Many people think it would be sustainable to make drinking water from collected rainwater. However, there is not enough rainwater in the Netherlands to meet demand. The costs are acceptable only on a larger scale, for example in an entire residential area. This project shows that rainwater collected as drinking water benefits the environment little, if at all, and that it may even have a negative effect.
Sustainability of rainwater as drinking water
Many people believe that rainwater can be collected as a sustainable source of drinking water. To investigate the extent to which this is the case, we looked at the options for water collection and treatment in both a densely populated urban area and in a detached house in an outlying area, including the costs and environmental impact.
Basic question and review
We started with the basic question: to what extent does the amount of precipitation that can be collected in our country meet local demand for drinking water? We then looked at which treatment technologies would be needed to make drinking water from rainwater, what this costs and what effects on the environment are to be expected.
No benefits for the time being
The results show that the amount of precipitation that can be collected in a densely populated area is enough to meet half of the local water requirement at most. The situation is different in the outlying area: with a lower population density – and therefore less water demand and often a larger roof area – it is possible to collect enough rainwater. However, the costs of individual water treatment are far too high for practical implementation. For an entire urban area, the costs correspond to those of centrally treated drinking water.
The determination of the environmental impact was based exclusively on ‘consumables’ – things such as chemicals and energy – but not installations or buildings. It was found that small-scale treatment has a larger environmental impact than centrally supplied water because the associated processes are less efficient. If the water is treated at the area level, there is a minor benefit but this is offset by the construction of local treatment plants and their environmental impact.