CZ230591A3 - process for treating contaminated water and a plant for making the same - Google Patents

Abstract

Preferred water to which the flocculating agent has been added is preferred an inorganic metal salt is allowed to flow down into the coagulation zone where it is mixed with the polyelectrolyte mixture water saturated with gas microbubbles by volume from 1: 1 to 1: 2.5 based on said mixture; in the fining zone for this mixture containing flocculated particles, countercurrently guided water, saturated gas microbubbles, in an amount of 0.1 m3 to 0.3 m3, based on 1 m 3 of water to be cleaned, thereby separating the sludge from purified water. The device consists of a flocculation unit (12), coagulation units (2) and fining units (1) v concentric ring-like arrangement, with coagulation a mixing and supply disc (4) for is provided to the unit (2) introduction of polyelectrolyte and water saturated with microbubbles in the fining unit (1) in its lower third tubular conduit (3) saturated with microbubbles a water collector is provided around the top of the fining unit (1) (5) a sludge connected to the sludge drain line (11), and an annularly arranged device consisting of flocculation units (12), coagulation units (2) and fining units (1), it is supplemented with an absorption column (15) containing optionally a cartridge (16) for absorbing gas into the water.

Description

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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to methods and apparatus for carrying out such processes.

The treatment of industrial and municipal waste water is carried out by physical, chemical and biological methods or combinations thereof.

BACKGROUND OF THE INVENTION

Metal salts such as ferric chloride, ferrous sulfate, or aluminum sulfate are often used for cleaning and flocculation to form fluffy precipitates with contaminants at a given pH range upon dissolution of said salts in contaminated water. This bulky precipitate is capable of adsorbing other pollutants.

However, the sedimentation rate of the colloidal precipitate is considerably, slow. Therefore, it is preferable to add polyelectrolytes to reduce settling time.

As polyelectrolytes, polyacrylamide, polyacrylic acid and the like can be used. These polymers deposit on solid particles, thereby promoting their sedimentation.

Hungarian Patent Specification No. 169,886 discloses a wastewater treatment process in which precipitating chemicals are added to the wastewater in a single scab at the same time as the gas is introduced for better mixing.

Hungarian patent specification No. 178,617 discloses a wastewater treatment process using a device consisting of a flocculation unit equipped with a paddle stirrer and a row of sequentially connected aeration units. This device serves to separate the resulting sludge.

2. SUMMARY OF THE INVENTION

The purpose of the invention was to develop a new method and apparatus for the purification of waste water in which fine colloidal impurities would be removed more efficiently and faster than in the known methods.

According to the method of the invention, the direct introduction of gas into the supernatant to promote flocculation is replaced by prior saturation of the water to be cleaned with air microbubbles, and the flocculating polyelectrolyte is introduced together with the water-saturated air microbubbles. In this way, the separation of the precipitated impurities in the area of precipitation with loosening microbubbles is promoted.

In addition, the coagulation, flocculation and clarifying units are not separate, connected units; instead, it is modified. a single three-piece device from concentrically mounted units. The flocculating agent is introduced into the innermost flocculation unit where coagulation occurs. Water containing polyelectrolyte and saturated with microbubbles of air is fed to the secondary central unit of the annular cross-section, while the external fining unit serves to separate the coagulated sludge from the purified water, which still contains a small proportion of water with microbubbles.

The water is saturated with gas microbubbles, preferably in a packed absorption column at a pressure of about 0.5 to about 0.5 MPa.

In particular, the invention relates to a process for the purification of contaminated waste water, comprising admixing a flocculating agent and a polyelectrolyte, introducing a gas and subsequently separating the coagulated sludge from the purified water.

The process according to the invention consists in admixing a flocculating agent, preferably an inorganic metal salt, to the water to be purified, whereupon the mixture is allowed to flow down into the coagulation zone. where it is mixed with water saturated with microbubbles and containing polyelectrolyte in a volume ratio of saturated water to polyelectrolyte in the range of 1: 1 to 2.5: 1, and then the sludge-containing mixture is separated from the treated water by countercurrent admixture of saturated water microbubbles, in an amount from 0.1

3 to 0.3 m, based on 1 m of the composition to be cleaned.

The water is gas-saturated preferably in an absorption zone-column filled with Raschig rings at a pressure ranging from 0.5 to about 6 bar.

The invention also relates to an apparatus for carrying out the method of the invention comprising a flocculation, coagulation and clarification unit.

The device according to the invention consists of an aggregate consisting of a flocculation, coagulation and clarification unit in a concentric annular arrangement with a feed disc in a coagulation unit for supplying saturated water microbubbles with an added electrolyte, passing micro-bubbles of saturated water in the lower third of the clarifying unit. the upper part of the fining unit and its outflow, with an absorbent, preferably packed, gas absorbing column coupled to the aggregate, from the flocculation, coagulation and fining units, in a concentric annular configuration.

In the individual parts of the aggregate, i.e. in the flocculation unit, in the coagulation unit and in the fining unit, the flow directions of liquids, solids and gas microbubbles are important.

In the flocculation unit, where the flocculation agent is mixed with the water to be cleaned, the mixture flows downwards and then enters the coagulation unit, at the bottom. encounters polyelectrolyte and microbubbles saturated with water, where the action of uni. flowing microbubbles, the stream of the mixture turns upward. This stream then passes to the fining unit, where the microbubbles saturated with water are supplied at the bottom, where the coagulated mixture flows through the mountain.

After separation of the sludge, this slurry leaves the fining unit, while the purified water is recovered from the bottom.

The apparatus according to the invention is shown in Fig. I. The apparatus comprises a contaminated water storage tank 13, a flocculating agent container 22, a coagulating agent container 23, and a cleaning unit of concentrically annular units with an attached absorption column 15 filled with packing 16. The cleaning unit consists of coagulation units 2, flocculation units 12 and fining units 1.

The flocculation unit 12 is equipped with a mixing and supply disc 4. The fining unit 1 has a tubing 3 for the supply of microbubble saturated water, a control valve 20, a sludge collector 5, a level regulator 8 and a drain channel 10 for purified water.

A level indicator 17, a pressure gauge 18 and a compressor 14 are connected to the absorption column 15.

A water saturated with gas bubbles is injected into the mixing and supply disc 4 with the pump 19.

The device according to the invention functions as follows:

The defect to be cleaned is supplied from the supply tank 13 by the pump 24 and the supply line 6 to the flocculation unit 12, where it flows downwards and enters the coagulation unit 2, where the flow direction of the mixture reverses upwards.

The flocculating agent is fed from the reservoir 22 through a nozzle (nozzle) provided on the inlet pipe to the flocculation unit 12 into the water to be cleaned, whereby the pollutants flocculate and entrain the colloidal particles absorbed from the water onto the surface of the precipitate.

The polyelectrolyte is fed from the reservoir 23 to the bottom of the coagulation unit 2 via a mixing and supply disc 4 to complete coagulation by neutralizing the electrical charge of the colloidal particles.

The mixing and supply disc 4 achieves a homogeneous mixing of the purification water supplied from the reservoir 13 with the electrolyte supplied from the reservoir 23. The polyelectrolyte, under a pressure of 0.5 to 0.6 MPa, is mixed with the water saturated with gas microbubbles before being introduced. 4. The gas-saturated water is supplied in a controlled amount from the absorption column 15 via the control valve 21. The mixture exits from the mixing and supply disc 4 through the openings into the coagulation unit 2, whereby the released gas bubbles cause complete and rapid homogenization. polyelectrolyte (from reservoir 23) without disturbing the flocculation formed in the flocculation unit 12 by the flocculation agent supplied from the reservoir 22. Reaction of the coagulating agent with colloidal

-Particles of pollutants last no more than a few radiant cunt.

The type of reagents in reservoirs 22 and 23 depends on the quality of the water to be cleaned from the reservoir 13. The amount of flocculant to be added is determined by preliminary laboratory experiments.

The microbubbles in the coagulation unit 2 cause the coagulated particles to flow upwardly after admixing the polyelectrolyte from the reservoir 23 by carrying contaminants of higher density and thereby preventing sedimentation thereof. The water carrying the coagulated particles flows over the coagulation edge of the unit 2 in its upper part into the fining unit K

The fining unit 1 is surrounded by a conduit 3 for supplying water saturated with gas microbubbles to which gas-saturated water comes from the absorption column 15 via a control valve 20, which then flows into the fining unit 1 through openings in the housing of the unit under the conduit 3.

In the fining unit, bubbles escape from the gas-saturated water and escape the coagulated particles of pollutants when they escape.

Flooded pollutant particles are entrained by microbubbles as sludge into the sludge collector 5 connected to the upper part of the fining unit 1.

The sludge withdrawal can be controlled by a level regulator 8 provided on the drain channel 10 for discharging purified water from the plant. The water level controller 8 can be used to adjust the water content of the withdrawn sludge as desired, thereby avoiding the costly dehydration of the sludge later.

The purified water leaves the clarifying unit 11 through the vertical discharge channel 10 and the discharge tube 9.

The sludge is discharged from the clarification unit through the sludge outlet 11.

Water saturated with gas is obtained by dissolving the gas in water in the absorption column 15 under pressure. It is transported under pressure, preferably at an operating pressure of 0.5 to 0.6 MPa, by means of a compressor 14.

Purified water obtained from the scrubbing unit 1 is pumped by pump 19 against working pressure to the head of the absorption column 15. At the top of the absorption column 15, the contact surface between water and gas is increased by the charge 16. Upon flowing, the water reaches the maximum degree of gas saturation.

The use of purified water from the clarification unit 1 suitably avoids the use of water from any external source.

The cleaning process according to the invention begins with a full flocculation unit 12, a coagulation unit 2 and a clarification unit consisting of clean or purified water.

By opening the control valves 20 and 41, the gas is admitted to the carbonated water. When microbubbles appear in the clarification unit at the water level, the pump 24 is operated simultaneously with the flow meters. directed to the advised chemical flow rates, arranged on the reservoirs 22 and 23 for the respective chemicals.

The operation of the device according to the invention can be automated by simple means, whereby the operation of the device according to the invention can be run continuously without the need for operator.

The residence time of the water to be purified is generally 15 to 25 minutes, depending on the characteristics of the contaminated water.

The method and apparatus of the invention have the following advantages:

a) The method is simple and easy to automate. In automatic operation, you only need to take care of replenishing chemicals and sludge removal.

b) The process according to the invention is economical in terms of energy, materials and costs.

c) The water content of the sludge obtained by the process according to the invention can be controlled, possibly to such a low value that no further treatment of the sludge is required to dehydrate it. If the removed impurities are flammable, they can be burned directly.

d) The device according to the invention is small in size. It is easy to install and easily transport to any location. This is particularly advantageous in densely populated industrial areas.

e) The design and small dimensions of the device allow the installation of a medium capacity mobile unit.

f) The device according to the invention requires very low investment and operating costs, reaching only 10 to 15% of the costs of the corresponding conventional device of the same capacity,

g) With careful operation of the device, it allows the purified water to be discharged directly into the streams without any harmful consequences.

h) The side-by-side connection of several devices according to the invention allows practically unlimited hydraulic loads. By using in cascade operation any desired quality of purified water can be achieved.

The use of the method and apparatus of the invention is not limited to the areas described herein.

The use of the addition of water with microbubbles makes it possible to improve living streams, such as streams and rivers, by enriching with dissolved oxygen.

With the method and apparatus of the present invention, the drinking water obtained from the underground layers, the dissolved gases and the contained iron, manganese, arsenic, heavy metals and even bacteria can be freed.

The method and apparatus of the present invention can be incorporated into any process line of an industrial plant using process water (e.g., paper mills). In this way, water can be recycled and waste water treatment associated with other costs (such as sludge handling) avoided.

The use of the device according to the invention significantly reduces the amount of hazardous waste recovered at conventional cleaning stations. The usable sludge (without drhydration) can be directly obtained.

The method and apparatus of the invention are preferably applicable to continuous automatic water purification in public baths and swimming pools.

The device according to the invention, connected to the biological wastewater treatment stations, guarantees a considerable cost reduction and offers other advantageous possibilities, such as de-phosphatization

The method of the invention is explained in more detail below with reference to the accompanying drawing.

DETAILED DESCRIPTION OF THE INVENTION

Example 1 - Treatment of waste water from a poultry processing plant

Wastewater has the following characteristics:

- solids content: 500 mg.l '^

- fat and protein content: 600 mg.1 ^

chemical oxygen demand (COD): 2500 mg.I ^-1 (chromate method) m of waste water is introduced into the plant according to the invention shown in Fig. 1.

Ve. flocculating the unit using aluminum sulfate as the flocculating agent. The gas-saturated water in the coagulation unit is mixed with polyacrylic acid as an anionic polyelectrolyte.

Amount of chemicals added:

Aluminum sulphate 0.2 kg Polyacrylic acid 0.002 kg Water saturation air 0.1 Ιδη (at 0.5 MPa pressure) Gas saturated water for addition of polyelectrolyte 0.05 m to the clarification unit 0.20 m?

electrical power (380/220 V, 50 Hz) 0.6 kW

Characteristics of purified water obtained by the process according to the invention:

solids content 5 mg.l * ^ fat and protein content 8 mg.l ^- ^ chemical oxygen demand (COD) 70 mg.l “^

Example 2 (comparative) waste water having the same properties as in Example 1 is purified according to the methods described in Hungarian Patent Specifications 169,886 and 178,617. In both of these methods, flocculation is aided by direct air introduction. The types and amounts of chemicals are the same as in Example 1.

A comparison of the results obtained using these methods with those of Example 1 obtained by the method of the invention is shown in Table 1:

Table 1 Properties Process according to the invention The method according to Hungarian. No. 189.886 Method according to the Hungarians. No. 178.617 Time for introducing chemicals 0.2 min. 10 min. 5 min. Coagulation rate 99% 50% 60% Average residence time of wastewater in the installation 25 min. 1.5 h. 2 h Solids content after purification 5 mg. I “ ¹ 20 mg. AND*"! 15 mg.l ' ¹ Chemical Oxygen Demand (COD) 70 mg.l ' ¹ 200 mg.l ' ¹ 120 mg.l ' ¹

The results of the comparative example show that the process according to the invention provides more efficient flocculation and coagulation with a considerably shorter residence time in the plant and also pollutants are separated from the water to a greater extent.

Industrial applicability

The method and apparatus according to the invention can be successfully used for the treatment of polluted urban and industrial waste water.

Claims (4)

A process for the purification of polluted water by the addition of a flocculating agent, a polyelectrolyte and a gas followed by separating the coagulated sludge from the purified water, characterized in that the polluted water to which the flocculating agent has been added, preferably an inorganic metal salt as flocculating agent, flow down into the coagulation zone, where it is mixed with a mixture of polyelectrolyte and water saturated with gas microbubbles in a volume ratio of 1 r 1 to 1: 2.5, based on said mixture, and then in the clarifying zone for this mixture containing flocculated particles, it acts in counter-flowing water saturated with microbubbles of gas, in an amount of 0.1 m to 0.3 m, based on 1 nt of water to be treated, thereby separating the sludge from the treated water. 2. A process according to claim 1 wherein the flocculating agent is aluminum sulfate. 3. The process of claim 1 wherein the anionic polymer is used as the polyelectrolyte. Device for carrying out the method according to claim 1, characterized in that it consists of a flocculation unit (12), a coagulation unit (2) and a clarification unit (1) in a concentric annular arrangement, wherein a mixing unit is provided in the coagulation unit (2). and a feed disc (4) for introducing polyelectrolyte and water saturated with gas microbubbles, in the clarification unit (1) in its lower third there is a pipe conduit (3) for feeding microbubbles of saturated water gas, around the upper part of the clarification unit (1) (5) the sludge connected to the sludge discharge pipe (11), and the annular arrangement consisting of a flocculation unit (12), a coagulation unit (2) and a fining unit (1) is supplemented by an absorption column (15) containing optionally a filling (15) for the absorption of gas into water.