WATER TREATMENT WITH OZONE

The potable water consumption is an important way of transmission of denominated hydro diseases. That's why in Spain for example, there is an obligation to treat and to control water destined to human consumption.

For it, the chlorine is the most used agent disinfectant, but neither the only one nor the best one. The power disinfectant of ozone is 3.000 times higher and faster. The potable water treatment with ozone displays, therefore, a series of advantages respect to the treatment with chlorine.

Firstly, due to the high oxidation powerful of ozone, the quality of the disinfection is far beyond the one that is obtained with a treatment with chlorine. In this way, they are able to eliminate virus, bacteria and chlorine-resistant microorganisms in general. Thanks also to this high potential of oxidation ozone is able to precipitate heavy metals that can be in dissolution and to eliminate organic compounds, pesticides and all type of scents and strange flavours that the water could contain. Another important advantage in the use of ozone opposite to chlorine is the fastness with which it acts, which allows us to make very effective treatments in few seconds or minutes, when a treatment of disinfection with chlorine needs a higher time of contact.

THE MAIN EFFECTS OF OZONIZATION OF THE POTABLE WATER

1) Bacterial disinfection and viral inactivation.

2) Oxidation of inorganic compounds like iron, manganese, heavy metals, cyanides, sulphured and nitrates.

3) Oxidation of organic compounds like detergents, pesticides, herbicides, phenols, flavour and scent caused by impurities.

The action of ozone in each one of these cases is as it follows:

Disinfection and viral inactivation:

Bacteria and the viral inactivation are related to the concentration of ozone in the water and the time of contact with the microorganisms. The bacteria are those that more quickly are destroyed. The E-Coli bacteria are destroyed by concentrations of ozone of a little more than 0.1 mg/l and a time of contact of 15 seconds to 25 ºC or 30 ºC of temperature. Streptococcus tecalis is destroyed much more easily. To concentrations of ozone of 0.025 mg/l approx., it is obtained a 99.9% of inactivation in 20 seconds to both temperatures. The virus is more resistant than the bacteria. Pioneering researches by French scientists of Public Salubrity in the 60´s demonstrated that poliovirus types I, II and III are inactivated by means of concentrations of dissolved ozone to 0.4 mg/l in a time of contact of four minutes.

Oxidation of inorganic compounds:

In the case of iron, manganese and several arsenic compounds, the oxidation happens very quickly, leaving insoluble compounds that can be removed easily by means of an activated-carbon filter. Sulphides ions are oxidized to sulphates ions, an innocuous substance.

Oxidation of organic compounds:

Ozone is a very powerful agent in the treatment of organic materials. The organic compounds can be natural or synthetic. Some organic compounds react very quickly with ozone until the destruction in minutes or still seconds (like phenol, formic acid), while others more slowly react with ozone (like several pesticides, trichlorethane etc.). In some cases, the organic materials are oxidized only partially with ozone. A main advantage of partial oxidation in organic materials is that these ones are polarized much more than originally, so it produces insoluble complexes that can be removed with activated-carbon filters.

Elimination of turbidity:

The turbidity of the water is eliminated by ozone through a mixed of chemical oxidation and neutralization of load. The colloidal particles that cause turbidity are maintained in suspension by particles of negative load that are neutralized by ozone. Ozone, in addition, destroys the colloidal materials by means of the oxidation of organic matters.

Elimination of scents, colours and flavours:

The oxidation of the organic matter, heavy metals, sulphides and strange substances, produces the suppression of flavours and strange scents that the water could contain, providing an improvement in the quality and the aspect of the water and doing more adapted for its consumption and enjoys.

---

THE WATER TREATMENT WITH OZONE

The technique is based on getting an appropriate time of contact between the water and the suitable amount of ozone. A concentration between 0.5 and 0.8 mg/l of ozone during about three or four minutes is enough to obtain an exceptional and disinfected quality of water. After the treatment, ozone is disturbed in oxygen after several minutes, besides the fact it does not leave any type of residual, so there will not be any residual disinfectant that could prevent the bacteriological growth. In cases in which it is necessary to assure that the consumption water just has been dealt with ozone, the ozonization system will be making in a deposit with a recirculation flow, in where by means of a Venturi injector it will add the adapted ozone production. This amount of ozone and therefore, the residual ozone concentration in the deposit depends, firstly, on the characteristics of production of the equipment, and secondly, of the shutdown and operating time of itself. It can be said, with the use of the timer, it is possible to increase and to diminish the time of production and shutdown obtaining in stationary state greater or smaller ozone concentration. For more complex systems of regulation and control can settle in the water a sounding of residual ozone measurement that acts directly on the production of the equipment to reach the pre-established value of the ideal amount of ozone concentration in the water.

Based on the type of installation and the demand there can be other many possibilities as the direct injection of ozone in the pipe by means of by-pass or the installation of an ozone generator directly in the consumption faucet.

Really, a treatment with ozone allows us to enjoy an excellent water quality free of pathogenic microorganisms and all the problems that chlorine entails.