Françoise Bichai

Using QMRA-based regulation as a water quality management tool in the water security challenge: Experience from the Netherlands and Australia

Innovation in the water sector is at play when addressing the global water security challenge. This paper highlights an emerging role for Quantitative Microbial Risk Assessment (QMRA) and health-based targets in the design and application of robust and flexible water quality regulation to protect public health. This role is especially critical as traditional supply sources are subject to increased contamination, and recycled wastewater and stormwater become a crucial contribution to integrated water supply strategies. Benefits and weaknesses of QMRA-based regulation are likely to be perceived differently by the multiple stakeholders involved. The goal of the current study is to evaluate the experience of QMRA-based regulation implementation in the Netherlands and Australia, and to draw some lessons learned for regulators, policy makers, the industry and scientists. Water experts from regulatory bodies, government, water utilities, and scientists were interviewed in both countries. This paper explores how QMRA-based regulation has helped decision-making in the Netherlands in drinking water safety management over the past decade. Implementation is more recent in Australia: an analysis of current institutional barriers to nationally harmonized implementation for water recycling regulation is presented. This in-depth retrospective analysis of experiences and perceptions highlights the benefits of QMRA-based regulation and the challenges of implementation. QMRA provides a better assessment of water safety than the absence of indicators. Setting a health target addresses the balance between investments and public safety, and helps understand risks from alternative water sources. Challenges lie in efficient monitoring, institutional support for utilities, interpretation of uncertainty by regulators, and risk communication to consumers.

Role of predation by zooplankton in transport and fate of protozoan (oo)cysts in granular activated carbon filtration.

The significance of zooplankton in the transport and fate of pathogenic organisms in drinking water is poorly understood, although many hints of the role of predation in the persistence of microorganisms through water treatment processes can be found in literature. The objective of this study was to assess the impact of predation by natural zooplankton on the transport and fate of protozoan (oo)cysts in granular activated carbon (GAC) filtration process. UV-irradiated unlabelled Cryptosporidium parvum and Giardia lamblia (oo)cysts were seeded into two pilot-scale GAC filtration columns operated under full-scale conditions. In a two-week period after seeding, a reduction of free (oo)cysts retained in the filter bed was observed. Zooplankton was isolated from the filter bed and effluent water on a 30 microm net before and during the two-week period after seeding; it was enumerated and identified. Rotifers, which are potential predators of (oo)cysts, accounted for the major part of the isolated zooplankton. Analytical methods were developed to detect (oo)cysts internalized in natural zooplankton isolated from the filter bed and effluent water. Sample sonication was optimized to disrupt zooplankton organisms and release internalized microorganisms. (Oo)cysts released from zooplankton after sonication were isolated by IMS and stained (EasyStain) for microscopic counting. Both Cryptosporidium and Giardia (oo)cysts were detected in association with zooplankton in the filter bed samples as well as in the effluent of GAC filters. The results of this study suggest that predation by zooplankton can play a role in the remobilization of persistent pathogens such as Cryptosporidium and Giardia (oo)cysts retained in GAC filter beds, and consequently in the transmission of these pathogens in drinking water.

Protection against UV disinfection of E. coli bacteria and B. subtilis spores ingested by C. elegans nematodes.

Nematodes, which occur abundantly in granular media filters of drinking water treatment plants and in distribution systems, can ingest and transport pathogenic bacteria and provide them protection against chemical disinfectants. However, protection against UV disinfection had not been investigated to date. In this study, Caenorhabditis elegans nematodes (wild-type strain N2) were allowed to feed on Escherichia coli OP50 and Bacillus subtilis spores before being exposed to 5 and 40 mJ/cm(2) UV fluences, using a collimated beam apparatus (LP, 254 nm). Sonication (15 W, 60s) was used to extract bacteria from nematode guts following UV exposure in order to assess the amount of ingested bacteria that resisted the UV treatment using a standard culture method. Bacteria located inside the gut of C. elegans were shown to benefit from a significant protection against UV. Approximately 15% of the applied UV fluence of 40 mJ/cm(2) (as typically used in WTP) was found to reach the bacteria located inside nematode guts based on the inactivation of recovered bacteria (2.7 log reduction of E. coli bacteria and 0.7 log reduction of B. subtilis spores at 40 mJ/cm(2)). To our knowledge, this study is the first demonstration of the protection effect of bacterial internalization by higher organisms against UV treatment, using the specific case of E. coli and B. subtilis spores ingested by C. elegans.

Understanding the role of alternative water supply in an urban water security strategy: an analytical framework for decision-making

Innovative analytical tools are needed to address complex sustainability challenges in securing water supply for water-stressed, expanding cities worldwide. Melbournes Alternative Water Atlas is a spatial analytical model that integrates citywide data to evaluate the cost-effectiveness of alternative supply options and their environmental and social benefits. This study presents the methodology employed in the Atlas model to evaluate supply options from four sources (rainwater, stormwater, centralized wastewater recycling, decentralized recycling) to meet the long-term water demand for a range of non-drinking uses in Melbourne. The results of the Atlas analysis highlight preferable options at the local scale with regards to multiple criteria, in order to guide strategic decision-making. Site-specificity and transferability of the Atlas approach are discussed. The Atlas approach can serve as a basis for other international locations to build a locally adapted analytical framework to evaluate the potential of alternative supply options to contribute to water security.

Integrating Water Quality into Urban Water Management and Planning While Addressing the Challenge of Water Security

In the face of growing water demand pressures, urbanisation, and climate change, freshwater resources are becoming scarcer and supply planners are turning to less traditional water sources, such as treated wastewater and urban run-off (stormwater), sources which may pose health risks to consumers. At the same time, traditional surface and groundwater resources are being subject to increased contamination, which contributes to water insecurity. How to address the water quality and public health dimension of urban water quantity challenges is emphasized in this chapter, especially through proper treatment and recycling of polluted run-off and wastewater, which, in the end, can achieve a two-fold benefit of increasing water supply (quantity) and improving the quality of available traditional freshwater resources. With the introduction of alternative sources however, and the delivery of fit-for-purpose water quality, it is crucial to both maintain and demonstrate the level of public health safety and protection in water supply. A systematic but flexible approach is needed to manage public health risks, either by framing and guiding the development of new supply schemes, or by assessing and validating the safety of existing schemes from contaminated sources. Quantitative Microbial Risk Assessment (QMRA) is a method that allows quantitative estimates to be made of microbial risks related to exposure of humans to water, either through drinking or other uses. In this chapter, the role of QMRA is described as a response to a 4-fold need, i.e. the need: (i) for technical guidance in the design of alternative supply schemes; (ii) for regulation to protect public health, both in traditional and alternative supply sources; (iii) for regulatory frameworks and institutions to enable innovation and development; and (iv) to assess new risks from innovative supply schemes and compare them to traditional water supply or other public health risks. Examples of water quality challenges in developing alternatives sources are given. Finally, the role of QMRA in balancing public health concerns with water availability issues and environmental, social, and economic factors in the decision-making process for water security planning is discussed.

Preliminary study on the occurrence and risk arising from bacteria internalized in zooplankton in drinking water

In this study, an environmental sampling campaign was conducted to detect internalized E. coli and C. jejuni bacteria in zooplankton and amoebae samples collected at various stages of three water treatment plants in Amsterdam, the Netherlands. Eight sampling locations were selected and sampling was performed twice, at a two-week interval, at each location. Chlorination was used to inactivate free (external) bacteria in the concentrated zooplankton samples and sonication was used to disrupt zooplankton organisms in order to release and recover internalized bacteria. Zooplankton enumeration was performed by microscopy. No internalized E. coli or C. jejuni bacteria were recovered from all of the samples analyzed. The occurrence of internalized E. coli or C. jejuni bacteria in drinking water was estimated to be lower than one internalized bacteria in 10⁵ zooplankton organisms, as derived from the detection limit of the sampling campaign. By using the QMRA approach and the Beta-Poisson model, a risk of infection of less than 9.2E-6 and 5.9E-5 was estimated for internalized E. coli and C. jejuni in drinking water, respectively. This study remains preliminary due to the limited number of samples taken at each location.