Basic requirements of Swimming Pool Water Treatment

1. Water Circulation
2. Flow Rate - explanation of turnover time and the importance of
filtration and circulation
3. Dilution - addition of fresh water

Swimming pool water treatment - the basics

The primary objective of pool water treatment is to maintain the water in a safe and pleasant condition for swimming and to :

• keep the water free of pathogenic (harmful ) bacteria
• keep the water free from growths of algae
• ensure the water is neither toxic nor irritating to swimmers (through high chlorine levels or high pH levels)
• prevent the formation of undesirable smells or taste in the water
• prevent corrosion of the pool surround, its fittings and equipment
• prevent scale formation in the pool, filter or pipework.

Flow rates and turnover

Pools become polluted at different rates. Generally the shallower the water the more bathers per cubic metre, and an open air pool has greater surface pollution than an indoor one.
Turnover is the number of hours it takes the filter to pass one complete volume of pool water.
Filter rating m3/hr. The filter rating is the flow of water through it designed to achieve a specified degree of clarification, say down to 10 micron, or 0.01 mm, within a certain period of time. So each type of pool requires its own matched filter to develop a satisfactory turnover period.

If you need advice on choosing the right size filter for your application, discuss it with your equipment supplier

Hotel and Health Club pools may be able to have a longer turnover period than an equivalent public or leisure pool if there are strict limits on bather loads and the time the pools are used. The Design Bather Load should be known and enforced by operators at the entrance. Similarly, school pools may have been designed to have 'rest' periods between classes.

Dilution

Disinfection of the water and the filtration process will not destroy or remove all of the pollutants present. A program of dilution of the pool water with fresh water is desirable to reduce the build-up of pollutants from bathers and the by-products of the disinfection process (such as cyanuric acid).
Back washing the filter dilutes the water to some extent because this water flushed to drain must be replaced. Unfortunately this is not frequent enough to maintain the concentration of undesirable pollutants at an acceptable level in comercial applications.
Some pollutants can only be reduced by dilution – organic chloramines like chlorcreatinine for example, cannot be broken down by chemical means.
A useful guide as to volume required is 30 litres per bather per day in a public pool, which should give benefits of lower levels of pollutants and hence reduce the use of the treatment chemicals themselves.