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We invite you to make a profound reflection about the perspective of the chaos according to the German philosopher Novalis: The water. Thankful for this little judgement exercise, four students of the civil and territorial engineering of the polytechnic university of Madrid take the slogan “Innovation makes the world better: Urban Sustainability” in the last stage of the competition Tsinghua-Santander World Challenges of the 21st Century Program, “the team will develop and discuss the idea on the campus of the Tsinghua university, against other six teams about this problem so current which the future generation have to say.

In the XVI century, the genious Leonardo da Vinci talked about the water like “water is de driving force of all nature: Movements, shifts, cycles, etc. These words were the words that made us to think ourselves if we are really driving to preserve the reserves of water. Sadly, the answer is a categorical no, and like four young potential engineers can´t change that the world population is gorwing exponentially, we must to take advantage of our sources.

“Back to the basics”: we must turn back to the idea of the self-sufficiency, look for the way of a self-supply.

Water like endless source is an utopian and old-fashionable way of thinking, because in the present, we can say that only the 2.5% of the mass of water is fresh water and the 0.97% it is suitable for the human use. This fact make us thinking about the unnecessary waste.

In this article, we will try to summarize our idea. Any comments or feedback will be greatly appreciated.

What is the problem or challenge our innovation is trying to address?

Under the 2030 Sustainable Development Goals of the United Nations, the number eleven makes reference to “Sustainable Cities and Communities”, we want to contribute to this goal by making sure that by this deadline, everyone has access to drinkable quality water.

The amount of pure water available in the world is very limited (less than 0.97% is suitable for human consumption) and we noticed that year by year there will be less and less due to climate change and contamination. We are trying to develop a system that, by collecting water from rainfall and recycling the water we use in our houses, is able to reduce the city water waste and derived expenses in the 50% of the water we consume on a regular basis. Correctly implemented, the system could also: help people from developing countries to gain access to pure water, prevent flooding and reduce contamination.

What is the solution we are offering?

To develop a smart water system based on the creation of a city network of smart buildings that are able to harvest rainwater from a green roof and the surrounding ground, and to process and reuse it following the idea of cyclical self-sufficiency.

In order to make this system work three are the needed steps:

Step 1. Water Gathering.

Trying to cover the maximum city surface, we will use a draining pavement and a garden roof to direct the water to an underneath water tank (the size of the tank will depend on raining estimation of each setting) used as the starting and finishing point of the water reutilization cycle.

We need to guarantee the water quality required by law, in order to do so, the harvested water will always go (when collected and after each reutilization) through a filtration and disinfection process (chlorination if coming from the pavement or the building, and UVGI if from the garden).

To move the water around the system the elements we need to have in place are the following ones:

First filtration. The filter is located on the roof, the garden and draining pavement. First, the rainwater goes through a correctly graded sand to prevent other particles from passing and damaging the filter located right after, which is needed to retain the smallest particles. This filter is able to treat the 55% of the total rainwater.

After the filtration the water can follow to possible paths:

Grey pipe: the water passes through a UV system (purple on the picture) to be disinfected by the removal of possible existing bacteria. Then, the water can either go to the underneath clean water tank or be used by the heating system; the path is determined by a distribution valve controlled from a smart technology app, that, when correctly programmed, is able to decide what are the water needs of the building.

Red pipe: the water that the filter has been unable to treat, or the one that comes directly from the draining pavement, is conducted to a smaller tank (previous to the clean water tank) that contains a filtering system, similar to the previous one used on the roof. After going through this filter, the water is directly conducted to the main tank.

Clean water tank: collects the water from the red and grey pipes and applies a chlorination process (the needed concentration has to exceed the break-point) to disinfect the water (this process is the equivalent to the UV of the grey pipe), so it is ready to be used as greywater.

Green pipe: under the demand of the neighbors the clean water is pumped to the different floors to be used on the toilet and household appliances as washing machines. This pipe also collects the water that, after being used in one floor, could be used in the ones below it as grey water; if necessary, the system has the same valves that were used in the grey pipe after the first filter (grey pipe), so if the water harvest on one floor is not needed the valve turns to allow the water to go back to the clean water tank.

The water used in the toilet that cannot be used again, goes directly to the sanitary collector, all the rest of the water is sent back to the deposit and the cycle starts again.

Step 3. Creating the Smart System.

For this project we will be using Internet of Things (IoT Sensorica) to make the hydraulic system controllable from a coded program (coded in Python using a Raspberry pi zero).

We will train the system to gain the capacity to understand the demand of the different households and circulate the water according to it. Also, we will be constantly measuring the water level at the underneath tank, so, in the case one has extra water, and the ones of the buildings around it are in need of water, the system could transfer the water from one to the others; which we would allow us to increase this building self-sufficiency to a neighbourhood level, and eventually, with the system completely trained, to a whole city level.

Feasibility Study.

The first thing that worried us is the climatic dependence our project has. After a deeper study, we were able to estimate that the yearly precipitation we will need in order for this project to be rentable will be 400 ml per year, and this happens in the 80% of the countries in the world.

The principal investors would be the governments with the support of the United Nations to take this problem in a world vision. In a reduce mode, the government of each country could support with grants those people who collaborate building according at this project. Other advantage to consider is that the sanitary system in a lot of cities of developing countries are insufficient so with this change could make aware the population about sustainability.

Is important to take account of the reduction of waste of water that it means if the impluyium system is integrated in the city.

Using the example of Madrid and according to the statistics of the city council, the houses consume 144.120.536 m3/year. The cost/m3 is 1.83€, that is equivalent to 2 USD / m3. It is supposed that the 50% of this water is used to meet the demand of grey waters, that it supposes 72.060.268 m3 annually, translated to money equivalent is a saving of 144.120.536USD/m3

The implementation costs of the system inside the building is about 13.679 USD, according to the city council, in Madrid there are 129.085 buildings, so the total cost will be 1.765.753.715 USD. With other sources of bakings, the period of return will be 12 years and 3 months. That we consider is really low if we see the benefits of this spends.


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