Ozone applications: Swimming pool water

Water quality can be improved eminently and costs can be saved on the long term when ozone is applied for swimming pool water treatment.

These are the main benefits of ozonisation:

- Substantial decrease in chlorine use
- Improval of the filter and coagulant capacities.
- A reduction of coagulant use and less backwashing of the filter is required
- Water use can be decreased, because of an increase in water quality
- Ozone oxidizes organic and inorganic matter in the water
- No unwanted byproducts - such as chloramines (which cause a chlorine-smell)
- Chlorine scents can be fully diminished by ozone application

- Ozone is a more powerful oxidant and disinfectant than chlorine. Certain chlorine-resistant pathogens (see ozone disinfection: resistant microorganisms) cannot multiply in water that is treated with ozone

Because of its strong oxidation and disinfection mechanism, ozone is very suitable for swimming pool water treatment.

Swimming pool water pollutants:

Swimming pool water pollution is mainly caused by swimmers. This makes it a very dynamic pollution, which is dependent on the number and types of swimmers. Swimming pool pollutants can be divided up into three groups: microorganisms, undissolved pollutants and dissolved pollutants.

Each swimmer carries a large number of microorganisms, such as bacteria, fungi and viruses. Many of these microorganisms may be pathogenic and can cause disease.

Undissolved pollutants mainly consist of visible floating particles, such as hairs and skin flakes, but also of colloidal particles, such as skin tissues and soap remains.

Dissolved pollutants can consist of urine, sweat, eye fluids and saliva. Sweat and urine contain water, but also ammonia, ureum, kreatine, kreatinine and amino acids. When these substances are dissolved in water, they cannot harm swimmers.

However, when these compounds react with chlorine in swimming pool water, incomplete oxidation can cause chloramine formation. This causes the so-called chlorine-scent, which irritates the eyes and respiratory system. In a number of cases, stable compounds can be formed, which can only be removed from swimming pool water by water refresment [13,14].

Because of its strong oxidation and disinfection mechanism, ozone is very suitable for swimming pool water treatment.

Increased efficiency of the filter

By treating water with ozone, the biodegradation rate of natural organic matter (NOM) is increased. This means, that large molecules are diminished to smaller molecules, which can be decomposed by a filter more easily. The organic matter will cause an increase in bacterial growth in the system, because it is a bacterial nutrient. Regrowth of bacteria in a distribution system is an unwanted effect. This can be turned into a positive effect by injecting ozone on a sand filter. Research has shown that preozonization can increase filter efficiency. Ozone increases biodegradability of materials and microbial growth, but it also increases the oxygen concentration in the filter. Total Organic Carbon (TOC) removal can be increased to 35% in a sand filter when ozone is added [33].
The amount of organic matter in the filter is decreased, causing regrowth of bacteria in the system to be reduced. Figure 2 shows the distiction between algae removal in a sand filter with ozone application and without ozone application.

Increasing coagulant efficiency

In a filter, a coagulant is usually added to prevent clogging and increase filter capacity. An extra benefit of ozone addition to filter systems is that coagulant activity is increased. Ozone itself can also act as a coagulant. Research has shown that preozonization can increase the adsorption of organic matter to coagulants, such as: activated aluminum [35], aluminum hydroxide [36], aluminum polychloride [34] and calcium carbonate [35]. A possible explanation for this is that the organic matter becomes more polar by ozonization. Figure 3 illustrates the effect of various ozone concentrations on turbidity removal by coagulants, such as aluminum polychloride.

Benefits of ozone application

Swimming water quality can be sufficiently increased by ozonization. This is not only a benefit when it comes to swimming, but it also guarantees healthy swimming water.

Recent research has shown that children’s immune systems may be affected by swimming in chlorinated swimming pools. The health risks are also increased for swimmers that train twice a day.

Purchasing an ozone system is relatively inexpensive compared to other techniques such as Saline Chlorine Generators, and an added benefit is that one can save costs on a long term.

Deactivation of resistant microorganisms by ozone:

The last decennia protozoa, such as Cryptosporidium Parvam and Giardia Lambia, have caused a large number of epidemics in the United States and Great Britain through drinking water [28,29,30]. In many cases, drinking water did comply with bacteriological quality standards. Consequentially to resistance of Cryptosporidium Parvum and Giardia Lambia in the environment and their resistance to disinfectants, direct purification of surface water much comply to very strict quality demands.

Protozoa spread through the environment rapidly as (oö)cysts (spores), which live longer and are more resistant to disinfectants than bacteria or viruses. In general, Cryptosporidium Parvum causes larger problems for drinking water treatment than Giardia Lambia does. Cryptosporidium Parvum is 4 – 5 µm in size, which makes it difficult to remove by conventional filtration [6]. Giardia Lambia is 8 – 14 µm in size, which makes it easier to remove by conventional filtration than Cryptosporidium Parvum [30]. Moreover, when drinking water or swimming pool water is treated by means of conventional chlorination, Cryptosporidium Parvum is insufficiently deactivated [28]. Alternative treatment methods, such as ozone and UV disinfection, appear to have the ability to deactivate the oocysts sufficiently

Edited for brevity and non-scientific explanation © 2010