A lot of our research has been confirmed: Fresh water is imported from the mainland, distributed over the island and recollected in the sewage systems all leading to the treatment plant we visited. The treated water then is released to the system of ditches, leading to the sea. Unfortunately this is still containing a lot of rainwater which is being treated unnecessarily. We did not realize however, that one of the biggest challenges concerning the water system is the enormous fluctuation in the demand. Since Texel its population doubles over summer there is a huge peak in the daily water consumption in that period.
We found out that until 1988 Texel used to be self-sufficient in their drinking water. A desalination installation, using excess heat from an energy-plant to distill sea-water, produced the drinking water during the seventies and eighties but with production costs of 7 guilders per cubic meter it was not economically feasible. Though all other Wadden islands produce their own drinking water, Texel, the biggest one is completely dependent on the pipelines. This is because the other islands are covered by more dunes. Texel only has one source, the Mokslootvallei, which has a capacity of 0,54 million cubic meters a year, one third of the demand.
With the current methods it isn’t economically feasible to have a separate drinking water treatment facility on Texel. Dutch drinking water is extremely cheap, around 1,76 euros a cubic meter, so in order to deliver water at that price a very efficient way of water production has to be found. On top of that it should be able to process enormous peak amounts in summer, making the installation even more expensive. For comparison, on the island Seba, which uses desalination, a cubic meter of drinking water costs 45 euros!
We found that the Hoogheemraadschap, who manages the waste water cleaning facility and the ground water level on Texel, already does great work. They make excessive use of natural methods and incorporate the water they clean in the total ecosystem. The biggest flaw we found is the fact that they do not separately collect rainwater so this is cleaned unnecessarily. We also think that, by implementing changes on a building level, a lot of water consumption can be prevented.
Therefore our final proposal focuses mainly on the reduction and re-use of the limited amount of fresh water on Texel. We want to offer packages that enable the inhabitants to reduce their water use and inspire the community to use and collect the rainwater. We will start on a personal level; awareness will be created amongst the inhabitants to motivate them to reduce their water consumption. There will be a basic package which will enable the Tesselaars to make small adaptations to their house, it will cost 70 euros and lead to a reduction of 20%. The next step will be to improve the water system on a building level. The advanced package will provide a new or renovated house with the best (future) water saving systems like modern toilets and rainwater harvesting systems. The final improvements should be applied on an island level, rainwater should be collected separately so it can be used and to prevent the unnecessary cleaning of it.
Though our initial plan was to close the loop and recycle the fresh water available on the island, we experience that, with the current technologies, this will not be feasible. Since building a new big machine will be too expensive and probably won’t improve the sustainability of the island, our future goal will not be self-sufficiency. By declining the water use on the island, as an example for the rest of the Netherlands, the amount of water that needs to be processed can be decreased drastically. If the demand is declined, the future innovators of Texel should be able to come up with a solution in the near future to make the island independent of the pipeline after all.