3. Design of the future sustainable socio-technical sub-system in more detail

In this chapter we will introduce and evaluate possible water saving technologies. We will choose the best technologies for our future system which will be combined in the plan visualized in part 4.

3.1 Water reduction:

Since Dutch water is relatively cheap saving water won’t lead to enormous savings on the financial field. However, cleaning water consumes lots of energy, the chemicals used end up in the ecosystem and ground water levels are disturbed, so it is important to pay attention to your water usage.

The Dutch average daily water usage is 120 liters per person, washing, cleaning and flushing the toilet consumes the biggest part of this water:

Daily water use

3.1.1 Awareness

By creating awareness among the Tesselaars they can start reducing their water use immediately. Info graphics or informative meetings should provide the inhabitants and tourists with tips in order to save drinking water. Small changes on a large scale can have big impacts:

  • Since taps run with approximately 12 L/min, don't forget to close it in between actions. Closing the tap while you brush your teeth, for one minute, twice a day, will save 20% of your water usage!
  • Leaking taps can consume enormous amounts of water; by checking all taps in your house you can prevent unnecessary waste of water. A dripping tap often wastes around 5 liters a day, a leaking toilet sometimes even 300 liters a day.
  • Showering 1 minute less, assuming you shower on a daily basis, will reduce your water use by more than 7%.
  • A bath consumes twice as much water (110 L) compared to a five minute shower.
  • Fill up the (dish)washing machine in order to use it as efficiently as possible. An average dishwasher uses 22,5 liters each turn, a clothes washing machine even 150 L. Assuming that by filling your machine you can prevent one wash a month and one dish a week you'll save 240L of water in a month, 8L of water per day, so another 7%.


3.1.2 Technological changes

To enhance the water savings that you can incorporate several, small, technical devices. For instance:

  • water saving shower heads consume 5 L/min instead of 8,7 without a reduction in comfort
  • water saving tap heads can save up to 3000 L/year and cost only 2 euros
  • heat exchangers can be applied to make use of the waste heat after a shower
  • modern (dish)washing machines are often much less energy and water consuming
  • the same goes for modern toilets, you can also use something to partly "fill" the reservoir of an old toilet
  • Grey or rainwater systems can replace lots of the clean water; this toilet (figure) saves 25% clean water by using the sink water to flush.
  • Rain water tanks are a great step towards water saving, without any extra work the water is perfectly suitable for irrigation and cleaning in and around the house. With tanks up to 2000 liters there can always be water available. If this water is used for outside purposes 7000 liters of drinking water can be saved annually.

grey water toilet


3.2 Precipitation systems

As we've seen Texel deals with large amounts of atmospheric precipitation. Collecting and using this fresh water can reduce tap water use to a large extend. The systems filter the water and collect it in a bag or tank underground or underneath the house. The reservoir can be connected to the toilets, washing machine and all other taps which aren't used for drinking water. The systems are not only friendly for the environment; a good system saves 50 euros on water using only 3 euros of energy.

precipation system

The roof of an average Dutch house catches 80.000 liters of rainwater on a yearly basis, this is nearly enough for an average two person household. Rainwater harvesting is beneficial because provides an independent water supply during regional water restrictions by reducing the existing water supply and simultaneously providing water during the whole year, especially in drought seasons by reducing the run-off, the erosion and the contamination of surface water.

The main components of a rain harvesting system are a catchment surface, which can be also the roofs of the existing buildings or a new catchment surface, the conveyance system (pipes), the storage area, which ranges in sizes according the catchment surface and can be under or on the ground and the treatment system (filters, pump).

3.2.1 Drinking water from rain water

Can rainwater be made safe to drink? Yes. How safe? As safe as your well or tap water. How do you make it safe for indoor use? By filtering and purifying it. As a result, it can also use as potable water, as rainwater is substantially free of salinity and other salts. Bringing rain indoors could save the expense and environmental costs of treating and transporting water.  

Contaminants in water may include algae, air pollution, bird excrement, and leaves, sand, and dust. Local wells have dealt with these problems for decades. Installation of filtration and purification equipment can remove these contaminants at home as well.

It is important to take measures and keep foreign matter out of the incoming rainwater. First flush devices, gutter screens and other screening mechanisms keep the rainwater as clean as possible before it enters the conveyance system. Using screens and filters will greatly reduce maintenance and lengthen the life of the pump and filtration/purification system. To keep sediment where it belongs, at the bottom of your tank, screen incoming rainwater, give the remaining sediment time to settle, avoid disturbing it, and don’t pull water from the bottom of the tank. Use a floating filter, which extracts water from the middle of the tank, leaving sediment undisturbed. Next is filtration, which removes debris from the water. Disinfection or purification follows, which kills contaminants and removes harmful substances that may be present. Filtration is included in every system, even simple irrigation systems. Examples of filtration systems include: screen filters, paper filters, and carbon or charcoal filters.

3.3 filter technologies

3.3.1 Natural filter technologies: The helofytenfilter

There are several natural ways to clean water, these are not only environmentally friendly, they are also relatively cheap and reliable since they don't depend on technologies.

In a helofytenfilter swamp plants are used in order to clean waste water. After solid particles are removed in a septic tank, the water can be pumped into the filter. This filter consists of a one meter thick layer of sand with a layer of small stones above and underneath it (see picture). The roots of the plants have grown through the sand and as the water gradually sinks down some air is dragged into the ground as well. This creates optimal surroundings for water cleaning bacteria which live in symbiosis with the helophytes; those bacteria clean the water up to 99%!


Since the pump only has to work during short time intervals, gravity will do the rest of the work, energy consumption of such filters is really low. Since all waste materials are being demolished by the bacteria, which can provide as food for other organisms, there is hardly any residue.

3.3.2 Desalination towards sustainable ways - turning seawater into drinking water

Global demand for water continues to increase due to population growth and economic development, whilst freshwater sources are becoming scarcer due to increasing demand for natural resources and the impacts of climate change. Desalination of seawater and brackish water can be used to augment the increasing demand for fresh water supplies.

It is referred to the removal of salts and minerals in order to produce water suitable for human consumption or irrigation. Due to relatively high-energy consumption (often using energy supply from fossil fuel sources which are vulnerable to volatile global market prices as well as logistical supply problems in remote and island communities and are therefore not sustainable), the costs of desalinating seawater are generally higher than other alternatives (like river water, rain water or water recycle), but alternatives are not always available. Moreover, the large amounts of energy have also an outsized impact on the environment. Simultaneously, desalination systems can damage the aquatic ecosystems by releasing large volumes of highly salty liquid brine back into the water.


Engineers and entrepreneurs across the globe are now trying to devise greener and more sustainable ways for desalination. Some are inventing new alternatives. Technologies that shrink energy and brine or they are chemical-free or even energy-efficient enough to run on renewable energy sources.

Current information on desalination shows that only 1% of total desalinated water is based on energy from renewable sources. Renewables are becoming increasingly mainstream and technology prices continue to decline, thus making renewable energy a viable option. While desalination is still costly, declining renewable energy technology deployment costs are expected to bring this cost down in the coming years. This is of particular interest to remote regions and islands with small populations and poor infrastructure for freshwater and electricity transmission and distribution.

There are two broad categories of desalination technologies. Thermal desalination uses heat to vaporize fresh water, while membrane desalination (reverse osmosis) uses high pressure from electrically powered pumps to separate fresh water from seawater or brackish water using a membrane.

Thermal Desalination Technologies: Thermal desalination involves distillation processes where saline feed-water is heated to vaporize, causing fresh water to evaporate and leave behind a highly saline solution, namely the brine. Freshwater is then obtained from vapor cooling and condensation.

Membrane Desalination Technologies: Membrane desalination uses membranes to separate fresh water from saline feed-water. Feed-water is brought to the surface of a membrane, which selectively passes water and excludes salts.

Desalination based on Renewable Energy: Desalination based on the use of renewable energy sources can provide a sustainable way to produce fresh water. It is expected to become economically attractive as the costs of renewable technologies continue to decline and the prices of fossil fuels continue to increase. Using locally available renewable energy resources for desalination like rain, tides, waves, which are also related to our water cycle sub-system is likely to be a cost-effective solution particularly in remote regions, with low population density and poor infrastructure for fresh water and electricity transmission and distribution. As a result, the solution is to find a sustainable solution to produce renewable energy and afterwards to use it in order to desalinate seawater. The placement of a large scale desalination plant in the middle of the sea has distinct advantages over land based desalination - only at sea can we gather a plurality of renewable energy sources - like solar, wind, tide, current, OTEC [ocean thermal energy conversion].

The dominant energy source is solar photovoltaic (PV), which is used in some 43% of the existing applications, followed by solar thermal and wind energy. The right combination of a renewable energy source with a desalination technology can be the key to match both power and water demand economically, efficiently and in an environmentally friendly way.

wave energy

An example: Carnegie Wave Energy is planning to open the world’s first zero-emission wave powered desalination plant on Garden Island in Australia. Using the Perth Company’s proprietary “CETO technology,” the two-megawatt pilot project will operate with multiple submerged buoys tethered to pumps that funnel pressurized water to turbines onshore. There the water can either be harnessed to create electricity or to run and supply water for a reverse osmosis desalination plant. The CETO wave power converters are the first to be fully submerged under water, keeping them safe from the effects of major storms and reducing visual impact. The project on Garden Island in Western Australia will be a grid-connected, commercial scale operation that will demonstrate the technology’s viability, record its interactions with the environment, and help provide fresh water in accordance with the West Australia Water Corporation. Desalination is an important part of Perth’s long-term strategy to maintain a supply of clean drinking water and the Carnegie Wave Energy technology will secure a means to provide this precious resource without relying upon energy-hungry machinery. Instead, by creating its own power, the CETO infrastructure can cut down on greenhouse gas emissions while also generating electrons and purified water. The project is expected to begin construction in 2014.

3.3.2 Produce drinking water from air humidity

Even though there is a shortage of surface or groundwater, in often-considerable quantities, water is to be found in the air. Moreover, as a result of global warming it is to be expected that the water content of the atmosphere will increase further because of the rising temperatures. So that this water resource can be developed as a source of drinking water. The entire process consists of two parts. First, the humidity from the air is absorbed by a highly concentrated saline solution (brine) and thus bound. Then this diluted saline solution is distilled and the water separated from the saline solution is condensed as drinking water (desorption).

Some example are the Skywater® machine and the atmospheric water generator (AWG), which we will explain below.

The Skywater® is a machine, which makes drinking water from humidity in the air. It is alleviate dependence from the local water supply, by harvesting enough fresh water from the air to supply a single-family home, office, and much more. The Skywater® 14 home / office machine may be the most convenient kitchen appliance since the refrigerator. No more lifting heavy water bottles for your water cooler, simply plug in Skywater® products and enjoy fresh, great tasting water for pennies to the liter.


The second example is the atmospheric water generator (AWG), which is a device that extracts water from humid ambient air. Water vapor in the air is condensed by cooling the air below its dew point, exposing the air to desiccants, or pressurizing the air. Unlike a dehumidifier, an AWG is designed to render the water potable. AWGs are useful where pure drinking water is difficult or impossible to obtain, because there is almost always a small amount of water in the air that can be extracted. The two primary techniques in use are cooling and desiccants. The extraction of atmospheric water may not be completely free of cost, because significant input of energy is required to drive some AWG processes, sometimes called "trading oil for water". Research has also developed AWG technologies to produce useful yields of water at a reduced (but non-zero) energy cost.

3.4 solutions for Texel

3.4.1 Awareness plan - reduce

In addition to the list mentioned above, there are much more small changes in and around the house which can have significant effect on your water usage. In order to involve the Tesselaars to their new sustainable future we start by raising their awareness and responsibility. The campaign should teach them that just by reducing their showers by one minute, closing the tap while brushing their teeth and filling up their washing machines in order to reduce their amount of washes, they can already reduce their water use by 25%. In addition they should feel responsible for their independency of the mainland: by saving 25% water, the pipeline might become unnecessary in the future.

A special function lays with the owners of hotels and other tourist accommodations; they will not only be responsible for their own water use but must also inspire their guests to do so. This should be done in a similar way to the cards we're already familiar with in hotels that tell you to re-use your towel.

3.4.2 Building level plan - reduce

When interest has grown among the inhabitants they should be motivated to contribute to their water saving plan more actively. Several packages must be available in order to turn your house or tourist accommodation into a water friendly one. The packages should be available in different gradations: from low-cost ones including saving water taps, shower heads and a rain water tank for outside use, up to the ultimate package where, especially new projects, incorporate grey water systems combined with precipitation collection.

These technological changes will not only reduce the drink-water usage by another 25%, it will also provide Texel with a unique selling point. Since the island is ahead of the mainland, by stimulating local companies to contribute to the distribution of sustainable solutions, the local economy will be stimulated by "exporting" Texel its sustainable expertise. This will also attract eco-tourism, stimulating the wish for tourists to contribute to the plan as well.

3.4.3 Rain water usage - reuse

Due to the recent floods and draughts there is need for an extra buffer on the short term. By incorporating these buffers, which will mainly be precipitation tanks, to grey water points, like swimming pools, showers and washing machines on camp sides, less drinking water will be spoiled by tourists. Gradually, as the technological changes will be incorporated in more and more buildings, the buffers, of different sizes, will become more effective.

3.4.4 Drinking water cleaning - recycling

The last step to provide independency for the Tesselaars is to create their own drinking water cleaning facility. Since there is no ground water source on Texel and desalination and using air humidity is still very energy consuming, recycling water is preferred. However, there are still no good, legal methods for this, making it a future goal.

Rosanne , Elia Galiouna

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