FI64745B - FOERFARANDE FOER FRAMSTAELLNING AV VID AVLOPPSVATTENRENING ANVAEND KALKMJOELK - Google Patents

Description

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Sweden-Sverige (SE) 7607957 ~ 3 (71) (72) Stig Arvid Henrikson, Grönviksvägen 103, S-16l to Bromma, Sweden-Sverige (SE) (7M Oy Heinänen Ab (5 ^ +) Method for lime used in wastewater treatment - for the manufacture of milk - Förfarande för framställning av vid avloppsvattenrening använd kalkmjölk

The present invention relates to a process for preparing lime milk for use in the treatment of waste water, in which lime is fed to a lime solvent forming a lime slurry, and in which the lime slurry is passed to an actual lime milk as a homogeneous solution to be added to the effluent.

In the production of lime milk, it is known to use a production device comprising inclined lamellae through which the lime slurry flows. Such a device is disclosed, for example, in SE patent publication 330 152.

The object of the invention is to provide a more efficient method for producing lime milk based on the use of said device. The method according to the invention is characterized in that in the lime milk production apparatus a slurry zone 1 is provided in the lower part of said sloping lamellae, where the surface load of the lamellae is about 2.5 m / m / h and in which the is about 1.25 m / m / h and in which the finer particles are separated, and that at least part of the lime slurry leaving the sloping lamellae and settling to the bottom of the lime milk making device is returned to the lime solvent. The invention achieves a high cleaning efficiency with the lowest possible lime consumption and at the same time avoids problems related to filling and flocculation as well as other operating problems occurring in the cleaning plant.

The invention will be described in more detail below with reference to the accompanying drawings, which show an embodiment of a wastewater treatment plant in which the invention is applicable.

Figure 1 shows schematically a complete treatment plant comprising devices for dispensing lime into waste water.

Figure 2 shows in more detail and on a larger scale a section of lime nreido production equipment.

Figure 3 shows the same apparatus seen from above.

The treatment plant according to Figure 1 comprises six pools 1-5 arranged in succession, through which the water to be treated passes alternately. Basin 1 includes a sand filter and a mechanically cleanable flap. Pool 2 is an aeration pool with activated sludge. Pool 3 is an external boiling pool. Lime milk prepared in the apparatus indicated by reference number 7 is introduced into the basin 4. The steamer marked with the reference number 5 ori and the foaming basin with the reference number 6 from which the purified water leaves as a patch. The construction of a treatment plant can, of course, vary in many ways without any relevance to the process of the present invention.

The apparatus 7 comprises a lime solvent 6 and a lime milk preparation device 9. The lime solvent 8 comprises a dissolution tank for dissolving dry, slaked or quicklime. In this tank, the mixer mixes 10 lime with the dissolving water introduced into it. As the dissolution water, effluent, purified wastewater with a pH of 10-12, biologically purified wastewater or tap water can be used. The amount of dissolution water should be about one liter of water per 1.7 g of lime.

From the dissolution tank 8, the lime slurry is allowed to exit to the actual lime gluing device 9, where it enters the pipe 11 into a centrally conical space 12, which acts as a lime slurry pocket.

The lime slurry exits upwards, passing between a plurality of lamellae 13 and 14, after which it flows away on both sides over the gutter table 15 into the gutters 16.

The lengths of the lamellae 13 and 14 vary. In the case shown in the drawing, every other lamella 13 is long, while the lamellae 14 between them are short. Thus, the lamellae 13 have a length of 2 meters and are spaced 15 cm apart, while the lamellae 14 are only 1 meter long and are likewise arranged at a distance of 15 cm from each other.

The zone comprising only the long lamellae 13, i. the lower half of the lamella pack, is dimensioned so as to provide a stationary sludge zone at this point. The sludge zone provides filtration of the upwardly moving lime sludge. Above the sludge zone, which has twice the number of lamellae 13 and 14, a clarification zone is created in which the finest particles separate as the lime milk rises.

The slurry zone in the upward flow is thus provided in such a way that the surface load 4,647,45 of the lower parts of the lamellae 13 is substantially higher than the surface load of the lamellae 13 and 14 in the upper region of the clarification zone. The surface load of the lamellae 13 in the sludge zone is in practice about 2.5 m / m / h, while the surface load of the lamellae 13 and 14 higher in the clarification zone is 3 2 about 1.25 m / m / h. Surface loads are calculated using the projected surfaces of the lamellae as a starting point.

The sludge that follows the lamellae and collects in the bottom cone 12 is about 10-15 times denser than the sludge water in the sludge zone and fills a space that is about one tenth of the space between the lamellae 13. Some of the lime sludge accumulated in the bottom cone 12 is pumped to the lime dissolution tank 8 and the remaining lime sludge is removed by gravity from one of the units in the treatment plant located before the lime milk addition point (e.g. the pre-treatment device). The amount of lime slurry pumped back into the dissolution tank 8 can be determined in practice on the basis of the concentrations of sand and impurities in the lime used in each different case. Reference numeral 17 denotes a lime sludge pump which leads the lime back to the leach tank 8 along the pipe 18 and which returns the lime to the pretreatment plant along the pipe 19.

At point 20, lime is dispensed and at 21, lime-lime solution is dispensed into the wastewater.

The invention is not limited to what has been described above and shown in the drawings, but can be varied in many ways within the scope of the following claim.

Claims (1)

CLAIM 64745 A process for preparing lime milk for use in the treatment of waste water, in which lime is fed to a lime solvent (Θ) to form a lime slurry, and in which the lime slurry is passed on to the actual lime milk production plant ) and from the top of which the finished lime milk is removed as a substantially homogeneous solution for addition to the effluent, characterized in that the lime milk production device (9) h and in which the upwardly rising lime sludge is filtered, and at the top of the lamellae (13,14) the cooking zone 1 in which the surface load of the lamellae is about 1.25 m / m / h and in which the finer particles are separated, and at least part of the lime sludge leaving the sloping lamellae, which settles in the manufacture of lime milk to the bottom of the appliance, return to the lime solvent (8).