RU2336233C2 - Method of biological sewage water purification - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: sewage water is preliminary aerated until degree of saturation with air is not less than 10.2 mg/l. Sorption and oxidation are carried out in biocoenosis of active silt, as such its swollen form is used, mixing sewage water and active silt supplied in countercurrent manner in ascending-descending flow with not less than two-fold cyclic change of pressure onto swollen silt from 0.1 to 0.01 MPa due to forced supply of water-silt mixture from separate sedimentator. Height of purified water layer is not less than 10 m. In sedimentator swollen silt is retained by means of biological film and gravitational sedimentation and purified water is separated in ascending-descending flow.

EFFECT: invention allows to reduce purification cost and improve water purification quality.

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Description

The invention relates to the biological treatment of wastewater.

A known method of biological wastewater treatment, including biological sorption and oxidation in the biocenosis of active, including swollen sludge, by aeration of a mixture of wastewater and activated sludge, separation of purified water and retention of swollen sludge using a biological film and gravity deposition, return separated from the purified water of swollen sludge to the aeration stage for reuse as activated sludge [see A.S. USSR No. 1551660, С02F 3/12, publ. 03/23/1990]. In this case, the separation of purified water and the delay of the swollen sludge are carried out by two or multiple sequential processes of deposition of particles of swollen sludge.

The disadvantages of this method include the fact that although it allows the use of swollen sludge with a high oxidizing ability and formed during wastewater treatment, the proportion of swollen sludge in the total proportion of sludge used is small, and the process of maintaining the working capacity of swollen sludge is uncontrolled.

Closest to the proposed method is a biological wastewater treatment, including sorption and oxidation in the biocenosis of activated sludge by aeration of a mixture of wastewater and activated sludge, separation of purified water and delayed swollen sludge by flocculation using a biologically active film and gravity deposition, return of activated sludge to aeration stage [see Russian patent No. 2146231, С02F 3/34, С12N 1/00, 1/20, 13/00, publ. 03/10/2000].

To implement the method requires complex and cumbersome equipment, containing both a sorption and oxidation zone, and a flocculation and deposition zone. In addition, the sorption and oxidation process occurs in a countercurrent fashion, first in a spiral moving upward flow, which ensures complete mixing both in the vertical and horizontal directions. In some cases, with large degrees of water pollution and its large volumes, water purification devices according to this method occupy large urban areas. In addition, these devices, according to sanitary standards, must be distant from residential areas over considerable distances, which increases the required area occupied by water treatment equipment. All these factors lead to a significant increase in the cost of wastewater treatment.

The task of creating this technical solution and its technical result is to reduce the cost of water treatment by reducing the complexity of the equipment used, reducing the required area for water treatment in urban areas while improving the quality of water treatment.

The specified technical result is achieved by the fact that in the method of biological wastewater treatment, including sorption and oxidation in the biocenosis of activated sludge, which use its "swollen" form, the separation of purified water and the delay of swollen sludge by flocculation using a biological film and gravitational deposition , the return of the swollen sludge to the aeration stage in a turbulent mode, there are differences, namely, preliminary aeration of the wastewater is carried out to a degree of saturation with air oxygen of at least 10.2 ml / l, sorption pollution in the biocenosis of swollen sludge is carried out by mixing wastewater and swollen sludge supplied in a counter-current flow in an upward-downward flow with at least two cyclic changes in the pressure on the swollen sludge from 0.1 to 0.01 MPa, which is achieved at a layer height the treated water is not less than 10 m, and the delay of swollen sludge and the separation of purified water are carried out in a separate device - a sedimentator in a downward-upward flow of moving water.

The proposed method allows to reduce the cost of wastewater treatment due to the reduction in the area occupied by treatment equipment through the use of a high-altitude scheme of the wastewater treatment complex, including bioreactors and sedimentators, and to reduce the complexity of the equipment used. The method simultaneously allows to improve the quality of water treatment.

The aeration of wastewater and activated sludge with a cyclic pressure change of at least twice from 0.1 to 0.01 MPa during its processing allows to more effectively maintain the sorption and oxidation ability of swollen sludge, which has better oxidizing properties under extreme conditions, which in combination with used flat modules with loading, coated with a biological film in the sedimentator, increases the efficiency of water purification.

The method is as follows.

When starting the bioreactor, the biocenosis of the swollen sludge is formed.

Wastewater freed from rough mechanical impurities is supplied to the bioreactor, here it is pre-aerated to a possible limit of its saturation with air oxygen of at least 10.2 mg / l.

The height of the layer of purified water in the bioreactor should not be less than 10 m. At the initial stage of the bioreactor start-up, sorption and oxidation of contaminants in the biocenosis of activated sludge occur, as a result of which the particles of swollen sludge lose their oxidizing and sorption ability. A mixture of purified water and spent swollen sludge is removed from the bioreactor and fed into a separate device - a sedimentator, containing several layers of biological film fixed on flat modules in a downward-upward flow. Under the influence of opposite charges of the biofilm and spent swollen sludge, contact and the formation of flocculi occur, which, under the influence of their own weight, are deposited in the lower part of the sedimentation device.

When fresh portions of treated wastewater are supplied to the bioreactor, swollen sludge taken from the sedimentator in a predetermined concentration (0.2-0.3 mg / l) selected from the sedimentator is also fed into it in a countercurrent scheme. During the pumping process, the floccules of the swollen sludge are destroyed as a result of the turbulent flow regime, and the swollen sludge acquires its original flocculent shape, while the growth of other microorganisms that are not involved in the oxidation and sorption is suppressed.

A mixture of swollen sludge and purified water is fed into the lower part of the bioreactor and mixed with the waste water supplied to the upper part of the bioreactor. Further, the swollen sludge rises to the upper part of the bioreactor in the ascending branch of the stream and then falls back to its lower part, while the pressure acting on the particles of the biocenosis of the swollen sludge is applied from 0.1 MPa in the lower part of the bioreactor to 0.01 MPa in the upper and again rises to 0.1 MPa in the lower. The number of cycles of pressure change, under the influence of which there are particles of the biocenosis, must be from two or more. This ensures the restoration of the sorption and oxidative ability of the biocenosis of swollen sludge, i.e. its regeneration. These changes in pressure can be achieved with a layer height of treated wastewater of at least 10 m. After the sedimentator, if necessary, clarified water can be disinfected and then discharged. Part of the mixture of swollen sludge with water is returned from the sedimentator to the aeration stage.

Example 1

For wastewater treatment in an amount of 300 m ³ / day, a high-altitude scheme of bioreactors and sedimentators with a total height of 10.5 meters is used. The amount of contaminants in the wastewater supplied to the wastewater treatment plant according to BOD ₂ o (biological oxygen demand in a twenty-day sample) is 314 mg / l. Before being fed to the receiving tank, the water to be purified passes through a mechanical cleaning process. The first stage of wastewater treatment consists in its saturation with atmospheric oxygen up to 10.2 mg / l, then a sludge mixture with a sludge concentration of 0.2 g / l is forcibly supplied from the sedimentators to the bioreactor in an ascending-descending flow, which allows changing the pressure to working active sludge in the range from 0.1 MPa to 0.01 MPa. This process is carried out twice. At the same time, the dose of working sludge in the aeration tank is 0.9 g / l. After passing the specified cycles of pressure change on the treated activated sludge, the treated wastewater with activated sludge enters the sedimentator to separate them, while the sludge mixture moves in a sedimentator in a downward-upward flow through the layers of the biological film fixed on flat modules. Swollen sludge and a biological film, having opposite charges, form floccules from the mobile medium of activated sludge, which, increasing in size, become heavier than the water being purified and settle into the conical part of the sedimentator. Since the deposition process is ongoing, the delayed activated sludge is pumped into the bioreactor in the same way. The transfer of swollen sludge is carried out in a turbulent mode, so the sludge flocculi are destroyed, acquiring the original flocculent form, which is necessary for the sorption of contaminants in the bioreactor. The clarified water from the sedimenter sent for further processing, while the delayed yl periodically removed, the degree of water purification will be the BOD ₅ - 30 mg / l. Part of the mixture of swollen sludge with water is returned from the sedimentator to the aeration stage.

In examples 2-4, the method is carried out similarly to that described in example 1, but the value of the parameters are excellent and are shown in the table, illustrate the effect on the degree of water purification.

No. Ref. overseas BOD ₂₀ , mg / l The height of the layer of purified water, m The number of cycles in the bioreactor The number of cycles in the sedimentator Daily load, m ³ / m ² Saturation with air oxygen, mg / l The frequency of unloading of sludge, days The degree of purification according to BOD ₂₀ , mg / l one 2 3 four 5 6 7 8 10 one 314 10 2 one four 10,2 10 thirty 2 314 12 2 2 8 10.7 fifteen twenty 3 314 fifteen 3 3 12 11.1 22 8 four 314 eighteen four four 16 12,4 thirty 3

The proposed method allows to reduce the cost of water purification in comparison with the prototype by 1.5-2 times by reducing the area occupied by treatment plants, by 3-4 times, simplifying the equipment used, and also to improve the degree of water purification.

Claims (1)

A method of biological treatment of wastewater during aeration, including sorption and oxidation in the biocenosis of activated sludge, which uses its swollen form, while mixing wastewater and swollen sludge supplied in a countercurrent scheme, separating purified water and delaying the swollen sludge by flocculation with using biological film and gravitational deposition, the return of swollen sludge to the aeration stage in a turbulent mode, characterized in that the preliminary aeration of wastewater to the degree of oxygen saturation air not less than 10.2 mg / l, sorption and oxidation are carried out in an upward - downward flow with at least a twofold cyclic change in pressure on the swollen sludge from 0.1 to 0.01 MPa, which is achieved when the layer height of the treated water is at least 10 m due to the forced supply of the water mixture from a separate sedimentator, in which the delayed swollen sludge and the separation of purified water in a downward-upward flow.