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. ... Read more

A new type of bio-composite material is being produced from water-recovered resources such as cellulose fibres from wastewater, calcite from the drinking water softening process, and grass and reed from waterboard sites. These raw materials may be contaminated with pathogens and chemicals such as Escherichia coli, heavy metals, and resin compounds. A novel risk assessment framework is proposed here, addressing human health risks during the production of new bio-composite materials. The developed framework consists of a combination of existing risk assessment methods and is based on three main steps: hazard identification, qualitative risk mapping, and quantitative risk assessment. The HAZOP and Event Tree Analysis methodologies were used for hazard identification and risk mapping stages. Then, human health risks were quantitatively assessed using quantitative chemical risk assessment, evaluating cancer and non-cancer risk, and quantitative microbial risk assessment. The deterministic and the stochastic approaches were performed for this purpose. The contamination of raw materials may pose human health concerns, resulting in cancer risk above the threshold. Microbial risk is also above the safety threshold. Additional analysis would be significant as future research to better assess the microbial risk in biocomposite production. The framework has been effectively used for chemical and microbial risk assessment. ... Read more

The concept of circular economy, aiming at increasing the sustainability of products and services in the water and other sectors, is gaining momentum worldwide. Driven by this concept, novel bio-composite materials produced by recovering resources from different parts of the water cycle are now manufactured in The Netherlands. The new materials are used for different products such as canal bank protection elements, as an alternative to similar elements made of hardwood. As much as these new materials are appealing from the sustainability point of view, they may leach toxic substances into the aquatic environment given some of their ingredients, e.g., cellulose recovered from wastewater treatment. Therefore, a methodology for the assessment of related environmental risks is needed and it does not exist currently. This paper addresses this knowledge gap by presenting a framework for this. The framework is based on European environmental risk assessment guidelines, and it includes four key steps: (i) hazard identification, (ii) dose–response modelling, (iii) exposure assessment and (iv) risk characterisation (i.e. assessment). As part of the first step, laboratory leaching tests were carried out to evaluate the potential release of specific chemical substances such as heavy metals and resin compounds into the aquatic environment. Laboratory test results were then used as input data to evaluate the risk of potential leaching from canal bank protection elements into surface water. A deterministic model was used first to identify the chemicals exceeding the guideline threshold. Subsequently, a stochastic model was applied to evaluate the environmental risks across a range of leachate concentrations and water velocities in the canal, thereby simulating a broader spectrum of possible situations. The risk analyses were conducted for four alternative bio-composite materials made of different ingredients, two different flow conditions (stagnant water and advective flow) in two types of canals (wide ditch and primary watercourse) and for two different water levels based on season conditions (summer and winter conditions). The results obtained from leaching tests identified Cu, Mn, Zn, styrene and furfuryl alcohol as potentially troublesome chemicals. In the case of stagnant water, the absence of a flow rate increases the residence time of the chemicals in the surface water, resulting in a higher PEC/PNEC (i.e. risk) value. However, under stagnant case conditions, environmental risks for all chemicals considered turned out to be below the safety threshold. In the advective case, the existence of a flow rate, even at low velocities simulating the conditions of ‘almost no flow,’ contributes to increased dilution, resulting in lower PEC/PNEC ratio values. The results presented here, even though representing real-case scenarios, are only indicative as these are based on laboratory leaching tests and a number of assumptions made. Additional field tests involving collecting and analysing water and sediment samples from the canal where the canal bank protection elements are located, over a prolonged period, are required to come up with more conclusive findings. ... Read more

The increasing focus on sustainability and circularity is driving the global production of environmentally friendly products. The Netherlands started producing new bio-composite materials which are created by reclaiming resources from various sectors of the water industry. These materials can be used for a variety of applications including façade elements in buildings. However, their potential environmental impact, particularly with regard to leaching of potentially harmful substances into surface water, necessitates further evaluation. To address this issue, a systematic environmental risk assessment methodology combined with novel experimental data is presented here. To collect this data, façade panels made of two different bio-composite materials were first subjected to a series of laboratory tests, including analysis in both new and weathered forms, the latter subject to a cyclic UV radiation and high humidity, in order to simulate the effects of aging. Leaching tests were then conducted to determine the potential release of specific chemical substances such as heavy metals and resin compounds, under two different rainfall conditions (every day and more extreme). The data generated this way was used to perform the risk assessment using the existing European ERA framework. The results obtained reveal different leaching behaviour of the new and weathered samples, as well as between the two analysed bio-composite materials, depending on the rain intensity. To overcome the uncertainties caused by the limited input data, a sensitivity analysis was carried out whereby leaching concentrations and rainfall intensities were varied and their influence on the environmental risk was assessed. The results obtained demonstrated that, despite some variability, both materials appear safe to use, i.e., with estimated risks below the established safety threshold. While these findings provide a preliminary indication, they are based on laboratory conditions and assumptions hence further field studies are recommended to obtain more definitive conclusions. ... Read more

Bio-composite materials made from resources recovered from the water cycle are the future of the holistic approach towards sustainable wastewater treatment. The raw ingredients for these materials are coming from contaminated sources such as wastewater resources, water plants from surface water etc.. Thus, different risks like human health, environmental and product quality risks need to be assessed. Existing literature was analysed regarding these risks, especially methods concerning the risk assessment in wastewater and drinking water treatment and water/wastewater-based resource recovery for reuse. The reviewed literature identified several risk assessment methods such as FMEA, FMECA, FTA, QMRA and QCRA as frequently used ones for these purposes. However, no dedicated methods were identified for the corresponding risk assessments related to bio-composite materials representing key knowledge gaps. The literature review also showed that the above identified risk assessment methods cannot be directly applied for bio-composite materials as many required input data are missing. To overcome above gaps, future research directions have been identified. These include use of qualitative risk assessment methods such as HAZOP and ETA to first identify hazards and map the risks. Once this is done, QMRA and QCRA could be used in combination with Monte Carlo analysis to assess the actual risks. However, before this can be done, additional work should be carried out to collect the missing data required for the use of these methods in the context of bio-composite materials. In addition, additional experimental work such as column leaching tests should be carried out to assess the environmental risks, in particular, looking at the release of toxic chemical compounds such as heavy metals in the aquatic environment. Finally, a list of quality requirements for bio-composite material and related products (e.g. requirements for mechanical properties, purity of raw materials, etc.) should be made, so that the related product quality risks can be assessed.
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