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.@en

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.@en

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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