Aluminium

Aluminum in water

What is aluminum?

It is a silver colored element, very light and easy to handle, as well as being very resistant to corrosion, low in toxicity and a good thermal conductor. Its symbol is Al, it has an atomic weight of 26.98 g / mol, it is number 13 in the periodic table and it is part of the group IIIA. It is the most abundant metal on the planet, naturally found in combination with oxides and silicates.

Aluminum is alloyed with small amounts of copper, magnesium, silicon, manganese and other elements to improve its strength and utility, mainly in the production of building materials. This element is widely used in the manufacture of products, as well as, as the structure of the equipment that performs operations in some industrial process. Some examples of use are: doors, windows, food containers, kitchen utensils, locks among others (1); and equipment such as tanks, distillation towers, ovens, mills, boilers, etc.

Aluminum has the curious characteristic of always remaining oxidized, this because it is highly reactive with oxygen. On its surface, a micro layer is formed, made of aluminum oxide (alumina, Al2O3), it is silvery in colour (therefore, oxidation is not noticed as with iron or copper), and it provides properties that make it resistant to corrosion and different chemicals (except strong acids and bases). Usually, an anodizing process is implemented to make it even more resistant, which is why aluminum is widely used in equipment manufacturing materials, tools, electronic devices, etc.

Does aluminum cause health effects?

This element is considered to be non-toxic, since Mexican standards consider a permissible limit of aluminum up to 20 mg / L in drinking water (2). There is not enough information about whether aluminum significantly affects human health, because although the human body is always exposed to this element due to its abundance in the environment, there is no relationship with harmful health effects.

Aluminum can be found in very low quantities in the water we drink and in food, but there is no scope for the metal to affect our organism. When aluminum is considered a health risk, it is when you have a high exposure to it.

Large amounts of aluminum administered orally can cause irritation of the gastrointestinal tract and lead to other health problems as a result of high intake of aluminum-containing medications as part of the formulation.

Another case is, of people who may be exposed to aluminum powder (e.g. in industrial processes), and may have severe problems in the respiratory system. The health problems caused by aluminum are then due to excessive contact, either by ingestion (mainly aluminum-containing drugs) or by high exposure to it.

Studies have been conducted on a possible relationship between aluminum and Alzheimer's disease, however, there are other studies that contradict this, reporting that there is not enough evidence to confirm this relationship (3).

How is aluminum present in water?

First you must understand how aluminum behaves in water. In water treatment plants, it is common to use aluminum sulphate salts as a coagulant for better filtration. These salts are inexpensive and widely used. Aluminum is not only applied in water treatment plants, it is also found in a wide field of application, such as the steel, food, pharmaceutical, cosmetic industry, etc.

What are the methods for removing aluminum from water?

The ion exchange and demineralization are some potential methods for removing aluminum from water. In treatment plants (as mentioned above), aluminum sulfate is usually added to the water during the coagulation process, which means that there are higher concentrations of the element in the treated water than in the raw water. When aluminum levels are above 0.1 mg / L in distribution systems, discoloration may result. This discoloration is also an indication of liquid treatment problems (lack of pH control, poor coagulation, and breaks in filtration) (4).

 Reverse osmosis RO is also a method for removing aluminum from water when aluminum values are below 0.05 mg / l. This method has become much more competitive because of the cost of operation.

Sources

  1. Equipo Editorial. Aluminio ¿Para qué sirve el elementro químico Al? IQuímicas. [En línea] 2018. [Citado el: 16 de Enero de 2020.] https://iquimicas.com/aluminio-sirve-elemento-quimico-al/.
  2. MODIFICACIÓN A LA NORMA OFICIAL MEXICANA NOM-127-SSA1-1994, SALUD AMBIENTAL. AGUA PARA USO Y CONSUMO HUMANO. LIMITES PERMISIBLES DE CALIDAD Y TRATAMIENTOS A QUE DEBE SOMETERSE EL AGUA PARA SU POTABILIZACIÓN. Diario Oficial de la Federación, Comité Consultivo Nacional de Normalización de Regulación y Fomento Sanitario. 2000.
  3. REVISIÓN DE LOS ESTUDIOS SOBRE EXPOSICIÓN AL ALUMINIO Y ENFERMEDAD DE ALZHEIMER. Suay, Loreto y Ballester, Ferran. 6, Valencia : Revista Española de Salud Pública, 2002, Vol. 76. 1135-5727.
  4. DeZuane, John. Handbook of Drinking Water Quality. Canadá : John Wiley & Sons, Inc., 1997. 0-471-28789-X.

Last updated 14/02/2020.