Fig. 1.48. Mixers

a-swrll; б-with partitions; в-with whirlpool chamber; 1-water service; 2-water taking; whirlpool chamber of flakes creation; 4-a pipe with nozzles on a tangent; 5-vertical settling structure.

From the chambers of flakes creation the water gets into settling structures, where flakes fall out in sediment. Settling structures can be horizontal, vertical and radial, by its construction and water moving (fig. 1.49). Settling structures can be connected with flakes creation chamber in one building.

Horizontal settling structures (fig. 1.49a) – are rectangular, stretched in the plan by water moving, reinforced concrete reservoirs in which the water moves in horizontal direction from one butt end of the building to another.

Vertical settling chambers (fig.1.49б) – reinforced concrete reservoirs of round or square form in plan, in which the water moves vertically, as a rule, from top to bottom.

Radial settling chamber (fig.1.49в) – round reinforced concrete reservoir with small height comparing to diameter. Water moves horizontally from center to periphery in radial direction in it.

Fig. 1.49. Schemes of settling structures:

а-horizontal; б-vertical; в-radial: 1,3-pipe lines of water serve and taking; 2-gathering tray; 4-pipeline for sediment removing; 5-zone of settling; 6-device for even distribution of water; 7-farm for sediment sweeping.

Speed of water moving in settling structures is taken as 0.5-0.75 mm/sec for vertical, till 3-8 mm/sec for horizontal.

Settling structures with small settling depth – thin layer settling structures are used for intensification and cheeping of settling process. As a rule, blocks of plates are installed in usual settling structures for this(fig.1.50). Water is cleared in 10-15 minutes in such settling structures.

For water clearing, except of settling structures, hydrocyclons are used, in which separation of hard phase from liquid one takes place due to centrifugal force action (fig.1.51). Water that is cleared is served on tangent direction to the cylindrical part of cyclone. Hard phase (flakes) is thrown to the walls and slip down under the action of centrifugal force. Cleared water moves out through union coupling that is located in the upper part of hydrocyclon.

Fig. 1.50. Schemes of thin layer settling structures: a-with small inclination of plates; b-sharp-inclined: 1-water service; 2-cleared water; 3-washed water.	Fig. 1.51. Hydrocyclon: 1-cylindrical body; 2-intake pipe; 3-discharge union couple; 4-cone; 5-emission.

Connection of processes, that takes place in hydrocyclones and in thin layer settling structures, are conducted in settling structures with screw shelves (fig. 1.52), which are produced as cylindrical base with conic bottom. Central pipe with hardly fixed screw shelves on it is installed. Muddy water is served on the tangent to the upper part of settling structure, that allows to obtain rotational motion at the entrance to screw shelves by it, than it moves by descending spiral to the hole at the lower part of central pipe and is taken out beyond the borders of settling structure. In such cases the water is cleared in 6-15 minutes in settling structures.

Method of water passing through sediment layer is used during clearing (fig. 1.53). After mixer water gets into lower part of clearing up device, where sediment is located in hanged up state. This sediment promotes the intensive flakes creation.

Surplus sediment gets from clearing up chamber through windows into silt-compacting chamber, from which it is deleted. Speed of ascending flow equals to 0.5-1.2 mm/sec, that ensures an effective water clearing up, that is gathered by

trays and than gets on filters. After settling the final content of hanged up particles in water is allowed to be 8-12 mg/l.

Fig. 1.52. Settling structure with screw shelves: 1-body; 2-intake pipe; 3-discharge pipe; 4-hole of cleared water intake; 5-central pipe; 6-screw shelf.	Fig. 1.53. Settling up device with hanged up sediment: 1-intake pipe; 2-layer of hanged up sediment; 3-clearing up chamber; 4-overflow pipe; 5-ring tray; 6-additional overflow-pipe; 7-windows; 8-silt-compactor; 9-sediment output.