AMVD Reference Document revision

Knowledge on pathogen removal during drinking water treatment

Sources of drinking water such as surface water can contain high numbers of pathogenic viruses, bacteria and other micro-organisms. The drinking water treatment must remove or kill these organisms so that the drinking water is safe and represents no threat to public health. The acceptable concentration of pathogens is in the order of 1 organism per one million litres of water. This low level cannot be demonstrated by means of water analyses. Drinking water utilities therefore need to demonstrate, by means of an AMVD, that the risk of infection resulting from consumption of drinking water is lower than 1 infection per 10,000 people per year. This requires current knowledge about the degree to which treatment processes remove or kill pathogens, and under which conditions that goal is achieved. This knowledge is dispersed in the scientific literature and a good overview of all the knowledge is lacking. This is the reason that earlier Joint Research Programme (BTO) research developed the AMVD Reference Document, in which this knowledge is collected. This knowledge needs to be regularly supplemented, and new treatment processes need to be added. The interpretation of the data in the context of Dutch practice demands a thorough data analysis. The recent period indicates that more attention needs to paid to this aspect, since the data from the literature are not always complete nor aligned. For this reason, the Reference Document has to be revised and supplemented.

Improved set-up, interpretation and supplementation of AMVD Reference Document

The following activities are to be carried out to improve the Reference Document:

1. Soil passage revision

Raw data from the four Dutch studies on the removal of micro-organisms by means of soil passage are to be collected or retrieved and controlled, because the knowledge about the situation and the available data for these studies are the most extensive. All these data will then be processed in the same manner to derive parameters for the mathematical model that predicts soil-passage removals. The adjusted data and results will be incorporated into the Reference Document. This activity will contribute to developing a better approach for data selection, quality control and interpretation of studies that are included in the Reference Document, and also apply to other treatment processes.

2. Reference Document problem areas and wishes

An inventory will be made of all the problem areas in the current set-up of the Reference Document. This concerns all the steps, such as study selection, data extraction, quality control, missing information, data analysis, interpretation for the AMVD, user interface, and safeguarding continuity for support and maintenance. Besides the demands and wishes that were gathered during the earlier set-up of the Operational Code 8-2020 Protocol AMVD Reference Document, KWR also will assemble its own experiences and discussion records. In addition, the drinking water utilities will be asked about their own wishes and experiences regarding the current version. Discussions will also be held with RIVM (National Institute for Public Health and the Environment) and in the WIR (infection risk working group) on how best to deal with the input of knowledge and expertise in the assessment of the studies’ quality, and how this translates to the AMVD. This will result in a plan for a revision of the Reference Document (in its current form in PCD 8 AMVD Reference Document).

3. Redesign of Reference Document

The Reference Document (database and user interface) set-up will be adjusted on the basis of the plan produced by the activities carried out under item 2 above. ‘Dummy’ user interfaces will be used to test the extent to which the adjustments meet the needs of the drinking water utilities. The new approach will also be tested on the processes that are already included in the current Reference Document (whether with a user interface or not), namely: UV disinfection, Ozonation, Soil Passage, Reverse Osmosis, Rapid Filtration and Activated Carbon Filtration. In this activity, the data themselves will not be expanded. The objective is to test whether the revised approach applies to various processes, or whether specific adjustments are needed. Adjustments in the databases with quality control will be directly implemented, so that new data can be directly included in items 4 and 5 and quality control take place.

4. Extension with WHO data

During 2018-2022 KWR and the University of Colorado in Boulder (UCB) collaborated in the collection of information on the effectiveness of treatment processes for the revision of the Guidelines for Drinking Water Quality of the World Health Organization (WHO). UCB will share with KWR the data from the processes they analysed. KWR will subject these data to quality control according to the revised approach and incorporate them into the Reference Document. Whenever necessary, additional literature research will be carried out to supplement or control the data.

5. UV LED disinfection

UV LED disinfection has, until very recently, only been used in small-scale treatment devices. In the meantime, a full-scale UV LED installation started operating in England. This means that UV LED is becoming a practical alternative to low- and middle-pressure mercury lamps. The use of these mercury lamps is no longer permitted (EU Directive 2011/65/EU), but the prohibition was exceptionally extended for UV lamps until 2024 because of the absence of an alternative. Now that UV LED presents an alternative, this exceptional status will possibly come to a timely end. UV LED also offers further possibilities in terms of lower energy consumption, control over the exact wavelengths that influence the degree of inactivation of pathogens, and other possible configurations, since various forms of ‘lamps’ are feasible. A literature study will be done and experiences collected with UV LED disinfection of drinking and other water on a practical scale. On this basis the practical feasibility, consequences and potential of UV LED for the Dutch drinking water sector will be determined. Besides the reports from this research, relevant data will be collected in the Reference Document. These will differ in part from the information currently presented on UV disinfection. Accordingly, a separate set-up will be developed for UV LED disinfection. This research will be carried out in collaboration with KWR treatment experts, and the project will be brought to the attention of the BTO Treatment theme research group.

Reviewed approach and set-up for practical application of AMVD Reference Document

The project will lead to a review of the approach and set-up of the Reference Document compared to the current approach, as described in PCD8 AMVD Reference Document. In addition, a new user interface will be designed which can be implemented in a follow-up project. The approach will also be published in a scientific paper, as an international, scientific quality-assurance. This is required for acceptance by RIVM and the Human Environment and Transport Inspectorate (ILT). An instruction video will also be made for users at drinking water utilities, so that they can themselves use the Reference Document in setting up Analyses of Microbial Safety of Drinking Water.