IE43616B1 - A method of removing ozone from wate - Google Patents

Abstract

1532227 Ozone removal PATERSON CANDY INTERNATIONAL Ltd 12 Aug 1976 [22 Oct 1975] 43368/75 Heading C1C Ozone is removed from water by passing the ozonized water through a filter media which comprises granulated coal or a granulated synthetic polymeric material. The coal is preferably anthracite. Magnesite, marble or chalk pellets from a pellet softener may be added to the filter.

Description

The present invention relates to a method of removing ozone from water, particularly but not exclusively swimming pool water.

Both chlorine and ozone are effective disinfection agents, and are widely used in the treatment of water supplies and in swimming pools. Residual chlorine is relatively stable, particularly when combined with ammonia to form chloramine, whereas ozone decomposes on its own accord in about an hour.

Chlorine is very soluble in water and its concentration in air in- contact with the water is too low at normal disinfection levels to cause any hazard. On the other hand, ozone is far less soluble and is particularly toxic in air.

In a water treatment plant this is of little consequence because the ozone-decays in the early part of the distribution system and never reaches the consumer. However, if these agents are used in a swimming pool the time delay between purification and the return to the pool is very short indeed. Thus it is necessary to remove all the ozone prior to returning the wat To maintain a residual sterilising action in the pool itself, it is desirable to maintain a residual level of chlorine, either free or combined, and if ozone is also used means are required for removing the ozone, preferably -243616 without destroying the chlorine.

In a large pool installation, chlorine is usually supplied ar. a gas and therefore over a period it is necessary to add an alkali to maintain an acceptable pH value.

It has been known for many years that granulated activated carbon effectively destroys ozone as well as free and combined chlorine. Granulated activated carbon has also been used as a filter media. Unfortunately because it destroys chlorine, bacteria are able to breed within the pores of the carbon, and although the carbon may absorb certain impurities it is not uncommon for the filtered water to contain more bacteria than the incoming w-ter. In this case post chlorination is necessary.

The invention provides a method of removing ozone 1$ from water comprising the step of passing the ozonized water through a filter medium which comprises granulated coal or a granulated synthetic polymeric material.

Preferably the granulated coal or the granulated synthetic polymeric material is in the form of non-porous particles so that the particles may be cleaned by back-washing the filters. Preferably, the pH of the water is maintained at a required value by a suitable additive.

If so desired a medium such as crushed magnesite, marble or chalk pellets from a pellet softener may be added to -33616 lhe i'il Ler.

By virtue of the high density of these materials they will fall to the bottom of the bed of anthracite, at which point the water will be clean and free from ozone.

Thus, hy way of example a purification system may include a sequence in which the raw water is passed down a packed column or a spray in a surrounding atmosphe>'e containing ozonized air. The ozonised water is then allowed to pass through a zone of sufficient volume to give the desired retention time for sterilisation or disinfection, and thence in through a filter media of sufficient size and depth both to remove suspended solids and to facilitate backwashing. 'x’his filter comprises anthracite, coal or a synthetic nonporous polymeric material. Finally, and optionally, the water would pass through a layer of pH correcting material and out through an underdrain system.

Any chlorine present in the incoming water would pass through unaffected.

The advantages of such a system over against granulated activated carbon or mixtures thereof with inert material are: (a) Avoidance of chlorine wastage and therefore lower operating costs. (b) Lower initial and replacement costs of the filter media. (c) Avoidance of bacterial contamination associated with activated carhon.

Claims (7)

1. A method of removing ozone from water comprising the step of passing the ozonized water through a niter medium which comprises granulated coal or a granulated synthetic polymeric material.

2. A method as claimed in claim 1 wherein the said coal is in the form of anthracite .

3. A method as claimed in claim 1 or claim 2, wherein the ganulated coal or the granulated synthetic polymeric material is in the form of non-porous particles so that the particles may be cleaned by back-washing the filter. I).. A method as claimed in claiin 2 or 3, wherein the pH of the water is maintained at a required value by a suitable additive.

4. 5. A method as claimed in claim 2, 3 or U> wherein magnesite, marble or chalk pellets from a pellet softener are added to the filter.

5. 6. A method for removing ozone from water according to any of claims 1 to 5 substantially as herein described with reference to the example given.

6.

7. Water in which the ozone has been removed by a method as claimed in any one of the preceding claims.