Invention relates to a method for utilizing kaoline or metakaoline that is created as a result of the thermal processing of kaoline in a water purification process in which process the water to be purified comprises impurities at least from one group which group belongs to the group: biological impurities, for example algae, fungi, viruses, bacteria, giardias, crypto sporidiums and other protozoans, organic impurities, for example agents that are harmful to health and environment and compounds that complicate production processes, for example extractive agents of the forest industry, inorganic impurities, like harmful metals and harmful metallic compounds, for example solid salamander and aluminium, heavy metals and in which case kaoline or metakaoline is added to the water to be purified. Previously the usage of metakaoline as an adsorption agent is known from a Japanese publication JP 3146414 in which it is demonstrated that the metakaoline and the zeolite are taken to have contact with a NaOH aqueous solution and are exposed to have an exchange of ions with a potassium solution in which case a strongly adsorbing substance can be achieved which substance is used in the ethylene production to remove the hydrogen.

The above mentioned solution is a special case and is suitable only for the adsorption of hydrogen. Now with the present, new invention the aim is to adsorb, thicken and settle down these impurities from the water containing impurities so that they can be collected from the bottom of the processing reservoir. The purpose of the method according to the invention is achieved with the characteristic features of the method so that kaoline or metakaoline is added as particles to the water to be purified either exclusively or together with intermediate agents, such as regulating chemicals of the pH or with a coagulating chemical which water is placed to a reservoir used as a processing space, to a flow- through reservoir or to a sufficient pipe extension in which the movement speed of the water is slowed down by increasing the cross-sectional area of the processing space to be essentially larger than the cross-sectional area of the inlet pipe, the removal of the mentioned particles from the reservoir with the water to be removed is prevented in which case due to the precipitation impact caused by the particles the impurities, precipitates and particles become settled at the bottom of the reservoir.

The method can also be applied as a column technique in which case the separation is based on the stream of the water to be processed through a kaoline or a metakaoline layer and the impurities become separated onto the surface of the granules with the help of an adsorption. It is characteristic for this embodiment that kaoline or metakaoline are let to affect as granules either exclusively or together with intermediate agents, such as with regulating chemicals of the pH or with a coagulating chemical the water to be purified in which case the granules are located to be a layer into a column used as a processing space to which column the movement speed of the water to be directed slows down due to a larger cross-sectional area of the processing space when the water penetrates the granule layer located in the column and when the granules cause the adsorption of the impurities onto the surface of the granules.

The advantage of the method according to the invention is that the impurities do not continue further with the water, but they can mainly be removed from the water unlike for example in several forms of the biological or chemical water treatment in which forms one tries to change the form of the impurities or the consistence into a less harmful form and one lets them however to mainly continue along the water. In the method according to the invention for example the harmful metals are tried to make settled at the bottom of the processing space from which they can be removed from time to time. Thus the method is a method that separates impurities from the water and improves the degree of treatment considerably even from the stage that one has first reached with a mechanical screening and filtering. The processing space for the method according to the invention can be formed for example to reservoirs, containers, pipe extensions and tunnels.

In the following the invention is described more detailed by referring to the

accompanying drawing in which

Figure 1 shows a reservoir construction as a processing space example to which reservoir construction a water purification method according to the invention is attached.

Figure 2 shows a purification column through which the water to be processed is directed. In the figure 1 the water to be purified comes along a pipe 2 to a reservoir 1 shown as an exemplary processing space which reservoir is sized in such a way that a retention time sufficient for the water, such as a retention time of several hours or most advantageously even more than a day, becomes formed in it. From the other end of the reservoir 1 the water becomes removed in a known way under the control plate 7 in which case the light particles staying in the surface water have no access out and they can be removed from the surface of the reservoir periodically. Such a slow stream is arranged to the reservoir with the help of a large cross-section towards the outlet pipe 3 so that the particles can settle down at the bottom and no forced motion of the particles with the help of the stream to the outlet pipe 3 does not occur.

The addition of kaoline or metakaoline to the water according to the method according to the invention is performed immediately at the forepart of the reservoir 1 at the location of the inlet pipe 2. In this case kaoline or metakaoline is located in a silo 4 in a powder form from which silo it is dosed through a valve 5 onto the surface of the reservoir most advantageously with the help of a known dividing apparatus in such a way that it comes to the surface covering the whole width of the reservoir. Kaoline or metakaoline powder is porous and surface charged and adsorbing and its particle size has to be under 0,1 mm, most advantageously under 0,07 mm so that it becomes settled at the bottom of the processing space during a delayed water stream. When it's mixed with water it has an property to adsorb impurities, become settled and form thickened parts 6 at the bottom of the reservoir 1 and thus purify the water above it. Due to settling property kaoline or metakaoline particles do not aim and cannot even be removed from the reservoir 1 under the control plate 7 in which there is also a stream upwards.

In one embodiment there is a mixing rotor at the forepart of the reservoir 1 and possibly a mixing chamber in which case kaoline or metakaoline particles can be mixed well with the water. After that there is a resting space in the reservoir in which the stream is so slow that the settling of the particles can occur. In one embodiment kaoline or metakaoline is added to the inlet pipe 2 sufficiently before the reservoir 1 in which case the mixing in the tube stream occurs in a simple way without auxiliary devices. The whole reservoir can then function as a settling and thickening reservoir. There can be a plate controlling the inlet stream at the end of the inlet pipe 2 which plate eases the whirlpools of the inlet stream straight at the first part of the reservoir.

The deposit 6 that is accumulated at the bottom of the reservoir 1 is removed from time to time in a such known manner, such as it usually happens from the deposit reservoirs either with the help of scraping or by emptying through a drain plug. The deposit contains kaoline or metakaoline and agents that have adsorbed to it. It is possible to free kaoline or metakaoline from the adsorbed agents for example by dissolving and thus get it back for use.

The vertical column 8 in the figure 2 contains kaoline and/or metakaoline as granules 9 the particle size of which is over 0,1 mm. With a particle size that is even over 0,5 mm good results can be achieved, too. Granules are surface charged and adsorbing and the water to be purified and directed from the inlet pipe runs through the granule layer located in the column 8 in which case impurities will stay on the surface of the granules 9. The granules 9 are on top of the sink gill net 12 and the water is removed from the column through a bottom water outlet 11. The columns 8 are usually constructed in such a way, for example equipped with an opening bottom that the changing of the mass to them can easily be performed. The column 8 can be closed or unclosed at the top. Also the granule mass can be located to be a layer in the processing space in such a way that the water runs through the mass in horizontal direction.