Selection of effective chemical compounds for drilled wells

Drilled wells during their operation are subject to so-called “aging” processes, which is visible in the decrease of their efficiency and increase in depression. The process, especially in case of quaternary and tertiary waters, is most affected by the chemical colmatation of the filter and filter-adjacent zone with chemical compounds precipitated from the flowing water. The literature analysis shows that ferrous sediments are the main mass of sediments clogging the quaternary and tertiary water intakes. They are usually in the form of soft reddish-colored sediments, and their essential element is Fe2O3 and FeO. Iron, siderite and quartz hydroxides were also found. The degree of colmatation in such wells can be significantly reduced by frequent renovations with chemical methods. The article presents results of laboratory tests on dissolution of sediments clogging withdrawal well filters with sodium dithionite (Na2S2O4) and sodium pyrosulphite (Na2S2O5). Representative samples were taken from selected quaternary water intakes in northern Poland.