Bioassays as a useful tool in the circular economy

Because fresh water from groundwater or surface water is scarce during dry periods, there is growing interest in reusing rainwater, and the treatment of treated domestic and industrial waste water. This requires studying the potential risks that may arise along the way as a result of the circulation and accumulation of microbial and chemical contaminants. Bioassays have proven effective for the assessment of the chemical quality of water sources and the effectiveness of water treatment processes. Could this instrument also be used to test water quality during water reuse? And which bioassay should be used?

Broad spectrum

These questions were addressed by the report ‘Bioassays for Water Quality Assessment in the Circular Economy’. Research in the past focused on considerations underlying the selection of bioassays and on the interpretation of the results in different water flows. The report describes how the applicability of a broad spectrum of bioassays was investigated for alternative sources and water use/reuse applications. “When bioassays are used for this purpose, water utilities and other stakeholders can make informed decisions about alternative sources and water reuse applications on the basis of water quality data,” says KWR researcher Astrid Reus. She presented her findings at the WiCE Inspiration Session recently.

Applicability of bioassays

The results show that bioassays are suitable for demonstrating the presence of substances with specific actions in the situations described. They can also be used to assess the effectiveness of a water treatment process. In addition, bioassays are a useful tool for screening and prioritising water samples for further assessment, including chemical identification and integrated risk assessment.

Determining toxicity

The bioassay results seen during the study can be linked to specific substances to determine the cause of the observed toxicity by combining the bioassay results with broad chemical analysis and effect-directed analysis (EDA). The evaluation of the results using the available experiment databases and predictions using computer models are also essential here. When the cause of a measured effect is explained in a bioassay, this information helps to make the right decisions during the production of drinking water in order to prevent any risks for health or the environment. Bioassays are valuable as support tools for decision-making about the use of alternative sources and water reuse applications. To optimise risk assessment, a good standard set needs to be selected from the available options.