The necessity for sustainable industrial processes and solutions has been intensified by climate change, which has led to an increased focus on enhancing resource efficiency and reducing greenhouse gas emissions. In accordance with the principles of the circular economy, the impl
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The necessity for sustainable industrial processes and solutions has been intensified by climate change, which has led to an increased focus on enhancing resource efficiency and reducing greenhouse gas emissions. In accordance with the principles of the circular economy, the implementation of improved water-smart solutions and enhanced water management processes, including the reuse and recycling of wastewater and the recovery of resources such as water, energy and nutrients, represents a pivotal strategy for addressing challenges such as climate change and water pollution.
This dissertation examines novel bio-composite materials derived from resources recovered from the water sector. These materials incorporate natural fibres derived from untreated wastewater (i.e., cellulose fibres) or surface water management (i.e., reed and grass fibres), as well as fillers such as calcite derived from drinking water softening processes or agricultural waste (i.e., coconut shells, olive powder, and food residue). Bio-based resins, such as polyester with a reduced styrene content or furan resin, containing furfuryl alcohol, serve as binders.
The presence of a wide range of pollutants has a significant impact on water resources as a result of human activities. It is therefore imperative that comprehensive testing is conducted to ensure that the utilisation of recovered resources does not result in any adverse effects on human health or the environment. It is crucial to emphasise that, because of their derivation from recycled raw materials, the utilisation of the novel bio-composite materials should not be assumed to be intrinsically risk-free. It is therefore imperative that a comprehensive risk assessment of the environmental and human health risks associated with the production and application of the new bio-composite materials is conducted.
The overall aim of this research project is to develop an approach for the evaluation of potential risks to human health and the environment that may result from the production and application of the new bio-composite materials. In line with this, four research questions have been formulated to conduct this study:
- What are the main risks and related hazards associated with the production of new resource recovery-based bio-composite materials and their applications and how are these interlinked?What existing methods can be potentially used (and with what modifications) and which new ones need to be developed to assess these risks?
- What is the best approach to define and quantify the human health risks involved in the production of bio-composite materials?
- What is the environmental risk associated with the use of the new bio-composite materials in the aquatic environment? More specifically, what is the risk in case of canal bank protection elements made from these new materials?
- What is the environmental risk associated with the use of new bio-composite materials based building façade elements and how does the weathering of these elements affect this risk?
Above research questions have been addressed and answered in Chapters 2 – 5 of this dissertation. Below, a summary of the work done in order to address the formulated research questions is provided.
A comprehensive literature review, detailed in Chapter 2, was conducted at the outset of this work to identify the principal hazards and associated risks involved in drinking water and wastewater treatment plants, water reuse, and water-based resources recovery. The literature study identified potential microbial and chemical contaminants of the raw materials used to produce the new water-based resource recovery bio-composite materials. These contaminants may pose a risk to human health and the environment. Nevertheless, it was found that no risk assessment methodologies have yet been used to assess the potential human health and environmental risks associated with the production and application of the new bio-composite materials.
The novel human health risk assessment framework, which is described in Chapter 3, employed a qualitative risk analysis as the initial step, followed by a quantitative risk analysis. The Hazard and Operability (HAZOP) method identified the principal hazards during the production, and the qualitative Event Tree Analysis (ETA) methodology created a corresponding risk map. The results of the qualitative risk assessment indicated that the main risks of new bio-composite materials are caused by chemical and microbial contamination, which can have a negative impact on human health and the environment. A quantitative human health risk assessment was conducted on four alternative new bio-composite materials, employing both Quantitative Chemical Risk Assessment (QCRA) and Quantitative Microbial Risk Assessment (QMRA) methodologies, with deterministic and stochastic approaches. The results of the chemical risk assessment indicated that the cancer risk from styrene and furfuryl alcohol exceeded the established safety threshold. Similarly, the microbial risk assessment identified significant concerns with E. coli in cellulose fibres, with the risk exceeding safety limit. The assessments were conducted under the most unfavourable circumstances, without the use of personal protective equipment (PPE) or safety protocols. Furthermore, the assumption of maximum exposure to contaminants was made due to the limited availability of input data, which resulted in an overestimation of the overall risk.
The presence of chemical contamination in raw materials used for the production of new bio-composite materials gave rise to concerns not only for human health but also for potential negative environmental impact. In order to assess the environmental risks involved, two applications of these new materials were considered in this study: (a) canal bank protection elements, which prevents soil from collapsing into the water and (b) façade building elements as decorations panels.
To assess the environmental risks of chemical release, from the bio-composite materials used as canal bank protection, laboratory column leaching tests were conducted. This preliminary step provided data for an approximate environmental risk assessment in real-world conditions. The environmental risk assessment framework, developed in accordance with European guidelines, as detailed in Chapter 4, showed that the concentration of chemicals leached into surface water was within safety threshold. However, styrene and furfuryl alcohol contained in the resins may still pose a concern to environmental risk. It is crucial to acknowledge that the interpretation of these results should be approached with caution, given the absence of on-site data and the numerous assumptions made, including instantaneous mixing of the leaching chemicals and the absence of Brownian motion. Furthermore, the background concentrations in freshwater and the fate and degradation of chemicals in surface water were not considered. Also, the leaching process was evaluated over time, with the observation of a plateau indicating a significant slowdown in the leaching process accompanied by a reduction in the driving force, thereby providing a better understanding of the leaching behaviour.
Bio-composite materials utilised as façade construction elements are more susceptible to adverse weather conditions than those used for canal bank protection. Chapter 5 presents an analysis of potential leaching from bio-composites on a real-world building of a pumping station in the Netherlands. Two bio-composite alternatives were tested, and two samples per material were used: one new sample (as the initial application) and one UV-treated sample (as the long-term application after weathering) per material, for a total of four samples. The samples were subjected to leaching tests simulating two rainfall events of a duration of one hour. The risk assessment demonstrated that no leached chemicals exceeded the safety threshold, with no detection of styrene or furfuryl alcohol in the leaching effluent samples. However, these findings should be interpreted with caution due to the limited input data and the assumptions made, including the lack of on-site data and the focus on a single rain event rather than analysing leaching over a longer time period. The weathering treatments affected the materials in different ways based on their resin composition. Material M3 (made of polyester resin) exhibited aesthetic changes, while Material M4 (made of furan resin) demonstrated increased roughness, reduced water resistance and fibre detachment. Microscopic examination revealed significant wrinkling in M4, indicating that environmental exposure significantly affects these materials.
Overall, it can be concluded (Chapter 6) that both microbial and chemical risks are inherent in the production and applications of new bio-composite materials considered in this thesis. These risks originate from the utilization of specific raw materials, including calcite from drinking water, cellulose derived from wastewater, reed and grass sourced from surface water management conducted by water boards, as well as the resins and additives employed in new materials. The framework developed in this research, which includes laboratory testing, modelling and risk assessment methods, has been validated as applicable to the case studies used in this work. Being generic in nature, the framework also shows potential for human health and environmental risk assessments associated with different future applications of new bio-composite materials.@en