title: Biogeochemistry of denitrifying bioreactors to enhance phosphorus removal from agricultural subsurface drainage

authors: Perera, Maddhumage Gimhani Nuwanthika

abstract: Degradation of water quality due to nutrient over-enrichment has become a global environmental concern. In Aotearoa, agricultural pollution of freshwaters by nutrients is increasing. Therefore, strategies need to be implemented to minimize nutrient pollution in surface waters. Denitrifying bioreactors (DBRs) are a prominent edge-of-field treatment technology to mitigate surface water nitrate loadings from agricultural subsurface drainage. Recent studies have identified that subsurface drainage can also contribute to the loss of phosphorus from agricultural soil. Therefore, this thesis investigates the potential of DBRs to incorporate iron-based materials to sequester phosphorus and reduce pollution of waterways.
There is some evidence suggesting low-level phosphorus removal by woodchip bioreactors alone. However, it is inevitable that woodchips alone do not abiotically remove phosphorus due to the incompatibility between the surface charge of wood at neutral-to-acidic pH values. In this study, raw pinus radiata, and, thermally modified pyrolyzed woodchips were employed for surface modification, with view to enhancing P binding in DBRs.
We were mindful in the design of material functionalization to avoid complicated preparation steps, exotic or harmful reagents, and impractical particle sizes to ensure compatibility for large-scale applications in the agricultural landscape. Results indicated that the functionalization of wood media successfully inversed the surface charge, leading to a net positive charge within the favorable range for phosphorus adsorption under reactor-specific conditions (pH 5.5 − 6). The maximum adsorption capacity of functionalized wood and functionalized biochar corresponded to 65.8 mg g-1 and 31.4 mg g-1, respectively, comparing well to values reported in the literature.
DBRs operate under varying hydraulic conditions, which results in variable flow rates, nutrient concentrations, redox status, pH, and many other variables that affect the operation of the bioreactor. The stability of iron hydr(oxide) composites is expected to be sensitive to some of these conditions, especially acidic and anaerobic conditions, which favor dissolution of iron hydr(oxide)s and therefore could adversely affect P removal. Furthermore, there are other likely products of reduced Fe2+ and orthophosphate (HPO42-) that could form under the conditions anticipated. Therefore, the biogeochemical environment in the DBR was characterized to understand the stability of iron hydr(oxide)s and their ability to subsequently remove of phosphorus.
To date, there have been only limited investigations into the stability of iron hydr(oxide)s under real-world bioreactor conditions, and functionalisation studies often neglect the impact of oscillating redox conditions on the stability of Fe-based adsorbents. In light of this, bench-scale woodchip bioreactors were established, both with and without MnO2, to evaluate the redox buffering capacity of MnO2 with view to mitigating the reductive dissolution of iron oxide. This approach aimed to improve the retention of dissolved reactive phosphorus (DRP) on the introduced iron oxide surfaces. It was concluded that iron oxides effectively remove DRP and MnO2 enhances nitrogen (N) removal, with slightly better performance observed in the treatment incorporating Fe oxides and MnO2. Hence, it can be inferred that the addition of manganese and iron oxides proves advantageous as an amendment to the conventional woodchip substrate in DBRs to enhance nutrient removal.
This thesis has demonstrated that Fe-functionalized media can effectively remove DRP in agricultural drainage water. In addition, by incorporating MnO2, Fe oxides can be stabilised under oscillating redox conditions, and therefore the combination of MnO2 and Fe oxides could serve as a practical solution for DBRs to mitigate diffuse pollution in New Zealand. These findings offer insights for redesigning DBRs, providing a clearer understanding of the dynamics of P removal in DBRs, and how functionalized media can be employed in the long term to remove phosphorus from agricultural drainage water, meeting water quality objectives while minimizing P releases.

text: Biogeochemistry of denitrifying bioreactors to enhance phosphorus removal from agricultural subsurface drainage Degradation of water quality due to nutrient over-enrichment has become a global environmental concern. In Aotearoa, agricultural pollution of freshwaters by nutrients is increasing. Therefore, strategies need to be implemented to minimize nutrient pollution in surface waters. Denitrifying bioreactors (DBRs) are a prominent edge-of-field treatment technology to mitigate surface water nitrate loadings from agricultural subsurface drainage. Recent studies have identified that subsurface drainage can also contribute to the loss of phosphorus from agricultural soil. Therefore, this thesis investigates the potential of DBRs to incorporate iron-based materials to sequester phosphorus and reduce pollution of waterways.
There is some evidence suggesting low-level phosphorus removal by woodchip bioreactors alone. However, it is inevitable that woodchips alone do not abiotically remove phosphorus due to the incompatibility between the surface charge of wood at neutral-to-acidic pH values. In this study, raw pinus radiata, and, thermally modified pyrolyzed woodchips were employed for surface modification, with view to enhancing P binding in DBRs.
We were mindful in the design of material functionalization to avoid complicated preparation steps, exotic or harmful reagents, and impractical particle sizes to ensure compatibility for large-scale applications in the agricultural landscape. Results indicated that the functionalization of wood media successfully inversed the surface charge, leading to a net positive charge within the favorable range for phosphorus adsorption under reactor-specific conditions (pH 5.5 − 6). The maximum adsorption capacity of functionalized wood and functionalized biochar corresponded to 65.8 mg g-1 and 31.4 mg g-1, respectively, comparing well to values reported in the literature.
DBRs operate under varying hydraulic conditions, which results in variable flow rates, nutrient concentrations, redox status, pH, and many other variables that affect the operation of the bioreactor. The stability of iron hydr(oxide) composites is expected to be sensitive to some of these conditions, especially acidic and anaerobic conditions, which favor dissolution of iron hydr(oxide)s and therefore could adversely affect P removal. Furthermore, there are other likely products of reduced Fe2+ and orthophosphate (HPO42-) that could form under the conditions anticipated. Therefore, the biogeochemical environment in the DBR was characterized to understand the stability of iron hydr(oxide)s and their ability to subsequently remove of phosphorus.
To date, there have been only limited investigations into the stability of iron hydr(oxide)s under real-world bioreactor conditions, and functionalisation studies often neglect the impact of oscillating redox conditions on the stability of Fe-based adsorbents. In light of this, bench-scale woodchip bioreactors were established, both with and without MnO2, to evaluate the redox buffering capacity of MnO2 with view to mitigating the reductive dissolution of iron oxide. This approach aimed to improve the retention of dissolved reactive phosphorus (DRP) on the introduced iron oxide surfaces. It was concluded that iron oxides effectively remove DRP and MnO2 enhances nitrogen (N) removal, with slightly better performance observed in the treatment incorporating Fe oxides and MnO2. Hence, it can be inferred that the addition of manganese and iron oxides proves advantageous as an amendment to the conventional woodchip substrate in DBRs to enhance nutrient removal.
This thesis has demonstrated that Fe-functionalized media can effectively remove DRP in agricultural drainage water. In addition, by incorporating MnO2, Fe oxides can be stabilised under oscillating redox conditions, and therefore the combination of MnO2 and Fe oxides could serve as a practical solution for DBRs to mitigate diffuse pollution in New Zealand. These findings offer insights for redesigning DBRs, providing a clearer understanding of the dynamics of P removal in DBRs, and how functionalized media can be employed in the long term to remove phosphorus from agricultural drainage water, meeting water quality objectives while minimizing P releases.

year: 2023-12-16

title: Examining therapeutic approaches towards injurious behaviours in adolescents: Perspectives on influence, efficacy & prevention

authors: Parsons, Abby

subjects: NSSI

abstract: This qualitative research investigates professional perspectives on adolescent non- suicidal self-injury (NSSI) and outward-directed injurious (ODI) behaviours through in-depth interviews with twelve professionals across mental health, education, and social services in New Zealand. Utilising thematic analysis, the study reveals insights into how these behaviours represent interconnected manifestations of underlying emotional regulation challenges shaped by individual vulnerabilities, relationship dynamics, and systemic factors. Four key themes emerged: The Duality of Aggressive Expression, Environmental and Developmental Influences, Building Therapeutic Connections, and System Complexities and Bridge-Building. The research extends theoretical understanding by examining how risk factors influence behavioural expression, highlighting the connection between neurodevelopmental differences, trauma histories, and family dynamics. By challenging traditional conceptual frameworks, the study identifies significant gaps between evidence- based interventions and real-world implementation, ultimately offering recommendations for more integrated treatment protocols, enhanced professional support systems, and comprehensive care pathways for vulnerable youth.

text: Examining therapeutic approaches towards injurious behaviours in adolescents: Perspectives on influence, efficacy & prevention This qualitative research investigates professional perspectives on adolescent non- suicidal self-injury (NSSI) and outward-directed injurious (ODI) behaviours through in-depth interviews with twelve professionals across mental health, education, and social services in New Zealand. Utilising thematic analysis, the study reveals insights into how these behaviours represent interconnected manifestations of underlying emotional regulation challenges shaped by individual vulnerabilities, relationship dynamics, and systemic factors. Four key themes emerged: The Duality of Aggressive Expression, Environmental and Developmental Influences, Building Therapeutic Connections, and System Complexities and Bridge-Building. The research extends theoretical understanding by examining how risk factors influence behavioural expression, highlighting the connection between neurodevelopmental differences, trauma histories, and family dynamics. By challenging traditional conceptual frameworks, the study identifies significant gaps between evidence- based interventions and real-world implementation, ultimately offering recommendations for more integrated treatment protocols, enhanced professional support systems, and comprehensive care pathways for vulnerable youth.

year: 2025

title: An evaluation of Te Rau Puawai workforce 100: Perspectives of Te Rau Puawai bursars

authors: Nikora, Linda Waimarie

subjects: Maori students

abstract: The Te Rau Puawai programme is an attempt to change the nature of the Maori
mental health workforce. To do this, Maori with aspirations to work, or to continue to
work in the mental health workforce, are supported, financially and academically, to
complete a tertiary qualification relevant to the field.
To evaluate the Te Rau Puawai programme, the Ministry of Health commissioned the
Maori and Psychology Research Unit of the University of Waikato in July 2001. The
overall aim of the evaluation was to provide the Ministry with a clearer understanding
of the programme including: the perceived critical success factors, the barriers if any
regarding Te Rau Puawai, the impact of the programme, the extent to which the
programme may be transferable, gaps in the programme, and suggested
improvements.
The evaluation team set out to gather the experiences and perspectives of recipients of
Te Rau Puawai services by asking all bursars to complete a questionnaire and
volunteer for follow up interviews or focus groups. Sixty two bursars responded to
our questionnaire, and we complete focus group or individual follow up interviews
with 19 bursars.

text: An evaluation of Te Rau Puawai workforce 100: Perspectives of Te Rau Puawai bursars The Te Rau Puawai programme is an attempt to change the nature of the Maori
mental health workforce. To do this, Maori with aspirations to work, or to continue to
work in the mental health workforce, are supported, financially and academically, to
complete a tertiary qualification relevant to the field.
To evaluate the Te Rau Puawai programme, the Ministry of Health commissioned the
Maori and Psychology Research Unit of the University of Waikato in July 2001. The
overall aim of the evaluation was to provide the Ministry with a clearer understanding
of the programme including: the perceived critical success factors, the barriers if any
regarding Te Rau Puawai, the impact of the programme, the extent to which the
programme may be transferable, gaps in the programme, and suggested
improvements.
The evaluation team set out to gather the experiences and perspectives of recipients of
Te Rau Puawai services by asking all bursars to complete a questionnaire and
volunteer for follow up interviews or focus groups. Sixty two bursars responded to
our questionnaire, and we complete focus group or individual follow up interviews
with 19 bursars.

year: 2002-05-01