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PARAMETROS DE CARACTERIZACIÓN DEL AGUA (II)
Index of Langelier
It is settled down for a certain temperature and it measures the state of balance of the water in relation to its incrustante or corrosive character. It is defined theoretically as:
where pH is the one to which is the water sample and pHs is the value of pH to which it would begin to precipitate Calcium Carbonate (CaCO 3 )
Due to it, when LSI has a negative value will be a water with corrosive tendency, as much greater as smaller is the LSI. However, for positive values of LSI the water will have an incrustante tendency which causes the calcium carbonate deposition.
For that reason it is important in industrial facilities and swimming pools to work with LSI next to 0 for optimal conditions of maintenance.
The value of LSI is calculated experimentally in the laboratory; however, an approach quite good can be done if we make the following formula:
Being, TDS =mg/l of dissolved solids;
T=the temperature in º C;
TH=the hardness expressed in mg/l of CaCO3 ; and
TAC=the alkalinity also in mg/l of CaCO3 .
Conductivity
The conductivity is a measurement of the capacity that the water has to lead the electrical current. The conductivity is related by a parameter called ionic force that is determined by the concentration and the load from each ion present in the water.
The values of conductivity are usually expressed in µS/cm (microsiemens by centimeter).
Nitrates
It is the specie derived from the most important nitrogen. They suppose an important source of nutrients for certain autotrophic organisms. A high nitrate concentration can originate the call eutrophization phenomenon, with an increase in the population of these autotrophic organisms that compete by oxygen with other aerobic organisms of greater size. The nitrate concentration, like the one of nitrites it is related to the later appearance of seaweed and for consumption it can cause metahemoglobinemia or the called disease of the blue baby.
Solids
We can distinguish: sedimentables solids, solids in suspension and dissolved solids, being the total solids the sum of all of them. These solids suppose the strange presence of bodies or substances that could not be very recommendable in some cases, besides the fact they increase the turbidity of the water and diminish the quality of the same one.
The sedimentables solids have a greater density than the water; they are dispersed due to drag forces or turbulences. When these forces and speeds stop and the water reaches a rest state, they precipitate at the bottom. They are usually eliminated easily by any method of filtration .
The solids in suspension stay in the water due to its colloidal nature. This is given by the small electrical charges that have these particles which make them have a certain affinity by water molecules. This type of solids are difficult to eliminate and it is necessary the addition of coagulating and flocculants agents to the water who modify the electrical charge of these particles, so they are grouped in floccules of greater size to be able to separate them by filtration. Certain systems of water treatment as ozonization already suppose a good floculante method because it oxidizes to the iron, manganese and aluminium. It is these oxides that truly have a floculante power in the water, so they increase the effectiveness of the filter and improve the transparency of the water.
The dissolved solids are related to the degree of mineralization of the water since they are ions of mineral salts dissolved by water. They are related to the conductivity of the water since an increase of these ions increases the conductive capacity. A treatment prolonged with composed of chlorine in a swimming pool for example increases the amount of dissolved solids and the conductivity in the time.
Turbidity
The turbidity is a parameter related to the transparency degree and cleaning of the water that depends on the amount of solids in suspension of the water which can simply be the result of a possible biological activity or a presence of no desirable components. It is measured by the absorption that a beam of light undergoes when cross a certain volume of water. In order to eliminate this turbidity and thus to improve the quality of the water are used the different types of filters which improve the yield with the use of flocculants.
