Prediction and validation in organic micropollutant removal

QSARs (quantitative structure-activity relationships) are a particularly useful instrument in this regard. This is why the project focuses on the further validation of existing, and the development of new, QSARs. Moreover, new developments will be closely monitored, in the field of membranes for instance. The emphasis will be on the extension and widening of AquaPriori. The activities will also result in an (improved) tool that can be used to make the research application-ready.

Supplying safe and reliable drinking water by removing micropollutants

Organic micropollutants (OMPs) in sources of drinking water are regularly in the news. Two years ago pyrazole was the centre of attention, and this year GenX was found in surface and drinking water in the Province of South Holland. The quantities of these and other OMPs in the sources are usually very low and not harmful to health, but the water sector wants to act proactively and continue supplying safe and reliable water. The central question is how to remove OMPs as efficiently as possible during the water treatment, and how to estimate this in advance. In principle there are three options for the removal of OMPs: 1) separation through the use of membranes, 2) removal through adsorption, and 3) degradation via biological or oxidative processes. Which process is the most suitable depends on the local conditions and on the specific properties of the OMP.

Models are being developed in the AquaPriori software tool to describe a statistical relationship (quantitative structure-activity relationship, or QSAR) between the molecular structure of the OMP and the behaviour in activated carbon filtration and reverse osmosis (RO). Research was conducted previously on the development of QSARs for UV/H₂O₂ processes. The AquaPriori models still need to be validated at the drinking water companies, and there is an additional interest in extending the tool with models for oxidation and biological processes.

Although it will always be necessary to establish experimentally the extent to which a specific technique is suitable for the removal of a specific pollutant under particular local conditions, it is very important to be able to assess in advance which treatment technique is the most suitable, and how effectively the current treatment process deals with the pollutant. QSARs are a particularly useful instrument in this regard. This is why the project focusses on the further validation of existing QSARs (an initial validation of AquaPriori has already been completed in the TKI project), and the development of new QSARs. Moreover, new developments will be closely monitored, in the field of membranes for instance. The project consists of separate work packages.

Extension and widening of AquaPriori

Researchers will carry out the following activities in the project:

Extension of AquaPriori for ACF and RO (work package 1)

In the first place, the tool will be reinforced with regard to ACF and RO. This involves the further validation of the existing models, an extension with existing and new NF and RO membranes, and the effect of competition by NOM on ACF processes. New contaminants will also be added in the tool.

Extension of AquaPriori for oxidation processes (work package 2)

Work will simultaneously be done on broadening the AquaPriori model by extending the tool with models for oxidation processes. Work was done in the past on QSARs for UV/H₂O₂ processes, and this will be further elaborated. Moreover, ozone processes will also be added.

Extension of AquaPriori for biodegradation processes (work package 3)

The research will also explore the possibility of developing models for biodegradation in AquaPriori.

Risk perception of undesirable substances; connection with Chemical Safety theme group (work package 4)

Within the Chemical Safety theme group [‘Risk perception and interpretation (chemical) water quality of drinking water’ project] and the Customer theme group, under the subject of ‘perception and trust’, responding to contaminations in drinking water sources is a key issue. The research in these two theme groups is conducted in close coordination with Vewin’s Communication Steering Group. In consultations with the Chemical Safety and the Customer theme groups, it was agreed that the Treatment theme group will connect with the above-mentioned project among others by: working together in determining the current state of affairs; laying out an action plan (with emphasis of communications; indicating that the latest treatment techniques are applied); and organising a workshop on the subject. The central role and leadership is the responsibility of the Chemical Safety theme group; the Treatment theme group only provides input for the workshop(s) and the reporting, but does not itself produce any accounts or reports.

Models, insight and protocol

The projects outcomes will be:

• Models in the area of ACF and RO, which can predict the removal of micropollutants in full-scale installations under operating conditions.
• Extension of these models with the effect of NOM on ACF and other types of RO membranes.
• Models in the area of (advanced) oxidation, which can predict the removal of micropollutants in full-scale installations under operating conditions.
• Insight into the possibilities of establishing QSBRs (quantitative structure-biodegradation relationships) for the biodegradation of specific micropollutants.
• A protocol for ‘undesirable substances in drinking water’, with a particular focus on treatment possibilities. This will be set up in close collaboration with the Chemical Safety and Customer theme groups.

The results of the AquaPriori research will also be set down in a report, and processed in models, which will lead to modifications to the tool. This will make it possible to predict, under particular conditions, the removal and/or degradation of substances by means of adsorption or activated carbon or other type of filter, RO or (advanced) oxidation. If possible, such a model will be developed for a small number of micropollutants (about which we have pertinent information) and biodegradation. These results will possibly be the subject of a peer-reviewed journal and/or trade publication article, and/or be presented at a congress.

With regard to the protocol on undesirable substances, the researchers will organise a workshop for the drinking water companies. The findings will be published in collaboration with the two other theme groups.