anthropogenic sources. Prolonged exposure to arsenic can lead to skin disease, cancer, diabetes and cardiovascular disease. This thesis investigates target separation of arsenic from contaminated water using the adsorption and coagulation/flocculation/dissolved air flotation (C/F/DAF) processes. 
DMI-65, a silica based catalytic media was used as an adsorbent to investigate As (III) and As (V) removal from a contaminated drinking water. Batch adsorption studies were conducted at different pH (5, 6, 7 and 8.5) to determine adsorption kinetics. Equilibrium was achieved after 6 hours of contact time and experimental data were best fitted to the pseudo second-order kinetic model for As (III) and As (V). The adsorption data were best fitted to Langmuir isotherm models and the maximum adsorption capacity of DMI-65 for As (III) and As (V) were estimated to be 0.318 mg/g and 0.237 mg/g respectively. Thermodynamics studies revealed that adsorption capacity and arsenic removal percentage using DMI-65 increased with increase in temperature. The adsorption process can be attributed to physisorption as a result of Van der Waals interaction at the surface of the adsorbent. Regeneration and reusability of a media is an important economic factor. DMI-65 was able to demonstrate its ability to regenerate after several cycles using sodium hydroxide (NaOH) and performed well over a wide pH range. The maximum removal efficiency for As (III) was 96.55 % at pH 5 and 90.40 % for As (V) at pH 8.5. 
A continuous adsorption study was conducted in a fixed-bed column to remove arsenic from the Waikato River using DMI-65. The dynamic adsorption capacity and breakthrough time was well predicted by Thomas and Yoon-Nelson models. The maximum adsorption capacity was found to be 11.96 mg/g using DMI-65 as adsorbent for initial concentration, flowrate and pH of ~ 13.00 – 20.00 µg/L, 20 mL/min and 5, respectively. Results obtained showed that DMI-65 is effective in removing arsenic from contaminated drinking water. It is also effective in reducing turbidity but fouling of the adsorption column is a major drawback and leads to increased pressure drop in the fixed-bed column. 
Competing ions in the form of organic anions such as nitrate (NO₃⁻), silicate (SiO₄⁴⁻), sulfate (SO₄²⁻), bicarbonate (CO₃²⁻) and phosphate (H₂PO₄⁻) are known to interfere with arsenic removal in natural waters. This interference is also influenced by the pH of the solution and anionic concentration. The study was conducted at pH levels (5 – 9) and anionic concentration strength (1, 5 and 10 mM). The most significant interference with the removal of As (V) by polyaluminium chloride (PAC) occurred in the presence of phosphate at pH 6 with a removal rate of 5.52 % at 10 mM phosphate concentration. Overall, the major impact of the competing anions on As (V) removal followed the following order of H₂PO₄⁻ > CO₃²⁻ > NO₃⁻ > SO₄²⁻.
Target separation of arsenic from other contaminants was investigated in a two-stage C/F/DAF process. The results of this study indicated that increase in flotation time (10 – 30 minutes) and saturation pressure (2 – 4 bar) did not result in any significant increase in arsenic removal efficiency. Turbidity removal efficiency was poor at pH 5 and 6 despite recording higher arsenic removal efficiency. The first stage DAF process showed that 88.10 % of arsenic and 3.44 % turbidity removal efficiency was achieved using 9.4 mg/L of PAC at pH 6. Increasing the pH of the remaining solution to 8 in the second-stage DAF process resulted in 83.55 % arsenic removal and 64.08 % turbidity removal after adding 0.47 mg/L PAC. These findings showed that the amount of arsenic leaving the water treatment plant (WTP) to the wastewater treatment plant (WWTP) can be reduced from the current 0.942 kg/day to 0.16 kg/day. This represents an overall reduction of 83.01 % in the amount of arsenic that would have end up in the biosolids thereby making it unfit for agricultural purposes. This result showed that arsenic can successfully be separated from other contaminants in a two-stage C/F/DAF process by change in pH from 6 to 8 and under optimised operating conditions.

year: 2020

title: 15 yr of interstellar neutral hydrogen observed with the Interstellar Boundary Explorer

authors: Galli, A

abstract: The interactions of our heliosphere with the surrounding local interstellar medium (LISM) lead to a range of observable phenomena such as energetic neutral atoms (ENAs) from the boundary regions of the heliosphere and the influx of interstellar neutrals (ISNs) into the inner solar system. Hydrogen is the dominant neutral species in the LISM, but due to ionization and radiation pressure, only a fraction of the ISN H atoms reach the inner solar system close to Earth. Monitoring this signal therefore provides observational constraints on our assumptions of the LISM and the solar-activity-dependent loss processes inside the heliosphere. The IBEX-Lo instrument on board the Interstellar Boundary Explorer has been the only instrument so far to measure ISN H atoms directly, together with ISN D, He, Ne, O, and ENAs in the energy range from tens of eV to 2 keV. This study covers 15 yr of IBEX-Lo ISN H observations, i.e., more than one solar cycle and includes two solar minima when the ISN H signal in IBEX-Lo is strongest. Despite the very intense ISN He signal, the ISN H signal can be retrieved with appropriate knowledge of the instrument, choice of optimum observation season, and supporting modeling. The retrieved ISN H signal shows a clear anticorrelation with solar activity. The resulting ISN H maps are available in orbit format and in ecliptic coordinates and will be the basis for future more detailed comparison with heliosphere models.

text: 15 yr of interstellar neutral hydrogen observed with the Interstellar Boundary Explorer The interactions of our heliosphere with the surrounding local interstellar medium (LISM) lead to a range of observable phenomena such as energetic neutral atoms (ENAs) from the boundary regions of the heliosphere and the influx of interstellar neutrals (ISNs) into the inner solar system. Hydrogen is the dominant neutral species in the LISM, but due to ionization and radiation pressure, only a fraction of the ISN H atoms reach the inner solar system close to Earth. Monitoring this signal therefore provides observational constraints on our assumptions of the LISM and the solar-activity-dependent loss processes inside the heliosphere. The IBEX-Lo instrument on board the Interstellar Boundary Explorer has been the only instrument so far to measure ISN H atoms directly, together with ISN D, He, Ne, O, and ENAs in the energy range from tens of eV to 2 keV. This study covers 15 yr of IBEX-Lo ISN H observations, i.e., more than one solar cycle and includes two solar minima when the ISN H signal in IBEX-Lo is strongest. Despite the very intense ISN He signal, the ISN H signal can be retrieved with appropriate knowledge of the instrument, choice of optimum observation season, and supporting modeling. The retrieved ISN H signal shows a clear anticorrelation with solar activity. The resulting ISN H maps are available in orbit format and in ecliptic coordinates and will be the basis for future more detailed comparison with heliosphere models.

year: 2025-04-14

title: The embodied and lived experiences of welfare and care for highly impaired, high performance para-sport athletes in Aotearoa New Zealand

authors: Lowry, Amanda

abstract: Aligning with calls in critical disability studies to bring the body and impairment into disability sport, this thesis examines the welfare and care experiences of highly impaired athletes in high-performance sport. While a focus on athlete welfare has gained some international prominence, and a duty of care is increasingly invoked as an organisational and coaching responsibility, these developments remain largely disconnected from disability.  
The research is centred around two main objectives. First, to amplify the lived and embodied experiences of highly impaired, high performance disabled athletes as they prepare for, train, and compete in sport, and those who support them. Second, to understand how sporting institutions and regulations (within the broader context of government funding and national health care provision) influence welfare and care practices for high performance disabled athletes. 
Crip methodologies and Indigenous Māori storytelling methodologies such as pūrākau centres lived experience as a site of resistance and knowledge production. Using a reflexive, qualitative approach, including semi-structured interviews, autoethnographic vignettes, and visual ethnography, I expose how impairment effects are managed in ableist sporting environments that valorise normative athlete ideals. I interviewed 11 high-performance paraathletes, seven organisational representatives and two support workers. 
The research highlights the material, emotional, and temporal labour of care in highperformance sport. Findings are organised around three core themes: the embodied labour of care, impairment effects and interdependence; the tension between crip time, care time, and performance time; the intersecting structural, institutional, and ableist barriers that shape and constrain highly impaired athletes’ participation in disability sport.  
The first theme shows how high-performance sport privileges autonomous, efficient, and normative bodies, while marginalising those whose messy, gritty embodied impairment effects demand more time, support, and interdependence. The findings bring to the fore biosocial, psycho-emotional costs of navigating care and its impact on athlete welfare. The second theme uncovers how the rhythms of highly impaired bodies disrupt the linear, clockbound time of high-performance sport, revealing the incompatibility between care time and high performance cultures. It highlights the vital yet invisible labour of support workers, ii unacknowledged in contemporary sporting discourse. The third theme addresses the barriers that highly impaired athletes face when navigating ableist institutional and organisational structures. It exposes the complexity of the ableist disability sporting landscape and the gap between duty of care rhetoric and practice. 
Ultimately, this thesis calls for a radical reimagining of disability sport, one that centres interdependence, affirms bodily difference, and addresses the structural failures that marginalise highly impaired athletes.

text: The embodied and lived experiences of welfare and care for highly impaired, high performance para-sport athletes in Aotearoa New Zealand Aligning with calls in critical disability studies to bring the body and impairment into disability sport, this thesis examines the welfare and care experiences of highly impaired athletes in high-performance sport. While a focus on athlete welfare has gained some international prominence, and a duty of care is increasingly invoked as an organisational and coaching responsibility, these developments remain largely disconnected from disability.  
The research is centred around two main objectives. First, to amplify the lived and embodied experiences of highly impaired, high performance disabled athletes as they prepare for, train, and compete in sport, and those who support them. Second, to understand how sporting institutions and regulations (within the broader context of government funding and national health care provision) influence welfare and care practices for high performance disabled athletes. 
Crip methodologies and Indigenous Māori storytelling methodologies such as pūrākau centres lived experience as a site of resistance and knowledge production. Using a reflexive, qualitative approach, including semi-structured interviews, autoethnographic vignettes, and visual ethnography, I expose how impairment effects are managed in ableist sporting environments that valorise normative athlete ideals. I interviewed 11 high-performance paraathletes, seven organisational representatives and two support workers. 
The research highlights the material, emotional, and temporal labour of care in highperformance sport. Findings are organised around three core themes: the embodied labour of care, impairment effects and interdependence; the tension between crip time, care time, and performance time; the intersecting structural, institutional, and ableist barriers that shape and constrain highly impaired athletes’ participation in disability sport.  
The first theme shows how high-performance sport privileges autonomous, efficient, and normative bodies, while marginalising those whose messy, gritty embodied impairment effects demand more time, support, and interdependence. The findings bring to the fore biosocial, psycho-emotional costs of navigating care and its impact on athlete welfare. The second theme uncovers how the rhythms of highly impaired bodies disrupt the linear, clockbound time of high-performance sport, revealing the incompatibility between care time and high performance cultures. It highlights the vital yet invisible labour of support workers, ii unacknowledged in contemporary sporting discourse. The third theme addresses the barriers that highly impaired athletes face when navigating ableist institutional and organisational structures. It exposes the complexity of the ableist disability sporting landscape and the gap between duty of care rhetoric and practice. 
Ultimately, this thesis calls for a radical reimagining of disability sport, one that centres interdependence, affirms bodily difference, and addresses the structural failures that marginalise highly impaired athletes.

year: 2025-10