In Mexico, I noticed that there was some salt in the tap water. Why is it so unfeasible to remove the salt?

Question

Why is there such as salinization problem in the world in general? Where I live, when water goes into ther sewer system, I suppose the impurities are removed before returning the water back to the rivers and so forth. Why can't the same technology be used to remove salt from the water?

Answer 1

Its cheaper in general and water companies can make more money that way if you need to buy fresh bottled water as well as pay for tap water.

Answer 2

Chances are, this isn't because of a lack of will from the water companies to use desalinisation instead of standard water treatment, but it might be a case of over-extraction of the groundwater (water stored underground naturally in rocks).

Over the years, demand for water in Mexico's increased a lot, and this leads to extracting more water. As a result, something known as salt water incursion occurs, where saltwater stored in the ground close to coasts leeches into freshwater supplies further inland, contaminating the supply.

As for the unfeasability of desalinisation? It costs a lot more money to treat water that way, and only very rich countries such as the United Arab Emirates rely wholly upon desalinisation. However, they have no ground, freshwater supply, so that makes them lean towards desalinisation.

And about using the same technology to remove the salt? I'm not so sure, but perhaps the water treatment facility in question is unable to remove salt from the water (it probably requires a different process)... either that or the water management company do not know of the salt content yet.
It could also somehow be leaking into the water pipes... I guess that may be another possibility.

Answer 3

For now the removal of salt from water is done by various methods, most of which and slow and expensive. Desalinization can and is being done by evaporation and condensation, but not on a very large scale, I have read that Israel has been a pioneer in this field for the water to be used for irrigation. There has also been some progress in plant use for the transformation by the Disney Corp. in Fla. If someone could come up with a sure fire cheap way to remove the salts from the oceans waters,he would be hailed as a hero. To think that the worlds deserts could be irrigated to change the barren land to fruitful land would be a God sent.

Answer 4

Waste water treatment in US/UK is primarily for organic matter and particulates. Salts are ions. The easiest way to remove salt is actually to remove the water. Water is evaporated leaving the salt behind. Imagine how much energy it would take to boil and condense the water for one Americans shower. It takes a massive amount of energy to desalinate water- this is why only rich countries do it. There is also a huge potential pollution cost as the energy must come from somewhere.
Much of Mexico is arid and the water comes from wells. Shallow well water may contain salts, especially in deserts or in areas and along a coast where too much ground water is being removed. Ocean water and salts are pulled in to replace the extracted fresh water. My guess is that many Mexican communities, particularly in tourist areas, have had their small scale water supplies compromised by tourism and the cruise ship industry's growing demand for water. Also, large scale irrigation of desert land (which is a fairly recent development) leaches salts from the soil into the groundwater.
Clean water is going to be a global civil rights issue in the coming decades and will likely be the cause of many conflicts between nations. Several US states are currently suing each other of freshwater resources. Its getting rarer and rarer.

Answer 5

There is different technology to deal with different problems. Sewerage works in general deal with organic material in water. There is technology to remove salts from water (used in various places around the world - flash evaporation, reverse osmosis, ion exchange) and the equipment and running costs may be substantially reduced if the levels of salts to be removed are low. It may be that the Mexicans just can't afford water treated in this way or don't place priority on it.

Edited comment: For some info on reverse osmosis see http://www.zenon.com/products/packaged_systems/RO/ZenoRO/

Answer 6

US water comes from lakes and rivers (fresh water) not the ocean (salt water). Removing salt is more costly than filtering out germs and stuff, and Mexico is very broke because it suffers so much from corruption. It also has few resources.