UNDERGROUND WATER QUALITY IN THE NORTH AREAS OF THE OMSK REGION
Fresh groundwater in the Omsk region is theoretically one of the most reliable sources of providing the population with drinking water, protected from pollution from the surface. However, a number of areas practically do not use groundwater due to their substandard quality and the availability of other sources of water supply - Irtysh and the river Om. Along with climatic conditions, the mineralization and chemical composition of groundwater is affected by the level of water exchange, which depends on the lithological composition of the rocks. The results of monitoring studies of underground water sources in the Omsk region show that the most frequent water pollutants are iron, manganese and ammonia. The source of iron is clay rocks and rocks of organogenic origin, which dominate in the Neogene-Quaternary and Oligocene-Miocene sediments. The transition of iron from rocks to water is carried out under the influence of oxygen in the aeration zone. The increased iron content depends not only on the presence of soluble iron compounds in the rocks, but also on the oxidation-reduction medium. Underground iron-containing waters usually have bicarbonate forms of iron in 80-90 % of cases. At the same time, regardless of the concentration, these types of water also contain iron bacteria, which are inactive in the initial form in the anoxic environment of the underground water intake. However, when water enters the RFH or the water tower, oxygen enrichment occurs, causing rapid development of iron bacteria, and they become a biologically active corrosion structure. Therefore, any methods of iron removal from water, which do not involve the removal of iron bacteria and these methods are ineffective.