Thesis
Water to rock? Tufa formation for capture of contaminants in industrial waste leachate
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2024
- Thesis identifier
- T17105
- Person Identifier (Local)
- 201972918
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Uncontrolled weathering of legacy industrial waste poses a risk of contaminant leaching into groundwaters and surface waters, leading to widespread exposure to plants and living organisms including humans. This risk would be substantially reduced by on-site remediation techniques that would immobilise the leached contaminants at the source. Therefore, the aim of this study was to develop a passive, nature-based, low-cost remediation technique that harnesses metal capture during precipitation of tufa – a freshwater limestone (CaCO3) that forms in Ca-rich streams including industrial waste leachates. This was achieved by: a) characterisation of the geochemistry and formation mechanisms of anthropogenic tufas (i.e., associated with anthropogenic materials) in four hyperalkaline (pH >10) and one neutral (pH 7-8) industrial waste leachates, b) application of these findings towards developing a tufa-imitating column experimental system that could be eventually applied on-site. The most stable long-term contaminant immobilisation would be in a hard tufa. Both the field study and the experimental work demonstrated that flowing water is necessary for hard tufa formation regardless of leachate type. However, the anthropogenic tufa study showed that precipitation mechanism depends on leachate type, which in turn is determined by the type of source waste that also affects the range and concentrations of mobilised contaminants. As a result, the extent of metal capture effectiveness in anthropogenic tufas is related to leachate composition and pH. These factors control whether the tufa would contain accessory minerals (e.g. carbonates, (oxyhydr)oxides), and whether the contaminants form species that are effectively removed by these minerals at given pH and tufa formation mechanism. The column experimental system successfully recreated hard tufa formation by CO2 ingassing into hyperalkaline streams under controlled conditions, and this engineered tufa removed metal contaminants (Cu, Ni, Sr, Zn) from solution. These experiments demonstrated the importance of balanced Ca concentration, alkalinity, and CO2 concentration to achieve CaCO3 precipitation at a stable rate. Importantly, the metals were found to affect CaCO3 precipitation onset and polymorphism and potential coprecipitation of separate minerals. A successful on-site application of the engineered tufa technique would require individual site assessment to determine which contaminants pose the highest risk and which tufa formation mechanism would be more effective at decreasing their aqueous concentrations to levels that do not pose environmental risks.
- Advisor / supervisor
- Cumberland, Susan
- Renshaw, Jo
- MacDonald, John
- Resource Type
- DOI
- Embargo Note
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File | 2024-11-22 | Private |