Arsenic (As) is a highly toxic element which naturally occurs in drinking water. In spite of substantial evidence on the association between many illnesses and chronic consumption of As, there is still a considerable uncertainty about the health risks due to low As concentrations in drinking water. In the Netherlands, drinking water companies aim to supply water with As concentration of <1 μg/L – a water quality goal which is tenfold more stringent than the current WHO guideline. This paper provides (i) an account on the assessed lung cancer risk for the Dutch population due to pertinent low-level As in drinking water and cost-comparison between health care provision and As removal from water, (ii) an overview of As occurrence and mobility in drinking water sources and water treatment systems in the Netherlands and (iii) insights into As removal methods that have been employed or under investigation to achieve As reduction to <1 µg/L at Dutch water treatment plants. Lowering of the average As concentration to <1μg/L in the Netherlands is shown to result in an annual benefit of 7.2–14 M€. This study has a global significance for setting drinking water As limits and provision of safe drinking water.

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An increasing number of people want to reduce their environmental footprint by using harvested rainwater as a source for drinking water. Moreover, implementing rainwater harvesting (RWH) enables protection against damage caused by increasing precipitation frequency and intensity, which is predicted for Western Europe. In this study, literature data on rainwater quality were reviewed, and based on Dutch climatological data the usable quantity of rainwater in the Netherlands was calculated. For two specific cases, (1) a densely populated city district and (2) a single house in a rural area, the total costs of ownership (TCO) for decentralized drinking water supply from harvested rainwater was calculated, and a life cycle assessment (LCA) was made. For the single house it was found that costs were very high (€60-€110/m ³ ), and the environmental impact would not decrease. For the city district, costs would be comparable to the present costs of centralized drinking water production and supply, but the environmental benefit is negligible (≤1‰). Furthermore, it was found that the amount of rainwater that can be harvested in the city district only covers about 50% of the demand. It was concluded that the application of rainwater harvesting for drinking water production in the Netherlands is not economically feasible.

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Often rainwater harvesting is considered as an important contribution to a more sustainable society. Rainwater is assumed to be clean water, requiring only limited treatment, and it is thought that there is sufficient rainwater available to provide people with drinking water. In order to check these assumptions, we carried out a desk study into the quality and quantity of rainwater. It was found that rainwater is cleaner than surface water, but still may contain contaminants. Especially the microbiological quality of rainwater is a point of concern, and therefore treatment, including disinfection, will be required. Furthermore, it was found that for densely populated areas, like a city district in Amsterdam, the quantity of rainwater that can be harvested from both built and paved surfaces equals only about half the amount that is required for the inhabitants. If rainwater is collected and treated at a neighborhood level, the costs are in the same order of magnitude as for centralized drinking water treatment. However, at the level of a single house costs are significantly higher. As rainwater requires less treatment than e.g. surface water, a small decrease in environmental impact may be realized. @en