Raw sewage, industrial chemicals, bacteria, and viruses would all have to be removed to create the kind of oasis I am envisioning. The purification system would have to be cheap, easily replaceable, and unobtrusive. I am hoping to create a space where people can safely worship, clean their clothes, swim, bath, and maybe even brush their teeth. That last bit might be tricky do to the sheer amount of pollutants. Above I have mentioned “purification,” and it is important that the water is “purified” rather than “filtered.” The difference between the two lies in the size of pollutants which the apparatus can remove. Filtration removes bacteria, while purification removes viruses as well – which are even smaller (bacteria ar 0.1 micron, and viruses at .01). To give perspective, a micron is 1/1000 of a millimeter. Hollow fiber membranes filter out all materials larger than 0.02 microns. Hollow fiber membranes are highly durable, cheap and easily replaceable, but they do not purify the water – leaving behind dangerous viruses that spread water borne illness. To purify the water these membranes would have to be used with a purifier to create a concentric system. Adding another membrane on the outside to prevent bio-fouling, the buildup of organisms on the surface of the filter, might also be helpful.
The answer to this purification question, the main obstacle in realizing the design of my project may lie in a couple of places. The most promising so far are as follows: UV light, Titanium Dioxide, and water bottles. When I say water bottles I mean the self purifying water bottles which have pores at 0.015 microns – think of it as Lifestraw on steroids. UV light is often used to sterilize water, yet it tends to be expensive. Electricity, bulbs, insulation – UV is simply not feasible at this scale. Titanium Dioxide is a photo-catalyst, so it removes biological hazards and some heavy metals when exposed to UV radiation, in the future this technology may be used in conjunction with sunlight to purify water cheaply and effectively, but it is not yet fully developed or widely available. Returning to the simple solution of self purifying water bottles, Lifesaver Bottle, designed in response to the 2004 tsunami, filters out all viruses and bacteria. Markedly superior to hollow fiber membranes, this technology is one which I will be investigating in the development of the oasis. Yet there remains the question of chemicals, how will I remove dangerous industrial chemicals, such as chromium (released by tanneries of which there are many in India), which are toxic and unaffected by purification?