Water in intelligent settlements

Ike Señeres

IN theory, an intelligent settlement could be located either in the urban areas or in the rural areas. It goes without saying however that a settlement could not be considered as intelligent not unless it has a sustainable supply of water. In order for the sources of water to be sustainable, it has to be renewable and there is no way around that. Unlike electricity however that could be renewed with new supplies from non-fossil sources, the new supplies could come only either from rainwater or recycled water. By comparison, the availability of rainwater is not predictable, but the availability of recycled water is, and the latter could even be programmable. For sure, the sources of recycled water are unlimited, but what is limited is the awareness and appreciation in the first place that water is recyclable and should be recycled. One limiting factor to that is the thinking that there is always water when it is needed, and therefore it does not have to be recycled.

Other than recycled water, the other sources are sea water and sewerage water, even if the latter is a bit controversial when used for human consumption. There are unlimited supplies of sea water for conversion into fresh water by way of desalination, but the practicality of desalination is limited by electricity costs. In theory, the economics of desalination is based on how much the output per liter would cost to process. What that means is that the economics would not be good if the processing cost would be greater than its relative value. That is however subject to the prevailing conditions at the time that the relative value is computed. For example, in a drought, it does not matter how much the process would cost, for as long as there is potable water that could be made available.

Given the fact that the practicality of desalination is limited by electricity costs, it would appear that the key to sustainable desalination is the development of all sources of renewable energy. Although the analogy is not exact, it takes several liters of oil to produce some liters of desalinated water. The solution therefore is to shift to the use of renewable energy for desalination, because in effect, several liters of oil could be saved by producing some liters of desalinated water without using fossil based oils. It is very important for us to understand this equation, because if the economics of desalination could become better, there would be no more shortage of potable water in the future. Besides, if the economics of desalination would really become extremely good, it would no longer make any sense in recycling sewerage water.

Atmospheric Water Generators (AWGs) are devices that extract water from humid ambient air. Just like solar panels that are ideal for use in the Philippines because of abundant sunshine, AWGs are also ideal for use in the Philippines because of the high humidity here. The upside is that water could be produced as long as there is humidity, but the downside is that it needs electricity in order to run the AWGs therefore the water is not really free because of high energy costs. Just like the issue of desalination however, the economics would be good if the value of the outputs are greater than the value of the inputs. I think however that the way to get out of this dilemma is to use renewable energy sources such as solar. In theory, solar energy is free as soon as the costs of solar panels are fully depreciated. Therefore, free solar energy could give us free dehumidified water.

As of now, the desalination of sea water, the filtration of sewerage water and the condensation of the humid air into water may seem like far-fetched ideas because somehow, fresh water is still available in most places one way or the other. However, the challenge now is to already start considering other options as early as possible, long before the real water shortages would come. Perhaps as a less daring option, we could also build long distance water pipelines from the rural areas just like the oil pipelines. Push comes to shove; we could even solve the problem in much the same way that importation is now solving our problem of rice shortages. Remember however that even if we have rice to cook, we would still need water to cook it with.

To be on the practical side however, it is safer to have multiple sources of water, with as many sources as possible. While most of us people would only be able to solve one problem at a time, the people who work for us in the government agencies should be brighter than us, and should be able to solve several problems all at the same time, such as the problem of supplying water and energy to our human settlements in both the rural areas and the urban areas. One clue that I would give to them is that if they could supply affordable energy, they would also be able to supply sustainable water, because it would then be cheaper to desalinate, filter and dehumidify.

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