Encyclopedia

General information on ion-exchange resins and principles of ion-exchange processes

The preliminary treatment is not enough for make-up water used in boilers and feed water used in the heat networks. The final stage of water treatment that relates to change of its ion composition till the complete removal of dissolved impurities, is performed by means of the ion-exchange method.

The water clarification process by means of filtration basically is performed by adhesive volumetric filtration in the vertical clarifying bed filters. The filter consists of a cylindrical vessel with spherical bottoms welded to it. The vertical one-chamber filters with diameters of 1.0, 1.4, 2.0, 2.6, 3.0 and 3.4 m are commercially available. Inside the filter there are filtering bed layer and drainage and distribution assemblies intended for uniform distribution and collection of water per filter's cross section area. The upper drainage and distribution assembly is made in the form of the cover plate that absorbs incoming water energy; bottom drainage and distribution assembly consists of a collector with the side bends equipped with specially designed slotted caps or slotted openings with a width of 0.4 mm to discharge water and prevent loses of the filtering material.

General information

Since natural waters contain impurities with various particle size it makes necessary to treat such waters in several stages. First stage is intended for removal of colloidal and suspended solids, and the subsequent stages - for removal of ion-dispersed substances and dissolved gases. Such system approach to the selected sequence of water treatment methods is aimed at the improvement of technical-and-economic indexes of various treatment stages and allows to automate the work of certain equipment and enhance reliability of water treatment plants in general.

General information

Clarifying (mechanical) filters are used to clean surface sources' water from particulate pollutants or clean clarified water from finely-dispersed sludge downstream the clarifier. During the filtration of water through the porous media the suspended particles are retained inside or on the surface of the ion-exchange resin, as a result the permeate is clarified.

The key water quality parameters intended for use in the heat power industry are as following:

concentration of particulate pollutants;
concentration of truly-dissolved solids (ion composition);
concentration of corrosive gases;
Read more ...

The complete operation cycle of the ion-exchange filter consists of the following stages:

loosening;
regeneration (supply of the regeneration solution);
backwash;
filter run.

Natural waters are classified by several factors, the most common of them is a salt content: salt content of fresh water is up to 1 g/dm³, brackish water - 1-10 g/dm³, seawater - more than 10 g/dm³. Salt content of river and ground waters may vary from 50-200 up to 1500-2000 mg/dm³. The largest amount of dissolved impurities is contained in ocean and see waters, g/dm³: the Baltic Sea - 11, Caspian Sea - 13, Black Sea - 19, Atlantic Ocean - 36.

By the prevailing anion content waters are classified into hydrocarbonate, chloride, sulphate waters. Fresh waters usually belong to the hydrocarbonate class, as the hydrocarbonate content in such waters amounts to 60-70%.

Water treatment by ion-exchange methods

Water clarification in bed filters

Preliminary water treatment by means of coagulation and precipitation

Water clarification by filtration methods

Water quality parameters

Operation of ion-exchange filters

Classification and characteristic of impurities of natural waters