Wastewater treatment by filtering them through the soil allows to obtain high quality water. Distinguished fields and fields of filtration irrigation. Filter fields are only used for wastewater treatment, powers the maximum possible amount of water. Irrigation fields are the share of crop production and supply liquid on them is limited to the needs of plants. Wastewater treatment method of filtering through the soil is used for a long time, but the shortage of arable land, the growth of land prices restricts use of filtering fields. Field irrigation in arid areas and will be applied in the future.

The process of self-purification of the soil is carried out at the expense of vital activity of soil organisms: bacteria, mushrooms, algae etc.. In sterile soil self-cleaning impossible. The main role in the processes of purification of soil bacteria and fungi belong. They settled on the surface soil lumps, between which seeps clean water. Nutrients microorganisms obtained from wastewater, and necessary for the oxidation of oxygen from the atmosphere and partly through photosynthetic aeration, performed on the soil surface algae. Penetration of oxygen into soil is restricted to 20-30 see and because the intensive mineralization of organic matter is observed only in the surface layers.

A significant role in the processes of wastewater treatment in the fields of filtering play nitrifying bacteria, perform the function of "preserving oxygen». A significant role in such methods of purifying plays microfauna. Soil worms loosen topsoil, facilitating the penetration of oxygen into the soil. A large impact on the speed of filtration provides soil structure. On sandy soil filtration speed 0.01-1.0 cm/s, on the mudflats of less than 0.001 cm/s. For this reason, it is recommended to arrange filtering fields on sandy and sandy soils, and clay are unsuitable for this.

Before serving the field of irrigation waste water advocates, to avoid causing siltation of soils due to suspended solids, contained in waste water. Water, the last cleaning and filtering the sewage contains practically no pathogens and eggs gel′mentov, has a high number of subpicture and chemical indicators. The fields are a danger in sanitary = epidemiological relation. For this reason, in the fields of irrigation, it is prohibited to grow crops, Edible raw.