Up to 200 L rain water is collected on the rooftop below the solar panels. A sinter filter retains the rough materials such as leaves, seeds etc. A gravity driven ultra-filtration membrane cleans the water, by removing bacteria and potential pathogens (Fig. 2). More about the concept of gravity driven membrane filtration is described under the so called subfolder.
The storage of drinking water in a 165 L container provides sufficient capacity to cope with variations in water usage. A disadvantage of storing water is the regrowth of microorganisms such as bacteria. The membrane retains them to around 99.99%. To avoid recontamination due to regrowth of bacteria, a UV-lamp is located in the middle of the drinking water storage tank. In order to reduce energy consumption the UV lamp will be turned on intermittently. Tests will be conducted to see determine the optimum on/off interval.
Persons living in “self” will have to adapt their water consumption depending on the weather conditions and precast. As rainfall in our regions will not be enough to cover the complete water consumption, treated rain water is only used for drinking, cooking and brushing teeth. To cope with the higher water demand a grey water treatment and recycling of treated water is foreseen.
Under these conditions drinking water consumption for two persons is assumed to be at 18L per day. If the storage container and the roof storage are filled, drinking water will be available for approximately 20 days without rain.