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Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling
Kotze, A. 2025. Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/c00923e7-51a2-49ef-90e6-328600fea7f3
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867614035988447232 |
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| access_status_str | Open Access |
| author | Kotze, Andrea |
| author2 | Dorfling, Christie |
| author_browse | Dorfling, Christie Kotze, Andrea |
| author_facet | Dorfling, Christie Kotze, Andrea |
| author_sort | Kotze, Andrea |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Kotze, A. 2025. Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/c00923e7-51a2-49ef-90e6-328600fea7f3 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132595 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:45:38.927Z |
| 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:10019.1/132595 Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling Kotze, Andrea Dorfling, Christie Akdogan, Guven Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Phosphorus -- Environmental aspects Sewage sludge -- Utilization Flash point (Thermodynamics) UCTD Kotze, A. 2025. Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/c00923e7-51a2-49ef-90e6-328600fea7f3 Thesis (MEng)--Stellenbosch University, 2025. ENGLISH ABSTRACT: A significant amount of phosphorus is being lost in sewage sludge and not recovered to reduce the dependency of the market on primary phosphorus production. As primary resources are declining, it is becoming critical to source additional phosphorus from other sources such as sewage sludge which contains a significant concentration of this valuable nutrient—typically between 4% to 9%. Many European countries are also introducing tighter restrictions on sewage sludge handling to ensure that more effort is being made to recover the phosphorus before disposal of the material. This study aimed to investigate the processes that are available for phosphorus recovery from sewage sludge and to compare two of these existing processes (AshDec and Ash2Phos) to a novel phosphorus recovery process, FlashPhos. The Flashphos process is a thermochemical process removing phosphorus as P4 through carbon reduction. AshDec is a thermochemical process using sodium sulphate to produce a high phosphorus-containing slag. Ash2Phos is a wet-chemical extraction process using HCl to produce a calcium phosphate product. The comparison of these three processes was achieved through a comprehensive analysis of the wastewater treatment process, different points of phosphorus recovery and the existing and under-development phosphorus recovery techniques from sewage sludge. Mass and energy balances were developed for the FlashPhos, AshDec and Ash2Phos processes to enable a reasonable comparison between these three processes. The processes were compared based on energy requirement and the possible phosphorus recovery. A sensitivity analysis was completed to evaluate the performance of these three processes taking into consideration the high variability in the composition of the sewage sludge and subsequent sewage sludge ash; this indicated whether certain processes might be better suited to a specific sewage sludge composition. The findings from the mass and energy balances indicate that both AshDec (5.3 MJ/kg ash) and FlashPhos (6.9 MJ/kg ash) processes require less energy than Ash2Phos (4.1 MJ/kg ash cooling and 3.5 MJ/kg ash incineration). All three processes achieve a high phosphorus recovery exceeding 80%. The sensitivity analysis reveals that the energy requirement and phosphorus recovery are significantly influenced by the composition of the sewage sludge, with the FlashPhos process being particularly sensitive to iron content which reduces the amount of phosphorus recovery, while AshDec's recovery is affected by calcium and phosphorus levels. The thesis further emphasizes the potential for the FlashPhos process to be a competitive option for phosphorus recovery due to its comparable energy requirement and effective yield. Recommendations for future research include expanding the sensitivity analysis to incorporate additional parameters, exploring a broader range of regression models, conducting detailed speciation analyses of sewage sludge and ash components and including economic criteria and environmental impact assessment results in the process comparison. These enhancements aim to refine the understanding of the processes involved and optimize phosphorus recovery methods. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2025-06-11T11:58:50Z 2025-06-11T11:58:50Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132595 Stellenbosch University xi, 118 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Phosphorus -- Environmental aspects Sewage sludge -- Utilization Flash point (Thermodynamics) UCTD Kotze, Andrea Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling |
| title | Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling |
| title_full | Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling |
| title_fullStr | Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling |
| title_full_unstemmed | Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling |
| title_short | Comparison of three processes for phosphorus recovery from wastewater sludge using process modelling |
| title_sort | comparison of three processes for phosphorus recovery from wastewater sludge using process modelling |
| topic | Phosphorus -- Environmental aspects Sewage sludge -- Utilization Flash point (Thermodynamics) UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132595 |
| work_keys_str_mv | AT kotzeandrea comparisonofthreeprocessesforphosphorusrecoveryfromwastewatersludgeusingprocessmodelling |