Thesis
Can wastewater treatment plants cope with future nanoparticle loading scenarios?
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2022
- Thesis identifier
- T16145
- Person Identifier (Local)
- 201680822
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The increased production and utilization of nanomaterials has brought significant advantages and developments in many sectors. The application of nanoparticles (NPs), however, comes with the challenge of their growing release into wastewater streams which could eventually enter the natural environment. Exposure to NPs can lead to a wide range of chronic and acute toxic effects on living organisms. These may vary from DNA damages, impairment of metabolic functions, organ injuries and ultimately death. Furthermore, NPs can also interact with other chemical substances. This has the potential to affect their behaviour and, in some cases, increase the toxicity of the generated NPs – chemicals mixtures. The presence and toxicology of NPs in conventional wastewater treatment plants has received increasing attention, attempting to understand their transport through, and impact on, wastewater treatments systems. While these efforts have largely focused on single NP types and concentrations equal to or below the predicted environmental concentrations, few attempts have investigated NP mixture scenarios as well extremely high NP concentrations. Further investigation into high concentration scenarios are needed due to the likely increase in NP use and therefore release into wastewater in the future. Moreover, further examination of NP removal in mixed NP systems is needed as most wastewaters will contain a mixture of NPs. In addition, the time dependent removal profile of NPs in wastewater secondary treatments has largely been ignored, with most studies focussing on the single endpoint of NP bulk removal. These current gaps indicate that we are poorly prepared to deal with nanoparticle pollution. Extreme NP release events can occur in case of accidents, unregulated discharge, and these spike events are of great concern for water and wastewater companies. The main aim of this PhD was to assess whether conventional and emerging secondary biological treatments can remove single and NP mixtures from wastewater and hence prevent their release into receiving water bodies. Firstly, a range of protocols for processing and analysing NPs were examined to determine the most effective. From this, NP determination was achieved via development and validation of a single analytical method based on microwave assisted acid digestion followed by inductively coupled plasma optical emission spectroscopy (IPC-OES). The results demonstrated the robustness of the method to quantify single and, most importantly, NP mixtures in aqueous solutions. The removal of NPs was studied as a function of NP type, concentration, time and bacteria nature. Activated (aerobic) and granular (anaerobic) sludge microorganisms were used to treat wastewater spiked with nano sized copper oxide (CuO), titanium dioxide (TiO2) and zinc oxide (ZnO). NPs – bacteria experiments prove that wastewater biological treatments can reduce NP release into the environment. Overall, activated sludge had greater efficiency than anaerobic granules. Activated sludge yielded NP removal greater than 90% in most of the experimental conditions tested within 180 minutes. However, the treatment efficacy was reduced at high NP mixture concentration. The presence of anaerobic granules could remove up to 70% of the NPs present in wastewater. However, these microorganisms did not seem to suffer reduction of removal performances in a NP concentration dependent manner. The effects of natural secondary wastewater liquor on NP behaviour were also assessed. Results show that primary treated wastewater liquor has the potential to stabilize NPs and hence reduce their removal due to aggregation driven sedimentation. The research presented here highlights the importance of the presence of biologically mediated secondary treatments to cope with the increasing occurrence of NPs in wastewater. The results indicate that microorganisms are an effective tool to remove NPs from sewage and therefore protect the natural aquatic environment. These findings hold implications for the fate and transport of nanoparticles through environmental systems and wastewater treatment plants.
- Advisor / supervisor
- Phoenix, Vernon
- Resource Type
- DOI
- Funder
Relations
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