DK143268B - DEVICE FOR CHEMICAL-MECHANICAL CLEANING OF WASTE FLUID - Google Patents

Description

143263

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a wastewater treatment apparatus for the chemical-mechanical purification of a wastewater comprising a coagulation chamber in which materials stored in the wastewater to be treated are adsorbed on hydroxide flux formed by the addition of a coagulant and an alkali. to the waste liquid, and a flotation and separation chamber arranged around the coagulation chamber in such a way that it encloses this and in which the flakes coming from the coagulation chamber and on which the slurry material is adsorbed are then caused to float up and excrete from the wastewater.

Oil-contaminated wastewater from plants, etc., has so far been purified by means of an apparatus of the type shown in FIG.

1 of the drawing, but such an apparatus has the disadvantage of having an undesirably large size and entails high installation costs.

The FIG. 1, an oil-water separator 1, e.g. a gravity separator in which a primary separation of oil and water from an oil-contaminated wastewater is effected, and one end of a wastewater feed line 2 containing a pump 3 opens into this oil-water separator 1. In the oil-water separator 1 most of the wastewater is separated into oil and water (primary treatment).

The oil-water separator 1 is connected to a coagulating tank 5 by means of a tube 4, and an oil-contaminating waste liquid which has undergone the primary treatment in the oil-water separator is fed into the coagulation tank 5 through this tube 4. A coagulant supply tube 7 which is provided with a pump 8, is therefore connected at one end to the pipe 4, while the other end opens into a coagulant storage tank 6, in which a coagulant such as e.g. alum cake, magnesium salt or seawater, is stored. An alkali supply pipe 10, in which is mounted a pump 11, has one end connected to the pipe 4 at a point at a distance from the connection with the coagulant supply pipe 7 to this pipe 4, and the other end opens into an alkali storage tank 9, in which can be found slaked lime or another alkali. Further, an auxiliary coagulant supply tube 13 is connected at one end to the coagulation tank 5 and at the other end to an auxiliary coagulant storage tank 12, e.g. a polyacrylamide type, which auxiliary coagulant supply tube 13 is also provided with a pump 14.

In the coagulation tank 5, the wastewater supplied from the oil-water separator 1 having a low oil concentration is mixed with the coagulant supplied by the pump 8, the alkali supplied by the pump 10 and the auxiliary coagulant supplied by the pump 14. The coagulation treatment in the coagulation tank 5 is carried out as follows:

For example, if a solution of slaked lime as alkali is used, in the tank 5 aluminum hydroxide flux is formed by the following reaction: A12 (SO4) 3 + 3Ca (OH) 2 - ^ - 2Al (OH) 3 + 3CaSO4

The small amount of oil contained in the waste liquid is adsorbed on the flies. In this case, anionic compounds are mainly used as auxiliary coagulant because anionic compounds will neutralize the positive charges on the aluminum ions supplied as coagulant thereby facilitating the formation of fluff and at the same time enable these fluffs to coagulate to larger masses.

The coagulation tank 5 is connected to a flotation separation tank 16 by means of a pipe 15, and the flotation separation tank 16 is connected at its rear end to a drain pipe 23.

A pressurized water supply pipe 22 is connected at one end to the pipe 15 which connects the coagulation tank 5 to the flotation separation tank 16 and at the other end to a pressurized water tank 17. The pressurized water tank 17 is filled with a filling material such as e.g. Rigging rings and one end of a water supply pipe 18 are connected to the top of this tank, while the other end of the water supply pipe 18 through a pump 19 is connected to a water tank not shown. The pressurized water tank 17 also communicates with a compressor 21 through a compressed air supply pipe 20, which is connected to the bottom end of the tank.

The water supplied from the water supply pipe 18 to the pressurized water tank 17 dissolves in the tank a predetermined amount of compressed air which is supplied from the compressed air supply pipe 20 during passage through the layer of Raschig rings and fed to the flotation separation tank 16 through the pressurized water supply pipe 22.

In the tank 16, by reducing the pressure in the supplied pressurized water to atmospheric pressure, a number of air bubbles are formed and these air bubbles abut the aluminum hydroxide flakes on which the oil is adsorbed and seize these flakes. The flies thus caught by the air bubbles float together with the air bubbles and are separated from the waste liquid.

This wastewater purified in the manner described is discharged through the drain pipe 23.

In most conventional apparatus of the type described above for treating oil-contaminated wastewater, the coagulation tank and flotation separation tank are independent of each other, and the volume of the former is generally twice as large as that of the latter.

It has therefore been inevitable that the whole apparatus will be very large, since it is impossible to manufacture the apparatus in a compact form, and this inevitably entails large installation costs.

From German Publication No. 2,016,414 an apparatus for purifying lacquer contaminated water is known. This apparatus comprises a coagulation tank and a separation tank which are assembled into a cylindrical unit so that the coagulation tank is in the form of an inner cylindrical container which is completely or partially surrounded by the separation tank in the form of an annular chamber system. The annular chamber system comprises, in the radial direction from the center and outwards, first an addition mixing chamber, then a deposition ring chamber and then an overflow and a drain ring chamber. -In the bottom of the centrally located cylindrical coagulation vessel, lacquer contaminated water, via a second conduit coagulant, via a third conduit compressed air and via a fourth conduit, radiate water is introduced. During operation, a foam is formed in the coagulation vessel by supplying said components moving upwardly into the coagulation vessel and beyond its edge. The overflow foam is trapped in the first surrounding annular chamber - the additive mixing chamber - whereby a further admixture of compressed air can be effected by supplying compressed air to the lower portion of this chamber. From the addition mixing chamber, the foam flows beyond the outer boundary wall of the addition mixing chamber and into the outlet

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4 chamber. In the deposition chamber, the foam is deposited as a cool mud on the surface of the foam-liquid mixture collected in this chamber. The foam is removed from the surface by scraping with a wiper while the liquid collecting in the lower part of the chamber flows through a filter located in the lower part of the outer boundary wall of the deposition chamber and into the overflow chamber. From the overflow chamber, the treated and purified liquid (water) flows over the outer boundary wall of the overflow chamber and into a surrounding drainage channel from which it is led away.

Thus, the apparatus known for the purification of lacquer-contaminated water known from this German publication is characterized in that the coagulation tank is a centrally placed container surrounded by the separation tank in the form of an annular chamber system and in that the liquid-foam transport in the apparatus takes place solely in the radial direction. , possibly combined with some up and down movement in the individual chambers. In the liquid-foam transport of this apparatus, the traveled flow path length will be relatively short - substantially no longer than the radius of the entire apparatus - which will allow poor contact between air bubbles and the material to be excreted at the same time as The liquid-foam transport in the apparatus tends to take place only along the surface of the liquid-foam content of the provided ring chamber system, whereby the internal volume of these chambers will not be efficiently utilized for separation purposes. Both of these aspects of the apparatus will thus contribute to a poorer separation of the material which is sought to be separated from the liquid.

The present invention relates to an apparatus for chemically mechanical purification of a waste liquid comprising a coagulation chamber in which materials suspended in the waste liquid to be treated are adsorbed on hydroxide flux formed by the addition of a coagulant and an alkali to the waste liquid, and a flotation and separation chamber arranged around the coagulation chamber in such a manner that it encloses this, and in which the flies coming from the coagulation chamber and on which the suspended material is adsorbed are then brought to flow and separated from the waste liquid which apparatus is characterized in that the coagulation chamber is provided with an axially bottomed inlet for the coagulant and hydroxide-mixed wastewater to be cleaned, and with at least two axially located concentric cylinder walls arranged to force the liquid to flow alternately up and down through passages between them from the center and outwards in a radial direction successive cylindrical walls and finally upwardly in a passage between the outer cylinder wall and the inner wall of the coagulation chamber to an annular outlet located at the top of this wall, the flotation and separation chamber being divided by means of radial partitions. an inlet chamber, an actual flotation chamber, optionally with one or more pre-treated inlet chambers and a collection chamber for the flocculate, one of which radial partitions are common to the inlet chamber and the collection chamber, the inlet chamber which is in flow communication with the annular configured as an overflow threshold which forms the inlet of the liquid to the actual flotation chamber possibly through one or more pretreatment chambers, and the second partition in the collection chamber is also configured as an overflow threshold which provides access for the flocculate from the actual flotation chamber to the separator the sump chamber, which is furthermore provided at the bottom with a drain for the flocculate, in which at the bottom of the actual flotation chamber immediately before the radial partition adjoining the withdrawal chamber, there is a discharge tube for the purified liquid.

Compared to the prior art technique for purifying oil-contaminated wastewater, the apparatus according to the invention has the following advantages: (a) since the flotation and separation chamber, which has a larger volume than the traditional separate coagulation tank, is incorporated as an integrated and compact part of the apparatus , the installation costs for the apparatus will be lower than for the traditional apparatus containing the coagulation tank as a separate tank; (b) for the same volume, the flotation and separation chamber of the invention may have less width than that of the conventional apparatus; (c) in a conventional flotation and separation tank, which is given a large volume to prevent air bubbles adsorbed to a fluff from being separated from that fluff, a plurality of current distributing plates are generally disposed on a such that the width of the tank is divided in an attempt to achieve a smoother flow of the waste liquid, while such distribution plates are unnecessary according to the invention, since the flotation and separation chamber can be designed with a relatively small width; (d) in order to achieve effective contact between the air bubbles and the flakes in the flotation and separation tank, it is advantageous if the apparatus is smaller in width and greater in height and the arrangement of the apparatus according to the invention is advantageous in this regard; (e) since the volume of the flotation and separation chamber of the invention can be made larger than the volume of the coagulation chamber, it is possible by arranging these chambers in series to inject the pressurized water in two stages.

Because of these advantages, it is possible to substantially increase the efficiency of separation in the flotation and separation chamber relative to the conventional apparatus.

Compared to the apparatus known from German Publication No. 2,016,414, the apparatus according to the invention is advantageous as follows;

The apparatus according to the invention - like the apparatus according to the German publication publication - has a centrally located coagulation chamber in which the predominant fluid transport will be radial, but in the design of the chamber it is ensured that this radial movement will be combined with an effective up and down movement , so that the path length traveled will be substantially longer than the immediate radius of the coagulation chamber, and so that the internal volume of the coagulation chamber is utilized effectively, both aspects of which will promote the adsorption of the oil to the produced fluff.

The apparatus according to the invention - like the apparatus according to the German publication publication - has a flotation and separation chamber surrounding the coagulation chamber as an annulus. In the flotation and separation chamber according to the invention, however, the liquid transport takes place as a one-way flow along the outer circumference of the coagulation chamber, where in the corresponding annulus of the apparatus according to the German publication specification, it is conducted as a radial flow on the surface of the liquid chamber substantially in the ring chamber. The traveled path length of the fluid flow in the flotation and separation chamber according to the invention is hereby considerably longer, and the flow will comprise an efficient fluid transport comprising the entire volume of the chamber. Both of these aspects of the design of the flotation and separation chamber will promote the possibility of effective contact between the air bubbles and the material to be separated, and the longer travel flow path length will further allow the material to be combined with air bubbles to be separated when to float to the surface before the outlet end of the chamber.

In addition, at the bottom of the chamber, supply means for pressurized water containing pressurized air are provided at the bottom of the chamber, which is not the case for the apparatus according to the German publication specification. The pressurized water promotes the main flow of the liquid while releasing air bubbles that rise up to the surface under good conditions of contact with the material to be separated.

Because the flotation and separation chamber of the apparatus of the invention is disposed along the outer circumference of the coagulation chamber and the fluid flow in the flotation and separation chamber is provided as a one-way peripheral flow, it is possible to make the flow path traveled sufficiently long to achieve whether it is a device with large or small processing capacity.

In the following, an embodiment of the invention will be described in connection with the drawing, in which: 1 shows a flow chart of the traditional treatment apparatus for treating oil-contaminated wastewater; and FIG. 2-5 is an embodiment of the present invention, namely: FIG. 2 is a plan view of the apparatus according to the invention; FIG. 3 is a vertical section along line III-III of FIG. 2; FIG. 4 is a vertical sectional view taken along line IV-IV of FIG. 2, and FIG. 5 is a vertical sectional view taken along the line V-V in FIG. 2nd

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The waste liquid cleaning apparatus of the invention comprises substantially a cylindrical tank 30 having a funnel-shaped bottom. The interior of the tank 30 is divided into a central coagulation chamber 31 and an annular flotation separation chamber 32 surrounding the central coagulation chamber with a cylindrical partition 33 located in the tank concentrically relative to its axis.

In the coagulation chamber 31, a small diameter cylinder T1 and a large diameter cylinder T2 are arranged concentrically with the axis of the tank, open at both ends in such a way that the open upper end of the small diameter cylinder Ti is placed in a lower height than the upper end of the large diameter cylinder T2, so that flow channels are formed in 31a, 31b, 31c in the coagulation chamber through which the waste liquid gradually flows outward from the central portion of the coagulation chamber. An annular element T3 having a l-shaped cross-section is connected to the upper part of the inner wall of the coagulation chamber 31 to form a water collection trough 34.

A tube 35 extends into the tank through the bottom wall of the tank with its inner open end 35a protruding upwardly inside the coagulation chamber 31 from the bottom of the small diameter cylinder T1 for supply to this coagulation chamber of the waste liquid which has been subjected to the primary treatment. A coagulant supply tube 36 and an alkali supply tube 37 are connected to the waste fluid supply tube 35, and a discharge tube 38 is connected to the bottom of the coagulation chamber 30 to discharge a precipitate from this coagulation chamber.

The flotation and separation chamber 32 is divided by radial partitions Si, S2, S3 and S4 into four sub-chambers, namely a liner insertion chamber 32a, a pressurized water injection chamber 32b, a flotation separation chamber 32c, and a liner collection chamber 32d.

As shown in FIG. 4, the upper ends of the partitions S2 and S4 are made lower than the upper ends of the partitions Si and S3.

An auxiliary coagulant supply tube 39 has one end thereof connected to the bottom of the water collection trough 34 and its other end connected to the lower portion of the liner insertion chamber 32a, and auxiliary coagulant feed line 40 leads from an auxiliary coagulant storage tank not shown and connected to an intermediate point. on pipe 39. A pipe 41 to 143268 9 supplies of pressurized water, i.e. Pressurized water containing air is connected at one end to a pressurized water tank which is not shown and its other end is forked and extended into the pressurized water injection chamber 32b. The forked ends of the pressurized water supply tube 41 disposed within the pressurized water injection chamber 32b are both provided with a straight nozzle 41a for controlling the pressurized jet stream discharge from the respective nozzles downwardly so as to abut each other.

The flotation chamber 32c forms a relatively long channel extending around a greater portion of the circumference of the coagulation chamber 31. By placing the flotation separation chamber 32 along the outer circumference of the coagulation chamber 31, it is possible to provide a relatively long flow passage in which the flow of liquid takes place. as a one-way flow (a peripheral flow).

A discharge pipe 42 for the treated purified drainage water is placed in the rear portion of the passage (in the flotation chamber 32c) so that fluke that has been separated does not again mix with the drainage water, which would result in a reduction of the treatment water. efficiency. The discharge tube 42 may in particular have its orifice disposed at the bottom of the chamber in the rear portion of the flotation chamber 32c.

A lint discharge tube 43 is provided in the lower portion of the lent collection chamber 32d which is disposed next to the flotation chamber 32c.

The apparatus of the present invention, as described above, operates in the following manner: First, to the coagulation chamber 31, through the feed tube 35, a wastewater which has previously been subjected to a primary treatment in oil-water separator is supplied. Through the tube 36, 37, a coagulant, e.g. a sludge of alum cake, and an alkali such as a sludge of slaked lime. In the coagulation chamber 31, aluminum hydroxide flakes are formed according to the above reaction formula.

Therefore, the small amount of oil contained in the liquid is adsorbed on the flies during passage of the liquid in the direction indicated by the arrows through channels 31a, 31b and 31c. In this case, the precipitates are discharged from the discharge tube 38. The wastewater thus exposed to the coagulation treatment flows into the water collection trough 34 from a number of notches T3a made in the trough and thence into the liner entrance chamber 32a. During this period, the waste liquid is mixed with the auxiliary coagulant supplied from the auxiliary coagulant supply line 40 through the tube 39. It is recommended to use a mixer, e.g. an injection or injection-type mixer, at the connection between the conduit 40 and the tube 39 to produce a uniform and rapid mixing of the coagulant with the waste liquid. The aluminum hydroxide flakes entering the lint inlet shame a 32a, gather in larger masses and flow into the adjacent pressurized water injection chamber 32b over the upper end of the partition S2. In the pressurized water injection chamber 32b, the flakes are brought into uniform and close contact with the pressurized water discharged from the straight nozzles 41a obliquely downwards in such a manner that they abut each other. The flakes on which the oil is adsorbed and which, due to the action of the coagulant, form large agglomerates, flow into the flotation chamber 32c below the partition S3. During the passage inside the flotation chamber 32c in the one with the arrows in FIG. 2, the flies abut and are connected to fine air bubbles created by the pressurized water and float on the surface of the water.

The liquid float is then moved into the float collection chamber 32d over the upper end of the partition S4, which is located at the outlet end of the flotation chamber 32c and serves as an overflow threshold, thereby being separated from the purified waste liquid.

The purified wastewater is discharged through the discharge pipe 42, while the oil-carrying lids are discharged through the leach discharge pipe 43.

The invention is not only applicable to the treatment of oil-contaminated wastewater as described herein, but also to the treatment of wastewater from pulp plants or wastewater containing suspended materials.