Magnesium is found in seawater (about 1300 p pm) and oceans (after the sodium) in big quantity. Rivers contains approximately 4 p pm of magnesium. Magnesium and other alkali earth metals are responsible for water hardness. Water which contain large amounts of alkali earth ions we called hard water, the water contain low amounts of these ions we called soft water. For example Dutch water contains between 1 and 5 mg of magnesium per liter.
Magnesium in the water we see in form like: Mg (s) + 2H2O(g) -> Mg(OH)2(aq) + H2(g).
Magnesium generally is a slow-reacting element, but reactivity increases with oxygen levels. Furthermore, magnesium reacts with water vapor to magnesium hydroxide and hydrogen gas like this above. Interesting fact is that magnesium fires cannot be extinguished by water. Magnesium reacts with nitrogen from air to form magnesium nitride (Mg3N2). When attempts are made to extinguish magnesium fires with water, magnesium aggressively reacts with hydrogen gas. We can stop any damage when we covered the magnesium with sand.
An example of a magnesium compound is magnesium phosphide (Mg3P2). When the compound comes in contact with water or moist air, it is decomposed and phosphine (PH3) is formed. This is a toxic compound, and it is also very flammable in air.
Solubility of magnesium and magnesium compounds we see mainly as Mg2+(aq) in watery solutions but also as MgOH+(aq) and Mg(OH)2(aq). Water solubility of magnesium hydroxide is 12 mg/L. Other magnesium compounds are clearly more water soluble, for example magnesium carbonate (600 mg/L). Magnesium sulphate adds a bitter flavour to water, and has a water solubility of 309 g/L at 10oC.
Magnesium is present in water because it is washed from rocks and subsequently ends up in water. Magnesium has many different purposes and can get into the water in different ways.
Chemical industries add magnesium to plastics and other materials. Its fire protection is substantial for many products. It also ends up in the environment from fertilizer application and from cattle feed. Magnesium sulphate is applied in beer breweries, too. And magnesium hydroxide is applied in wastewater treatment plants.
During the World War 2 magnesium was applied in fire bombs because it can't be extinguish by the water and can cause big damage. The development of these bombs introduced a method to extract magnesium from seawater.
All magnesium extraction processes require installations for cleaning off-gases and treating wastewater. Important comes of solid waste are deposited as landfill. All processes include minerals from calcination of carbonaceous to dehydration of hydroxides but all they are clean by conventional methods. The dust is removed. Gases emitted to the atmosphere contain carbon dioxide, sulfur dioxide, and nitrogen oxides. Of course the content of these gases are lowered by scrubbing with seawater and the local emission regulations is preserved. In electrolytic processes, carbon is used as a reduction in the preparation of anhydrous magnesium chloride and as anode material in electrolysis. Although such compounds only occur in liquid effluents from scrubber systems at low concentrations (that means a few micrograms per liter), collection and destruction are compulsory.
Small particles in the liquid effluents for the chlorinated organic compounds are necessary.
Particles may be flocculated with appropriate cationic or nonionic agents. They can be removed by nitration or centrifugation because liquids are treated with activated carbon. Traces of chlorine or hydrochloric acid in off-gases are scrubbed, recycled, or neutralized by conventional methods. We use for industrial purposes by-products from metallothermic processes. Sediment from casting operations contains entrapped metallic magnesium globules. People extremely carefully control hydrogen emission from the reaction of entrapped magnesium, with water. Off-gases from foundry operations containing different minerals and magnesium oxide are scrubbed by conventional methods to comply with local regulations.
Environmental effects of magnesium in the water are important, too. Magnesium is a dietary mineral for any organism but insects. It is a central atom of the chlorophyll molecule, that is the reason why it is so requirement for plant photosynthesis. Magnesium is found in seawater, rivers and rain water. So, we can say that magnesium is naturally part of our world and environment. Tendency for magnesium content in drinking water are unlikely, because negative human and animal health effects are not expected. Environmental problems indirectly caused by magnesium in water are caused by applying softeners. The hardness is partially caused by magnesium.
Some of magnesium ions negatively influence cleansing power of detergents, because these form nearly insoluble salts with soap. Today, alternative chemicals are applied, mainly complexing agents such as sodium citrate, EDTA (ethylenediaminetetraacetic acid) and NTA (Nitriloacetic acid), or ion exchanges such as zeolite A. These substances do not cause eutrophication and are not toxic.
Mobile heavy metals may end up in water ways, because EDTA is difficult to remove in wastewater purification plants. Contrary to calcium, magnesium is not bound to zeolites under washing conditions. Zeolite A increases the amount of lees. About ethylenediaminetetraacetic acid (EDTA) have the audacity to remove metals from compounds that are otherwise difficult to decompose.
Adding softeners to detergents is unnecessary for regions that only contain soft water. The different water in different regions show is it necessary to add magnesium or not.
A possible solution to this problem is dosing different compounds in detergents yourself.
Health effect of magnesium in the water is well-known and applied in our life. Magnesium is a dietary mineral for humans, one of the micro elements that are responsible for membrane function, nerve stimulant transmission, muscle contraction, also protein construction and DNA replication. It is an ingredient of many enzymes in our body. Magnesium and calcium often perform the same functions within the human body and are generally antagonistic. Here we can say that there aren't cases of magnesium poisoning. By large doses magnesium people can get muscle slackening, nerve problems, depressions and personality changes vomiting and diarrhoea.
It is unusual to introduce legal limits for magnesium in drinking water, because there is no scientific information of magnesium toxicity. If the water has many magnesium components and they make the water hardness we can remove them. In that way, by purification technologies we make the water soft and good for us.