Sediment bowls

Sediment bowls represent tanks in which water arrives on a narrow pipe. Arriving from a narrow channel of a pipe in wide space of the tank, it so slows down the movement (about 1 m to several millimetres in 1, that almost comes nearer to a rest condition. As a result weighed substances by gravity settle on a bottom of a sediment bowl in the form of a deposit. Speed of subsidence of the weighed particles is influenced by water temperature, and also the sizes and the form of particles. Dependence between the sizes of the weighed particles and their speed of subsidence.

From the table it is visible, that at upholding of water within several hours will settle only the large weighed particles having diameter to 0,01 mm. Depending on a direction of movement of water sediment bowls share on horizontal (usual and radial) and vertical.

Usual horizontal sediment bowls are rectangular tanks, walls and which bottom are concreted. Upholding time in them fluctuates from 2 to 8 ch. Depth of sediment bowls reaches 3-5 m. Water in them moves from one face wall to the opposite. The big sediment bowls have some sections (vertical partitions). The bottom in such sediment bowls with a bias that in a forward part of section the greatest part of a deposit (it dropped out is necessary for clearing improvement). The deposit except the weighed particles contains eggs gelmintov and bacteria.

Clearing of sediment bowls of the collected deposit occurs to the help a fire engine (water streams) or mechanical by (scrapers).vertikalnye sediment bowls have the roundish or rectangular form with a conic bottom. In the centre of such sediment bowl there is a pipe. The Sediment bowl-osvetlitel with the weighed deposit which part arrives water. Hence, water moves on this pipe from top to down, then arrives in actually ostojnik where moves upwards with very small speed. Thus weighed particles settle. Having reached to verhnogo sediment bowl edges, water is poured through a ring trench and goes to taking away pipe. Time of stay of water in a sediment bowl same, as well as in the horizontal. Accumulated in the bottom part of a sediment bowl a deposit periodically delete by means of an exhaust pipe.

Now apply new type of sediment bowls where clarification goes in a layer of the weighed deposit - a sediment bowl-osvetlitel with the weighed deposit. It represents the cylindrical tank in which centre the pipe (fig. 11) is located. From the central pipe located vertically, two horizontal tubes having from below apertures depart. As well as vertical, the sediment bowl-osvetlitel has a cone-shaped bottom. Water for clearing moves on the central pipe in the bottom part of a sediment bowl through apertures in horizontal tubes. It allows it to be distributed in regular intervals on the area of horizontal section osvetlitelja and to rise with small speed upwards, passing through a layer of the weighed flakes koaguljanta and before the detained deposit. Thus in the weighed layer there is a formation of new flakes koaguljanta, brought with the clarified water that promotes more effective detention of the weighed substances in comparison with a vertical sediment bowl. Having passed a layer of the weighed deposit, water arrives in a zone of the clarified water, is poured in a trench which is taking away water on the filter.

As in osvetlitele all time is formed a deposit of flakes and a suspension its superfluous quantity is sucked away in a sealant, whence is dumped in the water drain.

Advantage of a sediment bowl-osvetlitelja thanks to which it gains the increasing distribution, the smaller expense koaguljanta is.

Water Filtering is necessary for its clearing of the weighed substances, not arrested persons at the first stages of clarification of water of coagulation and upholding. Thus water is partially cleared and of microorganisms.

During filtering water pass through melkoporistyj the material detaining weighed particles. As such material use sand more often.

Water Filtering is carried out on special constructions - filters. Clearing on filters considerably is at a loss, if the water processing preliminary is not spent, allowing to remove from it a plankton (the smallest animal and vegetative organisms: zoo-and a phytoplankton). Preliminary processing is carried out on the microfilters representing a skeleton, fitted by a fabric from the most thin corrosion-proof steel wire. Such microfilter detains from 75 to 95% of seaweed and to 35% of the weighed substances.

Then water arrives on filters. Most often apply the fast filters passing water with speed of 5-7 km/h. The fast filter is a ferro-concrete tank with a double bottom: the bottom continuous and top perforated. On the top bottom the layer of a supporting material - gravel and a layer of a filtering material - sand is filled. Water which is filtered through a layer of sand, gravel from above moves and through a perforated bottom gets in poddrenazhnoe space, and from it on a pipe to the tank for pure water.

The Suspension is late on a surface and in the top layer of sand (10-15 sm) which through 8-12 ch works is condensed. Resistance which is tested by water, passing through thickness of sand, thus increases, and there is a difference between pressure of water over the filter and in drainage space. It is expressed by loss of a pressure and often serves as the indication to filter washing.

Passing a water considerable quantity, fast filters, naturally, quickly get littered and clearing demand. Their clearing is made mechanically by the current of the pure filtered water directed from below upwards with the big speed. Thus the sand layer vzmuchivaetsja, collapses a filtering film and sand is washed from pollution which together with washing water is poured in the national teams of a trench located over a layer of sand, and taken away in the water drain. Filter washing occupies about 15 minutes

To increase productivity of the filter, it load two layers of a filtering material. Such construction name fast filters with two-layer loading. They are arranged the same as also the fast filter. The filtering material is filled up by two (height 40-50 sm) layers: from below sand with diameter of particles 0,5-1,2 mm, and from above a layer antratsitovoj crumbs or droblenogo keramzita, having larger diameter of particles-0,8-1,8 of mm. Water for filtering moves from top to down with a speed of 10 km/h.

The Academy of municipal services of the USSR offers filters AKH (fig. 14), differing to that water for filtering moves both from above and from below through drainage space on which there is a gravel layer. It allows to use and the bottom layer of sand which are not participating in filtering in usual filters to raise productivity filtrob db 12-15 km/h. In thickness of sand on border between the top and average third of loading drainage pipes for gathering and tap of the pro are located? ltrovannoj waters. ypaBHOj veshennoe pressure in the top and bottom parts of the filter does not allow to wash away sand in the course of a filtration.

Recently in municipal practice the new type of a construction for the water clarification, combining in itself all three its stages - koagulirovanie, upholding and filtering has found application. It is contact osvetlitel. It represents the tank filled on 2,3-2,6 m with gravel and sand in such a manner that the size of particles of a loading layer gradually decreases in diameter in a direction from below upwards. Water moves from below through drainage pipes. Before an input in osvetlitel, i.e. Directly ahead of filtering, in water the solution koaguljanta arrives. Thus flakes koaguljanta are formed in thickness of loading (contact coagulation), as has caused the name of this construction. Speed of a filtration of water in contact osvetlitele makes 4-5 km/h.

Contact coagulation promotes faster formation at contact with granular loading and at smaller doses koaguljanta flakes and adsorption on them of the weighed particles. In the bottom layers of a loading layer larger suspension that warns zailivanie sand is late and extends time between washings. Washing is carried out the same as also fast iltrov.

Application of these constructions allows to refuse the equipment of special chambers of mixture, reaction and sediment bowls that is economically more favourable. However at big mutnosti the water making more 150 mg/l to apply contact osvetlitel it is not recommended.