Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time
Potgieter, Gerhardus Petrus. 2024. A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time. Unpublished doctoral dissertation. Stellenbosch : Stellenbosch University [online...
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Published: |
Stellenbosch : Stellenbosch University
2025
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613950486511616 |
|---|---|
| access_status_str | Open Access |
| author | Potgieter, Gerhardus Petrus |
| author2 | Jacobs, Karin |
| author_browse | Jacobs, Karin Potgieter, Gerhardus Petrus |
| author_facet | Jacobs, Karin Potgieter, Gerhardus Petrus |
| author_sort | Potgieter, Gerhardus Petrus |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Potgieter, Gerhardus Petrus. 2024. A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time. Unpublished doctoral dissertation. Stellenbosch : Stellenbosch University [online]. Available: https://scholar.sun.ac.za/handle/10019.1/131889
Thesis (PhD)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131889 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:44:17.380Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131889 A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time Potgieter, Gerhardus Petrus Jacobs, Karin Van Heerden, Esta Stellenbosch University. Faculty of Science. Dept. of Microbiology. Nitrogen cycle -- Environmental aspects Plants -- Effect of nitrogen on -- South Africa Eutrophication -- South Africa Water quality bioassay Ammonium nitrate -- Environmental aspects Bioremediation -- South Africa Bacterial communities -- Effect of water quality on Bacteria -- Effect of temperature on Gene expression Carbon cycle (Biogeochemistry) -- Environmental aspects UCTD Potgieter, Gerhardus Petrus. 2024. A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time. Unpublished doctoral dissertation. Stellenbosch : Stellenbosch University [online]. Available: https://scholar.sun.ac.za/handle/10019.1/131889 Thesis (PhD)--Stellenbosch University, 2024. ENGLISH ABSTRACT: The nitrogen cycle is an essential ecological process, crucial for the synthesis of key biomolecules and plant growth, thereby maintaining ecosystem balance. It involves the transition of nitrogen through various oxidation states, ranging from ammonia (NH3) with a -3-oxidation state to nitrate (NO3-) at +5. This cycle is driven by fundamental bacterial metabolic activities such as nitrogen fixation, nitrification, and denitrification. These processes collectively facilitate the transformation of nitrogen across different environmental contexts. Human-induced nitrogen imbalances, particularly through industrial activities like mining, have led to severe environmental consequences, including ammonia and nitrate contamination. In regions such as Southern Africa, where mining is a substantial industry, water contamination with nitrate levels far exceeds safe drinking water limits, leading to health issues like methemoglobinemia and cancer as well as harmful ecological effects such as eutrophication. These problems are exacerbated by using ammonium nitrate-based explosives and nitrate leachate from tailings storage facilities (TSF) which release large amounts of nitrogen compounds into the environment from mining operations. The mining industry's legacy, while economically beneficial, poses a major threat to environmental sustainability, emphasising the need for effective nitrate remediation strategies. The role of bacteria in converting ammonia to nitrate to nitrogen gas can be used as an efficient approach to remediate nitrate contamination through the complex processes of fixation, nitrification, and denitrification. However, the effectiveness of these bacterial processes is influenced by environmental factors such as temperature, pH, and bacterial diversity. Understanding the intricate relationships between these factors is crucial for optimising bioremediation strategies and limiting intermediated toxic by-products such as nitrite (NO2-), causing bacterial inhibition, and nitrous oxide (N2O), a greenhouse gas contributing to global warming. Low temperature is a critical factor impacting denitrification, influencing metabolic rates and gene quantity (present/absent), which leads to a marked reduction in nitrate removal efficiency and the production of toxic byproducts. An adapted first-order decay model, incorporating the Arrhenius equation, was utilised to examine denitrification rates at reduced temperatures. The findings indicate an affected decrease in denitrification rates with lower temperatures, however, adapted bacterial communities in environments with optimised carbon-to-nitrogen-to-phosphorus (CNP) ratios demonstrate enhanced denitrification performance, even at temperatures as low as 10 °C. Conversely, sites with indigenous bacterial communities and less regulated carbon sources exhibit much lower denitrification efficiency. Variations in pH was not a concern in this study and are not discussed in detail. Furthermore, it has been established that denitrification pathways in bacteria are modular, not linear, with different species possessing varying components of the pathway. This variability underscores the insufficiency of relying solely on taxonomic data to understand bacterial roles in denitrification. The influence of horizontal gene transfer and environmental stress highlights the critical importance of functional traits and protein-coding genes, such as nif, amo, nor, and nos, in sustaining effective bioremediation systems under low-temperature conditions. Effective management of bacterial communities, with a focus on maintaining balanced CNP ratios and optimising hydraulic retention times (HRT), is crucial for enhancing nitrogen reduction, gene quantitative presence within a community, and biomass production. In controlled environments such as bioreactors or in situ systems, using a carbon molar calculator to adjust carbon levels in proportion to nitrate levels has proven effective to reduce nitrate. Future more, HRT can be accelerated by up to 2.5 times compared to processes with low or unbalanced carbon supplies. Furthermore, maintaining temperatures above 20 °C and ensuring balanced CNP can stimulate communities with an enhanced genetic capacity for denitrification, as evidenced by the increase gene quantity within a community, such as nif, nir, and nor, indicating a potential for complete denitrification. In contrast, stimulating adapted communities at lower temperatures (10 °C) results in reduced quantity of nitrogen cycle genes, indicating a compromised ability for complete denitrification and leading to the accumulation of intermediate nitrogen oxidative species like nitrite. This underscores that, regardless of management strategies and determinants of denitrification rates, achieving complete nitrification necessitates temperatures above 20 °C. The challenge of managing nitrogen contamination underscores the importance of eco-friendly and sustainable remediation strategies. Both chemical and biological methods have its roles, but the efficiency of bioremediation, especially through bioreactors and in situ treatments utilising adapted indigenous bacterial communities, presents promising avenues for addressing nitrate contamination. However, the success of these strategies depends on a deep understanding of the nitrogen cycle, the roles of different bacteria in it, and the environmental factors affecting these processes. As research advances, it is becoming increasingly clear that a calculated approach, tailored to specific natural and physico-chemical conditions and leveraging the capabilities of bacteria, is essential for effectively addressing the challenges of nitrogen contamination. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2025-04-07T10:14:38Z 2025-04-07T10:14:38Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131889 Stellenbosch University 114 pages : iilustrations (some color) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Nitrogen cycle -- Environmental aspects Plants -- Effect of nitrogen on -- South Africa Eutrophication -- South Africa Water quality bioassay Ammonium nitrate -- Environmental aspects Bioremediation -- South Africa Bacterial communities -- Effect of water quality on Bacteria -- Effect of temperature on Gene expression Carbon cycle (Biogeochemistry) -- Environmental aspects UCTD Potgieter, Gerhardus Petrus A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time |
| title | A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time |
| title_full | A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time |
| title_fullStr | A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time |
| title_full_unstemmed | A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time |
| title_short | A calculated approach to nitrate bioremediation in temperature-variable mining environments: integrating adapted bacterial stimulation, carbon balancing, and hydraulic retention time |
| title_sort | calculated approach to nitrate bioremediation in temperature variable mining environments integrating adapted bacterial stimulation carbon balancing and hydraulic retention time |
| topic | Nitrogen cycle -- Environmental aspects Plants -- Effect of nitrogen on -- South Africa Eutrophication -- South Africa Water quality bioassay Ammonium nitrate -- Environmental aspects Bioremediation -- South Africa Bacterial communities -- Effect of water quality on Bacteria -- Effect of temperature on Gene expression Carbon cycle (Biogeochemistry) -- Environmental aspects UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131889 |
| work_keys_str_mv | AT potgietergerharduspetrus acalculatedapproachtonitratebioremediationintemperaturevariableminingenvironmentsintegratingadaptedbacterialstimulationcarbonbalancingandhydraulicretentiontime AT potgietergerharduspetrus calculatedapproachtonitratebioremediationintemperaturevariableminingenvironmentsintegratingadaptedbacterialstimulationcarbonbalancingandhydraulicretentiontime |