| Composition of water |
When we open the tap, clean tasty water flows out. Water undergoes several purification steps before it flows from taps.
Water that is used for drinking water production contains water molecules and a large variety of other substances. One of the properties of water is that it easily dissolves other susbtances. Water that falls to earth during rain showers dissolves substances, particles and gasses such as oxygen, which can be found in air. Contaminants that are present in air also dissolve in rain water. When surface water flows on earth it also dissolves several different substances, such as sand particles, organic matter, microorganismss and minerals. Water that settles into the ground and becomes groundwater often contains large amounts of dissolved minerals, as a result of contact with soils and rocks. Human activities, such as agriculture and industrial waste and sewer water discharge cause a number of pollutants to enter the water.
Self-cleansing capacity of water
Water has the capacity to cleanse itself. Contaminants are removed from water during biological processes. When water settles onto the ground, groundlayers will cause filtration to occur. Contaminants are broken down, or will stay behind in the ground layer. The self-cleansing capacity of water is not strong enough to produce clean drinking water. This is a consequence of the quantity and variety of industrial and agricultural contaminants that have entered surface and groundwater for many decades.
In the 1970’s it was discovered that industrial discharges and waste water discharges were the cause of water contamination. Immediately after this discovery measures were taken to prevent water pollution. Waste water must meet legal standard before it can be discharged. To meet the standards water is purified before it is discharged.
Despite of these measures water often still needs treatment before it is suitable for use as drinking water.
During water purification waste water is treated to become drinking water which meets legal standards in the physical, bacteriological and chemical area. The water may not contain an odour or flavour, and it should be bright and chemically stable (non-corrosive).
The kind of treatment water needs, strongly depends upon the composition and quality of the water. Water treatment contains two process steps: physical removal of solid particles, mainly minerals and organic matter and chemical disinfection; killing or deactivating microorganismss in water.
More information on water disinfection?:
Introduction water disinfection Necessity water treatment History of drinking water treatment
What is water disinfection? Necessity of drinking water disinfection History of water disinfection Waterborne diseases Factors that influence disinfection Conditions of water disinfection Regulation drinking water disinfection EU USA
Swimming pool treatment Swimming pool pollutions Swimming pool disinfection Swimming pool disinfection & health
Cooling tower water Cooling tower water pollutions Cooling tower water disinfection Cooling tower water legislation
Chemical disinfectants Chlorine Sodium hypochlorite Chloramines Chlorine dioxide Copper silver ionization Hydrogen peroxide Bromine Peroxone Peracetic acid
Disinfection byproducts Types of disinfection byproducts Research on health effects of disinfection byproducts