Production in greenhouse horticulture in Europe is still not as efficient in the use of water as it could be. Growth systems without soil (hydroponics) are becoming common in horticulture from most European countries, although no large scale in all countries. The advantages of soil -less growing systems compared to crops grown in soil are:
· The growth and harvesting are independent of the type of soil in the area of culture;
· Better control of growth by use of improved water pitcher filter quality and a better fertilization;
· Increased product quality;
· Start free of pathogens by using different substrates on the ground and / or easier soil pathogen control.
The disadvantages of these systems are:
· The high quality of water required;
· High investment and high costs of fertilizers;
· Low amount of water.
In most cases open or run the water systems are adopted. In such open systems, the nutrient solution is left freely lava ground and surface waters. For economic reasons and environmental concerns can be applied soilless closed systems. These closed systems are more efficient with the use of water and fertilizers, and cause less damage to the environment. The disadvantage of closed systems is the risk of a rapid spread of soil-borne pathogens due to the recirculation of the nutrient solution. To eliminate these pathogens, they can be used various methods of disinfection.
Treatment with ozone can be used to disinfect the drain water  . Ozone is the second most powerful sterilant is known and its function is the destruction of bacteria, viruses and odors. A contribution of 10 grams of ozone per hour and cubic meter of water is enough to kill all pathogens.
Another way to disinfect water drainage is to use UV radiation  . The ultra (or UV) radiation violet is a proven process for disinfecting water, air and solid surfaces microbiologically contaminated. To remove bacteria and fungi an energy dose of 100 mJ / cm is recommended 2 . For viruses a dose of 250 mJ / cm is recommended 2 .
When a treatment is applied by heating, a solution is heated for 30 seconds at 95C. At this temperature all pathogens are killed  . A disadvantage of heat treatment is gas consumption. Also the drain warm water contains less oxygen.
|Slow sand filtration
For a few years commercial farmers have been using facilities slow filtration through sand to remove pathogens.   Sand filtration is frequently used as a very effective way to remove suspended solids in water method. The filter medium consists of a series of layers of sand with a variety of grain sizes and specific gravity. Sand filters are available in different sizes and both manual and fully automatic operation materials.